Although rarely seen by the casual tourist in Costa Rica, snakes make up almost half of all reptile species in the nation (135 species, 17 poisonous). It is a fortunate traveler indeed who gets to see in the wild the fantastically elongated, I-beam-shaped chunk-headed snake, with its catlike elliptical eyes; the slender, beak-nosed bright green vinelike vine snake; or the relatively benign boa constrictor. Many neotropical snake species inhabit a wide range of Costa Rican environments, and wherever you are in the country there are sure to be snakes about. Not that you should worry. Fewer than 500 snakebites are reported each year, and less than three percent of these are fatal. Most bites occur among farmworkers.
Still, caution is always the watchword. Never reach into holes or under rocks, debris, or forest-floor leaf litter without first checking with a stick to see what might be quietly slumbering there. And remember that many snakes are well-camouflaged arboreal creatures which snooze on branches, so never reach for a branch without looking. You should even be cautious when peering inside bromeliads: the dark-colored chunk-headed snake likes to doze inside the moisture-collecting plants during the dry season.
Among the more common snake species you are likely to see are the wide-ranging boas which, with luck, you might spot crawling across a cultivated field or waiting patiently in the bough of a tree in wet or dry tropical forest, savannah, or dry thorn scrub. Wild boas vary in temperament and some are aggressive. Though not poisonous, they are quite capable of inflicting serious damage with their large teeth and will not hesitate to bite. Heaven forbid a full-grown adult (three meters or more) should sink its teeth in sufficiently to get its constricting coils around you!