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The Lord of the Forest
The Eastern Indigo Snake’s scientific name, Drymarchon couperi, translates to ‘Lord of the Forest’. These snakes earned their name through impressive size and status as top predators in longleaf pine ecosystems. Male indigo snakes can reach lengths exceeding 8 feet, which makes them the longest snake species native to the United States. As top predators, indigo snakes move incredible distances between habitats in search of prey. Indigo snakes have the largest documented home range of any snake species native to North America. Individuals can use thousands of acres and travel many miles in a single year (Stevenson and Hyslop 2010; Hyslop et al. 2014). Indigo snakes traverse both upland and lowland systems and consume a wide variety of prey species across many taxonomic groups (Stevenson et al. 2010). Despite a broad potential diet, indigo snakes are perhaps most well-known for their propensity to eat other snakes, including several venomous species such as Copperheads and Eastern Diamond-backed Rattlesnakes. Overall, indigo snakes have earned their reputation as an icon of the globally imperiled longleaf pine ecosystem.
A Long History of Population Declines
Indigo snakes have been listed as Threatened under the U.S. Endangered Species Act since 1978.
The original listing decision was driven, in part, by overcollection for the pet trade. While those pressures have somewhat subsided, indigo snake populations have also declined because of widespread habitat destruction, fragmentation, and degradation across the southeastern United States. Poor habitat management, particularly from a lack of regular fire in longleaf pine systems, and mortality from dense road networks can negatively impact populations even in otherwise protected landscapes (Hyslop et al. 2009; Breininger et al. 2012). Critically, similar factors have also led to the decline of Gopher Tortoises whose burrows provide essential overwintering shelters for indigo snakes. In addition to habitat concerns, there are a litany of other threats to indigo snake populations, including disease, introduced species (e.g., invasive lung worms; Bogan et al. 2022), and direct persecution by humans. Given these threats, recent status assessments have reaffirmed the imperiled status of indigo snakes across their range.
As a result of these stressors, indigo snake populations have declined throughout their range. This includes the complete extirpation of indigo snakes from the Florida Panhandle, southern Alabama, and southeastern Mississippi. The current status of indigo snakes in Peninsular Florida is mostly unknown, while southern Georgia is generally considered a stronghold for the species. However, even populations in Georgia face many challenges to their long-term persistence (Bauder et al. 2017). Current conservation efforts are mostly focused on habitat protection and maintenance for existing populations, monitoring and mitigation of emerging threats, and reintroduction of indigo into the western portion of their historic range.
Indigo Snake Reintroductions
Initial efforts to reintroduce indigo snakes to landscapes without populations were conducted by Dr. Dan Speake in the 1980s. These efforts included the release of 537 snakes spread across 18 sites, but none of these releases are believed to have established a self-sustaining population (Speake 1987; USFWS 2019). With some lessons learned from this initial project, efforts to reintroduce indigo snakes into the western portion of their historic range were revitalized in the mid-2000s. This time reintroductions initially focused on a single site: Conecuh National Forest in southern Alabama.
Releases at Conecuh began in 2010 when 17 snakes were released. Since 2010, mostly annual releases have contributed 350 indigo snakes to the Conecuh landscape. Released individuals are bred at The Central Florida Zoo’s Orianne Center for Indigo Conservation and head-started in captivity for approximately two years before release (Folt et al. 2019). In conjunction with this effort, a second release site was established in 2017 at The Nature Conservancy’s Apalachicola Bluffs and Ravines preserve. Currently, these reintroduction efforts are overseen by a large partnership that includes representatives from state and federal agencies, zoos, and NGOs.
The ultimate goal of conservation programs is to work towards recovery and delisting of imperiled species. For indigo snakes, reintroduction efforts are a fundamental part of range-wide conservation efforts. The U.S. Fish and Wildlife Service describes one of the criteria for delisting as “populations are distributed across at least 12 Conservation Focus Areas with at least 2 population within each of the 4 representative regions.” Thus, current objectives for recovering indigo snakes cannot be met without the successful reintroduction of populations into the Panhandle Region, which has no naturally occurring populations remaining.
A New Threat
A new threat to indigo snake recovery efforts is looming as energy development has been proposed at one of the indigo snake reintroduction sites. As a group, snakes are notoriously difficult to study and monitor in the wild. Despite this, recent efforts at Conecuh have documented encouraging evidence of success for reintroduction efforts, including reproduction of released snakes and dispersal of snakes to habitat patches other than their initial release site. Maintaining this program across nearly two decades to reach a point where there are positive signs of success has required thousands of person hours from stakeholders across many organizations and significant financial investment from both public and private sources.
The ultimate success of these efforts is currently in jeopardy. The U.S. Bureau of Land Management is currently proposing to open the Conecuh National Forest to oil and gas development that would directly impact 2,263 acres. This development would have both direct and indirect impacts on the indigo snake reintroduction effort as well as the associated longleaf pine ecosystem. In addition to outright destruction of habitat, increased development will challenge management of these fire-dependent ecosystems, negatively impact Gopher Tortoise populations, and increase the risks of road mortality for indigo snakes. Critically, these threats are already some of the biggest challenges to creating a self-sustaining indigo snake population in Conecuh. Exacerbating them through new developments could make this goal unachievable.
This article was authored by Drs. Houston Chandler and Chris Jenkins as a response to proposed oil and gas development in Conecuh National Forest. Together, they have nearly three decades of experience working on conservation programs for Eastern Indigo Snakes, including serving key roles in the reintroduction effort.
Literature Cited
Bauder, J. M., D. J. Stevenson, C. S. Sutherland, and C. L. Jenkins. 2017. Occupancy of potential overwintering habitat on protected lands by two imperiled snake species in the Coastal Plain of the southeastern United States. Journal of Herpetology 51:73–88.
Bogan, J. E., D. A. Steen, B. O’Hanlon, M. M. Garner, H. D. S. Walden, and J. F. X. J. Wellehan. 2022. DRYMARCHON COUPERI (Eastern Indigo Snake): Death associated with Raillientiella orientalis. Herpetological Review 53:147.
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Hyslop, N. L., J. M. Meyers, R. J. Cooper, and T. M. Norton. 2009. Survival of radio-implanted Drymarchon couperi (Eastern Indigo Snake) in relation to body size and sex. Herpetologica 65:199–206.
Hyslop, N. L., J. M. Meyers, R. J. Cooper, and D. J. Stevenson. 2014. Effects of body size and sex of Drymarchon couperi (Eastern Indigo Snake) on habitat use, movements, and home range size in Georgia. The Journal of Wildlife Management 78:101–111.
Speake, D.W., D. McGlincy, and C. Smith. 1987. Captive breeding and experimental reintroduction of the Eastern Indigo Snake. Pp. 84–90 in Proceedings of the Third Southeast Nongame and Endangered Wildlife Symposium (R.R. Odum, K.A. Riddleberger, and J.C. Ozier, eds.). Georgia Department of Natural Resources, USA.
Stevenson, D. J., and N. L. Hyslop. 2010. Drymarchon couperi (Eastern Indigo Snake). Long-distance interpopulation movement. Herpetological Review 41:91–92.
Stevenson, D. J., R. M. Bolt, N. L. Hyslop, D. J. Smith, T. M. Norton, K. M. Enge, and K. J. Dyer. 2010. Prey records for the Eastern Indigo Snake (Drymarchon couperi). Southeastern Naturalist 9:1–18.
U.S. Fish and Wildlife Service (USFWS). 2019. Species Status Assessment Report for the Eastern Indigo Snake (Drymarchon couperi), Version 1.1. Atlanta, Georgia.
