Once upon a time on Sanibel, the Eastern indigo snake (Drymarchon couperi) was considered a common snake species. These gentle giants are a unique species that are severely imperiled in their native range of the extreme Southeast United States. The last documented indigo snake on Sanibel was in 1999. It is now considered extirpated (extinct in an area) on Sanibel and Captiva; however, nearby islands contain small populations of these magnificent and highly protected animals.
The Eastern indigo snake is often cited as the longest native snake in the United States with a record size of 9.2 feet. However, the average size typically seen in the wild is five to six feet. Indigos are often confused with Southern black racers (Coluber constrictor priapus), which is the most common snake in South Florida. The average adult Southern black racer in Southwest Florida ranges from two to four feet and is much thinner in diameter than the indigo snake.
Indigos were protected by the state on Florida in the early 1970’s and federally listed as a threatened species by the U.S. Fish and Wildlife Service in 1978. Previously, they occurred throughout Florida and southern Georgia, Alabama, and Mississippi, but increasing development on large tracts of land have caused a steep decline in their numbers throughout this wide range. Indigo snakes are docile creatures that eat venomous snakes endemic in Southwest Florida and small reptiles and rodents.
When a road is built through a natural or rural area, indigo snakes are typically soon found dead from vehicle strikes. The fact that they breed during the winter (approximately Thanksgiving to Valentine’s Day) means that they are active and crossing roads more frequently while looking for mates when traffic approaches its peak in Southwest Florida due to winter residents and tourists. This is the reason they are no longer found on Sanibel and Captiva. Despite the island’s generous amount of conservation lands, these snakes, like so much wildlife, don’t recognize borders.
SCCF started the Pine Island Sound Eastern Indigo Snake Project in 2012 to inventory and research the remaining populations since they were considered extirpated on Sanibel and Captiva. SCCF has evidence that shows a decline on Pine Island Sound’s islands as well. These animals are in serious trouble, and many have predicted that they could be functionally extinct by the end of the century or sooner without a sound solution.
One idea that has been brought up over the last two decades is reintroduction. However, this would not make any sense because they are still vulnerable to car strikes on major roadways, such as Sanibel-Captiva Road. One idea is to elevate Sanibel-Captiva Road from Tarpon Bay Road to Blind Pass so wildlife can freely move north and south under the road. Another idea is to create a barrier across the entire length of the road with eco-passes or tunnels underneath at active areas where the most roadkill is found. It is believed that if this is done, Eastern indigo snakes could have a chance on Sanibel west of Tarpon Bay Road. These solutions are major undertakings that are sure to be costly and demand the commitment of the entire community.