Timber rattlesnakes (Crotalus horridus) and western diamondback rattlesnakes (Crotalus atrox) are very different species of snake, with their own separate ranges, habits and threats. Despite that they're of the same genus, these two species look and behave differently. Nevertheless, they can be difficult for many to distinguish at first glance.
Western diamondback rattlesnakes are generally large, with heavy bodies that average 5 feet long but can grow much longer. Western diamondback rattlesnakes are named for the distinctive diamond-shaped markings along their backs that are darker than the gray, yellow or pinkish base color. They also have a prominent rattle at the end of the tail. Timber rattlesnakes, by comparison, are smaller than their western counterparts. These snakes average 3 to 5 feet in length and have more slender bodies. Timber rattlesnakes lack a distinctive shape to their markings, which appear as dark bands that run along their backs. The snake's base color varies by region, ranging from dark gray to yellow.
Range and Habitat
Little geographic overlap exists between these two species. Timber rattlesnakes inhabit many eastern and southern states, ranging from central New England across to Texas, Oklahoma, Kansas and Nebraska. Western diamondback rattlesnakes, on the other hand, tend to be found in the Southwest. Their range spans from southern California to Texas and south into Mexico. Both species prefer rocky areas with plenty of crevices to conceal themselves in -- but western diamondback rattlesnakes reside in open or sparsely vegetated arid to semi-arid environments, while timber rattlesnakes live typically on forested hillsides.
Rattlesnakes are reputedly aggressive, but the bad rap is generally unearned and does not reflect the behavior of most species. Timber rattlesnakes, for example, tend to avoid confrontation with humans; in most cases they'll remain motionless or flee if possible when encountered. Western diamondback rattlesnakes are more aggressive overall; a diamondback will readily form a threat posture by flattening the body and rising into an S shape and rattling the tail. Even though diamondbacks tend to be more aggressive than timber rattlesnakes and are responsible for more snakebite deaths than any other American species, western diamondback rattlesnakes generally strike only in defense.
Both species are classified by the IUCN Red List of Threatened Species as species of "Least Concern," meaning that they are not threatened or vulnerable as of 2007. Even so, these species face challenges to their continued survival. Timber rattlesnakes are threatened by habitat loss and hunting, both for sport and for private pet collections, which has led to a decline in population throughout their native range. Though western diamondback rattlesnakes encounter similar threats, their reproductive success has allowed them to maintain their population.
- University of Michigan Museum of Zoology: Crotalus Horridus
- University of Michigan Museum of Zoology: Crotalus Atrox
- The IUCN Red List of Threatened Species: Crotalus Atrox
- The IUCN Red List of Threatened Species: Crotalus Horridus
- The Amphibians and Reptiles of Missouri; Tom R. Johnson