Possibly the world's rarest snake, the Antiguan racer is small, non-venomous and good-natured. Unusually amongst snakes, this species shows dramatic sexual dimorphism with the females being much larger in size than the males and possessing almost the opposite colouration; females are a silvery-grey colour with pale brown blotches and stripes, whereas the males are dark brown with creamy blotches (2).
The Antiguan racer is strictly diurnal(2), remaining active in the heat of the day but often seeking out dense vegetation to provide shade (4). Adults feed primarily on anole lizards (Anolis species) that are caught by ambush, lying in wait camouflaged beneath a thin layer of leaf litter with only their heads protruding (2). The main predators of the Antiguan racer are introduced rats and mongooses.
Originally distributed throughout Antigua and Barbuda, in the West Indies. By the late 20th Century, it was found only on Great Bird Island off the northeast coast of Antigua (2). A re-introduction programme is underway to restore this species to parts of its original range (3).
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 small Indian 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 (5). To make matters worse, many Antiguans and visiting tourists wrongly believed the racer to be dangerous, and snakes were often killed on sight (3).
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 (3). 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 (3), 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.
To learn more about a Whitley Award-winning conservation project for this species, click here.
Daltry, J.C., Bloxam, Q., Cooper, G., Day, M.L., Hartley, J., McRonnie, H., Lindsay, K. and Smith, B.E. (2001) Five years of conserving the 'world's rarest snake', the Antiguan racer Alsophis antiguae. Oryx, 35(2): 119 - 127.
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