Snakes are a family of legless, elongated, venomous or non-venomous carnivorous reptiles. Covered in scales and equipped with multiple joints in their jaws, most species of snakes live on land with some species are able to swim or fly. Thanks to their flexible jaws, most snakes eat their prey whole after they kill through either constriction, if non-venomous, or through poisoning with their venomous bite. Snakes are found on nearly every continent, except Antarctica, and are not found on many large islands, such as Ireland and Iceland. Only 600 species of snakes are venomous and only 200 of those are venomous enough to seriously harm or kill a human (about 7 percent of all snakes). Snakes shed their skin monthly and have forked tongues that they use to smell in order to hunt their prey and sense their surroundings.