Eastern Indigo Snake

Listing Status

Federal Status: Threatened
FL Status: Federally-designated Threatened
FNAI Ranks: G4T3/S3 (Globally: Apparently Secure, Sub sp. Rare/State: Rare)
IUCN Status: LC (Least Concern)

Appearance

The Eastern indigo snake is a non-venomous, bluish-black colored snake that can reach lengths of eight feet (2.4 meters). Its chin, cheek, and throat are mostly red or brown, but can also be white or black. Most indigo snakes have smooth scales, although adults do have keels (ridges) on the front of some of their scales (Florida Natural Areas Inventory 2001). When approached, the Eastern indigo snake shows no aggression (L. Nester pers. comm. 2011). They are also exothermic species – their body temperature is externally regulated.

Behavior

The Eastern indigo snake’s diet primarily consists of a variety of species, including small mammals, birds, toads, frogs, turtles and their eggs, lizards, and small alligators (National Park Service, n.d.).

Indigo snakes begin breeding between the months of November and April and nest between the months of May and August. Females lay 4-12 eggs yearly or bi-yearly, with the eggs hatching 90 days after being laid. Since the indigo snake is a commensal of the gopher tortoise, females usually deposit their eggs in gopher tortoise burrows. Females may have the ability to hold sperm, which would allow them to defer fertilization of an egg. Parthenogenesis (a form of asexual reproduction) may also be possible with Eastern indigo snakes, as some virginal snakes have been seen laying eggs (Kendrick and Mengak 2010, Smithsonian Marine Station at Fort Pierce, n.d.).

Habitat

Eastern Indigo Snake Range map showing all counties in Florida

Eastern indigo snakes inhabit pine flatwoods, hardwood forests, moist hammocks, and areas that surround cypress swamps. They can be found throughout Peninsular Florida and southeastern Georgia (Florida Museum of Natural History, n.d.).

Threats

The main threats facing the Eastern indigo snake is habitat destruction, fragmentation, and degradation. Habitat destruction is caused mainly by the extension of urban development in their habitat. Indigo snakes lose more than 5% of their habitat each year in Florida (Kendrick and Mengak 2010). As a species that often occupies gopher tortoise burrows, indigo snakes face being injured by people hunting for rattlesnakes in the burrows. This action usually causes death to other species in the burrow including Eastern indigo snakes. Habitat degradation is also a result from this action. Habitat fragmentation is also a threat as increased housing and road development can separate their habitat into smaller individual habitats. Small fragmented habitats can have problems supporting a viable population. Other threats include pollutants, vehicle strikes, captures for domestication, and intentional killings (Kendrick and Mengak 2010, Florida Natural Areas Inventory 2001).

Conservation and Management

The Eastern indigo snake is protected as a Threatened species by the Federal Endangered Species Act and as a Federally-designated Threatened species by Florida’s Endangered and Threatened Species Rule.

Federal Recovery Plan
Reference Materials

Report Sightings

FWC wants to know more about the Eastern Indigo Snake, a federally threatened species. Please report sightings through the Florida Rare Snake Registry, where other rare upland snake species (Southern Hognose Snake, Florida Pine Snake, Short-tailed Kingsnake) can also be reported. Photographs should be included to verify species identification. Reports of these species observed in other states will be accepted.

References

Florida Natural Areas Inventory. 2001. Field guide to the rare animals of Florida.
https://www.fnai.org/PDFs/FieldGuides/Drymarchon_couperi.pdf

Kendrick, M. M., & Mengak, M. T. (2010, September). Eastern Indigo Snake (Drymarchon couperi). Retrieved May 23, 2011, from The Warnell School of Forestry and Natural Resources

National Park Service. (n.d.). Eastern Indigo Snake: Species Profile. Retrieved May 23, 2011, from Everglades National Park:
http://www.nps.gov/ever/naturescience/easternindigosnake.htm

Smithsonian Marine Station at Fort Pierce. (n.d.). Drymarchon couperi. Retrieved May 23, 2011, from North American Mammals.