Falkland Islands Offshore Rat Eradication Programme

The Falkland Islands' offshore archipelago hosts globally important seabird and passerine populations, including the endemic Cobb's wren (Troglodytes cobbi), but introduced Norway rats (Rattus norvegicus) devastate ground-nesting birds on invaded islands. From 2001, Falklands Conservation, the Wildlife Conservation Society (owner of Steeple Jason Island) and local landowners engaged New Zealand rodent-eradication specialist Derek Brown to run a rolling programme of island-by-island rat eradications using bait stations and trapping.

Between 2001 and 2019, the programme successfully cleared Norway rats from 65 islands totalling roughly 6,500 hectares, ranging from under 1 hectare up to the 2,070-hectare Bleaker Island (cleared in 2019) -- for a cumulative cost of under £250,000, one of the most cost-efficient island-eradication records documented globally.

A peer-reviewed study (Tabak et al., Journal of Animal Ecology, 2015) surveyed 230 Falkland islands -- 85 still holding rats, 108 historically rat-free, and 37 post-eradication -- and found that passerine species richness on eradicated islands converged with that of historically rat-free islands within just 1-11 years, with strong recoveries of vulnerable species such as Cobb's wren and the blackish cinclodes.

26 additional islands that were cleared became re-invaded within five years, underscoring the need for sustained biosecurity monitoring, and two larger islands remain untreated because the terrain requires costlier helicopter-based operations.

Read the full analysis: https://mousefreemarion.org/a-success-story-65-islands-in-the-falklands-have-been-cleared-of-their-invasive-rats/