Responses of seabirds to the rabbit eradication on Ile Verte, sub-Antarctic Kerguelen Archipelago

Abstract

Studies on the role of introduced rabbits, Oryctolagus cuniculus, on islands have mainly focused on their negative impacts on vegetation. However, little attention has been paid to their influence on vertebrate communities. On Ile Verte (148ha) in the sub-Antarctic Kerguelen Archipelago, rabbits are the only mammal that have been introduced. The long-term consequences of their eradication in 1992 on both native, burrowing seabird prey populations and their predator, the brown skua Catharacta skua, were investigated between 1991 and 2005. Densities of breeding petrels were followed on site with three plant communities differing in their soil depth. In addition, the diet and breeding activities of skuas were evaluated on the entire island area. The density of breeding pairs of the most abundant petrel species, the blue petrel Halobaena caerulea, which only nested at the site with deep-soil, increased by approximately eightfold during the 6years following the rabbit eradication. Of the other species nesting in deep soil, there was an approximately fourfold reduction in the Antarctic prion, Pachyptila desolata, but such a decrease in breeding pair densities was not observed in areas with shallow soils. The South-Georgian diving petrels, Pelecanoides georgicus, was the rarest species, nesting only on mineral soils, and for which breeding pairs did not vary through time. The total numbers of fledged chicks of skua on the island significantly increased during the study period, but not the total number of breeding pairs. Thus, brown skuas were not affected by the disappearance of rabbits and rather benefited from an increase of their preferred prey. Blue petrels recovered quickly to sites with deep-soil, benefiting from the rabbit eradication and the cessation of burrow disturbance. The decrease of Antarctic prions could have been the result of an exclusion process from nesting areas on the deep soil site by blue petrels. © 2011 The Authors. Animal Conservation © 2011 The Zoological Society of London.