Reaching up to 8.6 feet (2.6 meters), the eastern indigo snake is the largest snake in North America. This species joined the federal "threatened" list in 1978 following a decline in numbers during the 1960s and 1970s.
As part of the installation's Endangered Species Management Plan (ESMP), the Fish and Wildlife Branch at Fort Stewart, Ga., monitors this snake, found in several areas of the installation.
Habitat destruction, highway mortality and illegal gassing of the gopher tortoise burrows frequented by the snake contributed to the decline of its population and continue to threaten its survival. Some populations were depleted by collection for the pet trade prior to listing.
They are known to forage, nest, and shelter in gopher tortoise burrows, relying on them for winter dens. This makes them vulnerable to people who put gas in the burrows to harvest eastern diamondbacks for local rattlesnake roundups. The practice, against federal statute and Fort Stewart regulations, can kill indigo snakes.
Fort Stewart harbors large and secure populations of both the eastern indigo snake and gopher tortoise. Since these species occur in fire-maintained ecosystems, prescribed burning has contributed significantly to the health of these populations.
Several programs are monitoring indigo snakes on post. The installation Fish and Wildlife Branch is conducting a long-term mark and recapture study to better understand population trends. The Wildlife Conservation Society St. Catherine's Island Wildlife Survival Center is assessing the health of the snake. The University of Georgia is conducting a radio-transmitter study of home range and seasonal activity funded by the U.S. Fish and Wildlife Service.
Since 1998, the mark and recapture study has marked a total of 36 indigo snakes (24 males, 12 females) at two study sites. All captures are measured, weighed, checked for gender and marked with passive integrated transponders (PIT) tags and by clipping belly scales.
Preliminary recapture data indicate that reproduction and successful recruitment is occurring for these populations.
In the health assessment study, Terry Norton, a veterinarian, holds indigo snakes from Fort Stewart briefly in captivity where a complete physical exam is performed. A previous study found very high plasma calcium and phosphorus levels in captive indigo snakes, and Norton is interested to determine if these elevated blood levels are found in wild specimens. They are also investigating the cause of a possible vesicular condition that causes skin boils on wild indigo snakes during the winter.
Professor Joseph Meyers and doctoral student Natalie Hyslop will soon begin the radiotelemetry study. Norton will implant the radio transmitters, and Hyslop will track adult male and female snakes. This study should provide valuable information on home range size, seasonal activity and foraging areas.
Fort Stewart Fish and Wildlife Branch biologists hope to better understand the installation's eastern indigo snake population, helping to ensure that the training mission and indigo snake management remain compatible.
Note: Dirk J. Stevenson is a herpetologist with the Fort Stewart Directorate of Public Works Fish and Wildlife Branch.
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