Download Evidence of mouse attacks on albatross chicks on sub

Antarctic Science 22(1), 39–42 (2010) & Antarctic Science Ltd 2009
doi:10.1017/S0954102009990459
Evidence of mouse attacks on albatross chicks on sub-Antarctic
Marion Island
M.G.W. JONES* and P.G. RYAN
Percy FitzPatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa
*[email protected]
Abstract: Introduced house mice Mus musculus have recently been discovered to be significant predators
of chicks of Tristan albatrosses Diomedea dabbenena and several burrowing petrels at Gough Island. We
summarize evidence for mouse attacks on albatross chicks at sub-Antarctic Marion Island, where mice are
also the only introduced mammal following the eradication of feral cats Felis catus in the early 1990s.
Wounds consistent with mouse attacks have been found on wandering albatrosses Diomedea exulans since
2003 and dark-mantled sooty albatrosses Phoebetria fusca in 2009. To date, attacks on wandering albatross
chicks have been infrequent, affecting ,1% of chicks in study colonies, and only about half of the attacks
have been fatal. Small chicks may also die when mouse burrows collapse under chicks, trapping them.
Mouse attacks appear to be a recent phenomenon, supporting the contention that mice pose a significant
threat when they are the only introduced mammal species. Ongoing monitoring is needed to assess whether
the impacts of mice increase over time. Our observations add impetus to calls for the eradication of mice
from Marion Island.
Received 29 June 2009, accepted 6 August 2009
Key words: alien species, conservation, Diomedea exulans, Mus musculus, Phoebetria fusca
P. palpebrata (Forster) (Near-Threatened; Ryan et al.
in press). These species are listed as threatened largely
due to accidental mortality on fishing gear, especially
longlines (BirdLife International 2008 - www.birdlife.org).
Both species of giant petrels Macronectes spp. (NearThreatened) are also common surface-nesters at the island,
and at least nine other species of petrels breed in burrows
on the island, including white-chinned petrels Procellaria
aequinoctialis L. (Vulnerable; Ryan & Bester 2008). In this
paper we report evidence of mouse attacks on seabird
chicks on Marion Island following the eradication of cats
from the island.
Introduction
Until recently, populations of house mice Mus musculus L.
introduced to oceanic islands were considered to have little
impact on breeding bird populations. However, recent
observations at Gough Island have shown significant
impacts on both seabirds and endemic landbirds (Cuthbert
& Hilton 2004, Wanless et al. 2007, 2009, Ryan &
Cuthbert 2008). Wanless et al. (2007) argued that mice are
likely to be most problematic at islands where they are the
only introduced mammal. In the absence of competition
and predation by other, larger introduced mammals, mice
attain high population densities that may trigger predatory
behaviour. Sub-Antarctic Marion Island is one such island.
Mice were introduced to Marion presumably by sealers
sometime before 1818, and cats Felis catus L.
were brought to the island in 1949 to control mice at
the weather station, resulting in a feral population (Cooper
2008) that decreased breeding success of burrowing petrels
and caused local extinction of some species (De Villiers &
Cooper 2008). Cats were eventually eradicated from the
island by 1992/93 (Bester et al. 2002), leaving mice as the
only introduced mammal.
Marion Island supports significant breeding populations
of several threatened or near-threatened albatrosses: 22%
of the world’s wandering albatrosses Diomedea exulans
L. (Vulnerable), 9% of dark-mantled sooty albatrosses
Phoebetria fusca (Hilsenberg) (Endangered), 7% of greyheaded albatrosses Thalassarche chrysostoma (Forster)
(Vulnerable) and 3% of light-mantled sooty albatrosses
Study area and methods
Marion Island (46854'S, 37845'E, 290 km2) has a vegetated
coastal plain that rises to volcanic scoria peaks (highest
point 1243 m). The island is home to large breeding
populations of seabirds and pinnepeds, and ornithological
research has been conducted on the island since 1965
(Cooper & Brown 1990, Ryan & Bester 2008), with regular
monitoring of breeding success of three wandering
albatross (c. 195–270 nests per annum) and three northern
giant petrel (c. 70–135 nests per annum) colonies since the
1980s (Cooper et al. 2001, Nel et al. 2003), and one greyheaded albatross (c. 90–140 nests per annum) colony since
1996 (Ryan et al. 2007). In these study colonies, breeding
attempts were monitored from egg laying to fledging. Once
the chicks were no longer brooded, they were checked
every 2–4 weeks, and any wounded chicks recorded.
39
Downloaded from https:/www.cambridge.org/core. IP address: 88.99.165.207, on 12 Jun 2017 at 19:38:41, subject to the Cambridge Core terms of use, available at
https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0954102009990459
40
M.G.W. JONES & P.G. RYAN
Fig. 2. The head and neck wounds exhibited by one of nine
dark-mantled sooty albatross chicks near the south-western
point of Marion Island in April 2009 (photo: P.G. Ryan).
Since the mid-1980s, annual counts of the entire breeding
population of wandering albatrosses on Marion Island have
been conducted during early incubation (January), and counts
of large chicks have been made prior to fledging (October),
allowing crude estimates of breeding success around
the island.
Results
Fig. 1. a. A well-feathered wandering albatross chick on Marion
Island exhibits wound on its lower back (photo: M.G.W.
Jones) very similar to b. those inflicted by mice on a Tristan
albatross chick on Gough Island (photo: P.G. Ryan).
Ad hoc observations have also been made of albatross chicks
outside study colonies, including chicks of light-mantled and
dark-mantled sooty albatrosses, as well as small numbers
of white-chinned and great-winged petrel Pterodroma
macroptera (Smith) chicks observed in monitored burrows
of low intensity studies. Wounded chicks were photographed,
and where feasible, their fate was checked by repeated visits.
Since 2003, 12 wandering albatross chicks have been found
on Marion Island with wounds on their backs, rumps and
flanks that were identical to those exhibited by Tristan
albatross Diomedea dabbenena Matthews chicks following
attacks by mice (Fig. 1). Six were recorded among
study colony chicks, with 0–2 records per year (0–2% of
Table I. Numbers of wandering albatross chicks attacked and killed by
mice in relation to breeding effort and success in study colonies at
Marion Island since the first record of a mouse attack in 2003.
Eggs laid
Chicks hatched
Chicks attacked
Chicks killed
Breeding success (%)
2003
2004
2005
2006
2007
2008
Total
268
204
2
1
80
197
153
0
0
71
242
173
1
1
79
199
132
2
0
77
257
213
0
0
72
249
223
1
0
64
1420
1098
6
2
74
Downloaded from https:/www.cambridge.org/core. IP address: 88.99.165.207, on 12 Jun 2017 at 19:38:41, subject to the Cambridge Core terms of use, available at
https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0954102009990459
MOUSE ATTACKS ON ALBATROSS CHICKS ON MARION ISLAND
41
chicks that hatch; Table I). The other six were observed
incidentally, mostly close to the research station, where
observer effort is greatest, but one attack occurred on the
island’s west coast, indicating that attacks occur around the
island. The fates of 11 wounded chicks were followed, of
which six (55%) died. Counts of incubating adults and large
fledglings showed no consistent regional differences in
breeding success around the island.
There has been no evidence of mouse attacks on greyheaded albatross or northern giant petrel chicks, either
in the study colonies or from incidental observations.
However, in April 2009 localized attacks were recorded on
dark-mantled sooty albatross chicks at Marion Island.
Seven of 19 large chicks on two ledges of an inland cliff in
the south-west of the island (Old Sea Cliffs, Toffee Lava)
bore open wounds on the backs of their heads and/or necks
(Fig. 2) similar to wounds observed on some Tristan
albatross chicks on Gough Island (K. Cita, unpublished
photographs). Another dark-mantled sooty albatross chick
bearing similar wounds was observed on sea cliffs near
Bullard Beach on the eastern coast of the island during the
same period (Bo Bonnevie, personal communication 2009).
There have been no incidental observations of attacks on
other seabirds. Mouse activity has been seen in many petrel
burrows, including mice running over and around chicks,
but no definite attacks have been recorded.
Mouse holes are frequently found in nests of wandering
albatrosses and, to a lesser extent, in grey-headed albatross
nests. Many such mouse holes lead into the base of the nest
cup where the mice may obtain a thermal advantage,
especially in winter (Sinclair & Chown 2006). In April 2009
two small wandering albatross chicks died under brooding
adults after they apparently were unable to extricate
themselves from large hollows (c. 10 cm in diameter) in the
nest cup. After death, their carcases required considerable
force to be pulled from these hollows. It is probable that mouse
nests had caved in under the chicks, indirectly killing them.
Wanless et al. (2007) hypothesized that mice have a greater
effect on native vertebrates when they are the sole introduced
mammal on an island. This is because their populations
increase when the combined effects of dominance,
competition and predation are removed. Our observations
lend further support to this hypothesis because the first mouse
attacks were recorded a decade after the eradication of feral
cats, the only other introduced mammal on the island. The
worrying conclusion is that mouse attacks might be expected
to increase at Marion Island, especially if mouse populations
benefit from global warming (de Villiers & Cooper 2008).
This would be cause for serious concern given the large
proportion of the global population of wandering albatrosses
that breeds on Marion Island (Ryan et al. in press). Given the
serious impacts of mice on insular populations when they are
the sole alien mammal, precautions should be taken if
competing aliens are eradicated. Every attempt should be
made to eradicate mice as well as other predatory mammals.
The apparent attacks on dark-mantled sooty albatrosses are
also cause for alarm. One sooty albatross chick has been
recorded killed by mice on Gough Island (Cuthbert et al.
unpublished), but this is the first occurrence of multiple
attacks on chicks in a single colony. Sooty albatrosses are
listed as Endangered (BirdLife International 2008), and are
the only albatross species whose population is decreasing at
Marion Island (Ryan et al. in press). It is also likely that
burrowing petrels are victims of mouse predation at Marion
Island, but that it goes undetected because they are less easily
observed and are not currently studied at this island. In the
1980s, blue petrel Halobaena caerulea (Gmelin) chicks were
apparently attacked by mice on Marion Island (Fugler
et al. 1987). South Africa is a party to the Agreement on
the Conservation of Albatrosses and Petrels (ACAP) and as
such has international obligations to ensure the conservation
of these birds. Continued monitoring of seabird chicks on
Marion Island for signs of mouse predation is required. Our
study provides further support for the need to attempt to
eradicate mice from Marion Island.
Discussion
Acknowledgements
Although mice have not been observed attacking albatross
chicks on Marion Island, the nature of the chicks’ wounds
strongly suggests that mice were responsible. Based on our
observations, currently , 1% of wandering albatross chicks
at Marion Island are attacked by mice. At Gough Island,
mouse attacks on Tristan albatrosses were overlooked
previously because of spatial differences in the frequency
of attacks (Cuthbert & Hilton 2004), but this does not
appear to be the case at Marion Island. It is also probable
that the attacks at Marion only commenced in the last few
years, because monitoring of wandering albatross chicks
has been conducted at the same intensity since the study
colonies were established in the early 1980s without any
records of wounded birds.
We thank Bo Bonnevie, Linda Clokie, Nico de Bruyn,
Quentin Hagens, Henk Louw, Edith Mertz, Cornelia
Niewenhuys, Samantha Petersen, Cheryl Tosh and Paul
Visser, for their observations. Research on Marion Island is
supported by the South African National Antarctic Programme
through the National Research Foundation, with logistical
support from the Directorate: Antarctica and Islands of the
former Department of Environmental Affairs and Tourism.
References
BESTER, M.N., BLOOMER, J.P., VAN AARDE, R.J., ERASMUS, B.H., VAN RENSBURG,
P.J.J., SKINNER, J.D., HOWELL, P.G. & NAUDE, T.W. 2002. A review of the
successful eradication of feral cats from sub-Antarctic Marion Island, southern
Indian Ocean. South African Journal of Wildlife Research, 32, 65–73.
Downloaded from https:/www.cambridge.org/core. IP address: 88.99.165.207, on 12 Jun 2017 at 19:38:41, subject to the Cambridge Core terms of use, available at
https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0954102009990459
42
M.G.W. JONES & P.G. RYAN
COOPER, J. 2008. Human history. In CHOWN, S.N. & FRONEMAN, W., eds.
The Prince Edward Islands: land-sea interactions in a changing
ecosystem. Stellenbosch: Sun Media, 331–350.
COOPER, J. & BROWN, C.R. 1990. Ornithological research at the subAntarctic Prince Edward Islands: a review of achievements. South
African Journal of Antarctic Research, 20, 40–57.
COOPER, J., BROOKE, M. DE L., BURGER, A.E., CRAWFORD, R.J.M., HUNTER, S.
& WILLIAMS, A.J. 2001. Aspects of the breeding biology of the
northern giant petrel (Macronectes halli) and the southern giant petrel
(M. giganteus) at sub-Antarctic Marion Island. International Journal of
Ornitholology, 4, 53–68.
CUTHBERT, R. & HILTON, G. 2004. Introduced house mice Mus musculus: a
significant predator of endangered and endemic birds on Gough Island,
South Atlantic Ocean? Biological Conservation, 117, 483–489.
DE VILLIERS, M.S. & COOPER, J. 2008. Conservation and management. In
CHOWN, S.N. & FRONEMAN, W., eds. The Prince Edward Islands: land-sea
interactions in a changing ecosystem. Stellenbosch: Sun Media, 301–324.
FUGLER, S.R., HUNTER, S., NEWTON, I.P. & STEELE, W.K. 1987. Breeding
biology of blue petrels Halobaena caerulea at the Prince Edward
Islands. Emu, 87, 103–110.
NEL, D.C., TAYLOR, F., RYAN, P.G. & COOPER, J. 2003. Population
dynamics of wandering albatrosses Diomedea exulans at sub-Antarctic
Marion Island: long-line fishing and environmental influences. African
Journal of Marine Science, 25, 503–517.
RYAN, P.G. & BESTER, M.N. 2008. Pelagic predators. In CHOWN,
S.N. & FRONEMAN, W., eds. The Prince Edward Islands: land-sea
interactions in a changing ecosystem. Stellenbosch: Sun Media,
121–164.
RYAN, P.G. & CUTHBERT, R.J. 2008. The biology and conservation status of
the Gough bunting Rowettia goughensis. Bulletin of the British
Ornithology Club, 128, 242–253.
RYAN, P.G., PHILLIPS, R.A., NEL, D.C. & WOOD, A.G. 2007. Breeding
frequency in grey-headed albatrosses. Ibis, 149, 45–52.
RYAN, P.G., JONES, M.G.W., DYER, B.M., UPFOLD, L. & CRAWFORD, R.J.M.
in press. Recent population estimates and trends in numbers of
albatrosses and giant petrels breeding at the sub-Antarctic Prince
Edward Islands. African Journal of Marine Science..
SINCLAIR, B.J. & CHOWN, S.L. 2006. Caterpillars benefit from thermal
ecosystem engineering by wandering albatrosses on sub-Antarctic
Marion Island. Biology Letters, 2, 51–54.
WANLESS, R.M., ANGEL, A., CUTHBERT, R.J., HILTON, G.M. & RYAN, P.G.
2007. Can predation by invasive mice drive seabird extinctions? Biology
Letters, 3, 241–244.
WANLESS, R.M., RYAN, P.G., ALTWEGG, R., ANGEL, A., COOPER, J.,
CUTHBERT, R. & HILTON, G.M. 2009. From both sides: dire
demographic consequences of carnivorous mice and longlining for the
critically endangered Tristan albatrosses on Gough Island. Biological
Conservation, 142, 1710–1718.
Downloaded from https:/www.cambridge.org/core. IP address: 88.99.165.207, on 12 Jun 2017 at 19:38:41, subject to the Cambridge Core terms of use, available at
https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0954102009990459