Pseudalsophis biserialis 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Dipsadidae

Scientific Name: Pseudalsophis biserialis (Günther, 1860)
Common Name(s):
English Galapagos Racer, Galápagos Racer
Alsophis biserialis (Günther, 1860)
Herpetodryas biserialis Günther, 1860
Taxonomic Notes: Zaher (1999) recognized Philodryas dorsalis and P. occidentalis as species distinct from P. biserialis; this action - which was not in a paper primarily concerned with taxonomy - appears to have subsequently been neglected, however, the taxonomic action appears not to have been disputed and Zaher et al. (2009) listed all three taxa within the newly-erected genusPseudalsophis without comment. This arrangement is consequently followed here.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2017
Date Assessed: 2014-01-26
Assessor(s): Márquez, C., Cisneros-Heredia, D.F. & Yánez-Muñoz, M.
Reviewer(s): Bowles, P.
Contributor(s): Hanson, S.
Facilitator/Compiler(s): NatureServe
Listed as Near Threatened on the basis that this species survives on a single island (with an area of 557 km2) and two small islets treated as a single location defined by the presence of invasive predators, however, while it is uncommon it is not clear that there is a decline in the number of mature individuals within its surviving range and, being highly tolerant of habitat modification, it is not considered to be undergoing a continuing decline in the extent or quality of its habitat. As such it is close to qualifying for a threatened listing applying criterion B1.

Geographic Range [top]

Range Description:This snake is endemic to the Galápagos Islands, where it is only known to survive on San Cristobal and the islets Champion and Gardner (Thomas 1997); it was formerly known from Floreana, based on a single specimen with a catalogue number 1946 and apparently collected in the early 1900s, with which the islets are associated, but was not recorded in a survey in 1905-1906 and is no longer considered to be extant here as it has not been recorded in surveys on this island for many decades (Van den Burgh 1912, C. Marquez unpubl. data). This species occurs from sea level to around 730 m asl.
Countries occurrence:
Ecuador (Galápagos)
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is encountered frequently in low numbers (C. Marquez unpubl. data); between 2009 and 2011 it has been encountered at frequencies of around 2-3 individuals per locality, with no evidence of decline (D. Cisneros-Heredia unpubl. data). With such low abundance, however, any declines may simply be difficult to detect (D. Cisneros-Heredia pers. comm.). Van den Burgh (1912) also reported that the species occurred in low numbers on the island. There is no enough information to know if the two subpopulations are disjunct (D. Cisneros-Heredia pers. comm. 2016).
Current Population Trend:Unknown
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:This species occurs in a range of habitats in San Cristobal's dry lowlands, including gardens of the capital, forests and shrubland, as well as on rocks on the beach. At higher elevations, where the climate is more humid, it is found in native vegetation. The highlands have however been subject to fewer surveys than lower elevations, and it may also occur in disturbed habitats here but have gone undetected (D. Cisneros-Heredia pers. comm. 2014).

Use and Trade [top]

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

Threats [top]

Major Threat(s): The species is thought to have been driven to extinction on Floreana by introduced predators, as several other reptiles and birds have also been lost from this island following introductions and the only surviving subpopulations of this snake in the region are on two islets where exotic species are absent. San Cristobal is a much larger island than Floreana, and the species is still frequently found in low numbers despite long co-existence with introduced rats and cats. Other species that have been lost from Floreana are, however, still in decline on islands where they survive even in areas where introduced predators ,have been present for over a century, and it is possible that declines are ongoing in this snake but have gone undetected. While it adapts well to disturbed areas, it is commonly found as roadkill in the lowlands (D. Cisneros-Heredia, M. Yanez-Munoz and C. Marquez pers. obs.), as roads bisect its habitat. (Wiedenfeld and Jiménez-Uzcátegui 2008)

Conservation Actions [top]

Conservation Actions: This species is endemic to the Galápagos National Park. More research is needed to clarify the population status of this species and to determine whether it is at risk from established exotic species, the eradication of which is not feasible from San Cristobal.

Citation: Márquez, C., Cisneros-Heredia, D.F. & Yánez-Muñoz, M. 2017. Pseudalsophis biserialis. The IUCN Red List of Threatened Species 2017: e.T190541A56253872. . Downloaded on 25 June 2018.
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