A venomous snake once found throughout Illinois was listed last week as a threatened species under the federal Endangered Species Act.
The eastern massasauga rattlesnake, also known as the “swamp rattler,” produces venom more toxic than most other rattlesnakes. However, the snake is known to be timid and more likely to flee rather than fight when confronted. The snake reportedly bites one or two people on average each year in Michigan and Ontario, Canada, where the largest populations live, according to the U.S. Fish and Wildlife Service, the agency which made the announcement Thursday.
The designation indicates a danger of extinction in the “foreseeable future,” according to Louise Clemency, a USFWS field supervisor. “When we assessed the populations we know of and the threats acting on them, we found there were still some viable populations remaining in the next 50 years, but there are many fewer populations and they’re on the downward decline,” Clemency said.
The USFWS said current populations of the snake have plummeted by nearly 40 percent within their range of Midwestern and Eastern states, extending from Illinois to New York and north to Ontario, Canada. The decline was noticed when the agency compared recent surveys with historical data going back to the mid-19th century.
The species, which grows to about two feet in length, prefers wet prairies, marshes and lowland areas near rivers. As wetlands are drained for farming, urban development and roads, the snake’s habitat is greatly reduced and fragmented, according to the environmental nonprofit Center for Biological Diversity.
In the 1961 book “Amphibians and Reptiles of Illinois,” herpetologist Phil Smith documented scattered populations of eastern massasauga rattlesnakes within 25 of about 80 counties in the north and central portion of Illinois.
By the late 1990s, only one healthy population was found at Carlyle Lake in Clinton County and “very small” populations were found in five other counties: Lake, Cook, Will, Piatt and Madison, according to the Illinois Department of Natural Resources, which lists the snake as endangered.
The USFWS now believes Illinois’ last wild population lives at Carlyle Lake, located about 280 miles south of Chicago.
The Lincoln Park Zoo joined conservation efforts to protect eastern massasaugas in 2009. In collaboration with the USFWS and IDNR, the zoo took in the last remaining population of the species in Cook County and individual snakes from the Carlyle Lake population. Since the zoo joined the project, 20 eastern massasaugas have been born at the zoo.
Two are currently on display at the Regenstein Small Mammal-Reptile House.
Eastern massasaugas play important ecological roles as both predator and prey, said Lisa Faust, the Lincoln Park Zoo's vice president of conservation and science.
“They're important because they're sitting in the middle of the food chain,” Faust said. “They both feed on things and feed things, like birds of prey, and they're an important link within a varied wetlands ecosystem. By managing habitat for massasaugas, you're restoring habitat for several other species that depend on it.”
Under the new federally protected status, it's illegal to kill eastern massasaugas, but the USFWS emphasizes “safety always comes first” and to protect oneself if threatened.
According to the USFWS, “a large portion” of snakebites from massasaugas are caused by someone intentionally harassing or accidentally stepping on the snake.
“If people encounter a massasauga rattlesnake, we encourage them to step back and leave the area,” Clemency said. “They will generally retreat.”
The eastern massasauga rattlesnake is the second venomous snake to be listed under the Endangered Species Act, enacted in 1973. The New Mexican Ridge-Nosed rattlesnake was listed as threatened in 1978.
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