Not all members of the Viperidae family have rattles at the tip of their tail. All members of the viper family, as well as many non-venomous snakes, will shake their tails when agitated. Copperheads and cottonmouths do not have rattles, but their tails will often shake against leaves and twigs, making a rattling sound. Rattles, dried scales at the tail tip, are found only on rattlesnakes. When these segments are shaken, the classic rattlesnake buzzing noise is heard. It is often believed that the number of segments on a rattlesnake's tail equals the rattlesnake's age. This is not always true. Usually rattlesnakes shed several times a year, depending on age, health and availability of food. With each shed a new segment of rattle is added. However, these rattles are often broken off when moving through rough terrain. Therefore, the number of segments in the rattle cannot accurately predict a snake's age.
