Eastern Indigo Snake Project

The eastern indigo snake (Drymarchon couperi) is a large (up to 8 feet in length), bluish-black snake found in the extreme southeastern United States. Its range has been severely diminished, and is now only found in disjunct populations in the peninsula of Florida and southern Georgia. The species has been extirpated from southern Louisiana, Mississippi, Alabama, and the Florida panhandle and have been federally and state threatened since 1978.

The eastern indigo snake was once common on Sanibel and Captiva Islands. Observations really started to taper off in the late 1980s, and the last known indigo snake was hit by a bicycle on the Indigo Trail (a trail named after the indigo snake) on the J.N. “Ding” Darling National Wildlife Refuge in February 1999. That snake died at the Clinic for the Rehabilitation of Wildlife (CROW) shortly after. Surveys, trapping protocols, and educational programs asking island residents to document new specimens have failed in verifying any remaining snakes.

The reason for its demise on our islands is mostly from getting run over by vehicles. The eastern indigo snake has the largest home range of any snake found in the United States. The home range of males can be up to two miles. These diurnal snakes can travel a long distance in a given day and are prone to crossing roads frequently. One by one, these snakes were hit by vehicles while crossing or sunning on roads until there were not enough snakes to continue the population.

Eastern indigo snakes are winter breeders. Unfortunately, they are searching for mates and covering a lot of territory while traffic is at its peak on the islands. Indigo snakes are fond of upland areas, and they tend to sleep and seek cover in gopher tortoise burrows. These sun-loving snakes are fond on open grasslands and near the edge of hammocks. As the island became infested with exotic trees such as Brazilian Pepper (Schinus terebinthifolius) and Australian Pine (Casuarina equisetifolia) throughout the 1960s-1990s, the once open landscapes were minimized, and the snakes began spending more time in the remaining open and sunny areas along the roads.

SCCF has partnered with the Orianne Society, a nonprofit organization dedicated to the conservation of reptiles and amphibians, to help assess the remaining populations of the eastern indigo snake in Pine Island Sound. The Wildlife and Habitat Management staff at SCCF has begun inventorying eastern indigo snakes in the area. Ding Darling and the Florida State Park system are collaborating with this research. Residents of Upper Captiva have lent their enthusiasm for the project, with volunteer time and covering the expenses through SCCF’s North Captiva Conservation Fund. Most have come to realize how fortunate they are to live on an island where this animal’s population is still viable.

The snakes are being pit-tagged and measured so a population estimate can be made and movements can be documented. These populations appear to be the last barrier island populations known to science.

The main reason that indigo snakes are able to survive on North Captiva and Cayo Costa Islands is the lack of busy roads and full-size vehicles, with most of both islands held in state park land with large unbisected tracts of land. The first eastern indigo snake from North Captiva (and the first of this project) was brought to CROW by SCCF staff on Feb. 6, 2012 because of unknown injuries. After a remarkable recovery at CROW, it was released by SCCF on April 19, 2012, back to its site of origin. The Orianne Society asks that indigos be given names and the person who found the injured snake on North Captiva chose the name, Kurt.

If you observe any indigo snakes in the area, please document it with a photo without disturbing them to record their location and report it to SCCF. Indigo snakes resemble the very common southern black racer snake (Coluber constrictor priapus), and dark specimens of the Florida watersnake (Nerodia fasciata pictiventris), so be aware that there are other black snakes in the area. For more information or to report a sighting please email indigo@sccf.org or call the SCCF Wildlife Habitat Management office at 239-472-3984.