Albatross chicks being eaten alive by mice.

April 2007, update on an earlier 2005 article.

The house mouse is one of the most widespread and well-studied invasive mammals on islands worldwide. It was thought to pose little risk to seabirds, but video evidence from Gough Island, South Atlantic Ocean shows house mice killing chicks of two IUCN-listed seabird species. In fact mouse-induced mortality in has been shown to be a significant cause of extremely poor breeding success for Tristan albatrosses, (0.27 fledglings/pair), and Atlantic petrels, (0.33 fledglings/pair). Population models show that these levels of predation are sufficient to cause population decreases. Unlike many other islands, mice are the only introduced mammals on Gough Island.

 

However, restoration programmes to eradicate rats and other introduced mammals from islands are increasing the number of islands where mice are the sole alien mammals. If these mouse populations are released from the ecological effects of predators and competitors, they too may become predatory on seabird chicks.

Gough Island endangered species
Gough Island (408 S, 98 W), South Atlantic Ocean is a World Heritage Site and a globally important seabird breeding colony. It has two endemic land birds—the Gough moorhen (vulnerable) and Gough bunting (vulnerable)—and the last viable breeding populations of two seabird species—the Tristan albatross (endangered) and the Atlantic petrel (vulnerable).

 

House mice were introduced there before 1888 and are the only alien mammals present. In 2000/2001, unexpectedly high breeding failure of Tristan albatrosses and Atlantic petrels was reported on Gough, and predation by mice was mooted. It has been confirmed that mice do attack and kill chicks up to 300 times their mass, and report a second season of low breeding success among affected seabirds. It is argued that similar mouse predation may have been overlooked elsewhere, and may be most likely where mice are the sole alien mammal.

This is the first record of widespread and devastating predation by house mice on seabird chicks, despite mice having been introduced to many seabird islands. Has it been overlooked? Or is there something peculiar about Gough Island? The climate and native biota are not unusual, and it seems unlikely that some other condition, as yet undefined, could have given rise to predatory behaviour. Perhaps of more importance is that among 385 islands with bird species known to be sensitive to invasive species, only six, including Gough, have house mice as the only invasive mammal.

It is now thought that where house mice are part of a complex of invasive mammals, the effects of dominance, competition and predation by larger species render mice less of a threat to native vertebrates. Recent events on Marion Island (468 S, 378 E) support this hypothesis.

House mice became the sole introduced mammal following the eradication of cats, Felis catus, in the 1990s. Since 2004, several wandering albatross chicks have succumbed to wounds consistent with mouse attacks. This is the first time in over 20 years of intensive study that wounds of this nature have been recorded.

The full report is published in the journal 'Biology Letters.'