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Appendix ES-9 HTSCL Annual Report 2014
Hawaiian Tree Snail Conservation Laboratory
PI: Brenden Holland
2014 Annual Report
TREE SNAIL PROPAGATION SUMMARY
The UH Tree Snail Conservation Lab currently houses and cares for snails in 10
endemic Hawaiian achatinelline species, all of which are listed as federally endangered.
The tree snails are housed in 28 cages maintained in four environmental chambers.
Conditions in chambers are intended to mimic natural conditions of mid-elevation
Hawaiian rain forest. Chambers have temperature and light control, on a 12 hour cycle.
Temperatures are held at 20 or 21°C for during daylight, and 16°C during the night.
Sprinkler timers are set to water cages each 8 hours, 6 days per week. There has
historically been a one day no water period, again to try to mimic natural conditions.
Tasks for lab staff include weekly scheduled cage changes, removal of old leaves
and branches and replacing with fresh leaves of native tree and plant species. We also
count births, measure newborn snails and remove, measure and preserve any dead
individuals, and note percent cultured fungus consumed.
Following removal of old leaves, cages are cleaned with hot water and detergent,
sterilized with ethanol, air-dried, and snails are replaced along with fresh foliage.
Members of our group hike Oahu trails weekly to collect fresh leaves, providing food for
the snails in the form of surface growing arboreal fungus from leaves and tree bark.
In addition culture medium is autoclaved weekly, and 60 plates are poured and
inoculated with lab fungus stock. Cultured fungus has been used as a dietary supplement
in the lab for a number of years.
Pulsing (Rotation)/Release of Achatinella
In consultation with the Oahu Army Natural Resources Program (OANRP), the
DLNR Snail Extinction Prevention Program (SEPP) and USFWS staff, we are waiting
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Appendix ES-9 HTSCL Annual Report 2014
for permission for releases of Achatinella mustelina populations brought in to the rotation
system trial in 2013. In the past the main role of this facility has been on tree snail
populations that were experiencing steep declines due usually to sudden increases in
predation pressure, usually due to Euglandina rosea and other predators moving into the
area. This is still the case: we will continue to make space available for endangered tree
snails on an emergency basis. However in light of the fact that recent experience has
shown that over the long-term in captivity, populations of tree snails can undergo
population fluctuations, the reasons for losses are difficult to understand, therefore are
challenging to control. For these reasons we are more careful perhaps than in the past
about bringing in a population without an exit strategy in place, for release/return to a
safe, predator-controlled field locality.
Since 2012 we have begun to identify lab populations that can be released into
their natural habitat on a case-by-case basis, and only where targeted, successful predator
control has been conducted, or predatory activity is low has ongoing monitoring. These
cases also have only been conducted after careful discussion and consensus of
appropriate parties (OANRP, SEPP, USFWS), and always under USFWS permit. There
are two main avenues for this scenario, one being release of snails into predator exclosure
structures, and the other is release at sites where rat control has been successful and
Euglandina and Jackson’s chameleon activity has not been observed. Examples include
the success at Puu Hapapa, where sudden drastic declines were observed, and A.
mustelina were brought in to captivity at the HTSCL, numbers increased, meanwhile
funding was obtained, barriers were tested, the site was prepared via native plant
restoration and weed and predator removal. A state of the art predator exclusion structure
was completed and 341 captive endangered snails were released into this protective
structure in early 2012, and this stands as one of the most remarkable accomplishments in
the history of Hawaiian tree snail conservation. One of the main strengths of this effort is
the long-term safety of not only the rare achatinelline tree snails that were initially placed
inside, but ongoing additions of this species as well as more than a half dozen others,
some extremely rare, as well as the opportunity to preserve and protect a small ecosystem
including rare plants, insects, spiders and even birds.
Another recent example of a laboratory release of endangered tree snails occurred
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during summer of 2013 when SEPP staff observed devastating impacts of rats on an A.
concavospira population. Tree snails were collected and brought into the HTSCL, kept
for 19 days, and then they were released inside of the Palikea snail enclosure, with one
additional snail included in the release due to a birth in captivity.
Table 1. Current population status summary for Achatinella mustelina.
Population
Number
Ekahanui
17: 17 juvenile
Makaha
2: 1 juvenile / 1 adult
East Makaleha
8: 6 juvenile / 2 adult
Schofield West
8: 6 juvenile / 2 adult
Peacock Flats
4: 1 juvenile / 3 adults
Bornhorst
2: 1 juvenile / 1 adult
Palikea
3: 3 adult
Publications
Since the previous Annual Report my staff, students, colleagues and I have
published the following three manuscripts based on OANRP funded research accepted
for publication in peer-reviewed scientific journals:
•
Chiaverano, L.M. & B.S. Holland. 2014. Impact and threat assessment of a
predatory invasive lizard on the endangered Hawaiian snail Achatinella
mustelina. Endangered Species Research. 24:115-123 (Impact factor 2.26)
•
Chiaverano, L.M., M. Wright, & B.S. Holland. 2014. Movement behavior of
invasive Jackson’s chameleons in Hawaii. Journal of Herpetology. 48(3) In press.
(Impact factor 0.89).
•
O’Rorke R., G.M. Cobian, B.S. Holland, M.R. Price, & A.S. Amends. 2014.
Dining local: the diet of a snail that grazes microbial communities is
geographically structured, Environmental Microbiology. doi: 10.1111/14622920.12630. [Epub ahead of print]. (Impact factor 6.24)
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Appendix ES-9 HTSCL Annual Report 2014
TREE SNAIL PREDATOR STUDIES
Bird dissection results:
Aside from care and maintenance of tree snails OANRP staff has provided a
number of invasive birds for dissection and gut content analysis. Observations of field
biologists including relatively low counts of juvenile and subadult size classes of
Achatinella mustelina within the predator exclosure structure, in conjunction with
observed bird activity in the host trees for this endangered tree snail, motivated this
investigation. To date, OANRP staff had delivered 41 invasive birds for dissection and gut
content analysis, from Army managed land at Puu Hapapa.
Birds
Snails
Species
n
Red-Vented Bulbul
9
0
Japanese White eye
12
0
1
0
13
0
Red-billed Leiothrix
6
1
House Finch
1
0
Francolin
1
0
41
1
Shama
Red-Whiskered Bulbul
Totals
Birds with snails
2
2
Table 2. Summary of invasive bird dissections from Puu Hapapa to date. The two snails found in
one Leothrix were both very small (< 2 mm) nonnative species, no Achatinella shells have been
found in a bird to date.
No additional snails have been found in the bird dissections. We dissected a large
Francolin collected by OANRP personnel at Puu Hapapa during this reporting period,
and found only plant material, plus one earwig (insect) in the stomach and
gastrointestinal tract. We also caught and preserved an Indian Mongoose, on the trail just
below the summit of Hawaii Loa Ridge while collecting HTSCL leaves for snail cages.
Dissection of this specimen yielded only unidentifiable plant material, no evidence of
bird or snail prey was found.
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Appendix ES-9 HTSCL Annual Report 2014
Jacksons chameleon dissection results:
We have examined gut contents of 74 chameleons during the reporting period.
Details of snails are shown below, while arthropod composition of guts are still being
analyzed, and will be made available upon completion.
Locality
Predator
Puu
Hapapa
2 birds
(1 White eye,
1 Francolin)
Puu
Hapapa
27 chameleons
Palikea
1 chameleon
Number and species
ID of snails
Identifiable nonsnail gut contents
0
Various seeds,
spiders and other
arthropods
11 Achatinella mustelina,
13 Philonesia,
1 Euglandina
5 Philonesia
1 Succinea
spiders and other
arthropods
spiders and other
arthropods
Table 1. Summary of invasive predator dissections collected at Puu Hapapa (73
chameleons) and Palikea (1 chameleon), Oahu. A total of 74 chameleons have been
dissected for this portion of the study to date. Snail shells were found in 28 of these, and
11 Achatinella mustelina were found in the guts of 6 of these chameleons, all collected at
Puu Hapapa. Although incidence of snails in predator guts has remained relatively low,
arthropod prey items in guts were abundant, suggesting short residence time for shells in
gut (3 - 4 days). We have estimated that at the chameleon density observed at Puu
Hapapa, and factoring in the rate of consumption observed, for each hectare of habitat
where chameleons and tree snails are present, up to 4,870 tree snails will be eaten per
year (Chiaverano & Holland, 2014. Endangered Species Research. 24:115-123). To date
A. mustelina is the only achatinelline tree snail species that has been found in the guts or
feces of Jackson’s chameleons.
Euglandina Angle Trap Trials
We are currently testing the first attempt to target and trap E. rosea in Hawaii without
bait or poison, by deploying double-sided angle traps that we designed and built in the lab.
These consist of rigid, lightweight linear sheets of smooth material with a dual 45-degree
angle affixed to the upper edge (see Figure 1), via bolts and wing nuts.
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Appendix ES-9 HTSCL Annual Report 2014
Figure 1. Schematic design for Euglandina rosea Angle Trap. Materials being tested are rigid plastic. Vertical
element may be folded for transport, and angle is affixed in the field. Also rigid stakes are used along
the bottom edge to secure trap to the ground.
The idea for the basic design is based on the angle barriers incorporated on the lower
portions of the Puu Hapapa and Palikea exclosure structures. Predatory snails in native
forest locations appear to randomly move through space while foraging, when they
encounter the angle barriers at Puu Hapapa and Palikea, crawl up as far as the are able,
until they encounter the angle barrier, where they simply stop moving and accumulate.
This is a potentially inexpensive, non-toxic, noninvasive approach. We conducted
preliminary laboratory testing, and demonstrated that the concept works on a small scale
in the laboratory, and traps all sizes of E. rosea for multiple days. We are planning to
optimize design, material, and scale via field-testing. If successful, initial field trials will
lead to the deployment of larger scale and numbers of the angle traps in priority areas of
greatest conservation concern (Fig. 2).
The total area covered by the multiple traps at these locations would depend on the
unique site terrain. As a starting point, we propose to build 6 traps at dimensions shown
in Figure 1. Dimensions will be adjusted to maximize effectiveness. In order to mimic
conditions at the exclosure fences, and ensure that foraging predators encounter the
smooth edge of the trap without passing underneath, clear ground areas are selected, and
where possible/necessary, deployment sites are cleared such that traps are placed flush
with the ground surface. The gap below the
angle is searched with a mirror at
Figure 2. Example of grid deployment of Angle Traps.
Along with design of traps themselves we will also optimize
placement orientation to maximize encounters of foraging
Euglandina rosea.
regular intervals, ideally until no additional
Euglandina are trapped. At that point the traps
can be either be moved to an adjacent area at
the same site or a new location, based on the
number of invasive snails collected, etc.
If effective, deployment of double sided angle traps have the potential to dramatically
change the outlook for native island snail fauna. We have built 8 prototypes and deployed
them at Puu Hapapa for testing, with consultation and help from the OANRP staff
biologists.
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Appendix ES-9 HTSCL Annual Report 2014
Figure 3. Angle box box lab tests were largely successful, set-up, showing screen (c) and one escaped snail
(r).
Also we moved all live Euglandina rosea as well as Jackson chameleon research out of
the HTSCL during the reporting period.
Environmental Chamber Maintenance
Although environmental chambers last for up to 10 – 12 years in the HTSCL, since we
need to provide the tree snails with water three times per day, the main factor leading to
chamber demise is typically rust. During the summer of 2014, for example, our oldest
chamber failed when the door hinges broke free of the frame due the rust penetrating
through the supporting structure. I had a chamber repair specialist here from Technical
Services Hawaii, who examined the chamber and determined it is not repairable.
Therefore in order to maximize the durability and life of the chambers, I have begun
refurbishing and rust–proofing the portions of chambers that tend to suffer rust damage,
namely the chamber floors, doors and light fixtures. This should extend the functional life
of the chambers.
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Appendix ES-9 HTSCL Annual Report 2014
A.
B.
C.
D.
E.
Figure 1. Chamber refurbishing and maintenance. Photo labeled A shows rust penetrating the
frame of the chamber, where door hinge failed. Photos B and C depict a typical rusted chamber
floor and door with light fixture. We moved the chamber outdoors, treated for rust, scraped with
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Appendix ES-9 HTSCL Annual Report 2014
wire brush and steel wool, primed the surface, then repainted the interior. We waited 72 hours for
the paint to dry and fumes to dissipate, then moved the chamber back inside the HTSCL.
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