Family: Viperidae, Pit Vipers view all from this family

Description 20-36" (50.8-91.4 cm). Numerous gray or brownish crossbands mark pale gray, buff, lavender, or pinkish-gray upper surface. Crossbands composed of tiny dots, often poorly defined. Head proportionally small, rattle large. Scales keeled, in 23 rows.

Warning Rattlesnakes, Copperheads, and Cottonmouths belong to a group of snakes known as pit vipers. These dangerous snakes have a heat-sensitive sensory organ on each side of the head that enables them to locate warm-blooded prey and strike accurately, even in the dark. The curved, hollow fangs are normally folded back along the jaw. When a pit viper strikes, the fangs rapidly swing forward and fill with venom as the mouth opens. The venom is a complex mixture of proteins that acts primarily on a victim's blood tissue. If you hear a rattlesnake shaking its rattle, back away. The snake is issuing a warning, and if the warning is ignored it may bite. There are many factors (temperature being the most important) that determine how a snake will react when confronted by a human. Venomous snakes should always be observed from a safe distance. Pit vipers are never safe to handle. Even dead ones can retain some neurological reflexes, and "road kills" have been known to bite. How to avoid and treat snakebites

Breeding Live-bearing. Young reportedly about 9" (23 cm) at birth.

Habitat Arid rocky foothills and canyons, primarily in ocotilla-mesquite-creosote bush and saguaro-paloverde associations; sea level to 4,800' (1,450 m).

Range C. Arizona south to s. Sonora, Mexico.

Discussion Natural history poorly known. Reportedly active day and night and occasionally encountered crossing roads after warm showers. Occasionally confused with larger Speckled Rattlesnake which enters its range. Feeds on lizards and small newborn mammals. Record longevity exceeds 15 years.