Eastern indigo snake females use pheromones to attract males. Some researchers take advantage of this method of communication to attract males and capture them for research.
Communication Channels: visual ; tactile ; chemical
Perception Channels: visual ; tactile ; vibrations ; chemical
Humans are an important threat to eastern indigo snakes. At adult size they have few natural predators, but smaller or younger snakes may be taken by larger predators, such as large hawks. If eastern indigo snakes are threatened, they will first try to retreat quickly. If retreat is not possible, these snakes will display intimidating behavior when confronted by a potential threat. These behaviors include flattening their heads, hissing, and vibrating their tails. However, they rarely bite humans. Eastern indigo snakes protect themselves by hiding in burrows and by behaving cryptically. Their coloration may also help to protect them somewhat.
Known Predators:
Anti-predator Adaptations: cryptic
Eastern indigo snakes are the largest snakes in the United States and the largest, non-venomous snakes in the southeastern United States. Eastern indigo snakes are uniformly black with the exception of a red or cream colored area on the chin, throat, and, occasionally, the cheeks. The scales are smooth and large, typically with 17 scale rows at the mid body. Adults typical reach between 157.2 and 213.36 cm long. The record, however, is 280.4 cm long. Eastern indigo snakes are sexually dimorphic, with males growing longer than females. Eastern indigo snake young are similar in appearance, with the exception of a white band around their body. These snakes are commonly confused with with racers. Racers differ from eastern indigo snakes in several aspects: racers are rarely over 121.9 cm long, they are often thinner and have a dull black coloration with white or brown throats.
Range mass: 14 to 30 g.
Average mass: 24 g.
Range length: 152.4 to 213.36 cm.
Average length: 174.7 cm.
Other Physical Features: heterothermic
Sexual Dimorphism: male larger
The average lifespan of a wild eastern indigo snake is commonly 17 years. However, they can survive up to 21 years in the wild. The longest living indigo snake lived in captivity for 25 years and 11 months.
Range lifespan
Status: wild: 12 to 21 years.
Average lifespan
Status: wild: 17 years.
Range lifespan
Status: captivity: 16 to 25 years.
Average lifespan
Status: captivity: 23 years.
Typical lifespan
Status: wild: 15 to 21 years.
Average lifespan
Status: wild: 17 years.
Typical lifespan
Status: captivity: 16 to 25 years.
Average lifespan
Status: captivity: 23 years.
Eastern indigo snakes can be found in a variety of environments including pine and scrubby flatwoods, high pine, dry prairie, tropical hardwood hammocks, edges of freshwater marshes, agricultural fields, coastal dunes, and human-altered habitats. These snakes thrive more in wetland environments, as opposed to xeric conditions. Often eastern indigo snakes can be found living in the same habitat as gopher tortoises. Eastern indigo snakes use gopher tortoise burrows for shelter in the xeric habitats where gopher tortoises are found. In more moist habitats, eastern indigo snakes take shelter in hollowed root channels, hollow logs, or the burrows of rodents, armadillos, or land crabs. One study (Smith 1987) concluded that eastern indigo snakes live in different habitats throughout the year and at different stages of their lives. For example, adults and juveniles use different burrow habitats.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: desert or dune ; savanna or grassland ; forest ; scrub forest
Wetlands: marsh
Other Habitat Features: agricultural
Eastern indigo snakes are most common in Florida and the southern regions of Georgia, although they used to occur throughout much of Alabama, Texas, and South Carolina, as well. Populations in those areas have largely been lost due to habitat destruction, poaching, and killing of these snakes.
Biogeographic Regions: nearctic (Native )
Eastern indigo snakes consume a variety of food sources. They have one of the most varied diets of any snake. Eastern indigo snakes eat mammals, frogs, lizards, fish, eggs, birds, and other snakes, including venomous snakes. Eastern indigo snakes are immune to the venom of sympatric species of venomous snakes. Interestingly, they are one of the only snakes known to eat young turtles. Like other snakes, they typical eat their prey while it is still living. However there has been recorded cases of an eastern indigo snake beating prey against a nearby object to kill it. Eastern indigo snakes do not constrict their prey, they typically overpower it until the prey is exhausted to the point at which it can't escape, sometimes immobilizing the prey by pressing it to the ground. Their powerful jaws are used to grasp and pin down their prey until it can be ingested.
Animal Foods: birds; mammals; amphibians; reptiles; fish; eggs
Primary Diet: carnivore (Eats terrestrial vertebrates, Piscivore , Eats eggs)
Eastern indigo snakes occupy abandoned gopher tortoise burrows, where they seek protection and reproduce. After eastern indigo snake young hatch, they may remain in the nest for a day or two before dispersing. Eastern indigo snakes also help control populations of rodents and other snakes, including venomous snakes, in their home range.
Mutualist Species:
Eastern indigo snakes were commonly used in the pet trade before this became illegal. They were prized in the pet trade for their docile nature and hardiness. Currently, some are bred in captivity as pets but keeping eastern indigo snakes is regulated and permits are required. Now though, to keep an indigo snake in a one's possession one must have a permit or it is illegal. Eastern indigo snakes are important predators of rodents and venomous snakes, which helps to regulate populations of these potentially harmful animals. Eastern indigo snakes are not aggressive and often live near humans without any negative interactions, aside from human persecution resulting from misunderstanding about snakes and their important ecological roles.
Positive Impacts: controls pest population
Eastern indigo snakes are not a threat to humans. Their status as endangered species sometimes interferes with construction projects.
Eastern indigo snakes are sexually dimorphic in growth as well. Males grow to larger sizes and females may halt growth to focus their energy on maintaining the production of eggs. Growth rates are higher in younger individuals.
Humans present that greatest threat to eastern indigo snakes. Appropriate habitat is destroyed during roadway and housing construction and logging and agricultural activities. Domesticated animals and pesticides also negatively affect populations. Eastern indigo snakes are sometimes accidentally gassed in their burrows by rattlesnake poachers and they were frequently and illegally taken from their natural habitats and sold as pets. Eastern indigo snakes were placed on the U.S. endangered species list in 1971. Since then, they have been protected by the United States Fish and Wildlife Service and the Florida Fish and Wildlife Conservation Commission. Under this protection, it is illegal to possess, harm or harass eastern indigo snakes and permits are required to keep or transport them. Several adult snakes have been returned to sandhill regions and are being monitored for conservation research purposes. Populations remain threatened.
US Federal List: endangered
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Female eastern indigo snakes signal their readiness to mate by producing pheromones. When the scent is picked up by a male indigo snake, they track down the scent until they come into contact with the female. If other males are present, they will typically engage in ritual combat dances. During these dances, both males will intertwine their bodies and try to force the other's head to the ground. The winner mates with the female. Eastern indigo snakes have a polygynandrous mating system; males and females have multiple mates.
Mating System: polygynandrous (promiscuous)
In northern Florida, where most research on reproduction cycles has been conducted, the breeding season is from November to April. Females deposit their eggs from May to June. Females lay from 4 to 12 eggs, usually in vacated animal burrows, such as those of gopher tortoises, fallen logs, or some other sheltered burrow. Young hatch in about 3 months, usually in August and September. The breeding season may be extended in parts of south central Florida. Some researchers suggest that can store sperm and delay fertilization, but this idea has yet to be supported by evidence.
Breeding interval: Eastern indigo snakes breed once a year.
Breeding season: Eastern indigo snakes mate from November to April and lay eggs in May and June.
Range number of offspring: 4 to 12.
Average number of offspring: 7.
Average age at sexual or reproductive maturity (female): 3-4 years.
Average age at sexual or reproductive maturity (male): 3-4 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; oviparous
Eastern indigo snake hatchlings are born at an average size of 30.48 cm long. They grow rapidly and often reach adult size in 2 to 3 years. Eastern indigo snake females invest in young through supplying the egg and finding a safe place to lay their eggs. There is no further parental investment.
Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
Foster et al. (2000) studied the parasites of 21 Eastern Indigo Snakes in Florida, identifying 19 different parasites that included 2 species of trematodes, 3 cestodes, 10 nematodes, 2 acanthocephalans, 1 pentastomid, and 1 tick.
Hyslop et al. (2009) and others have found that Eastern Indigo Snakes are often associated with the burrows of Gopher Tortoises (Gopherus polyphemus).
When cornered, the Eastern Indigo Snake flattens its neck vertically (not horizontally as in the hognose snakes), hisses, and vibrates its tail, producing a rattling sound. When caught, it seldom attempts to bite. Captive Eastern Indigo Snakes are usually restless and keep on the move when handled. (Conant and Collins 1991)
The Eastern Indigo Snake (Drymarchon couperi) is a large shiny bluish black snake, sometimes with chin, throat, and sides of head with cream, reddish, or orange brown. It is the largest North American snake, reaching about 150 to 210 cm (record 263 cm). The scales are normally smooth, but some males, especially larger individuals, have faintly keeled scales on as many as five middorsal rows, starting at about the second quarter of the body; the anal plate is undivided. The third from last upper labial is wedge-shaped and cut off above by contact between adjacent labials. Young are like adults, but often with much more reddish on head and forward part of belly, 43 to 66 cm at hatching. (Behler 1979; Conant and Collins 1991)
The current stronghold for this threatened species is southeastern Georgia and peninsular Florida. It persists in lower numbers in Florida's panhandle, but is functionally extinct in Alabama and Mississippi. (USFWS 2008)
The Eastern Indigo Snake (Drymarchon couperi) is found in the eastern United States from southeastern Georgia, peninsular Florida and the lower Keys west to southeastern Mississippi; it was apparently released outside its native range in extreme southern Mississippi by governmental agencies (Conant and Collins 1991). Historically, this species occurred throughout Florida and in the coastal plain of Georgia, Alabama, and Mississippi (USFWS 2008 and references therein).
Home range estimates for Eastern Indigo Snakes in peninsular Florida ranged from 1.9 to 150 hectares for females and 1.6 to 327 hectares for males. Summer home ranges tend to be much larger than winter home ranges. A recent telemetry study in Georgia estimated home ranges of 35 to 354 hectares for females and 140 to 1530 hectares for males. Especially in fall and winter, Eastern Indigo Snakes are often associated with Gopher Tortoise burrows. These snakes seem to avoid paved roads, urban areas, and deciduous forest. Eastern Indigo Snakes exhibit a homing instinct and may return annually to previously used winter dens. (USFWS 2008 and references therein)
The Eastern Indigo Snake is found in pine woods, turkey oak, and palmetto stands near water, orange groves, and tropical hammocks (Behler 1979). It occurs mainly in large, unsettled areas (Conant and Collins 1991). Based on their work with Eastern Indigo Snakes in southeastern Georgia, Hyslop et al. (2009) suggest that availability of Gopher Tortoise (Gopherus polyphemus) burrows, which are used by the snakes as shelters, may be a limiting factor for the Eastern Indigo Snake in the northern part of its range (see also, e.g., Stevenson et al. 2003).
In a study in Georgia, Indigo Snake populations were typically associated with deep, excessively drained sandy soils on sand ridges along major coastal plain streams; winter sightings occurred almost exclusively on sandhills and in association with Gopher Tortoises (Diemer and Speake 1983).
The Eastern Indigo Snake was listed as threatened under the U.S. Endangered Species Act in 1978 (Federal Register, 43 FR 4026-4029).
The Eastern Indigo Snake is long-lived; one captive individual lived nearly 26 years (Behler 1979).
All other plain black snakes within the range of the Eastern Indigo Snake have keeled scales, a divided anal plate, or both (Conant and Collins 1991).
Because of their large home ranges and other behavioral traits, it is estimated that maintaining a viable population of Eastern Indigo Snakes requires at least 1000 hectares. The lack of reliable survey methods for this snake has made it difficult to obtain basic demographic and trend data and carry out effective conservation planning. One intriguing possibility that has shown at least some promise for locating Indigo snakes has been training dogs to track them. (USFWS 2008 and references therein)
Although development has been generally extremely harmful to the Eastern Indigo Snake, in south Florida, agricultural sites such as sugar cane fields and canal banks through citrus groves created in former wetland areas are occupied by Eastern Indigo Snakes. Historically, these snakes would have occupied only higher elevation sites within the wetlands. Agriculture and its associated canal systems, however, have brought increased numbers of rodents and other snake species that are eaten by Eastern Indigos, resulting in higher densities of Eastern Indigo Snakes in these areas than would have been present in the past. Efforts to restore natural wetlands in some of these areas may actually reduce resident populations of Eastern Indigo Snakes. (USFWS 2008)
Current efforts to secure the future of the Eastern Indigo Snake are focused on land acquisition, captive breeding snakes to establish new populations in the wild, and habitat management (USFWS 2008).
The Eastern Indigo Snake mates from November to February. It deposits 5 to 12 leathery eggs, 76 to 102 mm long, in April or May. Hatchlings appear in late July to October. (Behler 1979)
Sexual maturity is reached at about 1.5 meters in length. Two captive females bred at 40 and 41 months of age. Average clutch size of 20 females removed from the wild and laying eggs the following spring was 9.4 eggs. In captivity, Eastern Indigo Snakes typically lay eggs every year. (USFWS 2008 and references therein)
Although at the time it was listed as a federally threatened species the Eastern Indigo Snake was treated as a subspecies, Drymarchon corais couperi, it is now accepted as a full species, Drymarchon couperi (USFWS 2008 and references therein).
Loss of native habitat supporting Eastern Indigo Snakes is ongoing as a result of development and urbanization. Habitat loss is especially problematic for this species because of its relatively large home range. (USFWS 2008)
The diet of the Indigo Snake includes small mammals, birds, frogs, snakes (including even cottonmouths and rattlenakes), lizards, and young turtles. The Indigo Snake is not a constrictor, instead immobilizing food with its jaws. (Behler 1979; Conant and Collins 1991)
Although the diet consists mainly of vertebrates, based on a single record Rossi and Lewis (1994) suggested that in some microhabitats Philomycus slugs could be an important food source for hatchling and juvenile Eastern Indigo Snakes.
The eastern indigo snake (Drymarchon couperi) is a species of large, non-venomous snake in the family Colubridae. Native to the southeastern United States, it is the longest native snake species in the country.[5]
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.
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 (1794-1866).[6] Couper brought Holbrook the type specimen from south of the Altamaha River in Wayne County, Georgia.
The eastern indigo snake has a number of common names including indigo snake, blue indigo snake, black snake, blue gopher snake, and blue bull snake.
The eastern indigo snake has uniform 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.[5] The longest recorded specimen measured 2.8 m (9.2 ft) in total length (including tail). Unlike many snakes, mature male indigo snakes are slightly larger than females. This is thought to be due to intraspecies competition and combat with the males.[7] A typical mature male measures 1.2–2.36 m (3.9–7.7 ft) in total length, with a reported average of 1.58 m (5.2 ft), and weighs 0.72–4.5 kg (1.6–9.9 lb), reportedly averaging 2.2 kg (4.9 lb). Meanwhile, a mature female typically measures around 1.1–2 m (3.6–6.6 ft) in total length, averaging 1.38 m (4.5 ft), and weighs 0.55–2.7 kg (1.2–6.0 lb), averaging 1.5 kg (3.3 lb).[8][9] Specimens over 2.6 m (8.5 ft) can weigh up to 5 kg (11 lb).[10] 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.[11]
The eastern indigo snake inhabits areas from far southwestern South Carolina through Florida, and west to southern Alabama and southeastern Mississippi. Their historic range extended into Louisiana.[12] A related species, the Texas indigo snake (Drymarchon melanurus erebennus), is found in southern Texas and Mexico.[13]
Because of habitat loss, the eastern indigo snake is listed as a federally threatened species in Georgia and Florida.[14] In 2012 the Alabama Department of Conservation and Natural Resources had listed the species as possibly extirpated within the state.[15] A reintroduction program has shown initial signs of success, with an individual sighted in March 2022.[16]
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. The eastern indigo snake 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, and another 15 (10 female and 5 male) in 2019. The 10-year program is a collaborative effort between the Florida Wildlife Commission and private partners.[17]
NatureServe considers the species to be Vulnerable.[18]
Another issue the eastern indigo snake is facing would be dealing with infections due to the snake fungal disease (Ophidiomyces ophiodiicola).[19] This fungus infects the dermal layer of snake skin, causing a variety of lesions that commonly manifest on the head and near the vent. [20]
The eastern indigo snake frequents flatwoods, hammocks, dry glades, stream bottoms, cane fields, riparian thickets, and high ground with well-drained, sandy soils.[13] In Georgia, the eastern indigo snake prefers excessively drained, deep sandy soils along major streams, as well as xeric sandridge habitats.[21][22] In the northern parts range is restricted to sandhills and require Gopher Tortoise burrows during colder seasons [23] Xeric slash pine plantations seem to be preferred over undisturbed longleaf pine habitats.[24] Habitat selection varies seasonally. From December to April, eastern indigo snakes prefer sandhill habitats; from May to July the snakes shift from winter dens to summer territories; from August through November they are located more frequently in shady creek bottoms than during other seasons.[25] In a study in Georgia, winter sightings generally occurred on sandhills, in association with gopher tortoise (Gopherus polyphemus) burrows.[26] These burrows can be used as cover from predators, fires, or extreme temperatures that may come through the area.[27]
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.[21]
Because the cover requirements of eastern indigo snakes change seasonally, maintaining corridors that link the different habitats used is important. From the spring through fall snakes must be able to travel from sandhill communities and upland pine-hardwood communities to creek bottoms and agricultural fields.[25] In winter, indigo snakes den in gopher tortoise burrows, which are usually found in open pine forests with dense herbaceous understories.[24] Burrows need to be in areas where there is no flooding. Eastern indigo snakes heavily use debris piles left from site-preparation operations on tree plantations.[24] These piles are often destroyed for cosmetic reasons but should be left intact because they provide important hiding cover for both the snake and its prey. Summer home ranges for the indigo snake can be as large as 273 acres (110 hectares).[25]
The eastern indigo snake is carnivorous, like all snakes, and will eat 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.[28] 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.[29] 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 turtles, lizards, frogs, toads, fish, a variety of small birds and mammals, and eggs.[13][24][30]
As defensive behavior the eastern indigo snake vertically flattens its neck, hisses, and vibrates its tail. If picked up, it seldom bites.[31]
It often will cohabit with gopher tortoises in their burrows, although it will settle for armadillo holes, hollow logs, and debris piles when gopher tortoise burrows can't be found. Hunters, hoping to flush out rattlesnakes, often wind up accidentally killing 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.
As an apex predator, indigo snakes have no natural predators. Instead, humans represent the biggest threat to the eastern indigo snake. Highway fatalities, wanton killings, and overcollection for the pet trade adversely affect indigo snake populations. Snakes are taken illegally from the wild for the pet trade. Eastern indigo snakes are sometimes "gassed" in their burrows by rattlesnake hunters.[21] Along with infrastructure and pet trade, indigo snake populations are drastically declining due to habitat fragmentation. The eastern indigo snake's decline is correlated with the gopher tortoise decline as well since they utilize their burrows for hibernation.
The eastern indigo snake is oviparous.[32] The eggs are 75–100 mm (3–4 in) long by 27–32 millimetres (1–1+1⁄4 in) wide. Females will lay a single clutch of 4-14 eggs from late April through early June.[33] The hatchlings are 600–700 millimetres (23+1⁄2–27+1⁄2 in) long.[34] Eastern indigo snakes are often referred to as late maturing colubrids; they usually do not reach maturity until they are 3 to 5 years old and around 5 to 6 feet in length. Female eastern indigo snakes have the ability to retain live sperm for long periods, potentially over 4 years. Thus, females are able to choose when to release the sperm to fertilize the eggs.[35] Mating season is at a peak from November to January but can occur from October through March.[36]
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.
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, 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.[37]
This article incorporates public domain material from Drymarchon couperi . United States Department of Agriculture.
The eastern indigo snake (Drymarchon couperi) is a species of large, non-venomous snake in the family Colubridae. Native to the southeastern United States, it is the longest native snake species in the country.
Eastern indigo
