Snakes are reptiles found on every continent except Antarctica. They have no legs and no eyelids. There are over 3,400 snake species that vary greatly in size, from 10 cm to 9 meters long. Snakes use their forked tongue to smell and track prey. Some snakes can see infrared radiation to detect warm-blooded animals. Snakes are covered in scales and shed their skin periodically. They are carnivorous, eating small animals, birds, eggs or insects. Venomous snakes use venom to paralyze prey, while constrictors kill by coiling around their victim. In colder climates, snakes brumate or become inactive during winter instead of hibernating.