Creating populations where there are none: A history of efforts to reintroduce Eastern Indigo Snakes


Juvenile Eastern Indigo Snake next to an egg – Dirk Stevenson

At the beginning of 2020, I gave a presentation on the history of Eastern Indigo Snake conservation at the 9th World Congress of Herpetology. It was a great opportunity to share the extensive work that has gone into stabilizing and protecting indigo snake populations across the southeast with an international audience that knew little about indigo snakes. Despite spending only a couple of minutes discussing the ongoing reintroduction project, the majority of the questions that I received after the presentation concerned this issue. Translocations (moving animals to new areas) and reintroductions were actually a hot topic at this conference as this type of management action becomes increasingly necessary. Scientists aren’t the only ones who seem to be drawn to this aspect of indigo snake conservation. I answer more emails from the general public about indigo snake reintroductions than any other project that I have been involved in while working for Orianne.

Approximate range of the Eastern Indigo Snake – Javan Bauder

So, why does the reintroduction project seem to captivate the interest of the conservation community and the broader public? I think there are a few reasons for this widespread interest. First, one of the most challenging aspects of conservation revolves around restoring populations that were lost before effective threat management could be implemented. Indigo snakes are not unique in suffering from extensive range contractions, with large areas of theoretically suitable habitat occurring in regions where populations no longer exist. There is a real need in the conservation world to understand how to best implement translocations and reintroductions, and these techniques have become more prevalent as the threats from habitat loss, invasive species, and climate change impact species at large spatial scales. The widespread translocation of Gopher Tortoises in Florida is an example of this approach being implemented to save individuals from the tide of habitat loss. Second, releasing the largest native snake in the U.S. to places where it no longer occurs is sure to spark strong emotions in both snake lovers and haters. One needs only to read the comments on any article about the indigo snake reintroductions to see this in action. Third, indigo snakes are commonly kept as pets and are regularly bred in captivity. Many people who breed indigo snakes have reached out to express an interest in donating snakes to the reintroduction project as a way to help the conservation efforts (more on the complexities of this issue below). Overall, reintroductions are a fascinating, and sadly often necessary aspect, of large-scale conservation efforts for species that have experienced significant declines.

Reintroduction efforts for indigo snakes actually began all the way back in the late 1970s. Dr. Dan Speake and colleagues bred and released indigo snakes at sites in Mississippi, Alabama, Florida, Georgia, and South Carolina (Speake et al. 1987). Unfortunately, these initial efforts were unsuccessful in establishing new populations of indigo snakes. These early attempts did provide evidence that rearing and breeding indigo snakes in captivity for eventual release was possible and that released snakes could survive in the wild. There was even evidence that released snakes were reproducing at one site. However, this suggestion of early success highlights one of the most important aspects of reintroductions – this is frequently overlooked by the general public – that releasing individuals and creating a self-sustaining population are two completely different things. The complexities of population biology are a topic for another article, but the failure of early attempts to reintroduce indigo snake populations highlights the challenges for this type of project.

Eastern Indigo Snake hatchlings – Orianne Center for Indigo Conservation

When the Orianne Society was founded in 2008 reviving the indigo snake reintroduction project was a critical component of the overall mission to conserve indigo snakes. But what would make this attempt likely to succeed when the previous efforts had failed? One of the first steps was establishing the Orianne Center for Indigo Conservation (OCIC) at the Central Florida Zoo. Opened in 2012, this facility became the permanent home for the captive indigo snake colony that produces snakes to use in the reintroduction project. The facilities at the OCIC were specifically designed around a long-term captive breeding program and include large outdoor enclosures that benefit individuals and their reproductive abilities by mimicking conditions that would be found in nature. Another important achievement was forming the Eastern Indigo Snake Reintroduction Committee, which brings together stakeholders to oversee the project and maximize its chances for success. Even with this infrastructure in place there were still significant challenges for a project of this nature.

Indigo snake in outdoor enclosure at the OCIC – Sean Antonio

The most obvious challenge when initiating a captive breeding and reintroduction program for a threatened species is finding the animals needed to create the captive colony. Reintroductions generally require many releases of individuals into the wild, and indigo snake natural history makes it impossible to collect snakes from the wild in sufficient numbers to achieve this goal. Doing so would damage the existing indigo snake populations. Thus, the decision was made to collect gravid females from Georgia populations. Their progeny were used to start the captive colony while the adults were returned to the wild to minimize the impacts on those populations. Over the years, these original founders have been supplemented with other snakes from both Georgia and Florida and by retaining a small portion of the captive bred individuals. Maintaining genetic diversity and healthy breeding snakes are top priority in the captive breeding program because a sufficient number of young snakes must be produced each year to sustain the release program.

Releasing a captive bred indigo snake – Orianne Center for Indigo Conservation

With the captive colony established and producing snakes every year, the biggest challenge was sustaining the project (logistically and financially) over a long enough time period to have an opportunity for success. Initially, the project was designed to occur at a single site in Alabama with annual releases of snakes occurring for at least 10 years (Stiles et al. 2006). Population modeling suggested that at least 300 individuals would need to be released over this time period to create a self-sustaining population. Subsequent analyses have further highlighted the need to release large numbers of snakes and shown that there are quantifiable differences in the probability of success based on different release strategies (Folt et al. 2019a). In 2017, the reintroduction program expanded to incorporate a 2nd site in the Florida panhandle. As of this year, annual releases have continued at each site, and a total of 191 and 69 individuals have been released in Alabama and Florida, respectively. These releases will continue annually for the foreseeable future, and there was some additional good news this year as the first offspring from reintroduced snakes were captured in Alabama.

There are a couple of other topics worth mentioning when discussing the indigo snake reintroduction project. The first is the controversy that occurred in 2016 when genetic analyses were used to suggest there were two species of Eastern Indigo Snake (Krysko et al. 2016). Follow-up analyses were unable to replicate these results when using a larger dataset and additional techniques (Folt et al. 2019b), and USFWS currently only recognizes a single species of Eastern Indigo Snake. The second issue is what role, if any, can private indigo snake collections play in the reintroduction process. There are no easy answers here, and it is often discussed at the annual reintroduction committee meetings. On the one hand, additional snakes to release in the wild would be a good thing, but on the other, it is hard to guarantee the health and genetic makeup of snakes from these types of collections. These issues could jeopardize the success that has been made over the last 12 years. At some point in the future, incorporating privately bred indigo snakes into the release program may occur but the current logistical challenges outweigh the benefits. Overall, these two challenges highlight the complex nature of reintroduction programs.

Indigo snakes breeding in captivity – Orianne Center for Indigo Conservation

Will we live to see a time when indigo snakes recapture some of their former range? This is the ultimate question facing the reintroduction program. With continued support, it is likely that indigo snake populations at both reintroduction sites will become self-sustaining within the next 10–20 years. Success will obviously depend on appropriate habitat management occurring at a landscape scale and the long-term stability of the Gopher Tortoise populations on these properties. If reintroductions at these sites are successful, there are several other potential properties that could support indigo snake populations. Only time will tell if the Lord of the Forest will return to its forest, but I am optimistic that I will live to see it.

Literature Cited

Folt, B., C. P. McGowan, D. A. Steen, S. Piccolomini, M. Hoffman, J. C. Godwin, and C. Guyer. 2019a. Modeling strategies and evaluating success during repatriations of elusive and endangered species. Animal Conservation 23:273–285.

Folt, B., J. M. Bauder, S. Spear, D. J. Stevenson, M. Hoffman, J. R. Oaks, P. L. J. Wood, C. Jenkins, D. A. Steen, and C. Guyer. 2019b. Taxonomic and conservation implications of population genetic admixture, mito-nuclear discordance, and male-biased dispersal of a large endangered snake, Drymarchon couperi. PLoS ONE 14:e0214439.

Krysko, K. L., M. C. Granatosky, L. P. Nuñez, and D. J. Smith. 2016. A cryptic new species of Indigo Snake (genus Drymarchon) from the Florida Platform of the United States. Zootaxa 4138:549-569.

Speake, D. W., D. McGlincy, and C. Smith. 1987. Captive breeding and experimental reintroduction of the eastern indigo snake. Pages 84–90 in R. R. Odum, K. A. Riddleberger, and J. C. Ozier, editors. Proceedings of the third southeast nongame and endangered wildlife symposium. Georgia Department of Natural Resources, Athens, Georgia.

Stiles, S., J. Stiles, J. C. Godwin, C. Jenkins, E. M. Rush, B. Lock, V. M. Johnson, M. Wines, and C. Guyer. 2013. Repatriation of eastern indigo snakes to conservation lands in South Alabama, USA. Pages 37-41 in P. S. Soorae, editor. Global Re-introduction Perspectives: 2013. IUCN/SSC Re-introduction Specialist Group (RSG), Gland, Switzerland.