How to Identify the White-Lipped Island Pit Viper (Identification Guide)

Key identifying features

The White-Lipped Island Pit Viper is a green arboreal pit viper distinguished by a clean white or pale yellow line running along the upper lip, contrasting sharply against the green head. This lip stripe, combined with the standard pit viper features of a triangular head, heat pits, and vertical pupils, makes it relatively recognizable among green pit vipers when seen well.

Coloration & pattern

The body is a bright to medium green, sometimes with a slight blue or yellow tint, offering camouflage among leaves. The defining white lip stripe runs along the edge of the upper jaw and often continues as a pale lateral line down the length of the body, particularly in males. The tail frequently shows a reddish-brown tint near the tip, a common trait across many green pit viper species. The belly is generally pale green or whitish.

Head, eyes & scales

The head is broad and triangular, clearly distinguished from the neck, with a heat-sensing pit between each eye and nostril. The white or cream lip line is one of the most noticeable facial features, standing out clearly against the green head scales. The eyes have vertical pupils and are moderately large. Dorsal scales are keeled, producing a slightly textured, matte body surface.

Size & body shape

This species is small to moderate in size, with adults typically reaching around 50 to 80 centimeters. The body is slender and laterally compressed, well suited to climbing through shrubs and low trees, with a prehensile tail for gripping branches.

Range & habitat where you'll see it

As suggested by its name, this species is associated with island habitats, generally in coastal or insular forest settings within its native range. It favors shrubby vegetation, forest edges, and low branches near the ground, and like most green pit vipers is largely nocturnal, most often seen at night coiled on vegetation.

How to tell it apart from look-alikes

The combination of a clear white or pale upper lip stripe against a green head is the most useful single field mark for this species, since many related green pit vipers either lack this stripe or show a less distinct version. Range and island locality further help confirm identification. As always, the broad triangular head, vertical pupils, facial heat pits, and keeled scales distinguish any pit viper, including this one, from harmless green snakes lacking these traits.