The Shawnee National Forest is famous for its twice-yearly snake migration. In spring, snakes (along with other reptiles and amphibians) migrate out of the forest’s limestone bluffs and into LaRue Swamp. In the fall, the migration is reversed as the snakes come out of LaRue Swamp to spend the winter at the dry base of the limestone cliffs.
Running between the cliffs and the swamp is Snake Road, also called LaRue Road. LaRue Road runs between two very different ecosystems.
LaRue Swamp is on the west side of the road. The swamp is part of the Mississippi River basin. Here you will see species such as the cottonmouth snake, the southern leopard frog, and the bird-voiced tree frog. These animals are common in Mississippi and Louisiana, but are not usually seen as far north as Illinois. LaRue Swamp is also an important stop for migrating waterfowl, such as ducks and geese.
The LaRue-Pine Hills are on the east side of the road. The LaRue-Pine Hills are famous for their majestic bluffs towering 49 meters (160 feet) straight into the air. They form the easternmost point of the Ozark Mountain ecosystem.
The limestone rock of the bluffs is more common to Missouri and Arkansas than the rest of Illinois. More than 405 million years ago, the bluffs were at the bottom of a vast sea called the Illinois Basin. There were seashells and coral in the Illinois Basin. When the sea creatures died, they left behind skeletons made of calcium carbonate. Over millions of years, those skeletons became limestone rock.
Wind and erosion cut grooves and gullies into the soft limestone surface. These ridges and caves make an ideal habitat for snakes. They are protected from the weather, cool in the summer and warm in the winter.
To get to and from the bluffs, snakes must migrate across LaRue Road every spring and fall. If you’re a snake, crossing the road is dangerous. In the cool early morning and evening hours, the black asphalt is relatively warm, and rather than crossing quickly, snakes and other cold-blooded creatures like to hang out. That is why so many snakes, frogs, toads, and turtles get hit by cars. It is possible that up to twenty-five percent of all snakes will eventually become roadkill: According to biologist Rich Seigel, almost one in four of the snakes he collected for one of his studies had been killed by vehicular traffic. It is estimated that tens to hundreds of millions of snakes have been killed by automobiles in the United States.
In 1972, the Forest Service made the decision to close LaRue Road for three weeks in the spring and three weeks in the fall in order for the snakes to migrate safely. However, Scott Ballard, a District Heritage biologist and herpetologist with the Illinois Department of Natural Resources, found that the snake migration took a lot longer than anyone first thought. Based on information in his master’s thesis, the Forest Service extended the road closure. Now the Snake Road is closed from March 15 to May 15 in the spring and from September 1 to October 30 in the fall.
“There was a lot of resistance from the locals at first,” explained Ballard. “It used to be sport around here to see how many snakes you could run over with your car.”
As time passed, area residents changed their minds. “Most people now are supportive of the road closure,” says Chad Deaton, District Wildlife Biologist with the Mississippi Bluffs Ranger District of the Shawnee National Forest. “It helps that it doesn’t interfere with duck hunting season. Duck hunting is a very popular activity around here.”
Snake enthusiasts and herpetoculturists also support closing the Snake Road to let the snakes migrate across it. (Herpetologists study snakes and other reptiles, while herpetoculturists keep reptiles and other snakes as pets or for a hobby.)
Cars are prohibited, but people are welcome to walk the 2.6-mile Snake Road. Ballard and Deaton say walking across Snake Road isn’t like entering Indiana Jones’ Well of Souls.
“Contrary to popular belief, you won’t see a great river of snakes washing across the road,” says Ballard. “If you see twenty snakes while you’re out here, that’s a good day.”
Snakes play an important role in nature’s ecosystem and can be good for humans. “Many people’s first reaction to seeing a snake is to kill it,” says Ballard, “but a single snake can eat nine pounds—an entire pillowcase’s worth of mice—in one year. Herons and egrets also eat frogs and small snakes. Without snakes, these birds would be deprived of a food source, and we would be overrun by rodents. It’s something to think about before we run off to find a hoe or a club to end a snake’s life.”
There are three kinds of venomous snakes in the LaRue-Pine Hills: the cottonmouth, the copperhead, and the timber rattlesnake. These snakes eat small animals like fish, frogs, and mice. They will only bite people if they are provoked or disturbed.
Collecting snakes on the Snake Road is against the law. To enforce the law, Scott Ballard works as an undercover conservation law investigator.
Questions for Biologists on the Snake Road
Q: How did you become interested in snakes?
A: Scott Ballard explains, “As a kid I was very allergic to dogs and cats. My mother gave me a pet snake when I was ten. After that I was hooked.”
Q: Have you ever been bitten by a snake?
A: “Many times,” says Ballard, “but I’ve never been bitten by a venomous snake. I’ve gotten very close to snakes without meaning to and haven’t been bitten. Once I was looking for a rattlesnake species. I’d lain down, turned my head, and found one five inches from my eyes. She just looked at me and I looked at her, and I slowly got up and moved away.”
Q: What should someone do if they suddenly come upon a snake in the woods?
A: “They should stop and slowly take a step or two away from the snake,” says Chad Deaton. Scott Ballard adds, “Snakes are not mean. Snakes don’t go out of their way to bite you. They only bite people when they are surprised or feel threatened.”
Q: How many snakes are saved every year because of closing the Snake Road?
A: Ballard and Deaton say they aren’t sure, but they see fewer snakes dead on the road. That’s a good sign. It suggests more snakes are safely crossing the Snake Road every year.
Snake venom is extremely dangerous. It can also be medically useful. Some drugs developed from snake venom are used to treat disease.
Captopril comes from the jararaca (Bothrops jararaca), a viper from Brazil. Captopril works to lower blood pressure. Eptifibatide comes from the southeastern pygmy rattlesnake (Sistrurus miliarius barbouri), native to the southeastern United States. Eptifibatide prevents blood from clotting in the coronary arteries, the arteries supplying blood to the heart.
There are only about 300 species of snakes in the world that are venomous. Of that number, only about half of them are able to kill humans with their bite. There are a dozen fatal snakebites in the United States every year. Thats fewer than the number of people who are killed by bee stings or struck by lightning.
On the other side of the world (and home to deadlier snakes, such as the cobra), more than 20,000 people die from snakebites every year in India.
Are you scared of snakes? You might suffer from ophidiophobia. Ophidiophobia is a fear of snakes.
Term Part of Speech Definition Encyclopedic Entry allergic Adjective
having a consistent, unusual, negative reaction to a substance.
an animal able to live both on land and in water.
bee sting Noun
small puncture wound made by bee, wasp, or hornet.
scientist who studies living organisms.
bird-voiced treefrog Noun
frog native to wooded swamplands in the southeastern United States.
blood pressure Noun
pressure exerted by blood on the walls of arteries.
Encyclopedic Entry: bluff calcium carbonate Noun
chemical compound (CaCO3) found in most shells and many rocks.
drug used to treat high blood pressure.
underground chamber that opens to the surface. Cave entrances can be on land or in water.
steep wall of rock, earth, or ice.
Encyclopedic Entry: cliff clot Verb
to form a clump or semi-solid mass.
venomous snake native to Asia and Africa.
venomous snake native to North America.
tiny ocean animal, some of which secrete calcium carbonate to form reefs.
coronary artery Noun
vessel that supplies blood to the heart.
venomous snake native to North America.
harmful condition of a body part or organ.
chemical substance used to change the physical or mental state of an organism.
direction in which the sun appears to rise, to the right of north.
community and interactions of living and nonliving things in an area.
Encyclopedic Entry: ecosystem egret Noun
type of large wading bird (heron) with long, white feathers.
drug used to prevent blood from clotting in the coronary arteries.
act in which earth is worn away, often by water, wind, or ice.
Encyclopedic Entry: erosion fatal Adjective
ecosystem filled with trees and underbrush.
animal (amphibian) with smooth skin and long hind legs for jumping.
small ditch or ravine usually formed by running water.
environment where an organism lives throughout the year or for shorter periods of time.
Encyclopedic Entry: habitat heron Noun
long-legged wading bird.
person who keeps reptiles for pets or as a hobby.
person who studies reptiles.
study of reptiles.
Illinois Basin Noun
large depression that was formed by a sea in the Paleozoic Era (542-251 million years ago) covering parts of the U.S. states of Illinois, Indiana, and Kentucky.
Indiana Jones Noun
series of movies (named after the main character).
to meddle or prevent a process from reaching completion.
poisonous South American snake.
leopard frog Noun
frog native to North America.
sudden electrical discharge from clouds.
Encyclopedic Entry: lightning limestone Noun
type of sedimentary rock mostly made of calcium carbonate from shells and skeletons of marine organisms.
very impressive and formal.
master's thesis Noun
research that documents the author's work in a field, used to support the author's pursuit of a Master's degree in college or university.
movement of a group of people or animals from one place to another.
Mississippi River Noun
(3,734 kilometers/2,320 miles) river in the central United States.
fear of snakes.
Ozark Mountains Noun
highland region in the central U.S. states of Missouri, Arkansas, and Oklahoma.
to disallow or prevent.
to annoy or make angry.
pygmy rattlesnake Noun
small but highly venomous snake native to North America.
animal that breathes air and usually has scales.
to oppose or confront.
long, narrow elevation of earth.
path, usually paved, for vehicles to travel.
natural substance composed of solid mineral matter.
order of mammals often characterized by long teeth for gnawing and nibbling.
empty shell from an organism native to the ocean, such as a snail.
bones of a body.
reptile with scales and no limbs.
land permanently saturated with water and sometimes covered with it.
Encyclopedic Entry: swamp timber rattlesnake Noun
snake native to North America.
U.S. Forest Service Noun
part of the Department of Agriculture responsible for national forests and national grasslands.
huge and spread out.
poison fluid made in the bodies of some organisms and secreted for hunting or protection.
snake with fixed fangs that secrete venom.
birds that live near the water.
direction in which the sun appears to set.
movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.
the study of animals.