The Shawnee National Forest snake migration
Although the words “snake migration” may sound terrifying to some, the Shawnee National Forest snake migration is one of the coolest biological events that happen in the country. During this period of time, thousands of snakes migrate across a single stretch of road in order to find safety on the other side. Due to the protected nature of many of the snakes, the road, now dubbed Snake Road, began closing each year in order to reduce accidental vehicle incidents. This migration happens twice a year, once between March 15 and May 15th, and again from September 1st to October 30th. When the migration is in swing, Snake Road closes, making it one of the most unique events in the world. In fact, Snake Road is the only road closed every year for the migration of snakes and other reptiles.
Is it normal for snakes to migrate?
Snakes don’t migrate hundreds of miles like birds – but they do, indeed, migrate to reach dens for overwintering. Cold blooded snakes are dependent on external sources of heat – so they can’t survive cold weather unless they find a safe space to hibernate until Spring. If you’ve seen a snake crossing the road in Spring or Fall – they are most likely migrating. Seldom do you find a situation perfect for a mass snake migration like the amazing Snake Road event.
Why do the snakes migrate across this specific road each year?
What makes Snake Road so special isn’t the road itself, but what it bisects. Snake Road is between two important geological regions, the LaRue Pine Hills and the LaRue Swamp. The LaRue Pine Hills are home to large, towering limestone bluffs that make up the easternmost point of the Ozark Mountain chain. These limestone structures have deep crevasses and holes that make the perfect wintering ground for snakes during the colder seasons. On the other side of the road is the LaRue Swamp. LaRue Swamp is one of the largest swamps in the region and the preferred location for many of the state’s most important snakes and reptiles. When winter months are near, the snakes and reptiles cross the road in order to reach the limestone caverns, and when it warms up they head back to the swamps!
Why is the road closed each year?
In 1972, research into the region showed that thousands of reptiles were dying while trying to navigate the road. In fact, some research shows that up to 25% of all snakes will be killed by cars in the United States. The data showed that closing the road for a few weeks would ensure the safe passage of millions of reptiles during the migration. Later data gathered by Scott Ballard, a District Heritage biologist, would show that the 3-week gap wasn’t quite long enough for the reptiles to cross. Using his data, he was able to have the road closure extended for a few extra weeks, thereby increasing the number of snakes that could successfully make the journey. 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. Incredibly, there was some pushback from the locals when the closures went into place. Here’s why:
The most common venomous snakes to cross the road each year
There are three types of venomous snakes that live in the region:
copperheadscottonmouthstimber rattlesnakes
Copperheads
Copperheads are generally recognized as the most common venomous snakes wherever they can be found, although they are the least dangerous of them all. Thankfully that’s the case because they are also the snake that most often bites humans! Their camouflage and motionless defense mechanism often work too well, as humans will either step on them or reach near them only to find they have been bitten. Copperhead bites are rarely, if ever, fatal nowadays.
Cottonmouths
Cottonmouths are aquatic snakes that get their names from their bright white mouths. When threatened, they will curl up and flash their mouth, hoping to scare predators away. Most of the time, it works! In some situations, however, humans will accidentally step on them or try and handle these venomous creatures and are bitten. Cottonmouths are more venomous than copperheads but still aren’t very deadly.
Timber Rattlesnakes
The most venomous snakes in the region are timber rattlesnakes. Timber rattlesnakes are related to the copperhead and cottonmouth (they are all pit vipers), but they are by far the most venomous of the three. Thankfully, these snakes do their best to avoid humans and even give an audible warning with their rattles when they feel threatened (courtesy of their rattles). Timber rattlesnakes aren’t all that common as they only breed every three years and produce a litter of 10 snakes, of which only 5 will make it to adulthood.
Nonvenomous Snakes
There are many types of nonvenomous snakes in Illinois, especially in the LaRue region. The most common include:
earth snakesrough green snakesgarter snakeswater snakes (multiple species)
Although these snakes are quite numerous, they play an important role in the ecosystems. In fact, snakes eat millions of pounds of mice and rats each year, keeping humans from being overrun by pests that often carry diseases.
