Of Mice and Men - Enlarged rodents threaten Gough seabirds

An article in the UK's Guardian Newspaper by environmental editor John Vidal reports on the extraordinary growth (literally) of accidentally introduced population of the House Mouse Mus musculus on Gough Island (-40.316667°, -9.916667°) in the South Atlantic. The mice grow to up to three times the size of ordinary house mice, and have adapted a carnivorous diet consuming albatross, petrel and shearwater chicks alive!

Albatross chicks weigh up to 10 kg and the mice weigh 35g. In the words of RSPB scientist Geoff Hilton, "it is like a tabby cat attacking a hippopotamus".Hints of the predatory behavior of the mice were obtained by Richard Cuthbert, a RSPB researcher, and Erica Sommer from Cape Town University after work on the island in 2000-2001. Their suspicion was confirmed by Cuthbert and Ross Wanless from the University of Cape Town’s Percy FitzPatrick Institute in 2005 with dramatic video footage of the attacks (Wanless et al. 2005).

Complete eradication of the mice is an urgent priority. Gough supports 20 species of nesting seabird including the Tristan (Wandering) Albatross Diomedea dabbenena and 99% of the world's Atlantic Petrels Pterodroma incerta. The 2008 IUCN Red List classifies both the albatross and petrel as 'Critically Endangered' and 'Endangered' respectively meaning that they are considered to be facing an extremely high (CE) or a very high (E) risk of extinction in the wild. It is estimated that 60% of Atlantic Petrel chicks (some 700,000/annum) die before fledging most as the result of mouse predation. The ground-nesting Gough Bunting Rowettia goughensis, an island endemic, is similarly threatened with imminent extinction unless something is done. Gough has a land mass of 35 square miles (91 km²) and a rodent population of 700,000 and upwards. Introduced rats have already decimated seabird populations on the main island of the Tristan da Cunha archipelago, of which Gough is a part.

A £220,000 grant from the UK Government's 'Overseas Territories Environment Programme' has supported a provisional study to test the effect of dropping poisoned bait by helicopter, an approach used with great success by the New Zealand and Australian Governments. The Royal Society for the Protection of Birds (RSPB) is also contributing personnel to the rodent eradication effort. Fortunately, the equally important Inaccessible and Nightingale Islands are free of rats and mice thanks to the strict adherence to conservation guidelines introduced for all visits to these islands by the Tristan community.

Wanless RM, Angel A, Cuthbert RJ, Hilton GM, Ryan PG. Can predation by invasive mice drive seabird extinctions? Biol Lett. 2007 Jun 22;3(3):241-4.