Crotalus viridis

Species of snake

Crotalus viridis (Common names: prairie rattlesnake, Great Plains rattlesnake,) is a venomous pit viper species native to the western United States, southwestern Canada, and northern Mexico. Currently, two subspecies are recognized, including the prairie rattlesnake (Crotalus viridis viridis), the nominate subspecies, and the Hopi rattlesnake (Crotalus viridis nuntius).

This species commonly grows to more than in length. The maximum recorded size is In Montana, specimens occasionally exceed in length; the species reaches its maximum size in this region. One of the most characteristic features is the presence of three or more, usually four, internasal scales. Identification characteristics will vary depending on which subspecies is encountered. Generally, prairie rattlesnakes are usually lightly colored in hues of brown. Patches of dark brown are often distributed in a dorsal pattern. A color band may be seen at the back of the eye. The prairie rattlesnake group carries the distinctive triangle shaped head and pit sensory organs on either side of the head. A key characteristic that can help differentiate a prairie rattlesnake from other rattlesnakes is the presence of two internasals contacting the rostral.

Prairie rattlesnakes are found in North America over much of the Great Plains, the eastern foothills and some intermontane valleys of the Rocky Mountains, from southwestern Canada through the United States to northern Mexico. In Canada, they occur in Alberta and Saskatchewan; in the US in eastern Idaho, most of Montana, North Dakota, South Dakota, Wyoming, Nebraska, Colorado, Kansas, Oklahoma, Texas, New Mexico, northeastern Arizona, extreme western Iowa, and in Mexico in northern Coahuila and northwestern Chihuahua. Its vertical range is from near the Rio Grande to over in elevation in Wyoming. The type locality is described as "the Upper Missouri [Valley, USA]". An emendation was proposed by H. M. Smith and Taylor (1950) to "Gross, Boyd County, Nebraska." They seem to prefer dry areas with moderate vegetation coverage. Vegetation cover will vary depending on region and subspecies. The venom of the Prairie rattlesnake is a complexly structured mixture of different proteins with enzymes such as proteases and peptidases found among them. Besides the hemotoxin and its tissue destructive effect, the venom also has neurotoxic properties.

Prairie rattlesnakes, because of their expansive distribution, have a wide array of prey. Generally, this species prefers small mammals, such as ground squirrels, ground nesting birds, mice, rats, small rabbits and prairie dogs. They will occasionally feed on amphibians and reptiles, and sometimes even other snakes. This is more commonly seen in juvenile snakes. They give birth in late summer or early fall, being their breed 22–28 cm long, without the need for parental care. In addition, the young are toxic as soon as they are born. They reach sexual maturity at three years of age. It is also common for females to give birth at communal den sites with the young born between August and October.

This species is classified as Least Concern on the IUCN Red List of Threatened Species (v3.1, 2001). Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend was stable when assessed in 2006.