Eastern Indigo Snake; an Endangered Species

Drymarchon corais couperi

written by Steven Kite

The eastern indigo snake (Drymarchon corais couperi) is the largest nonvenomous snake in North America. Individuals up to 104 inches have been measured. It derives its name from the dark blue iridescence of it large scales. The blue color is most noticeable just after the snake has shed. Adults are uniformly black or bluish black both above and below, with the chin, throat, and lips usually tinged with reddish or orange pigmentation. The young are lighter in color and have a faint banded pattern.

Indigos lay from five to twelve white eggs in May or June. Hatching occurs in August and September. The young indigos may approach 2 feet long when they hatch.

Indigo snakes feed on small mammals, frogs, toads and other snakes. They feed especially heavily on frogs and snakes. They can eat rattlesnakes and other pit vipers as well as coral snakes, because they are immune to their venom. The indigo snakes large size and strong jaws enable it to eat its prey live. It uses its large body to hold its prey, but does not kill by strangling like snakes which are constrictors. Its victims die from suffocation, as they are eaten head first.

While the indigo snake is widely distributed throughout the American tropics, the eastern subspecies occurs only in southeastern Georgia and throughout peninsular Florida. It is completely isolated from other subspecies populations. The eastern indigo may be found in a variety of habitats throughout most of Florida. It occurs in xeric sandhills in the panhandle, and in central and northern portions of the Florida peninsula. However, it is not restricted to dry habitats. It is fairly common in cabbage palms hammocks, hydric hardwood hammocks and it also frequents areas around ponds.

In drier habitats, the eastern indigo often seeks shelter in gopher tortoise and armadillo burrows as well as stump holes. These dens may be used for egg laying, shedding and for providing protection from dehydration and temperature extremes.

The eastern indigo snake has been classified as a threatened species by the Florida Game and Fresh Water Commission (GFC) since 1971 and by the U.S. Fish and Wildlife Service (USFWS) since 1978. The main reason for its decline is habitat loss. Indigos need relatively large areas of undeveloped land. As habitats become fragmented by roads, indigos will be increasingly vulnerable to highway mortality as they travel through their territories.

They also fall victim to domestic dogs, commercial collecting, gassing of gopher tortoise burrows, chemicals, and killing by uninformed persons.

Some researchers believe that insecticide poisoning may be one of the leading causes of snake mortality, sighting high levels of dieldrin, chlordane, mirex, PCBs, and heptachlor epoxide that has been found in the fat reserves of dead indigos found in Georgia.

Here are some ways you can help the eastern indigo snake:

Learn more about the indigo and its habitat
(some references are listed below:)

Write or call your legislators and express your support for habitat protection and chemical use measures that will help the indigo snake.

Inform others, especially large-tract landowners, about the need to protect the indigo.

Report people who violate the laws that protect indigos.

Legal Aspects

The use of burrow fumigants such as gasoline in illegal in Florida. Indigos may not be sold or kept as pets without special permits from the Florida Game and Fresh Water Fish Commission and the U.S. Fish and Wildlife Service.

Moler, P.E.Distribution of the eastern indigo snake (Drymarchon corais couperi) in Florida. Herp review 16(2):37-38
Moler, P.E. 1987. Delicate Balance. Fla. Wildlife July-August.

Picture Source:
Williams/Carmichael, Florida's Fabulous Reptiles and Amphibians, p. 41