Coloration is uniformly glossy black, with red or cream colored accents possible around the chin, throat and sometimes the cheeks. Scales for this species are large and smooth. Eastern indigo snakes are nonvenomous.
Eastern indigo snakes are the longest snakes found in the United States, reaching lengths of 5 to 7 feet (1.5 to two meters), with the record length exceeding 8.5 feet (2.5 meters).
Native to the southeastern United States, eastern indigo snakes occur primarily throughout the peninsula of Florida, north to parts of southern Georgia and Alabama, and to the west, occupying a small portion of southeast Mississippi. Historical range for indigo snakes extended to South Carolina, but the species is considered very rare or extirpated there as well as throughout most of Alabama and Mississippi, although some reintroductions have made in an attempt at population recovery.
Indigo snakes have eight recognized subspecies, two of which can be found in the United States: eastern indigo snakes and Texas indigo snakes. The Smithsonian's National Zoo has two eastern indigo snakes.
Habitats for eastern indigo snakes include a wide variety of environments, depending upon geographic location and seasonal changes. Preferred habitats include pine and scrubby flatwoods, pine rocklands, sandhills, dry prairie, edges of freshwater marshes, agricultural fields and human-altered habitats. Temperature changes can require this species to seek shelter; the northern dwelling eastern indigo snakes most often use gopher tortoise burrows for this purpose. Hollowed logs or rodent burrows also act as sufficient shelter for individuals living in wetter habitats. In central and southern Florida, seeking shelter from cold weather is not necessary, but they may still seek underground refuge in certain circumstances.
Eastern indigo snakes are active, terrestrial predators known to expose and chase down prey. They will occasionally climb shrubs or trees in an attempt to find food. This species eats a wide variety of animals including small mammals, birds, frogs, turtles, turtle eggs and snakes--even venomous species like cottonmouths and rattlesnakes. Juvenile eastern indigo snakes will prey mostly on invertebrates. Prey such as rats that are strong enough to put up a fight are killed not by constriction, but instead by pressing them against stationary structures found in their environment like burrow or tunnel walls. Holding such prey in place requires a strong bite.
Most of what is known about the breeding habits of eastern indigo snakes reflects information gathered from populations in northern Florida. Breeding season runs between November and April, with females laying four to 12 eggs during May or June. Young will hatch after three months of incubation, normally between August and September. In south-central Florida, breeding will occur from June to January, with egg laying occurring between April and July and hatching taking place from mid-summer to early fall. Hatchlings will measure 17 to 24 inches (43 to 61 centimeters) in length.
Females have the ability to store sperm and delay fertilization of eggs if necessary. A single record exists of a captive individual laying five eggs after being isolated for over four years. Additionally, there have been reports of parthenogenetic reproduction, which may question the occurrence of sperm storage for over four years.
Eastern indigo snakes are diurnal.
Information on the life span of eastern indigo snakes in the wild is not available. The longest this species has survived in human care is 25 years and 11 months.
The United States Fish and Wildlife Service has listed eastern indigo snakes as threatened due to a dramatic decline in population. This decline is primarily a result of over-collecting by pet traders, habitat loss and fragmentation, and mortalities as an indirect consequence of the gassing of gopher tortoise burrows by rattlesnake collectors. While it is suspected that fragmented populations could be maintained in protected tracts of wild land in the event of excessive human development, it is not likely that these populations would remain viable.
Conservation actions have been put into place both federally and statewide. Eastern indigo snakes are protected at the state level in Alabama, and have full protection as a threatened species in Florida and Georgia. In South Carolina and Mississippi, they are protected as an endangered species. Further conservation efforts beneficial to eastern indigo snakes would be the protection and preservation of large areas of natural, unaltered habitat. It is difficult to determine how much land would be needed to recover and sustain a healthy population, but research is currently in place to obtain a better idea. Methods of conservation currently in place include prescribed burning to maintain an ideal habitat, continuation of a captive breeding colony, gaining cooperation from local landowners and increased public education and outreach. Expansive tracts of undeveloped land are what will be needed to best help eastern indigo snakes recover.