Sistrurus – Ground rattlesnakes

The genus Sistrurus is a group of small to medium-sized venomous pit vipers, closely related to rattlesnakes (Crotalus) and found primarily in North America, especially in the United States and parts of northern Mexico. Like their larger cousins, Sistrurus snakes have a distinctive rattle at the end of their tails, which they use to warn potential threats — but they’re generally more secretive, less aggressive, and often less dangerous to humans due to their smaller size and lower venom yield.

One of the key features that separates Sistrurus from their Crotalus relatives is the scalation on their heads. Sistrurus species have nine large scales on top of the head, similar to non-venomous snakes, while Crotalus species have smaller, more fragmented head scales. Like all pit vipers, Sistrurus snakes have heat-sensing pits between the eyes and nostrils to help them detect warm-blooded prey — even in total darkness.

Physically, these snakes tend to be thick-bodied and relatively short, with adult sizes typically ranging from 40 to 80 cm (16 to 32 inches). Their patterns are usually composed of dark blotches or spots running down the back, and coloration varies from gray and brown to reddish tones, depending on the species and habitat. Their cryptic patterns allow them to blend seamlessly into leaf litter, grasslands, or forest floors, making them hard to spot unless they move or rattle.

While these snakes are venomous, bites are rare and usually not life-threatening to healthy adults, thanks to their smaller venom glands and reclusive nature. Still, they should be treated with caution and respect. Their venom is primarily hemotoxic, affecting blood and tissue, but it’s also being studied for possible medical applications, including blood pressure regulation and clot-dissolving therapies.