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massasauga snake © David Davis

Eastern massasauga rattlesnakes have heat-sensitive pits near their eyes that allow them to sense their prey.

Occupying the Wetlands from south Ontario to eastern Missouri

Also known as the “swamp rattler,” the eastern massasauga rattlesnake is a subspecies of the massasauga, which ranges from north Mexico to south Canada. The subspecies’ range is somewhat more limited: south Ontario to eastern Missouri. “Massasauga” is derived from the Chippewa language and translates as “great river-mouth,” presumably referring to the snake’s preference for wet habitats. Eastern massasaugas hibernate through winter and early spring in bogs, swamps and wet prairie environments, traveling up to 1.6 miles to drier summer habitats. They often winter in crayfish holes, which frequently flood, resting with their head above the water and body submerged. They also hibernate under logs, tree roots and in small mammal burrows. Unlike other rattlesnakes, they hibernate alone.

A pit viper, eastern massasauga rattlesnakes have heat-sensitive pits near their eyes that let them sense the presence of prey. They can also track prey by sight, vibration and heat. Eating mostly small mammals like voles, deer mice and shrews, the rattlesnake often strikes, injects its venom, then retreats and waits for the animal to die or be subdued before eating it. Its venom is highly toxic, but delivered in small doses. In humans, bites will produce swelling, nausea and intense pain. 

A candidate for the federal Endangered Species List, the eastern massasauga is listed as Endangered, Threatened or a Species of Concern in every state and province in its range. The main threat to the subspecies is loss and fragmentation of habitat.