Release Site Selection

We have decided to select 3 initial reintroduction sites distributed across the Panhandle region; an area within Conecuh National Forest, Apalachicola Bluff and Ravines (a TNC Preserve), and Nokuse Plantation (a privately owned preserve). Once eastern indigo snake populations are self sustaining at the 3 initial sites we will evaluate additional sites. We selected repatriation sites by considering a number of issues that will influence success, including:

 

• Factors causing snake decline: it is important to determine and mitigate for the factors that caused the original decline of eastern indigo snakes at potential release sites before trying to restore populations. Given that eastern indigos have declined across the entire panhandle region, the factors that caused the declines likely occurred at a regional scale.

 

• Restoration and Long-Term Management of Release Sites: it is important that habitat conditions on release sites are restored for eastern indigo snakes as well as gopher tortoise. Restoration of sites including prescribed burning, select removal of hardwoods, and replanting of ground cover. Understory and tree species will be important considerations in preparation for reintroduction. A commitment to annual habitat assessments at repatriation sites, and keeping current with recommended actions and schedules will be essential for long-term success.

 

• Size and Connectivity of Sites: little is known about the spatial population structure and ecology of eastern indigo snake populations. Specifically, the minimum size of habitat patches required to maintain a viable population, and the habitat components that are required to maintain connectivity among populations. However, there are studies that suggest that individual animals require large protected areas that contain a diversity of habitat types.

 

• Occurrence at Potential Sites: we are currently interested in repatriation efforts and not augmenting existing populations. Thus, it is important to know if eastern indigo snake populations currently occur at potential reintroduction sites. Though there have been no recent sightings of eastern indigo snakes in the Panhandle region since the late 1990’s, this species can be difficult to find in the wild and further surveys are required before repatriation efforts begin.

 

• Dedicated Partners: one of the most critical issues to the success of repatriation efforts will be establishing and maintaining partnerships with a variety of agencies, organizations, and private individuals. Specifically, it is important to work closely with permitting agencies and entities that own release site.

 

Release Strategies 

The strategies used to release animals can have a significant effect on success. When considering how to release eastern indigo snakes we are considering how many should be released per site, snake age and size, timing of release, sex ratios, snake health, genetics, and imprinting on seasonal habitats. The following specific guidelines may be adjusted based on conditions at release sites or the experimental model for different release sites:

 

• Quantity Released: we plan to release approximately 30 eastern indigo snakes per year at each release site. We plan to continue releasing snakes at this rate until we determine that the release sites are reaching carrying capacity.

 

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  Young Eastern Indigo snake, photo credit Dirk Stevenson
  Age and Size: we plan to raise eastern indigo snakes in captivity for approximately 1.5 years, at which time they will be released into soft release enclosures. Snakes will be released from enclosures when they are approximately 2 years old. Snakes at this age should be able to accommodate PIT-tag placement and transmitter implantation. We also may experiment to determine if we could have greater success by releasing snakes that are 1, 1.5, or 2 years old.

 

• Sex: a sex ratio of 1:1 would be ideal in establishing each new population. Some studies have found a ratio of 2:1, males to females in wild populations. A higher number of released males may not be detrimental in repatriation projects. 

 

• Health Assessments: pre-release screening of each snake is critical to the adaptive success of the individuals released, and for the preemption of disease vectoring into wild populations of reptiles. Testing and screening prior to release in repatriation areas will be similar to the procedures for snakes entering quarantine. Diagnostics will include a complete physical examination and body condition score, CBC, chemistry, protein electrophoresis, multiple fecal enteric bacterial pathogen cultures, fecal examination including checking for amoebiasis and other protozoan organisms and performing multiple fecal flotations. Diagnostics for Cryptosporidia and Paramyxovirus serology will also be completed. All specimens will be scale clipped and implanted with PIT-tags if not already implanted. Only upon approval by a designated veterinarian will a snake be cleared for transport and release.

 

• Genetic Considerations: preliminary evidence suggests that an Atlantic clade and Gulf clade eastern indigo snakes exist. However, these data need to be analyzed further before this information can be assessed. Project Orianne is working with University of Florida to further analyze this data set and determine the levels of differentiation between the clades. In addition, we are also interested in conducting research that looks at differentiation using nuclear genes. If there is indeed significant differentiation between clades, we will use animals from the Gulf clade to reestablish populations in the panhandle region.

 

• Imprinting on Seasonal Habitats: we will release snakes during their second winter into soft release enclosures that have an abundance of overwintering habitat. Conservation biologists currently promote a “soft release” scenario for reintroduction programs. This requires the release of an animal first into an enclosure at the release site for a period of time so it may acclimate to the site, prior to release into the wild. This period in which snakes are maintained in the soft release enclosure provides for an orientation period, and may reduce stress factors associated with adapting to a new environment.

 

Release Site Monitoring 

Repatriation sites for eastern indigo snakes will be monitored annually to determine continued presence, relative abundance, survival, and whether reproduction and recruitment is occurring. Implementing a monitoring program will allow us to use an adaptive approach to increase success. Snakes will continue to be released at sites until it is determined the site is reaching carrying capacity as evidence by successful reproduction, high rates of emigration from the release site, and stabilizing abundance estimates. Snakes will continue to be monitored after releases are ceased to determine if the population is sustainable without continued releases. The following field methods will be used to monitor eastern indigo snakes at repatriation sites:

1. Visual encounter surveys at/near gopher tortoise burrows, other animal burrows, and stumpholes in sandhill habitats during the cooler seasons.
2. Canine surveys at gopher tortoise burrows are also an effective field method that may be used to locate eastern indigo snakes and their shed skins. When the trained detector dog signs/indicates at a particular burrow using this technique, the burrow must then be scoped with a burrow camera in an effort to document actual snake presence.
3. Placement of large “box traps” along drift fence arrays in sandhill habitats near gopher tortoise colonies occupied by overwintering eastern indigo snakes; we may also employ this technique in an effort to secure snakes.

The following data will be recorded for each eastern indigo captured, and recaptured, at repatriation sites: date, state, county, site, GPS lat/long, sex, and/or presence of weak keels on the median dorsal scale rows, snout-vent length, tail length, total length, PIT code, habitat and microhabitat type. Additionally, small ventral scale clips will be taken and preserved in 90% ETOH so that they are available any for future genetic analysis.

The body condition and health of eastern indigo snakes captured at repatriation sites will be described noting the prevalence of a boil-lesion condition that is common to this species, and also scoring each snake’s body condition based on residual mass (i.e., the snakes mass relative to the mass of an average snake of the same length). A skilled DVM, PhD will conduct health assessments including blood and stool profiles on a select number of snakes from each site annually.