The rattlesnakes are among the most famous and most feared snakes in the world. People see them as fierce and cunning creatures. But like all snakes rattlesnakes are actually timid and nervous. There are over 30 species of rattlesnakes. Most of them are native to Mexico and the southern United States.With the exception of the Santa Catalina,rattlesnakes Crotalus catalinensis all rattlesnakes have a so called rattle on the end of their tail. It consist of a series of hollow rings of a horny substance keritan. Keritan is the same substance that our fingernails are made of inter connected but not fixed to each other. Each time a rattlesnakes molt three or four times a year. The rattle is extremely brittle and often gets broken when a rattlesnakes feels it is in danger. Or becomes excited it shakes the rattle 40 to 60 times per second making the characteristic sound that warns enemies.And is meant to frighten them away. Rattlesnakes are only dangerous if they are accidentally trodden on or otherwise disturbed. Their bite is dangerous, especially to children but seldom fatal. The snakes are virtually immune to their own venom. Their diet consists of small mammals , birds and occasionally lizards and frogs.