Boiga andamanensis

Boiga andamanensis (Wall, 1909)

(Tables 3–4; Fig. 8, 9F)

Dipsadomorphus andamanensis Wall, 1909

Dipsas andamanesnsis — Das et al. (1998) (sic)

Boiga andamanensis — Smith 1943

Taxonomic history. This species was originally described as Dipsadomorphus andamanensis based on a series of six syntypes, originating from the Andaman Islands, deposited at the Indian Museum, Calcutta, Bengal (now, Zoological Survey of India, Kolkata). As in the case of B. beddomei, Wall (1909) described this species whilst revising the B. ceylonensis group. However, this species has not been a subject of taxonomic confusion ever since (but see Deraniyagala, 1955), probably because of its allopatric distribution.

Specimens examined. India. Andaman Islands.

Syntypes: ZSI 15189 (an adult male), ZSI 7928–7930, ZSI 8641, ZSI 15142 (unsexed juveniles) all from the Andamans.

Other specimens: Male (n=1) ANFD unreg. Female (n=1) CIARI unreg. from Andaman Islands, India.

Etymology. Toponym, named after its distribution in the Andaman Islands, Bay of Bengal.

Diagnosis. A species of Boiga endemic to the Andaman Islands of the Bay of Bengal, India, characterized by: 21 scale rows at midbody (vs. 19 in B. ceylonensis, B. thackerayi, B. barnesii, B. beddomei and B. flaviviridis; up to 23 in B. nuchalis, B. dightoni); reddish/brownish to pale greenish dorsum (vs. yellowish-brown in B. thackerayi; always brownish in B. beddomei, B. ceylonensis, B. dightoni, B. nuchalis and B. barnesii; always greenish in B. flaviviridis); preocular 1 (vs. 3 in B. barnesii); ventral and ventro-lateral region completely lacking pattern (vs. with white and black adjacent blotches in B. barnesii, B. thackerayi; spotted in B. beddomei, B. ceylonensis, B. nuchalis, B. dightoni).

Redescription of the largest syntype (ZSI 15189). An adult male measuring 1028 mm total length, with an SVL of 795 mm and tail length of 233 mm. Overall habitus slender, mandible slightly damaged on both the sides; a small lateral compression and loss of tissues at midbody. Head large and considerably wider than the thin neck; Scalerows 21:21:17; vertebrals relatively enlarged; rostral not visible from above; internasals shorter than preforntals; parietals much broader and longer than other cephalic scales; supraoculars and preoculars elongate; preoculars mildly visible from above; loreal single; much smaller than preoculars and nasals. Nostril in the middle of an elongate nasal; postoculars 2, small; 8 supralabials (3 rd to 5 th entering orbit), the last one largest; 10–11 infralabials (the first six in contact with genials); temporals 3+2/3+2/3; preventral single; ventrals 268; subcaudals 133 pairs. Colouration in preservative completely faded and bleached, uniform pale creamy white both dorsally and ventrally, without any pattern; body with brownish borders along some scales; eye of a similar colour, pupil barely discernale; tail slightly darker.

Variation shown by other syntypes and referred material. Agreeing with the lectotype in most aspects and showing the following intrasepcific variations: scalerows: 21:21:15-17; SVL 1060–1340 mm; tail 295–375 mm; juveniles: SVL 245–382 mm; tail: 92–117 mm; ventrals 255–267; subcaudals 102–127. Dorsal colouration variable from bright coral red to brown or olive green, with or without black crossbars across the body and tail. Head unpatterned dorsally; ventrals usually a paler hue than the dorsal colour, completely lacking pattern.

Distribution and natural history. Restricted to islands of the Andaman Archipelago, in the Bay of Bengal. Not found in the Nicobar Islands or elsewhere (Fig. 13). Boiga andamanensis is nocturnal and is often seen after dusk, along low lying bushes and shrubs, foraging for lizards (especially of the genus Coryphophylax) and frogs (pers. obs.).