The Terciopelo (Spanish for velvet) Viper is one of the largest and most dangerous venomous snakes in the Neotropical rainforest. The Terciopelo (Bothrops asper; Central America)and Fer-de-Lance (Bothrops atrox; South America) are closely related pit vipers in the family Crotalidae. They reach up to eight feet (2.5 m), with heads up to four inches (10 cm) wide.

These snakes are greatly feared and have many common names. Barba Amarilla (yellow beard) is what larger individuals like this one are often called.

Terciopelos are live-bearers, giving birth to up to 100 young at a time.

Terciopelos are responsible for the majority of venomous snake bites in Central America. Their venom is a hemotoxin, meaning it attacks the blood, and causes clots that lead to death of the surrounding tissues. The bites are very dangerous if not treated with antivenom.

However deadly, these snakes are an important part of the rainforest ecosystem. The favorite food of adult terciopelos are rainforest rats. If these rats become too common, they eat a lot of tree seeds and can change the structure of the forest. The rainforest rats also compete with larger mammals like agoutis.

The other large, venomous snake of the Central American rainforest is the Bushmaster, pictured at right. Although it is also a pit viper, it has many traits that are different. It is the only pit viper species that lays eggs, and unlike most pit vipers, its venom also contains a significant amount of neurotoxin (affects the nerves). The combined hemotoxin-neurotoxin venom is very deadly.

Bushmasters are incredibly rare, perhaps even fewer in number than other top predators like Jaguars and Harpy Eagles. These snakes often reach eight feet in length, with reports of eleven foot (3.4 m) snakes in Central America and fourteen (4.3 m) footers in South America.