Terciopelo

Identification

The terciopelo is a large pit viper with a broad, flattened head set clearly apart from the neck⁸. It is olive, grey, brown or nearly black, with 18–25 dark triangles edged in pale scales along each side; seen from above, these can form X or butterfly shapes^1,8. A dark stripe runs from behind the eye to the corner of the mouth, the pupil is vertical, the chin is often yellow and the belly is cream¹. Its back scales are strongly keeled, which gives the species its name: asper is Latin for “rough”¹.

Adults typically measure 1.2–1.8 m and can weigh up to 6 kg⁸. Males reach about 1.6 m, while females are much bulkier and can reach about 2.5 m^1,8.

Distribution

The terciopelo lives in the humid lowlands of Middle America and north-western South America². In Mexico it ranges from southern Tamaulipas and San Luis Potosí south through Veracruz, Puebla, Oaxaca and Chiapas to the Yucatán Peninsula^1,8. From there it continues through Guatemala, Belize, Honduras, Nicaragua, Costa Rica and Panama to Colombia and western Ecuador¹.

It does not occur in El Salvador⁹. Older records from Trinidad and El Salvador came from confusion with the common lancehead, and the lanceheads of Venezuela are now placed in Bothrops colombiensis; records from north-western Peru still need confirmation^1,6.

Habitat

The terciopelo is mainly a snake of tropical rainforest and evergreen forest, often near rivers and streams⁸. In Costa Rica, radio-tracked snakes of both sexes strongly preferred areas near swamps². It also copes well with lightly disturbed land at the edge of farmland, so it is not rare to find one in or near houses².

It is mostly found in the lowlands, but in Colombia it reaches about 1,500 m¹.

Behaviour

The terciopelo is mainly active at night and lives alone⁸. Radio-tracking in Costa Rica showed that it usually makes short moves of less than 10 m between a daytime shelter and a night-time ambush site, with occasional longer moves to new hunting areas². Its home range is small, averaging about 4–6 hectares².

Young terciopelos sometimes climb into vegetation⁸. Despite popular belief, there is no evidence that its numbers in Costa Rica are increasing².

Diet

The terciopelo is a generalist predator². Young snakes eat mainly frogs and lizards, while adults increasingly take birds, rodents and other small mammals, as well as large frogs when warm-blooded prey is scarce². Some of its prey are animals that farmers consider pests².

Young terciopelos also use their differently coloured tail tip as a lure to attract prey⁸.

Reproduction

The terciopelo gives birth to live young¹. Breeding is highly seasonal and tied to rainfall, so its timing differs between Costa Rica’s Caribbean and Pacific lowlands². After a pregnancy of 6–8 months, females give birth to litters of 5 to 86 young, with larger females having more young⁸.

Litters of up to about 90 newborns have been recorded¹.

Venom and medical significance

The terciopelo causes most snakebites in Central America and northern South America, mostly in young farm workers in rural areas³. Of the roughly 5,500 snakebites a year in Central America, most of the bites, and the most severe ones, are caused by this species⁴. The World Health Organization lists it in Category 1, the highest medical importance, in Mexico, Belize, Guatemala, Honduras, Nicaragua, Costa Rica, Panama, Colombia and Ecuador⁵.

Its bite can cause swelling, bruising, blisters, death of skin and muscle, failure of blood clotting, bleeding, low blood pressure and kidney problems³. Antivenom given into a vein is the main treatment, and antivenoms made in Brazil, Colombia, Costa Rica and Mexico have been tested in clinical trials³. Anyone bitten should go to hospital immediately.

Conservation

The terciopelo is listed as Least Concern on the IUCN Red List (published 2021)⁷. Despite persecution by people and large changes to its habitat, it is expected to persist well into the future².

Similar species

The terciopelo was once treated as part of the common lancehead (Bothrops atrox) and is still often confused with it^1,8. The common lancehead often has yellow or rusty tones and more rectangular or trapezoid blotches, and the two species live side by side only in parts of northern Colombia⁸.

These differences are not a safe basis for handling any snake. Keep your distance from every snake you cannot identify.

In captivity

The terciopelo is a dangerous venomous snake and is not suitable as a pet. In zoos it has lived for 15–21 years⁸. In the wild, give it plenty of space and let it move away.