Green vine snake

Identification

The green vine snake is extremely slender, with a long, sharply pointed snout that ends in a small projecting tip^1,2. Its eyes have horizontal, keyhole-like pupils, a feature of the genus Ahaetulla^2,3. It is usually bright green, with a thin white stripe along each side of the belly¹, although some individuals are other colours^2,4. When the snake is alarmed, the skin between its scales shows a black-and-white checked pattern².

An adult female from Colombo measured 1.06 m, of which 40 cm was tail¹. Older accounts, written before the 2020 revision, describe vine snakes commonly reaching about 1.5 m².

Distribution

Since 2020, Ahaetulla nasuta has been treated as endemic to Sri Lanka, in the central and south-western wet zone^1,4. For a long time the name was used for green vine snakes across India, Bangladesh, Nepal and South-East Asia⁴.

A study by Mallik and colleagues in 2020 showed that these snakes are a group of several species¹. Indian populations are now A. borealis, A. farnsworthi, A. isabellina and A. malabarica in the Western Ghats, and A. oxyrhyncha in the lowlands¹. The authors also note that Sri Lanka itself may hold more than one species¹.

Habitat

In Sri Lanka this species lives in the wet, hilly zone in the centre and south-west of the island¹. It is fully arboreal, spending its life in trees and bushes⁴. Wall described vine snakes resting on the topmost branches of low bushes and scrub, where they look just like a green twig. They also climb tall trees².

Behaviour

Vine snakes are active by day, like the rest of their subfamily^2,3. They move quickly through leaves and thin twigs, spreading their light weight over many points, but are slow on the ground².

When threatened, a vine snake raises its front body and puffs out its neck to show the black-and-white checks between its scales. It then opens its mouth wide². Freshly caught snakes may strike repeatedly at a person’s face². Its Sinhala name, ahaetulla, means “eye plucker”, from an old belief that it aims for people’s eyes².

Diet

The Reptile Database lists lizards and other vertebrates as its prey⁴. Older records from Sri Lanka and India also include frogs, small birds, mice and occasionally other snakes².

Before striking, the snake draws its front body into zig-zag curves. It then darts forward, seizes its prey just behind the head and holds on until the animal’s struggles weaken². Captive young fed readily on geckos, agamid lizards and skinks².

Reproduction

The green vine snake gives birth to live young, usually 5–15 at a time⁴. The young develop inside the mother, and some are born still inside a thin membrane². Newborn vine snakes measured in Sri Lanka were about 31–33 cm long². In the older, wider sense of the species, young were reported to be born over a long season from about March to December².

Venom and medical significance

The green vine snake is mildly venomous. It is rear-fanged, meaning its grooved fangs sit at the back of the upper jaw². WHO lists the long-nosed whip snake among the colubrid snakes proven able to cause local envenoming⁵. Sri Lanka’s Ministry of Health lists vine snakes as mildly venomous⁶.

Reported bites in Sri Lanka and India caused local pain, swelling and numbness that cleared within two to three days, without wider illness². Wall noted that symptoms in people were not usual². Anyone bitten should still seek medical care.

Conservation

The IUCN Red List classes Ahaetulla nasuta as Least Concern (2025 assessment)⁷. Since the 2020 revision, this species is known only from Sri Lanka’s wet zone, a much smaller range than the old, wider species¹. The authors of the revision noted that more than one species may still be hidden among Sri Lankan vine snakes¹.

Similar species

In Sri Lanka, the green vine snake could be confused with the Sri Lankan green pit viper (Trimeresurus trigonocephalus), a venomous viper^5,6. Pit vipers have a small sensory pit between the nostril and the eye⁵. The vine snake has no pit, and its pupils are horizontal³. It is also extremely slender, with a long, pointed snout and a white stripe along each side of the belly^1,2.

These differences are not a safe basis for handling any snake. Since the pit viper is dangerous^5,6, treat every green tree snake with caution and leave it alone.

In captivity

Vine snakes have been kept in vivaria for study since at least the 1890s. Freshly caught snakes often strike at people, and captives have eaten lizards, mice and frogs². Because it is mildly venomous^5,6 and has a small range in the wild, it is not suitable as a pet. Do not collect or handle it.