Sistrurus species differ from the larger rattlesnakes of the genus Crotalus in a number of ways. They are smaller in size, but also their scalation is different: Sistrurus species have nine large head plates (same as Agkistrodon), whereas with Crotalus (and almost all other viperids) the head is mostly covered with a large number of smaller scales. Sistrurus species have a relatively small rattle that produces more of a high-pitched, buzzing sound than a rattle, like Crotalus.
Eastern Massasauga (S.c. catenatus): Adults 24" to 36" in length. Color light gray to grayish brown, with median row of darker blotches on back; typically with three rows of similar but smaller blotches on sides. Wide head, with enlarged scales between and in front of eyes. Narrow neck, and stout body, and keeled scales. Eyes with vertical pupils.
Desert massasauga (S. c. edwardsii): This subspecies is more slender and smaller than S. c. tergeminus, reaching a maximum length of 53 cm.
The color pattern consists of a light gray or white base color, with dark gray or gray-brown blotches. They have a distinctive, dark stripe that runs along the side of the head which passes over the eye. Their rattles are significantly higher pitched than those of larger species of rattlesnake, sometimes giving them the nickname buzztail.
Compared to S. c. tergeminus, it is paler in color and its belly is nearly white. Midbody, it has 23 rows of dorsal scales instead of 25, as well as fewer ventral scales and dorsal blotches.
Western massasauga (S. c. tergeminus): Adults range in size from 35 cm to 91 cm. The standard length for 43 male and 63 female adult specimens was 68 cm. An average length of 46-66 cm, with a maximum of 88.3 cm.
The color pattern is similar to that of S. c. catenatus, but paler: the dark brown blotches contrast strongly with the tan-gray or light gray ground color. The venter (belly) is light with a few dark markings.
Southern Hognose Snake
Found in North America from southeastern Ontario (Canada) and western New York State southwest to southeastern Arizona (USA) and northern Tamaulipas (Mexico). In Mexico, isolated population exist in southern Nuevo León and north-central Coahuila. It occurs in various habitats ranging from swamps and marshes to grasslands, usually below 1500 m altitude. The type locality given is "... on the prairies of the upper Missouri
The venom of rattlesnakes contains specialized digestive enzymes that disrupt blood flow and prevent blood clotting. Severe internal bleeding causes the death of the small animals that this snake eats. After envenomation, the rattlesnake is able to withdraw from the dangers of sharp toothed prey animals until they are subdued and even partially digested by the action of the venom.
S. c. catenatus is rather shy and avoids humans when it can. Most massasauga snakebites have occurred after people deliberately handled or accidentally stepped on one of these animals. Both of these scenarios are preventable by avoiding hiking through areas of low visibility (in rattlesnake country) when not wearing shoes and long pants, and by leaving the massasaugas alone when they are found. There are only two recorded incidents of people dying from massasauga rattlesnake bites and in both cases they did not receive proper treatment. In at least one of these cases, the victim was a young child.