Madison Area Herpetological Society

Rattlesnakes in Wisconsin: A Historical and Conservation Perspective

Rattlesnakes in Wisconsin: A Historical and Conservation Perspective
By Eric Roscoe

The sound of a rattlesnake sounding off its rattle is perhaps one of the most unmistakable sounds in nature, and very often is also one which elicits an especially strong fear response from many people as an instant warning of impending danger. But why then have these snakes become long popular in the United States when a single bite can cause permanent injury, disfigurement, or even death? Those all sound like terrible, ugly things to be avoided. Early North American travelers and settlers through modern day civilizations alike have heard or listened to, and lived with rattlesnakes, as well as some of North America’s other venomous snake species for centuries while living, working, and settling into new areas of the country, and have become quite familiar with these venomous reptiles in a number of ways, both positive and negative. Indeed, rattlesnakes have held significant cultural and historical significance throughout North America for centuries, with perhaps one of the earliest symbolic references being from the use of the Colonials during the Revolutionary War in the form of the well-known Gadsden Flag depicting a coiled timber rattlesnake (Crotalus horridus) with the snake’s rattle’s original intended message “Don’t Tread On Me”. Even today, rattlesnakes continue to play important symbolic and conservation related roles in the use of our United States military, and various political and social movements throughout the U.S as well as even on social media and the Internet through such regular promotions as “Rattlesnake Friday”, among many others. Rattlesnakes have even been depicted on U.S. currency as well, and were even runner ups to the bald eagle as our nation’s national symbol.

Rattlesnakes in general are a large, and diverse group of most often medium sized to large, heavy bodied venomous pit vipers from the family Crotalidae indigenous to the Americas depending on the exact species and subspecies. Approximately thirty five recognized species of these snakes are currently recognized across two genera, Sistrurus, or the pygmy and ground rattlesnakes, and Crotalus, or the typical rattlesnakes, as well as approximately 65 to 75 recognized subspecies thereof altogether. Perhaps the most obvious and recognizable features of their snakes are their multi-segmented rattles at the ends of their tails comprised of loosely connected buttons which are highly modified scales through thousands or even millions of years of evolution with the original designated purpose of warning potential predators and other larger animals of their presence to avoid predation or trampling. Interestingly enough, when born, neonate rattlesnakes possess only a single button, in which subsequent segments are added each time the snake sheds its skin and grows, which may be multiple times each year. Thus, along with the fragile nature of these snake’s rattles which leads to them often breaking, are the reasons why it is unreliable to determine a rattlesnake’s age upon the number of segments a given snake has. Lastly, heat sensitive loreal pits, located on each side of the snake’s head or face between the eye and nostril also characterize rattlesnakes and other pit vipers.

In Wisconsin, there are currently 22 recognized species of snakes, the vast majority of which are harmless and/or nonvenomous. Of these, only two species are venomous, and both of their ranges, abundances, and distributions have been reduced drastically from historic levels prior to 1880. These two species are the timber rattlesnake (Crotalus horridus), and the eastern massasauga (Sistrurus catenatus). Both of these species will be discussed in further detail below. Both of these species were historically very abundant in Wisconsin, and the first mention of rattlesnakes in the state was by Hennepin during his travels up the upper Mississippi Riverway in 1680. To give some overall idea of the historical prevalence of rattlesnakes throughout much of Wisconsin, it can be noted that many early travelers to the state, including Marryat, believed that there may have been no other place in America where the two respective species were larger and more numerous than in Wisconsin, and those who have made overland trips from one area of the state to the other often witnessed both species along their ways.

Despite Wisconsin’s, as well as much of the Midwest’s and other state’s elsewhere fewer number of venomous snake species and their abundance, as well as herpetofauna diversity in general relative to more diverse regions of the U.S. such as the southwest and southeast, rattlesnakes nevertheless have played, and continue to play important roles In Wisconsin and elsewhere as either currently state endangered or protected wild animals. However, much of the available data on historical rattlesnake abundance in Wisconsin came from newspaper accounts rather than formal scientific papers on reptiles in Wisconsin, and oftentimes, insufficient details were provided to determine the species, although such factors as range, habitat, and the snake’s size and dimensions have been used to deduce the most likely candidate. As an example, the timber rattlesnake never occurred east of Madison, even historically, any references to rattlesnakes from there on were more likely to have been the eastern massasauga.

Wisconsin’s Species

The timber rattlesnake, Crotalus horridus, is the larger and more common of Wisconsin’s venomous species, typically ranging in length from 36 to 60 inches. Most at home in the steep, rugged bluffs and valleys of the southwestern and western regions of the state along the lower Wisconsin and Mississippi Riverways, these boldly colored and patterned, well known snakes are a rusty yellowish or orange, brownish yellow, pinkish-brown, grayish or grayish-brown in ground color with numerous darker brown or black chevron shaped crossbands, grading into a darker black tail and lighter colored tan rattle. Oftentimes, a narrow reddish-orange dorsal stripe is present on some snakes, and the head tends to be wide and unpatterned or unmarked except for a few small dark pinpoints. Timber rattlesnakes in Wisconsin, as well as other northern states within their range require deep rocky fissures which go well beneath the frostline in order to successfully brumate and overwinter. The historical distribution of timber rattlesnakes in Wisconsin has remained largely intact, despite significant reductions in population sizes. Elsewhere in the U.S., the timber rattlesnake widely occupies much of the eastern and southeastern U.S., where this species is occasionally also known as the “canebreake” rattlesnake, supposedly due to their propensity for being found near sugar cane fields and other agricultural areas. The timber rattlesnake was afforded conservation protection in Wisconsin in 1998, and while “threatened” status was considered for this species in the state, they only received, and continue to currently be listed as a “protected wild animal” in Wisconsin, and with no current federal status as of this article in 2018 due to political opposition to such a listing in conserving a venomous and potentially dangerous, yet also shy and reclusive animal.

The eastern massasauga, Sistrurus catenatus, is the smaller, more secretive, and at least somewhat lesser well-known rattlesnake species in Wisconsin. This smaller, heavy bodied species typically reaches only 20 to 32 inches, and is grayish to grayish brown in ground color with a series of larger, darker brown or black “bow-tie” shaped dorsal and lateral blotches. The head is relatively narrow and slender for a rattlesnake, and a series of ligher and darker ocular (or eye) stripes are present as well. Occasionally, darker to even melanistic (abundance of darker pigmentation) massasaugas are also noted in some regions. The massasauga is also perhaps the less tolerant of the two Wisconsin venomous species than the timber rattlesnake to human induced activities and changes, and has certainly been the harder hit of the species in recent decades, suffering population declines of 90% or more across the state. Also known as the “swamp rattlesnake”, its habitat is much more associated with floodplain wetlands along medium to large rivers or other larger, undisturbed wetland systems including sedge meadows, marshes, wet prairies or fens, shrub carr, and adjacent upland habitats including pine barrens, floodplain forests, prairies, old fields, and agricultural areas. In fact, the etymology of the name “massasauga” originated from the Native American term for “great river mouth”, and certainly reflects this species’ presence especially for such river confluences. In Wisconsin, massasaugas were formally very numerous over much of the southern two thirds or so of the state, with many accounts of them by travelers in some areas, although today, populations are restricted to perhaps 5 or fewer in remote western and west-central Wisconsin, as well as very small areas of perhaps south-central and southeastern Wisconsin. Also of note is the massasauga’s rattle. Although a rattlesnake species which does rattle when sufficiently disturbed, it is oftentimes less audible than that of the timber rattlesnake or other larger rattlesnakes. Early settlers to Wisconsin often likened it to that of the buzz of an insect or ticking of watches. It was noted that despite the abundance of massasaugas in early settlement, their rattle often sounded feeble and persons or livestock were seldom bitten. Currently listed as a state of Wisconsin endangered species, the eastern massasauga is also now currently listed as a federally threatened species as well, which much of its range elsewhere having declined as well, including elsewhere in the Midwest, Northeast, and into southeastern Canada.

Reproductive Concerns

As with the majority of other pit viper species, all rattlesnakes, including Wisconsin’s two venomous species, are oviparous. This means the young develop and hatch from eggs internally within the mother before being deposited in a clear, membrane consisting of egg yolk and other nutrients the neonate snakes can subsist on as their first meals. So if rattlesnakes are capable of reproducing, why are the threats they face such an issue when it comes to their reproductive viability? Can’t they just mate and then reproduce? Aren’t we being overpopulated with dangerous, venomous rattlesnakes anyway? Unfortunately, and aside from the notion of “overpopulation” being a largely subjective term, the answer to all of these negative and incorrect perceptions is not quite that simple. Typically, in most cases, rattlesnakes mate and copulate when they emerge in the spring in May and June, and gestate their internally developing young in dry, sunny, warm, and exposed locations throughout the summer, and then deposit their young in late summer or autumn of that same, or even following year. Unlike many other snakes, recent findings published indicate that at least some species of rattles do provide some maternal care for their newly deposited young for as much as 7 to 14 days or more, whereas these neonates have been observed to remain at, or near their birthing rocks or other areas where they were born. Furthermore, female rattlesnakes have been shown to be capable of retaining sperm for up to several years, and may only reproduce every two to three years or more when conditions are favorable. Indeed, neonate rattlesnakes are born with venom, and are largely capable of hunting and defending themselves shortly thereafter. However, it is largely a persistent myth that baby snakes are ironically more dangerous than adults, which is mostly not the case. It has been found that neonate snakes are able to control and monitor their venom, just as adults can. While neonate snakes may have differing venom composition than adults, the metric which should be rather considered is the volume produced and injected in that of a bite.

Depending on the age, size, and overall health and condition of the snake, anywhere from 4 to 14 neonate snakes are possible, give or take. So why are rattlesnake species in many areas having a hard time keeping up with the threats. Part of this problem lays in the fact that many rattlesnakes require a relatively long time among snakes to reach sexual maturity in order to be reproductively viable in the first place. For example, it may not take a female timber rattlesnake until its 8th to 10th year or even more to become sexually mature. Secondly, relatively small litter or brood sizes, as mentioned above, and high predation and persecution rates, are also factors. Indeed, even though they are born with venom, neonate and baby rattlesnakes, and even adult snakes, fall prey to a myriad of other animals including bird of prey, turkeys, and other large birds, a number of carnivorous to omnivorous, or scavenging mammals such as skunks, raccoons, foxes, weasels, and others, and other snake species, for example.

Habitat Loss, Fragmentation, Modification, and Development

Both species of rattlesnakes have experienced significant population declines in Wisconsin due to a number of conservation issues and threats, with habitat loss, fragmentation, modification, and development having been, and continuing to be significant factors in the declines of these snakes. Loss of available prey or food sources, overwintering sites, and/or suitable reproductive sites can all be results of these conservation concerns. Escalating, or increasing bluffland development for housing has, for example, decreased timber rattlesnake population numbers, and has increased the number of human snake encounters. Likewise, vegetative succession, which is a natural transition of plant communities from earlier, more open canopies to more closed canopies, has greatly affected the quality of the living and reproductive habitats for both species, but the massasauga especially. Historically, natural processes and factors such as occasional wildfires and burning, grazing, and flooding have helped to maintain these earlier successional plant species and more open environments, although now, human activities have greatly altered and even accelerated these factors when they are performed for other purposes not in these snakes’ conservation interest.

Fragmentation, such as the development of roads, barriers, and other infrastructures, on another hand, also causes, and continues to cause conservation concerns in that impermeability (or the snake’s inability to pass or cross the barrier road), or direct or indirect impacts, such as road mortality, often significantly impacts these snake’s populations. Habitat quality, small viable population sizes, and carrying capacity can also become issues with fragmentation as well, particularly with species which undergo seasonal reproductive movements from one area to another. In addition, other habitat modifications, such as diking, fluctuating water levels, and even other forms of wildlife management, while successful and appropriate for some species such as waterfowl, can have devastating effects on local herpetofaunal populations if poorly timed, and this certainly has been the case in several areas of Wisconsin with formally large massasauga populations. These drawdowns often have had the most severe effects on snakes while overwintering, thereby exposing snakes to sub-freezing temperatures without the afforded added protection, and also resulting in dehydration and dessication as well. Certainly, any significant loss or alteration of hibernacula, whether direct or indirect, has hit many populations especially hard in Wisconsin and elsewhere.

Human Persecution and Wisconsin’s Bounty

Perhaps the largest of the challenges historically, and even still currently faced by snakes in Wisconsin has been direct, or outright killing and persecution. Many, and numerous accounts of early travelers and settlers to Wisconsin describe the killing of hundreds or even thousands of rattlesnakes in a given period of time across many areas of the state. Unfortunately, such fear, dislike, and even hatred of these species continues even to this present day, and it has often been challenging to overcome much of the public’s long held, negative attitudes and perceptions of venomous snakes in particular. There are indeed prevalent safety concerns rather than genuine appreciation of the snake’s natural history that are likely still prevalent today behind many of the public’s interest and inquiries regarding them. Therefore, these safety concerns should not be dismissed entirely, but rather be placed into the proper perspective.

Unfortunately, another issue still widely affecting rattlesnake populations within some states and regions of the U.S. to this day are those of “rattlesnake roundups”, which are medium to large, public spectacle events involving the capture, display, handling, and slaughter of hundreds or even thousands of rattlesnakes. Snakes are often collected from the wild in inhumane and ecologically unsustainable methods such as “gassing” the snake’s dens or potential burrows, where they are then often housed and transported in inhumane or unkempt enclosures or facilities. During many of these events, snakes are also subjected to large amounts of stress, mis-handling, and ultimately inhumane slaughter and decapitation methods, and their meats, rattles, skins, and other byproducts are sold for consumption or as souvenirs. While much more can be said of these events, a positive trend occurring in at least a few such events has been their conversion to more educational and humane rattlesnake and wildlife appreciation and education events, while still maintaining the tradition of these events and revenue local residents, businesses, and even governments generate and oftentimes depend on.

While no such roundup events have occurred currently or historically in Wisconsin and much of the Midwest to the author’s knowledge, Wisconsin did have its bounty on both species prior to 1975, where as much as $3 to $5 were offered per rattle or tail collected. While the total, or exact number of snakes harvested during this time are not known, data and information on several counties and localities are known. In nearby Houston County, MN, over 4,955 snakes were collected as a result of the bounty, while about 427 were taken in Buffalo County, WI, 4, 286 in Juneau County, WI, and over 10,000 in Crawford County, WI. Fortunately, this bounty was discontinued after 1975 once it was realized by local and state governments that populations had been decimated drastically, and the bounties no longer became sustainable or profitable. Sadly, gravid, or pregnant female rattlesnakes have been, and still continue to have been perhaps hit the hardest due to their relatively sedentary nature for much of the year, and embryonic developmental requirements of open, dry, exposed areas needed for follicle growth and depositing young. Even the loss of a few developing, gravid females can oftentimes be enough to push a species over the brink in many localities.

New and Emerging Threats-Snake Fungal Disease

Certainly, much can be said about the long time conservation threats affecting rattlesnakes in Wisconsin historically over the course of decades or even centuries, but what about newer, more novel, and emerging threats? Unfortunately, there have been in the form of snake fungal disease, or SFD. And this disease does not just affect rattlesnakes, but many other non-venomous species as well that live in association with rattlesnakes including milksnakes (Lampropeltis triangulum), racers (Coluber constrictor), northern watersnakes (Nerodia sipedon) and other species. And according to Jeffrey Lorch, a microbiologist with the U.S. Geological Survey (USGS) National Wildlife Health Center in Madison WI who has conducted extensive SFD research on snakes in Wisconsin and the Midwest, as well as throughout the U.S., fungal agents are among the most devastating wildlife diseases, comparable to white nosed syndrome in bats, and chytrid disease in amphibians.  First reported in New England and Illinois in 2006 and 2008, respectively, although it is also possible that clinical signs obtained from snakes in Wisconsin and Minnesota could point to SFD having been present for more decades than believed. SFD is an emerging disease affecting wild snake populations across many states across the eastern U.S., and even more recently, globally in species of snakes widely found across Europe. Specifically, SFD is caused by the fungal agent Ophidiomyces ophiodiicola which, under the correct conditions, most commonly causes clinical signs such as scabbing or crusty scales, subcutaneous nodules, abnormal or opaque cloudiness of the eyes not associated with shedding, and localized or thickening of the skin and scales, although facial swelling, skin ulcers, and deeper nodules have also been reported. While the long term mortality of SFD has yet to be known, from what is known about this emerging wildlife disease thus far is that it does have the potential to result in devastatingly high mortality rates, especially in some areas. For example, in some areas of the northeast, population declines of imperiled timber rattlesnakes have declined as much as 50% or more in 2006 and 2007 due to this disease, and smaller, more isolated or fragmented populations may be even more vulnerable.

Unfortunately, there is still much we do not know about this emerging disease, and whether it has always long been present in the snake’s environment or whether human and environmentally induced changes have proven responsible for providing increased hospitality for the fungus in the way of wetter, more damp, or humid overwintering conditions for the snakes than what has been available historically, and whether we are unknowingly transferring or contributing to its spread to new sites as well. However, there is hope for snakes, as in recent years, as SFD has been more extensively researched, and potential treatments and remedies are explored. Many local, state, and federal agencies, researchers, and other stakeholders have been working together to help combat SFD and other emerging wildlife diseases. Fortunately, snakes might just have an edge against the fungus, which gives at least somewhat of a brighter future as they have co-evolved with the fungus to develop immune system defenses against it. According to Lorch, Snakes might have mechanisms that they would normally use to cope with that pathogen, but something is off, be it a changing habitat or changing climate, that they are just not able to deal with it as they normally would.”

Snakebites in Wisconsin

So what has the actual snakebite epidemiology, or level of occurrence and frequency, been in Wisconsin, both currently and historically? Surely an animal that is venomous and potentially dangerous to humans should be eradicated, right? Well, in actuality, while these qualities about these animals may be true and correct, rattlesnakes are also quite shy and reclusive species that occur primarily in more rugged and remote areas which are seldom traversed by most people, and are thus seldom encountered in most areas of the state. To place matters into even further perspective, the most recently available body of research as of this article published in the Journal of Wilderness & Environmental Medicine for animal related fatalities between the years 2008 and 2015 shows bee and wasp stings as the most frequently cause of death, rather than venomous snakebites. Simply put, venomous snakes are not out to chase or attack people, and furthermore their venom, which is simply highly modified enzymes and proteins, among other chemical properties, was evolved over the course of millions of years not to attack or ingest animals easily 10 times or more the snake’s size, but rather to simply give the snake an evolutionary bonus of being able to more quickly and efficiently consume and digest their smaller prey, most often smaller mammals, birds, and occasionally smaller reptiles or amphibians depending on the species. With the exception of perhaps, and even then oftentimes dubiously, a small number of only the largest species of snakes in the world found elsewhere on the globe, namely the very most largest boas and pythons, no other snakes, venomous or otherwise are simply large enough to ingest a person.

In fact, the last known and recorded rattlesnake bite fatality in Wisconsin occurred in 1900 in the state. Even despite both species’ wider range and abundance prior to 1880 in the late 1800’s, many accounts note that despite the abundance of venomous snakes in many areas of Wisconsin, people were often seldom bitten by them. Similar can also even be said of horses, cattle, and other domesticated livestock, which were also occasionally bitten by snakes, but seldom died as well. As an example, of the 70 snakebite occurrences, most of which have occurred prior to 1900, only 12 fatalities were known, and even this can be attributed to much less improved medicine and healthcare back during these times than what is available today. In fact, most of the medical practitioners of these times had little more training, knowledge, or experience than the laypersons which were bitten, and oftentimes the medical treatments of those times were even worse than the snakebite itself. Certainly, the treatments themselves for back than most often simply entailed the consumption of alcohol and whiskey, which would hardly be an effective or appropriate remedy for snakebites today.

Summary, The Future of Rattlesnakes in Wisconsin, and How You Can Help

Both of Wisconsin’s rattlesnakes are indeed some of the most well-known and recognizable animals in our Badger state, and it is relatively fortunate that both species now receive state and/or federal protections. However, this does not mean either species are out of the woods yet, and is much more still needs to be done. Unfortunately, most populations remain on the decline or are otherwise barely maintaining a minimum threshold, and still need additional help and protections. This is where an array of many different homeowners, property owners, land managers, biologists and researchers, wildlife conservationists, and other stakeholders can collaborate and all work together to help secure these widely feared and misunderstood animal’s futures in the state of Wisconsin, especially for future generations who may very well not be as fortunate to see or observe these species in Wisconsin.

Additional public education, awareness, and outreach, as well as added legal protections, citizen science initiatives, and increased enforcement are all needed to help monitor and maintain rattlesnakes in Wisconsin. Improved, or better timed environmental and wildlife management practices and policies, such as prescribed burning, diking, and others with more consideration and emphasis on local herpetofaunal individuals, their habitats and hibernaculums especially, and populations than has traditionally and historically been afforded will also greatly benefit these species in Wisconsin. We also need more widespread public support, and continued, increased cooperation and collaboration between the public and private sectors and various stakeholders to work towards accomplishing these common goals and interests. More state or region herptile specific conservation organizations and initiatives, particularly those focusing on the species of greatest conservation need in our state, such as the eastern massasauga rattlesnake (Sistrurus catenatus), western slender glass lizard (Ophisaurus attenuatus), ornate box turtle (Terrapene ornata), Blanchard’s cricket frog (Acris blanchardi), and others are also needed in Wisconsin and the Midwest. Much of the current work being done only currently falls under that of the WDNR, or Wisconsin Department of Natural Resources, and many of the past roles and efforts have become defunct or inactive over the years. A re-launch and redevelopment of Wisconsin’s and the Midwest’s Partners in Amphibian and Reptile Conservation chapters (PARC) expected this summer in 2018 will hopefully work to fulfill these needs.

Even if one does not care for snakes, it is important to still recognize their ecological roles and benefits, and even the many different legitimate scientific, medicinal, and other societal benefits they, and other reptiles and amphibians in general can provide us. Proper education and awareness, as well as maintaining a simple level of awareness of one’s actions and surroundings whenever living or working in areas where these specialized snakes still occur will go much further overall in their conservation, and being able to co-exist with them as natural neighbors while avoiding snakebites and other negative human-snake encounters.

1. Johnson, Glenn, Rich King, et. Al., Eastern Massasauga Management Working Group. The Eastern Massasauga Rattlesnake: A Handbook for Land Managers. 2000.

2. Schorger, A.W. Rattlesnakes in Early Wisconsin. 1967-1968.

3. Wisconsin Department of Natural Resources Bureau of Natural Heritage Conservation. Avoiding and Treating Rattlesnake Bites in Wisconsin. Accessed 11 March 2018.

4. Wisconsin Herp Atlas Project. University of Wisconsin-Milwaukee Field Station. Timber Rattlesnake and Eastern Massasauga Species Accounts. 15 Feb. 2007.

5. Lorch JM, Lankton J, Werner K, Falendysz EA, McCurley K, Blehert DS. 2015. Experimental infection of snakes with Ophidiomyces ophiodiicola causes pathological changes that typify snake fungal disease. mBio 6(6):e01534-15. doi:10.1128/mBio.01534-15.

6. United States Geological Service. National Wildlife Health Center. Snake Fungal Disease. Accessed 11 March 2018.

7. Loyd, Robin. Against Fungal Infections, Snakes May Have an Edge. 18 January 2018. UnDark.