Eyelash pit viper
Text by: Andrey Acosta / Juan Jorge Araya
Costa Rica is one of the most biodiverse countries in the world, it posses about 5% of world’s biodiversity (Obando, 2007). Among the beautiful animals living in Costa Rica, we can find the group of reptiles, some of them are the American Crocodile, the Green Iguana, colorful lizards and anoles. You can enjoy of these good-looking living fossils just walking around in a trail or spending the day in some river (not all of them), in the case of crocodiles.
There are other reptiles not so easy to find, or at least they demand more ability to be found in most cases… snakes. Snakes make up 60% of all reptiles in Costa Rica (Solórzano, 2004) and yet, they are the shiest group, but it is a really amazing experience once you find one of them.
There are almost 140 species of snakes in Costa Rica distributed in different families according to their physical and genetic characteristics, but only two of the nine families present in the country, are venomous.
Some days ago while walking through the main trail at Cahuita National Park in the Caribbean side of Costa Rica, we were able to find one of the most beautiful snakes that inhabit in our country, the locals call it Bocaracá but the English name used among scientists and herpetologists is Eyelash pit viper (Bothriechis schlegelii).
The Eyelash pit viper belongs to Family Viperidae (venomous vipers). This is a small sized viper with a known maximum length of 95cm, although the average on adults is 50-70 cm. This viper is arboreal, but also, it isn’t rare to watch them close to the ground, specially juveniles (Solórzano, 2004). This species is more active at night, resting during the day.
This specie is well known for the variation in its color, they have different morphs (green, brown, brownish, yellow, yellowish, grayish, white, pinkish and more), but the best way to tell apart this specie from the others is by its small horn-shaped extensions on the supraocular scales (above eyes).
In Costa Rica, the yellow morph is also known as Oropel (from Oro which means gold in Spanish) by the locals, but is the same specie, so remember, for the locals the yellow one is Oropel and those of other colors are Bocaracás.
In our case, we found a beautiful “white “Bocaracá”, awake, posed on a buttress root, probably waiting for a prey (there were some anoles near). Like most snakes its most common hunting method is waiting immobile until one of its preys is close enough, from where they can attack surprisingly. They feed on rodents, some lizards, frogs, small bats, birds and even hummingbirds.
Anyway, we took a couple pictures and left, so our scaled friend could keep hunting, it was around breakfast time when we found it, so we didn’t want to interrupt its meal time.
The viper family occurs worldwide, except for Australia and some oceanic islands. All vipers possess long, hinged fangs that can penetrate thick fur or several layers of feathers and inject s strong venom deep into a prey animal´s body. (Leenders, 2001).
All viper species in the New World are assigned to the subfamily Crotalinae or pit vipers, this subfamily have a distinct additional feature, a deep, pit like hole on each side of the head between the eye and the nostril. The so called loreal pits are sophisticated infrared receptors that allow the snake to locate and track prey whose body temperature differs from background temperatures. For the most part, these snakes are sit and wait predators, they stay in the same spot for a varying amount of time, ranging from a few hours to several weeks, waiting for the prey to pass within striking distance (Leenders, 2001).
Their excellent camouflage makes them nearly invisible to both prey and predators. Costa Rica has 14 species of pit vipers in 8 different genera, ranging from small, slender snakes that live in trees in cool mountainous regions to very large, thick bodied terrestrial pit vipers that inhabit the hot lowlands.
The feature that most readily distinguishes an eyelash pit viper from all other Costa Rican snakes is the presence of usually two, eyelash like pointed scales above each eye. The function of the scales is still a mystery. The coloration of this species is extremely variable, even within a single litter, different color forms may occur.
The distribution range of Bothriechis schlegelii extends from the southern part of Mexico south to Ecuador and Venezuela, at elevations between sea level and 1300 meters (4250 feet).
Snake bite incidents involving this species are not uncommon in Costa Rica, and every year three to six people are reported to have died after being bitten. A large percentage of the bites are sustained by people walking through dense vegetation, because this snake is arboreal, they are often bitten in the head, neck, shoulders or chest. Bothriechis schlegelii is live-bearing and produces litters of up to 20 young, each measuring between 21cm and 24cm (Leenders, 2001).
Leenders, Twan. (2001). A guide to Amphibians and Reptiles of Costa Rica. San José: Zona Tropical.
Obando, V. (2007). Biodiversidad de Costa Rica en cifras. Instituto Nacional de Biodiversidad (INBio). Heredia, Costa Rica.
Solórzano, A. (2004). Snakes of Costa Rica: Distribution, taxonomy, and natural history. Instituto Nacional de Biodiversidad (INBio). Heredia, Costa Rica.