RATTLESNAKE

any of about 30 species of venomous New World snakes of the viper family (Viperidae), characterized by a tail rattle that produces a buzzing sound when vibrated. Rattlesnakes are pit vipers (subfamily Crotalinae)i.e., they have a small heat-sensing pit between each eye and nostril that aids in hunting. The rattle, their outstanding feature, is composed of horny, loosely connected segments, added one at a time, with each skin shedding. Presumably a warning device, the rattle usually contains six to ten segments in an adult. Eastern diamondback rattlesnake (Crotalus adamanteus) There are two genera of rattlesnakes: Sistrurus, including the massasauga and the pygmy rattler (S. miliarius), and Crotalus, including the sidewinder and all others. The massasauga and pygmy rattler are small and have nine large scales on the tops of their heads. Members of the genus Crotalus may be large or small, depending on the species, but all have mostly small scales on their heads. Among the best known species in North America are the timber, or banded, rattlesnake (C. horridus; see ) of the eastern and central United States, the prairie rattlesnake (C. viridis) of the western states, and the eastern and western diamondback rattlesnakes (C. adamanteus [see photograph] and C. atrox), which are the largest of all rattlesnakes. Rattlesnakes are found from Canada to South America, usually in arid regions. They vary in length from about 30 centimetres (one foot) in several small Mexican species to about 2.5 metres (8 feet) in the eastern diamondback. A few species are marked with transverse bands, but most rattlesnakes are blotched with dark diamonds, hexagons, or spots on a lighter background, usually gray or light brown; some are various shades of orange, pink, red, or green. Identification is sometimes difficult. Most species of rattlesnakes eat small animals, primarily rodents; small or juvenile rattlesnakes depend largely on lizards. All species bear live young, usually in broods of about a dozen. Like other snakes, rattlesnakes cannot tolerate extreme heat or cold. In hot areas they become nocturnal, avoiding the heat of day in protected shelters. In winter they congregate in rockslides or crevices to hibernate. All rattlesnakes are venomous and dangerous. With improved methods of treatment and the abandonment of folk cures (many of which presented more danger than benefit to the victim), a rattlesnake bite is no longer the threat to life that it once was. It is still, however, a serious and painful accident. The most dangerous rattlesnakes are the Mexican West Coast rattlesnake (C. basiliscus) and the tropical or South American rattlesnake, or cascabel (C. durissus); both have a venom that attacks the nervous system more strongly than that of other rattlesnakes. The most dangerous species in the United States are the diamondbacks.