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Typhlops tasymicris

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA REPTILIA SQUAMATA TYPHLOPIDAE

Scientific Name: Typhlops tasymicris
Species Authority: Thomas, 1974
Common Name(s):
English Grenada Bank Blindsnake

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(iii) ver 3.1
Year Published: 2011
Date Assessed: 2011-01-26
Assessor(s): Powell, R. & Henderson, R.W.
Reviewer(s): Hedges, B. & Bowles, P.
Justification:
Listed as Endangered on the basis that it has a known extent of occurrence of 156 km², and a true extent of occurrence certainly considerably less than 5,000 km², it is known from three locations, and there is a continuing decline in the extent and quality of its habitat throughout its range, as well as potentially in its extent of occurrence and area of occupancy. Research is urgently required to establish whether this snake survives on Grenada as, if the species is found to be extinct on that island, it would immediately require reassessment as Critically Endangered.

Geographic Range [top]

Range Description: Until recently, this species was known only from two specimens, collected at St. David Parish and St. Andrew Parish, Grenada in 1968. These sites are less than 20 km apart. The snake was rediscovered in 2010 on the slopes above Chatham Bay on Union Island, St. Vincent and the Grenadines (Quinn et al. 2010, Rivera Rodríguez et al. 2011). Although searches have been conducted on other islands, they have to date revealed no evidence of other populations. The species has been reported from sea level to 179 m asl.

It is unlikely that more than 50% of the land area on Grenada supports suitable habitat for this species, and it is expected to be restricted to the vicinity of Chatham Bay on Union Island. Based on this, the species has an estimated maximum extent of occurrence of 156 km². Its area of occupancy is unknown, although the extent of habitat believed to be capable of supporting this species in Chatham Bay is as small as 0.523 km² (see Bentz et al. 2011).
Countries:
Native:
Saint Vincent and the Grenadines
Possibly extinct:
Grenada
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This species is known from two specimens collected from Grenada in 1968, and from five individuals recently found on Union Island (Bentz et al. 2011, Rivera Rodriguez et al. 2011). The status of these subpopulations is difficult to assess as a result of the small number of captures, reflecting the difficulty of finding fossorial blindsnakes. Extensive surveys and interviews with local inhabitants targeted at relocating this species in Grenada have been unsuccessful. Due to high rates of deforestation on this island and pressure on and between the two known sites where this species was known to occur, the Grenada subpopulation is at least severely fragmented, and is possibly extinct.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: On Union Island these minute snakes inhabit leaf litter in subtropical/tropical dry forests with rocky areas (Rivera Rodríguez et al. 2011, Bentz et al. 2011); some introduced vegetation (mango trees, annual grasses along the road) is present but this area remains one of the very few relatively intact secondary dry forests on the island and in the entire Grenadine chain. The two individuals from Grenada were found in areas then characterized by moist lowland and hillside forest, and in mixed plantations (cacao, mango and nutmeg) (Wallach 2000, Yorks et al. 2003, Thomas 1974). While the known habitats are varied and the species exhibits some ability to tolerate agricultural disturbance, all recorded individuals have been found in shaded habitats with trees and thick leaf litter. In captive experiments individuals preferentially burrowed into the substrate to avoid extremes of temperature, suggesting that they are reliant on a deep litter layer. When near the surface, they have been found beneath moisture-retaining cover objects such as rocks and a termite mound (Rivera Rodriguez et al. 2011, Bentz et al. 2011). In common with other leaf litter-associated blindsnakes, this species is unlikely to survive in unshaded, deforested or intensively-cultivated areas where soil is exposed.
Systems: Terrestrial

Use and Trade [top]

Use and Trade: This species is not subjected to any commercial exploitation.

Threats [top]

Major Threat(s): By 2001, 70% of Grenada's forests had been lost, and both sites where this species was found are subject to intensive human use. The shaded habitats that existed at these localities when the species was recorded were destroyed by Hurricane Ivan in 2004, and have since been converted to cropland. When this species was discovered, an airport and active archaeological digs were in operation at one site, and while these activities have since ceased the associated infrastructure provides ready access to this area, facilitating human settlement. The creation and expansion of villages and their associated agriculture have increased dramatically since the 1990s. Although orchards in some parts of its presumed Grenada range may provide refuges for this species, any surviving subpopulations in this part of Grenada will be isolated from one another by intensively-farmed cropland. The vulnerability of these snakes to agricultural effluents (herbicides and pesticides) is unknown.

On Union Island, this species occurs in a small area of forest that was protected from agricultural development by its historical inaccessibility. The construction of a road in 2005 has, however, opened up this area, which is at imminent risk from further development. There are plans to extend the road through the heart of the Chatham Bay site, which would destroy much of the litter cover that represents critical habitat for this snake. Land clearance along the slope for housing and agriculture is already underway in the northeast of the bay (Bentz et al. 2011), and the construction and upslope expansion of tourist facilities threatens to place additional pressure on this area. The introduction of exotic mammals, particularly feral goats which destroy understorey vegetation and cats which are known to prey on small reptiles, also represents a severe threat to this species (Bentz et al. 2011).

Conservation Actions [top]

Conservation Actions: Chatham Bay protects the most important watershed on Union Island, and measures are needed to preserve and manage the forest to ensure the integrity of both this and the area’s biodiversity, including the Grenada Bank Blindsnake. This species' habitat on the island has been identified by local NGOs and the national Forestry Department as a site of conservation importance, but these groups currently lack the means to enforce its protection. In the long term, this site should probably be preserved as a national protected area. As the minimum measures necessary to safeguard this species and its habitat in the immediate future, resort construction should be confined to the beach and road construction diverted to lower elevations where it will not threaten critical habitat for this species (Bentz et al. 2011). Control of feral mammals should be implemented to mitigate their adverse impacts.

Research is needed as a matter of urgency to establish whether this species survives on Grenada, and if so whether it occurs more widely than historical records suggest. Other stands of forest and forest/mixed plantation agriculture on Grenada and in the Grenadines should continue to be surveyed for the presence of these snakes (Johnson 1988, Henderson and Powell 2009). Research is needed into the population size, distribution and natural history of the Union Island population, and into this snake's sensitivity to threatening processes. Unless new data reveals that this snake is more abundant and widely-distributed than is currently recognized, it should be the target of species-specific legislation aimed at its preservation.

Citation: Powell, R. & Henderson, R.W. 2011. Typhlops tasymicris. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 28 July 2014.
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