How to Identify the Bornean Pit Viper (Identification Guide)
A guide to recognizing the Bornean Pit Viper by its triangular head, heat-sensing pits, keeled scales, and green to brownish coloration in Bornean rainforests.
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Key identifying features
The Bornean Pit Viper (referring to Trimeresurus borneensis and related species endemic to Borneo) is a venomous pit viper identifiable by its broad, triangular head, heat-sensing facial pits, vertically elliptical pupils, and rough keeled scales, adapted for life in the dense rainforests of Borneo.
Coloration & pattern
Coloration is often green to olive-green, sometimes with a bluish or yellowish tinge, and may include faint darker speckling or a thin pale lateral stripe along the lower flank. Some individuals show more brownish tones, particularly those found closer to the forest floor, providing camouflage suited to their specific microhabitat, whether in the canopy or leaf litter.
Head, eyes & scales
The head is broad, triangular, and clearly distinct from the neck, housing venom glands typical of pit vipers, with a heat-sensing pit located between each eye and nostril. The eyes have vertical, cat-like pupils, and the scales are keeled, giving the body a rough, matte texture rather than a smooth or glossy one.
Size & body shape
This species is small to medium, generally reaching 50–90 cm (20–35 inches), with a moderately stout body suited to slow, deliberate arboreal or semi-arboreal movement, and a tail capable of gripping branches for stability while climbing.
Range & habitat where you'll see it
The Bornean Pit Viper is found across the island of Borneo, inhabiting lowland to montane rainforest, often near streams, forest edges, and dense vegetation. It is primarily nocturnal, frequently found coiled on low branches, shrubs, or vegetation near water at night.
How to tell it apart from look-alikes
The combination of a broad triangular head, heat-sensing pits, and vertical pupils separates it from non-venomous green tree snakes found in the same habitat, which have narrower heads and round pupils. Distinguishing it from other closely related Bornean and Southeast Asian pit vipers often requires attention to fine scale counts, precise coloration, and locality, but the general pit viper body plan—rough keeled scales and a heat-pit-equipped triangular head—is the most immediate identification clue.
Frequently asked questions
Is the Bornean Pit Viper venomous?
Yes, it is a venomous pit viper native to Borneo's rainforests.
How can I tell it apart from a non-venomous green tree snake?
Look for the broad triangular head, heat-sensing facial pits, and vertical pupils, which non-venomous tree snakes lack.
Where does the Bornean Pit Viper live?
It is found throughout Borneo in lowland to montane rainforest, often near streams and dense vegetation.
What time of day is it most active?
It is primarily nocturnal, often seen coiled on low branches or vegetation at night.
What color is this species typically?
It is commonly green to olive-green, sometimes with bluish or yellowish tinges, though some individuals show more brownish tones.