Large-scaled Pit Viper
Trimeresurus trigonocephalus • Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Trimeresurus, Species: Trimeresurus trigonocephalus
Venomous Status
Venomous (Solenoglyphous)
Danger Level
Moderate Risk. While bites are painful and cause significant localized swelling, they are rarely fatal. Medical attention is required to manage tissue damage.
Geographic Range
Endemic to Sri Lanka. It is widely distributed across the island's wet zone, intermediate zone, and certain parts of the dry zone, particularly in hilly regions.
Conservation Status
Least Concern (IUCN), though local populations face threats from habitat loss due to deforestation and agricultural expansion.
Physical Description
Distinctive bright green to yellow-green body with a black pattern of broken stripes or spots. The head is large, triangular, and distinct from the neck, with a dark temporal stripe. Scales are heavily keeled and large on the head. Eyes have vertical pupils.
Size & Dimensions
Typical adult length is 60–75 cm (24–30 inches), with maximum lengths occasionally reaching 130 cm. This specimen appears to be an adult.
Habitat
Wet-zone forests, rubber and tea plantations, and grasslands. It is a primarily arboreal species found from lowlands up to approximately 1,800 meters elevation.
Behavior & Temperament
Arboreal and primarily nocturnal, though often seen resting on low vegetation during the day. It is generally sluggish and slow-moving but can strike quickly if provoked or handled.
Diet & Feeding
Carnivorous, preying on small mammals, birds, lizards, and frogs. It is an ambush predator that uses its heat-sensing pits to locate warm-blooded prey.
Reproduction
Ovoviviparous (gives birth to live young). Litters typically consist of 5 to 25 neonates, usually born during the rainy season.
Venom & Safety
Venom Type
Hemotoxic and cytotoxic, causing local tissue damage, swelling, and pain. It is not generally considered lethal to healthy adult humans but is medically significant.
First Aid Advice
Keep the victim calm, immobilize the affected limb at or below heart level, and seek immediate medical attention. Do not use tourniquets or attempt to suck out the venom. Antivenom is available for Trimeresurus species.
Look-alikes
Often confused with the Green Bamboo Viper (Trimeresurus gramineus) or the Sri Lankan Palm Viper (Craspedocephalus strigatus), but distinguished by its larger, more distinct head scales and specific patterns.
Conservation Status
Least Concern (IUCN), though local populations face threats from habitat loss due to deforestation and agricultural expansion.
Cultural Significance
Known locally as 'Pala Polonga' in Sinhala. It plays a significant ecological role in controlling rodent and lizard populations in its native ecosystems.
Notable Features
Features extremely large, plate-like scales on the top of the head compared to other pit vipers. It possesses heat-sensitive pits between the eyes and nostrils for detecting infrared radiation.