The eastern indigo snake (Drymarchon couperi) is a species of large, nonvenomous snake in the subfamily Colubrinae of the family Colubridae. Native to the Southeastern United States, it is the longest native snake species in the country.<!-- only the longest in "North America" if using a restrictive and unconventional definition where only the US+Canada are included; Mexico is home to Boa imperator and Cuba to Chilabothrus angulifer -->

thumb|Eastern indigo

Taxonomy and etymology

Taxonomy

The eastern indigo snake was first described by John Edwards Holbrook in 1842. For many years, the genus Drymarchon was considered monotypic with one species, Drymarchon corais, with 12 subspecies, until the early 1990s, when Drymarchon corais couperi was elevated to full species status according to the Society for the Study of Amphibians and Reptiles, in their official names list.

Etymology

The generic name, Drymarchon, roughly translates to "lord of the forest". It is composed of the Greek words drymos (Δρυμός), meaning "forest", and archon (ἄρχων), meaning "lord" or "ruler".

The specific name is a latinization of the surname of American planter James Hamilton Couper (1794&ndash;1866). Couper brought Holbrook the type specimen from south of the Altamaha River in Wayne County, Georgia.

Common names

Drymarchon couperi has a number of common names, including black snake, blue bull snake, blue gopher snake, blue indigo snake, eastern indigo snake, and indigo snake.

Description

The eastern indigo snake has uniformly blue-black dorsal scales, with some specimens having a reddish-orange to tan color on the throat, cheeks, and chin. This snake received its common name from the glossy, iridescent dorsal and ventral scales which can be seen as blackish-purple in bright light. This smooth-scaled snake is considered to be the longest native snake species in the United States.<!-- only the longest in "North America" if using a restrictive and unconventional definition where only the US+Canada are included; Mexico is home to Boa imperator and Cuba to Chilabothrus angulifer --> A typical mature male measures in total length, with a reported average of , and weighs , reportedly averaging . Males that measure longer than 1.2 m (4 ft) tend to possess weak keels on mid-dorsal scale rows 3–5, while females lack this characteristic. Mature females typically measure around in total length, averaging , and weigh , averaging . Specimens over can weigh up to . Although the eastern indigo snake is similar in average body mass, extremely large specimens of the bulky, sympatric venomous eastern diamondback rattlesnake can outweigh it.

Geographic distribution

The eastern indigo snake inhabits areas from Florida to the southern areas of Georgia and Alabama. Studies in Georgia showed that the most indigo snake sightings happen within the Tufton Upland region of the Coastal Plain especially in the sand ridges. Their historic range extended into Louisiana, Mississippi, and South Carolina. In 2012 the Alabama Department of Conservation and Natural Resources had listed the species as possibly extirpated within the state. A reintroduction program has shown initial signs of success, with an individual sighted in March 2022.

The eastern indigo snake was largely eliminated from northern Florida due to habitat loss and fragmentation. A restoration program is currently underway at Apalachicola Bluffs and Ravines Preserve (ABRP) in northern Florida. It was last observed at ABRP in 1982, until 2017, when 12 snakes were released as part of the program. Twenty more snakes were released in 2018, with another 15 (10 females and five males) in 2019. The 10-year program is a collaborative effort between the Florida Fish and Wildlife Conservation Commission and private partners.

NatureServe considers the species to be "endangered".

Another issue facing the species is infections due to the snake fungal disease caused by Ophidiomyces ophiodiicola. This fungus infects the dermal layer of snake skin, causing a variety of lesions that commonly manifest on the head and near the vent.

Preferred habitat

The eastern indigo snake frequents flatwoods, hammocks, dry glades, stream bottoms, cane fields, riparian thickets, and high ground with well-drained, sandy soils. The species is also strongly associated with longleaf pine and scrub oak communities which usually have turkey oak, live oak, and sand post oak trees. Georgia, they occur in the middle and lower coastal plain. In the northern parts of its range it is restricted to sandhills and requires gopher tortoise burrows during colder seasons. Xeric slash pine plantations seem to be preferred over undisturbed longleaf pine habitats. In these sandhill environments, foraging, nesting, ecdysis, and potentially mating occur at or in these burrows.

The eastern indigo snake is most abundant in the sandhill plant communities of Florida and Georgia. These communities are primarily scrub oak-longleaf pine (Pinus palustris) with occasional live oak (Quercus virginiana), laurel oak (Q. laurifolia), Chapman's oak (Q. chapmanii), and myrtle oak (Q. myrtifolia). Other communities include longleaf pine-turkey oak (Q. laevis), slash pine-scrub oak (Pinus elliottii), pine flatwoods, and pine-mesic hardwoods. Burrows need to be in areas with no flooding. The eastern indigo snake heavily uses debris piles left from site-preparation operations on tree plantations.

Food habits and behavior

The eastern indigo snake is carnivorous, like all snakes, and consumes any other small animal it can overpower. It has been known to kill some of its prey by pressing the prey against nearby burrow walls. They will stick their heads into stump holes or burrows, patrolling fringes of wetlands, or potentially climbing after prey. Captive specimens are frequently fed dead items to prevent injury to the snake from this violent method of subduing its prey. Chemosensory studies with mice (Mus musculus) have shown that D. couperi responds with significantly elevated rates of tongue

flicking and investigation towards visual cues of prey, and not volatile chemical cues. They are diurnal, terrestrial snakes that are regarded as wide-ranging, active foragers. Its diet has been known to include other snakes (ophiophagy), including venomous ones, as it is immune to the venom of the North American rattlesnakes. The eastern indigo snake also eats slugs, turtles, lizards, frogs, toads, fish, a variety of small birds and mammals, and eggs.

As defensive behavior, the eastern indigo snake vertically flattens its neck, hisses, and vibrates its tail. If picked up, it seldom bites.

It often cohabits with gopher tortoises in their burrows, although it will settle for armadillo holes, hollow logs, and debris piles when gopher tortoise burrows cannot be found. Hunters, hoping to flush out rattlesnakes, often accidentally kill indigo snakes when they illegally pour gasoline into the burrows of gopher tortoises (a practice referred to as "gassing"), even though the tortoises themselves are endangered and protected.

Predators

As an apex predator, the eastern indigo snake has few natural predators. Instead, humans represent the biggest threat. Highway fatalities, wanton killings, and over-collection for the pet trade adversely affect snake populations. Snakes are taken illegally from the wild for the pet trade. The eastern indigo snake is sometimes "gassed" in its burrow by rattlesnake hunters. Along with increasing infrastructure and the pet trade, eastern indigo snake populations are drastically declining due to habitat fragmentation. The eastern indigo snake's decline is correlated with the gopher tortoise's decline as well. since the eastern indigo snake utilizes the gopher tortoise's burrows for brumation.

In Florida, the eastern indigo snake may be eaten by some growth stages of invasive snakes such as the Burmese python, reticulated python, Southern African rock python, Central African rock python, boa constrictor, yellow anaconda, Bolivian anaconda, dark-spotted anaconda, and green anaconda.

Reproduction

The eastern indigo snake is oviparous. Its eggs are long by wide. The female lays a single clutch of 4–14 eggs from late April through early June. The hatchlings are long. The eastern indigo snake is often referred to as a late maturing colubrid; it usually does not reach maturity until it is 3–5 years old and around 5–6 feet in length. The female eastern indigo snakes has the ability to retain live sperm for long periods, potentially over 4 years. Thus, the female is able to choose when to release the sperm to fertilize the eggs. Mating season is at a peak from November to January but can occur from October through March. This occurs while the snakes are in their sandhill habitats.

Captivity and care

Due to its generally docile nature and appearance, some people find the eastern indigo snake to be a desirable pet, although its protected status can make owning one, depending on location, illegal without a permit. Only a few states require permits to own an eastern indigo snake, but a federal permit is required to buy one from out of state anywhere in the US. The permit costs $100; information about obtaining one can be found by doing a web search. Most states allow unrestricted in-state sales. To thrive in captivity, this snake requires a larger enclosure than most species do, preferably with something to climb on.

A study by Emily C. Lynch aimed to determine the ideal conditions for Indigo Snakes kept in captivity found that snakes with access to florescent light and unchanging behavioral enrichment items had the lowest stress levels and maintained the highest activity levels. Snakes that had rotating enrichment items had higher stress levels than those with unchanging environments. Snakes kept in these conditions took less time to emerge from their hide, spent more time basking, and had lower levels of stress hormones in their feces.

One notable owner of a pet eastern indigo snake was gonzo journalist Hunter S. Thompson during the time he wrote his Hell's Angels book. One evening, about 1966<!-- maybe 1967; terminus ante quem is Cardinal Spellman's death in December 1967 -->, he left his snake — with a mouse to eat — in a cardboard box in the Random House editor's office, but the mouse gnawed through the box and both animals escaped. The snake was subsequently beaten to death by the night watchman, which still caused Thompson great anguish several years later, and was his justification for sending his — often excessive — room service bills to Random House.

Sources

References

Further reading

  • Conant, Roger; Bridges, William (1939). What Snake Is That?: A Field Guide to the Snakes of the United States East of the Rocky Mountains. (With 108 drawings by Edmond Malnate). New York and London: D. Appleton-Century Company. Frontispiece map + 163 pp. + Plates A–C, 1–32. (Drymarchon corais couperi, pp.&nbsp;63–65 + Plate 10, figure 27).
  • Goin, Coleman J.; Goin, Olive B.; Zug, George R. (1978). Introduction to Herpetology, Third Edition. San Francisco: W.H. Freeman. xi + 378 pp. . (Drymarchon corais, p.&nbsp;117; Drymarchon corais couperi, pp.&nbsp;124, 308, Figure 16–1).
  • Holbrook JE (1842). North American Herpetology; or, A Description of the Reptiles Inhabiting the United States. Vol. III. Philadelphia: J. Dobson. 122 pp. (Coluber couperi, new species, pp.&nbsp;75–77 & Plate 16).
  • Morris, Percy A. (1948). Boy's Book of Snakes: How to Recognize and Understand Them. (A volume of the Humanizing Science Series, edited by Jaques Cattell). New York: Ronald Press. viii + 185 pp. (Drymarchon corais couperi, pp.&nbsp;34–36, 179).
  • Powell R, Conant R, Collins JT (2016). Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America, Fourth Edition. Boston and New York: Houghton Mifflin Harcourt. xiv + 494 pp., 47 plates, 207 Figures. . (Drymarchon couperi, p.&nbsp;373 + Plate 33 + Figure 158).
  • Smith, Hobart M.; Brodie, Edmund D. Jr. (1982). Reptiles of North America: A Guide to Field Identification. New York: Golden Press. 240 pp. (paperback), (hard cover). (Drymarchon corais couperi, pp.&nbsp;188–189).
  • Zim HS, Smith HM (1956). Reptiles and Amphibians: A Guide to Familiar American Species: A Golden Nature Guide. New York: Simon and Schuster. 160 pp. (Drymarchon corais, pp.&nbsp;94, 156).
  • Conservation Management Institute: Eastern Indigo Snake
  • Encyclopædia Britannica Online: Indigo Snake
  • 2018 Species Status Assessment Report (pdf)