Your web browser (Safari 7) is out of date. For more security, comfort and the best experience on this site: Update your browser Ignore SNAKE MIGRATIO N On the road in Shawnee National Forest For the complete article with media resources, visit: http://www.nationalgeographic.org/news/snake-migration/ By Mary Schons Friday, January 21, 2011 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 1 of 8
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. 2 of 8
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. 3 of 8
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. Vocabulary Term 4 of 8
allergic Term having a consistent, unusual, negative reaction to a adjective substance. amphibian an animal able to live both on land and in water. bee sting small puncture wound made by bee, wasp, or hornet. biologist scientist who studies living organisms. bird-voiced frog native to wooded swamplands in the southeastern treefrog United States. blood pressure pressure exerted by blood on the walls of arteries. bluff steep cliff. calcium chemical compound (CaCO3) found in most shells and carbonate many rocks. captopril drug used to treat high blood pressure. cave underground chamber that opens to the surface. Cave entrances can be on land or in water. cliff steep wall of rock, earth, or ice. clot verb to form a clump or semi-solid mass. cobra venomous snake native to Asia and Africa. copperhead venomous snake native to North America. coral tiny ocean animal, some of which secrete calcium carbonate to form reefs. coronary artery vessel that supplies blood to the heart. cottonmouth venomous snake native to North America. disease a harmful condition of a body part or organ. drug chemical substance used to change the physical or mental state of an organism. duck aquatic bird. east direction in which the sun appears to rise, to the right of north. ecosystem community and interactions of living and nonliving things in an area. 5 of 8
Term egret type of large wading bird (heron) with long, white feathers. eptifibatide drug used to prevent blood from clotting in the coronary arteries. erosion act in which earth is worn away, often by water, wind, or ice. fatal adjectivecausing death. forest ecosystem filled with trees and underbrush. frog animal (amphibian) with smooth skin and long hind legs for jumping. gully small ditch or ravine usually formed by running water. habitat environment where an organism lives throughout the year or for shorter periods of time. heron long-legged wading bird. herpetoculturist person who keeps reptiles for pets or as a hobby. herpetologist person who studies reptiles. herpetology study of reptiles. ideal adjectiveperfect. Illinois Basin 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 series of movies (named after the main character). interfere verb to meddle or prevent a process from reaching completion. jararaca poisonous South American snake. leopard frog frog native to North America. lightning sudden electrical discharge from clouds. 6 of 8
Term limestone type of sedimentary rock mostly made of calcium carbonate from shells and skeletons of marine organisms. majestic adjectivevery impressive and formal. research that documents the author's work in a field, master's thesis used to support the author's pursuit of a Master's degree in college or university. migration movement of a group of people or animals from one place to another. Mississippi (3,734 kilometers/2,320 miles) river in the central River United States. ophidiophobia fear of snakes. Ozark highland region in the central U.S. states of Missouri, Mountains Arkansas, and Oklahoma. prohibit verb to disallow or prevent. provoke verb to annoy or make angry. pygmy small but highly venomous snake native to North rattlesnake America. reptile animal that breathes air and usually has scales. resist verb to oppose or confront. ridge long, narrow elevation of earth. road path, usually paved, for vehicles to travel. rock natural substance composed of solid mineral matter. rodent order of mammals often characterized by long teeth for gnawing and nibbling. seashell empty shell from an organism native to the ocean, such as a snail. skeleton bones of a body. snake reptile with scales and no limbs. 7 of 8
Term swamp land permanently saturated with water and sometimes covered with it. timber rattlesnake snake native to North America. U.S. Forest part of the Department of Agriculture responsible for Service national forests and national grasslands. vast adjectivehuge and spread out. venom poison fluid made in the bodies of some organisms and secreted for hunting or protection. viper snake with fixed fangs that secrete venom. waterfowl birds that live near the water. west direction in which the sun appears to set. wind movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun. zoology the study of animals. Websites Shawnee National Forest: Snake Migration in LaRue-Pine Hills National Park Service: What Does It Take to be a Park Ranger? Bureau of Labor Statistics: Biological Sciences 1996 2017 National Geographic Society. All rights reserved. 8 of 8