Malayan pit viper

Identification

The Malayan pit viper is a stout snake with a large, triangular head, a pointed snout and a heat-sensing pit between the eye and the nostril^1,3. Its body scales are smooth².

It is reddish, pinkish or greyish-brown above, with large, dark, roughly triangular blotches edged in black, usually alternating on either side of a dark line down the back². A broad dark stripe runs from the eye to the corner of the mouth, with a pale stripe above it that is clearest in young snakes, and the belly is dirty white speckled with brown².

It rarely grows longer than about 70 cm¹. The largest snake in Smith’s classic account was a female of 87 cm².

Distribution

The Malayan pit viper lives in Thailand, Laos, Cambodia, southern Vietnam, Peninsular Malaysia and Indonesia, where it is found on Java and possibly Borneo¹. It occurs in most of Thailand⁴. WHO also lists it for the southern peninsula of Myanmar and for the Indonesian island of Madura³.

Habitat

It lives in wooded country at low altitudes and is common in many parts of its range, especially near the sea². It has been studied in deciduous dipterocarp forest in north-east Thailand, and it is also found in farmland^4,6. People most often meet it in rubber and coffee plantations³.

Behaviour

Like other Asian pit vipers, it is slow-moving and hunts in the evening and at night². It bites readily if disturbed². In southern Thailand, most bites happen between 6 and 9 pm and between April and June, and more than half are on the foot⁶.

Diet

Asian pit vipers feed mainly on small mammals, but they also take lizards, frogs and toads, and less often birds, eggs and other snakes². Smith’s captive Malayan pit vipers lived chiefly on mice². A radio-tracked female in north-east Thailand fed only once while she stayed with her eggs⁴.

Its diet differs from place to place, and so does its venom: a study across its range found that the variation in venom closely matches local diet, suggesting that each population’s venom is adapted to its prey⁵.

Reproduction

The female lays eggs and then stays coiled around them until they hatch, a kind of parental care that few snakes give^2,4. The eggshells are very thin¹. Two captive females laid 13 and 30 eggs, which hatched after 42 and 47 days, and the young measured 15–16 cm².

In north-east Thailand, a wild female tracked by radio laid three eggs in a rock crevice in August and stayed coiled around them for the whole 49–62 days until they hatched⁴.

Venom and medical significance

The Malayan pit viper causes 38% of snakebites by identified snakes in Thailand, and the World Health Organization places it in its highest category of medical importance in Thailand and Indonesia^3,6. About half of its bites inject too little venom to cause symptoms³.

When venom is injected, it causes local swelling, blistering, bruising and persistent bleeding from the fang marks, and it can stop the blood from clotting and cause bleeding from the gums and elsewhere; severe tissue death may need surgery and can leave permanent disability³. In a study of 838 patients in southern Thailand, 1.3% had bleeding away from the bite and 2.5% developed acute kidney injury⁶.

The Thai Red Cross makes a specific Malayan pit viper antivenom, which corrects the clotting problems but appears to do little against local tissue damage, and Biofarma in Indonesia makes an antivenom that includes this species³. Anyone bitten should go to hospital immediately.

Conservation

The Malayan pit viper is listed as Least Concern on the IUCN Red List (2022 assessment)⁷. It is common in many parts of its range².

Similar species

The eastern Russell’s viper (Daboia siamensis), which also lives in Thailand and on Java, is a true viper with no heat-sensing pit between the eye and the nostril, and it has rows of large, dark-rimmed spots instead of triangular blotches³. These differences are not a safe basis for handling any snake. Keep your distance from every snake you cannot identify.

In captivity

The Malayan pit viper is a dangerous venomous snake and is not suitable as a pet. Its bite can cause severe bleeding and permanent tissue damage³. It should never be caught or kept by private individuals.