Discover the Deadliest Animals in Illinois

Written by Cindy Rasmussen
Published: October 2, 2022
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According to the Illinois Department of Natural Resources, “Snakes inhabit Illinois, dwelling in forests, grasslands, marshes, swamps, ponds, lakes, streams, rivers and sloughs.” The only place it doesn’t mention is snakes on a plane! (There actually was an incident with a snake on a plane heading for O’Hare International Airport in Chicago, back in 1985. What looked like a snake tail was spotted in an overhead bin and when the flight attendant opened the compartment an 18-inch northern water snake fell into the lap of an unsuspecting passenger! The 16-year-old boy sitting next to her grabbed the snake and admitted that he had smuggled it onto the plane. It was turned over to authorities when they landed in Chicago.).

So, it may appear that there is no where in Illinois you can avoid the dangers of snakes, but in reality, how dangerous are snakes? Are there other animals in Illinois that are dangerous or deadly even? With 12.67 million people in the state there must be some unique animal attack stories, like an incident with a “kamikaze squirrel”! Let’s discover the deadliest animals in Illinois.

Are Snakes the Most Dangerous Animals in Illinois?

Deadliest animals in Illinois - coppherheads are just one of the venomous snakes in the state

Copperheads are just one of the venomous snakes in Illinois

©Creeping Things/

There are forty different species of snakes in Illinois but only four of them are venomous. All four are what we call “pit vipers” and have a pit on either side of their heads which is used to help them sense warm-blooded prey. Pit vipers also have fangs that house the venom that can disable their prey allowing them to swallow their prey whole. They certainly do not prey on humans, but if provoked or handled they certainly will bite in defense. The four native venomous snakes in Illinois are:

  • Eastern copperhead: These snakes get their name from the copper-colored head and are located in the southern third of the state. If you are hiking in the fall in snake territory you may spot a group of these snakes that sometimes travel together when they are headed for their hibernation sites.
  • Northern cottonmouth: These snakes are semiaquatic and can live in swampy areas. In Illinois they are only in the southern-most tip of the state. There is nothing notable about their body’s coloration, they are mostly all brown or black with some having a faded pattern, but they get their name from the white interior of their mouths. Hopefully you are never close enough to encounter an angry, mouth-opened cottonmouth.
  • Timber rattlesnake: The timber rattlesnake is a threatened species in Illinois “due to habitat loss and indiscriminate killing” according to the Illinois Department of Natural Resources. They can be found along the western border of the state along the Mississippi and at the southern tip of the state. These snakes are light brown with black bands and a rust-colored stripe down the back.
  • Eastern massasauga: So far all of the venomous snakes have lived in the southern portion of the state or along the Mississippi, thinking the northern part of the state would be free from venomous snakes, but then there is the eastern massasauga. These snakes live in the northern two-thirds of the state. However, encountering one is rare due to the fact that these snakes are listed as endangered due to habitat loss. They live in marshes and swamps and the more people drain these areas to create more buildable land, the more habitat that is loss. These snakes are the smallest of the venomous snakes in Illinois, around 18-30 inches. They are gray with dark brown splotches on their back and smaller splotches on their sides.

Coyotes vs. Wolves vs. Dogs: which are more Dangerous?

Deadliest animals in Illinois - dogs are most dangeorus that coyotes and wolves

Dogs are more dangerous to humans in Illinois than coyotes and wolves

©KruBeer Photo/

Coyotes, wolves and of course dogs all live in Illinois. Wolves are the largest of the three and can grow to be 5 to 6 feet long and weigh up to 120lbs. However, there has never been a wolf attack in Illinois and only 2 fatal wolf attacks in North America in the last 100 years, so very rare. Coyotes are much smaller than wolves growing to be 2 to 4 feet long and weighing 20 to 50lbs. The Chicago Animal Care and Control reports that it receives 450 service requests a year involving coyotes. However, there has never been a human attacked by a coyote in the past 30 years. Pets have been attacked, cats and small dogs, so it is important to keep your pets in a fenced area or on a leash and report any coyote sightings.

Although dogs have been killed by coyotes, dogs are more dangerous to humans than most animals. Unfortunately, 30 to 50 Americans die each year due to dog attacks, many of which are small children. A one-year-old girl from Springfield, Illinois was killed in March 2021 by the family dog when she got too close to the dog’s food and the dog bit her causing a fatal injury. In December 2021, there was a report of a recent case of a man being killed by his own dogs in his home in Roseland which is the far south side of Chicago. is a national organization which is trying to increase education on preventing dog bites and attacks in the future.

What about Lake Michigan?

Way back in 1955 there was a story of a boy being attacked by a bull shark in Lake Michigan. However there is no proof of this and this is now just an urban legend. Bull sharks can live in fresh water but they could not make their way all the way up the Mississippi River to Lake Michigan. So, besides the riptides, swimming in the Lake should not be dangerous.

Are “Kamikaze Squirrels” the most Dangerous Animals in Illinois?

Eastern Gray Squirrel

Squirrels have a habit of chewing through trash cans

© Davies

If Mother Nature had a blog she would definitely have posted this story, maybe as a warning. The Chicago Tribune reported that alderman Howard Brookins Jr had voiced his concern about squirrels in the city at a recent council meeting. He was upset that “aggressive squirrels” had been chewing through trash cans and causing damage. A few weeks later the Tribune reported Brookins was out for a bike ride when he “was jumped by a kamikaze squirrel that leapt into the front wheel of his bike and lodged himself in the spokes”. Doesn’t sound like this is going to end well.

Although this sounds like a funny story, and alderman Brookins was able to see the irony in the incident (updating his Facebook pic to that of his bike with the squirrel in the spokes) it ended with Brookins in the hospital with significant injuries from flying over the handlebars of his bike. And the squirrel…well, he didn’t make it, perhaps getting revenge for his fellow squirrel community. As humans and wildlife try to coexist there is bound to be some conflicts but hopefully, we are getting better at getting along.

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The photo featured at the top of this post is © DnDavis/

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About the Author

I'm a Wildlife Conservation Author and Journalist, raising awareness about conservation by teaching others about the amazing animals we share the planet with. I graduated from the University of Minnesota-Morris with a degree in Elementary Education and I am a former teacher. When I am not writing I love going to my kids' soccer games, watching movies, taking on DIY projects and running with our giant Labradoodle "Tango".

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