Calloselasma – Malayan pit viper

A ground-dwelling, venomous snake native to Southeast Asia—found from Thailand and Vietnam through peninsular Malaysia and into the Indonesian island of Java. It is easily recognised by its triangular, broad head and distinctive colouration: a generally reddish-brown or grey body marked with two rows of dark triangular blotches, often set against a pale background and accompanied by a thin vertebral stripe.

This snake prefers habitats such as forest edges, rubber and palm plantations, bamboo thickets, unused farmland, and other disturbed areas close to human presence. Because it often rests in leaf litter or beneath plant debris during the day, its cryptic patterning allows it to blend seamlessly into its surroundings—making it hard to spot until it moves. When hunting or threatened, it uses its heat-sensing pit organs (located between each eye and nostril) to detect warm-blooded prey, giving it the “pit viper” distinction. Its diet consists of small mammals (like rats and mice), amphibians, and occasionally birds, making it an important controller of pest species in agricultural zones.

What sets the Malayan pit viper apart is both its remarkable camouflage and its medically important venom. The venom is primarily hemotoxic, meaning it attacks the blood-clotting system, causes severe local swelling, tissue damage, and sometimes internal bleeding. In Thailand, it is one of the leading snakes responsible for snakebite incidents, with a high number of hospital admissions each year. Although fatalities are rare thanks to antivenom and medical care, many untreated bites result in serious complications, including necrosis (tissue death), compartment syndrome, or permanent damage to limbs. The snake’s behavior—often sedentary, waiting patiently in ambush—adds to the risk of accidental encounters.