Download Investigation of threats to the Christmas Island Pipistrelle.

INVESTIGATION OF THREATS TO THE
CHRISTMAS ISLAND PIPISTRELLE
A Report to the Department of the Environment
and Water Resources
Prepared by:
Lindy Lumsden, Martin Schulz, Raquel Ashton and David Middleton
Arthur Rylah Institute for Environmental Research
Department of Sustainability and Environment
123 Brown Street, Heidelberg VIC 3084
March 2007
Arthur Rylah
Institute
Flora, Fauna &
Freshwater Research
Title:
Investigation of threats to the Christmas Island Pipistrelle.
Produced by:
Arthur Rylah Institute for Environmental Research,
Department of Sustainability and Environment,
123 Brown Street,
Heidelberg, Victoria,
Australia 3084
ABN 9071905 2204
Date:
March 2007
This document may be cited as:
Lumsden, L., Schulz, M., Ashton, R. and Middleton, D. (2007). Investigation of threats to the
Christmas Island Pipistrelle. A report to the Department of the Environment and Water
Resources. Arthur Rylah Institute for Environmental Research, Department of Sustainability
and Environment, Heidelberg, Victoria.
Cover photo: The Christmas Island Pipistrelle Pipistrellus murrayi (Lindy Lumsden)
Copyright © Department of Sustainability and Environment, Victoria
General disclaimer
This publication may be of assistance to you but the State of Victoria and its employees do not
guarantee that the publication is without flaw of any kind or is wholly appropriate for your
particular purposes and therefore disclaims all liability for any error, loss or other consequence
which may arise from you relying on any information in this publication.
2
Table of Contents
Table of Contents ........................................................................................................................2
List of Tables................................................................................................................................5
List of Figures ..............................................................................................................................5
List of Plates.................................................................................................................................5
Acknowledgments........................................................................................................................7
Executive summary .....................................................................................................................8
The decline of the Christmas Island Pipistrelle.........................................................................8
Wet season 2005/06 study and new perspectives on the causes of decline ..............................8
The future ................................................................................................................................10
Introduction ...............................................................................................................................11
Methods ......................................................................................................................................14
Duration and timing of study ..................................................................................................14
Detector sampling ...................................................................................................................14
Trapping ..................................................................................................................................14
Collection of biological samples to assess health status .........................................................16
Location of roost sites .............................................................................................................18
Observations of roost trees using infra-red cameras ...............................................................20
Observations on other species .................................................................................................22
Results ........................................................................................................................................23
Detector sampling ...................................................................................................................23
Number of individuals caught .................................................................................................23
Disease investigation...............................................................................................................26
Roost sites ...............................................................................................................................27
Availability and longevity of maternity roosts........................................................................34
Colony size and roosting behaviour ........................................................................................39
Emergence times and investigation of daytime flight.............................................................40
Observations of roost trees using infra-red cameras ...............................................................42
Nankeen Kestrel observations.................................................................................................44
Feral Cat sightings...................................................................................................................46
Common Wolf Snake observations.........................................................................................47
Other observations...................................................................................................................48
Discussion...................................................................................................................................50
Key findings of the study ........................................................................................................50
Clarification of current distribution.....................................................................................50
Estimation of the size of the remaining population.............................................................50
Confirmation of breeding status..........................................................................................51
Location of maternity roosts ...............................................................................................51
Identification of further threats ...........................................................................................51
Investigations of potential predators ...................................................................................52
Investigation of disease .......................................................................................................52
Nomination for listing the species as ‘Critically Endangered’ ...........................................53
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Threat analysis.........................................................................................................................53
Predation or disturbance by the Common Wolf Snake Lycodon aulicus capucinus ..........54
Predation and/or disturbance by the Giant Centipede Scolopendra morsitans...................55
Predation and/or disturbance by the Yellow Crazy Ant Anoplolepis gracilipes.................57
Predation by the Nankeen Kestrel Falco cenchroides ........................................................58
Predation by the introduced Black Rat Rattus rattus ..........................................................59
Predation by the Feral Cat Felis catus ................................................................................59
Predation by endemic predators ..........................................................................................60
Disturbance to roost sites from Giant African Snails Achatina fulica ................................60
Habitat loss..........................................................................................................................61
Habitat alteration .................................................................................................................61
Loss of roost sites................................................................................................................61
Prey availability...................................................................................................................62
Climatic conditions .............................................................................................................63
Vehicle-related mortality.....................................................................................................63
Disease ................................................................................................................................63
Decreasing population size..................................................................................................64
Options for future management...............................................................................................64
Captive breeding .................................................................................................................64
On-ground roost management .............................................................................................66
Predator control ...................................................................................................................67
Further investigations to determine cause of decline ..........................................................70
References ..................................................................................................................................73
Appendices .................................................................................................................................77
Appendix 1. Sites sampled using bat detectors and the number of Christmas Island
Pipistrelle calls recorded....................................................................................................77
Appendix 2. The biological samples collected from the trapped Christmas Island
Pipistrelles. ........................................................................................................................79
Appendix 3. Blood count parameters from blood smears collected from 31 Christmas
Island Pipistrelles...............................................................................................................81
Appendix 4. The blood parameters of Little Forest Bat Vespadelus vulturnus, Southern
Forest Bat V. regulus and Large Forest Bat V. darlingtoni, from Healesville,
Victoria. .............................................................................................................................83
Appendix 5. The fate of the Christmas Island Pipistrelle roost trees located in 1998
during the Lumsden et al. (1999) study.............................................................................84
Appendix 6. Prey items identified from remains found at Nankeen Kestrel feeding
sites. ...................................................................................................................................85
4
List of Tables
Table 1. The number of individuals caught, their reproductive condition, forearm length
and weight. Retrapped individuals have been excluded. ............................................26
Table 2. Characteristics of roost trees used by the radiotracked Christmas Island
Pipistrelles in December 2005. ....................................................................................29
Table 3. The number of individuals recorded exiting maternity roosts and the maximum
number of individuals represented by these counts. ....................................................40
Table 4. The prey items identified from feeding remains of Nankeen Kestrels,
predominantly in the west of the island at Fields 25 and 26. ......................................45
List of Figures
Fig. 1. The trend of decline in the Christmas Island Pipistrelle from 1994 to 2005. .................11
Fig. 2. The locations sampled using bat detectors with an indication of the number of
calls of the Christmas Island Pipistrelle that were recorded. .........................................24
Fig. 3. The locations trapped for the Christmas Island Pipistrelle using harp traps,
showing the sites where bats were caught......................................................................25
Fig. 4. The location of roost sites of Christmas Island Pipistrelles found in December
2005. ...............................................................................................................................30
Fig. 5. Emergence times of Christmas Island Pipistrelles from maternity roosts in
December 2005 (n = 365 observations). ........................................................................41
Fig. 6. Feral Cats sighted during field work on Christmas Island in December 2005. ..............46
Fig. 7. Common Wolf Snake observations in the west and south of the island.........................48
Fig. 8. The distribution of the Giant Centipede in 2004 recorded during reptile surveys
undertaken by the Christmas Island Biodiversity Monitoring Programme....................56
Fig. 9. The distribution of the Giant African Snail Achatina fulica in 2005, based on island
wide surveys (map courtesy of PANCI). ……………………………………...……… 60
List of Plates
Plate 1. An ultrasonic bat detector set in place within a waterproof housing. ...........................15
Plate 2. Trapping site along the recently bulldozed lines through secondary regrowth just
west of the start of the Winifred Beach Track. .............................................................15
Plate 3. Harp trap set at the eastern end of the Circuit Track along the edge of a new
rehabilitation area..........................................................................................................16
Plate 4. Individual recognition was achieved by fur clipping. ...................................................17
Plate 5. A radio transmitter fitted to a Christmas Island Pipistrelle...........................................19
Plate 6. Transmitter signals were searched for from sea as well as land. ..................................20
Plate 7. A Faunatech Digicam Surveillance Infra-red Camera set up on tripod with
movement sensors attached to the tree to detect the movement of animals up and
down the tree.................................................................................................................21
Plate 8. Loose bark lifting off a dead Tristiropsis acutangula used as a maternity roost by
a colony of 32 Christmas Island Pipistrelles (Roost 14)...............................................31
Plate 9. Maternity roost under bark on a dead Tristiropsis acutangula tree where there
was no loose bark below the roost site (Roost 14)........................................................31
Plate 10. Peeling bark on a dead Tristiropsis acutangula used as a maternity roost by a
colony of up to 54 pipistrelles (Roost 13) where there was continuous bark for
most of the trunk of the tree.. ......................................................................................32
Plate 11. Roost under lifting bark used by 15 female pipistrelles (Roost 17)............................32
5
Plate 12. Maternity roost in the top of a dead Arenga Palm (Roost 15), used by 48
individuals. ..................................................................................................................33
Plate 13. Suspended dead pandanus fronds used as a roost used by a male pipistrelle. ............33
Plate 14. Roost used by a male pipistrelle in a dead palm frond................................................34
Plate 15. Roost tree 18 when found on 21 December 2005. ......................................................36
Plate 16. Roost tree 18 when found two days later (23 December 2005), after collapsing. ......36
Plate 17. Roost tree 13 falling over on 13 April 2006 as observed on the infra-red camera
set at its base................................................................................................................37
Plate 18. The last remaining piece of loose bark on a dead tree, which was being used as
a maternity roost for a colony of 11 Christmas Island Pipistrelles (Roost 23). ..........38
Plate 19. The remains of a Tristiropsis acutangula tree that was used as a roost site by
Christmas Island Pipistrelles in 1998 (Roost 2)..........................................................39
Plate 20. Observation of a Black Rat climbing a Christmas Island Pipistrelle roost tree ..........43
Plate 21. Observation of a Giant Centipede climbing a Christmas Island Pipistrelle roost
tree...............................................................................................................................43
Plate 22. Nankeen Kestrels were common throughout the disturbed areas of the island. .........44
Plate 23. Nankeen Kestrel feeding remains comprised predominantly of the large
grasshopper Volanga irregularis.................................................................................45
Plate 24. Feral Cats appeared to have increased in abundance since 1998................................46
Plate 25. Common Wolf Snakes were commonly observed on the road and in disturbed
areas in the west of the island. ....................................................................................47
Plate 26. Giant Centipedes were abundant throughout all areas of the island in 2005. .............49
Plate 27. Giant African Snails were also abundant throughout parts of the forest. ...................49
Plate 28. A photograph from Venezuela of a giant centipede, Scolopendra gigantea,
holding and eating a freshly-killed Leaf-chinned Bat, Mormoops megalophylla,
while hanging from the ceiling in a cave ....................................................................57
6
Acknowledgments
We would like to thank the following people who assisted with this project.
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•
•
•
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David James, Parks Australia North, Christmas Island, for all his assistance while we were
on the island, as well as during the preparation phase of this study and subsequent to the
field work, especially with respect to the infra-red cameras, roost watches and detector
monitoring. We would also like to recognise the huge amount of work David has
undertaken in monitoring the Christmas Island Pipistrelle over the past three years –
without his efforts our current knowledge of the species would be much reduced.
Mick Jeffery, Max Orchard and Kent Retallick, Parks Australia North, Christmas Island for
assistance in various ways.
Ross Meggs and Barbara Young, Faunatech Bairnsdale, for all their efforts developing and
constructing the infra-red cameras.
Dr. Philippa McLaren, Gribbles Veterinary Pathology Laboratory, for analysing the blood
smears and for discussions on their interpretation.
Dr Ian Beveridge, Veterinary Department, University of Melbourne, for examining faecal
material for internal parasites.
Dr Chris Tidemann for access to field notebooks from his 1980s studies.
Dr Jesus Molinari for permission to reproduce the photo of the Venezuelan centipede.
David James, Mick Jeffery and Richard Loyn for commenting on an earlier draft of this
report.
Susan Wright, Emma Lowe and Julian Barnard from the Department of Environment and
Heritage (now Department of the Environment and Water Resources) for facilitating
funding and managing the project.
Field work was undertaken under permits from the Australian Government, Department of the
Environment and Heritage to conduct scientific research in Christmas Island National Park, and
the Arthur Rylah Institute Animal Ethics Committee AEC 05/010 and AEC 06/06.
All photographs in this report are by Lindy Lumsden, Martin Schulz or Raquel Ashton, except
where indicated.
7
Executive summary
The decline of the Christmas Island Pipistrelle
The Christmas Island Pipistrelle Pipistrellus murrayi is endemic to Christmas Island, and is the
only species of insectivorous bat on the island. It has declined dramatically in distribution and
abundance in the last 20 years. In the mid-1980s it was common and widespread across the
whole island. It is now predominantly restricted to a small area in the far west of the island,
having disappeared from over 80% of its former range. Long-term monitoring using ultrasonic
bat detectors indicates a decline of 90% in abundance since 1994. Indications suggest that this
species may become extinct within several years. If it does, it will be the only species of
microbat to become extinct in Australia within historical times. Therefore it is critical that
urgent action is taken to halt this decline and commence the recovery of the species.
The cause of this rapid decline is unknown. A number of potential threatening processes have
been identified and this project was initiated to investigate two of the most likely threats:
predation or disturbance at roost sites, and disease. There are a number of introduced species
that may be impacting on the conservation of the Christmas Island Pipistrelle by preying on or
disturbing bats from within their roosts, e.g. Common Wolf Snake Lycodon aulicus capucinus,
Giant Centipede Scolopendra morsitans, Yellow Crazy Ant Anoplolepis gracilipes, Black Rat
Rattus rattus or Feral Cat Felis catus. Predation may be especially critical during the breeding
season when non-flying young are left in the roosts at night while the adult females forage. In
addition, it is possible that a currently unknown health threat has recently been introduced to
the island. Disease is considered the cause of the extinction of the two species of endemic rats
on Christmas Island (Maclear’s Rat Rattus macleari and Bulldog Rat R. nativitatus) at the start
of the 20th century.
Wet season 2005/06 study and new perspectives on the causes of decline
The field component of this study was timed to coincide with the period when females give
birth to their young (December 2005 – early January 2006), so that maternity roosts could be
located, and information could be collected on the breeding patterns of the species. Sampling
using ultrasonic bat detectors and harp traps confirmed the recent patterns found by the
Christmas Island Biodiversity Monitoring Programme that this species is virtually confined to a
small area in the far west of the island. Additionally, a very small number of individuals were
located in the central-west of the island. The size of the total population is not known,
however, 167 individuals were observed emerging from maternity roosts providing a minimum
population size. Based on the number of captures, detector passes, and individuals in maternity
roosts, the total population may be in the order of 500 to 1000 individuals.
Communal maternity roosts, where females give birth to their young, were located for the first
time during this study. Seven maternity roosts were found by radiotracking lactating females
back to their roosts. These maternity roosts were highly specific, with six of the seven located
under exfoliating bark on dead trees. All roosts were in or near gully lines within The Dales
area in the far west of the island. Colony sizes in maternity roosts ranged from 11 to 54
individuals, with some colonies alternating between two adjacent roost trees.
Suitable maternity roost trees may be a limiting resource, either now or in the near future.
Within nine months of locating these roosts (i.e. as of September 2006), four roost trees had
collapsed and another had lost all the loose bark off the tree, resulting in the loss of five of
these seven known maternity roosts. Dead trees occur in low densities, and the bats selected
8
areas of the forest that had higher densities of these preferred roost trees. If the loss of
maternity roost trees continues at this rapid rate, the low availability of suitable roost sites
could become a serious threat to the species.
Fifty-two individuals were trapped and examined for evidence of disease or ill-health in this
study. All appeared in good condition, with high body weights and no obvious external signs
of disease. Seventy-three percent of the individuals were females, of which 82% were in
breeding condition. A range of biological samples were collected: blood; swabs from the
external opening of the respiratory system, urogenital area and wing membrane for viral and
bacteriological testing; faeces to examine for internal parasites; and external parasites. All
samples were normal, with the exception of the white blood cell counts, that were lower than
for other species of closely-related microbats, and possible regenerative anaemia. However,
the significance of these findings are unclear, as it is not known if these parameters are typical
for this species or represent ill-health. While this study found no definite indication of disease
or ill-health in the remaining Christmas Island Pipistrelle population, the number and quantity
of samples that could be collected was limited due to the very small size of these bats (3-4 g).
Therefore, further studies are required before disease can be ruled out as a possible contributing
factor in the decline of the species.
Infra-red cameras with movement sensors were established on maternity roost trees. It had
originally been planned to set these at the entrances to the roost cavities, however, due to the
severely decayed nature of the trees and the looseness of the lifting bark, this was not possible.
Instead, the cameras were set at the base of the trees to capture images of potential predators
climbing up and down roost trees. To date, Black Rats, Giant Centipedes and a Common Wolf
Snake have been observed on roost trees. Black Rats and Giant Centipedes are highly arboreal
and could be accessing roosts. The climbing ability of the Common Wolf Snake is still to be
fully determined. Black Rats are known to have caused the decline of bats on islands
elsewhere in the world. It is not known if Giant Centipedes prey on pipistrelles, however, there
is a recent report from Venezuela of a con-generic species of giant centipede preying on bats
considerably larger than themselves. The abundance of Giant Centipedes on Christmas Island
has increased considerably in recent years, however, the distribution and timing of this increase
does not closely match the pattern of decline of the pipistrelle. The Common Wolf Snake was
introduced in 1987 and has since spread from the Settlement across island, matching both the
timing and pattern of decline of the pipistrelle.
Another species that may be impacting on the conservation of the pipistrelle is the Nankeen
Kestrel Falco cenchroides which first arrived on the island in the 1950s and increased its
distribution and abundance in the 1980s. The kestrel preys on the Glossy Swiftlet Collocalia
esculenta natalis, the diurnal ecological equivalent of the pipistrelle. It may therefore also be
capable of catching pipistrelles in flight, although no evidence of this has been found in kestrel
feeding remains.
It is likely that the recent explosion of the Yellow Crazy Ant supercolonies had direct and
indirect impacts on the pipistrelle. Roosts on the trunks of trees would have been in the direct
path of columns of ants travelling from nests on the ground to the canopy. However, ants are
not considered the main cause of the decline, as the pipistrelle was already in decline before the
ants exploded in numbers, and the stronghold of the pipistrelle is in the west of the island which
is where the majority of the supercolonies formed. However, had the supercolonies not been
controlled, the impact from these would have most likely accelerated the decline of the species,
as would any re-emergence of uncontrolled supercolonies in the future.
9
A wide range of other threats have been proposed, although there is no direct evidence as to
their impact on the decline of the pipistrelle.
The future
Due to the rapid decline of the Christmas Island Pipistrelle and the lack of hard evidence for the
cause of this decline, there is an urgent need for a range of management actions to prevent the
imminent extinction of this species. Management options can be grouped into four approaches:
captive breeding; on-ground roost management; predator control; and further investigations to
determine the cause of the decline so that management actions can be more targeted in the
future. We believe the two highest priorities are to establish a captive breeding program and to
protect and supplement roost sites. These measures alone will not ensure the long-term
survival of the species. However, they will provide some ‘breathing space’ in which to
determine and address the cause of the decline.
We recommend that a captive breeding colony be established at an existing wildlife facility on
the Australian mainland, at a location with a similar climate and day length, such as Darwin.
Alternatively a facility could be built and staffed on the island. However, the advantage of
using an established facility is the existence of experienced staff, such as animal keepers and
veterinarians, and access to pathology services, enclosures and resources. This option would be
more cost-effective and better able to maintain and monitor the health and well-being of the
animals. It would, however, require animals to be transported from Christmas Island to
Darwin, probably necessitating the hire of a plane. A captive colony would provide insurance
against further decline in numbers, and a source of animals to re-establish wild populations
once the cause of the decline had been identified and controlled.
Predation of individuals from within roosts remains a serious potential threat to the survival of
the Christmas Island Pipistrelle. Therefore, it is suggested that preventative barriers are
installed around the bases of all remaining maternity roosts to prevent introduced species from
climbing roost trees. In addition, potential roost trees, i.e. other dead trees with exfoliating
bark, close to maternity roosts should also be protected in this way. The rapid collapse of
maternity roosts and the low densities of these preferred roost trees, may lead to a shortage of
these roosting sites. Therefore it is recommended that artificial roost sites in the form of bat
boxes be established nearby. These should be set on smooth metal poles to prevent introduced
species from accessing the roosts.
Methods for controlling the wide range of introduced species that may be impacting on the
pipistrelle should be investigated, and where possible undertaken throughout The Dales area
encompassing all known roosting sites. It is important that this area is intensively monitored
for Yellow Crazy Ants, so that any new colonies can be located and quickly controlled.
Further investigations are also required into the cause of the decline of the pipistrelle. The
long-term monitoring of the distribution and abundance should be continued to monitor the
status of the remaining population. The current infra-red camera monitoring of the maternity
roosts should be continued and further radiotracking studies conducted to locate additional
roost sites. Experimental studies may be required on captive animals to test for the impact of
potential predators.
Urgent action is required on all proposed management options to avert the imminent extinction
of the Christmas Island Pipistrelle.
10
Introduction
The Christmas Island Pipistrelle Pipistrellus murrayi is endemic to Christmas Island, and is the
only species of insectivorous bat on Christmas Island. It was listed as ‘Endangered’ under the
Environment Protection and Biodiversity Conservation (EPBC) Act 1999 in 2001, and
transferred to ‘Critically Endangered’ under the EPBC Act in September 2006. A Recovery
Plan for this species was adopted in 2004 (Schulz and Lumsden 2004).
The distribution and abundance of this species has changed dramatically in recent years.
Surveys undertaken in the mid-1980s found the species to be widespread and common across
the island (Tidemann 1985). However, studies in the mid-1990s, revealed that a marked
reduction in abundance and a westward range contraction was occurring (Lumsden et al. 1999).
This decline has continued at a rapid rate and the species is now confined to the far west of the
island, no longer occurring across more than 80% of its former range (James 2004). Based on
survey data, there was a 33% decline in abundance between 1994 and 1998 (Lumsden et al.
1999), and a further 55-65% decline between 1998 and 2004, or 10% per year (James 2004).
This decline has continued at a steady rate in 2005 and 2006 (David James, Parks Australia
North Christmas Island [PANCI], pers. comm.) (Fig. 1). The number of individuals remaining
is not known, however, it is considered that the population has reached a critically low number.
There is a real possibility that this species may become extinct in the near future (possibly in a
matter of years) (Fig. 1). If it does, it will be the only species of microbat to become extinct in
Australia within historical times.
120
% of 1994 population
100
80
60
40
20
0
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
Year
Fig. 1. The trend of decline in the Christmas Island Pipistrelle from 1994 to 2005. This
data is based on repeated sampling using ultrasonic bat detectors at fixed stations (taken from
James 2005, with the addition of unpublished data for 2005 and 2006 from David James, Parks
Australia North Christmas Island [PANCI], pers. comm. and the inclusion of data from Corbett
et al. 2003 for sampling undertaken in 2002).
11
The cause of this rapid decline is unknown. A number of potentially threatening processes
were identified in the Recovery Plan (Schulz and Lumsden 2004). However, further work is
required to determine the main cause(s) of the decline in the species to provide direction for
recovery actions.
Predation or disturbance at roost sites is considered one of the most likely threats to the survival
of the species (Schulz and Lumsden 2004). Predation or disturbance may be especially critical
during the breeding season when non-flying young are left in the roosts while the adult females
forage. These young are likely to weigh less than 1 g, and so would be vulnerable to a range of
predators. A number of introduced species may be impacting on the conservation of the
Christmas Island Pipistrelle by either preying on, or disturbing bats while they are within their
roosts, e.g. Common Wolf Snake Lycodon aulicus capucinus, Feral Cat Felis catus, Black Rat
Rattus rattus, Giant Centipede Scolopendra morsitans or Yellow Crazy Ant Anoplolepis
gracilipes.
The Common Wolf Snake was introduced to the island from South-east Asia in 1987 (Smith
1988) and since then has spread across most of the island (James 2005; PANCI unpubl. data).
Lumsden et al. (1999) suggested that the timing of introduction and the distribution of the
snake closely mirrored the decline of the pipistrelle, and considered the snake to be a possible
cause of the decline. Introduced snakes have had devastating impacts on island fauna
elsewhere (see Schulz and Lumsden 2004 for examples). The introduced Black Rat has been
attributed with the extinction of bats on islands elsewhere in the world (e.g. Daniel and
Williams 1984) and introduced rats are considered the primary cause of decline and local
extinction of bat species in New Zealand (Colin O’Donnell, Dept. of Conservation, New
Zealand, pers. comm.). Little is known about the possible impact of centipedes, however,
Giant Centipedes (Scolopendra gigantea) in Venezuela have been recorded preying on bats
larger than the Christmas Island Pipistrelle (Molinari et al. 2005).
The proliferation of the Yellow Crazy Ant in recent years is likely to have had direct and
indirect effects on the pipistrelle. However, the ants are unlikely to be the primary cause of the
current decline, as the decline had already commenced before the Yellow Crazy Ants exploded
in numbers, and the stronghold of the species in the west of the island corresponds broadly with
where the majority of the supercolonies formed.
Another possible factor that may be causing high mortality rates is disease. It is possible that
some specific health threat has arisen in recent years or has recently been introduced to the
island and it has been suggested that this may be the most plausible hypothetical agent of the
decline (James 2005). Whilst there is no direct evidence of transmissible disease in the
population (although this is difficult to determine without targeted studies) there is
circumstantial evidence that it is plausible. Firstly, island species are more prone to suffer from
epizootics than are continental species by virtue of their geographical and spatial confinement.
Secondly, it is believed that disease was the cause of the extinction of the two species of
endemic rats on Christmas Island at the start of the 20th century (Pickering and Norris 1996)
and the contemporaneous decline of the Christmas Island Shrew Crocidura attenuata trichura.
Thirdly, some of the introduced species on Christmas Island, such as the Giant African Snail
Achatina fulica and Black Rat have been implicated in dispersing diseases to oceanic islands
(Alicata 1966; Pickering and Norris 1996). Transmissible disease is considered a major cause
of decline in some other species, such as a range of frog species (chytrid fungus) and the Koala
Phascolarctos cinereus. (chlamydophila). Factors other than infectious agents can also
contribute to species decline through negative impact on health. These include toxic, climatic,
12
traumatic, genetic, parasitic, nutritional, developmental, metabolic and degenerative causes of
disease. These factors are subject to change through time and can impact severely on survival
and productivity.
Other possible threatening processes outlined in the Recovery Plan included predation by birds
while the bats are in flight (in particular the Nankeen Kestrel Falco cenchroides which became
established on the island in the 1950s), habitat loss and alteration, altered prey availability,
vehicle-related mortality and altered climatic conditions.
The aim of this study was to investigate two of the most likely causes of decline: predation or
disturbance at roost sites, and disease. This report documents data collected in December 2005
– early January 2006, re-examines the possible causes of declines in light of this new
information, and outlines potential management options and future investigations.
13
Methods
Duration and timing of study
Field work on this project was undertaken over a 23 day period, from 12 December 2005 to
2 January 2006. The trip was timed to coincide with when the females were suspected to give
birth to their young. The timing of births was not previously known for this species, however,
many tropical microbat species time their reproductive cycles so that females give birth at the
start of the wet season to coincide with peak insect abundance. In addition, Tidemann (1985)
deduced from reproductive patterns found in March and September, that births were likely to
occur in December, at the start of the wet season. Prior to this study there was no information
on the types of roosts used by females to raise their young. By undertaking the field work at
this time, maternity roosts, which are likely to be the most critical roosts for the species, could
be identified. Many species of insectivorous bats utilise a range of diurnal roosts outside the
breeding season but display more specific maternity roost site selection (Kunz and Lumsden
2003).
Although the field work was conducted at the start of the wet season, only limited amount of
rain fell during the period. Some rain fell on 11 of the 23 sampling days, however, on most
days this was less than 3 mm (Bureau of Meteorology records). The mean daily maximum
temperature during this period was 27.9 ± 0.7 oC and the minimum was 23.1 ± 0.7 oC (Bureau
of Meteorology records).
Detector sampling
Three PANCI ultrasonic bat detectors (AnabatV detectors linked to CFZcaims, Titley
Electronics, Ballina, NSW) were employed most nights in an attempt to locate foraging areas
being used at that time by pipistrelles. The equipment was housed in a waterproof box, set on a
customised tripod, with the microphone pointing down towards an angled sheet of perspex
(James 2005; Plate 1). Sites were sampled in the west and south of the island, in areas that the
pipistrelle had been recorded in 2004 (James 2004) or in 1998 (Lumsden et al. 1999), or in
adjoining areas. Appendix 1 provides the locations of the sites sampled. All sites were on
tracks or in small clearings. The equipment was set mid to late afternoon and retrieved the
following morning, enabling all night recordings directly onto the memory card in the
CFZcaim. All files were checked using AnalookW, and the number that represented bat
echolocation calls was recorded.
Trapping
Three PANCI harp traps (Austbat, Bairnsdale, Victoria) were used every night of the field trip
to trap animals to assess their health condition and to attach radio transmitters. To increase the
probability of capture, trap sites were concentrated in areas where the pipistrelle was known to
forage, based on the detector recordings. Two main areas were sampled. Firstly, traps were set
in the core foraging area in the west of the island along the start of the Winifred Beach Track
and in the area of secondary regrowth just to the west, along recently (May 2005) bulldozed
lines (Plate 2). Secondly, traps were set in the central-west section of the island where a small
number of calls had been recorded on the detectors (Plate 3; Appendix 1; refer Fig. 3). Traps
were set in potential flight paths along tracks. They were checked regularly during the night
and again early the next morning. Bats were placed in individual cloth bags to allow the
collection of faecal remains from each individual.
14
Plate 1. An ultrasonic bat detector set in place within a waterproof housing.
Plate 2. Trapping site along the recently bulldozed lines through secondary regrowth just
west of the start of the Winifred Beach Track.
15
Plate 3. Harp trap set at the eastern end of the Circuit Track along the edge of a new
rehabilitation area. A small number of calls were recorded on the detector at this site but no
pipistrelles were trapped.
Data collected on trapped individuals included age, sex, reproductive condition (for females)
and forearm and weight measurements. Age was assessed by the degree of ossification of the
finger joints, a characteristic that can only be used to recognise juveniles up to four months of
age (Anthony 1988). Four categories were used to describe reproductive condition of females:
pre-parous, indicating the female had not bred before; pregnant, assessed by the size of the
abdomen and by palpating it; lactating, where nipples were enlarged and milk was expressed;
and post-lactating where the nipples had regressed indicating the individual had bred previously
but was not currently in breeding condition. In the results, pre-parous and post-lactating have
been combined into a ‘non-breeding’ category.
To investigate the rate of recaptures, bats were individually marked using fur clipping. This
non-intrusive technique was used as a short term alternative to banding, as some species of bats
show an unacceptable rate of injury from bands (Baker et al. 2001), and the susceptibility of
band injuries in this species is not known. Six positions on the dorsal surface of the body were
used for fur clipping (shoulder, mid-body and rump on each side of the body, numbered A-F).
A sufficiently large number of combinations was achieved by clipping up to four positions, for
individuals of each sex (Plate 4).
Throughout this report means are provided ± 1 standard deviation (SD). All grid references are
provided in WGS84, Zone 48.
Collection of biological samples to assess health status
All trapped individuals were assessed for their health condition using a number of techniques.
Individuals were examined externally for obvious signs of ill-health (e.g. the presence of
wounds, lesions or obvious discharges). Swabs were taken for viral and bacteriological testing
16
Plate 4. Individual recognition was achieved by fur clipping. This individual was clipped
on the left and right shoulder and the right rump, and was given the number ABF.
from the external opening of the respiratory system, urogenital area and wing membrane.
Faeces collected from bats held in individual cloth bags were used to produce slides from direct
smears and faecal floats. Any urine that was produced during handling was collected.
Searches were undertaken for external parasites by blowing through the fur of the dorsal and
ventral surface of the body, and by examining the wing membranes. The biological samples
taken from each individual are provided in Appendix 2. Fur was collected during the process
of fur clipping for individual recognition. Samples of fur were mounted onto slides to provide
reference material for dietary studies of potential predators.
Blood samples were taken from a subset of individuals. Blood sampling has been shown not to
impact on the survival of Big Brown Bats Eptesicus fuscus in the USA (Wimsatt et al. 2005).
However, because of the very small size of the pipistrelles, we decided, in conjunction with the
ARI Ethics Committee, that individuals would be subjected to either blood sampling or the
attachment of a radio transmitter, but not both. Heavily pregnant females were also not
sampled. Therefore blood was taken only from males and non-pregnant females who were not
fitted with a transmitter. Blood samples were taken from the lateral tail vein. This was the
only vein found to be superficial enough and large enough to obtain a sample. In some smaller
individuals (predominantly males), even this vein was too small to successfully obtain a
sample. To take the blood, the animal was gently restrained and the vein was pierced with a
sterile 30 gauge needle. A micro-pipette tube was placed over the wound and the blood
allowed to travel up the tube by capillary action until the desired amount was reached. The
tube was removed and a sterile cotton bud was placed on the wound with enough pressure to
stop the blood flow. The blood from the micro-pipette was then used to make two smears onto
microscope slides, although for some individuals it was possible to only obtain enough blood
for one smear.
17
All biological samples were transported (under quarantine conditions) to Victoria for
processing. Half of the swabs were sent to Gribbles Veterinary Pathology Laboratory in
Clayton for bacterial culture and analysis. The other half were sent to CSIRO Australian
Animal Health Laboratory for viral isolation. The blood smears were analysed by Gribbles
Veterinary Pathology Laboratory. An evaluation of the composition and concentration of the
cellular components of the blood was conducted. This evaluation included the following tests:
red blood cell count, white blood cell count, differential white blood cell count (i.e.
classification of the white blood cells as neutrophils, lymphocytes, monocytes, eosinophils and
basophils) and platelet count. Smears were also examined for blood parasites.
Little is known of blood parameters for microbats, and comparative material was not available
to put the findings from the pipistrelles into context. Therefore, for comparison, blood was
taken from 16 individuals of forest bats from Coranderrk Bushland Reserve at Healesville,
Victoria (11 Little Forest Bats Vespadelus vulturnus, four Large Forest Bats V. darlingtoni and
one Southern Forest Bat V. regulus). These species are of a similar size and flight pattern, and
the genera Pipistrellus and Vespadelus are closely related (Volleth and Tidemann 1989). The
blood was collected and analysed using the same methodology, and by the same people, as for
the pipistrelles.
Location of roost sites
To investigate roosting requirements of the Christmas Island Pipistrelle, radio transmitters were
attached to individuals caught while foraging at night and then located in their roosts during the
day. The original intention was to track bats both in the core of their current distribution and at
the eastern limit of their range. It was hoped that examining roosts in the eastern area would
assist in understanding the reasons behind the westward contraction of the species. However,
as it was not possible to trap animals in this area (see Results), all tracking was undertaken on
individuals caught at the main trapping site near the start of the Winifred Beach Track (see
Fig. 3).
Due to the small size of these bats, the lightest available transmitters were used (Holohil
Systems, Ontario, Canada, Model LB-2N, weight 0.35 g). This represented less than 10% of
the mean body weight of the individuals that were tracked (females 4.3 ± 0.3 g, n = 20, 8.1% of
body weight; males 4.0 ± 0.2 g, n = 4, 8.8% of body weight). Larger individuals were selected
for tracking in preference to smaller ones, to reduce this proportion. Although the weight of the
transmitter was heavier than the 5% recommended by Aldridge and Brigham (1988), it was
within the 10% range recommended by Bradbury et al. (1979). Insectivorous bats are capable
of carrying large weights as illustrated by females transporting young between roost sites,
which may be up to 75% of their own body weight (Lumsden and Bennett 1995). In 1998,
Lumsden et al. (1999) successfully radiotracked Christmas Island Pipistrelles using transmitters
that weighed 0.48 g (the lightest that were available at the time), representing 12.7% of the
weight of those individuals. Observations on their flight behaviour and the distances
individuals flew between roost sites and foraging areas (up to 2 km) indicated that the
pipistrelles were able to successfully carry this weight. It was considered that for the short
duration of transmitter attachment (less than 10 days) that this would not significantly affect
these individuals (Lumsden et al. 1999).
Twenty-four individuals were tracked: 20 females (18 lactating, 2 non-breeding) and four
males. Lactating females were predominantly selected for tracking to enable the location of
maternity roosts. No transmitters were attached to obviously pregnant females to avoid adding
18
a further weight burden to these individuals. Lactating females leave their young in the roost
while they forage at night. The only times they carry their young in flight is when they move
them to a new roost. These distances are likely to be short (less than several hundred metres)
and this flight would take only a minute or two. Hence it is considered that the impact of
carrying the extra weight of the transmitter, in addition to the young, is likely to be minimal.
The transmitters were attached using Vetbond (3M Animal Care Products, USA) after first
trimming the fur on the dorsal surface between the shoulder blades (Plate 5). Bats were
released at the point of capture within several hours of their capture.
Plate 5. A radio transmitter fitted to a Christmas Island Pipistrelle.
Roost sites were located using Telonics TR4 and TR2 scanner receivers in conjunction with
omnidirectional and three element directional antennas. Signal range within the rainforest was
limited to less than 300 m. In some situations, especially after rain, signal strength was further
reduced to less than 200 m. To locate roost sites, all tracks within a 4 km radius of the capture
point were regularly driven, and numerous extensive walking transects were undertaken
through the forest within a 2-3 km radius of the capture point. In an attempt to locate
transmitters that could not be found using land-based searches, radiotracking was also
undertaken from a boat that travelled along the northern and western coastlines, from the
Settlement to Winifred Beach (Plate 6).
On detection of a transmitter pulse, the signal was then followed to determine the location of
the roosting bat. To assist locating the entrance of the roost, most roosts were watched at dusk
for emerging bats. The total number of bats emerging and the time of emergence of each
individual were recorded. Observers were in place up to 15 minutes prior to sunset. In low
light situations, a nightscope (Litton Electron Devices) was used to observe the bats leaving
roosts. Some roosts were observed on multiple nights. Roost exit watches also assisted in
determining if the transmitter was still attached to the bat.
19
Plate 6. Transmitter signals were searched for from sea as well as land.
Attempts were made to check known roosts each day to investigate long term roost usage and
to determine when the transmitters fell off. However, due to the inaccessibility of most roosts
and the time required to reach them, this was not always possible.
Once a roost was located a range of measurements were taken of the tree and surrounding area,
including the height and diameter of the roost tree, if it was dead or live, type of roost cavity,
height of cavity, distance to surrounding vegetation and canopy cover. To assess the
availability of potential roost trees, the number of live and dead trees were counted within a
0.1 ha area surrounding each roost tree. In addition, a number of transects were walked, both in
and outside of the area containing the known roost trees, to assess the number of dead trees
with potential roost sites.
Observations of roost trees using infra-red cameras
Predation or disturbance episodes at roosts are difficult to observe and are likely to happen only
infrequently. To increase the chances of recording such an event, infra-red cameras
(Faunatech, Digicam Surveillance Cameras, Bairnsdale, Victoria) were developed to capture
the image of potential predators at roost trees (Plate 7). These infra-red cameras operate in
complete darkness with no visible illumination of the scene. The camera units are fully
waterproof and operate in all weather conditions. The cameras were set on tripods that could
be attached to the side of trees or set on the ground, to prevent interference from Robber Crabs
Birgus latro. Movement sensors trigger the camera resulting in either a still photo or short
video sequence. A number of sensor types were tested while constructing these cameras to
ensure that all the potential species that may be causing predation or disturbance could be
recorded, as well as the movement patterns of the pipistrelles entering and leaving the roost.
The only sensor found to detect the movement of small animals (i.e. the size of the Common
20
Wolf Snake and Giant Centipede) was an active infra-red beam. Large memory cards (1 GB)
and large external batteries were used to enable continuously sampling for extended periods of
time. The photos could then be readily downloaded and checked to determine species in the
vicinity of the roost.
It had originally been intended to set these cameras at the entrances to roost cavities in an
attempt to observe pipistrelles exiting and entering, as well as other species moving in and out
of the roost. Prior to this study, it had been anticipated that maternity roosts may be in tree
hollows and hence it was expected that a single beam, or series of beams, could detect all
animals moving in or out. However, all the maternity roosts located during this study were
under loose bark on heavily-decayed, dead trees (see Results) and it was not possible to attach
the sensor brackets either side of the roost entrance without the risk of dislodging the loose bark
or causing the tree to collapse. In addition, there was no single entrance to the roost and hence
a single beam could not cover all possible entrance points. Therefore, the decision was made to
install the cameras at the base of the roost trees so that at least potential predators moving up
and down the roost tree could be observed.
Due to problems with the delivery of the equipment, only one unit was available during the
field work period. Extensive testing was undertaken during this time. Later when all four
cameras were available, they were set at roost trees in April 2006, and have been monitored
since this time by PANCI staff.
Plate 7. A Faunatech Digicam Surveillance Infra-red Camera set up on tripod with
movement sensors attached to the tree to detect the movement of animals up and down
the tree. (Note this photo was taken when testing the equipment – this tree is not a pipistrelle
roost tree).
21
Observations on other species
Extensive searches were made for Nankeen Kestrel feeding pellets, and observations were
made of foraging behaviour, predominantly in open areas in the west of the island within 1 km
of known pipistrelle foraging areas. Rocky areas were searched in the extensive minefield
areas south and west of the West White Beach car park (Fields 25 and 26). Prey remains were
identified in the field using a magnifying glass.
All incidental records of Feral Cats and Common Wolf Snakes from the west of the island, seen
when driving or walking through the forest, were recorded. Standardised searches were
undertaken for Common Wolf Snakes, African Land Snails and Giant Centipedes within a 1 ha
radius of all known roosts over a 30 minute search period. These searches involved turning
fallen timber and debris on the ground and searching under loose bark at the base of trees.
22
Results
Detector sampling
The purpose of the detector sampling was to locate additional areas that the Christmas Island
Pipistrelle occurred in, to further define the current distribution and to identify areas to focus
trapping efforts. A total of 53 detector nights were undertaken with sites spread across western,
central and southern sections of the island (Fig. 2). Full details of the results from the detector
sampling are provided in Appendix 1. No pipistrelle calls were recorded at 37 (70%) of these
sites. High numbers of calls were only recorded in the far west of the island, especially just to
the west of the start of the Winifred Beach Track along the recently bulldozed lines in
secondary regrowth, where on each of two nights over 1500 calls were recorded, indicating a
number of individuals were intensively feeding in the area.
Sampling was undertaken in the Rehab 22S area where calls were recorded in 1998 and 2004
(Lumsden et al. 1999; James 2004). A very low number of calls were recorded, ranging from
1-6 per night (Fig. 2, Appendix 1). Some of these calls were in quick succession, which might
suggest that a small number of individuals were on route from a roosting area to a foraging
area, or a single individual circled over the microphone several times. However, despite
extensive sampling in areas surrounding these sites, no foraging or roosting areas were located.
The very low number of calls plus the inability to trap any bats here (see below) suggests that
only a very small number of individuals use this area.
Three detectors were set on the eastern end of the Circuit Track (see Plate 3) – two of these
recorded a single call each, while the third recorded three calls (Fig. 2; Appendix 1). No calls
were recorded from all the other sites sampled in the centre and south of the island.
Number of individuals caught
A total of 54 harp trapnights were conducted: 33 trapnights at the start of the Winifred Beach
Track and the nearby bulldozed lines, and 21 in the areas to the east where calls had been
recorded on detectors (Fig. 3). Fifty-two individuals were trapped, three of which were
recaught at a later time. All were trapped along the Winifred Beach Track and adjacent area.
No individuals were trapped in the area to the east, despite extensive trapping effort (Fig. 3).
It was not statistically valid to undertake a mark-recapture analysis to estimate the size of the
remaining population, due to the low retrap rate in the trapping results, and because all bats
were caught in the one location.
Females were caught more often than males, accounting for 73% of the captures (38 females vs
14 males). The majority of females were breeding, with 82% either pregnant or having
recently given birth (Table 1). Of the seven females that were not in breeding condition, one
appeared to have bred in previous years, while the other six had not bred before. Some species
of bats breed in the first year of their life, while others do not commence breeding until the
second year (Barclay and Harder 2003). It is not possible to age bats once they are more than
several months of age, and so the age of these non-breeding females is not known. It is
possible that these six females were first year individuals, although an alternative explanation
may be that they were adults that were not breeding for some unknown reason.
23
The Settlement
West White Beach
#
S
#
#
The Dales # S
#
S
#S
S
#
S
###
#
# ######
#
#S
S
# #
#
#
S
##
##
Winifred
Beach
#
High bat activity
#
S
S Low bat activity
#
#
S
#
No bat activity
Christmas Island
National Park
2
0
2
4
##
##
##
#
# ###
#
#
N
South Point
Kilometers
Fig. 2. The locations sampled using bat detectors with an indication of the number of
calls of the Christmas Island Pipistrelle that were recorded.
24
The Settlement
West White Beach
The Dales
#
#
S
S
#
S
## #
#
#
##
Winifred
Beach
#
S Bat captures
#
#
S
No captures
N
Christmas Island
National Park
2
2
0
0
2
2
Kilometers
4
4
South Point
Kilometers
Fig. 3. The locations trapped for the Christmas Island Pipistrelle using harp traps,
showing the sites where bats were caught. The locations where bats were caught in the west
of the island were along the start of the Winifred Beach Track and the adjacent bulldozed lines,
while the trapping in the central-west area was along the eastern end of the Circuit Track and
the track to Rehab 22S.
25
Table 1. The number of individuals caught, their reproductive condition, forearm length
and weight. Retrapped individuals have been excluded.
Sex
Male
Female
Reproductive
condition
All
All
Pregnant
Lactating
Non-breeding
Number caught
Forearm (mm)
Weight (g)
14
38
6
25
7
31.1 ± 0.6
31.6 ± 0.6
31.2 ± 0.6
31.7 ± 0.6
31.4 ± 0.7
3.8 ± 0.3
4.5 ± 0.5
5.5 ± 0.3
4.3 ± 0.3
4.1 ± 0.2
Pregnant females weighed considerably more than lactating or non-breeding females (Table 1).
The heaviest pregnant female trapped was 5.6 g when first caught on 14 December 2005 and a
massive 6.2 g, with parturition considered to be imminent, when retrapped on 22 December
2005. If the non-breeding weight of this individual was 4.1 g (the mean for non-breeding
individuals), this would mean that the weight of the young (and associated fluids etc) was 2.1 g.
The body weights for individuals caught in December were significantly higher than the
weights of individuals caught in 1998 during May-June (Lumsden et al. 1999) (males 3.8 ± 0.3
g vs 3.4 ± 0.3 g; t = 4.82, p < 0.001; females [excluding pregnant females] 4.3 ± 0.3 g vs 3.6 ±
0.23 g; t = 12.33, p < 0.001). It is not known if this represents an improvement in the condition
of the bats between 1998 and 2005 or reflects seasonal changes in weight in response to insect
availability.
Disease investigation
External examinations of the 52 trapped individuals revealed no obvious external indication of
ill-health. They all appeared in good physical condition, their fur looked healthy and they had
high body weights. The only external parasites found were a small number of mites on the
wing membranes of 10 of the individuals (19%) (Appendix 2). Insectivorous bats on mainland
Australia typically have mites, ticks and bat flies (Jackson 2003). No ticks or bat flies were
observed on the pipistrelles. Examination of the faecal smears and floats revealed no evidence
of internal parasites (Ian Beveridge, Melbourne University, pers. comm.).
The swabs sent for bacterial analysis revealed no bacteria when examined microscopically and
the bacterial culture produced only light growths of mixed skin flora. These results indicate
that no significant bacterial pathogens were detected in these samples. Similarly, no viruses
were detected in the swabs sent for viral isolation.
The blood smears showed the red blood cells to have mild to moderate polychromasia with
occasional nucleated red cells. Polychromasia and nucleated red cells are associated with
regenerative anaemia, and in domestic animals are usually an indicator of previous or chronic
disease. This indicates the bone marrow is healthy enough to respond to a previous loss of red
blood cells. The morphology of the white blood cells was normal and the number of platelets
was adequate. The blood was considered to be leukopenic, i.e. lower than expected numbers of
white blood cells were found. No blood parasites were found. Blood parasites are considered a
possible cause of the extinction of the two species of endemic rats on Christmas Island at the
start of the 20th century (Pickering and Norris 1996).
26
Both regenerative anaemia and leukopenia are non-specific conditions which have been
associated with a range of diseases such as infectious conditions and toxic insults. No specific
toxins were investigated in this study, however samples were collected for such analysis if, and
when, potential toxins are identified. Regenerative anaemia can also result from any chronic
disease. However, the significance of these findings was unclear because there was no predecline data on the blood characteristics of the Christmas Island Pipistrelle, nor was there any
comparative material from other similar species. The leukopenia was assumed because the
numbers of white blood cells found in the pipistrelles would be considered low in other
mammal species. The white blood cell count was predominantly 1-2 x 109/L (Appendix 3).
Australian native mammals typically range from 2-15 x 109/L (Clark 2004). Little published
information is available on bats. For example, a recent book on the haematology of Australian
mammals (Clark 2004) provides white blood cell estimates for a wide range of species
including flying-foxes, but none for insectivorous bats. The Grey-headed Flying-fox Pteropus
poliocephalus has been recorded with white blood cell counts of 10-22 x 109/L, and some
overseas species of flying-foxes have 0.8-6.4 x 109/L (Clark 2004).
Blood smears were taken from three species of Victorian forest bats (Vespadelus spp.) in
March 2006 to provide comparative material from similar-sized, closely related species. The
red blood cells of the forest bats also showed a level of polychromasia, and this pattern was
consistent in all 16 individuals (Appendix 4). Therefore, polychromasia may be a normal
feature of microbat blood rather than indicating previous or chronic disease (Philippa McLaren,
Gribbles Veterinary Pathology Laboratory, pers. comm.). The Victorian forest bats were also
found to have low white cell counts, although not quite as low as the pipistrelles (Appendix 4).
The forest bat white blood cell counts ranged from 2-5 x 109/L (compared to 1-2 x 109/L for the
pipistrelles). The relative proportion of the white blood cell types of the forest bats was similar
to the pipistrelles (Appendices 3 and 4). Therefore, it appears that microbats may have lower
white blood cell counts than other mammals, but that the pipistrelles are somewhat lower again.
The significance of this finding however remains unclear, as it is not known if these levels are
typical for this species, typical for island species that are not exposed to high levels of disease
factors, or if in fact it does represent some form of ill-health. Therefore, further health research
is necessary to clarify the potential role of disease in the decline of this species.
Roost sites
Twenty-four individual were tracked during this study: 20 females (18 lactating, 2 nonbreeding) and four males. A number of problems associated with radio-tracking these
individuals were encountered. Firstly, more than half of the individuals fitted with transmitters
could not be located during the day (i.e. at roost sites) despite extensive searching by road, foot
and boat. Roosts were found for nine of the 20 females tracked, and two of the four males,
resulting in the location of 46% of the individuals. The second problem, which was likely to be
partly responsible for the first, was that the transmitters fell off the lactating females within a
very short period of time. For the individuals where the duration of attachment time could be
determined, transmitters remained attached to lactating females for 1.8 ± 0.8 days (n = 5),
whereas one non-breeding female retained the transmitter for nine days, and one male retained
its transmitter for 10 days. This pattern of transmitters falling off lactating females prematurely
has also been recorded for other species of insectivorous bats (e.g. Lumsden et al. 2002).
Since most of the maternity roosts that were found were located were under loose bark, when
the transmitters fell off the individual they usually fell to the ground below the roost. In these
situations the signal strength decreased considerably from the 200-300 m that it could be
27
detected when elevated in the roost. This meant that to locate a transmitter that was on the
ground the observer had to pass very close to the roost tree.
The nine females that could be found during the day led to the location of seven maternity
roosts. One of the females tracked to a roost was a non-breeding female, however, nonbreeding females of other species will often join maternity roosts (e.g. O’Donnell and Sedgeley
1999). Observations of the two roost trees used by this individual, the number of individuals
using the roosts and the behaviour of the bats, suggested that these were also maternity roosts,
and they are referred to as such in this report. The two males for which roosts were located led
to the finding of three roost sites. Roost sites were numbered 13 onwards (Table 2), so as not
to confuse them with the roosts located in 1998 (Roosts 1-12).
All individuals fitted with transmitters were trapped along the start of the Winifred Beach
Track and the adjacent area. All roosts were located to the west or south-west of the capture
point (Fig. 4), despite extensive searches in other directions. The maternity roosts were on
average 1.60 ± 0.22 km (range 1.23 – 1.78 km; n = 10) from the capture point, while the male
roosts were 2.15 ± 0.12 km (range 2.01 – 2.23 km; n = 3). All roosts were within primary
rainforest, either in gully lines or associated with The Dales along the west coast, both on the
plateau and the terraces.
Six of the seven maternity roosts were under loose bark on heavily-decayed dead trees. Three
of these trees were identified as Tristiropsis acutangula, while the identity of the other three
trees is uncertain (Table 2). As T. acutangula decays, the bark typically forms large sheets that
lift off the trunk leaving a space underneath several centimetres deep (Plate 8). The way the
tree shed its bark was similar for all six roost trees, irrespective of the tree species. The bark on
dead trees of other species did not exfoliate in the same pattern. The loose bark that formed the
roost sites appeared to be quite thick, with similar pieces of fallen bark from T. acutangula
trees measured at 4.4 – 11.1 mm thick. The cavities formed by these sections of lifting bark
had multiple entry and exit points, a factor that may be important in enabling bats to escape
from potential predators. These six roosts were very similar in structure, as shown in Plates 8
to 11. In some situations the trunk of the tree below the roost site was bare of bark (e.g. Roost
14; Plate 9), which may have restricted the movement of introduced species to the roost
entrance, while for others there was loose bark for much of the length of the tree (e.g. Roost 13;
Plate 10). The entrances to these roost sites varied in height from 7 – 24 m above the ground
(mean 10.8 ± 6.6 m) (Table 2). The seventh maternity roost was in a hole in the top of a dead
palm Arenga listeri (Plate 12), 19 m above the ground.
The three male roosts were very different in structure to the maternity roosts. Two were in the
suspended fronds of a pandanus Pandanus sp. (Plate 13), while the third was in the dead frond
of a palm (Plate 14). These were 4.5 ± 0.9 m above the ground. The roosts used by males were
similar to some of the roosts used by males and females during the non-breeding season in
1998 (Lumsden et al. 1999).
28
Table 2. Characteristics of roost trees used by the radiotracked Christmas Island Pipistrelles in December 2005. Note: roost number 16
was not used (a shed transmitter was found under this tree but it was not considered to be a roost tree). Grid references are provided in WGS84.
DBH is the diameter of the roost tree.
Roost
No.
13
14
15
17
18
19
20
21
22
23
Maternity/
Male roost
Maternity
Maternity
Maternity
Maternity
Maternity
Male
Male
Maternity
Male
Maternity
Grid reference
561886
561513
561513
561068
561110
560862
560862
561520
560684
561480
8840668
8840351
8840351
8841075
8841072
8840847
8840847
8840320
8840715
8842252
Tree species
Dead/
Live
DBH
(cm)
Height
of tree
(m)
Height
of roost
(m)
Tristiropsis acutangula
Tristiropsis acutangula
Dead
Dead
Dead
Dead
Dead
Live
Live
Dead
Live
Dead
33
52
31
54
46
22
22
53
35
61
25
25
19
20
13
12
12
22
12
25
7
9
19
7
7
5
5
11
3.5
24
Arenga listeri
unknown tree species
unknown tree species
Pandanus sp.
Pandanus sp.
Tristiropsis acutangula
Arenga listeri
unknown tree species
Type of roost
Under bark
Under bark
Hole at top
Under bark
Under bark
Suspended dead frond
Suspended dead frond
Under bark
Suspended dead frond
Under bark
29
29
Fig. 4. The location of roost sites of Christmas Island Pipistrelles found in December
2005. Maternity roosts are shown in red, and the male roosts in blue. The location where
individuals were caught foraging at night at the start of the Winifred Beach Track and the
adjacent bulldozed lines, is marked as the capture site.
30
Plate 8. Loose bark lifting off a dead Tristiropsis acutangula used as a maternity roost by
a colony of 32 Christmas Island Pipistrelles (Roost 14).
Plate 9. Maternity roost under bark on a dead Tristiropsis acutangula tree where there
was no loose bark below the roost site (Roost 14). The arrow indicates the roost location.
31
Plate 10. Peeling bark on a dead Tristiropsis acutangula used as a maternity roost by a
colony of up to 54 pipistrelles (Roost 13) where there was continuous bark for most of the
trunk of the tree. The arrow indicates an entrance to the roost.
Plate 11. Roost under lifting bark used by 15 female pipistrelles (Roost 17).
32
Plate 12. Maternity roost in the top of a dead Arenga Palm (Roost 15), used by
48 individuals.
Plate 13. Suspended dead pandanus fronds used as a roost used by a male pipistrelle.
33
Plate 14. Roost used by a male pipistrelle in a dead palm frond.
Availability and longevity of maternity roosts
The availability of potential maternity roosts was assessed in three ways.
1. The number of live and dead trees were assessed in a 0.1 ha area surrounding each
maternity roost, with 1794 trees counted, of which only 15 (0.84%) were dead trees (of any
species).
2. To increase the search area and make it more specific to potential roost sites, a count was
made of dead trees with sheets of exfoliating bark, similar to those used as roost sites,
within a 50 m radius of each maternity roost (i.e. 0.8 ha). Twenty-one potential roost trees
were located within these seven 0.8 ha areas, resulting in an average of 3.8 potential roost
trees/ha (including the roost tree itself) within the vicinity of roost sites (note that this
calculation is based on roosts under exfoliating bark on dead trees and does not assess the
availability of roosts in the top of palms such as Roost 15). Some of these trees were
subsequently found to be used as roosting sites later in 2006: in December 2005 four dead,
roost-type trees were recorded around each of Roost 13 and Roost 21, with one of these
trees at each site used by female pipistrelles in August 2006 (David James and Glenn Hoye,
pers. comm.).
3. Transects were walked through The Dales area (often when walking between roost sites) to
further assess the availability of roosts in this general area. A total of 2760 m were walked
searching for dead, roost-type trees, 50 m either side of the transect. Fifteen trees were
observed at a density of 0.54 trees/ha. Further transects were walked to the east of the main
roosting area (i.e. to the east of Winifred Beach Track and along the Circuit Track),
searching 20 m either side of the transect, with only four dead, roost-type trees seen, at a
density of 0.17 trees/ha.
34
Although the data are limited, and these figures may underestimate the number of potential
roost sites (especially recently dead trees where most of the bark remained on the tree making
them less obvious), they suggest that the availability of potential maternity roosts in the general
area is low, and that the pipistrelles are roosting in areas that have higher densities of preferred
roost sites.
Many of the dead trees used as maternity roosts were heavily decayed and likely to collapse in
the near future. One of the roost trees (Roost 18) collapsed two days after it was located as a
roost site. It was first found on 21 December 2005 (Plate 15) when a female carrying a
transmitter shifted to it from a nearby roost (Roost 17, 17 m away). An exit count was
conducted on Roost 18 on the night of 22 December. The following morning the tree was
found on the ground (Plate 16). A thorough search was made of the tree, including under the
bark remaining on the tree and underneath the tree, to determine if any bats were killed in the
fall. No dead bats were found: the only remains observed were of several squashed crabs. The
roost exit count of Roost 17 on 20 December, prior to the bats shifting to Roost 18, revealed 12
bats. Fourteen bats were counted from Roost 18 on 22 December before it fell, and a
subsequent count of Roost 17 on 24 December revealed 15 bats. Assuming that this was a
single colony of bats that alternated between these two roost trees, it appears that all, or at least
most, of the bats survived. It is not known if the tree fell during the night or day. If the tree fell
at night while the adults were away foraging they would not have been directly impacted. If,
however, there were young in the roost when the tree fell they would have been unable to
escape. The female that led to the location of these two roosts was in non-breeding condition.
We have made the assumption that this was a maternity roost and that this female was roosting
with lactating females, because of the type of roost used, the number of bats in the roost, the
behaviour of bats and since non-breeding females of other species often join maternity roosts.
However, if this assumption is incorrect and all individuals were non-breeding, no young
would have been in the roost. Alternatively, if it was a maternity roost and the tree fell during
the day, there may have been enough warning for the females to escape from the roost carrying
their young in flight. Video evidence of another roost tree collapsing (see below) suggests that
there may be some movement of the tree before it falls, hence giving some warning to the bats
inside.
Of the seven maternity roosts found in December 2005, four roost trees had collapsed by May
2006 (this study; David James, pers. comm.). In addition to the roost tree mentioned above,
Roost 15 and Roost 23 fell sometime in March 2006 after a period of particularly heavy rain
(David James, pers. comm.). Another roost tree (Roost 13) collapsed on 13 April 2006 as
shown in photos taken by the infra-red camera set at its base (Plate 17). In addition, exit counts
in August 2006 revealed that Roost 17 was not being used (David James, pers. comm.),
although it is not known if it had been abandoned or the bats were using a nearby roost at the
time and would return to it at a later date. The remaining two roost trees (Roost 14 and Roost
21) are 10 m apart and were probably used by the one colony of bats (although Roost 14 is now
no longer useable, see below).
The bark on some of these dead trees was very loose, appearing likely to fall off in the near
future. Therefore, even if the trees remain standing, there is a high probability that the roost
sites on these trees will remain for only a limited time. For example, the loose bark on Roost
14 (see Plate 8) had fallen off the tree by September 2006 resulting in this tree no longer
providing roosting opportunities (David James, pers. comm.). The bark under which the roost
was located on Roost 23 was the only piece of remaining bark on the tree when it was first
found in December 2005 (Plate 18).
35
Plate 15. Roost tree 18 when found on 21 December 2005.
Plate 16. Roost tree 18 when found two days later (23 December 2005), after collapsing.
36
Plate 17. Roost tree 13 falling over on 13 April 2006 as observed on the infra-red camera
set at its base.
37
Plate 18. The last remaining piece of loose bark on a dead tree, which was being used as a
maternity roost for a colony of 11 Christmas Island Pipistrelles (Roost 23).
To further investigate the longevity of roost sites, searches were made for the Christmas Island
Pipistrelle roost trees located in 1998 (Lumsden et al. 1999). The fate of eight of the 11 roost
trees could be determined from site photographs and the location of marker tape (Appendix 5).
Three of the four live roost trees located in 1998 remained in situ and appeared the same in
2005 (a large Syzygium nervosum, a strangler fig around a large tree and an Arenga listeri with
loose fronds). The forth live tree, an A. listeri had fallen but remained suspended in adjoining
trees, with the roost cavity area still present. The location of four of the dead T. acutangula
that were used as roost sites in 1998 was found in 2005. Remains of two of these trees were
found on the ground (Plate 19). In the other two locations the remains of the tree could not be
found. One was already highly decayed in 1998 and it is likely to have fallen soon after this
time and the remains have probably disintegrated in the intervening seven years. The other was
situated in the middle of a dense pandanus patch and the remains were no longer visible. In
both situations we were confident that the roost tree no longer remained standing. Therefore all
four roosts that were under bark on dead trees, i.e. the same as the maternity roosts, were no
longer available as roosts after a seven-year period.
No radiotagged individuals were located in any of the four 1998 live roost trees during the
current study. Further, a dusk watch was conducted at the large Syzygium nervosum (Roost 6,
Appendix 5) on 14 December 2005 to see whether any bats were using it at the time. No bats
were seen to emerge from this roost.
The rapid decline of maternity roosts, and the general low availability of alternate potential
roost sites are major concerns to the continuing survival of the Christmas Island Pipistrelle.
38
Plate 19. The remains of a Tristiropsis acutangula tree that was used as a roost site by
Christmas Island Pipistrelles in 1998 (Roost 2). The orange nursery tag used to mark the
tree in 1998 was still attached.
Colony size and roosting behaviour
Exit counts were used to determine the number of individuals using maternity roosts. Most
roosts were counted on only one occasion, although several were counted on multiple days
(Table 3). Roost 13 was counted four times (15, 16, 18 and 31 December 2005). On three of
these counts the numbers were very similar (52-54 individuals). The mean number of
individuals in maternity roosts was 29.4 ± 16.5 (range 11 – 54 individuals). Although several
attempts were made to observe males exiting roosts to determine colony sizes, none
successfully recorded bats. However, due to the structure of the roosts used by males, it is
likely that these roosts supported either a single individual or just a small number of bats.
Due to the limited amount of time the transmitters remained attached to the lactating females,
little information could be gained on the frequency of roost shifting. All lactating females were
recorded to use just a single roost during the time the transmitters remained attached. The nonbreeding female was recorded using two roosts, 17 m apart (Roost 17 and 18). One male was
recorded using two roosts, one in a dead pandanus frond (Roost 20) and a second in a
suspended palm frond (Roost 22). These two roosts were 220 m apart.
It appeared that, although the lactating females we radiotracked used only one roost during the
short period of time they could be tracked, the colonies to which they belonged used more than
one roost. For example, Roosts 14 and 21 were only 10 m apart and appeared to be used
alternatively by the colony. Thirty-two individuals were seen to emerge from Roost 14 on 16
December 2005. When another radiotracked lactating female led to the location of Roost 21 on
30 December, 39 individuals were seen to emerge. Exit counts of Roost 13 on consecutive
nights revealed different numbers (35 individuals on 15 December and 53 on 16 December)
39
suggesting some individuals were using alternative roosts. In addition, exit counts undertaken
by David James in March 2006 suggested that there was another roost close to Roost 13, as
only a few bats were seen to emerge from Roost 13 but numerous other bats were observed in
flight during the exit watch (David James, pers. comm.).
To determine the maximum number of individuals represented in the maternity roosts during
December 2005, the maximum count from each roost or pair of roosts was summed, resulting
in a total of 167 individuals (Table 3). This figure can be used as a minimum current
population size for the Christmas Island Pipistrelle. The true population size is likely to be
larger than this as we were unable to locate the roost sites of all individuals fitted with radio
transmitters. There will most likely be additional, as yet unlocated, roost sites, containing
animals not included in the above count. In addition, this figure does not include males which
are probably dispersed in roosts containing small numbers of individuals.
Table 3. The number of individuals recorded exiting maternity roosts and the maximum
number of individuals represented by these counts. Two roosts were counted on more than
one occasion. In calculating the maximum number of individuals, Roosts 14 and 21, and
Roosts 17 and 18 are considered paired roosts. Only a single figure for each pair of roosts is
included, with the highest count recorded from either roost used.
Roost
No.
1st
count
2nd
count
3rd
count
4th
count
Mean no.
indiv.
Max. no.
indiv.
13
14
15
17
18
21
23
Total
35
32
48
12
14
39
11
53
54
52
48.5
32
48
13.5
14
39
11
29.4 ± 16.5
54
–
48
15
–
39
11
167
15
Emergence times and investigation of daytime flight
Emergence patterns were observed during exit counts (n = 11 emergence watches at maternity
roosts). Pipistrelles emerged from roosts on average 13.3 ± 6.0 minutes after sunset (n = 365
observations). The earliest time a bat was seen to emerge from a roost was exactly sunset and
the latest was 31 minutes after sunset (Fig. 5).
After leaving the roost, individuals would often circle around the area for 5-10 minutes before
leaving for foraging areas. During these times they would sometimes fly high in canopy gaps
or above the canopy. For example, when conducting a roost watch at Roost 23 on 30
December, individuals were seen to fly above the roost at a height of 40-50 m above the
ground.
40
35
.
30
Number of individuals
25
20
15
10
5
0
-1
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
Time after sunset (mins)
Fig. 5. Emergence times of Christmas Island Pipistrelles from maternity roosts in
December 2005 (n = 365 observations).
In 1984, Tidemann (1985) reported Christmas Island Pipistrelles hawking insects along roads
and ecotones during the late afternoon, 1.5 hours before sunset. No daytime foraging of the
pipistrelle was observed in studies in 1994, 1998, 2004 and 2005 (Lumsden and Cherry 1997;
Lumsden et al. 1999; James 2005), with bats first appearing during the dusk period. This led to
the suggestion that a temporal shift in foraging behaviour had occurred, possibly due to
predation risk from a diurnal predator, such as the Nankeen Kestrel (Lumsden et al. 1999;
James 2005). Foraging by bats during daylight hours on islands elsewhere in the world has
been attributed to a lack of diurnal avian predators (Speakman 1995).
To examine this aspect further, we reassessed the data on emergence patterns recorded during
earlier studies, by examining Chris Tidemann’s field note books from his trips to the island in
1984 and 1988, and emergence patterns observed in 1998 (Lumsden et al. 1998). The
following extracts are from Chris Tidemann’s notebook regarding observations of bats flying
during daylight hours in 1984:
24/8/84 – ‘Saw Pipistrellus flying at 652414 at 5.00 pm – at least 1 hr < sunset. Several
flying close to ground at ca 1.5 m – catching insects, some very close to ground. Others
also flying above or near canopy level – few Swiftlets up high flying with Pipistrellus’.
27/8/84 – ‘Pipistrellus sightings at 722412 at 5.30 pm, and at 714428 at 6.20 pm’.
Comment – ‘Seems likely that Pipistrellus in absence of predators or competitors can
afford to become active during daylight hours – 5.00, 5.15, 5.30 (dark at ca 6.10) and also
exploit all feeding areas from < 1 m off the ground to at or just above canopy level.’
41
In June – August 1988, Chris Tidemann collected 21 pipistrelles by shooting them during the
late afternoon/early dusk period. Such shooting required sufficient light to bring the pipistrelles
down and then find them on the ground, which is not easy to do in low light levels (C.
Tidemann, pers. comm.). Hence, although the exact times were not recorded, there were many
instances in 1988 of pipistrelles flying during the period when the kestrels would have been
foraging (C. Tidemann, pers. comm.). In the 1980s kestrels were seen on most days but only in
low numbers, primarily foraging over secondary regrowth (C. Tidemann, pers. comm.).
The earliest observation of a bat flying in the 1980s, where the time was recorded, was 5.00
pm, which was 55 minutes prior to sunset (sunset is 5.55 pm on these dates), rather than ‘1.5
hrs before sunset’ as reported by Tidemann (1985). This apparent discrepancy is probably due
to terminology, i.e. the difference between official sunset and when it becomes ‘dark’.
The time of emergence of the first bat from roost sites watched in 1998 was on average 5
minutes prior to sunset, although some individuals were observed flying nearby as early as 19
minutes prior to sunset (Lumsden et al. 1999). Individuals left their roosts earlier during
overcast weather than on clear nights. During the observations in 2005 the earliest bat to
emerge from a maternity roost was exactly sunset and the mean time of emergence of the first
bat was 6 minutes after sunset. It is not known if the apparent difference between the 1980s,
1998 and 2005 emergence times represents a shift in behaviour, or is due to differences
associated with the season, weather or reproductive condition of the females.
The roost emergence data is used from the 1998 and 2005 studies as it provides more accurate
information of emergence times than the detector data, as often the roost sites were some
distance from the foraging grounds. For example, in 1998 the earliest bats were recorded on
the detectors was 5-10 minutes after sunset.
Observations of roost trees using infra-red cameras
The infra-red cameras have been operating at a number of roost trees since February 2006. The
only potential predators filmed climbing the base of the roost trees have been the Black Rat and
Giant Centipede (Plates 20 and 21), and more recently a Common Wolf Snake (David James,
pers. comm.). As it was not possible to set the cameras at the roost entrance, it can not be
determined if either species accessed the roost or preyed on roosting pipistrelles.
42
Plate 20. Observation of a Black Rat climbing a Christmas Island Pipistrelle roost tree
(photo provided by David James).
Plate 21. Observation of a Giant Centipede climbing a Christmas Island Pipistrelle roost
tree (photo provided by David James).
43
Nankeen Kestrel observations
Nankeen Kestrels were common throughout the more open or disturbed areas of the island
including adjacent secondary regrowth and the edges of primary rainforest (Plate 22). They
appeared to be more abundant than in 1998 (Lumsden et al. 1999), although this could not be
quantified.
Plate 22. Nankeen Kestrels were common throughout the disturbed areas of the island.
One hundred and one Nankeen Kestrel feeding sites, comprising prey remains and pellets, were
located on elevated limestone rock outcrops in mined/rehabilitation areas or under branches and
other vantage points. These were predominantly in Fields 25 and 26 in the west of the island
(Plate 23, Appendix 6). A total of 2,234 individual prey items were identified in these remains
(based on pairs of legs or elytra) of which 97.4% were of the large grasshopper Volanga
irregularis (Table 4). This species was recorded at 100% of the feeding sites. Smaller
numbers of other Orthoptera, Coleoptera and Lepidoptera were recorded. Three individuals of
the introduced skink Lygosoma bowringii were recorded, and the feathers of the Christmas
Island Glossy Swiftlet Collocalia esculenta natalis were observed at 10% of the 101 feeding
sites. No remains of Christmas Island Pipistrelles, or any other mammals, were found.
Observations were made of foraging Nankeen Kestrels in Fields 25 and 26, within 1 km of the
pipistrelle foraging area at the start of the Winifred Beach Track. All feeding observations
were of snatches against surfaces such as tree foliage or the ground. The amount of time spent
foraging over different habitats was recorded (n = 2895 seconds of observations). Kestrels
spent 31% of this time foraging over the canopy of primary rainforest, while 38% was spent
over secondary regrowth. Both these situations are used extensively as foraging habitat by the
Christmas Island Pipistrelle.
44
Table 4. The prey items identified from feeding remains of Nankeen Kestrels,
predominantly in the west of the island at Fields 25 and 26. The number of individuals is
based on the number of pairs of legs for Orthoptera (grasshoppers), and the number of pairs of
elytra for Coleoptera (beetles) and Lepidoptera (moths). All Glossy Swiftlet remains were
feathers and hence no assessment could be made of the number of individuals these remains
represented.
Prey Type
Invertebrates
Large grasshopper Volanga irregularis
Other Orthoptera
Christmas Island Jewel Beetle
Chrysodema simplex
Click Beetle (Elateridae)
Unidentified Coleoptera
Unidentified Blattodea
Meadow Argus (Lepidoptera)
Reptiles
Lygosoma bowringii
Birds
Christmas Island Glossy Swiftlet
Collocalia esculenta natalis
No. ind.
% ind.
No. of
% of feeding
sites
feeding sites
2175
2
33
97.4
0.1
1.5
101
2
21
100
2
21
8
3
2
8
0.4
0.1
0.1
0.4
1
3
2
6
1
3
2
6
3
0.1
3
3
10
10
Plate 23. Nankeen Kestrel feeding remains comprised predominantly of the large
grasshopper Volanga irregularis.
45
Feral Cat sightings
Feral Cats were commonly observed throughout the island (Plate 24) and although not
quantified, appeared more abundant than in 1998 during the Lumsden et al. (1999) study. The
locations at which cats were observed are shown in Fig. 6.
Plate 24. Feral Cats appeared to have increased in abundance since 1998.
The Settlement
###
#
#
West White Beach
The Dales
#
# # #
# #
#
#
##
##
#
#
#
#
Winifred
Beach
#
##
#
S
#
Cat sightings
N
Christmas Island
National Park
22 2 00 0 2 2 24 44
Kilometers
Kilometers
Kilometers
#
#
South Point
Fig. 6. Feral Cats sighted during field work on Christmas Island in December 2005.
46
Common Wolf Snake observations
Common Wolf Snakes were commonly observed on roads and in disturbed areas throughout
the island (Plate 25). The locations where Common Wolf Snakes were recorded in the west or
south of the island is shown in Fig. 7. Due to the common nature of the species, records were
not kept of sightings in the centre and northeast of the island. Most of the observations were of
animals on the road at night. However, extensive searches were also made under rocks and
fallen timber. Multiple individuals were sometimes found in these situations. For example, six
individuals were located under a single piece of wood beside the Dales Road in a disturbed area
near the Immigration Reception and Processing Centre.
Plate 25. Common Wolf Snakes were commonly observed on the road and in disturbed
areas in the west of the island.
While the majority of individuals were located in disturbed areas, four observations were along
roads or tracks within primary rainforest, with a further three observations on the edge of
primary rainforest. No Common Wolf Snakes were located in systematic 30-minute reptile
searches centred on each roost tree. Recently (February 2007) a Common Wolf Snake was
photographed at a roost tree in primary rainforest, a considerable distance from tracks or
disturbed areas.
In addition to the animals found in the west of the island, two individuals were located in the
southern section of the island (Fig. 7). This species had not previously been recorded in the
southern section of the island (James 2005). One of these individuals was a very small
juvenile, indicating a breeding population is present in this area.
47
The Settlement
West White Beach
#
#
The Dales
#
##
####
#
#
#
##
#
Winifred
Beach
#
S
Wolf Snake observations
Christmas Island
National Park
N
#
#
2
2
0
0
2
2
Kilometers
4
4
South Point
Kilometers
Fig. 7. Common Wolf Snake observations in the west and south of the island. Note
sightings were not recorded for the central and northeast sections of the island.
Other observations
Comparisons were made of the change in abundance of other species between our studies in
1998 and 2005, based on general observations. The number of Giant Centipedes (Plate 26) and
Giant African Snails (Plate 27) had increased considerably. Although present in 1998, neither
species was commonly observed. However, in 2005 they were both extremely abundant, in
disturbed areas and throughout primary rainforest. Giant Centipedes are highly arboreal and
have been observed climbing pipistrelle roost trees (see Plate 21). Giant African Snails were
frequently found on the trunks of trees under loose bark to at least 3 m. The distribution of
Giant African Snails appeared patchy. No snails were found around the currently used roost
trees. In contrast, they were abundant around some of the roost trees used in 1998, but not
known to be occupied in 2005, to the north of the Winifred Beach Track (e.g. Roost 6). It is
not known if this finding is significant, or purely coincidental. Black Rats also appeared to be
more abundant in primary rainforest but this could not be quantified.
48
Noticeable changes to the rainforest ecosystem had also occurred as a result of the explosion
and subsequent control of Yellow Crazy Ants, for example the loss of Red Crabs Gecarcoidea
natalis and an increase in seedling regeneration. It is also likely that many of the changes
mentioned above are linked to the population explosion of Yellow Crazy Ants. At least part of
the area currently being used for roosting by the pipistrelles was infected by ants (James 2005),
although some roosts were in areas that remained ant free.
Plate 26. Giant Centipedes were abundant throughout all areas of the island in 2005.
Plate 27. Giant African Snails were also abundant throughout parts of the forest.
49
Discussion
Key findings of the study
This study provided new information on the biology, ecology and habitat requirements of the
Christmas Island Pipistrelle. Unfortunately, although considerable knowledge was gained, we
still do not have any direct evidence of the cause/s of decline of the Christmas Island
Pipistrelle. However, this new information will assist our understanding of the species and the
potential threatening processes.
Clarification of current distribution
The rapid decline in both distribution and abundance of 80-90% since the mid-1980s has been
well documented in previous reports (e.g. Lumsden et al. 1999; James 2004, 2005; Schulz and
Lumsden 2004; Lumsden and Schulz 2005). The most recent detector surveys by James (2004,
2005) revealed a continuing decline of 10% per year at the long-term monitoring sites. In an
attempt to determine the full extent of the range of the species and to locate additional
populations, the Christmas Island Biodiversity Monitoring Programme surveyed 95 additional
sites in 2005 (David James, pers. comm.). No new populations were found, and the majority of
the recordings (77.5% of the sites at which they were recorded and 97.4% of the calls) came
from an area of approximately 125 ha centred on mining leases and the adjacent National Park
at the start of the Winifred Beach Track. This result suggested that up to 95% of the population
fed in an area of 125 ha.
To further clarify the distribution of the pipistrelle, we undertook additional bat detector
sampling (53 detector nights), examining sites in the western, central and southern sections of
the island. This data confirmed the earlier detector survey results, indicating the species is
virtually confined to a small area in the far west of the island. Additionally, intensive sampling
in the central-west section of the island where the species was recorded in 2004, revealed that a
very small number of individuals remain in this area. Unfortunately, despite intensive trapping
efforts in this area, none of these individuals could be caught and so it is not known if these
records represent males or females and, if the latter, whether they were breeding. No records of
pipistrelles were recorded from 27 nights of sampling elsewhere in the centre or south of the
island (Fig. 2).
Estimation of the size of the remaining population
It was not possible to statistically estimate the population size using mark-recapture analysis on
the trapping data, due to the low recapture rate. However, a minimum population size could be
estimated based on the number of individuals observed in roosts. The maximum number of
individuals recorded in maternity roosts was 167 individuals. It is not known if males share
roosts with lactating females, or if maternity roosts are comprised predominantly of females
and their young, which is often the case for microbats (Kunz and Lumsden 2003). If males
roost separately it would be reasonable to assume that a similar number of males are present in
the population. Roosts could not be located for half of the individuals carrying radio
transmitters and so it is apparent that not all existing colonies, and hence individuals, were
located. Although we do not have hard data to support a population estimation of any size,
based on the number of captures, detector passes and individuals in maternity roosts, our best
guess is that the total population is in the order of 500 to 1000 individuals.
50
The number of individuals in the central-west area is estimated to be very small, based on the
low number of detector passes. It is possible that these detector passes represent less than five
individuals, although the foraging and roosting areas of these individuals would need to be
located before an accurate estimate could be made. As this area is approximately 6 km from
the known roost sites in The Dales area, it is unlikely that these are wide ranging individuals
from these colonies, and it is more likely that they are roosting somewhere close to where they
were recorded.
Confirmation of breeding status
Due to the rapid decline of the Christmas Island Pipistrelle, there was concern that unknown
factors may have been affecting the reproductive success of the population, by reducing the
number of females and/or the proportion of these that were breeding. Of the 52 individuals
caught, 73% were females. It is not known if this is an accurate reflection of the sex ratio of
the remaining population or is an indication of different foraging locations used by males and
females. However, it does indicate that there is still a high proportion of females in the
population. In addition, 82% of the 38 females caught were breeding (lactating or heavily
pregnant). This proportion is consistent with other species in this family (Vespertilionidae). A
review of the reproductive rate of a wide range of bat species revealed that 85% ± 3.1% SE of
females breed each year (for species that produce a single young; Barclay et al. 2004). The
Christmas Island Pipistrelle produces a single young each year (Tidemann 1985).
Prior to this study it was not known when females gave birth to their young. We were able to
confirm Tidemann’s (1985) prediction that this occurred at the start of the wet season in
December. In mid-late December 2005, females were either heavily pregnant with parturition
imminent, or had recently given birth, as judged by the condition of the lactating nipples.
Location of maternity roosts
Prior to this study the only information available on roosts used by the Christmas Island
Pipistrelle was from the non-breeding season, when individuals were found to roost in a variety
of situations in primary plateau rainforest: under exfoliating bark of dead trees (predominantly
T. acutangula); under flaking fibrous matter or dead fronds of live Arenga Palm or Pandanus;
under a Strangler Fig against the trunk of a canopy tree; and in the hollow of a large Syzygium
nervosum (Lumsden et al. 1999). The seven maternity roosts located during this study were
highly specific, with six of the seven under exfoliating bark on dead T. acutangula, or similar,
trees. The three roosts used by males were similar to some of those used during the nonbreeding season (by both males and females). All roosts were in or near gully lines within The
Dales area. Unlike most of the island, this area has free surface water, and hence the
environment here is likely to be more humid. However, it is not known if this is a factor in the
selection of roosting areas, or is contributing to the survival of the species in these areas. Roost
sites were located 1.3 – 2.3 km from the main foraging area at the start of the Winifred Beach
Track, indicating that these small bats are commuting considerable distances between roost
sites and foraging areas. This result suggests that they are actively selecting particular areas of
the forest in which to roost and in which to feed, and that these areas provide more favourable
conditions or increased resources.
Identification of further threats
An extensive list of potential threats to this species has previously been outlined by Schulz and
Lumsden (2004) and James (2005). An additional threat was identified during this study: the
loss of potential roost sites (in particular maternity roosts). Although not considered to be the
51
primary cause of the decline, the loss of suitable maternity roosts could now be having a
serious impact on the remaining population. The loss of five of the seven maternity roosts in
just nine months represents an extremely high rate of loss of roosts, especially since these types
of roost trees appear to be in low densities. Examination of the roosts located in 1998 revealed
that all of the roosts in dead trees (i.e. similar to the maternity roosts) had been lost since that
time. The loss of potential roosts should now be considered a serious threat to the survival of
this species (refer Threats section below for further discussion).
Investigations of potential predators
In an attempt to determine what predators may be accessing pipistrelle roosts, we developed
and tested infra-red cameras with movement sensors sensitive enough to detect small potential
predators. Once all the equipment had arrived on the island, these were set at the bases of
maternity roost trees by David James and other Parks Australia North staff. To date, Black
Rats Giant Centipedes and a Common Wolf Snake have been observed to climb roost trees. As
it was not possible to set the cameras at the height of the roost entrance due to the severely
decayed nature of these trees, it is not known if these animals actually investigated the
maternity roosts.
The extensive examination of Nankeen Kestrel feeding remains resulted in the identification of
Glossy Swiflets as part of the diet of this species. Given the similar flight pattern of swiftlets
and pipistrelles, it is possible that Nankeen Kestrels are also capable of catching pipistrelles in
flight. However, no evidence of pipistrelles were found in 101 feeding remains, most of which
were collected within 1 km of the main foraging area used by the pipistrelles. Since kestrels
feed predominantly in open areas, the pipistrelles are unlikely to be at risk from predation
within primary forest while they remain below the canopy. However, this risk increases when
they fly above the canopy or within openings in secondary regrowth or primary rainforest,
especially adjacent to more open habitats.
There appears to have been a temporal shift in the timing of roost exit since the mid-1980s,
with pipistrelles observed in flight up to 55 minutes prior to sunset in 1984, but not seen before
sunset in 2005. The reassessment of the early records of daytime flight has clarified the timing
and frequency of this behaviour. However, the cause and significance of this change in
behaviour can not be determined at this stage.
There have been obvious changes in the ecosystem on Christmas Island in recent years, many
of which are associated with the explosion and subsequent control of Yellow Crazy Ants.
General comparisons between 1998 and 2005 indicate a marked increase in the abundance of
many of the introduced species on the island, especially Common Wolf Snakes, Giant
Centipedes, Giant African Snails, Feral Cats, Black Rats and Nankeen Kestrels.
Investigation of disease
The 52 individuals trapped during this study appeared to be in good condition. All individuals
had high body weights, there were no obvious external signs of disease and the majority of
females were breeding. Had the females been in poor condition or their health compromised, it
could be expected that they would have forgone reproduction to increase their own survival rate
(Barclay et al. 2004). All of the biological samples collected were normal, with the exception
of the low white blood cell counts and possible regenerative anaemia. The white blood cell
counts were lower than for other species of similar-sized microbats. However, the significance
52
of this finding is unknown, as it can not be determined if this is typical for this species or if it
does in fact represent ill-health.
The number of tests that could be undertaken using biological samples was limited due to the
small size of the pipistrelles and the decision not to sacrifice any animals for internal
examinations. The amount of blood that could safely be obtained was enough to do blood
smears, but insufficient to also conduct biochemical testing. Other testing, such as for
Australian Bat Lyssavirus, require tissue or organ samples, which were not available. No
symptoms of lyssavirus were observed.
Since no previous veterinary work had been undertaken on the Christmas Island Pipistrelle and
no specific signs indicating disease had been observed, this resulted in a broad spectrum of
disease possibilities needing to be investigated. While a number of health parameters were
considered in this study, further research is required to explain the apparent species differences
and the possible role of ill-health in the decline. Compounding this uncertainty is a lack of predecline information on this species and the absence of health reference values, making it very
difficult to determine the significance of these observations.
This study found no definite indication of disease or ill-health in the remaining Christmas
Island Pipistrelle population. It is not clear if the low white blood cell count and the possible
regenerative anaemia is abnormal or normal for this population. Further investigations are
necessary if potential causes are to be evaluated. For example, toxic causes of regenerative
anaemia, such as lead poisoning, should be considered. Potentially there are many possible
environmental toxins which may affect health, survival and reproduction and to consider all
these is a large and costly undertaking. However, without further studies, we are also unable to
rule out the presence of disease and its possible contribution to the decline of the species.
Nomination for listing the species as ‘Critically Endangered’
During the preparation for this study a nomination was submitted to the Threatened Species
Scientific Committee (TSSC) to transfer the Christmas Island Pipistrelle from ‘Endangered’ to
‘Critically Endangered’ under the EPBC Act (Lumsden and Schulz 2005). The data collected
in December 2005 supported this nomination and this supplementary information was provided
to the committee in July 2006. The TSSC accepted this nomination and the species was listed
as ‘Critically Endangered’ on 12 September 2006.
Threat analysis
This section provides a summary of the potential threats to the long-term survival of the
Christmas Island Pipistrelle. This summary is based on studies undertaken in 1994 (Lumsden
and Cherry 1997), 1998 (Lumsden et al. 1999), 2004-2005 (James 2004, 2005), the Recovery
Plan (Schulz and Lumsden 2004) and the current study.
The cause of the rapid decline has not yet been identified, despite extensive investigations.
Apart from one death due to Yellow Crazy Ants (see below), no instances of mortality have
been recorded. The likelihood of observing the predation of a small, cryptic nocturnal bat is
extremely low, and predation may be occurring, but going unrecorded. However, it is not
known which (if any) of the following species may be preying on the pipistrelle.
53
Predation or disturbance by the Common Wolf Snake Lycodon aulicus capucinus
The Common Wolf Snake is a recent coloniser from South-east Asia that was first recorded on
the island in the Settlement area in 1987 (Smith 1988). Elsewhere it is known to forage
predominantly on lizards and occasionally small mammals, on the ground or in the lower forest
strata (Deoras 1978; Daniel 1989; Murthy 1990). The Common Wolf Snake is usually
associated with human habitation and on Christmas Island has been well established around the
Settlement area since its introduction (Rumpff 1992; Fritts 1993). Until 1998, the only records
elsewhere on the island were of a population around the buildings at Grants Well in the centre
of the island. In 1998, the location of a number of individuals further west indicated a range
expansion for this species (Cogger and Sadlier 1999; Lumsden et al. 1999). This westward
range extension has continued, and the species is now widespread across the island, including
in the far west (James 2005). Although this snake has been recorded on the edge of, and along
tracks into, the primary rainforest, it is not known the extent to which it is confined to the edges
or is spread throughout undisturbed rainforest tracts. The Common Wolf Snake is capable of
climbing trees (Auffenberg 1980) and may predate on roosting bats, particularly those
sheltering under exfoliating bark on the lower trunks of trees. A recent photograph of a
Common Wolf Snake climbing a roost tree in primary rainforest indicates that the species can
occur in primary rainforest well away from disturbed areas, and can climb at least the base of
trees.
Lumsden et al. (1999) considered this snake to be a likely factor in the observed decline and
westward range contraction of the Christmas Island Pipistrelle. In 1984, when Tidemann
(1985) recorded the pipistrelle to be widespread and common, including in the Settlement area,
the snake was not yet introduced to the island. However, by the early 1990s, extremely high
densities (up to 500 individuals per ha) were recorded in the Settlement (Rumpff 1992). In
1994, no pipistrelles were observed in the Settlement, although low levels of activity were
recorded at a single site nearby (Lumsden and Cherry 1997). By 1998, no pipistrelles were
recorded anywhere in the far north-eastern section of the island, and anecdotal evidence
suggested they disappeared from the Drumsite area of the Settlement several years before
(Lumsden et al. 1999). The expansion of the Common Wolf Snake into the central region of
the island coincided with the decline of the pipistrelle in that region during the 1990s.
Pipistrelles now longer occur in this part of the island.
Introduced snakes have had devastating impacts on island fauna elsewhere (e.g. Savidge 1987;
Fritts and Rodda 1998; Loope et al. 2001). For example, the Brown Tree Snake Boiga
irregularis has caused the extinction of 75% of the native forest bird species and half the native
lizards on Guam within 40 years of introduction (Loope et al. 2001), and reduced the Mariana
Fruit Bat Pteropus mariannus population to only 100 adults, with no recruitment for a decade
(Fritts and Rodda 1998). Of all the introduced predators on Christmas Island, the Common
Wolf Snake is the only species for which the timing of the introduction was immediately prior
to the decline of the pipistrelle and whose distribution pattern mirrors that of the pipistrelle.
Having evolved in the absence of snakes, the Christmas Island Pipistrelle is likely to be naive
to the risk of climbing snakes and would not have developed strategies to avoid such predation.
The Common Wolf Snake has had serious detrimental impacts when introduced to other
islands. For example, on Reunion Island it has been attributed with causing a decline in
endemic mice and the near extinction of a species of gecko (Cheke 1987). Weighing less than
5 g, the Christmas Island Pipistrelle is smaller than some of the vertebrate species the Common
Wolf Snake has been recorded preying upon. Non-flying young, weighing approximately 1 g,
left unprotected in roost sites while the females forage at night, would be particularly
54
vulnerable. In addition, adults could be preyed upon if trapped inside a roost with a single exit,
such as many tree hollows.
The arguments against the Common Wolf Snake being the main cause of the decline include
their limited climbing ability, ‘sit and wait’ foraging strategy, sluggish behaviour and limited
penetration into primary rainforest (James 2005). No individuals of this species were found in
the systematic 30-minute reptile searches around each roost tree located in this study, although
more recently a snake has been recorded at one of the maternity roosts. The previous lack of
records of Common Wolf Snakes from the southern section of the island led to the suggestion
that this species was unlikely to have caused the decline in this area (James 2005). Two
Common Wolf Snakes were recorded in this area during this study, although it is not known if
the species has been present for some time undetected, or whether these individuals represent
recent invasions. One of the snakes was a juvenile, suggesting there is a breeding population in
the area. Recent dietary analysis of Common Wolf Snakes (n = 138), caught primarily in
disturbed habitats, have not revealed any pipistrelles in their stomach contents (David James,
pers. comm.).
Predation and/or disturbance by the Giant Centipede Scolopendra morsitans
Giant Centipedes are believed to have been introduced to Christmas Island when it was first
settled. Andrews (1900) observed individuals arriving in shipments of coconut frond thatching,
and by 1907 it was abundant (Andrews 1909). It is currently widespread across the island and
extremely abundant (James 2005; Fig. 8).
Giant Centipedes are highly arboreal and were observed climbing trees and sheltering under
exfoliating bark on tree trunks. Therefore they could readily access pipistrelle roosts causing
either disturbance or direct injury from biting. They are very aggressive and their bite is
extremely painful to humans and has been recorded causing the paralysis of the leg of a
domestic duck (James 2005). A bite to a pipistrelle would likely be fatal. Non-flying young
left alone in the roost at night would be particularly vulnerable, as would individuals of all ages
if cornered in a roost without multiple escape routes. Adult bats roosting under loose bark
would, however, have a number of escape routes, and this may be a factor in their selection of
these roosts.
Little is known of the interaction between centipedes and bats, although there is a recent report
from Venezuela of centipedes preying on bats (Molinari et al. 2005). Observations were made
in a cave in Venezuela of the world’s largest centipede Scolopendra gigantea (maximum length
> 300 mm) preying on three species of bats considerably larger than themselves. On one
occasion a centipede was observed feeding on a freshly dead Leaf-chinned Bat Mormoops
megalophylla (Plate 28). This centipede was 145 mm long and weighed 15.2 g after feeding
for some time (it was estimated to have weighed approximately 9 g prior to feeding). The bat
was estimated to weigh 16.5 g. At the time the centipede and bat were collected, the centipede
had consumed approximately 35% of the bat’s body mass. The other observations were of a
210 mm centipede feeding on a 27 g Southern Long-nosed Bat Leptonycteris curasoae, and a
160 mm centipede feeding on a 10 g Davy’s Naked-backed Bat Pteronotus davyi. Although
the centipedes were not seen to catch and kill the bats, the authors were confident that these
observations represented predation rather than scavenging on carcasses. All bats were freshly
dead, previously healthy individuals, and it appeared the centipedes caught the bats while
crawling across the ceiling of the cave or by hanging from the ceiling and catching the bats in
flight. Centipedes can quickly immobilise their prey with venom while holding it securely with
their legs.
55
Fig. 8. The distribution of the Giant Centipede in 2004 recorded during reptile surveys
undertaken by the Christmas Island Biodiversity Monitoring Programme. This map is
reproduced from James (2005).
Although it is not known if the Giant Centipede on Christmas Island can, or does, prey on the
Christmas Island Pipistrelle, these observations of a con-generic species from Venezuela
suggest that predation by this species needs to be seriously considered. The Giant Centipedes
on Christmas Island are typically 150 mm long with some individuals observed up to 250 mm
(David James, pers. comm.). If a 145 mm Venezuelan centipede can catch and consume a
16.5 g bat, then it is likely that a 150 mm Christmas Island centipede could easily prey on a 4 g
pipistrelle.
The timing and pattern of introduction of the Giant Centipede to Christmas Island does not
correspond well with the decline of the pipistrelle. However, the centipede appears to have
become considerably more abundant in recent years (i.e. comparing general observations from
our studies in 1998 and 2005). Such an increase may potentially have resulted in increased
predation pressure on the pipistrelle.
56
Plate 28. A photograph from Venezuela of a giant centipede, Scolopendra gigantea,
holding and eating a freshly-killed Leaf-chinned Bat, Mormoops megalophylla, while
hanging from the ceiling in a cave (reproduced with permission from Molinari et al.
2005).
Predation and/or disturbance by the Yellow Crazy Ant Anoplolepis gracilipes
The Yellow Crazy Ant is a tramp species that has been recognised as among the top 100 of the
‘world’s worst’ invaders by the IUCN and the Global Invasive Species Database (O’Dowd
2002). It has been listed as a key threatening process under the EPBC Act and has been
recognised as a key threat to biodiversity on Christmas Island (Commonwealth of Australia
2002). It was accidentally introduced to the island some time between 1915 and 1934
(O’Dowd et al. 1999). These ants form multi-queened supercolonies in which the density of
ants is extremely high. Dramatic increases in supercolony formation began in the mid to late
1990s at several widespread locations. The effect of the supercolonies is that Yellow Crazy
Ants become the numerically dominant consumer on both the forest floor and in the canopy
(O’Dowd et al. 1999, 2003). Supercolonies range in size from several hectares to several
hundred hectares, and at the height of their infestation in 2002 occupied 28% of the total
rainforest area on Christmas Island (James 2005).
It is currently not known what impacts the Yellow Crazy Ant has had on the Christmas Island
Pipistrelle. However, evidence indicates that the continuing spread of the ant would have
deleterious consequences for the long-term viability of the species. The Yellow Crazy Ant has
been recorded preying on mammals elsewhere, such as newborn pigs, dogs, cats, rabbits and
57
rats (e.g. Lewis et al. 1976; Haines et al. 1994). The Christmas Island Pipistrelle is known to
be attacked and killed by the ant: one individual in a harp trap died as a result of Yellow Crazy
Ant attack in 1998 (Lumsden et al. 1999). Bats contacted by Yellow Crazy Ants that are not
killed directly are likely to suffer reduced fitness due to exposure from sprayed formic acid
leading to blindness and physiological stress (O’Dowd et al. 1999).
All the roosts located in 1998 and 2005 were in areas that were devoid of supercolonies at the
time, although some of these areas may have been infested in the intervening period. The
majority of roosts were situated under exfoliating bark on the trunks of trees. These roost
locations would be directly in the path of columns of ants travelling from nests on the ground to
the canopy where they forage (O’Dowd et al. 1999). Consequently, such roost sites are likely
to be readily accessed and investigated by Yellow Crazy Ants. Some roost sites may also be
potentially usurped by ants nesting in canopy or mid-strata tree hollows. Given the small size
of the pipistrelle, maternity sites located within supercolony areas, and in particular the nonflying young in these roosts, must be considered at risk. It is likely that in areas infested by
Yellow Crazy Ants, the Christmas Island Pipistrelle would be forced to select alternative
roosts, where available. Since Yellow Crazy Ants use dead trees less frequently than live trees
for both foraging and commuting to the canopy, this may be a factor in the use of dead trees as
roosts (David James, pers. comm.).
Secondary impacts as a result of the Yellow Crazy Ant proliferation and subsequent control are
unknown. It is possible other potential predators, such as the Giant Centipede and Black Rat,
have increased in number.
Although the proliferation of the Yellow Crazy Ant in recent years is likely to have had direct
and indirect effects on the pipistrelle, the ants are unlikely to be the primary cause of the
current decline, as the decline had already commenced before the Yellow Crazy Ants exploded
in numbers, and pipistrelles have disappeared from sections of the island (such as the central
plateau) where supercolonies never formed. Further, the stronghold of the pipistrelle in the
west of the island broadly corresponds with where the majority of the ant supercolonies
formed. An aerial baiting program led by the Crazy Ant Steering Committee and Parks
Australia North resulted in the destruction of supercolonies at all sites baited and led to a
reduction of numbers by 98% in 2002 (Green 2002; Kemp 2003). Since this time, however,
some ant populations have increased in numbers (David James, pers. comm.).
It is not known if any of the other species of introduced ants may be impacting on the status of
the Christmas Island Pipistrelle.
Predation by the Nankeen Kestrel Falco cenchroides
On mainland Australia, the Nankeen Kestrel preys primarily on terrestrial vertebrates, with bats
occasionally recorded as a dietary item (Lewis 1987; Marchant and Higgins 1993). Nankeen
Kestrels first arrived on Christmas Island in the 1950s and were initially only in low numbers in
the north-east section of the island (James 2005). They expanded their range and significantly
increased in abundance in the 1980s (H. Rumpff, cited in Lumsden et al. 1999). Although a
bird of grasslands and other open habitats on mainland Australia, on Christmas Island this
species is also widespread in areas of secondary rainforest regrowth. Although it is absent from
extensive tracts of primary rainforest, it is present along the edges and tracks through some
areas of primary rainforest, using these openings as foraging locations. In 1984, Tidemann
(1985) recorded pipistrelles hawking insects along roads and ecotones during the late
afternoon, up to an hour before sunset. Foraging by bats during daylight hours on islands
58
elsewhere in the world has been attributed to a lack of avian predators (Speakman 1995).
There appears to have been a shift in the time of first emergence over recent years, from bats at
times being seen up to 55 minutes prior to sunset in the mid-1980s, up to 19 minutes prior to
sunset in 1998, to exactly sunset in 2005. However, it is not known if this represents a real
temporal shift in foraging behaviour with emergence shifting to after sunset when predation
risk is lower, which may be the result of predation pressure from a diurnal raptor, such as the
Nankeen Kestrel. Alternatively, it may be due to differences in the season, weather or
reproductive condition of the females. However, this is considered unlikely as the time of the
first recorded bat call was consistent throughout the year during the extensive detector surveys
undertaken by PANCI in 2004-2006 (David James, pers. comm.).
The Nankeen Kestrel is widespread across the island, both in areas that the pipistrelle has
disappeared from and in areas where it is still occurs (Lumsden et al. 1999; James 2005). This
study has shown that kestrels prey on Glossy Swiftlets, the diurnal ecological equivalent to the
pipistrelle, and hence it is possible that they could also catch pipistrelles in flight. However, no
evidence was found of pipistrelles in prey remains of kestrels during this study. It is considered
unlikely that predation by this species is the primary cause of the decline, although the
possibility that it is a compounding factor cannot be ruled out, and requires further
investigation. If pipistrelles have altered their behaviour to emerge only after sunset to reduce
predation risk, there would now be very little overlap between the periods of activity of the
pipistrelle and the kestrel.
Predation by the introduced Black Rat Rattus rattus
This exotic species has been attributed with the extinction, or decline, of bats on islands
elsewhere in the world (e.g. Daniel and Williams 1984; Pryde et al. 2005), and is thought to be
a severe threat to native animals on Christmas Island (Commonwealth of Australia 2002). The
Black Rat was introduced when the island was first settled in the 1890s, and is now common
and widespread throughout the island. It occurs both in areas occupied and not occupied by the
pipistrelle. The Black Rat replaced the two species of endemic and now extinct rats (Maclear’s
Rat Rattus macleari and Bulldog Rat R. nativitatus). Maclear’s Rat, which was highly
arboreal, was extremely abundant at the time of settlement (Andrews 1900). Therefore, it
could be expected that the pipistrelle had evolved to co-exist with an arboreal rodent.
However, the impact of the Black Rat is unknown, and it is possible that it may be a
contributing factor in the decline of the pipistrelle. Since it is highly arboreal, it could be
preying on bats within their roosts. Several observations have been made using the infra-red
cameras of rats climbing pipistrelle roost trees (see Plate 20). Because it was not possible to
place the cameras at the roost entrances, it is not known whether the rats investigated or
interfered with roosting pipistrelles. Potential changes in the distribution and abundance of this
opportunistic rat, in response to altered food resources as a result of the impacts of the Yellow
Crazy Ant supercolonies on rainforest structure, may need to be considered.
Predation by the Feral Cat Felis catus
This introduced predator became established soon after settlement, and is now common and
widespread on the island. It is considered to pose a severe threat to native animals on
Christmas Island (Commonwealth of Australia 2002). Although dietary studies have not
revealed the Christmas Island Pipistrelle as a prey species (Tidemann et al. 1994; Corbett et al.
2003), it is possible that occasional individuals are captured given their low roosting and
foraging habits. However, the timing of introduction and pattern of distribution of this species
does not correspond with the decline of the pipistrelle, and so it is unlikely to be the primary
59
cause of decline. Feral Cats were observed to be common and widespread during this study,
both in areas occupied and unoccupied by the pipistrelle.
Predation by endemic predators
The Christmas Island Pipistrelle has not been recorded as a prey item of the Christmas Island
Goshawk Accipiter fasciatus natalis or Christmas Island Hawk-Owl Ninox natalis (Hill and Lill
1998; Hill 2004a, b). However, it is possible that both species may opportunistically prey on
the pipistrelle. The relationship between the pipistrelle and these potential natural predators is
unlikely to have altered recently, and hence they are not considered to be the cause of the recent
decline.
Disturbance to roost sites from Giant African Snails Achatina fulica
The abundance of the Giant African Snail has increased dramatically in recent years, at least in
part due to the explosion of Yellow Crazy Ants and the subsequent decline of Red Crabs.
Giant African Snails were frequently found on the trunks of trees under loose bark. It is not
known if this species may interfere with bats in their roosts through competition for space or by
rendering the roosts unsuitable due to secretions. No Giant African Snails were found within
the vicinity of maternity roosts, but it is not known if this finding is significant or unrelated.
The snails have a patchy distribution on the island (Fig. 9), and their distribution does not
correlate well with the pattern of decline of the pipistrelle, however, as they appear to be
expanding their range into the area used for roosting by the pipistrelles, further investigations
are required.
Fig. 9. The distribution of the Giant African Snail Achatina fulica in 2005, based on
island wide surveys (map courtesy of PANCI).
60
Habitat loss
The Christmas Island Pipistrelle is a rainforest-dependent species that requires primary
rainforest for roosting sites. The extensive clearfelling of primary rainforest for phosphate
mining has reduced the roosting habitat available for the species compared to that present at the
time of settlement. While opening up parts of the rainforest may have increased the area
available as foraging habitat, for most insectivorous bats, roosting habitat is generally more
restricted and limiting than foraging habitat. Hence it is expected that a population decline was
experienced by the species in the years of intensive clearing for phosphate mining.
Habitat loss is not, however, considered to be the cause of the recent decline in distribution and
abundance as there was no clearing of primary rainforest since the species started to decline
(clearing of primary rainforest ceased in 1987). However, any additional loss of habitat may
compound other factors that are impacting on the species and is likely to be more influential
now that the species has declined to a low population size.
Proposals currently under consideration to clear primary rainforest on vacant crown land may
provide additional pressure on the remaining Christmas Island Pipistrelle population and/or
reduce suitable habitat available for the long-term recovery of the species. In addition, the
removal of secondary regrowth during phosphate mining may adversely affect foraging
habitats.
Habitat alteration
In the 1960s drill lines were bulldozed across the island in parallel lines at 120 m intervals for
phosphate mining exploration. This resulted in the clearing of 354 separate lines with a total
length of 506 km (Lumsden et al. 1999). The Christmas Island Pipistrelle is an edge specialist
targeting forest ecotones and gaps within the rainforest canopy. In 1984, Tidemann (1985)
commonly observed bats flying along open drill lines. By the mid-1990s, the combination of
storm damage and the regeneration of vegetation along many of the drill lines resulted in the
loss of much of this temporary foraging niche. The loss of this habitat may have caused a local
reduction in population numbers. However, it does not account for the apparent abundance of
this bat at first settlement (e.g. Andrews 1900) or the westward contraction in range of the
pipistrelle.
Loss of roost sites
Although not likely to be the primary cause in the decline of this species, a factor identified
during this study that could now be having a serious impact on the remaining population, is the
loss of roost sites, in particular maternity roosts. Maternity roosts were found to be
predominantly under loose bark on dead T. acutangula, or similar, trees. Of the seven
maternity roosts located in December 2005, four of these trees have now collapsed and another
has lost all the loose bark off the tree. This has resulted in the loss, over a nine month period,
of five of the seven maternity roosts that were used by pipistrelles in December 2005 (i.e. as of
September 2006; David James pers. comm.). It is likely that the bats that had been using these
roosts shifted to nearby roosts (assuming they had not been killed in the tree fall). However, if
the loss of roosts continues at this rapid rate, the low availability of suitable roost sites could
become (if it is not already) a severely limiting factor.
The majority of the remaining individuals appear to be roosting in a small area in the west of
the island in The Dales (Fig. 4). Searches of this area revealed only low densities of dead trees
of the preferred roost tree species. The densities of potential roost trees were highest within the
61
immediate vicinity of the roost trees (i.e. within a 50 m radius) indicating the bats were
selecting areas that had high densities of potential roosts, presumably to facilitate roost
switching behaviour. Using roosts that are close together may be particularly important when
lactating females shift roosts and need to carry their young in flight. A similar pattern of
selecting areas with high densities of potential roosts has been found for other species of
microbats (e.g. Lumsden et al. 2002).
Many of the maternity roosts appeared to be at a similar stage of decay, suggesting that they
may have been killed in a single event, such as a cyclone, some years ago. It is currently not
clear why the female pipistrelles are choosing to roost under bark on dead trees rather than in
tree hollows in live trees, that would appear to offer more protection for the young and have a
much greater longevity. Often species of microbat that roost under loose bark in the nonbreeding season, shift to tree hollows to give birth to their young (Kunz and Lumsden 2003),
however this pattern is not followed by the Christmas Island Pipistrelle. It is possible that some
threatening processes are acting to make tree hollows less suitable, while not affecting (or
affecting to a lesser extent) roosts under bark. For example, if an introduced species, that could
cause predation or disturbance, entered a roost in a tree hole with a small entrance, the bats
would be trapped inside with no alternate escape route. However, when the bats roost under
lifting sheets of bark, there are multiple entry and exit points, and hence they have a much
greater chance of escaping a predator. Alternatively, it could be that tree hollows are now
being occupied by some other species which are excluding bats from using these roosts,. such
as Yellow Crazy Ants or feral bees.
Yellow Crazy Ant populations may have an influence on the availability of potential roost
trees. T. acutangula trees are one of the species targeted by scale insects and their Yellow
Crazy Ants mutualists would have contributed to a higher prevalence of dead trees (Mick
Jeffery, pers. comm.). The aerial baiting program for Yellow Crazy Ants in 2002 covered most
of the area used for roosting by the pipistrelle, and hand baiting has also occurred in The Dales
area every year since 2000. As a result Yellow Crazy Ants in The Dales area have not
subsequently achieved comparable pre-aerial baiting densities. Consequently scale insect
outbreaks have been more contained, resulting in less canopy dieback and tree death. This may
have implications for future 'recruitment' of dead trees for maternity roosting purposes.
Prey availability
Unknown factors may be altering the densities of prey available to the Christmas Island
Pipistrelle. Preliminary dietary studies have indicated a range of small flying invertebrates,
especially moths, beetles and flying ants, are taken as prey items (Lumsden and Cherry 1997;
James 2005). However, further investigations are required to determine whether the species is
an opportunistic feeder or shows dietary specialisation, and if this varies throughout the year.
Yellow Crazy Ant supercolonies have resulted in the localised reduction of invertebrate
diversity and abundance (James 2005). In addition, the baiting program to control the Yellow
Crazy Ants may have impacted on invertebrate availability. Alteration to flying insect numbers
may result in reduced breeding success of the pipistrelle, leading to a reduction in population
size. However, the distribution and timing of the ant explosions and subsequent control do not
match the pattern of decline of the pipistrelle. In addition, insect abundance remains high and
insectivorous birds are common across the island, suggesting that there has not been a collapse
in the food base (James 2005).
62
Climatic conditions
Cyclones have been documented to severely impact bats on islands (e.g. Craig et al. 1994;
Gannon and Willig 1994; Rodriquez-Duran and Vazquez 2001). A severe storm in March
1988 damaged significant areas of primary rainforest. The impact of this natural event on the
roosting and foraging areas of the pipistrelle is unknown.
The effects of drought, as experienced in recent years, on the Christmas Island Pipistrelle are
unknown. It is likely that such conditions restrict prey numbers and may influence the thermal
properties of roosts resulting in a population decline. Although forest fires are uncommon on
the island, during extended dry periods in 1994 and 1997, fires occurred in terrace rainforest.
The effects of forest fire on the Christmas Island Pipistrelle is unknown, but may result in
direct adverse impacts due to the loss of roost sites (particularly exfoliating bark on tree
trunks), and indirectly by affecting invertebrate populations.
Although altered climatic conditions may have some influence over population numbers, it is
unlikely that the rapid decline in numbers is due to this factor.
Vehicle-related mortality
The Christmas Island Pipistrelle commonly forages along roads from close to ground level to
above canopy height within and along the ecotone of primary rainforest and secondary
rainforest regrowth (Tidemann 1985; Lumsden and Cherry 1997; Lumsden et al. 1999). Small
rainforest bat species are known to be the victims of roadkills elsewhere (Schulz 2000), and
Tidemann (1985) reported a collision of a Christmas Island Pipistrelle with a vehicle. The
incidence of vehicle-related mortality (e.g. from night haulage trucks associated with phosphate
mining) is unknown, although no roadkilled pipistrelles were found during the monitoring of
wildlife mortalities along Murray and North West Point Roads from January 2004 to May 2006
by PANCI, including sections of which pass through the edge of pipistrelle foraging areas
(David James pers. comm.). Mortalities may, however, have gone undetected as bats killed
during the night may have been scavenged by crabs prior to dawn.
Although not considered a major cause of mortality, increased night-time traffic levels along
roadways may result in an increase in vehicle-related mortality, especially in the western
section of the island, due to the construction of the Immigration Reception and Processing
Centre and new phosphate mining operations in the pipistrelles’ main foraging area. If
population numbers were high, deaths due to vehicles would probably be inconsequential.
However, as numbers decrease, any additional deaths have a greater impact.
Disease
There was no obvious external sign of ill-health in the pipistrelles caught during our 1994, 1998
or 2005 studies. As discussed elsewhere in this report, the 52 individuals trapped in the current
study appeared to be in good condition. All had high body weights, there were no obvious
external signs of disease and the majority of the females were breeding. Of the biological
samples collected, all were normal, with the exception of the white blood cell counts. These
were lower than for other species of similar-sized microbats, however, the significance of this
finding is unknown. However, the possibility that the decline in the species may be due to a
more subtle cause of ill-health cannot be ruled out. It is possible that disease may be having a
significant impact on numbers without clinically ill individuals being observed. Such impacts
might be expressed through reduced survival of specific age groups, reduced numbers of young
being recruited into the breeding population, lower success of late pregnancies or reduced
63
reproductive lifespan. The possible leukopenia and regenerative anaemia found in this study
requires further consideration. Known causes of such conditions should be ruled out, for
example, leukopenic viruses and exposure to toxins such as lead.
Decreasing population size
Current evidence suggests that the Christmas Island Pipistrelle is declining rapidly in both
distribution and numbers. A small population size increases the risk of extinction through
inbreeding depression and stochastic events (Caughley and Sinclair 1994). Although the
pattern of decline and the current condition of the animals is not consistent with inbreeding
depression, this factor may play a role in the future as the population size continues to decline.
In addition, now that the population is confined to such a small area, stochastic events may play
a role in the final demise of the species.
Options for future management
There is a serious risk of extinction of the Christmas Island Pipistrelle in the near future. If the
rate of decline indicated in Fig. 1 continues, it is possible that the species will be extinct by
2008. To ensure the survival of the species urgent action is required now, using a range of
approaches. These actions need to be undertaken concurrently and implemented immediately,
rather than waiting until the cause of the decline is identified. Below we outline four
approaches: captive breeding, on-ground roost management, predator control, and further
investigations to determine the cause of the decline so that management actions can be more
targeted in the future. Although all actions need to be undertaken urgently, we believe the two
highest priorities at present are to establish a captive breeding program and to protect and
supplement roost sites. These measures alone can not ensure the long-term survival of the
species, however, they will provide some ‘breathing space’ in which to determine and address
the cause of the decline. We have listed advantages and disadvantages of each option as well
as an indication of the priority and feasibility of undertaking the proposed action.
Captive breeding
Background: The rapid and continuing decline of the Christmas Island Pipistrelle in recent
years, combined with a lack of direct evidence for the cause of this decline, dictates an urgent
need for the establishment of a captive breeding colony to prevent the imminent extinction of
the species. Such a colony would provide insurance against further decline in numbers, and a
source of animals to re-establish wild populations once the cause of the decline has been
identified and controlled. In addition, further aspects of the biology and health of the species
could be clarified from a captive colony.
There are two options for establishing a captive colony: using an existing wildlife facility on
the Australian mainland, or building and staffing a facility on Christmas Island.
Option 1: Establishing a captive colony in an existing wildlife facility on the Australian
mainland.
Advantages: An established facility would have appropriate staff, including experienced
animal keepers and veterinarians, and would have ready access to pathology and other services.
Such staff would be in a optimal position to maintain and monitor the health and well-being of
the animals. It is possible that existing enclosures could be modified to make them suitable for
the pipistrelle, thus significantly reducing building costs, or if new enclosures were required,
64
constructing them would be less expensive on the mainland than on Christmas Island. There
would also be greater access to artificial food supplies (mealworms and supplements).
Disadvantages: It would be more difficult and expensive to transport bats to a facility on the
mainland than it would be to one on Christmas Island. Due to the potential risk of disease in
the remaining population, animals brought to the mainland would initially need to be kept
under strict quarantine conditions. In addition, there is also the risk that animals brought to the
mainland might be exposed to pathogens and other factors that are not present on Christmas
Island.
Priority: Very high.
Feasibility: High.
Option 2: Building and staffing a facility on Christmas Island.
Advantages: Animals could be housed in the same climatic conditions as in the wild, and their
diet could be supplemented with naturally occurring insects. Wild individuals could be quickly
and easily transported to the facility.
Disadvantages: The lack of facilities and trained animal keepers and veterinarians would
require the building of a new facility and the staffing of this facility. This is likely to be very
expensive. In addition, the decline of the pipistrelle commenced in the north-east section of the
island, which is where it would logistically be easiest to establish the captive colony (i.e. in or
near the Settlement). If there is some, as yet unknown, environmental factor affecting the
species on the island, captive animals would continue to be exposed.
Priority: High.
Feasibility: Medium.
Establishing a captive colony is now one of the highest priority recovery action for this species
to enhance its survival and prevent its imminent extinction. For a range of reasons (staff,
facility, resources, cost) we believe that establishing this colony in an existing facility on the
Australian mainland would have the greatest chance of success. If animals were brought to the
mainland they would need to be located in an area with similar climatic conditions and day
length to Christmas Island, as these factors influence breeding success in captive colonies of
bats (Jackson 2003). We have had preliminary discussions with the Territory Wildlife Park in
Darwin, whose threatened species unit has successfully bred a range of threatened fauna
species for reintroduction back to the wild. They have expressed interest in being involved
with a captive breeding program for the Christmas Island Pipistrelle (subject to appropriate
funding being available; Dion Wedd, Curator, Territory Wildlife Park, pers. comm.). It is
likely that a plane would need to be chartered to transport the animals to the facility as there are
no direct commercial flights from Christmas Island to Darwin. Alternatively, it may be
possible to fly to Perth, hold the animals in a quarantine facility for several days to enable them
to feed and rest, and then fly to Darwin, however this is likely to have greater negative impacts
on the animals than a single, direct flight. A captive management plan would need to be
developed, to consider the techniques for captive management and breeding, transportation,
housing, diet and quarantine issues. It would also need to consider the number of individuals to
be taken from the wild to form the founding colony and their age, sex and reproductive
condition.
There are few examples of captive breeding colonies of microbats in Australia, with the
exception of the Ghost Bat Macroderma gigas (Jackson 2003). Phillips and Inwards (1985)
maintained a large breeding colony of Gould’s Long-eared Bats Nyctophilus gouldi in Canberra
65
for four years, with 33 females giving birth to young in captivity. Small numbers of nonbreeding bats can be readily kept in captivity for extended periods, for example, we have
maintained two male Eastern Freetail Bats Mormopterus sp. in captivity for 17 years, and a
number of other species for up to eight years (L. Lumsden, pers. obs.). Experience can also be
drawn from extensive microbat captive colonies in North America (Barnard 1995; Lollar and
Schmidt-French 1998). Bats can be readily transported in small cloth bags, that would need to
be held in containers maintaining appropriate temperature and humidity conditions.
Consideration may need to be given to establishing a captive colony of a related, nonthreatened species (e.g. a species of pipistrelle from the Northern Territory), so that appropriate
management protocols are established prior to bringing Christmas Island Pipistrelles into
captivity. However, due to the imminent extinction of the pipistrelle, there may not be time for
this.
On-ground roost management
1. Install artificial roost sites (bat boxes)
Background: The rapid collapse of dead trees providing maternity roosts and the generally low
availability of these trees, suggests that either now, or in the near future, there may be a
shortage of potential roost sites. This shortage may force bats to roost and raise young in less
optimal roosts, thus potentially affecting reproductive success and/or survival rates.
Establishing artificial roosts that provide a similar physical space and microclimate to loose
bark on dead trees may provide alternative roosts. Setting bat boxes on smooth metal poles
with preventative barriers at the base would provide predator-proof roost sites.
Advantages: Installing bat boxes would provide additional, alternate roosts that are not
accessible to tree-climbing potential predators.
Disadvantages: It is not known if pipistrelles will use bat boxes, and some experimentation
may be needed to design a box that is acceptable to the bats. To make a significant
contribution at a population level, a large number of boxes will need to be provided. It is not
known if all potential predators can be excluded.
Priority: High.
Feasibility: High. Parks Australia North has already commenced implementing this
recommendation, with 14 bat boxes installed on 6 m metal poles in May 2006 in Sydneys Dale
near existing maternity roosts (David James, pers. comm.). It is not known as yet if these
boxes are being used by pipistrelles, and regular monitoring of the boxes is required to
determine if this strategy is successful.
2. Placing preventive barriers around the bases of the remaining known maternity roost
trees.
Background: Since predation or disturbance at roosts is suspected as a factor in the decline of
the pipistrelle, an important action will be to protect existing maternity roosts from potential
predators or species causing disturbance in roosts (e.g. Giant Centipede, Black Rat, Yellow
Crazy Ants, Common Wolf Snake and Giant African Snail). Preventative barriers should be
installed at all remaining maternity roosts, including the roost that is not currently being used
(Roost 17). Investigations will need to be undertaken to determine the most effective way of
excluding all unwanted species, without impacting on the longevity of the roost tree. Options
include the application of sticky materials such as Tanglefoot, or the erection of physical
barriers such as a sheet of metal around the tree with the gap between the metal and the tree
filled with an impenetrable barrier such as silicone, or abrasive surfaces to deter Giant African
Snails. If adjacent trees have interconnecting branches these may also need to be treated.
66
Advantages: Will exclude potential predators from known roosts.
Disadvantages: It is not known if these barriers will be effective, and none have yet been
designed or field tested. It is unknown if these barriers may have a negative impact on the tree
or non-target species. In addition, barriers will not exclude potential predators (e.g. Giant
Centipede) that are actually living in the roost trees, as opposed to climbing up these trees from
the ground.
Priority: High.
Feasibility: High.
3. Search for more potential roost trees and establish protective barriers.
Background: It is highly likely that other dead trees with exfoliating bark, close to known
maternity roosts are also used as roost sites by pipistrelles. It is therefore recommended that
searches be made of the area surrounding known roosts and all similar-looking trees are treated
using the method outlined above.
Advantages: This will immediately protect more potential roost trees, without the cost and
time involved in identifying if they are currently being used as a roost. This action will enable
a greater number of potential roost trees to be protected, rathr than just protecting known
roosts.
Disadvantages: In addition to the disadvantages discussed above, by just protecting dead trees
with exfoliating bark this could bias the types of roosts that are protected.
Priority: High.
Feasibility: High.
4. Creating natural new roost habitat by selective killing live trees.
Background: The majority of maternity roosts were located under loose bark on dead T.
acutangula, or similar, trees. Searches revealed low densities of these potential roost trees.
Therefore, one option would be to selectively kill live T. acutangula trees, and other species
whose bark exfoliates in a similar pattern, to provide roosting habitat in the future.
Advantages: This would provide new potential roost trees replacing those that have collapsed.
Disadvantages: There would be a time lag between when the trees were killed and when the
bark lifts to form a suitable cavity. In addition, killing these trees may impact other threatened
fauna and the ecosystem as a whole.
Priority: Low (due to time lag).
Feasibility: Medium.
Predator control
1. Monitor and eradicate Yellow Crazy Ant supercolonies in The Dales area, from
Sydneys Dale to Martin Point.
Background: All currently known roosting sites are located in The Dales area from Sydneys
Dale to Martin Point. If new supercolonies of Yellow Crazy Ants formed in this area they
could present a serious threat to the remaining roosting colonies. Hence it is important that this
area is intensively monitored, especially within the vicinity of known roosts, to locate and
control any new supercolonies.
Advantages: This would eliminate the impact of Yellow Crazy Ant supercolonies on roost
sites.
67
Disadvantages: None, particularly as this could be incorporated into the existing Yellow Crazy
Ant control program.
Priority: High.
Feasibility: High.
2. Control of the Giant Centipede
Background: In light of recent information from Venezuela of a similar species of centipede
preying on bats considerably larger than the Christmas Island Pipistrelle, serious consideration
needs to be given to the potential threat posed by this species, and for the development of
localised control methods. Control efforts should be concentrated in the remaining roosting
areas in The Dales.
Advantages: This would eliminate or reduce the impact of potential predation or disturbance
by this species to roosting bats.
Disadvantages: There are no established control methods or programs for this species on the
island, and it is unknown if it would be feasible to control this abundant, arboreal, introduced
species.
Priority: High.
Feasibility: Low (except for protecting roost trees and bat boxes).
3. Control of the Black Rat
Background: Black Rats are known to prey on bats elsewhere in the world and could be
reducing survival rates of the Christmas Island Pipistrelle. Black Rats have been observed
climbing pipistrelle maternity roost trees. An eradication program for the whole island (such as
has been successfully undertaken on a number of New Zealand islands; Colin O’Donnell, pers.
comm.) is unlikely to be funded or feasible. However, investigations should be undertaken into
the feasibility of undertaking control programs in the key roosting area.
Advantages: Control programs, especially within The Dales region could eliminate or reduce
the predation threat from Black Rats.
Disadvantages: This would be difficult to achieve due to the environment and the potential
impact on non-target species.
Priority: High, particularly as with Yellow Crazy Ant management, rat numbers may have
increased, thereby resulting in a greater potential current threat.
Feasibility: Low (except for protecting roost trees and bat boxes).
4. Control of the Common Wolf Snake
Background: The timing of introduction and distribution pattern closely mirrors the decline in
the Christmas Island Pipistrelle. Therefore, although there is no direct evidence that this
species has played a role in the decline of the pipistrelle, this snake needs to continue to be
considered as potential threat until proven otherwise. It is suspected to climb trees as it is
known to occur in the ceilings of houses on the island, and has been observed climbing the base
of a maternity roost. Although there is debate about the ability of this snake to prey on the bat,
it is known to feed on mice in South-east Asia, and could be a threat to unprotected non-flying
young, or to adults trapped inside roosts with a single exit.
Advantages: Control of this introduced species will eliminate or reduce the threat to this and
other native species that may be impacted.
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Disadvantages: It is not known if this species is involved in the decline of the pipistrelle.
There are no established control methods available.
Priority: High, as there is good circumstantial evidence in terms of the spread of this snake and
the corresponding decline of the Christmas Island Pipistrelle.
Feasibility: Low (except for protecting roost trees and bat boxes).
5. Control of the Feral Cat
Background: Although cats are known to prey on microbats elsewhere, the Christmas Island
Pipistrelle has not been recorded as a prey item of cats on the island. Since cats have been on
Christmas Island since settlement this species is not likely to be the major cause of the recent
decline.
Advantages: Control would reduce or eliminate the predation risk from this species.
Disadvantages: It would be difficult to control or eliminate this species from the remaining
Christmas Island Pipistrelle areas.
Priority: Low.
Feasibility: Low (except for protecting roost trees and bat boxes).
6. Control of the Giant African Snail
Background: Giant African Snails have become abundant in recent years. No snails were
observed in the vicinity of maternity roosts, however it is not known if this finding is
significant or coincidental. It is possible that this species may have a negative impact on the
roosting environment.
Advantages: Control would reduce any potential threat.
Disadvantages: There are no control programs in place on the island, and it is not known if it
would be feasible to control this introduced species. Its semi-arboreal nature increases the
difficulty for control methods.
Priority: Low.
Feasibility: Low (except protecting roost trees and bat boxes).
7. Control of the Nankeen Kestrel
Background: The shift in timing of first emergence from 55 minutes prior to sunset in the mid1980s to sunset in 2005 has led to the suggestion that the pipistrelles have altered their
behaviour to reduce predation risk from this self-introduced species. Evidence that Nankeen
Kestrels prey on the Glossy Swiftlets suggests that this species is capable of also catching
pipistrelles in flight, although no evidence of pipistrelles were found in kestrel feeding remains.
Advantages: A control program in the western section of the island would eliminate or reduce
the expanding population of Nankeen Kestrels, and thus reduce the threat to the pipistrelle.
Disadvantages: No control programs are currently in place on island, and it may not be
socially acceptable to reduce populations of this native raptor, especially since there is
uncertainty as to whether it is a factor in the decline of the pipistrelle.
Priority: Medium.
Feasibility: High.
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Further investigations to determine cause of decline
1. Continue monitoring distribution and abundance.
Background: Monitoring of the distribution and abundance of the Christmas Island Pipistrelle
has been conducted at established monitoring sites since 1994. The intensity and extent of this
monitoring has increased in recent years as part of the Christmas Island Biodiversity
Monitoring Programme. It is due to this long-term monitoring that we are aware of the rapid
decline in abundance and distribution of the pipistrelle. Further monitoring is critical to
recognise continuing declines and the distribution and abundance of the remaining population.
Advantages: Continuing documentation of population trends.
Disadvantages: None. Note that additional resources will need to be provided to PANCI to
continue undertaking this monitoring.
Priority: High.
Feasibility: High.
2. Monitor known roosts with remote cameras to provide direct evidence of threats.
Background: Four infra-red cameras are currently set at the bases of roost trees.
Advantages: Photos from these cameras may provide direct evidence of threats to roosts,
including potential threats not currently identified.
Disadvantages: None. Note that additional resources will need to be provided to PANCI to
undertake the regular maintenance and downloading of data from the cameras.
Priority: High.
Feasibility: High.
3. Locate more maternity roosts to increase the level of protection of roosts.
Background: Since most of the maternity roosts located in December 2005 have since
collapsed, it is important to undertake more studies to locate new roosts. In addition to locating
roosts by radiotracking individuals, it may be possible to use a thermal imaging camera to
locate roost sites by scanning likely trees and observing where heat sources are located.
Advantages: This will increase our knowledge of the roosts used by pipistrelles, and will
enable more roosts to be protected from potential predators by using tree guards and the placing
of bat boxes nearby.
Disadvantages: None.
Priority: High.
Feasibility: High.
4. Collection of data on population dynamics.
Background: It is not known which life cycle stage of the pipistrelles (i.e. dependent young,
recently independent young, non-breeding adults or breeding adults) is under the greatest threat
and is leading to the decline of the species.
Advantages: The collection of data on survivorship and population recruitment would help to
determine the main threats to the species and would enable targeted management actions.
Disadvantages: Some aspects of population dynamics (e.g. long-term survival rates) could
only be determined through long-term studies, and due to the rapid decline and imminent
extinction of this species there is little time available to undertake such a study. However,
70
valuable information could be gathered by undertaking a short-term study during the period
from female pregnancy until juveniles become independent.
Priority: Medium.
Feasibility: Medium.
5. Further investigations into the health of the population.
Background: The current study on the health of the population revealed all aspects that could
be examined were normal, with the exception of the low white blood cell counts and possible
regenerative anaemia. Further investigations are required to determine if these are typical for
this species or represent ill-health in the population. In addition, many other tests that would
have been useful to conduct, for example a blood biochemical profile and selected organ
biopsy, could not be undertaken due to the difficulty in getting adequate samples from such
small animals, and the decision not to sacrifice animals for internal investigations.
Advantages: Further research may determine if disease is a factor in the decline of the species.
This would influence the direction and priorities of recovery actions. Known causes of
suspected abnormalities such as regenerative anaemia should be investigated, e.g. exposure to
lead.
Disadvantages: It will be difficult to obtain sufficient material for analysis without taking
specimens.
Priority: Medium.
Feasibility: High for assessing environmental toxins, low for assessments based on biological
samples from individuals due to the difficulty of obtaining large enough samples for analysis.
6. Experimentally test for impact of potential threats using captive individuals located on
Christmas Island.
Background: To date it has not been possible to determine the cause of the decline of the
pipistrelle by using observational techniques. It may therefore be necessary to experimentally
test for the impact of potential threats using captive individuals of both potential predators and
possibly pipistrelles. This would need to be undertaken on the island to allow for easy
collection and testing of potential predators. It may be possible to use surrogates for
pipistrelles in predation trials, for example using pipistrelle faeces to provide a smell stimulus
and tape recordings of their social calls for an aural stimulus. Key species that should be tested
in this way are the Giant Centipede, Common Wolf Snake and Giant African Snail.
Advantages: This approach may provide the required information to determine the key threats
to the species and therefore enable targeted management.
Disadvantages: A short-term holding facility would need to be established and maintained on
the island. It may be difficult to exclude all extraneous factors, and to interpret the findings.
Priority: High.
Feasibility: Medium.
7. Determine potential impact of the Common Wolf Snake through radio telemetry.
Background: To determine if the Common Wolf Snake is a significant factor in the decline of
the pipistrelle, a detailed study of the snake may be required. Radiotracking wild individuals
would help determine their movement and activity patterns, climbing ability and prey taken.
Advantages: Such a study would help determine whether this snake is a significant threat to
the pipistrelle, and hence enable targeted management.
71
Disadvantages: Time involved; difficulty of implanting transmitters in a small snake; and
difficulty of directly relating information obtained to potential impact on the Christmas Island
Pipistrelle.
Priority: High.
Feasibility: Medium.
72
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76
Appendices
Appendix 1. Sites sampled using bat detectors and the number of Christmas Island Pipistrelle calls recorded. The time of
all calls are given for sites with less than 15 calls.
77
Date
Location
Grid Reference
14-Dec-05
14-Dec-05
14-Dec-05
15-Dec-05
15-Dec-05
15-Dec-05
16-Dec-05
16-Dec-05
16-Dec-05
17-Dec-05
17-Dec-05
17-Dec-05
18-Dec-05
18-Dec-05
18-Dec-05
19-Dec-05
Bulldozed lines to west of Winifred Beach Tk
Bulldozed lines to west of Winifred Beach Tk
Bulldozed lines to west of Winifred Beach Tk
Tk to Rehab S22
Tk to Rehab S22
Tk to Rehab S22
Tk that old Site 34 on - off rd to Blowholes
Tk that old Site 34 on - off rd to Blowholes
Tk that old Site 34 on - off rd to Blowholes
Tk that old Site 34 on - off rd to Blowholes
Tk that old Site 34 on - off rd to Blowholes
Tk that old Site 34 on - off rd to Blowholes
E-W Baseline 0.9km SE from jnct Murray Rd
E-W Baseline 1.0km SE from jnct Murray Rd
E-W Baseline 1.7km SE from jnct Murray Rd
near old Site 7 at start of Dales Tk
562740
562711
562645
567400
567342
567204
569980
569660
570241
569352
570241
569980
565940
566045
566636
562552
19-Dec-05
20-Dec-05
20-Dec-05
20-Dec-05
21-Dec-05
21-Dec-05
21-Dec-05
22-Dec-05
22-Dec-05
near old Site 7 at start of Dales Tk
Tk to Rehab S22
Tk to Rehab S22
Tk to Rehab S22
Tk to Rehab S22
Tk to Rehab S22
Tk to Rehab S22
Circuit Tk new rehab area
Circuit Tk new rehab area
562421
567204
567342
567202
567260
567020
566887
566456
566680
No. calls
Calls start
Calls end Time of calls
8841707
8841638
8841744
8840292
8840226
8840016
8838545
8838783
8838501
8839005
8838501
8838545
8841209
8841203
8840994
8841968
393
432
130
0
0
4
0
0
0
0
0
0
0
0
0
14
1850
1852
1853
2319
0026
2032
1901
1914
1901, 1910, 1913, 1914
2017
2201
2017, 2018x2, 2019, 2127, 2133, 2158,
2159x4, 2200, 2201
8842081
8840016
8840226
8839894
8839864
8839791
8839763
8840446
8840435
0
1
0
5
0
0
0
1
1
1905
1906
1908
0345
1905
2249
1906, 2248x2, 2249x2
1908
0345
77
Date
Location
22-Dec-05
23-Dec-05
23-Dec-05
23-Dec-05
24-Dec-05
24-Dec-05
24-Dec-05
25-Dec-05
25-Dec-05
25-Dec-05
26-Dec-05
26-Dec-05
26-Dec-05
27-Dec-05
27-Dec-05
27-Dec-05
28-Dec-05
28-Dec-05
28-Dec-05
29-Dec-05
29-Dec-05
29-Dec-05
30-Dec-05
30-Dec-05
30-Dec-05
31-Dec-05
31-Dec-05
31-Dec-05
Circuit Tk new rehab area
Tk from EW Baseline to Murray Rd
Tk from EW Baseline to Murray Rd
Tk from EW Baseline to Murray Rd
South Point East Quarry Area
South Point East Quarry Area
South Point East Quarry Area
South Point Wharton Hill Area
South Point Wharton Hill Area
South Point Wharton Hill Area
Rehab area west of S22
Rehab area west of S22
Rehab area west of S22
LB4 area below lookout
LB4 area behind shrine
LB4 area off Murray Rd
South Point Chinese Temple
South Point Chinese Temple
South Point Chinese Temple
The Dales, 2WD carpark
The Dales, Hughs Dale walking tk
The Dales Martin Pt carpark
Further south in Rehab 22S
Further south in Rehab 22S
Further south in Rehab 22S
Bulldozed lines west of Winifred Beach Tk
Bulldozed lines west of Winifred Beach Tk
Winifred Beach Tk
Grid Reference
566472
568262
567995
567815
572136
571890
571629
571309
571075
570916
566929
567199
567551
565810
565587
566085
570679
570764
570636
561906
561360
561157
567207
566772
566614
562740
562711
562720
8840542
8840858
8841016
8841128
8833379
8833254
8833291
8834620
8834486
8833835
8841112
8841307
8841321
8841648
8841700
8841936
8832658
8832487
8833104
8841741
8841931
8842732
8839902
8839539
8839400
8841707
8841638
8841544
No. calls
Calls start
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
6
6
0
0
1589
1535
134
1914
Calls end Time of calls
1921
1914, 1915, 1921
0210
1904
0216
2215
0210, 0211x2, 0215, 0216x2
1904, 1905, 1928, 2143, 2150, 2215
1859
1902
1853
0420
0338
2356
0359
78
78
Appendix 2. The biological samples collected from the trapped Christmas
Island Pipistrelles. Swabs: R – respiratory swab, G – genital swab.
ID No.
Reproductive
status of females
♀A
♀B
♀C
♀D
♀E
♀F
♀AB
♀AC
♀AD
♀AE
♀AF
♀BC
♀BD
♀BE
♀BF
♀CD
♀CE
♀CF
♀DE
♀DF
♀EF
♀ABC
♀ABD
♀ABE
♀ABF
♀ACD
♀ACE
♀ACF
♀ADE
lactating
lactating
pregnant
lactating
pregnant
lactating
pregnant
lactating
non-breeding
pregnant
pregnant
lactating
non-breeding
lactating
lactating
lactating
pregnant
lactating
non-breeding
lactating
lactating
non-breeding
lactating
lactating
lactating
lactating
non-breeding
lactating
lactating
4.6
4.4
5.6
4.6
5.9
4.6
5.4
5.1
3.7
5.0
5.8
4.1
4.4
4.0
4.7
3.7
5.3
4.2
4.1
4.6
4.1
4.0
4.0
4.1
4.4
4.1
4.1
4.3
4.2
♀ADF
♀AEF
♀BCD
♀BCE
♀BCF
♀BDE
♀BDF
♀BEF
♀CDE
♂A
♂B
♂C
♂D
non-breeding
non-breeding
lactating
non-breeding
lactating
lactating
lactating
non-breeding
lactating
–
–
–
–
4.3
4.3
4.4
4.3
4.3
4.3
3.9
4.0
4.2
4.0
3.4
3.9
3.7
Weight
(g)
Blood
sample
+
+
Swab
G
R&G
G
R&G
G
G
G
G
R&G
R
R
Faecal
sample
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
G
wing
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
G
G
R&G
R
R
G
+
+
+
+
+
+
+
+
+
+
+
External
parasites
Transmitter
attached
5 mites
2 mites
nil
nil
nil
4 mites
nil
3 mites
nil
4 mites
nil
nil
nil
1 mite
nil
nil
nil
5 mites
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
+
5 mites
nil
nil
nil
nil
nil
nil
nil
nil
nil
nil
2 mites
nil
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
79
ID No.
Reproductive
status of females
♂E
♂F
♂AB
♂AC
♂AD
♂AE
♂BC
♂BD
♂BE
♂BF
–
–
–
–
–
–
–
–
–
–
Weight
(g)
4.0
4.1
3.8
3.1
3.8
3.6
3.9
3.9
3.6
4.2
Blood
sample
Swab
Faecal
sample
+
+
G
+
G
+
+
+
+
+
+
+
External
parasites
Transmitter
attached
nil
nil
nil
nil
nil
nil
nil
nil
nil
3 mites
+
+
80
Appendix 3. Blood count parameters from blood smears collected from 31 Christmas Island Pipistrelles. Explanations of the
various parameters are provided at the end of the table.
Sample
No.
White blood cell characteristics
WBC Neutro- Lymph- Mono- Eosinoestimate phils
ocytes
cytes
phils
Basophils
Total
WBC for
differential
81
1
2
3
1.5
1.5
1
40
37
7
49
53
84
9
8
6
1
0
2
1
2
1
140
137
107
4
5
6
7
8
9
10
11
1.5
1
2
2
1.5
2
<1
1.5
42
27
43
29
23
24
31
39
56
49
47
65
69
61
56
49
2
14
6
2
5
4
5
10
0
0
3
4
3
7
2
2
0
10
1
0
0
4
6
0
142
127
143
129
123
124
131
139
12
13
14
15
16
17
18
19
<1
1.5
2
1.5
1.5
32
4
32
9
13
58
82
59
77
80
6
7
4
8
7
0
4
1
1
0
1
3
4
5
0
129
104
132
109
113
2
2
21
51
59
33
15
12
1
1
4
3
121
151
20
21
1.5
1.5
35
16
56
66
3
17
1
0
5
1
135
116
Red blood cells
Platelets
Parasites Comments
OK
polychromasia +
2 NRBC
polychromasia ++
polychromasia +
polychromasia +
polychromasia +
1 NRBC
polychromasia +
polychromasia ++
polychromasia +
polychromasia ++
1 NRBC /100 wbc
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
OK
OK
OK
nil
nil
nil
OK
OK
OK
OK
OK
OK
OK
OK
nil
nil
nil
nil
nil
nil
nil
nil
OK
OK
OK
OK
OK
nil
nil
nil
nil
nil
limited amount of blood in smear
slightly less anaemic
limited amount of blood in smear
2 NRBC
polychromasia +
polychromasia +
polychromasia +
OK
nil
nil
OK
OK
nil
nil
slightly less anaemic than some
81
Sample
No.
22
White blood cell characteristics
WBC Neutro- Lymph- Mono- Eosinoestimate phils
ocytes
cytes
phils
1.5
14
75
7
1
Basophils
Total
WBC for
differential
3
114
Red blood cells
Platelets
polychromasia +
OK
Parasites Comments
nil
23
24
25
26
27
1
<1
21
7
68
12
5
1
1
1
1
1
117
29
polychromasia +
polychromasia +
OK
OK
nil
nil
28
<1
2
14
6
2
1
27
polychromasia +
OK
nil
29
<1
4
3
0
0
0
11
polychromasia +
OK
nil
30
<1
5
7
3
0
0
20
polychromasia +
OK
nil
31
1
6
84
7
1
2
106
polychromasia +
OK
nil
limited amount of blood in smear
- cells lysed
limited amount of blood in smear
- cells lysed
limited amount of blood in smear
- cells lysed
limited amount of blood in smear
limited amount of blood in smear
but more markedly leukopaenic
than others
limited amount of blood in smear
but slightly more leukopaenic than
others
limited amount of blood in smear
but more markedly leukopaenic
than others
limited amount of blood in smear
but more markedly leukopaenic
than others
82
Explanation of the blood parameters is taken from the Encyclopedia of Surgery: A Guide for Patients and Caregivers.
http://www.surgeryencyclopedia.com/Ce-Fi/Complete-Blood-Count.html. The types of white blood cells are:
• Neutrophils are phagocytic cells (i.e. able to engulf objects) and aid in destroying bacteria and other ingested cells.
• Lymphocytes are responsible for initiating and regulating the immune response by the production of antibodies.
• Monocytes process and present antigens to lymphocytes.
• Eosinophils are increased in allergic reactions and parasitic infections.
• Basophils mediate the allergic response by releasing histamine.
82
Appendix 4. The blood parameters of Little Forest Bat Vespadelus vulturnus,
Southern Forest Bat V. regulus and Large Forest Bat V. darlingtoni, from
Healesville, Victoria.
Species
Little Forest Bat
Little Forest Bat
Little Forest Bat
Little Forest Bat
Little Forest Bat
Little Forest Bat
Little Forest Bat
Little Forest Bat
Little Forest Bat
Little Forest Bat
Little Forest Bat
Southern Forest Bat
Large Forest Bat
Large Forest Bat
Large Forest Bat
Large Forest Bat
WBC
estimate
2.5
3
3
3
3
2.5
3
4
5
2
4
3
2
4
3.5
3
Neutro- Lymphophils
cytes
10
22
36
20
14
53
29
28
21
5
27
19
30
35
40
17
70
70
49
77
77
43
68
66
74
80
61
79
50
51
56
70
Monocytes
20
8
15
3
9
4
3
2
3
15
11
1
20
7
1
13
Eosinophils
4
1
Basophils
1
1
1
2
7
1
Red blood cells
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
polychromasia +
83
Appendix 5. The fate of the Christmas Island Pipistrelle roost trees located in
1998 during the Lumsden et al. (1999) study.
Roost
No.
Grid reference
Tree species
Dead/
Live in
1998
Condition in 2005
1
0562167
8840636
Tristiropsis
acutangula
Dead
Found on ground – looks like had been
on ground for some time.
2
0562232
8840594
Tristiropsis
acutangula
Dead
Found on ground – looks like had been
on ground for some time.
3
–
–
Tristiropsis
acutangula
Dead
Not found
4
0562181
8840524
Tristiropsis
acutangula
Dead
Found location of where tree had been
but could not find remains of tree –
definitely not still standing.
5
–
–
Not known
Dead
Not found
6
–
–
Syzygium
nervosum
Live
Appeared identical to 1998
7
0562276
8840563
Tristiropsis
acutangula
Dead
In middle of pandanus patch – no
standing trees so assume has fallen but
could not find remains. GPS reading
approximate.
8
–
–
Arenga listeri
Live
Not possible to get accurate GPS
reading due to canopy coverage, but
approx. 20 m from Roost 8. Tree has
fallen over but is suspended in other
trees – area where roost was is still
present.
9
0561956
8840658
Strangler fig
surrounding
large tree
Live
Appeared identical to 1998
10
0561917
8840607
Arenga listeri
Live
Tree still standing and containing loose
fronds similar to in 1998 (note: GPS
reading is approximate as could not get
a signal right next to tree).
11
–
–
Pandanus sp.
Live
Not found
84
Appendix 6. Prey items identified from remains found at Nankeen Kestrel feeding sites. The number of individual grasshoppers is
based on the number of pairs of legs found; the number of Coleoptera/Lepidoptera is based on the number of pairs of elytra found unless more intact
individuals were located. No assessment could be made of the number of individuals of Glossy Swiftlets as all remains were just feathers.
No. Locality
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Site Type
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
Field 25
Rock outcrop
NE Point
Tree roost
Phosphate
Power pole roost
Hill Rd
Phosphate
Power pole roost
Hill Rd
Vagabond Rd Road sign roost
ML138
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Field 26
Rock outcrop
Grid Reference
Date
Volanga
irregularis
*563196
*563207
*563188
*563209
*563176
*563184
*563181
*563163
*563243
*563204
*563186
*563186
*563204
*563237
576454
574760
8841614
8841604
8841606
8841664
8841572
8841578
8841545
8841526
8841536
8841532
8841520
8841508
8841508
8841474
8848825
8845401
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
14/12/05
18/12/05
18/12/05
15
6
31
49
113
72
65
73
46
81
32
6
29
23
12
10
574481
8845480
18/12/05
575051
562353
562344
562345
562361
562391
562408
562373
562363
562355
562317
562326
562330
8846621
8842991
8842168
8842168
8842211
8842212
8842212
8842240
8842259
8842281
8842279
8842295
8842314
28/12/05
18/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
Other
Chrysodema Beetles ** Unidentified Meadow Argus Lygosoma Glossy
Orthoptera
simplex
Coleoptera Blattodea
Lepidoptera bowringii Swiftlet
1
1
1
9
1
-
-
+
+
+
-
18
1 (dark
brown legs)
-
-
-
-
-
-
-
3
142
7
5
4
10
5
12
2
6
14
7
18
-
1
1
1
-
-
-
-
+
85
85
No. Locality
86
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
Field 26
Field 26
Field 26
Field 26
Field 26
Field 26
Field 26
Field 26
Field 26
Field 26
Field 26
Field 26
Field 26
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Site Type
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Dirt mound
Dirt mound
Dirt mound
Dirt mound
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Grid Reference
562304
562250
562272
562261
562244
562211
562207
562202
562162
562348
562461
562478
562437
563629
563601
563618
563597
563622
563590
563570
563609
563650
563647
563722
563714
563713
563721
563740
563761
563762
563444
563505
563495
563510
563570
563499
563506
8842346
8842324
8842293
8842290
8842306
8842310
8842324
8842329
8842404
8842028
8841972
8841968
8841973
8841876
8841875
8841865
8841877
8841836
8841826
8841812
8841806
8841816
8841846
8841797
8841798
8841828
8841834
8841846
8841793
8841798
8841711
8841580
8841573
8841553
8841582
8841630
8841640
Date
Volanga
irregularis
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
22/12/05
1/01/06
1/01/06
1/01/06
1/01/06
1/01/06
1/01/06
1/01/06
16
4
16
12
23
5
10
5
11
61
36
14
27
36
6
4
15
6
3
4
9
2
5
9
35
2
2
2
53
8
2
5
3
2
52
8
2
Other
Chrysodema Beetles ** Unidentified Meadow Argus Lygosoma Glossy
Orthoptera
simplex
Coleoptera Blattodea
Lepidoptera bowringii Swiftlet
-
1
2
4
3
2
1
1
-
1
-
-
1
1
2
2
1
-
1
1
-
+
+
+
+
86
No. Locality
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
87
85
86
87
88
89
90
91
92
93
94
95
96
97
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Lily Beach
Rd
Lily Beach
Rd
Lily Beach
Rd
Quarry, W of
Quarry Rd
Quarry, W of
Quarry Rd
Quarry, W of
Quarry Rd
Quarry, E of
Quarry Rd
E of Airport
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Field 25
Site Type
Grid Reference
Date
Volanga
irregularis
Other
Chrysodema Beetles ** Unidentified Meadow Argus Lygosoma Glossy
Orthoptera
simplex
Coleoptera Blattodea
Lepidoptera bowringii Swiftlet
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Signpost
563654
563696
563621
563614
563609
563609
563612
563598
563564
563573
575352
8841608
8841606
8841629
8841629
8841638
8841652
8841686
8841693
8841647
8841646
8846082
1/01/06
1/01/06
1/01/06
1/01/06
1/01/06
1/01/06
1/01/06
1/01/06
1/01/06
1/01/06
2/01/06
10
94
79
5
10
2
112
17
94
49
12
-
2
2
2
1
-
1
-
1
1
1
-
+
-
Signpost
575414
8846149
2/01/06
4
1
-
-
-
-
-
-
Dirt mound
575726
8846482
2/01/06
6
-
-
-
-
-
-
-
Dirt mound
575655
8846482
2/01/06
4
-
1
-
-
-
-
-
Dirt mound
575655
8846460
2/01/06
31
-
-
-
-
-
-
-
Dirt mound
575787
8846577
2/01/06
4
-
-
-
-
-
-
-
Dirt mound
576027
8847260
2/01/06
5
-
-
-
-
-
-
-
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
576156
563657
563646
563590
563583
563572
563542
563524
563544
563583
563590
563595
563601
8844137
8841771
8841733
8841740
8841724
8841738
8841734
8841729
8841772
8841780
8841780
8841772
8841770
2/01/06
2/01/06
2/01/06
2/01/06
2/01/06
2/01/06
2/01/06
2/01/06
2/01/06
2/01/06
2/01/06
2/01/06
2/01/06
17
8
47
14
10
2
4
3
7
2
9
2
11
-
1
-
-
-
-
-
87
No. Locality
98
99
100
101
Field 25
Field 25
Field 25
Field 25
Site Type
Rock outcrop
Rock outcrop
Rock outcrop
Rock outcrop
Grid Reference
563628
563704
563563
563579
8841785
8841774
8841537
8841538
Date
Volanga
irregularis
2/01/06
2/01/06
2/01/06
2/01/06
55
4
4
7
Other
Chrysodema Beetles ** Unidentified Meadow Argus Lygosoma Glossy
Orthoptera
simplex
Coleoptera Blattodea
Lepidoptera bowringii Swiftlet
-
1
3
-
-
-
-
+
* The grid references for the first 14 feeding sites is provided in AGD66.
** Beetles were predominantly Click Beetles (Elateridae).
88
88