Eastern Massasauga Rattlesnakes at Allerton Park

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When you think about the treasures of the U of I’s Robert Allerton Park near Monticello, you probably don’t think of endangered rattlesnakes. But scientists have recently confirmed that the eastern massasauga, a small, shy rattlesnake native to our region still inhabits parts of Allerton Park south of the Sangamon river.

Now, if the word “rattlesnake” brings to mind the monstrous creatures of old westerns, which lay in wait for unsuspecting cowboys, you’ll be gratified to know that the massasauga is a much smaller and more timid creature.

With adults averaging less than two feet long, the massasauga is one of the smallest rattlesnakes in North America. It is often confused with other common, non-venomous snakes but its tail is tipped with a rattle, which it will rattle as a warning when cornered. Other snakes mimic this action by shaking their tails but they do not have rattles.

Massasaugas use a variety of habitats, from old fields and savannas to floodplain forest, marshland and bogs. They are active from April through October, feeding on small rodents and sunning themselves during the day. In winter massasaugas hibernate, either in burrows created by other animals, especially crayfish, or under rock piles.

At the time of European settlement massasaugas were apparently abundant in the northern two-thirds of Illinois, with a range that extended from New York in the east to Ontario in the north and west into Iowa.

Habitat alteration, drainage of wetlands and intentional killing of snakes resulted in a swift decline for massasaugas in Illinois during the 1800s. Writing in 1893, one observer noted, “On the prairies of Illinois, before the country became thickly populated, these reptiles were extremely abundant, and the killing of two or three dozen in a season was not an unusual thing for a farmer’s boy. Now, in that same region, not one is seen in years.”

In 1994, massasaugas were listed as a state endangered species in Illinois, and are currently believed to hang on in only three or four small populations, including the one at Allerton Park.

There have been records of massasaugas at Allerton since the 1930s. Legend has it that rattlesnakes found north of the river, in the vicinity of the house and formal gardens, were moved to the restored prairie on the south side.

Recent searches for massasaugas organized by Eric Smith, a regional Heritage Biologist with the Illinois Department of Natural Resources, came up empty until Mosheh Wolf found a baby massasauga in 2000. In 2002, researchers from the U of I and the Department of Natural Resources captured an adult male, nicknamed Al, who was large enough to be implanted with a radio transmitter. In the ensuing years, Al has led researchers to two female snakes, which together have given birth to more than twenty young over this period. Tracking Al has also made it possible for Allerton managers to time their prairie burns so as not to put him and other massasaugas at risk.

Speaking of risk, I would emphasize that although Al is venomous, the risk he poses for people who enjoy Allerton’s natural areas is miniscule. Massasaugas prefer to avoid people, and have proven to be very good at doing so.

A special thanks to Chris Phillips, of the Center for Biodiversity at the Illinois Natural History Survey, and Fran Harty of the Nature Conservancy, for their help with today’s story.