Among the most distinguishable serpents, almost all rattlesnakes are identified by a rattle at the tip of their tails. This rattle serves as a warning; the snakes shake the tips of their tails to create the notorious rattling sound to ward off passersby. Over 20 species -- and numerous subspecies -- inhabit the United States and Mexico; rattlesnakes live only in the Americas.
Most rattlesnake species belong to the genus Crotalus, although a handful belong to the genus Sistrurus. The massasauga species and subspecies, along with the pigmy rattlesnake species and subspecies, belong to the latter. Sistrurus species typically are smaller rattlesnakes and often are separated from Crotalus by the distinguishing characteristic of nine large scales on their head.
All but three species of rattlesnakes belong to Crotalus: the pigmy rattlesnake, massasauga and Mexican pigmy rattlesnake. Both the pigmy rattlesnake and the massasauga have subspecies that inhabit different areas of the United States. Eastern massassaugas prefer wetter habitats such as marshes, swamps and wet forests; western and desert massasaugas venture into sage-brush prairie, desert land and rocky areas. Pigmy rattlesnakes inhabit the Southeast, South and southern Midwest.
Desert and Arid Habitat Species
Many rattlesnake species, though certainly not all, inhabit the dry, arid desert regions of the Southwest. Sidewinders, western diamondbacks, tiger rattlesnakes and the Mohave rattlesnake all inhabit sandy or arid habitats such as the Sonoran desert. As its name suggests, the sidewinder's distinct method of movement works side to side. These rattlesnakes also have hornlike scales that protrude above and to the side of their eyes. The large western diamondback can grow to nearly 8 feet long and is known to stand its ground when approached, unlike many other venomous snakes who would rather flee if given the opportunity. Their large fangs can reach over 1/2 inch long. Small tiger rattlers have a distinct banded pattern along their back, hence their common name. Mohave rattlesnakes have indubitably dangerous venom composed of both hemotoxins and neurotoxins. Other species that inhabit arid or semi-arid habitats include, but aren't limited to: twin-spotted, black-tailed, speckled and rock rattlesnakes.
Prairie, Wetland and Forest Species
While some may associate rattlesnakes with deserts and arid areas, a few species inhabit parts of the Midwest and eastern United States in habitats far from "arid." The large timber rattlesnake is common throughout much of the eastern half of the U.S. The timber rattlesnake often is easily distinguished by its long, black tail. The eastern diamondback inhabits the Southeast and is the largest rattlesnake in the United States, reaching up to 8 feet long. Its size alone is intimidating to most, and its venom is the most toxic among all venomous snakes in the United States.
- University of Nebraska-Lincoln: Rattlesnakes
- Stetson University: The Pigmy Rattlesnake (Sistrurus miliarius)
- National Audubon Society Field Guide to North American Reptiles and Amphibians; John L. Behler and F. Wayne King
- National Park Service Saguaro National Park: Venomous Snakes
- Tom Brakefield/Stockbyte/Getty Images