Some lizards do hibernate, depending upon the species, the climate of their natural habitat and the weather. Hibernation in lizards is an adaptation that allows them to survive low temperatures despite being ectothermic, or cold-blooded, creatures.
Many species of lizard that live in temperate climates hibernate to survive the cold, as without sufficient ambient heat, their metabolic processes slow down. Without hibernation, this slow-down can be deadly. During hibernation, their metabolism changes to drastically conserve energy, so the metabolic slow-down from low temperatures is less dangerous. It is a gradual process that is driven by several successive weeks of lower temperatures as the lizard's body converts to hibernation mode. Lizards are very prone to hypothermia, and their body tissue can die if they are not sufficiently prepared.
Some species of lizard that hibernate include green anoles, horned lizards, and fringe-toed lizards. Tropical species cannot hibernate, as they have not evolved adaptations to cold conditions.