Secrets of Rainbows and Muds

By DIRK J. STEVENSON. Rainbow snake (above). Photo credit: Kevin M. Stohlgren.

As dusk gathers a large blue-black snake, as dark as the water flowing over her, rearranges her coils among the spidery roots of a giant cypress. A night heron lands awkwardly on a nearby cypress knee, reconsiders, takes off, then returns. Current swirls around the massive tree trunk as fluttery treefrog whistles fill the air. The snake waits. The water moves. She straightens her muscular form, striped vivid red, and swims slowly. She rises. Breathes. Waits. Her tongue flicks, tasting the water, finding molecules of eel. A final breath and she swims with grace along the bottom and into deeper water. The hunt is on. 

Farancia is the genus for mud and rainbow snakes – arguably among North America’s prettiest, oddest and hardest to find snakes. These species are stout and large, yet docile. Iridescent and supple. Primeval scales colored with striking reds, yellows and black. Bellies patterned with orange and salmon.

Mud snake hatchling . Photo credit: Kevin Enge

The eastern mud snake (Farancia abacura abacura) can reach 81.5 inches, nearly 7 feetlong. The common rainbow snake (Farancia erytrogramma erytrogramma) can grow to 5.5 feet, or 66 inches. Both are native to the Southeast’s Coastal Plain. The rainbow’s range wraps around the Gulf and Atlantic coasts from southeastern Louisiana to Virginia and Maryland. Mud snakes have a similar range, albeit with a western subspecies found as far north along the Mississippi River valley as southern Illinois and the Missouri Bootheel.

Zoologists Albert H. Wright and W.D. Funkhouser, from their experiences in the Okefenokee Swamp wilderness a century ago, nominated cypress snake and sphagnum snake as common names, ominously describing what we now call mud snakes as “decidedly inhabitants of the twilight parts of the swamp… in the dark, gloomy cypress ponds on the islands… or amongst dense vegetation of the deepest and most inaccessible regions.”

SPECIAL PREDATORS, SLIPPERY PREY

Exceptionally soggy conditions really bring these snakes out. Herpetologist Archie Carr wrote of seeing hundreds of mud snakes on a two-mile stretch of U.S. 441 south of Gainesville, Fla., following hurricane rains in 1941. Others documented more than 200 juvenile mud snakes run over on the same roadway after a hurricane in 1950.

The two-toed amphiuma is the preferred prey for the mud snake. Photo credit: Dirk Stevenson.

The hardened, pointed tail tip of mud and rainbow snakes has yielded colloquialisms like “horned snake” and “stinging snake.” The tip is presumably an adaptation for prodding their long and slimy prey into position for swallowing, and is incapable of puncturing human skin. While adult muds fancy eel-like salamanders called amphiumas, the primary prey of adult rainbows is the American eel, a catadromous fish. The snakes’ enlarged teeth on the rear of their upper jaw also helps dispatch and handle such slippery prey. Smaller snakes of either species also eat earthworms, small fish, salamanders, tadpoles and frogs.

Both species are oviparous (egg layers), nesting later (June into mid-July) than many other southern snakes. The incubation period is 60-80 days, and unlike the vast majority of North American snakes, female muds and rainbows (which grow much larger than males) remain with their eggs, leaving the nest only to eat, defecate or shed their skins. This attendance may confer some degree of protection and increase hatchling success, although neither has been substantiated. Mud snakes sometimes deposit their clutches within the mounds of vegetation and debris that comprise alligator nests.

Although clutches for rainbows and muds average two-to three-dozen eggs, there are exceptions. A 6.5-foot mud snake found near Valdosta laid 111 eggs (69 of which hatched), a record clutch for this species.

AT HOME IN WATER OR LAND

Muds and rainbows are highly aquatic. Muds typically inhabit swamps and other lentic (still-water) wetlands, while their striped kin are denizens of lotic – rapid-water – habitats such as rivers and connected waterways that support eel populations. Both leave the water to find nesting or overwintering sites, to move during droughts or to travel between foraging sites. Whit Gibbons and his colleagues at the Savannah River Ecology Lab discovered that hatchling rainbows may overwinter in or near their natal nests, moving to nearby wetland habitats the following spring.

Rainbow snake dining on an American eel along the Champney River in Darien, GA. Photo credit: Tim Keyes/Georgia DNR

Field surveys I conducted in xeric sandhills along the Canoochee River in south Georgia mirrored these observations. I caught five hatchling rainbows in April and  May at drift fences up to three-quarters of a mile from the river. Rainbows at the site would be preyed on by other snakes, including cottonmouth, harlequin coral snake, eastern indigo and eastern kingsnake, plus raptors, larger predatory fish, alligators and raccoons.

Observing and finding either Farancia species is never easy. By raking saturated muck, especially at dry-downs, I collected two yearling rainbows in the same week from tupelo swamps along the Altamaha River. Last year I hand-raked a yearling mud snake from a mucky, sphagnum-lined seepage.

Rainbows – often called eel moccasins – love spring runs. Though they are not confined to such cool, clear waterways, the calcareous waters of spring runs, in addition to being predictable lairs for big eels, are high-visibility habitats to explore. Herpetologist Wilfred T. Neill saw more eel moccasins in Georgia than anybody, and his 1964 article on the species is a classic in natural history (read a copy; requires free account). Neill and Archie Carr reported watching foraging rainbows swim along the bottom of runs 8-12 feet deep. Foraging rainbows are known to nose about under debris in the water and may stick their heads directly into the substrate.

Although mud snakes are locally common to abundant throughout much of their range, the conservation status of the rainbow snake is poorly known, in part due to the profound difficulty in finding the animal even where it’s common. Rainbows are rare, thought to be declining in some areas and listed and monitored by many state heritage programs within their range.

REPORT SIGHTINGS

Anyone who finds either species is encouraged to report the sighting, with photos (if possible) and location details, to Georgia DNR’s Wildlife Conservation Section, (478)-994-1438 or daniel.sollenberger@dnr.ga.gov.

Dirk J. Stevenson is a naturalist and owner of Altamaha Environmental Consulting in Hinesville. Part of this article first appeared in Herp Nation magazine.