Review article: The catastrophic impact of invasive mammalian predators on birds of the UK Overseas Territories: a review and synthesis

Abstract

The UK has sovereignty over 16 Overseas Territories, which hold some of the world’s great seabird colonies and collectively support more endemic and globally threatened bird species than the whole of mainland Europe. Invasive alien mammalian predators have spread throughout most of the Territories, primarily since European expansion in the 16th century. Here we review and synthesize the scale of their impacts, historical and current, actions to reduce and reverse these impacts, and priorities for conservation. Mammalian predators have caused a catastrophic wave of extinctions and reductions in seabird colony size that mark the UKOTs as a major centre of global extinction. Mammal‐induced declines of threatened endemics and seabird colonies continue, with four Critically Endangered endemics on Gough Island (Tristan da Cunha), St Helena and Montserrat directly threatened by invasive alien House Mice Mus musculus, Feral Cats Felis catus and rats Rattus spp. Action to reduce these threats and restore islands has been modest in comparison with other developed countries, although some notable successes have occurred and a large number of ambitious eradication and conservation plans are in preparation. Priority islands for conservation action against mammalian predators include Gough (which according to one published prioritization scheme is the highest‐ranked island in the world for mammal eradication), St Helena and Montserrat, but also on Tristan da Cunha, Pitcairn and the Falkland Islands. Technical, financial and political will is required to push forward and fund the eradication of invasive mammalian predators on these islands, which would significantly reduce extinction risk for a number of globally threatened species.

Invasive predators and global biodiversity loss

“…This search returned 771 records, which we inspected to determine whether invasive alien predators were identified as a known or likely threat to each species (n = 703 species identified as negatively impacted by invasive predators). We crosschecked this list against previous reviews (1,18,20,(44)(45)(46)(47)(48) and added 35 additional threatened species recorded as being negatively affected by invasive predators, but not revealed in our Red List search. Given the small number of additional species identified and the broad geographic coverage of the previous studies used for cross-checking, we do not consider that this exercise brings any systematic bias to our analyses.…”

The biodiversity of the United Kingdom’s Overseas Territories: a stock take of species occurrence and assessment of key knowledge gaps

“…They support a wealth of biodiversity (Prince and Croxall 1996;Procter and Fleming 1999;Cuthbert 2004;Angel and Cooper 2006;Sheppard et al 2013;Churchyard et al 2014;Friedlander et al 2014;Weber et al 2014;Havery et al 2015) much of which faces immediate threat, particularly from invasive alien species (Hilton and Cuthbert 2010;Dawson et al 2015). However, conservation action is constrained by the limited, poorly prioritised, and taxonomically biased biodiversity information (Clark and May 2002;Game et al 2013).…”

Feral cats threaten the outstanding endemic fauna of the New Caledonia biodiversity hotspot

“…Cats are efficient predators that can kill both adults and chicks of most small or medium-sized species of seabirds. Procellariides' naive and clumsy behavior when on the ground makes them particularly vulnerable to introduced predators (Bourgeois and Vidal, 2008;Hilton and Cuthbert, 2010). Due to their long lifespans, low reproductive rates and delayed maturity, the population dynamics of these seabird species is particularly sensitive to adult mortality (e.g.…”