Eastern indigo snake population monitoring in north-central Florida
October 2022 - September 2023
- U.S. Fish and Wildlife Service
The eastern indigo snake (EIS; Drymarchon couperi) was federally listed as threatened in 1978, with population declines largely caused by anthropogenically-induced habitat loss. The species has declined throughout its range such that natural populations no longer occur in Alabama, Mississippi, or the Florida panhandle, and they are thought to be in decline throughout much of their range in Georgia and Florida. Although peninsular Florida is considered a stronghold for the species, their contemporary distribution in north-central Florida is largely unknown.
The proposed research will address three components of the EIS recovery strategy, focusing on the North Florida Region, which is considered critical for connectivity of peninsular Florida populations with the species’ only other remaining stronghold in southeastern Georgia. We will use occupancy surveys at potential overwintering sites, a protocol used successfully to monitor EIS in southeastern Georgia, to better understand the distribution and status of EIS in the North Florida Region. The surveys will also provide a set of baseline occupancy data for follow-up surveys to monitor trends over time. Additionally, we will conduct more intensive mark-recapture surveys at two focal population monitoring sites in order to collect data to estimate demographic parameters (e.g., survival, population size). Finally, we will also collect blood samples for subsequent hormonal, and toxicologic, and genetic analyses. The genetic analysis will provide an estimate of the effective population size, which can be used to monitor changes in population size over time. It will also be used to evaluate the current level of genetic connectivity across the region, which will inform the recovery process because maintenance of genetic connectivity is listed as a criterion that must be met for delisting.