MONTGOMERY-The Eastern indigo snake (Drymarchon couperi) is the longest snake in North America. Specimens have been documented at more than 8.5 feet long and weighing more than 10 pounds. As the name implies, their overall coloration is a deep, lustrous, bluish black. Most have creamy or reddish areas on the chin, throat and cheek. Indigo snakes have rather large, smooth scales except for some big males who have a few rows of lightly keeled (ridged) scales down the center of their backs. Indigo snakes are usually relatively docile, rarely attempting to bite if handled.
Indigo snakes once occupied virtually all of Florida, southeastern Georgia and extreme southern Alabama. In peninsular Florida, they used a variety of habitats including stump holes, hollow logs, animal burrows, etc. for winter refuge. Throughout the rest of their range, their presence has been closely associated with mixtures of habitats that include high, dry, sandy ridges, usually forested with longleaf pine and scrub oaks (“sandhills”), pine flatwoods, and lower, more densely vegetated wetland areas. Indigo snakes − juveniles in particular − use the lower, wetter portions of their home range for foraging during the warmer months, while the higher, drier areas are used more heavily in winter.
Gopher tortoises (Gopherus polyphemus) and their burrows seem critical to the existence of indigo snakes in their northernmost range. These burrows, most often dug in the loose soil of the sandhills, provide indigo snakes refuge from both winter’s cold and summer’s heat. Gopher tortoise burrows are also used by females as sites for breeding and laying eggs. Indigo snake breeding is believed to occur from October through February in Alabama.
Indigo snakes are opportunistic feeders that eat small mammals, birds, lizards, frogs, toads, and other snakes, including venomous species. Indigo snakes are immune to the venom of the native pit vipers they are likely to encounter.
Populations of Eastern indigo snakes have declined dramatically in recent decades, and the species is now federally listed as Threatened across its range. Primary reasons for the species decline include collection for the pet trade; continuing habitat degradation, fragmentation, and loss; road kills; and mortality associated with the “gassing” of gopher tortoise burrows by rattlesnake hunters. It is illegal in Alabama to place gas or any other noxious chemical in any wildlife burrow or den. Deliberate persecution by man, indirect poisoning by pesticides and herbicides, and a decline in gopher tortoise populations are also believed to be contributors to population declines. While still relatively common in portions of Georgia and Florida, populations are quickly becoming more and more fragmented. The species is now rare in the panhandle region of Florida, and may have disappeared entirely from Alabama.
Efforts to improve indigo snake populations in Alabama have included both conservation of suitable habitat and efforts to reintroduce the species to areas where it once existed. Several restocking efforts were made during the 1970s and 1980s, but surveys in 2005 and 2006 provided no evidence of indigo snakes anywhere in the state. In 2007, preparations began for a new reintroduction effort in suitable habitat within the Blue Spring Wildlife Management Area portion of the Conecuh National Forest in south Alabama.
Eggs were acquired from gravid (pregnant) female indigo snakes collected from southeast Georgia. These females were held in captivity until they laid their eggs, after which the snakes were released at the site of their capture. Eggs were incubated until hatching and the young snakes remained in captivity until they were 2 years old. Each juvenile indigo snake had a radio transmitter implanted inside its body to allow movements to be followed. Plans are to release snakes at the same site for 10 years with the hope of establishing a stable population.
In June 2010, 17 2-year-old Eastern indigo snakes were released. Releases since that time have included 31 snakes in 2010, 30 snakes in 2011, 20 snakes in 2012, and 20 in 2013. Notably, however, two females recaptured for transmitter replacement in 2012 laid eggs while in captivity. This proves with certainty that members of the very first group released are successfully breeding in the wild. The young snakes hatched from these two clutches of eggs were released in 2013 when almost a year old.
Data collected through radio tracking of released indigo snakes through 2011 has been informative. Mortality was found to be approximately 50 percent during the first year, but 10 percent or less during subsequent years. Predation and road kill were the major identifiable causes of observed indigo snake mortality.
The average maximum distance moved from the release site for all monitored snakes has been 0.98 mile. This differed between the sexes with females moving only about half as far as males. Average home range size for all released individuals was 267.62 acres. As might be expected, the average home range size of males was more than twice that of females. It is hoped that each year will provide more insight into indigo snake behavior, movements, home range size and survival needs, and that Alabama will once again have a viable Indigo snake population.
MEDIA RELEASE/ John S. Powers, Area Wildlife Biologist, Alabama Division of Wildlife and Freshwater Fisheries
