A comparison of Dipsas trinitatis (A
and c) and Dipsas variegata (B and D).
Thirty six species of the snail-eating snakes in the genus Dipsas are currently recognized. One species, Dipsas trinitatis Parker is known only from Trinidad. The original description of Dipsas trinitatis (Parker, 1926) was based upon a single male specimen from the Trinity Hills and a second specimen without locality data. Parker recognized its close relationship to the mainland South American Dipsas variegata and distinguished the two species using the presence/absence of a preocular, the number of upper labials, and differences in color pattern, characters now known to be variable in both taxa. In an overall review of dipsadine snakes Peters (1960) relegated D. trinitatis to a subspecies of D. variegata based on color differences from the mainland populations. Emsley (1977), Murphy (1997) and Boos (2001) followed this recommendation and discussed this snake as D. v. trinitatis.
Until now, all references to Dipsas on Trinidad have referred to Dipsas trinitatis Parker. Murphy and Rutherford (2014) have now report the presence of Dipsas variegata on Trinidad. Its presence is based upon a single female specimen, identified as Dipsas trinitatis, was found in the collection of The National Museum and Art Gallery of Trinidad & Tobago and now stored in The University of the West Indies Zoology Museum (UWIZM). Its large size (796 mm total length, 607 mm SVL), bulky head, tall upper labials, an eye diameter that is about equal to the eye-mouth distance readily distinguish it from its congener, Dipsas trinitatis. The specimen agrees well with all 16 diagnostic characters for the species listed by Harvey and Embert (2008).
Collection data accompanying the specimen reports it locality as Macqueripe Bay on the north coast of the Chaguaramas Peninsula and adjacent to Tucker Valley.
The smaller head in D. trinitatis has been noted previously, but placed side-by-side the size difference is dramatic and it appears Dipsas variegata is macrocephalic, while D. trinitatis is microcephalic. Microcephalism evolved in several sea snakes (Hydrophis, family Elapidae, Hydrophiinae) that specialize in hunting snake eels in crevices. The smaller head allows the snake to probe holes and crevices to extract the fish. Since Dipsas feeds on snails and extracts them from their shells it seems probable that the difference in head size is adaptive for a specific type of prey, or a specific foraging strategy (possibly removing snail bodies from shells of different sizes or extracting snails from crevices). Feeding behavior and diet in these snakes is poorly known it is unclear as to how head size relates to diet or foraging.
Dipsas variegata is the 44th species of snake reported from Trinidad and the second species of Dipsas from the island. In addition there is a third species of snake specialized for feeding on gastropods from Trinidad – Sibon nebulata.
Murphy JC, Rutherford, MG. 2014. The snail-eating snake Dipsas variegata (Duméril, Bibron and Duméril) on Trinidad, and its relationship to the microcephalic Dipsas trinitatis Parker (Squamata, Dipsadidae). Herpetology Notes, 7: 757-760.