Alsophis antiguae

Status_ne_offStatus_dd_offStatus_lc_offStatus_nt_offStatus_vu_offStatus_en_offStatus_cr_onStatus_ew_offStatus_ex_off

Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA REPTILIA SQUAMATA DIPSADIDAE

Scientific Name: Alsophis antiguae
Species Authority: Schwartz, 1966
Common Name(s):
English Antiguan Racer
Synonym(s):
Alsophis leucomelas subspecies antiguae Schwartz, 1966
Taxonomic Notes: This species has two sub-species:

A. a. antiguae Parker, 1933
A. a. sajdaki
Henderson, 1989

The sub-species Alsophis antiguae sajdaki is thought by some to represent a full species (A. sajdaki; Hedges et al. 2009), which would render A. antiguae extinct; however, there is evidence against this proposition, from a study of more than 400 live specimens from Great Bird Island, so that the consensus remains that A. antiguae is still extant as described in this account (J. Daltry pers. comm. 2010). As a result, the subspecies-level taxonomy is likely to change (J. Daltry pers. comm. 2010).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(iii) ver 3.1
Year Published: 2010
Date Assessed: 2009-06-30
Assessor(s): 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, H.T., Wearn, O.R., Wren, S., Zamin, T., Sears, J., Wilson, P., Lewis, S., Lintott, P. & Powney, G.
Justification:
Alsophis antiguae 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.
History:
1996 Critically Endangered
1994 Endangered (Groombridge 1994)

Geographic Range [top]

Range Description:This species is endemic to the island bank of Antigua and Barbuda, where it once ranged over most of the islands; however only subfossil remains (tentatively attributed to this species) have been found on Barbuda, and the species went extinct from the main island of Antigua shortly after the Asian mongoose (Herpestes javanicus or H. auropunctatus) was introduced at the end of the 19th century (Daltry et al. 2001). The area of distribution for this species has been increased from 8.4 ha to 65 ha (0.1% of its natural range). The snake can be found at all elevations of its current distribution range (up to approximately 30m), but was probably also found at higher elevations on Antigua prior to its extinction on the island (J. Daltry pers. comm. 2010).
Countries:
Native:
Antigua and Barbuda
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: 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: Increasing

Habitat and Ecology [top]

Habitat and Ecology: This species is found in habitats with dense canopy cover, dense undergrowth and a layer of leaf litter.
Systems: Terrestrial

Threats [top]

Major Threat(s): 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).

Conservation Actions [top]

Conservation Actions: 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.

Bibliography [top]

Daltry, J. 2006. The effect of black rat Rattus rattus control on the population of the Antiguan racer snake Alsophis antiguae on Great Bird Island, Antigua. Conservation Evidence 3: 30-32.

Daltry, J.C. 2006. Control of the black rat Rattus rattus for the conservation of the Antiguan racer Alsophis antiguae on Great Bird Island, Antigua. Conservation Evidence 3: 28-29.

Daltry, J.C. 2006. Reintroduction of the critically endangered Antiguan racer Alsophis antiguae to Green Island, Antigua. Conservation Evidence 3: 36-38.

Daltry, J.C. 2006. Reintroduction of the critically endangered Antiguan Racer Alsophis Antiguae to Rabbit Island, Antigua. Conservation Evidence 3: 33-35.

Daltry, J.C., Bloxam, Q., Cooper, G., Day, M., Hartley, J., McRonnie, H., Lindsay, K. and Smith, B. 2001. Five years of conserving the 'worlds rarest snake', the Antiguan racer Alsophis antiguae. Oryx 335(2): 119-127.

Hedges, S.B. 2007. pers. comm. Red List Assessment.

Hedges, S.B. 2010. Caribherp: West Indian amphibians and reptiles. Pennsylvania Available at: www.caribherp.org. (Accessed: 14/07/2010).

Hedges, S.B., Couloux, A. and Vidal, N. 2009. Molecular phylogeny, classification, and biogeography of West Indian racer snakes of the Tribe Alsophiini (Squamata, Dipsadidae, Xenodontinae). Zootaxa 2067: 1-28.

Henderson, R. 1989. A new subspecies of Alsophis antiguae (Serpentes: Colubridae) from Great Bird Island (Antigua), Lesser Antilles. Caribbean Journal of Science 25(3/4): 119-122.

IUCN. 2010. IUCN Red List of Threatened Species (ver. 2010.4). Available at: http://www.iucnredlist.org. (Accessed: 27 October 2010).

Mayer, G.C. 2008. pers. comm. Red List Assessment.


Citation: Daltry, J. & Mayer, G.C. 2010. Alsophis antiguae. In: The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 31 October 2014.
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