IUCN Red List Assessment
Red List Category Year Assessed
Critically Endangered Red List Criteria
Daltry, J. & Mayer, G.C. Reviewer/s
Böhm, M., Collen, B. & Ram, M. (Sampled Red List Index Coordinating Team) Contributor/s
Hedges, B., Powell, R., De Silva, R., Milligan, HT, Wearn, O.R., Wren, S., Zamin, T., Sears, J., Wilson, P., Lewis, S., Lintott, P. & Powney, G. Justification
Alsophis antiguae History
has been assessed as Critically Endangered. This species distribution across Antigua and Barbuda has historically been reduced to a single population on Great Bird Island. Since 1995, the Antiguan Racer Conservation Project has led a reintroduction programme, and there are now populations on Rabbit, Green, and York islands, with the global population exceeding 300. However, the species extent of occurrence is only 0.65 km² (less than 0.1% of its natural range) and it is continually threatened by invasive species, inbreeding depression, and natural disasters. Continued conservation management, population monitoring and invasive species control are needed to guarantee the species persistence.
Classified as Critically Endangered (CR) on the IUCN Red List (1).
In 1995, J. Daltry demonstrated the population on Great Bird Island numbered 50 +/- 7 individuals. Since reintroductions on to Rabbit, Green and York Islands the population now exceeds 300 (Daltry et al. in press). Population Trend
Invasive mammals, in particular Black Rats and mongooses, are a major threat to this species and are responsible for its dramatic historical decline in abundance. Although the islands now inhabited have been cleared of invasive predators, re-invasions are a threat. Rats re-invaded Great Bird Island in 2001, but were eradicated the same year (J. Daltry pers. comm. 2010). In late 2005, rats reappeared on Green Island (Daltry 2006), probably transported by visitor boats, but these were successfully eradicated in 2006.
This species is threatened by loss of genetic variation due to its small population size: Genetic studies by Durrell Wildlife Conservation Trust have confirmed the species to be critically inbred, and fertility is low.
Hurricanes can cause flooding on the lowland areas of the island. J. Daltry (pers. comm.) observed a 20% population decline on Great Bird Island after Hurricane Georges in 1998, the storm surges of which flooded more than 10% of the island.
Visitors to the islands may disturb snakes and could affect feeding and mating behaviour. Incidents of visitors killing snakes have also been reported. In addition, activities such as mowing, trampling, and allowing camp fires to burn out of control may pose threats to the viability of the very small population of this species. Visitor numbers on Great Bird Island have gone up to over 40,000 visitors per year, which has gone up dramatically from only 17,000 visitors per year during the mid 1990s (J. Daltry pers. comm. 2010).There are also well-substantiated reports of snakes being taken as pets (J. Daltry pers. comm. 2010).
This snake was once common in Antigua, but by the twentieth century it had completely disappeared from the island and was thought to be extinct, mainly as a result of the introduction of two species (4). Black and brown rats (Rattus rattus
and Rattus norvegicus
) were accidentally brought to the West Indies on foreign ships from Europe, wreaking havoc on endemic wildlife including the Antiguan racer whose eggs and young were preyed upon (4). Then in the late 19th Century the Asian mongoose (Herpestes javanicus
) was introduced in an effort to control rat populations in sugar cane plantations. These quickly established themselves and systematically drove many species of terrestrial reptiles and ground-nesting birds to extinction or near-extinction, amongst them the Antiguan racer (3). To make matters worse, many Antiguans and visiting tourists wrongly believed the racer to be dangerous, and snakes were often killed on sight (5).
A reintroduction plan was established in 1999 by the Antiguan Racer Conservation Project, which focussed on the subspecies on Great Bird Island. Since then, the Antiguan Racer Conservation Project has eradicated alien mammals from 12 islands and successfully reintroduced the racer to three islands: Rabbit (1999), Green (2002) and York (2008). At present, there are no individuals of this species in captivity (J. Daltry pers. comm. 2010). Continued conservation management, population monitoring and invasive species control are needed to guarantee the species persistence.
In 1989, the believed extinct Antiguan racer was rediscovered on Great Bird Island where it was indeed facing imminent extinction. By 1995, only about 60 racers survived, and most had been severely injured by rats (5). A conservation initiative sprang into action to save this species; Fauna and Flora International, the Antigua Forestry Unit, the Island Resources Foundation, the Durrell Wildlife Conservation Trust, the Environmental Awareness Group and Black Hills State University joined forces to create the Antiguan Racer Conservation Project (2). This award-winning project led to the eradication of rats and mongooses from Great Bird Island and 11 other offshore islands, an extensive study programme, and a very active education initiative for local people and visiting tourists (2). The results were highly successful and in 1999 ten snakes were re-introduced onto another small island that had been cleared of rats (4). The Antiguan racer was also bred in captivity for the first time, although severe problems were encountered (2). In 2002 there were still fewer than 150 Antiguan racers in existence (5), but as a result of the various conservation efforts there are now around 300 in the wild, an impressive six-fold increase (6). However, work remains ongoing, population numbers continue to be monitored and constant vigilance is needed to ensure that rats or mongooses do not return to the islands (4). Now something of a national celebrity, the future is slightly brighter for one of the world's rarest animals.