Idaho State Reptile
Western Rattlesnake (common name)
Crotalus viridis (scientific name)
Native to North America including the western U.S., southwestern Canada, and northern Mexico, the western rattlesnake is known for the alarming rattling noise it makes with its tail before striking. The rattler is a pit viper like the copperhead snake and the water moccasin, and as such has an indentation on each side of its head that can detect heat.
ALSO KNOWN AS
Prairie rattlesnake, plains rattlesnake, black rattler, common rattlesnake, confluent rattlesnake, Great Basin rattlesnake, large prairie rattlesnake, rattlesnake of the prairies, spotted rattlesnake
The western rattlesnake is most often light brown with darker brown patches along its back. Its head is triangular and there’s a deep indentation between its nose and mouth containing a heat-sensitive organ. A rattlesnake’s most characteristic feature, though, is the rattle found at the tip of its tail. In newborn snakes, the rattle is a single bead that makes no noise. Each time a rattlesnake sheds its skin, it grows a new bead. These beads click together to make the snake’s warning rattle.
There are a number of subspecies, and each looks slightly different. A prairie rattlesnake, for example, tends to have a yellow or gray tint to its overall coloring. Its spots have straight edges and a border of pale scales. Its eye stripe is wide, with lighter stripes tilted to the snake’s jaw on either side. The great basin rattlesnake usually has a more beige-yellow background color. Its spots are less pronounced and irregular with pale centers, and are even more indistinct on the snake’s head. The northern Pacific rattlesnake is darker overall with a deep brown or gray skin that sometimes runs to black.
Up to 27 years in captivity. Up to 16–20 years in the wild.
Varied, but mostly dry places with medium plant coverage.
Range: Alberta, British Columbia, Saskatchewan, most of the Great Plains including Idaho, Montana, and North Dakota south all the way to Mexico’s northern states of Coahuila and Chihuahua. Within this range, it can live at elevations of 328 feet (100 m) to over 9,104 feet (2,775 m). Within Idaho, prairie rattlesnakes have the smallest range and only occur in the east-central parts of the state, in Valley and Lemhi Counties. Great Basin rattlesnakes are more common, and live in southwestern Idaho. Northern Pacific rattlesnakes live in the Clearwater, Salmon, and Snake River drainage areas of west-central Idaho.
Conservation Status: Least Concern (LC)
In early spring, western rattlesnakes come out of hibernation and look for mates or bask in the sun. In areas where vegetation is dense, a snake may climb to a bush’s upper branches to find a sunny spot. Unlike most snakes, western rattlesnakes give birth like mammals rather than laying eggs, and can have from one to 25 young at a time. Females don’t necessarily breed each year. They can mate any time during their active months, but always give birth in the early fall. It’s usual for females to give birth in a communal nest. A young western rattlesnake is born fully formed and independent.
These snakes prefer to be active by daylight when weather is cool and at night when temperatures rise. When threatened, a western rattlesnake shakes its tail very quickly, making a rustling or rattling sound to warn any approaching animal away. If that doesn’t work and the snake still feels a need to defend itself, it will bite. The snake’s venom is a strong blood poison that the snake can regulate; some bites may be venom-free.
Top land speed recorded: 3 mph (4.8 kph).
Small mammals including prairie dogs, rats, mice, squirrels, small rabbits, and others.
Breeding interval: Annual
Birthing period: August–October
Average litter size: 4–12 young
Size at birth: 7 to 15 in (18 to 38 cm) long
Click to enlarge an image
Raw Data Source: U.S. Fish and Wildlife Service
Author: World Trade Press