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(Crotalidae). rattlers, a family of poisonous snakes closely related to the vipers. The nerve endings at the bottom of the facial depression, located between the nostrils and the eye. are capable of perceiving even the faintest (approximately 0.1°C) variations in air temperature. As a result of this, the snake feels the approach of even a small warm-blooded animal, which is its prey. In daytime it hides under rocks and in the burrows of rodents. The snakes often gather in large numbers for hibernation.
Many rattlesnakes live in tropical forests; some are found in semideserts and deserts, while certain species live high in the mountains. Rattlesnakes feed on various vertebrates, chiefly mammals. The overwhelming majority of rattlesnakes are ovoviviparous (the young rupture the egg membranes a few minutes after they are laid). Two North American genera (Crotalus and Sistrurus) have a rattle on the end of the tail (from which the Russian as well as the English name of the family is derived). The rattle is formed of modified terminal scales and consists of movable segments. During rapid oscillations of the tip of the tail, the segments striking one another produce their peculiar sound.
The rattlesnake family includes six genera, which include more than 120 species. They are distributed in Asia and in North and South America. They are known from the Pliocene epoch. In the USSR they are represented by several species of mamushi. The bites of rattlesnakes are fatal to small animals and extremely dangerous to large animals and humans.