Last Updated: Jun 17, 2015
The fer-de-lance, a pitviper species, is known as the terciopelo in Costa Rica. It is considered one of the country’s most dangerous snakes, as it is both highly venomous and aggressive – a trait not shared by many snakes, which bite primarily as a defense mechanism.
Scientific Name: Bothrops asper
Status in the Wild: Common
Habitat: Grasslands, Rainforests, Tropical Dry Forests, Woodlands
Sometimes referred to as “the ultimate pitviper,” the fer-de-lance has a triangular head and a heat sensitive organ between its eyes and nostrils. In terms of coloration, they resemble a rattlesnake: brown with chevron markings of darker brown or forest green outlined in white. The species is one of the most sexually dimorphic in the snake kingdom. Though they are born about the same size, females grow more quickly and larger than males; adult females can reach over eight feet while males rarely measure more than seven feet. Females have exceptionally thick bodies and can weigh in around 13 pounds – the heaviest of all venomous snakes.
Fer-de-lances are nocturnal and usually remain hidden under leaf litter or among tree roots. Juveniles may be semi-arboreal, and several cases have been reported of adult snakes living in trees. Their diet consists primarily of terrestrial vertebrates like frogs and lizards, and unlike other Central American species, the Costa Rican fer-de-lance also favors small mammals such as opossums and rats.
Adults are considered the most dangerous snake in Costa Rica; they will defend themselves when they feel threatened, so hikers are always advised to keep their eyes open and to wear sturdy hiking boots.
The fer-de-lance is found throughout the lowlands of Mexico and Central America, and also range south into Colombia, Ecuador and Venezuela. In Costa Rica, they prefer lowland rainforests and are prevalent in human-modified environments like banana plantations, where rats – a primary food source – are very common. They are frequently seen in Corcovado National Park, near Puerto Viejo and Cahuita, around Papagayo, and throughout the country’s interior lowlands.
Reproductive behaviors in Costa Rica are related to rainfall patterns, resulting in different mating habits among populations throughout the country. Breeding occurs from September to November in the Pacific and during March in the Caribbean. After a gestational period of 180 to 240 days, females deliver their offspring live between April and June and September to November. Most litters average around 40 young, though the number can vary greatly.
Status in the Wild:
The fer-de-lance is not a threatened species. However, these snakes have been threatened by severe habitat modification, especially in Costa Rica’s more rural areas. The species plays an important role in local ecosystems, both as prey and as predator. Visitors are advised to keep their distance from this highly venomous species and seek medical attention immediately in the case of snakebite.