Reptiles

Rainbow Snake

Farancia erytrogramma · also called rainbow snake, eel moccasin

Least Concern → carnivore Rivers & wetlands Coasts & shorelines

A rainbow snake can reach a metre and a half, flash an iridescent sheen off glossy blue-black scales striped in red, and live in the same southeastern rivers for years without a single person noticing. It hunts almost nothing but American eels, it is docile to the point of barely defending itself, and even herpetologists who study it for a career can go years without finding one.

Overview

The rainbow snake, Farancia erytrogramma, is a large, non-venomous, iridescent snake of clean coastal-plain rivers, streams, and swamps in the southeastern United States. It is an extreme dietary specialist, hunting almost exclusively American eels at night, working down prey that is nearly as long and far more muscular than most snakes would attempt.

Hidden by design

Highly aquatic, nocturnal, and a burrower by day, the rainbow snake is one of the least-seen large snakes in its range, found mostly by accident during fish surveys. It shares with the mud snake a hard tail-tip spine it presses against a threat — harmless, but likely the origin of the American hoop snake legend. Despite its size it is famously docile, rarely biting even when handled.

Tied to the eel

Because it depends so completely on the American eel, which migrates to the Sargasso Sea to breed, the snake’s fortunes are indirectly tied to dams and other barriers that block eel migration — a threat that could hit the snake without ever touching its own wetland habitat.

Status

Least Concern but poorly surveyed, given how hard it is to find. An isolated south Florida population went unconfirmed for decades and was considered possibly gone — a reminder of how easily a species this secretive can be lost unnoticed.

Rainbow Snake: common questions

Is a rainbow snake venomous or dangerous?

No. The rainbow snake has no venom and is remarkably docile, rarely if ever attempting to bite even when caught and handled. Its only real defences are burrowing away to escape, hiding its head within its coiled body, and pressing the small hardened spine at the tip of its tail against a predator or handler, a harmless action sometimes mistaken by startled people for a sting. Despite its impressive size and striking colours, it poses no danger to people and is regarded by herpetologists as one of the gentlest large North American snakes.

Why does the rainbow snake only eat eels?

Its entire hunting behaviour and even aspects of its jaw and throat appear adapted specifically for subduing and swallowing American eels, long, extremely strong, slippery fish that would be difficult prey for most snakes. This narrow specialisation likely evolved because eels are abundant in the same clean coastal rivers and swamps the snake inhabits, and by focusing on one demanding but locally plentiful prey type, the rainbow snake avoids competing directly with the many more generalist snakes and other predators sharing its wetland habitat.

Why is the rainbow snake so rarely seen?

A combination of habits keeps it hidden even from experienced snake hunters. It is highly aquatic, spending most of its time in or under water rather than basking or moving overland, it is active mainly at night, and by day it burrows into mud, sand, or dense vegetation at the water's edge rather than resting somewhere visible. Because its main prey, the American eel, is itself often active at night in the same habitat, the rainbow snake's schedule and hiding habits line up closely with staying out of sight, and most confirmed sightings come from incidental captures, such as during fish surveys, rather than from deliberate searching.

What is the connection between the rainbow snake and the hoop snake legend?

The rainbow snake, like its close relative the mud snake, has a small hardened spine at the tip of its tail that it presses against anything holding it, and this harmless behaviour is one of the leading explanations for the American folk tale of the hoop snake, a mythical creature said to bite its own tail, roll after victims like a wheel, and kill with a venomous tail sting. No snake can actually do any of that, but early observers who saw a real Farancia snake jabbing with its odd tail spine, and who already knew the hoop snake story, may have concluded they were seeing the legendary creature in action.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 11, 2026. Last updated September 11, 2026.

Quick facts

Scientific name: Farancia erytrogramma
Diet: Overwhelmingly the American eel, hunted in rivers, streams, and swamps at night, along with occasional salamanders, tadpoles, and fish, with the snake seizing and working down a slippery, powerfully muscled eel that can be nearly as long as the snake itself
Iridescent colours: The rainbow snake has a glossy blue-black back with three narrow red or pink stripes running its length, a bright red or yellow belly marked with rows of black spots, and in good light the smooth scales flash an iridescent sheen, giving the snake its name
Almost never seen: Despite reaching up to about 1.5 metres and being locally common in the right habitat, the rainbow snake is so aquatic, nocturnal, and burrowing that it is one of the least frequently encountered large snakes in the southeastern United States, and many herpetologists who have worked in its range for years have never found one
The tail spine: Like its close relative the mud snake, a rainbow snake has a small, hard, pointed scale at the tip of its tail that it presses or pokes against a predator or a handler, a harmless defensive tactic that, along with the mud snake's, is thought to be the origin of the American hoop snake legend
A gentle giant of the swamp: Despite its size, the rainbow snake is remarkably docile and almost never bites in defence, relying instead on burrowing away into mud and vegetation, hiding its head in its coils, and using the harmless tail spine, making it one of the calmest large snakes to encounter
Tied to clean water and eels: Because it depends so heavily on the American eel, the rainbow snake's fortunes are tied to the health of the rivers those eels use, and eels themselves migrate to and from the Sargasso Sea to breed, so anything that blocks that migration, such as dams, indirectly affects the snake's food supply
Large clutches, secretive nests: Female rainbow snakes lay clutches of roughly 20 to 50 eggs in a hidden, moist site such as a rotting log, sandy bank, or burrow, and, unusually for a snake, the female may remain coiled near the eggs, though the extent of any guarding behaviour is not fully documented given how rarely nests are found
Range: The coastal plain of the southeastern United States, from southern Maryland and Virginia south through the Carolinas, Georgia, and Florida and west along the Gulf coast to Louisiana, in clean, well-vegetated rivers, streams, spring runs, swamps, and marshes with sandy or muddy bottoms, generally staying within or very close to permanent water.
Conservation status: Least Concern → ≈ The rainbow snake is widespread across the southeastern United States coastal plain and is assessed as Least Concern, though its extremely secretive habits make it difficult to survey and its true status in many areas is poorly known. Because it depends heavily on the American eel, an animal that has itself declined across much of its range due to dams blocking migration, habitat loss, and overharvesting of young eels, the rainbow snake could be affected indirectly by any long-term eel decline, even where the snake's own wetland habitat remains intact. One isolated population in south Florida had not been confirmed for decades and was considered possibly extirpated, illustrating how easily a population of such a hard-to-find snake can be lost without anyone noticing in the wild