Eastern Indigo Snake

The eastern indigo snake (Drymarchon couperi ) is a large nonvenomous snake of the Colubridae family. Despite once occurring widely in the coastal plain of the southeastern United States from Georgia to Mississippi, as of the early twenty-first century eastern indigo snake populations are typically only found in southeastern Georgia and peninsular Florida. Recent and ongoing reintroduction efforts are attempting to re-establish the species in southern Alabama and the Florida panhandle, however. In Alabama, the snake was historically reported in southern pine plains and hills in Mobile, Baldwin, and Covington Counties but prior to the reintroduction effort had not been documented in the state since 1954. The common name of this species is derived from its large glossy scales, which take on the blackish-purple color indigo in bright light. The genus Drymarchonalso includes the Texas indigo snake as well as several Central American species and one possible species reported in Venezuela.

The eastern indigo snake was first described in 1842 by pioneering nineteenth-century naturalist and herpetologist John Edwards Holbrook, author of North American Herpetology; or, A Description of the Reptiles Inhabiting the United States. Holbrook's taxonomy was based on a specimen captured live and brought to him by Georgia planter James Hamilton Couper. Holbrook gave the species the scientific name Drymarchon couperi from the Greek "drymarchon" (roughly meaning "lord of the forest" for the snake's impressive size and girth) and "couperi" to honor the man who brought him a live specimen.

The indigo snake is one of the longest native North American snakes and the second heaviest, with a thick body that can reach up 6 to 7 feet in length (2.13 to 2.45 meters). Exceptionally large individuals are possible; the largest indigo snake recorded was 9.2 feet (2.8 meters) long, and the heaviest was more than 10 pounds (4.5 kilograms). Mature individuals are typically a uniform glossy blue-black, although some specimens exhibit reddish orange or cream coloration on the throat, cheeks, and chin. Smaller indigo snakes are easily mistaken for the common black racer, but the black racer is slender and quick and the indigo snake is stouter and slower-moving.

In Alabama, as in Georgia and the Florida Panhandle, the eastern indigo snake has historically preferred raised sandy ridges in proximity to stands of longeaf pines and scrub oaks. In these areas, it shares this habitat with the gopher tortoise (Gopherus polyphemus), which digs extensive burrows in the loose soil that are shared by indigo snakes seeking refuge from extreme cold and heat. The snakes also have been known to take shelter in hollow logs and the burrows of rodents, armadillos, and even land crabs. Female indigo snakes use the burrows of tortoises and other animals for breeding and laying eggs, which typically occurs between October and February. After mating, females will lay one clutch of eggs, averaging nine eggs per clutch, that begin hatching 90 to 100 days later.

Like all snakes, indigo snakes are carnivorous, and this species eats a wide variety of prey, including lizards, frogs, small birds, small mammals, and other snakes. They are known to regularly prey upon copperheads, cottonmouths, and rattlesnakes and are generally considered to be at least resistant to their venom. Unlike many non-venomous snakes, the eastern indigo snake is not a constrictor. Instead, it generally either kills with the power of its jaws or begins to swallow prey alive.

When approached, a wild indigo snake will attempt to escape, albeit at a much slower speed than a rat snake or racer, and if it feels unable to do so, it will attempt to warn off a threat by hissing, flattening its neck to make its head appear larger, and vibrating its tail, an action which in dry leaves can produce a noise like that of a rattlesnake. When grasped and picked up, the indigo snake typically becomes calm after a few minutes of handling and rarely bites. Their demeanor, along with their spectacular size and appearance, makes them attractive as pets and is one of the reasons that they are endangered in the wild. The eastern indigo snake is listed as federally threatened under the Endangered Species Act and is protected. The greatest threats to these snakes are loss of habitat, the illegal practice of pouring gasoline down burrows by rattlesnake hunters, and the pet trade.

In the 1980s, the Alabama Cooperative Wildlife Research Unit at Auburn University attempted to reintroduce the indigo snake, with releases in Autauga, Baldwin, Bullock, Covington, Escambia, Mobile and Washington Counties. Some of these snakes were later temporarily recaptured. Starting in 2008, a reintroduction effort attempted to establish the species in Conecuh National Forest by the Alabama Department of Conservation and Natural Resources in cooperation with the Alabama Natural Heritage Program at Auburn University. Other partners included the U.S. Fish and Wildlife Service, Zoo Atlanta, and the Orianne Society in Florida. The project has released approximately 170 snakes to date, with a total of 300 snakes planned to be released in the area. In January 2020, technicians from the Auburn University School of Forestry and Wildlife Sciences and Museum of Natural History found a two-foot hatchling in the project area. It was the first wild-born indigo snake found in the state in decades. In March 2022, a second hatchling was discovered.

Additional Resources

Gibbons, Whit, and Mike Dorcas. Snakes of the Southeast. Athens: University of Georgia Press, 2005.

Godwin, James, et al. "Reintroduction of the Eastern Indigo Snake (Drymarchon couperi) into Conecuh National Forest." Auburn: Environmental Institute, Auburn University, 2011.

Powers, John S. "Alabama's Indigo Snake Population." Courier Journal, July 26, 2014; http://www.courierjournal.net/online_only/article_3f217abe-14f8-11e4-9caf-0019bb2963f4.html.