Friday, June 24, 2011

Trinidad's Snail-eating Snake

The Snail-eating Snake, Dipsas trinitatis. This specimen was found
crossing the Arima Valley Road.
H. W. Parker described Dipsas trinitatis from a single specimen collected in Trinity Hill Reserve, Trinidad in 1926 and recognized its close relationship to the Venezuelan D. variegata. He distinguished the two species on the basis of presence or absence of a preocular, the number of upper labials, and differences in color pattern. In 1960 James Peters recognized trinitatis as a subspecies of D. variegata based solely on color. Cadle et al. (2003) showed the two forms are similar in scale counts and color pattern and note that D. v. trinitatis has a smaller head in relation to the body and fewer maxillary teeth than does D. v. variegata, but considered the Trinidad population a subspecies of D. variegata. Dipsas trinitatis was removed from the synonymy of Dipsas variegata by Harvey and Embret (2008) on the basis of distinctive morphology and its allopatric distribution. D. trinitatis can be distinguished from D. variegata by fewer (7-9) maxillary teeth, the lack of sublabials (scales between the labials and chin shields), and the lower labials contact the third pair of chin shields on one or both sides of all specimens. Specimens with two pairs of chin shields the lower labials contact the fused single scale where the third pair would be. Emsley (1977) suggested that its apparent rarity was due to its crepuscular activity and cryptic habits. I observed this snake relatively frequently in the Arima Valley and occasionally at other locations on the island in the 1980’s, but failed to find it during several  trips made ten years later. On my current trip a specimen of the snake was encountered during a heavy rain storm, about 0100 hours in the Arima Valley (photo). Friends report that they see this snake in low bushes in the early evening, probably hunting snails.

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