The Eastern Massasauga Rattlesnake is the only native species of rattlesnake in Michigan. This species is also the only venomous snake found within the state’s borders. The Eastern Massasauga is federally protected as a threatened species under the U.S. Endangered Species Act, which makes it unlawful to harm, harass, or kill the snake without a special permit.
Identifying Michigan’s Only Native Rattlesnake
The Eastern Massasauga Rattlesnake, Sistrurus catenatus, is a small to medium-sized snake, with adults typically measuring between 2 to 3 feet in length. It possesses a thick, stout body and a head that is distinctly triangular, which is characteristic of pit vipers. The coloration is generally gray or light brown, featuring a distinct pattern of large, dark brown or black blotches that run down the center of the back.
These dark blotches are often edged in white and may resemble an intricate bowtie or figure-eight pattern. As a pit viper, the massasauga has heat-sensing pits located between its eyes and nostrils, and its eyes contain vertical, slit-like pupils. The most recognizable feature is the rattle at the end of its tail, which is composed of interlocking segments of keratin.
The sound of the massasauga’s rattle is often described as a faint, sharp buzz, sometimes compared to a bee stuck in a spiderweb. This is different from the louder, sustained warning of larger rattlesnake species. Hatchlings are born with a single segment, known as a button, and add a new segment each time they shed their skin.
Geographic Range and Habitat
Historically, the Eastern Massasauga Rattlesnake was found throughout the Lower Peninsula of Michigan, though its population has declined significantly due to habitat loss. Today, Michigan is considered a stronghold for the species, with populations concentrated in specific regions, primarily across the Lower Peninsula. Areas with confirmed sightings include a cluster of counties in the southeast, such as Oakland, Livingston, and Jackson, as well as counties in the southwest and northern Lower Peninsula.
The species is strongly associated with wetland habitats, earning it the nickname “swamp rattler”. Its preferred environments include open wetlands like bogs, fens, wet meadows, and marsh edges. They rely on these specific wetland areas for hibernation during the cold months, often utilizing crayfish or small mammal burrows that extend below the frost line and are close to groundwater.
The snakes often move to drier, adjacent upland habitats, such as old fields or forest openings, during the summer months for foraging and gestation. This seasonal movement between wetland and upland areas means they require a mosaic of interconnected habitats to survive. Their reclusive nature and the fragmentation of their required habitat are the primary reasons why they are rarely encountered by the average person.
Understanding Risk and Safe Practices
The Eastern Massasauga is known for its shy and non-aggressive temperament, preferring to remain hidden or flee when approached by a human. Bites to humans are extremely infrequent in Michigan and typically only occur when the snake is provoked, handled, or accidentally stepped on.
The massasauga’s venom is hemotoxic, meaning it affects the blood and tissues, but fatalities are exceptionally rare because the snake’s small fangs deliver a limited volume of venom. If a rattlesnake is encountered, the most important action is to remain calm, stop moving, and slowly back away to give the snake ample space to retreat.
Actionable safety practices include staying on marked trails and avoiding stepping or reaching into areas where the ground is obscured by thick vegetation or crevices. Because the Eastern Massasauga is a federally threatened species, it is illegal to kill, capture, or harass the snake. If a bite does occur, the immediate course of action is to seek emergency medical attention, as a hospital visit is necessary for proper treatment.