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Antarctic Science 25(6), 763–766 (2013) & Antarctic Science Ltd 2013 doi:10.1017/S0954102013000126

Observations of mice predation on dark-mantled sooty albatross and Atlantic yellow-nosed albatross chicks at Gough Island

R.J. CUTHBERT1, H. LOUW1,2, G. PARKER1,2, K. REXER-HUBER1,2 and P. VISSER1,2

1 Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, SG19 2DL, UK

2 DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, University of Cape Town, Rondebosch 7701, South Africa

[email protected]

Abstract: Introduced house mice Mus musculus L. have been discovered to be major predators of chicks of

the Tristan albatross Diomedea dabbenena L. and Atlantic petrel Pterodroma incerta Schlegel and to also

predate great shearwater Puffinus gravis O’Reilly chicks at Gough Island, and similar predatory behaviour

has been reported for house mice on Marion Island. Observations on Gough Island over three breeding

seasons of nesting Atlantic yellow-nosed albatrosses Thalassarche chlororhynchos Gmelin and dark-

mantled sooty albatross Phoebetria fusca Hilsenberg indicate that house mice are also preying on these two

species: the first records of mice preying upon summer-breeding albatross species on Gough Island.

Predation on these two albatross species appears to be relatively rare ( , 2% for the Atlantic yellow-nosed albatrosses) and ongoing monitoring is required to ascertain if the impact of mice is increasing.

Conservation actions to eradicate mice from Gough Island will be of benefit to these species and other

species that are being impacted by this invasive species.

Received 17 September 2012, accepted 7 December 2012, first published online 21 May 2013

Key words: conservation, invasive species, Mus musculus, Phoebetria fusca, Thalassarche chlororhynchos

Introduction

The impact of invasive mammalian predators on islands is

well known (Atkinson 1985, Jones et al. 2008) and invasive

species remain one of the key threats for the conservation of

many bird species (Butchart 2008, Hilton & Cuthbert 2010).

On Gough Island in the South Atlantic Ocean, introduced

house mice Mus musculus L. prey on the chicks of albatrosses

and burrowing petrels. To date mice have been reported

killing nestlings of three seabird species: the Critically

Endangered Tristan albatross Diomedea dabbenena L., the

Endangered Atlantic petrel Pterodroma incerta Schlegel, and

the Least Concern great shearwater Puffinus gravis O’Reilly

(Cuthbert & Hilton 2004, Wanless et al. 2007). Further

evidence indicates that eggs and chicks of the endemic and

Critically Endangered Gough bunting Rowettia goughensis

Clarke are also preyed upon by mice on the island (Cuthbert &

Hilton 2004, Ryan & Cuthbert 2008). For populations of

winter-breeding Tristan albatross and Atlantic petrel the

current levels of predation are unsustainable, with 65–80% of

chicks killed each season (Cuthbert 2004, Cuthbert et al.

2004, Wanless et al. 2012). There are further concerns

and growing evidence that all winter breeding petrels on

Gough are being affected by mice predation (Angel &

Cooper 2006, Cuthbert et al. 2013). In this paper we describe

observations of mice predation on chicks of the summer-

breeding Atlantic yellow-nosed albatross Thalassarche

chlororhynchos Gmelin and dark-mantled sooty albatross

Phoebetria fusca Hilsenberg, the first records of such attacks

on Gough Island for these two globally endangered species.

Study area and methods

Monitoring of Atlantic yellow-nosed albatrosses was

undertaken at a long-term study colony (Cuthbert et al.

2003) and three other sites that are part of a monitoring

programme for the species (Cuthbert & Sommer 2004).

These four areas held 277–300 breeding pairs in the

three seasons of study (2008/09, 2009/10 and 2010/11).

Monitoring of chicks was made on at least weekly intervals

at the long-term study colony from hatching until all chicks

had fledged, with visits to the three other areas after the

peak of egg laying, after hatching and shortly before

fledging. Dark-mantled sooty albatross monitoring was

conducted via scan counts of coastal and inland cliffs

(Cuthbert & Sommer 2004) that held 212–238 breeding

pairs during the three seasons, with further counts in late

December and mid-March of numbers of hatched and

fledging chicks. Around 50 nests and chicks were checked

during 2008/09 and 2009/10 from both coastal and inland

areas with monthly nest checks in the 2009/10 season.

Further incidental observations on sooty albatross chicks

were made during ongoing plant eradication work on the

island’s sea-cliffs.

Results

The fresh carcass of a sooty albatross chick was discovered

at a nest on 15 December 2008. The chick had round

open wounds to the skin of its belly and the abdominal

cavity was exposed with the intestines visible (Fig. 1).

763

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Other than the observed wounds, the chick was undamaged

and appeared to be in good body-condition, with a mass of

0.45 kg and internal fat deposits. Directly underneath the

chick and located within the chick’s nest was the entrance

to a mouse hole (Fig. 1). A second dead sooty albatross

chick was found during the same period and on the same

stretch of cliffs. The body of this chick was too

decomposed to assess patterns of wounds, although it was

clear that the skin had been removed from behind its neck.

Fledging success (number of fledging chicks/number of

hatched chicks) of sooty albatrosses during the three

seasons was 56% (n 5 87 hatched chicks), 69% (n 5 78)

and 46% (n 5 82) in the 2008/09, 2009/10 and 2010/11

seasons, with an overall mean of 57.1 ± 11.5%.

An Atlantic yellow-nosed albatross chick was found

dead on 15 January 2010. This chick had hatched on the

22 December and weighed 1.7 kg at the time of death. The

carcass was fresh with very few fly maggots and other

invertebrates present and no visible sign of decay. Wounds

were found on the lower belly, exposing the viscera (Fig. 2).

The nest mound had a mouse hole in the cup and a mouse

hole at the base of the pedestal, with a well-used track

leading to it (Fig. 2). This predated chick was one of

52 hatched chicks in the long-term study colony where

regular (more than twice weekly) checks were made in the

2009/10 season, suggesting mice preyed upon a minimum of

2% of chicks in this season. Fledging success of this species

was 53% (n 5 194 hatched chicks), 64% (n 5 201) and 82%

(n 5 175) in the 2008/09, 2009/10 and 2010/11 seasons,

respectively. However, there was considerable variation

between the four sites in rates of survival during the 2009/10

breeding season with a coefficient of variation (CV) of 0.631

in comparison to CVs of 0.101 and 0.115 in the other two

years (Table I). The high variation in the 2009/10 season was

due to one site with very low chick survival (Table I).

Inspection of a sample of Atlantic yellow-nosed albatross

nest mounds (n 5 86 at two of the four sites) in the 2009/10

season indicated that 34% of nests had mouse holes in them,

of which eight had holes into the nest cup.

Discussion

This is the first time that mice have been reported to prey

upon summer-breeding albatross species on Gough Island

and the first records, of which we are aware, of mouse

preying on Atlantic yellow-nosed albatross chicks and

second observation of mice attacks on sooty albatross

chicks (Jones & Ryan 2009). The wounds to the stomach

and rump, and exposed viscera were identical in both

location and character to wounds observed on Tristan

albatross and Atlantic petrel chicks attacked by mice on

Gough Island and to wounds on wandering albatross

Diomedea exulans L. and dark-mantled sooty albatross

chicks on Marion Island (Cuthbert & Hilton 2004, Wanless

et al. 2007, Jones & Ryan 2010). The apparent rarity or

absence of mice preying upon summer breeding species on

Gough Island led Angel & Cooper (2006) to conclude that

the impact of mice was likely to be low for summer-

breeders, in contrast to the situation for winter-breeders.

This appears to be the case for both the yellow-nosed and

sooty albatross on Gough Island, where, despite the

observed predation events, overall rates of chick survival

are relatively high and in the range previously recorded for

the species on Gough and other islands (Tickell 2000,

Cuthbert et al. 2003). However, it is apparent that on a local

scale mice may be detrimental, with only 7% of Atlantic

yellow-nosed albatross chicks surviving to fledge at one site.

It is also important to note that the scavenging behaviour of

sub-Antarctic skuas Catharactica antarctica Lesson and

southern giant petrels Macronectes giganteus Gmelin on

Gough Island means that without frequent nest checks many

chicks could have been consumed and ‘‘disappeared’’

leaving no evidence that they were originally preyed upon

Fig. 1. a. The carcass of a sooty albatross chick with wounds to

its belly and abdomen and exposed viscera, and b. location

of the mouse hole within the nest and beneath the carcass of

the chick.

764 R.J. CUTHBERT et al.

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by mice. Consequently, levels of mouse depredation of

sooty and yellow-nosed albatross chicks on Gough Island

could be higher than suggested by our observations.

House mice have been reported to prey on chicks of

passerines and small petrels in other studies (Fugler et al.

1987, Ainley et al. 1990, Campos & Granadeiro 1999,

Michelsen-Heath & Gaze 2007), however it is only on

Gough Island and on sub-Antarctic Marion Island (Jones &

Ryan 2010) that house mice are known to prey upon

chicks of albatross species. At both Marion Island and

Gough Island predation events appear to be associated with

house mice utilizing albatross nest mounds. Mice on sub-

Antarctic islands are known to utilize burrows in order to

provide a warmer microclimate and their burrows are

disproportionally found in wandering albatross nesting

mounds in comparison to other habitats (Avenant & Smith

2003). These authors attribute the high proportion of mice

burrows around albatross nests to the high densities of soil

macro-invertebrates in these manure enriched sites, as

macro-invertebrates are a preferred food item for house

mice (Gleeson & Van Rensburg 1982, Jones et al. 2003).

An unfortunate by-product of this site selection by house

mice is that it may have contributed to the predatory

behaviour of mice on Gough and Marion islands, as such

burrows will place mice directly underneath albatross

chicks where chicks are most vulnerable.

Given the evidence for mice preying on two additional

species, further monitoring of breeding success and causes

Fig. 2. a. The carcass of an Atlantic yellow-nosed albatross chick with wounds on the belly and exposed viscera, and b. location of the

mouse hole within the nest mound and entrance of the mouse hole at the base of the pedestal.

Table I. Values of fledging success of Atlantic yellow-nosed albatrosses on Gough Island with sample size of hatched chicks in parentheses for the four

monitored sites and three breeding seasons, with the overall mean, standard deviation (SD) and coefficient of variation (CV).

Season Site 1 Site 2 Site 3 Site 4 Mean ± SD CV

2008/09 50% (48) 44% (45) 54% (24) 58% (77) 51.8 ± 6.0% 11.5%

2009/10 86% (52) 8% (50) 56% (27) 89% (72) 59.7 ± 37.7% 63.1%

2010/11 84% (32) 81% (53) 67% (21) 81% (69) 78.3 ± 7.9% 10.1%

MOUSE PREDATION OF ALBATROSSES AT GOUGH ISLAND 765

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of nesting failure are warranted for these and other species

to determine if this behaviour is becoming more

widespread and of greater severity on Gough Island.

Proposed conservation management actions to eradicate

house mice from Gough Island in order to remove a key

threat to the Critically Endangered Gough bunting and

Tristan albatross and Endangered Atlantic petrel will have

further benefits in eliminating this cause of breeding failure

for the Endangered Atlantic yellow-nosed albatross and

dark-mantled sooty albatross.

Acknowledgements

We thank the South African National Antarctic

Programme, University of Cape Town and Royal Society

for the Protection of Birds for providing logistical support

in the field and the Tristan da Cunha Conservation

Department for granting permission to work on Gough

Island. Funding was provided by the UK Government’s

Overseas Territories Environment Programme (OTEP).

Thanks to M. Nysschens for assistance with albatross

monitoring. The constructive comments of the reviewers

are gratefully acknowledged.

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