Current Status and Protection Efforts of the Eastern Indigo Snake, an Overview

by Dean Alessandrini

In a time in the not so distant past, (pre-1965), The Eastern Indigo snake (Drymarchon corias couperi) was the most commonly kept pet snake in the state of Florida. The large, glossy snakes are well known to be non-aggressive and to thrive in captivity, and, therefore, their popularity soared. Over collecting, needless butchering and the practice of gassing the favorite retreat of the Eastern Indigo, Gopher Tortoise burrows, have all taken their toll on these magnificent animals. None of these factors, however, can equal the devastation caused by the principal enemy of the Indigo: the progress of mankind, which equals habitat destruction for the Indigo snakes.

Home Range and Preferred Habitat

Today, the home range consists essentially of South Georgia and Florida.

Past literature references of the range of the Eastern Indigo have been fairly vague. It is generally agreed to have had an original range from South Carolina through the Florida peninsula and westward to southern Louisiana. As early as the 1950’s, the status of the Eastern Indigo was listed as problematic in the states of Mississippi, Alabama, South Carolina and Louisiana. It is generally agreed that, with the possible exception of re-introductory efforts, the Eastern Indigo is extremely scarce if it still occurs in these 4 states.

In Georgia, The Eastern Indigo is limited to the southeast portion of the state, and is typically associated with xeric (sandy, very dry) sand ridge habitat, but can also be found in pine-scrub oak woods, forested sandhills, as well as around wetlands such as swamps, streams and canals.  The Gopher Tortoise, Gopherus polyphemus has a larger range in south Georgia, but occupies much of the same habitat, and the Indigo prefers the burrow of the tortoise as it’s favorite retreat and nesting site.

The Florida range of the Indigo consists essentially of the entire peninsula, with scattered populations in the panhandle. Indigos of Northern and Central Florida primarily inhabit scrub (sandy soiled Pine, Scrub Oak) and swale (highly vegetated, seasonably marshy) habitats. In these regions they prefer the burrow of the Gopher Tortoise as a retreat and nesting site, but may also utilize burrows from Armadillos and other mammals. It is more difficult to study the Indigo in the vastness of the everglades region, but it is presumed that Indigos utilize more diversified habitats in extreme South Florida. It has been reported that they are often found near canals banks, where crab holes are utilized in lieu of Gopher Tortoise burrows. The Subspecies seems to be less restricted in suitable habitat in South Florida than in more Northern parts of its range, probably because of the warmer winters.

Threats to the Survival of The Eastern Indigo

Over collecting 

In the mid 1960’s, Eastern Indigos were collected in mass numbers by Florida dealers, and could be purchased for about $15.00 ea. for adults. By the mid 1970’s, that price had increased to about $90.00 ea.

Prices continued to grow as demand would not subside, and by the late 1970’s, collectors were paying well over $200 per specimen. Collectors also resorted to contacting rattlesnake hunters to collect the snakes while “gassing” Gopher Tortoise burrows for rattlesnakes. Although the animals are protected today, a black market persists, as some “fans” of the Indigo do not seem to care about its plight in the wild.

Extermination

All snakes suffer from needless persecution from the general human population, but the Indigo is a prime candidate. Being large and conspicuous, the Indigo is an easy target for those who fear and therefore kill every snake on sight. These same factors contribute to the animals being killed with frequency by large pets. Numerous accounts of people who “used to” have Indigos on their property but “the dogs got them all” have been recorded. Being active snakes with a very large home range, road mortalities are very frequent as well.

Gassing of Gopher Tortoise burrows:

In Georgia and Florida “Rattlesnake Roundup” hunters spray gasoline into the burrows of the Gopher Tortoise, hoping to evict prize-winning rattlesnakes. Since the Indigo and the tortoises themselves also occupy these burrows, they too are displaced. If not butchered or sold by the hunters, there is a good change they will perish in time from the effects of the fumes. It has been estimated that the gassing of the burrows renders them unsuitable for habitat for a periods of up to seven years.

Decline in numbers of the Gopher Tortoise

The Gopher Tortoise is also a Subspecies in decline. The burrows of these tortoises are regularly over 15 feet long, and sometimes over 30. It has been estimated that in the northern and central parts of their range, over 90% of Indigo snakes lay their eggs in Gopher Tortoise burrows. The burrows provide protection from weather, fire, and predators for many small animals, including both reptiles and mammals. The success of the Gopher tortoise seems essential to that of the Indigo.

Staggering of hatch rate of juveniles

Although I am aware of no studies conducted on wild snakes, it has been my personal observation and that of many others who have captive bred these animals, that the hatchlings do not all emerge at the same time. I have personally noted periods of as long as 2 weeks between the “pipping” (beginning stage of hatching) of the first and last neonates of a single clutch. Once the pipping process has begun, the odors will certainly attract predators, and, if this phenomenon is occurring in the wild, it could certainly lead to increased predation of the newborn snakes and hatching eggs by skunks, raccoons, and even other snakes.

Habitat Destruction, Fragmentation

Without a doubt this is the most serious threat to the Eastern Indigo. In the warmer months, Indigos will utilize as much as 100 or more hectares of habitat (1 hectare = 2.471 acres) Because of these large ranges, even small fragmentations such as homes, farms or roads can result in the ultimate demise of the population.  Large tracts of suitable undisturbed habitat are required to ensure the success of the Eastern Indigo. As the population and development of Florida continues to grow, such suitable regions become fewer and fewer in number.

Fire Suppression

Suppression of natural fires is known to have a negative influence on Gopher Tortoises and, therefore, Indigo Snakes. The absence of periodic fire allows for excessive leaf debris build up which makes for difficult digging, as well as shortage of food sources for the tortoises.

Conservation Status

 The Eastern Indigo Snake was listed as a threatened Subspecies by the Florida Game and Fresh Water Commission (GFC) in 1971, and by the US Fish and Wildlife Service (USFW) in 1978.

 “Threatened” as defined by USFW and GFC: Subspecies that are likely to become endangered in the foreseeable future if current trends continue.

“Endangered” as defined by USFW and GFC: Subspecies in danger of extinction if the deleterious factors affecting their populations continue to operate.

Recovery Efforts

The ultimate objective for protecting the Indigo snake should be focused on protection of large (at least 1000 ha.) of habitat, and ensuring that healthy and reproducing populations of Indigo Snakes populate and are fully protected where suitable habitat still exists in the historical range of the Subspecies.

The Recovery Plan for the Eastern Indigo Snake prepared by the US Fish and Wildlife Service outlines the following measures of action for the recovery of the Eastern Indigo Snake:

1. Maintain and protect existing populations of Eastern Indigo Snakes.

2. Reestablish populations where feasible.

3. Improve the attitude of the public and their behavior towards Indigo Snakes.

The NASA Project

Since the Mid-1970’s, The Biomedical Operations and Research Office at the NASA John F Kennedy Space Center, has been supporting environmental monitoring and research. Goals of their “Strategic Plan” include protection, preservation, and enhancement of the natural environment at KSC.

One of the Subspecies described for monitoring and protection is the Eastern Indigo Snake. Over 60 Indigo snakes in all have been fitted with radio transmitters and periodically tracked for data analysis.

The goal of the study is to collect such data as: home ranges, preferred habitats and nesting areas, principal periods of activity, growth rate, mortality issues etc.

This data will be used to create ideal habitat “modules” that can be sectioned off, eliminated of roads and completely protected. As these modules become more successful and it is determined the number of snakes that can successfully occupy a given area, similar modules may be created in other areas of the state, or even outside the state, within the Indigo’s traditional range.

The depth of this program is truly remarkable, and the Ecologists involved in the study are becoming well known for their educational programs on Indigos throughout the state.

The Creation of Florida Panther National Wildlife Refuge

In 1989, the US Dept of Interior created a 30,000-acre refuge near Big Cypress National Preserve. This region provides habitat and protection for hundreds of Subspecies, including the Eastern Indigo.

Conclusions

The Eastern Indigo Snake is certainly under distress. Habitat destruction, wanton killings, and the pet trade have all taken a serious toll. There is hope, however. Efforts including habitat conservation / reconstruction and education of the general public as to the status and gentle and harmless nature of these beauties are the key to it’s future success. 

Literature References:

US Fish and Wildlife Service. 1982. Eastern Indigo Snake Recovery Plan.

US Fish and Wildlife Service, Atlanta GA. 23pp.

Littschwager, David; Middleton, Susan 1994. Witness, Endangered Subspecies of North America, Chronicle Books 255pp

Conant, Roger; Collins, Joseph T. 1991. A field Guide to Reptiles and Amphibians: Eastern and Central North America. 3^rd ed. Peterson Field Guide series No. 12 Houghton Mifflin Co. 450pp..

US Dept. of Interior, Fish and Wildlife Service, 1994, Endangered and Threatened Wildlife and Plants. Washington, DC (Publisher unknown)

Diemer, Joan E., Speake, Dr. Dan W., The Status of the Eastern Indigo Snake in Georgia.

Alabama Cooperative Wildlife Research Unit, Auburn University, Auburn, GA

Moler, P.E. 1992. Eastern Indigo Snake, Rare and Endangered Biota of Florida, Amphibians and Reptiles.

University of Florida Presses, Gainsville, FL.