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Endangered Species Program
Conserving and restoring threatened and endangered species and their ecosystems
Eastern Massasauga (Sistrurus catenatus)
The eastern massasauga is a small, thick-bodied rattlesnake that lives in shallow wetlands and adjacent uplands in portions of Illinois, Indiana, Iowa, Michigan, Minnesota, New York, Ohio, Pennsylvania, Wisconsin, and Ontario. The eastern massasauga has been declining over the past three decades due to loss and fragmentation of its wetland habitat. Throughout its range, biologists have confirmed that less than half of the eastern massasauga’s historical populations still exist. We know of 558 historical populations, of which 211 have been lost and the status of 84 is uncertain – with the likelihood that many of those populations have also been lost. We have information indicating that 267 of the historical populations still exist today. Most of those populations are in Michigan and Ontario, Canada. New York, Pennsylvania, Ohio, Indiana, Illinois, Wisconsin and Iowa have fewer populations.
Listed as Threatened
The U.S. Fish and Wildlife Service listed the eastern massasauga rattlesnake (Sistrurus catenatus) as threatened under the Endangered Species Act. We also determined that designating critical habitat for the eastern massasauga is not prudent.
The Service listed the eastern massasauga as threatened because of loss of populations throughout its range, declines in the number of individuals within those populations and the fact that threats will continue to cause declines into the future. If we continue to lose eastern massasauga populations, the species is likely to face extinction in the future.
We prepared a Species Status Assessment to assess the eastern massasauga’s current and projected future ability to survive. The analysis predicts a continuing decline in the number of eastern massasauga populations. We know that 38 percent of historical populations have been lost as of 2014 and the status of another 15 percent is uncertain. Our analysis projects a 90 percent reduction in number of populations over the next 50 years. The southwestern portion of the snake’s range will see the most severe declines with a predicted 97 percent loss of historical populations over the next 50 years. In addition to the loss of populations, we expect the extent of species’ range will shrink by more than 80 percent over the next 50 years as populations are lost.
Life History and Ecology
Eastern massasaugas have been found in a variety of wetland habitats, including bogs, fens, shrub swamps, wet meadows, marshes, moist grasslands, wet prairies, and floodplain forests. They will shift the habitats they use, depending on the season. Generally, they use wetlands in the spring, fall, and winter. In summer, snakes migrate to drier, upland sites, ranging from forest openings to old fields, agricultural lands and prairies.
Females give birth to litters of 5 to 20 live young in August or early September. Female massasaugas reach sexual maturity at three or four years of age. They have been reported to reproduce both annually and biennially in different parts of their range. Massasaugas usually hibernate in wetlands in crayfish or small mammal burrows. Hibernation sites are located below the frost line, often close to groundwater level. The presence of water that does not freeze is critical for suitabile hibernaculum.
Massasaugas feed primarily on small mammals such as voles, moles, jumping mice, and shrews. They also will eat other snake species and occasionally birds and frogs. Young snakes depend more on cold-blooded prey, particularly frogs. Natural predators for the massasauga, particularly the eggs and young, include hawks, skunks, raccoons, and foxes.
Species Survival Plan
A Species Survival Plan® is a collaborative science-based management program of the Association of Zoos and Aquariums (AZA).
Conservation and Research
Survey and Management Guidances
Archives: Chronological list of previous Federal Register publications, with associated information materials, and other actions pertaining to the Endangered Species Act status of the eastern massasauga.
Last updated: March 12, 2018