Gila monsters

Source: and
Gila monsters are large lizards. In the wild the animals can only be found in Mexico and in the southern United States (Nevada, Arizona, California). They are easily recognizable from their black wart-like skin with red-pink spots.
Its natural habitat is a dry, desert-like area. During the day, Gila monsters seek shelter under rocks or bushes. At dusk the animals start looking for food. Gila monsters can handle quite large meals (ranging from one third to half of their body weight). After a meal they can last a long time without food. They do need to drink water regularly.
Their diet consists of small rodents, young birds, and bird and reptile eggs. The scientific name of the Gila monster (Heloderma suspectum comes from Greek. Helos means head of a nail, or stud, and derma means skin. Heloderma therefore means studded skin. Suspectum means suspect: The discoverer of the Gila monster suspected the animal to be poisonous because of the grooves on its teeth.
The studded skin is due to osteoderms, bone plates that fortify the skin.
The idea that Gila monsters produce poison is correct. The poison (exanatide) is produced by glands in the lower jaw and is inserted into the prey via grooves in the molars. The poison is spread by chewing. The poison is not always found in prey however. Apparently the poison is mainly used as a defense mechanism.

Gila monsters hibernate and in zoos this should be induced artificially (from November to March). First the animals should not be given any food for two weeks in order to empty the gastro-intestinal system. Then the temperature of the enclosure should be lowered to 10-12 degrees Celsius. Also during hibernation the animals should be given fresh water. In zoos Gila monsters can become up to 20 years old.