Friday, October 21, 2016

Tobago Racer, Mastigodryas dunni (Family Colubridae)

Size: 776 mm SVL, 881 mm TL, hatchlings 240 mm. Identification: Dorsal scale rows 17 at mid-body, reduced to 15 posteriorly; each scale has a pair of apical pits, otherwise smooth. Rostral visible from above; nasals divide, nostril large; loreal rectangular; one preocular; two or three postoculars;  upper labials 8-10, lower labials 8-10; ventrals 185−196; divided cloacal plate; 119−124 divided subcaudals; eyes exceptionally large. The dorsum is blue-gray, a light, indistinct  stripe present on scale rows 1-2, a more distinct stripe present on rows 4-5, laterally coloration becomes lighter, including light labials; the venter is white-pink with some blotches; the underside of the tail may be flecked with gray. It is likely that the juveniles are blotched with cross bands like M. boddaerti and that the colors change to an blue-gray with maturity. The combination of dorsal scales in 17 rows at mid body, scales with apical pits, a loreal, a vertebral scale row that is not enlarged, and five lower labials in contact with the first chin shield, and two lateral stripes one scale row 1–2 and a second on rows 4–5 should separate the species from all other Trinidad and Tobago snakes, except the other two species of Mastigodryas . The Tropical Racer, M. boddaerti is restricted to Trinidad, but the Yellow-necked Racer, M. amarali, is not confirmed from  the islands. The two may be distinguished by a stripe on the anterior body that spans scale rows 3−4−5 in the Yellow-necked Racer, and only rows 4-5 in this species. Known only from Tobago and Little Tobago Islands. A forest and forest-edge species. Diurnal. Diet probably similar to the Tropical Racer, but it has not been studied.

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