Natural History: Pygmy Rattle Snake

The Carolina Pigmy Rattle Snake, scientific name Sistrurus miliarius miliarius, is an extremely well equipped and fascinating snake. Its range is from the southern most part of South Carolina to the southeastern part of North Carolina. It is one of three subspecies of the Pigmy Rattle Snake, Sistrurus miliarius. The subspecies are differentiated primarily due to pattern deviation and geographical location. Populations of Dusky Pigmy Rattlesnakes, Sistrurus miliarius barbouri, extent all the way through Florida, and Western Pigmy Rattle Snake populations, Sistrurus miliarius streckeri, extend all the way to eastern Texas.

These snakes are rather small rattlesnakes compared to the genus Crotalus, reaching only a record size of 31 inches. They further differ from their Crotalus brethren based on their head shape and head scale pattern. Crotalus has a wider and broader head composed of numerous small scales, while Sisturus has nine large-scale plates on the crown of their head. Pigmy Rattlesnakes generally have a light brown to greyish coloration with dark brown blotches going down their backs and flanks. The patterning on miliarius miliarius is very clear-cut and vivid and it is often witnessed to have a reddish tint to it. The other two subspecies have more of a dusky or less vivid patterning.

These snakes possess a tiny rattle constructed by keratinous shed skin. Most other rattlesnake species will always utilize their rattles to ward off predators, however Sistrurus only irregularly does. When threatened sometimes individuals will sound off their miniscule rattle, while other times they will remain motionless. Many herpetologists go as far as categorize Sistrurus miliarius in a group with a few other rattlesnakes known as the “rattleless rattlesnakes”. Nonetheless, when used the small rattle will produce a slight buzzing sound that can only be heard from several feet a way. This causes many herpetologists to speculate as to why Pigmy Rattlesnakes have such a small rattle or even a rattle at all. Some hypotheses suggest that the snake’s small size, leading to infrequent shedding, results in the trifling size of their rattle. However, based on their reluctant use of their rattles and other morphological shortcomings, it is more widely thought that Pigmy Rattle Snakes represent a basal group to all rattle snakes. Therefore, Sistrurus is a frequent character in studies analyzing the origin of rattlesnake rattles. When juveniles, the tips of their tails are equipped with a vibrant yellow coloration that is used to lure in prey. When older this coloration fades, but their rattle gets larger. Some herpetologists further hypothesize the driving force of the origin of snake rattles is actually a lure for prey. There are herpetological studies that provide evidence of visual similarities between the tip of a snake rattle and arthropods (a typical prey choice of lizards, frogs, and many small mammals).

These snakes have the ability to be successful in a wide variety of habitats. However they typically prefer longleaf pine habitats due to the large abundance of burrows constructed by Gofer Tortoises and small mammals. Juveniles thrive off of a diet of insects and small lizards, and adults add on small mammals and birds to their diet. Pigmy Rattlesnakes utilize a largely hemorrhagic venom to immobilize their prey. Hemorrhagic venom is a composition of toxins that, when injected, result in excessive internal and external bleeding.

This venom is very effective to immobilize their small prey, however, in relation to deterrence of predation, venom is rarely used. Pigmy Rattlesnakes are typically unaggressive and, as briefly stated above, rely on their camouflage as their first line of defense. Witnessed aggressive behavior (frequency of strikes) is directly correlated with the vulnerability of its posture. When coiled, the snake typically does not strike unless relentlessly pestered. Conversely, when uncoiled the hostility of this snake is significantly increased. However, despite being primarily unaggressive, the invisible nature of this snake leads to many accidental human encounters. Consequently, this snake is responsible for a large number of snakebites in the southeastern United States. However, despite the numerous human envenomations, the venom from this snake poses a very small threat of fatality to humans, but will cause extreme discomfort.