How to Identify the Large-Eyed Pit Viper (Identification Guide)
A venomous arboreal pit viper of South and Southeast Asia, distinguished by its notably large eyes, slender green or brown body, and heat-sensing facial pits.
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Key identifying features
The Large-Eyed Pit Viper (Trimeresurus macrops) is a venomous arboreal pit viper found across parts of South and Southeast Asia, named for its unusually large eyes relative to head size compared to other pit vipers. It has a broad, triangular head, heat-sensing pits, and a slender body suited to life in trees and shrubs.
Coloration & pattern
The body is typically bright green, sometimes with a yellowish or bluish tinge, and may show a thin white or yellow lateral stripe running along the lower sides in some individuals. Faint darker speckling or crossbands may be present but are often subtle against the green background. The belly is usually pale green, yellow, or cream.
Head, eyes & scales
The head is broad and triangular, clearly distinct from the neck. Its defining feature is the large, prominent eyes, noticeably bigger than those of many related pit vipers, often with a golden, reddish, or coppery iris and vertically elliptical pupils. Heat-sensing pits are located between the eye and nostril on each side. Scales are keeled, giving a slightly rough texture.
Size & body shape
Adults typically reach 60 to 90 cm (24 to 35 inches) in length. The body is slender with a prehensile tail, adapted for climbing and gripping branches in forest and shrub vegetation.
Range & habitat where you'll see it
This species occurs in forests, plantations, and shrublands across parts of Southeast Asia, including Thailand, Cambodia, Laos, and Vietnam. It is arboreal and nocturnal, typically found coiled on low branches, shrubs, or vegetation near forest edges and streams.
How to tell it apart from look-alikes
The unusually large, prominent eyes are the most distinctive feature separating this species from other green pit vipers in the region, such as the Sri Lankan Green Pit Viper or Brown-Spotted Pit Viper, which have proportionally smaller eyes. Its triangular head, heat-sensing pits, and vertical pupils distinguish it from harmless green vine snakes and other non-venomous arboreal species. Range and habitat, combined with eye size and iris color, are the most reliable identification clues among similar-looking green pit vipers.
Frequently asked questions
What is the most distinctive feature of the Large-Eyed Pit Viper?
Its unusually large eyes relative to head size, compared to other related pit vipers.
What color is this snake typically?
It is usually bright green, sometimes with a yellowish or bluish tinge and a thin lateral stripe.
Where is it found?
In forests, plantations, and shrublands across parts of Southeast Asia, including Thailand, Cambodia, Laos, and Vietnam.
How can it be told apart from harmless green snakes?
By its broad triangular head, heat-sensing pits, vertically elliptical pupils, and keeled scales, none of which non-venomous green vine snakes have.
How large does it grow?
Adults typically reach 60 to 90 cm (24 to 35 inches) in length.