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Eastern massasauga rattlesnakes, the only venomous snake in Michigan, are shy creatures that will avoid humans whenever possible. Also known as "swamp rattlers," they spend the vast majority of their time in year-round wetlands hunting their primary prey, mice.

The eastern massasauga, a rare sight for most Michigan residents, has been declining due to fragmentation and loss of wetland habitat. The massasauga is listed as threatened species by the US Fish and Wildlife Service under the Endangered Species Act.

Rattlesnake bites, while extremely rare in Michigan, can and do occur. Anyone who is bitten should seek medical attention immediately.

Report a massasauga observation

Report observations of possible snake fungal disease to the DNR Wildlife Disease Laboratory at 517-336-5030.

    • Keep your distance and observe it from a distance.
    • Use caution.
    • Remember it deserves a safe living space.
    • Do not pick it up.
    • Keep all pets away.
    • If you live or recreate in areas that are historic habitats of the massasauga, learn more about them.
    • Learn what to do if you or a pet is bitten:
      • If a pet, notify your veterinarian and immediately take pet to a veterinarian for treatment.
      • You are bitten, call 911 or contact your medical care provider or emergency room for further direction.
    • Report observations.

    Remember, not all snakes are venomous. There are several harmless species in Michigan.

  • Michigan's only venomous snake is a rare sight for most state residents. Historically, they could be found in a variety of wetlands and nearby upland woods throughout the Lower Peninsula. During the late spring, these snakes move from their winter hibernation sites, such as crayfish chimneys and other small mammal burrows in swamps and marshlands, to hunt on the drier upland sites – likely in search of mice and voles, their favorite food.

    Females give birth to eight to 20 young in late summer. The young snakes have a single "button" on their tails; a new rattle segment is added at each shedding of the skin, which occurs several times per year.

    The massasauga can be characterized as a shy, sluggish snake. Its thick body is colored with a pattern of dark brown, slightly rectangular patches set against a light gray-to-brown background. Occasionally, this coloration can be so dark as to appear almost black. The belly is mostly black. It is the only Michigan snake with segmented rattles on the end of its tail and elliptical, ("catlike") vertical pupils in the eyes. The neck is narrow, contrasting with the wide head and body, and the head appears triangular in shape. Adult length is 2 to 3 feet.

    These rattlesnakes avoid confrontation with humans; they are not prone to strike – preferring to leave the area when they are threatened. Like any animal, though, these snakes will protect themselves from anything they see as a potential predator. Their short fangs can easily puncture skin, and they do possess a potent venom. It is best to treat them with respect and leave them alone. The few bites that occur to humans often result from attempts to handle or kill the snakes. Any bite from a massasauga should receive prompt professional medical attention. When compared to other rattlesnakes found in the United States, the massasauga is the smallest and has the least toxic venom.

    Massasaugas are found throughout the Lower Peninsula, but not in the Upper Peninsula (thus there are no venomous snakes on the Upper Peninsula mainland.) They are becoming rare in many parts of their former range, throughout the Great Lakes area, due to wetland habitat loss and persecution by humans.