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Alsophis antiguae 

Scope: Global
Language: English
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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 ssp. antiguae Schwartz, 1966
Taxonomic Notes: The subspecies Alsophis antiguae sajdaki is thought by some to represent a full species (Hedges et al. 2009), which would render A. antiguae extinct. There is however evidence against this proposition from a study of more than 400 live specimens from Great Bird Island which concluded that, apart from some geographical variation in ventral counts, the proposed diagnostic characters represented sexual dimorphism. On this basis this account considers that A. antiguae is still extant, represented by the surviving form A. a. sadjaki (J. Daltry pers. comm. 2010, 2015).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(v) ver 3.1
Year Published: 2016
Date Assessed: 2015-07-20
Assessor(s): Daltry, J. & Mayer, G.C.
Reviewer(s): Bowles, P.
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. & Hanson, S.
Facilitator/Compiler(s): NatureServe
Justification:
Alsophis antiguae has been assessed as Critically Endangered. This species was historically lost from Antigua due to the introduction of mongoose, and probably from Barbuda for unknown reasons, and reduced to a single population that until recently survived only on Great Bird Island. Since 1995, the Offshore Islands Conservation Programme has led a reintroduction programme, and there are now populations on Rabbit, Green, and York islands, with the global population exceeding 1,100. 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.
Previously published Red List assessments:

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 became extinct on the main island of Antigua shortly after the Small Asian Mongoose was introduced at the end of the 19th century (Daltry et al. 2001), surviving only on Great Bird Island. The distributional extent of this species has been increased from 8.4 ha to 65 ha (0.1% of its natural range) following reintroduction of the Great Bird Island population (Alsophis antiguae sadjaki) to three outlying islands. The snake can be found at all elevations (up to approximately 30 m), but was probably also found at higher elevations on Antigua prior to its extinction on the island (J. Daltry pers. comm. 2010).
Countries occurrence:
Native:
Antigua and Barbuda
Additional data:
Number of Locations:3
Upper elevation limit (metres):30
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:In 1995, J. Daltry demonstrated that the population on Great Bird Island numbered 50 +/- 7 individuals. Since reintroductions to Rabbit, Green and York Islands the population now exceeds 1,100, as of a 2015 census of the global population using mark-recapture methods (J. Daltry pers. comm. 2015).
Current Population Trend:Increasing
Additional data:
Continuing decline of mature individuals:Yes
Population severely fragmented:Yes

Habitat and Ecology [top]

Habitat and Ecology:This species is found in habitats with dense undergrowth; the surviving population is found in an area characterized largely by littoral dry forest and scrub. Historically the species presumably occurred in wetter habitats on mainland Antigua.
Systems:Terrestrial

Use and Trade [top]

Use and Trade: As a rare species this snake may be of interest to the pet trade, and both domestic use as pets and smuggling have been recorded (Offshore Islands Conservation Programme).

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 and its extinction on Antigua. Although some of 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 have confirmed the species to be critically inbred (S. Funk, unpubl. data, Daltry et al. in review), and fertility is low.

Hurricanes can cause flooding on the lowland areas of the island. J. Daltry (pers. comm. 2010) 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 60,000 visitors per year, which has gone up dramatically from only 17,000 visitors per year during the mid 1990s (J. Daltry pers. comm. 2015).There are also well-substantiated reports of snakes being taken as pets (Daltry et al. in review).

Conservation Actions [top]

Conservation Actions: A reintroduction plan was established in 1999 by the Antiguan Racer Conservation Project. Since then, the Antiguan Racer Conservation Project (now renamed the Offshore Islands Conservation Programme) has eradicated alien mammals from 15 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. The species was formally granted national protected status in 2015.

Citation: Daltry, J. & Mayer, G.C. 2016. Alsophis antiguae. The IUCN Red List of Threatened Species 2016: e.T939A71739009. . Downloaded on 09 December 2016.
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