Successful reintroduction of the Critically Endangered Antiguan racer Alsophis antiguae to offshore islands in Antigua, West Indies

Abstract

The Critically Endangered Antiguan racer Alsophis antiguae is endemic to Antigua and Barbuda (441 km² area) but declined following the arrival of invasive mammals. By 1995, only an estimated 51 Antiguan racers survived on an offshore islet (Great Bird Island: 8·4 ha), many of which had injuries consistent with rat bites. To prevent extinction, a consortium of national and international organizations eradicated the Black rats Rattus rattus from Great Bird Island in 1995 and the snake population promptly doubled in size. The agencies then embarked on a programme to eradicate invasive rats and, where present, Small Asian mongooses Herpestes javanicus from a further 14 islands around Antigua. The first reintroduction was carried out in November 1999, with ten wild racers translocated from Great Bird Island to Rabbit Island. Further reintroductions followed to Green Island (from October 2002) and York Island (from January 2008), bringing the total area of occupancy for racers to 63 ha. The translocated racers appeared to thrive in their new habitats and reproduced almost immediately. The reintroduction programme was underpinned by field research, fundraising and an innovative education campaign to address prevailing negative attitudes towards snakes. While the Antiguan racer metapopulation has increased to > 1100 individuals in the wild, lasting success depends on Great Bird, Rabbit, Green and York Islands being fully protected from invasive mammals and harmful developments. To spread the risk, additional reintroduction sites must be identified.