North Philippine temple pit viper

Identification

This is a pit viper, with a heat-sensing pit on each side of the head between the eye and nostril^3,7. The scales on the top of its head and on its chin are strongly keeled³. Its colour is variable³. Females are green or blue, often with crossbands of blue and white or red and white, and a pale stripe behind the eye^3,4. Males and young snakes are green, with white or red spots and a white or red stripe behind the eye^3,4. In some populations on Negros, even the males are blue³.

Males stay small, growing to about 0.5 m^3,4. Females are much larger: the largest female reported by Vogel and colleagues was 0.96 m long, while the largest male was only 0.46 m³.

Distribution

This pit viper lives in the Philippines, on Borneo (Sabah, Sarawak, Brunei and Kalimantan), and in Indonesia on Sulawesi, Buton, the Sangihe Islands and Belitung^1,3. In the Philippines it is known from Luzon, the Visayas, Palawan, parts of Mindanao and the Sulu Archipelago^1,5. Until 2007 it was included in Wagler’s temple pit viper (Tropidolaemus wagleri)². A revision that year restricted T. wagleri to southern Thailand, Peninsular Malaysia and Sumatra, used T. subannulatus for snakes from Borneo, Sulawesi, the Sulu Archipelago and the Philippines, and recognised T. philippensis on Mindanao². Its authors expected that T. subannulatus might itself be split further³.

Habitat

On Luzon and in the Visayas it is common and widespread in forest, from sea level to mid-mountain elevations⁶. It lives in trees and seldom comes down to the ground³. In Malaysia, temple pit vipers are generally found in wet lowland rainforest from sea level up to about 400 m⁴. In Malaysia, people have been bitten by temple pit vipers while picking fruit in orchards, gardening, weeding and farming, and in forests and oil palm plantations⁴.

Behaviour

Temple pit vipers are not considered aggressive^4,5. They usually strike only when provoked, disturbed or accidentally stepped on, and most people bitten in a Malaysian study were bitten only once⁴. In that study, the hand or arm was bitten in 57% of cases⁴.

Diet

Temple pit vipers feed on small animals, especially birds, frogs, lizards, mice and other rodents⁴. In the Philippines it has been described as useful to people, because it eats agricultural pests, including rodents and even large rats⁵.

Reproduction

The North Philippine temple pit viper gives birth to live young rather than laying eggs¹. Young temple pit vipers are slender and green with white and red spots, and the sexes only take on their different adult colours as they grow⁴.

Venom and medical significance

All pit vipers are venomous, and the World Health Organization lists this species in its Category 2 of medically important snakes, meaning it can cause illness or death but clinical data are lacking^4,7. In practice, recorded bites have been mild. A study of 190 bites by this species in Sabah and Sarawak, together with bites by its close relative T. wagleri, found mainly local pain and some swelling⁴. Almost all patients had only minimal local effects, antivenom was not needed in any case, and no one died⁴. Its venom does not affect blood clotting, and no specific antivenom has been made⁴. The study’s authors suggested it should be removed from the WHO Category 2 list in Malaysia⁴. Even so, anyone bitten should go to hospital immediately.

Conservation

The North Philippine temple pit viper is listed as Least Concern on the IUCN Red List (assessed in 2022)⁸. In the Philippines it is common and widespread in forest⁶.

Similar species

In the Philippines, green pit vipers of the genus Trimeresurus, such as the Philippine pit viper (Trimeresurus flavomaculatus), have smooth scales on the head and chin, while this species has strongly keeled ones³. On Mindanao, Leyte and Samar the related Tropidolaemus philippensis also occurs; it has fewer scale rows around the body (18–19 rather than 21–29)³. These differences are not a safe basis for handling any snake. Keep your distance from every snake you cannot identify.

In captivity

This is a venomous snake and is not suitable as a pet. Bites mostly happen when people disturb one by accident, for example while picking fruit or gardening⁴. Leave any pit viper you find alone. It should never be caught or kept by private individuals.