Illinois Natural History Survey - University of Illinois

The Eastern Massasauga at Carlyle Lake

Few other animal groups are as persecuted as rattlesnakes. From old western movies where six-foot-long rattlers rear up to strike a cowboy on horseback to outrageous folktales of rattlesnakes chasing humans, a lot of bad press has been directed at rattlesnakes. In reality most rattlesnakes present very little threat to humans. They are much more likely to lay quietly and let you pass than they are to rattle or even flick their tongues. One species in particular is undeserving of the reputation as an aggressive killer. This is the massasauga or swamp rattlesnake, Sistrurus catenatus, one of two species of rattlesnakes found in Illinois (the other is the timber rattlesnake, Crotalus horridus). At less than two feet in length, the massasauga is one of the smallest rattlesnake species. It is also very secretive and not prone to bite even when disturbed.

At the time of European settlement, the massasauga was found throughout the northern two-thirds of Illinois. There are accounts of early travelers and farmers encountering 20 or more massasaugas in a single spring day. Within a very few years, however, habitat destruction and outright persecution reduced the Illinois range of the massasauga to a few widely scattered populations. As early as 1890 it was noted that the massasauga was in decline. Today there are only three or four populations remaining in Illinois. Only the population at Carlyle Lake in Clinton County is thought to be large enough to have any hope of surviving the next 20 years.

snake.jpg
Easterm massasauga (Sistrurus catenatus).

It is not clear when the Carlyle Lake population first became known to Illinois biologists. The first reference to massasaugas at Carlyle Lake that I am aware of is from Mike Morris, a herpetologist who compiled range maps for all Illinois amphibians and reptiles. His massasauga map from the early 1980s shows a dot in Clinton County at about the location of Carlyle Lake. However, it was not until 1991 that any attempt to keep records on the Carlyle massasaugas was initiated. It was then that Scott Ballard, District Heritage Biologist with the Illinois Department of Natural Resources (IDNR), began keeping track of when and where massasaugas were encountered at the lake. Scott's work showed that between 1991 and 1998 from 2 to 20 massasaugas were incidentally encountered each year. Unfortunately, Scott also discovered that some of these encounters were the result of snakes being hit by lawn mowers or automobiles and others were snakes killed by uninformed park visitors or landowners. In 1994, the massasauga was listed as endangered in Illinois and this resulted in increased interest in the welfare of the species. More recently, plans for commercial development at Carlyle have been presented by various government agencies and private groups. These development plans have caused the IDNR to step up its investigations into the status of the massasauga at Carlyle.

In response to this need, I started studying the massasauga at Carlyle Lake in the fall of 1998. The initial purpose of my study was to conduct a systematic survey for massasaugas at South Shore State Park, one of the two IDNR-owned or managed properties at the lake. In Illinois, massasaugas spend the winter hibernating underground in crayfish burrows, so I started my survey by looking for appropriate crayfish habitat. At Carlyle this is grassland where the water table is seasonally elevated. I identified a potential site and returned the following spring to start my research. I was lucky enough to have chosen an area that is used by a large number of massasaugas. I documented the timing of emergence and dispersal from the hibernation sites, and established baseline population data. My initial results indicate that massasaugas emerge from hibernation in crayfish burrows (a process called egress) in late March and remain in the general vicinity for up to 36 days. After that, they move out into their summer ranges to forage for food and locate mates. An in-depth analysis of the specific locations where massasaugas were found suggests that during egress massasaugas select locations closer to retreats (crayfish holes or logs) and shrubs compared to random locations. This proximity to cover may allow massasaugas to escape predation, especially from aerial predators, such as hawks.

In the next phase of my research at Carlyle I will attempt to locate as many hibernation sites as possible and further investigate timing of egress and population size. I will also radio-track 10 or more snakes to find out where they go when they leave the hibernation sites. The final product of these efforts will be a better picture of how many massasaugas live at Carlyle and how they utilize the various habitat types at the lake. This information will be used to direct commercial development away from the areas that are used by massasaugas. Hopefully, it will also be part of a larger management plan that includes purchase of additional habitat and educational programs that counter the "bad press" already in existence. Only through such a comprehensive plan does the massasauga have any real chance of continued existence at Carlyle Lake or in Illinois.

Christopher Phillips, Center for Biodiversity



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