Antigua announces 15th island cleared of invasive alien mammals

Abstract

Conservation news Antigua announces 15th island cleared of invasive alien mammals The once-forested island nation of Antigua and Barbuda in the Eastern Caribbean looks starkly different today. Besides having lost most of its forest cover-first to agriculture and later to urban sprawl and tourism developments-this small country has suffered from a wide range of harmful invaders. Among the most devastating for wildlife are the Eurasian black rat Rattus rattus, which reached the Caribbean with European settlers in the th century, and the small Asian mongoose Herpestes javanicus, introduced in the late th century in an attempt to control the rats. Many native species have been lost, including the Antiguan burrowing owl Athene cunicularia amaura, the endemic Antiguan and Barbudan muskrats 'Ekbletomys hypenemus' and Megalomys audreyae and, most recently, the Lesser Antillean iguana Iguana delicatissima. While native biodiversity declined on Antigua and Barbuda, the country's uninhabited offshore islands emerged as vitally important natural refugia. More than  small limestone islands scattered across Antigua's shallow coastal shelf are home to globally important colonies of seabirds, the Vulnerable West Indian whistling-duck Dendrocygna arborea, nesting marine turtles and many of the country's last endemic plants, reptiles and invertebrates. Collectively, the islands have been internationally recognized as a Key Biodiversity Area, an Alliance for Zero Extinction Site, and an Important Bird Area. By the s, however, most of Antigua's offshore islands were occupied by rats, and mongooses had reached the larger islands, further depleting their native flora and fauna. Among the many species affected was the Critically Endangered Antiguan racer Alsophis antiguae, a harmless dipsadid snake. Only c.  racers remained when the species was first surveyed by Fauna & Flora International (FFI) in , all confined to the -ha Great Bird Island, and most had been injured by black rats. To save these rare snakes, rats were successfully eradicated from Great Bird Island and two neighbouring cays in  by staff from FFI, the Forestry Unit and the Environmental Awareness Group. Since then efforts to remove invasive alien mammals have expanded across the archipelago, with  islands successfully targeted:

Invasive mammal eradication on islands results in substantial conservation gains

“…For example, rat eradication was undertaken on Great Bird Island, an islet off Antigua in the Lesser Antilles, which houses the only population of world's rarest snake, the critically endangered Antiguan racer (Alsophis antiguae) (36). The outcome has been highly successful, with the Antiguan racer population increasing 20-fold on four islands (38). Following rat eradication on Langara Island in Canada, the population of ancient murrelets (Synthliboramphus antiquus) was estimated to double, and Cassin's auklets (Ptychoramphus aleuticus) recolonized the island (37).…”

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

“…Not only was it necessary to treat the target islands (Table ) but also other nearby islands that could serve as stepping stones for the invasive species to return. Between 1995 and 2014, 15 offshore cays were cleared of rats and, where present, mongooses (Lawrence & Daltry, ). Rats were eradicated using methods described by Varnham et al .…”