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Eastern Massasauga

Sistrurus catenatus

Family: Viperidae

COSEWIC status:
  • Endangered (Carolinian population)
  • Threatened (Great Lakes / St. Lawrence population)
SARA status:
  • Endangered (Carolinian population)
  • Threatened (Great Lakes / St. Lawrence population)
IUCN status:
  • Least Concern


The Eastern Massasauga is a pygmy rattlesnake; most adults are only 60–75 cm long. It is grey to brownish with saddle- or butterfly-shaped darker brown blotches on the back that alternate with smaller blotches on the sides. The belly is black with scattered light markings. The scales are keeled (ridged down the centre), which gives the snake a rough appearance. The Eastern Massasauga has vertical pupils, heat sensing pits between the eye and nostril and a triangular head with three dark stripes running down each side. This snake is most easily identified by its rattle, which is made up of interlocking segments that are added one by one when the snake sheds its skin, one to three times a year. However, the rattle can break off and may not always be apparent.

Similar Species

Since the Timber Rattlesnake is extirpated, the Eastern Massasauga is the only rattlesnake that remains in Ontario. The Eastern Foxsnake, Eastern hog-nosed Snake, Eastern Milksnake and Northern Watersnake superficially resemble the Eastern Massasauga. Further, the Eastern Foxsnake and Eastern Milksnake vibrate their tails when threatened, mimicking a rattlesnake. None of these species have a rattle, vertical pupils, heat-sensing facial pits or the distinct butterfly-shaped blotches on their back. The Eastern Milksnake has smooth scales, and those of the Foxsnake are only weakly keeled. The Eastern Hog-nosed Snake has an upturned snout.


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In Canada, the Eastern Massasauga occurs only in Ontario. It has been extirpated from much of its previous range in southwestern Ontario and is now restricted to the eastern shore of Georgian Bay, the northern Bruce Peninsula, a small population on the Niagara Peninsula and another very small population in the Windsor area. In the United States, the Eastern Massasauga occurs in the Great Lakes region in western New York and Pennsylvania west to Iowa and Missouri, although it has become rare in many of the states in which it is found.


Eastern Massasaugas are generally associated with water or lowland habitats and are rarely found more than 50 km from the Great Lakes. In Ojibwa, Massasauga means “great river mouth.” The Eastern Massasauga is a habitat generalist at the landscape scale and can be found in forests, meadows, shoreline habitats, wetlands, rock barrens, grasslands and old fields. The species requires very specific microhabitat features within these habitats for thermoregulation, gestation and hibernation.


In Canada, Eastern Massasaugas reach sexual maturity in three to six years and females only breed every two to three years. Individuals can live for more than 15 years. They breed from late July to early September and females give birth to 3–20 live young the following year in late summer. At birth, the young are 16–24 cm in length and instead of a rattle they are born with a cream to yellow “button” at the end of their tail. Like all rattlesnakes, the Eastern Massasauga is a pit viper and a heat-sensitive pit located on each side of the head between the eye and nostril allows the snake to see a thermal image of its environment. Its heat-sensitive pits and venom make the Massasauga a very effective predator of small mammals, its primary prey. Eastern Massasaugas prefer to remain motionless and rely on their camouflage to avoid interaction with predators and people. If provoked, they usually rattle and/or retreat under nearby cover. This snake will typically bite in defense only if it is harassed, handled or stepped on. Only two people have ever died in Canada from a Massasauga bite, both more than 60 years ago. However, anyone who suspects they may have been bitten should seek medical assistance.


Loss and fragmentation of habitat is an ongoing threat to this species throughout its range. Unfortunately, many people still kill rattlesnakes on sight, while others collect them illegally for the pet trade. Road mortality is probably the most severe threat to this slow-moving species, even in protected areas. People can safely live near Eastern Massasaugas.

Additional Information About This Species In Canada