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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

© Josh Kapfer
Bullsnakes are the largest snake species native to the upper Midwest.
© Josh Kapfer

April 2007

More bluff than bite

They huff and hiss, but these bullish snakes are harmless and a rare find. Help us locate where bullsnakes range and roam in Wisconsin.

Josh Kapfer


Hints for sighting bullsnakes
Reporting your findings

The grass blades bent and I saw it: a snake. Not a little one, either. Its body was coiled, but I could tell it had to be close to four or five feet long. I was stooped over collecting prairie seeds about two feet away. Seeing a snake that big in the wild gets your blood moving, and I stared wide-eyed and motionless at the serpent for several seconds. Although startling at first, I realized that given my current vulnerable position, it could have harmed me already had it wanted to do so.

My pulse slowed, but a lingering uneasiness remained. What usually jolts me back to reality from the mindless cadence of stripping prairie seed and putting it in a bucket is the chance sighting of some pretty tame stuff – a pasqueflower, a gleaming white antler shed, or a turkey feather – not a BIG snake, ceaselessly flicking its forked tongue and watching me with unblinking eyes. Much to my surprise, it didn't seem startled by me at all and simply sat motionless, half covered by dormant grass.

I should have known better. A warm spring afternoon on a Wisconsin prairie can bring numerous delights: the year's first bird's-foot violet, the call of a western meadowlark, a sand scrape peppered with fresh coyote tracks...and reptiles. Those who traverse prairies and savannas for work or pleasure occasionally see several of Wisconsin's rare reptile species like ornate box turtles (Terrapene ornata), slender glass lizards (Ophisaurus attenuatus), prairie racerunners (Aspidoscelis sexlineata viridis), or bullsnakes.

Bullsnakes (Pituophis catenifer sayi) are the largest snake species native to the upper Midwest, and reportedly can exceed 74 inches (190 cm) in length. Their variable colors include mixed patterns of brown, black, yellow, beige and white. Their heads are heavily patterned with dark bars on the scales around the mouth, and a pointed "snout" or rostral scale. The middle third of their bodies is adorned with dark brown or black saddle-shaped blotches that are large and distinct on the back, but are smaller and less defined along the sides. The back third of their bodies, including the tail is marked with alternating black or dark brown rings on a yellow or beige background. When approached or cornered, bullsnakes are known to "huff" or "hiss" to ward off a potential threat. These sounds may be heard from some distance, and bullsnakes may have earned their common name from this bullish behavior.

Bullsnakes are non-venomous constrictors that prey mostly on small mammals. For this reason, they are believed to be incredibly efficient at controlling rodent populations, particularly in agricultural settings. In his 1981 book, The Natural History of the Amphibians and Reptiles of Wisconsin, Richard Vogt estimated that a single bullsnake consuming one rat every two weeks during the snake's active period from April to October in Wisconsin would save a farmer approximately $400 annually (in 1981 prices) in losses to damaged crops and livestock feed. Thus, the bullsnake, like other snakes that consume rodents, is an important member of the agricultural community.

Herpetologist Josh Kapfer leads the effort to document bullsnake sightings. © Josh Kapfer
Herpetologist Josh Kapfer leads the effort to document bullsnake sightings.
© Josh Kapfer

Bullsnakes purportedly prefer short grass or sand prairies, and savannas (slightly wooded grasslands with fewer than 12 trees per acre). Such areas have declined so substantially that bullsnakes, and many other grassland species, have fewer places in the upper Midwest to forage, nest and overwinter. Consequently bullsnake populations have declined significantly over the past several decades and stable populations have been documented at only one or two sites in Wisconsin. Due to its rarity in the upper Midwest, bullsnakes are listed as a protected wild animal by the Wisconsin Department of Natural Resources. The listing means it is illegal to take, possess or kill this snake.

Little is known about the bullsnake's true status throughout much of its potential range in Wisconsin. Despite its size, it is an elusive creature and few sightings are reported annually. Often these reports are anecdotal and difficult to substantiate. Therefore, state herpetologists have designed a more formal method for documenting where this species occurs in Wisconsin. Such information will be crucial to future conservation of this species.

Hints for sighting bullsnakes

You are more likely to see bullsnakes in April through May and again in September through October when temperatures are lower and the snakes are sunning themselves. Though bullsnakes have been reported in many regions of Wisconsin, experience suggests they are more common in the southern, south central, southwestern and western portions of the state. Bullsnakes are primarily found in open canopy upland habitats with dry, sandy soils such as prairies, oak savannas, pastures and meadows, particularly if those areas are next to open south-facing bluffs. People who spend a lot of time outdoors, like property managers, foresters, farmers and hunters, are more likely to encounter these snakes.

Bullsnakes can easily be mistaken for eastern milksnakes (Lampropeltis triangulum triangulum) or western fox snakes (Elaphe vulpina) to the untrained eye. Neither of these snakes is venomous, but inexperienced observers will still want to exercise a little caution before getting too close to snakes that have not been positively identified. Bullsnakes, like several other snake species, are rattlesnake mimics that shake their tails when disturbed. When the moving tail tip contacts any dry object, it makes a sound that may be mistaken for a rattlesnake rattling. Should you encounter a snake exhibiting such behavior, don't panic. Keep a little distance between you and the snake. Get out your field guide, and get a look at the snake's coloration and markings from about five feet away.

Reporting your findings

Bullsnake observations can be reported electronically and sent directly to the DNR's endangered resources program. The data from these accounts will be used to estimate the bullsnake's status and distribution in Wisconsin. Reported sightings will also help wildlife biologists and property managers make sound conservation decisions about preserving the snake's preferred habitats.

The reporting form asks observers to provide the county, township, range and section of each sighting. GPS coordinates and the names of nearest roads are especially helpful, if they can be determined. Also include your name, phone number and email address so state herpetologists can contact you for further information about the sighting. Recording the date, time of day, weather and temperature for each sighting is important as well.

Since bullsnakes might be confused with other snake species, photographs of the snake should also accompany each observation. It is important to note that bullsnakes are occasionally found in similar habitats as timber rattlesnakes (Crotalus horridus), and observers should exercise caution when approaching a snake that they cannot identify. In such instances, photos should be taken no closer than four to five feet from the snake.

Take a photo to help identify snakes you encounter in the field. © Josh Kapfer
Take a photo to help identify snakes you encounter in the field.

© Josh Kapfer

These photos will help identify the species, so please try to get photos showing the front, middle and back of the snake in daylight to verify the animal's natural colors. Protected animals, like these snakes, cannot be collected for future identification.

To help you distinguish snake species, consider taking along a copy of the booklet "Snakes of Wisconsin," by Rebecca Christoffel, Robert Hay and Lisa Ramirez (Publication PUB-ER-100-00) available for $3.00 from the DNR's Bureau of Endangered Resources. It contains color pictures, descriptions, known ranges and a key to identifying Wisconsin's 21 types of snakes.

Sightings and digital photos of bullsnakes seen in Wisconsin can be submitted by mail or electronically to the Wisconsin Department of Natural Resources. Learn more about the bullsnake and how it differs from similar snake species in Wisconsin.

See details about the Bullsnake Sighting Initiative and the observation form. Printable versions of bullsnake information pamphlets and posters can also be downloaded from this page. You can pick up paper copies of the bullsnake sighting forms from area nature centers or by writing the Bureau of Endangered Resources. Mailed reports should be sent to: Bullsnake Sighting Initiative, DNR Bureau of Endangered Resources, P.O. Box 7921, Madison, WI 53707.

Back in the field, I rested my prairie seed bucket between me and the snake. Slowly, I stood up and took a step forward to get a better look at him. He really was quite a stunning critter: all shiny scales of brown, yellow and black. Thick, muscular body pressed against the sand, soaking up all the heat that the sun would yield on this mild April afternoon. My step, however, must have disturbed him. For the first time, he moved, lifted his head, turned away from me and, with surprising gracefulness, quietly slithered off to disappear down a nearby gopher hole.

Josh Kapfer is a herpetologist with DNR's Bureau of Endangered Resources and recently completed doctoral research at the University of Wisconsin-Milwaukee on bullsnake ecology. He will coordinate fieldwork, reporting and subsequent research on bullsnake distribution in the state.