Dendrelaphis ngansonensis

This snake is found in Thailand but not in Bangkok

English name: Nganson Bronzeback (aka: “Vietnamese Bronzeback”)
Scientific name: Dendrelaphis ngansonensis
Thai name: งูสายม่านเวียตนาม (Ngu Sai Man Vietnam)

Description: To 150cm long. Large and relatively robust for a Bronzeback. Body is brown with various indistinct brown mottling, showing bright blue skin between the scales when disturbed. Head is brown with a thick black eyestripe that extends out a short distance past the neck. Eye is fairly large. Belly is light yellow to cream or tan.

Relevant scale counts: 15 rows of midbody scales with enlarged vertebral scales. 180-199 ventrals and 126-153 subcaudals.

Similar Species: Painted Bronzeback is less robust, lacks brown mottling, and has a distinct dorsolateral stripe.
Blue Bronzeback is less robust, has more distinct blue on flanks, is brighter in color below, and lacks the brown mottling.
Banded Bronzeback has a yellowish neck (most visible when inflated), distinct slanted black bars on forebody, and lacks the brown mottling.

Range: From southern China south through Laos, Vietnam, Cambodia, and into east-central Thailand.

Habitat: Forests up to 1500m, often in trees.

Contribution to the ecosystem: Likely feeds on lizards and frogs as other Bronzebacks. Would be eaten by birds of prey and larger snakes.

Danger to humans: This species is not dangerous to humans.

Conservation status and threats: No known conservation issues, though it is seen less often than several other Bronzebacks.

Interesting facts: The Nganson Bronzeback was thought to be a Vietnamese subspecies of Painted Bronzeback until 1999, when Thomas Ziegler and Gernot Vogel elevated it to full species status. They found that species status, and not subspecies, was warranted due to clear differences in coloration, size, and ventral scale counts between the two snakes as well as the fact that they occur sympatrically (in the same area) over much of their range, which would not be viable if they were two subspecies within a single species. Since that period it has been found to occupy a much broader range across five countries, and is actually most closely related to the Blue Bronzeback.

References:
Ecology Asia: Nganson Bronzeback
On the Knowledge and Specific Status of Dendrelaphis ngansonensis
Gernot Vogel pers. comm.
A new species of the genus Dendrelaphis from Yunnan Province China