Rattlesnake entering its burrow.
Source: National Geographic Photo Gallery
Photographer: Bruce Dale
Snakes belong to the animal class reptiles. This group also includes crocodiles, lizards, and turtles. Reptiles are cold-blooded animals that raise their body temperature by lying in the sun or lower it by crawling into the shade. Their body temperature changes to the temperature of its surroundings. Because of this, snakes that live in colder climates must hibernate through the winter. They will find burrows or caves and fall into a deep sleep until the weather becomes ware enough for them.
There are more than 2,900 species of snakes in the world. They live almost everywhere, in deserts, forests, oceans, streams, and lakes. Snakes live on the ground, in trees, and in water.
Snakes cannot survive in places where the ground stays frozen year round so there are no snakes north of the Arctic Circle or in Antarctica. Some islands, including Ireland and New Zealand, do not have snakes at all.