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Alsophis sanctonum 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Dipsadidae

Scientific Name: Alsophis sanctonum Barbour, 1915
Common Name(s):
English Terre-de-Haut Racer
Synonym(s):
Alsophis antillensis ssp. sanctonum Barbour, 1915
Taxonomic Notes: This species has two subspecies:
A. sanctonum sanctonum Barbour, 1915
A. sanctonum danforthi Cochran, 1938.

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(iii) ver 3.1
Year Published: 2017
Date Assessed: 2015-07-21
Assessor(s): Gomès, R., Dewynter, M., Powell, R., Hedges, B. & Mayer, G.C.
Reviewer(s): Bowles, P.
Contributor(s): 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. & Hedges, B.
Facilitator/Compiler(s): NatureServe
Justification:
This species is restricted to three islands (each treated here as a separate location) with a combined surface area of around 16 km2; as the species is rare or absent in degraded parts of Terre-de-Haut, its true area of occupancy is expected to be somewhat lower, and is estimated to be below 10 km2. Ongoing threats exist from localized development and more widely from the action of introduced species; as these are leading to declines in the quality and extent of the species' habitat it qualifies for listing as Endangered under criterion B. Additionally it is at extreme risk from the potential introduction of mongoose, which would lead to catastrophic and likely immediate declines and the species' probable extinction. Imports of exotic species to these islands, which form part of the same political unit as Guadeloupe, are not presently regulated, and this therefore represents a highly plausible future threat.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is endemic to Terre-de-Bas and Terre-de-Haut; these islets make up the Îles de Saintes, part of Guadeloupe. Terre-de-Bas and Terre-de-Haut are very small islands with a combined total area of approximately 16 km². It has also been recorded from Îlet Cabris (Breuil 2009). The islands have a maximum elevation of 260 m, and the species occurs throughout the islands.
Countries occurrence:
Native:
Guadeloupe
Additional data:
Estimated area of occupancy (AOO) - km2:9
Number of Locations:3
Upper elevation limit (metres):260
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species seems to be common on the two larger islands; on Terre-de-Bas it is found across the island, while on Terre-de-Haut it has a more fragmentary distribution (R. Gomès pers. comm. 2015). Nevertheless snake densities are thought to be much lower than previously believed, as densities vary greatly by location and time of year rather than being uniform (R. Gomès pers. comm. 2015). No studies have been carried out into population dynamics in this species, and interviews with people who have worked within its range for 30 years and are familiar with the species suggest that it occurs at lower densities than in the past (R. Gomès pers. comm. 2016). On the latter island it is associated with less disturbed, wooded areas, where it is common, but it is very rare elsewhere (R. Gomès pers. comm. 2015). There is no information about its status on Îlet Cabris.
Current Population Trend:Unknown
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This species occurs along mangrove edges and roadsides, and in gardens and wooded areas (preferentially in semi-deciduous forest with Pimenta racemosa, Pisonia subcordata, Hymenea courbaril, and Bursera simaruba). Although the species has been found in various habitats, it prefers areas less frequented by humans (Breuil 2002).
Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: There is no known use or trade in this species.

Threats [top]

Major Threat(s): This species may be threatened by habitat loss due to urban development, particularly for the tourist industry, but development presently appears to be highly localized on these islands based on satellite imagery. At present development is only ongoing on Terre-de-Haut, but tourist developments have been proposed for Terre-de-Bas (R. Gomès pers. comm. 2015). Much of the forest on Terre-de-Haut has nonetheless been lost or heavily degraded as a result of overgrazing by goats. Goat densities are extremely high in the Les Saintes archipelago, where thousands of feral animals prevent forest regeneration at least at low elevations (R. Gomès pers. comm. 2016).  This species is very rarely found in the resulting habitats as the resulting soil erosion and reduction in leaf litter destroys suitable ground cover for the snake and habitat for the its prey (R. Gomès pers. comm. 2015). Observations based on following individual snakes suggest that animals may now struggle to find sufficient prey due to this reduction in leaf litter quality (R. Gomès pers. comm. 2016).

Rats are present on the islands and are a known threat to other species of Alsophis (Breuil 2002). Feral chickens may feed on juveniles, which occur in lower densities where these are present (R. Gomès pers. comm. 2015). As with other species of snake, this species is at serious risk of extinction should human traffic between islands introduce mongoose, which have resulted in massive declines and extinctions of other Caribbean reptiles including other species of Alsophis. The islets lie close to Guadeloupe and, being part of the same French territory, no import controls exist. Mongoose introduction is therefore a real risk in the near future especially if tourist development results in increased numbers of visitors. Human persecution is a less significant issue for this species than others, as locals on the islands are aware that this snake is harmless, however, increasing tourist numbers on Terre-de-Haut are likely to bring the snake into contact with people unaware that the animal is inoffensive (R. Gomès pers. comm. 2015).

Conservation Actions [top]

Conservation Actions: This species currently has no conservation measures in place for it. The major part of its range on Terre-de-Haut lies within the Morne due Chameau biotope, which has national protection prohibiting urban development (R. Gomès pers. comm. 2015). This protection does not, however, effectively prevent predation by stray pets or tree cutting. Îlet Cabrit is a conservation management area, but feral goats and chickens are widespread on this small island and their numbers are not thought to be effectively managed (R. Gomès pers. comm. 2015). Better enforcement of existing regulations at both sites is recommended to assist the conservation of this species (R. Gomès pers. comm. 2015).

The establishment and management of new protected areas could provide a safeguard for this species from habitat loss, and establishing controls to prevent the introduction of mongoose is a priority.

Citation: Gomès, R., Dewynter, M., Powell, R., Hedges, B. & Mayer, G.C. 2017. Alsophis sanctonum. The IUCN Red List of Threatened Species 2017: e.T176330A71742582. . Downloaded on 20 October 2017.
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