Eastern Massasauga Rattlesnake (Sistrurus catenatus catenatus)

Michigan's Only Venomous Snake

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.

What do I do if I see a massasauga?

  • 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, contact 911 or contact your medical care provider or emergency room for further direction.
  • Report observations.
  • More snake safety tips and snake bite treatment information: http://mnfi.anr.msu.edu/emr/safety.cfm

Remember, not all snakes are venomous. There are several harmless species that look similar to the massasauga rattlesnake.

All snakes play an important role in the ecosystem. Some may eat insects, others like the massasauga consider rodents a delicacy and help control their population. Snakes are also a part of a larger food web and can provide food to eagles, herons, and several mammals.

We can easily learn to live with these creatures. When you encounter a snake, leave it alone. In most cases, the snake will move to different areas. If pets are in the area, it is important to confine them until the snake moves on. Most often snakes do not wander into areas with little vegetation. The most likely period to encounter snakes in the open is early spring or mornings when they can be found sunning themselves.

Additional Information

Life History & Michigan History

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 8 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, ("cat like") 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.