Indigo Snake: Jewel of the Pine Savanna

By Ethan Hatchett

A thriving longleaf pine savanna can conjure up images of gaping gopher tortoise burrows, red-cockaded woodpeckers feeding young in their cavity nests high in the pines and colorful wildflowers carpeting the forest floor. But one important resident of this forest can be easily overlooked because of its quiet, secretive nature.

The eastern indigo snake is a nonvenomous, apex predator of the longleaf pine savanna. It is North America's longest native snake with adults stretching up to 82 inches, or nearly 7 feet long. (The largest on record topped 8 1/2 feet.) Indigo snakes have a black, thick body with iridescent purple or blue highlights when viewed in sunlight. The snake's chin and cheeks are usually red or orange, a sharp contrast with its dark body.

In the Southeast, indigo snakes are restricted to dry, pine-oak sandhills, which they usually share with gopher tortoises. These snakes use gopher tortoise burrows as shelter during the winter for nesting and refuge. During warmer months, indigos disperse throughout the sandhills and may move long distances, often foraging along wetland edges.

Breeding occurs from November until April, and females typically lay 5-10 eggs during May or June. Eggs are often placed in the moist sand of tortoise burrows. Females can store sperm for at least four years for future fertilization. Males defend territories, and encounters with other males may result in combat and even cannibalism.

Indigo snakes are active only during the day. During the summer they prefer wetland edges where prey is abundant, but they move to drier habitats in the winter. Indigo snakes are more active in cold weather than most other snakes. They regularly feed on mammals, birds, frogs and other snakes, including rattlesnakes and cottonmouths.

When cornered, indigos may flatten their heads, hiss and vibrate their tails, which produces a rattling sound. Despite these intimidating acts, often referred to as a bluff, they rarely bite.

As the number of gopher tortoises has decreased, so has the number of indigo snakes. These snakes depend on tortoise burrows more than any other vertebrate burrow associate. It can be assumed that the well documented reduction in the abundance of gopher tortoises has likely affected the status of the indigo.

The natural habitat of Georgia's Coastal Plain has been drastically changed because of agricultural and silvicultural activities, forcing indigo snakes into smaller, isolated compartments of suitable habitat. What was once a wide-ranging species now must frequently cross roads to reach separated areas of suitable habitat. As a result, indigo snakes have become increasingly vulnerable to vehicles.

Many populations also were depleted by collection for the pet trade before the species was protected as threatened under the Endangered Species Act in 1978. And despite being illegal, the continued practice of introducing gasoline down gopher tortoise burrows ("gassing") to drive out eastern diamond-backed rattlesnakes results in the death of many burrow inhabitants, including the indigo snake.

These threats and the snake's status have resulted in the eastern indigo snake being considered a high-priority species for conservation in Georgia's State Wildlife Action Plan.

This comprehensive conservation strategy, which is undergoing a periodic revision, lists 640 native animal and plant species as priorities for conserving statewide. The 150 conservation actions recommended in the plan focus restoration and protection efforts where they're most needed and most effective.

DNR and others are working to conserve the indigo snake. Key sites are being restored through efforts such as prescribed fire. And in a study funded by DNR, The Orianne Society is researching how many indigo snakes inhabit suitable habitat in south Georgia. The study focuses on assessing the presence of the snakes on sandhills in the Altamaha, Alapaha and Satilla river drainages. Each survey season, a subset of sites is checked, with a total of approximately 60 sites surveyed over three years. During each winter survey season, sites are visited three times and walked by one or more observers searching for indigos.

The University of Georgia Marine Extension is conducting a telemetry study of indigos on state lands to investigate interactions between the snakes and translocated populations of gopher tortoises. Snakes were captured on sandhill sites near the populations and fitted with external radio transmitters to monitor their movements. While transmitters are usually implanted in snakes, attaching them externally is a less invasive option and one that shows promise for use in tracking large, rare snakes, such as indigos.

Coinciding with The Orianne Society's work, DNR has conducted a mark-recapture study of indigos on other lands for six years. In 2023, staff tagged 27 "new" indigos with PIT, or passive integrated transponder, tags and recaptured 25 individuals that had been tagged before. Mark-recapture data will be used to uniquely identify individual snakes and help assess population estimates and trends. This effort is being continued in 2024.

The eastern indigo snake is an irreplaceable part of Georgia's landscape. As an apex predator, the snake plays a critical role in keeping its ecosystem healthy and balanced. Not only is this animal valuable from an ecological viewpoint, it's also one of the most beautiful animals in the state. There is no other snake quite like the indigo.

Ethan Hatchett is a communications assistant in DNR's Wildlife Conservation Section.

Top: Eastern indigo snake resting on a log (Mark Krist)

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