Predation of Atlantic Petrel chicks by house mice on Gough Island

The impacts of predation by invasive mammals on island fauna are a major driver of insular biodiversity loss. Devastating, hitherto unsuspected impacts of predatory house mice on breeding seabirds have been described recently. We studied the fate of 178 Atlantic Petrel Pterodroma incerta nests at Gough Island, over four seasons, from October 2003 to January 2008. Introduced house mice Mus musculus were found in all study burrows checked for mouse visits. From October 2003 to September 2004, we video-recorded attacks by mice on six (of 13) live, healthy Atlantic Petrel chicks and on one (of three) great shearwater Puffinus gravis chicks. In all years, chicks died from mouse attacks. Stage-specific daily nest survival rates were modelled, from which estimates of breeding success were derived that accounted for the variable exposure periods studied among years. Average daily survival rate of eggs was 0.998, and hatching success through the entire incubation period (55.5 days) was 0.924 [95% confidence interval (CI) 0.903–0.940]. Daily chick survival rates were 0.990, which gave a modelled fledging success of 0.247 (CI 0.165–0.338) over the 138-day chick period, and average annual breeding success (chicks fledged per breeding attempt) of 0.228 (CI 0.150–0.318), which is low compared with congeners. Productivity estimates were used as a parameter in a population simulation model, which predicted a population multiplication rate (λ) of 0.993 (CI = 0.966–1.021). However, in the one season studied from laying to fledging (2007), from 58 nests, only one chick fledged (1.7%). This suggests the wide errors on the model results may obscure a more severe reality. More than 60% of model simulations resulted in an International Union for Conservation of Nature classification of Endangered. Our results add support to calls to eradicate mice from Gough Island. More generally, mice cannot be ignored as a potential threat to island fauna, and island restoration and management plans should routinely include eradication of introduced mice.

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