BioKIDS home

Kids' Inquiry of Diverse Species


Sistrurus catenatus

What do they look like?

Eastern Massasauga rattlesnakes are members of the pitviper group. This large group of species are members of a larger group, the vipers. Vipers all have enlarged, hollow fangs at the front of their mouth which are used to inject a modified saliva into their prey. This saliva is venomous and causes their prey to die. The gaping of the mouth as they bite causes the fangs to swing forward, jabbing the prey, then muscles in their head inject the venom. Most vipers wait until their prey are dead before eating them. Pitvipers also have sense organs on either side of their head, the 'pits', that detect heat. This is important because pitvipers tend to eat warm-blooded prey and they use their pits to locate them. Some pitvipers are known as 'rattlesnakes' because they have a series of segments at the end of their tail that are loosely connected and make a hissing rattle sound when vibrated by the snake. New rattle segments are added each time the snake sheds its skin, so by counting the rattles one can estimate how old the snake is. Rattle segments can be lost, though, so if a snake has 8 rattle segments it may well be more than 8 years old. All rattlesnakes also have cat-like pupils which are elliptical and oriented vertically in the eye. (Harding, 1997)

Eastern Massasauga rattlesnakes are thick-bodied, medium-sized snakes, ranging in length from 47 to 100 cm as adults. This snake is marked with rows of dark, irregular blotches running the length of their back on a background color of gray, gray-brown, or brown. These dark blotches, and dark stripes on the tail, are often outlined in a lighter scale color, making them stand out against the background color. Many are strikingly beautiful. Their coloration makes them very difficult to see in the places where they bask or hide. Belly color is usually black with light mottling and their heads are triangular in shape. Some individuals are almost completely black. The scales are keeled (with a raised ridge down their center) and males are slightly longer than females. Newborn eastern massasauga rattlesnakes are born at 18 to 25.6 cm in length. They are similar to the adults but overall lighter in color and have only a single 'button' of a rattle. At birth young Eastern Massasauga rattlesnakes are capable of using their fangs and venom. (Harding, 1997)

These snakes are sometimes confused with eastern timber rattlesnakes, which have tails that are almost completely black. Eastern Massasauga rattlesnakes have striped tails. (Harding, 1997)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    47 to 100 cm
    18.50 to 39.37 in

Where do they live?

Eastern Massasauga rattlesnakes are native to the Nearctic region. They are found throughout the central United States, from southern Canada to western Arizona, south to the Gulf Coast of Texas, and east to Pennsylvania. (Harding, 1997)

What kind of habitat do they need?

Eastern Massasauga rattlesnakes are usually found in damp lowland habitats, including bottomland forests, swamps, bogs, fens, marshes, sedge meadows, and wet prairies. The name 'massasauga' means 'great river mouth' in the Chippewa language. These habitats are used by massasaugas from early fall to late spring. During the spring and summer months these snakes often move into drier, more upland habitats, such as grasslands and farm fields. (Harding, 1997)

How do they reproduce?

Eastern Massasauga rattlesnakes mate in the spring and fall. The females hold the babies inside their bodies for about 3.5 months then, rather than laying eggs as some snakes do, they give birth to live young. Females give birth to their 5 to 20 young in abandoned mammal burrows or fallen logs while living in their drier, summer habitats. Young snakes become sexually mature (able to have babies) in their third or fourth year. (Harding, 1997)

  • How often does reproduction occur?
    Females reproduce only every other year.
  • Breeding season
    Eastern Massasauga rattlesnakes breed in the spring and fall, they give birth in August and early September.
  • Range number of offspring
    5 to 20
  • Average gestation period
    3.5 months
  • Range age at sexual or reproductive maturity (female)
    3 to 4 years
  • Range age at sexual or reproductive maturity (male)
    3 to 4 years

Female Eastern Massasauga rattlesnakes nurture and protect their young inside of their bodies while they're developing. The young remain near their mother for a few days after birth and then move away (disperse).

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

How long do they live?

Eastern Massasauga rattlesnakes have been known to live in captivity for 20 years, but lifespan in the wild is unknown. (Harding, 1997)

  • Range lifespan
    Status: captivity
    20 (high) years

How do they behave?

Eastern Massasauga rattlesnakes are active from April through late fall. They hibernate through the cold months alone or in small groups, often in crayfish or mammal burrows in lowland habitats. Hibernation sites are often close to water level and below the frost line. They return to the same hibernation site year after year. They can swim well, but spend most of their time basking on high ground, such as on muskrat lodges, grass clumps, or rocks. They are most active during the day but may become more active in the morning and evening during the hot months of summer. Eastern Massasauga rattlesnakes tend to stay in relatively small home ranges.

How do they communicate with each other?

Eastern Massasauga rattlesnakes may communicate among themselves with chemical and physical cues, especially during breeding. These snakes detect prey with their sense of smell and with the heat-sensitive pits found on their faces. They are also sensitive to vibrations and have relatively good eyesight. Rattlesnakes also communicate warning signals and aggression to attackers with their rattling tail and by coiling up and striking. (Harding, 1997)

What do they eat?

Eastern massasauga rattlesnakes eat mainly small mammals such as voles, white-footed mice, jumping mice, and shrews. They sometimes also take other snakes, frogs, birds, bird eggs, and insects, especially when they are younger and smaller. Young eastern massasauga rattlesnakes entice frogs and toads to come closer by twitching their tail tips. These snakes usually strike their prey, then wait for them to die before eating them, but prey that aren't likely to fight back, such as baby mice or frogs, may be eaten without using venom. (Harding, 1997)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • mammals
  • amphibians

What eats them and how do they avoid being eaten?

Some large snakes, such as racers and milk snakes, may eat rattlesnakes. Hawks, herons, raccoons, and foxes may be able to kill them as well, and deer and pigs will trample rattlesnakes when they see them. However, by far the biggest threat to eastern massasauga rattlesnakes is humans, who have relentlessly pursued and killed these snakes throughout their range. Eastern massasauga rattlesnakes mainly avoid confrontation, they are usually not aggressive. They rely on their camouflage coloration to avoid being seen and will most likely freeze when approached. If an enemy comes too close these snakes will attempt to escape or will vibrate their tail as a warning. Most eastern massasauga rattlesnakes are hesitant to strike unless seriously harassed. (Harding, 1997)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

These rattlesnakes are very important in controlling populations of rodents and other small mammals in their natural habitats. (Harding, 1997)

Do they cause problems?

Rattlesnake bites to humans are rare, but are potentially dangerous. Most people who are bitten by rattlesnakes have been attempting to hurt or handle them. Eastern Massasauga rattlesnakes have a potent venom but have relatively short fangs that often fail to penetrate clothing and can deliver only small amounts of venom with each bite. Rattlesnake bites are painful, with swelling and tissue damage near the bite site. Anyone who has been bitten by a rattlesnake should stay calm and seek immediate medical attention (NOT try to cut open the wound and suck it out, a popular folklore). Most people recover completely from rattlesnake bites.

Most rattlesnakes are shy and retiring and killing rattlesnakes is entirely unnecessary. Rattlesnakes found near homes may be removed to other areas, though it is likely that it is the humans who have intruded on a snake's traditional habitat. (Harding, 1997)

  • Ways that these animals might be a problem for humans
  • injures humans

How do they interact with us?

Eastern Massasauga rattlesnakes are very important in controlling rodent populations throughout their range. Research on rattlesnake venom helps develop new medical technologies to treat heart conditions and other diseases. (Harding, 1997)

Are they endangered?

Eastern Massasauga rattlesnakes are threatened or endangered throughout their range, as a result of human persecution and habitat loss. Their wetland habitats are often lost to draining projects and their upland habitats to agriculture and suburban development. Michigan is one of the few places where Eastern Massasauga rattlesnakes seem to be doing reasonably well, though populations are declining here as well. The status in Michigan is 'special concern'. In the USA, this rattlesnake is a candidate species being considered for federal protected status.


Tanya Dewey (author), Animal Diversity Web.


Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Michigan: The University of Michigan Press.

University of Michigan Museum of ZoologyNational Science Foundation

BioKIDS home  |  Questions?  |  Animal Diversity Web  |  Cybertracker Tools

Dewey, T. . "Sistrurus catenatus" (On-line), Animal Diversity Web. Accessed May 23, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
Copyright © 2002-2024, The Regents of the University of Michigan. All rights reserved.

University of Michigan