costa rica snakes
Snakes have been vilified throughout the Western World. They are generally regarded with aversion and fear. This comes as no surprise when even the Bible depicts the harbinger of doom, in the Garden of Eden, as a serpent (i.e. snake). The possession of venom of some species often further exacerbates the hysteria found in popular lore. This is truly a pity, because the vast majority of snakes are not particularly dangerous. Upon closer observation, many species are actually sleek and elegant. Although many snakes have an iridescent sheen, they are not slimy to the touch. Prior to the prejudice of modern times, snakes were often venerated as gods. In practical terms ,many agricultural societies benefit greatly from snakes preying upon rodents, which often cause great losses to farmers. Needless to say the 1800 or so species found in the world also play a valuable role in a great variety of ecosystems.
On the other hand, since there are snakes that can be deadly to humans, it is important to approach them with caution and respect. In Costa Rica we find a bit more than 7.5% of the world's snake fauna with approximately 135 species found within its borders. The 17 snakes that belong to the Viper and Coral Snake families are considered dangerous, in that their venom can be lethal. This means that 87% of the country's snakes are not considered to be dangerous, despite the fact that some of the members of other families also have varying degrees of venom. Many of these snakes are not known to bite at all, even when handled. A few species that have been found to be aggressive enough to bite have caused symptoms no more severe than localized pain, significant bleeding, or the swelling of a limb. It is important to remember that the function of venom is to help a snake immobilize, subdue and digest prey. Humans do not qualify as prey, merely as a potential threat. Thus, fundamentally, snakes have no interest in striking at humans if they do not feel that they are in danger.
In the realm of science, the snakes are vertebrates that belong to the Class known as Reptilia (along with Lizards, Crocodiles, Alligators, and Turtles). They share the Order of Squamata (Latin for scaly), with their close relatives the lizards. As a matter of fact, the snakes are believed to have evolved from a group of lizard-like ancestors about 125 million years ago, during the Cretaceous era. These ancestors seemed to evolve towards a subterranean lifestyle in which limbs, like legs, were more of a hindrance than a benefit. In time they lost all limbs as well as most of the bone structures that supported them. Over a period of millions of years the subterranean snakes changed back to life above ground. Then with the rise in certain types of small mammalian prey, such as rodents, snakes became more and more common. Today they inhabit almost all of earth's ecosystems. Due to their inability to generate heat internally, snakes must regulate their body temperature from ambient sources. As a result the number of species diminishes as the distance from the tropics increases. Few snakes live in cool temperate regions, none at the poles. Costa Rica's climate is quite favorable to their existence.
Within this country snakes belong to nine families, four of which comprise the vast majority of species. The largest family, known as the Colubridae are also called the Typical Snakes. Fairly common members of this family in the United States are the Garter Snake, the Corn or Rat snake, the Hog Nosed Snake, and the King Snake. The other three major families are the boas (Boidae) , the coral snakes( Elapidae), and the vipers (Viperidae)
In Costa Rica a few of the outstanding members of the Colubridae family are the vine snakes, the mussurana, and the blunt headed tree snake. The vine snakes (Oxybelis sp.) are extremely slender and possess pointed heads, only slightly wider than their necks. They are primarily arboreal and wander through the vegetation in search of birds. Part of their hunting technique is to mimic the vine tangles which are so numerous in the tropical forest. It has adapted itself to moving exactly like a branch or vine bobbing in the breeze, creeping ever so slowly up to its prey. The mussurana (Clelia clelia) is a dark gray or black snake that can be up to six feet in length. It actually hunts an assortment of snakes, many of them venomous. It seems to be immune to the toxins and is thus an important means of controlling viper populations. A snake with unusual morphological features is the blunt headed tree snake (Imantodes cenchoa). It measures about one foot in length, has vertical pupils,(like a cat), modified vertebrae, enlarged vertebral scales, and a body shaped like an I-beam. All of these are adaptations for life on the outer reaches of trees and shrubs, hunting for lizards and frogs on the small twigs and leaves. This type of body allows the snake to reach across gaps in the vegetation that are up to one half of its length. All in all the Colubridae is an extremely diverse family. Its members come in all sizes, shapes, and colors. Some taxonomists feel it should be divided in smaller families, but until then it represents the largest of all snake families.
The boas belong to the family Boidae. They are considered a more primitive family because they retain vestigial body parts that are an inheritance from their lizard forbears. Their skeletons include a pelvic girdle and tiny leg bones that are no longer functional The largest of the world's snakes belong to this family. The anaconda has been recorded as the most massive of snakes, weighing 235 lbs. at a length of 29 feet. The anaconda's range is restricted to South America, but its close cousin, the boa constrictor(which is Costa Rica's largest snake)is no pushover, reaching lengths of 18 feet. As its name suggests it kills prey by constriction; wrapping its coils around a victim and crushing it. The cause of death is suffocation. Another intriguing species is the rainbow boa with its jewel like radiance. Although its body color ranges from brown to rusty hues, the structure of its scales creates an almost shimmerimg gleam of turquoise and blue when exposed to direct light. Few observers could deny that it is stunning. There are two other boas within the country, which also prey upon rodents, birds, and other small vertebrates. Larger prey is the exclusive domain of the boa constrictor, which is known to have consumed ocelots and coatis; animals that are about the size of a Cocker Spaniel.
A third family that needs little introduction is that of the coral snakes. These reptiles are always brightly colored with some arrangement of red, black, yellow or white. Today these colors are considered aposematic which means they serve as a warning. And indeed the warning should be heeded because they are venomous. Their particular type of poison is primarily a neurotoxin which causes paralysis of muscle tissue that can lead to death. Coral snakes have rear fangs, which places some limitations on their ability to bite a large object. If one wears boots while hiking one reduces the danger of a coral snake bite to virtually nil. Most cases of envenomation have occurred when someone has deliberately picked up a coral snake and has subsequently been bitten in the hand.
Vipers are the snakes that most inspire primal awe and fear. Large syringe like fangs and lightning speed make them a formidable predator. In Costa Rica there are 12 species of vipers, all of which can be recognized by a combination of features. First of all their heads are rather triangular being very wide at the base of the jaws. ( Some would say shaped like a spearhead) Secondly they have two holes on each side of their face; one being the nostril and the other a facial pit which acts as a heat sensing device. Whereas most other snakes have large shield like scales on the top of their heads, vipers have many rows of small scales, as well as vertical pupils.
The viper that has caused most fatalities and serious injuries is the fer-de-lance, known locally as the terciopelo. It seems to be the most brazen of the vipers, although it also does not generally strike unprovoked. It is somewhat reminiscent of a rattlesnake, colored with varying hues of brown and beige, with a pattern of large dark diamonds on its upper side. Despite its reputation, in my own experience of 8 years as a naturalist in the tropics; I have been in close proximity, or even stepped over a fer-de-lance numerous times- and not once did an individual strike out at me. Furthermore, I have been in the presence of a few herpetologists who have tried to trap, apprehend, or manipulate these creatures and on these occasions there was also not a single aggressive manifestation. This is not to say that they will not strike, or that one shouldn't practice extreme caution in their proximity- but I merely wish to suggest that even this most feared of snakes is not a rampaging, vicious animal that is prone to extremes of aggression.
On any given trip to Costa Rica the likelihood of encountering even one snake is rather small. They are more common in the lowlands than in the highlands, and are often more active at night. If one has the great misfortune of being bitten the standard procedure is to kill the snake and take it with you for identification. Immobilize the victim and try to keep them calm. (The slower the metabolism, the slower the spread of the venom) Then proceed to the nearest hospital, which should have antivenin. A snake bite by a poisonous snake will only begin to have serious systemic manifestations after 2-5 hours. There have been a fair amount of cases where no venom was even delivered by the bite. In the present day few fatalities occur except in the remotest of regions.
Written by Marc Egger