Prairie Massasauga

Image of a massasauga
Species of Conservation Concern
Safety Concerns
Scientific Name
Sistrurus tergeminus tergeminus
Viperidae (venomous snakes) in the order Squamata (lizards and snakes)

The prairie massasauga is a medium-sized, dark rattlesnake with a short, thick body. General coloration is light gray to dark gray, with rows of dark to light brown blotches down the middle of the back and along both sides. The belly is generally light colored. The head is a thick diamond shape with dark stripes extending back from the eyes. The tail has a stubby rattle. Like other venomous snakes, they have “pits” on the sides of their heads, and the pupils are diamond-shaped (not round). The other rattlesnake of north Missouri, the timber rattlesnake, grows much larger and has a rusty stripe down its back.

Human deaths caused by its bite are rare, but studies show that the massasauga's venom is highly toxic, so it must be respected and classified as dangerous.

Similar species: This rattlesnake is extremely similar in appearance to the eastern massasauga (S. catenatus), and in Missouri the two are mainly identified based on geographical range: the prairie massasauga occurs in our northwestern corner and in some north-central counties, while the eastern massasauga — now considered extirpated from our state — once occurred along the Mississippi River floodplain north from St. Louis. The prairie massasauga used to be considered the same species as the eastern massasauga.

Two other rattlesnakes are known from Missouri, and they are not as rare as massasaugas. The timber rattlesnake (Crotalus horridus) occurs statewide, and adults are about 3 to 5 feet long.The western pygmy rattlesnake (Sistrurus miliarius streckeri), which does not exceed 20 inches in length, is not found in northern Missouri. It lives in counties bordering Arkansas and in the eastern Missouri Ozarks.

Common Name Synonyms
Massasauga Rattlesnake
Eastern Massasauga

Length: 18–30 inches.

Where To Find
Prairie Massasuga Distribution Map

Small numbers survive in north-central and northwest Missouri. Recently recorded in only Chariton, Lynn, and Holt counties.

Mainly found in bottomland or wet prairies dominated by cordgrass, sedges, bullrushes, and smartweeds, and lowlands by rivers, lakes, and marshes. They prefer places where there are numerous crayfish burrows providing shelter from predators and weather conditions. They require wetlands associated with river floodplains of north Missouri. Populations have declined because of habitat loss as wetlands were drained and floodplains and prairie were converted to farmland. Restoring wetlands along rivers, improving existing wetlands, and protecting this snake from being killed are the keys to the survival of this species.

Massasaguas feed primarily upon rodents (especially voles and deer mice) and small snakes such as gartersnakes, plus lizards. Most of the hunting occurs during the day, except in the hottest part of the summer, when this species becomes more active at night.

What were formerly two subspecies of "eastern massasauga" (Sistrurus catenatus) have been split into separate species. The massasauga population discussed on this page is now considered a subspecies of western massasauga (S. tergeminus) that is called the prairie massasauga (S. tergeminus tergeminus). Meanwhile, the eastern massasauga (S. catenatus), a candidate for federal endangered status, is likely extirpated from Missouri. It used to occur along the Mississippi River floodplain north of St. Louis. Both massasauga species are listed as endangered in Missouri. None can be injured, killed, or taken from the wild for any use.

Life Cycle

In summer, massasaugas live along the edges of wet prairies. They overwinter in burrows in moist lowland areas. They emerge from winter dormancy in mid-April. In early October, they migrate back to overwintering areas, in some cases traveling distances of over 1½ miles. Female massasaugas are believed to reproduce every other year. Mating occurs in late summer, and females give birth to an average of 4 to 10 live young.

Many of us fear rattlesnakes, so it’s a natural impulse to want to kill them — however, as we increase our understanding of how these snakes fit into the balance of nature, our knowledge and appreciation of these disappearing snakes makes us concerned for their survival.

Massasaugas hunt voles, mice, and other rodents, plus smaller snakes, keeping their populations in check. As a resident of marshy areas and moist prairies, this efficient predator thus has an important predatory niche within those habitats.

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Similar Species
About Reptiles and Amphibians in Missouri
Missouri’s herptiles comprise 43 amphibians and 75 reptiles. Amphibians, including salamanders, toads, and frogs, are vertebrate animals that spend at least part of their life cycle in water. They usually have moist skin, lack scales or claws, and are ectothermal (cold-blooded), so they do not produce their own body heat the way birds and mammals do. Reptiles, including turtles, lizards, and snakes, are also vertebrates, and most are ectothermal, but unlike amphibians, reptiles have dry skin with scales, the ones with legs have claws, and they do not have to live part of their lives in water.