How to Identify the Phuket Pit Viper (Identification Guide)

Key identifying features

The Phuket Pit Viper is a member of the Asian green pit viper complex (genus Trimeresurus), a group of slender, prehensile-tailed, arboreal vipers found throughout Southeast Asia. Like its relatives, it has a triangular, distinctly heat-pit-bearing head, vertically elliptical pupils, and a body built for climbing through vegetation rather than moving quickly across open ground. Positive identification within this species group typically requires close examination of scale counts and locality, since many green pit vipers look nearly identical at a glance.

Coloration & pattern

The base body color is bright to medium green, occasionally with a faint yellowish or bluish cast, which provides effective camouflage among leaves. A thin white, cream, or pale yellow stripe commonly runs along the lower side of the body, more pronounced or exclusive in males, a pattern typical of the Trimeresurus group. The belly is usually a paler green, yellow-green, or whitish tone. The tail tip often shows a reddish-brown or rust coloration in many members of this species group, contrasting with the green body, though this can vary between individuals.

Head, eyes & scales

The head is broad, flattened, and triangular, clearly distinct from the narrower neck, an adaptation shared by all pit vipers to house venom glands. Heat-sensing pits lie between the eye and nostril on each side. The eyes are relatively large with vertical, cat-like pupils, an easy way to distinguish it and its relatives from harmless green snakes that have round pupils. Body scales are keeled, giving the skin a slightly rough or matte texture rather than the smooth, glossy look of some non-venomous green snakes.

Size & body shape

This is a small to moderate-sized snake, with adults typically reaching roughly 50 to 80 centimeters in total length. The body is slender and laterally compressed, aiding movement through branches, and the tail is prehensile, used to grip stems and twigs while the snake forages or rests coiled in vegetation.

Range & habitat where you'll see it

As its name suggests, this species is closely associated with Phuket and nearby areas of peninsular southern Thailand, where it inhabits lowland and hill forest, forest edges, and sometimes vegetation near human settlements. It is primarily nocturnal and arboreal, often found coiled on low shrubs, vines, or tree branches within a meter or two of the ground, especially near streams or moist forest understory.

How to tell it apart from look-alikes

Separating this species from other green pit vipers in the region (such as Pope's pit viper or the white-lipped pit viper) is difficult without expert examination of scale rows, hemipenal structure, or genetic data, and much of this complex was only resolved taxonomically in recent decades. Range can offer a strong clue, since this species is largely restricted to the Phuket area and nearby peninsular Thailand. Non-venomous green snakes that may be superficially confused with it, such as certain vine snakes or green whip snakes, lack the heat-sensing pits, have round pupils rather than vertical ones, and generally have smoother scales and a more slender, elongated head without the broad triangular shape.