Eastern Indigo Snake

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.

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 (1794–1866). 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. The longest recorded specimen measured 2.8 m (9.2 ft) in total length (tail included). Unlike many snakes, mature male indigo snakes are slightly larger than females. This is thought to be due to intraspecies competition and combat among males. 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). 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 1.1–2 m (3.6–6.6 ft) in total length, averaging 1.38 m (4.5 ft), and weigh 0.55–2.7 kg (1.2–6.0 lb), averaging 1.5 kg (3.3 lb). Specimens over 2.6 m (8.5 ft) can weigh up to 5 kg (11 lb). 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. A related species, the Texas indigo snake (Drymarchon melanurus erebennus), is found in southern Texas and Mexico.

Conservation status