Snakes – Discover-Nature

Venomous Snakes Of Illinois

There are 40 snake species native to Illinois, and they are found in all types of habitat from woodlands and prairies to wetlands and urban areas. Of these, four species are venomous. A venomous snake is one that uses a chemical toxin to kill its prey. This internally developed chemical is delivered through a pair of hollow fangs in the upper jaw of the mouth. When the snake opens its mouth, the fangs drop down and venom is injected into the prey as the snake bites. The snake will then release the prey, waiting for the venom to kill it before swallowing the prey whole. Juveniles will inject less venom, but with the same potency as adults.

^{Pit viper Fang and Jaw Structure drawn by M Moran at Encyclopedia Britannica}

Venomous snakes in Illinois are all pit vipers, a sub-family of the Viperidae family of snakes. The pit, a large opening between the eye and the nostril, just above the upper lip, can detect heat given off by warm-blooded prey species. Their elliptically-shaped eyes is another characteristic that helps to identify venomous snakes.

^{Close-up of elliptical eye on Copperhead by Mark Dumont, Jun 2011}

^{Close-up of pit above upper lip on pit vipers, by Scott Ballard, IDNR}

Illinois venomous snakes are non-aggressive in nature, but will bite if cornered, harassed, or stepped on. Bites are usually not fatal in humans, but they can be quite painful, often resulting in swelling and possible infection. Vomiting, nausea, and tissue or nerve damage may also result. Anyone that is bitten should seek immediate medical attention.

^{Eastern Copperhead, Agkistrodon contortrix, by Peter Paplanus, Aug 2018}

^{Eastern Copperhead close-up, Agkistrodon contortrix, by Peter Paplanus, Apr 2021}

The Eastern Copperhead, Agkistrodon contortrix, lives in the southern third of Illinois on wooded hillsides, river bluffs with sandstone or limestone outcroppings, and along forest edges. During the hot summer months, they may also feed on the abundant rodent populations in meadows or near abandoned buildings. The copperhead is about four feet in length and has a light brown back with one to two dozen reddish-brown colored hourglass-shaped markings along the back. The top of their head is a brighter red-brown.

^{Northern Cottonmouth, Agkistrodon piscivorus, by Virginia State Park Service, May 2016}

^{Northern Cottonmouth flashing white, Agkistrodon piscivorus, by Peter Paplanus, Aug 2022}

The Northern Cottonmouth, Agkistrodon piscivorus, resides in far southern parts of Illinois, living in swamps, sloughs, and oxbow lakes. At five feet in length, this heavy-bodied snake is a uniform charcoal or dark olive color, with dark crossbands and a tan to gray belly. When disturbed, its response is to face its attacker and open its mouth widely, displaying the bright white interior, earning the name of cottonmouth.

^{Timber rattlesnake close-up, Crotalus horridus, by Peter Paplanus, Apr 2023}

^{Timber rattlesnake, Crotalus horridus, by Peter Paplanus, Apr 2023}

Timber rattlesnakes, Crotalus horridus, live in both southern and northern areas along the Mississippi River and Illinois River valleys. Usually found in heavy timber with rock outcrops or bluffs, this snake, up to six feet long, is marked by two dozen black crossbars down a gray-green-yellow back. Its belly is light-colored with dark edges, and it shows a dark strip behind each eye. Timber rattlesnakes will hunt in any areas where there is a large rodent population. They are listed as threatened since we have seen sharp declines in the populations in recent years.

^{Massasauga Rattlesnake, Sistrurus catenatus, by Peter Paplanus, Apr 2021}

^{Massasauga Rattlesnake close-up, Sistrurus catenatus, by Peter Paplanus, Apr 2021}

The Massasauga Rattlesnake, Sistrurus catenatus, is found in small numbers scattered across the state, mainly in prairie wetlands and river floodplains. Listed as endangered in the United States, it has become quite rare in Illinois with only a couple sightings annually for the past several years. Massasaugas are about two feet in length, with a gray to light brown back and 30-40 dark, bow-tie shaped markings. Four to seven darker rings cover the tail. Their main prey is small rodents.

Venomous snakes have small ranges, staying close to home for hunting and mating. Their main predators include humans, birds of prey, and other snakes. Many have been killed by people with an unfounded fear of these creatures. Although they play a major role in controlling rodent populations, there has been little concern shown over loss of habitat due to draining of wetlands and other urban development. Plan a visit to the Jurica-Suchy Nature Museum or a nature center near you to learn more about these mysterious, yet wonderous species.

Snake Defense

Snakes, with over 3,000 species worldwide, are one of the largest groups of reptiles. They are found on every continent except Antarctica and live in every type of habitat including freshwater and saltwater. They have numerous enemies and have developed defensive strategies enabling them to survive and prosper.

^{Catching a snake on the wing by CuriousLog, Jun 2007}

^{Red-shouldered hawk with snake by Don Loarie, Mar 2018}

^{Great Blue Heron eating snake by C Watts, Jan 202}2

Snakes must deal with threats from a wide range of animals. Bird species that prey on snakes include raptors, ravens, egrets , and storks. Nocturnal hunters, including owls, have excellent sight in low-light conditions and often hunt by spotting movement among foliage. Likewise, during daytime hours, red-tailed hawks and eagles can spot movement on the ground while soaring. Snakes are normally line-of-sight hunters, and are often unaware of threats from above, giving avian predators a distinct advantage.

_{^{American crocodile, Crocodylus acutus by Florida Fish and Wildlife, Feb 2021; Wolverine by Maia C, Aug 2012; Skunk by D Fletcher, May 2016}}

Most mammal predators are larger, more agile, and faster. Badger, wolverine, and racoon are all excellent climbers and may hunt from an elevated perch. Wolverine and skunk are also burrowers that will dig out their prey from underground. Snakes living in saltwater and freshwater environments are eaten by predators such as crocodiles and snapping turtles. In addition, some larger snake species regularly hunt smaller snakes.

^{Copperhead on dead leaves by Abbott Handerson Thayer, Mar 2022}

Snakes use a number of non-aggressive strategies to avoid confrontation and escape. Their best defense is to remain hidden, using colors and patterns to break up the outline of their body, allowing the snake to blend with the background foliage and be overlooked by any predators. Another passive strategy is balling, involving compressing their body into a tight coil or ball, typically with the head tucked in to protect this most vulnerable area. Playing dead is often an effective means to escape predation, honed to perfection by the Western hognose snake. This snake convulses its body, rolls onto its back, and lets its tongue loll out of its mouth. It may vomit or spew blood, release fecal matter or musk, all in its attempt to convince a potential predator that it is already dead and no longer appetizing.

^{Timber rattlesnake balled and hidden by Peter Paplanus, Apr 2022}

Mimicry is a development that has taken place in some species over long periods of time. Batesian mimicry is when a harmless species has evolved the coloration of a more dangerous species to fool a predator into leaving it alone. Scarlet kingsnakes of the southeastern United States are quite harmless but look very much like Eastern coral snakes, a venomous species in that same area. Auditory mimicry involves creating sounds used by more dangerous snakes. Fox snakes, found in deciduous forests, often vibrate their tails in leaf litter, making a buzzing noise very similar to the sounds made by rattlesnakes living in the same area.

^{Scarlet kingsnake by FWC Fish & Wildlife Research Institute, May 2015}

^{Eastern coral snake by FWC Fish & Wildlife Research Institute, Sep 2014}

Snakes often use one or more methods of intimidation. Bright display colors are found among many venomous species and serve as a warning to potential predators that this snake is dangerous. Another form of intimidation involves a snake inflating its body or a body part to make it look bigger. The puff adder inflates its whole body by filling its lung with air. Cobras hold their heads high and flare out an extra fold of skin on either side of their heads, commonly called “hooding.” Intimidation may also involve auditory cues including the rattling of a snake’s tail and the hiss emitted by cobras as they bring up their heads.

When the above strategies do not allow the snake to escape, most species will not hesitate to strike. Several species do not bite, striking with the nose or an open mouth; however, all venomous snakes will bite in self-defense, although they may not inject venom. A few species are able to spit venom, used purely as an act of self-defense, although if the venom targets an eye or nasal passage, the results can be extremely painful.

Snakes are some of the most interesting species with a lifestyle very different from our own. They have many strategies for keeping themselves safe from wild predators, and will be around for us to observe, learn about, and be fascinated by.

Snake Monitoring

Some days I spend hours grabbing snakes! As a snake monitor, I am one of several stewards in this area leading groups that monitor snakes. Our goals are to learn what species live here, their population size, and what areas they inhabit. We are using this data, as well as other related information, to assist in making habitat management decisions.

Wildlife monitoring activities for any species are designed based on prior knowledge of when and where a species may be found and what kinds of activities we might observe. For snakes, we identify possible sites based on several factors: being away from human activities, having access to food, water, and shelter for overnight and bad weather. We set out numerous snake boards. A snake board is a piece of rubber, wood or metal approximately two square feet in size and heavy enough that it will not be moved by wind or animals. A line of these are laid out in the observation area, about one every 8-10 yards. I use three boards at each of my dozen or so sites, but there can be 1 to many used.

*Storeria dekayi*, Midland Brown Snake by Janice Sommer, 2018

Snakes are ectotherms, meaning they must obtain heat from their surroundings. Snakes require heat to perform any action including moving, hunting and digestion. Snake boards are generally placed in sunny areas. This creates a spot where a snake can spend a few safe and sheltered hours absorbing heat that will allow them to hunt, eat and digest a meal. When they are warm enough, they will leave the board area, complete their hunting or other movements. They usually spend the night under rocks or logs in a close-by and safe place and return again the next day.

Monitors usually work in pairs. When we visit a site, we will record date, time, and weather conditions. One monitor lifts the board and both monitors capture any snakes that are present, placing them into a soft, cloth bag. As each snake is removed from the bag, we record the species, weight, length and any identifying marks.

Several pictures are taken of each one, and then they are released. They usually disappear quickly into the underbrush, but may not go far and may return to the board after we are gone. Observations are made at least weekly, and are varied by time of day or weather conditions in order to have data across a wide spectrum of factors.

We have a wide variety of questions, and we are always adding more to the list. Identifying what data to collect to provide answers, helps determine and refine our procedures. Questions range from statistical to curious such as what snakes do we find in DuPage County, where do they live, what do they eat, can they swim, what restoration activities affect them and how, what management practices need to take them into consideration. Collected data is used by scientists, teachers and stewards as we learn more about our own environment and how to manage its health.

Garter Snakes

At this time of year, as soon as the daytime temperatures start to reach into the forties and above, we begin to see snakes coming out of their winter dens. Two common snakes in DuPage County are both garter snakes, from the genus Thamnophis which includes 30 species worldwide.

The Eastern Garter Snake, Thamnophis sirtalis and the Plains Garter Snake, Thamnophis radix spend the winter in underground dens containing several dozen to several hundreds of individuals. Winter is a period of dormancy where these snakes enter brumation, an extreme slowing down of their metabolism.

Eastern Garter Snake, *Thamnophis sirtalis*, by DonArnold

A garter can be up to 30″ long, black/brown backs, yellow stripes on their sides and a gray-green belly. Usually found in meadows, light forests, marshes and vacant lots, they enjoy a warm spot such as open rocky/paved surfaces warmed by sunlight or hanging out in bushes or logs in the sun. Their meals include insects, earthworms, slugs and fish. Nights are spent under logs, rocks or leaf litter protected from wind and rain.

There are a variety of methods used to study snake species, one of which involves using cover boards. Boards are approximately two square feet, made of plywood, aluminum siding or heavy rubber. These are placed in likely spots where snakes will be found. The snakes use the boards during the day for shelter, rest and warmth. When snakes are found under the boards we identify each snake, weigh and measure it, take lots of pictures and note any markings or injuries. We also record location, weather, time of day and any activity observed. Finding a variety of individuals helps to establish population numbers; finding the same individuals more than once helps to identify whether snakes are moving to different locales during the year.