Spotlight on: Eastern Massasauga Rattlesnake

There’s a certain mystique about snakes, especially the large or venomous ones. Some people are afraid of snakes to such an extent there’s a term for it: ophidiophobia. According to the Cleveland Clinic, one in 10 American adults and one in five teens deal with a specific phobia at some point in their lives, and the fear of snakes is one of the most common of these.

People may be afraid of snakes as a result of cultural beliefs or stories—they’re not positively mentioned in many movies and some mythologies view them as downright evil. Some studies suggest that humans may even have a “genetic fear” of snakes—that people have evolved to be afraid of them, as they were stronger physical and visceral threats when humans lived closer to the land.

Of course, some people also find snakes fascinating. And as scientists learn more about them, we are understanding more about their significance to their ecosystems. They’re a natural form of pest control, and they have an interesting and dynamic presence in the food web. Eastern massasauga rattlesnakes prey on other animals but can also be a food source for birds of prey, foxes, and other predators.

At Lincoln Park Zoo, we’re among those who find snakes fascinating—and the eastern massasauga rattlesnake is a favorite species at Regenstein Small Mammal-Reptile House.

Sensational Snakes

Eastern massasauga rattlesnakes are on the small side, with a length of around 2 feet on average. They can be distinguished by their heart-shaped heads, thick bodies, and gray-brown coloring; young snakes have even more vivid patterns. And of course, they have rattles at the end of their tails, which can be used to distract prey or warn predators to back off. The rattling sound is created when the hollow segments of the keratinized rattle bang together.

These snakes are small pit vipers that have a large range in Midwestern Great Lakes states as well as in Ontario, Canada. Although most people think rattlesnakes are desert animals, the eastern massasauga rattlesnake is often known as the “swamp rattlesnake” because it prefers wetter ecosystems. In fact, the word “massasauga” is a Native American (in the Ojibwe language) term that means “great river-mouth” and was used to describe the grasslands surrounding river deltas.

They eat small rodents, like mice and voles, but also prey on frogs and other snakes. They have enlarged and hollow fangs that inject venomous saliva into their victims. These are sit-and-wait predators, but they also use heat-sensing pits near their eyes, the ability to sense vibrations, and an adaptation that lets them detect chemicals, such as odors, to find food.

Eastern massasauga rattlesnakes hibernate alone, sometimes taking over crayfish burrows or small mammal burrows. They prefer hibernation sites near the water line. And like all rattlesnakes, they bear live young—up to 20 in one litter. Their reproductive success depends on their health and the availability of food.

The 2024 Michigan Trek

Every spring, Lincoln Park Zoo researchers go to a site in Michigan with representatives from other zoos and partner institutions that are members of the Eastern Massasauga Rattlesnake Species Survival Plan®. This site is owned by the Edward Lowe Foundation and hosts the SSP members as they monitor the snakes at this site, which is a central location where the snakes gather.

This year, the zoo’s Senior Director of Population Ecology Lisa Faust, Ph.D., and zoo Curator Dan Boehm attended. In total, 55 snakes were discovered, of which 17 had been caught and processed in previous years. Boehm explains that this is a respectable number, a result of favorable weather conditions that encourages the snakes to bask in the sun in visible areas. If it’s too cold and snowy or more than 80 degrees Fahrenheit, the snakes are harder to locate. And timing is key—if the monitoring takes place too early, the snakes may not yet have emerged from underground wintering locations. If it takes place too late, the snakes may already have dispersed and vegetation will have grown in, making them difficult to find.

The trip helps researchers understand snake demographics, population trends, disease risk, and the impact of wildlife management actions. More than 1,000 eastern massasauga snakes have been captured, tagged, and released as part of this program. It’s important work—but it’s also hard work for the few dozen researchers that attend. It involves 10-hour days, with participants hiking up to 5 miles a day in search of individual reptiles while trying to avoid ticks, mud, and dangerous plants.

“What’s memorable for me personally this year is that, in the nearly 20 years that I’ve been surveying the Michigan site, I always come home with poison sumac rash as it is everywhere and I am highly reactive,” Boehm reveals. “But each year I have become better at avoiding contact with that plant and this year I was successful at avoiding it entirely.”

He also got to see the northern lights, since he was in a rural area with a very dark sky.

Fear Factor

Unfortunately, the bias against snakes has real-world consequences. This species is listed as threatened by several different authorities, including the U.S. Endangered Species Act. Major threats to their survival are habitat loss, since they depend on ever-diminishing wetlands, and simple eradication. People fear rattlesnakes, so they kill them. Lincoln Park Zoo has worked with the Illinois Department of Natural Resources and the U.S. Fish and Wildlife Service on regional conservation measures.

Eastern Massasauga Snakes at Lincoln Park Zoo

If you come to Regenstein Small Mammal-Reptile House, you’ll be able to see an eastern massasauga snake in the front part of the building. Lincoln Park Zoo also has five more individuals behind the scenes. This species is solitary, so they prefer being alone. They are only paired for breeding.

Because of their “sit-and-wait” feeding strategy and the fact that they are cold-blooded animals, eastern massasauga snakes tend to stay still to conserve energy. They may not move for hours or even days, except to bask in sunlight or otherwise change positions to alter their body temperature. Lincoln Park Zoo keepers mimic seasonal cues by altering the day to night cycles to reflect what’s happening outside, like longer days and shorter nights in the summer. They also alter the temperatures inside the snakes’ habitat, up to 80 degrees F in summer, and as low as 50 degrees F in winter. They even mimic hibernation conditions by keeping snakes in complete darkness for two months at the height of winter.

What do they eat at the zoo? Adult eastern massasaugas receive a medium mouse every week or two, while younger snakes get smaller mice fed weekly. And like all animals at the zoo, the snakes receive enrichment. “That could be novel scents such as shed skins from other massasaugas, periodic modifications or rocks, plants, or branches. Or we might do a heavy mist of the entire enclosure to simulate a hard rain,” Boehm says. “It could also be scent trailing with their food item, which involves dragging a mouse across the ground in their enclosure and leaving the mouse in a tucked-away location for the snake to find.”

Take Action With Us

When it comes to saving eastern massasauga rattlesnakes, your best bet is to simply observe, don’t disturb. This is true of many species of wildlife, but few are as feared as venomous snakes. If people leave the snakes alone, they can survive in peace, and humans can enjoy the biological diversity that makes this world such an exciting place to live.