Eastern Massasauga Rattlesnake (Sistrurus catenatus catenatus)

Michigan's Only Venomous Snake

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. They are listed as a "species of special concern" by the Michigan Department of Natural Resources, and are protected by state law.

Like many snakes, the first human reaction may be to kill the snake. But it is important to remember that 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.

The U.S. Fish and Wildlife Service is currently evaluating the Great Lakes population to determine whether it should be listed as a threatened species. In Michigan, it remains an important part of our natural history.

Was that a massasauga?

Status:Special Concern, it is protected by the State of Michigan and is a candidate for federal listing
Range: Entire Lower Peninsula,. Although once common, populations may be declining due to loss of wetland habitats and human harassment.
Habitat: During spring, Massasaugas use open shallow wetlands or shrub swamps. They can be found in crayfish towers or small animal burrows which are adjacent to drier upland open shrub forest sites. During summer, Massasaugas move upland to drier areas. Look for them "sunning" in open fields, grassy meadows or farmed sites.
Behavior: Sluggish, slow moving snake. It may strike if threatened.
Benefits:Eastern Massasauga rattlesnakes eat small mammals, amphibians and insects. The Massasaugas are eaten by eagles, herons and some mammals.
  • Massasaugas have thick bodies with colors that range from gray, grayish brown or brown. Its back has large dark brown blotches with smaller lighter brown patches on its sides. Young Massasaugas are similarly marked with brighter coloration.
  • This snake has a wide triangular head and eyes with slit shaped pupils.
  • Adults can be 18" to 30" in length.
  • Young Massasaugas have small yellow buttons or "rattles" at the tip of their tail. Adult "rattles" are grayish yellow, like pieces of corn kernels, on top of dark rings.
  • Snakes may bite to protect themselves.

Look alike Snakes:

  • The eastern milk snake and eastern hog-nosed snake are harmless.
  • A hog-nose snake will flare its head, coil, and may strike.

Eastern Massasauga Rattlesnake
(Sisturus catenatus)
Eastern Massasauga Snake (Sisturus catenatus)
Photo by: James H. Harding

Eastern Milk Snake
(Lampropeltis triangulum)
Eastern Milk Snake (Lampropeltis triangulum)
Photo by: James H. Harding

Eastern Hog-nosed Snake
(Heterodon platyrhinos)
Eastern Hog-nosed Snake (Heterodon platyrhinos)
Photo by: Earl Wolf

Click on an image to see a larger version.

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, study their habits.
  • 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.

Remember, not all snakes are venomous. Additional information is available on Michigan's snakes.

Radio Tracking Project
(photo by Matt Heumann)

Beginning the Spring of 2002, researchers used radio telemetry equipment to follow snakes at Indian Springs Metropark in Oakland County. This project is a cooperative effort between the Michigan Department of Natural Resources, the Huron-Clinton Metropolitan Authority (HCMA) and the U. S. Fish and Wildlife Service (USFWS). Telemetry uses a tiny radio transmitter surgically implanted into a snake. The signal is picked up by special monitoring equipment.

There are two primary objectives to the telemetry study. First, we seek clarification of the behavior of massasaugas in areas that include expansive upland open habitats such as old fields and savannahs. Second, we are interested in the behavior of massasaugas in areas of human use and how to manage conflicts between massasauga conservation and human recreation.

Eastern Massasauga Rattlesnake by Matt HeumannUp to 15 massasaugas will be implanted with transmitters. They will be monitored for two activity seasons to study their patterns of movement. Data on habitats the snakes are using and when they're using them will be collected. This work will also reveal corridors used and barriers perceived by the snakes. Work at this southern Michigan site will complement efforts conducted in fens in northern Indiana and in coniferous swamps farther north to provide a broader perspective of habitat needs and massasauga behavior across Michigan.

In addition to clarifying the basic biology of massasaugas, a component of this project will be to identify opportunities to promoting the conservation of the massasauga.

As of early April, seven snakes had been captured for the project. Snakes will be monitored regularly throughout the spring and summer, then periodically in the fall to establish hibernacula. If necessary, additional snakes will be implanted in spring 2003. All snakes will then be monitored in spring and summer 2003. Their transmitters would then be removed. Snakes added to the study that year would be followed to their hibernacula (wintering quarters) and transmitters removed in spring 2004.

The eastern massasauga rattlesnake population has declined throughout its range from western New York and southern Ontario, to Iowa and southward to Missouri. It is either included on lists of endangered and threatened species or watch lists in every state it occurs. The primary causes of its decline are habitat loss and persecution. The USFWS listed the massasauga as a candidate for the federal species list. Since massasauga are more common in Michigan than anywhere else in its range, the Natural Heritage Program has agreed to cooperate in a multi-state planning effort to describe how threats to the species will be minimized. The goal is to assure the long-term protection of massasauga populations and eliminate the need for federal listing.

2002 Survey

In order to ensure the long-term survival of Michigan's massasauga, an understanding of the distribution of local populations and critical habitats is necessary. In 2002, Michigan Natural Features Inventory (MNFI) conducted surveys in an attempt to gain such an understanding.

In winter 2002, Dr. Bruce Kingsbury, professor of biology at Indiana-Purdue University, and graduate student Michelle Standora identified 77 potential core areas for 2002 surveys. These sites, all on publicly-owned lands, were identified based on habitat quality and prior rattlesnake occurrences.

MNFI surveyed 40 sites associated with 27 of these core areas in addition to five sites associated with other MNFI projects. A total of 80 rattlesnakes were observed by survey participants. Seven others were observed by outside sources, yielding a total of 87 rattlesnakes from 19 different sites. Of these 19 sites, six were birthing sites consisting of 5 adult females and a total of 28 young-of-the-year.

Survey efforts will continue in 2003 with an increased focus on survey gaps and identification of hibernation sites. MNFI also hopes to supplement surveys on public lands with additional surveys on private lands.

Non-DNR Links

Herp Center (Indiana-Purdue University Fort Wayne)

Canadian Eastern Massasauga Recovery Team

Michigan Society of Herpetologists

Sistrurus catenatus catenatus (University of Michigan, Museum of Zoology)

Eastern Massasauga Rattlesnake (Wisconsin Dept. of Natural Resources)

Sistrurus catenatus catenatus (NatureServe)

Eastern Massasauga Rattlesnake (US Fish & Wildlife Service)

Related Documents
Eastern Massasauga Snake Occurrences Map PDF icon