Reptiles of North Carolina
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NC Records

Farancia erytrogramma - Rainbow Snake


Photo: FKW
Photo: K. Bischof, S. Becker
Taxonomy
Class: Reptilia Order: Serpentes Family: COLUBRIDAE Subfamily: Dipsadinae
Taxonomic Comments: Farancia consists of two species of secretive, mid-to-large bodied aquatic dipsadine snakes endemic to the southeastern United States (Gulf of Mexico and Atlantic Coast). No comprehensive molecular phylogeny of the genus has been completed. The taxonomy of F. erytrogramma has been stable since the mid-1950s (see Neill [1964] for further reading).
Species Comments: Farancia erytrogramma, the Rainbow Snake, is one of two members of the genus found in North Carolina. It is found primarily in the southeastern United States, ranging from Louisiana east to the Atlantic coast, and north to northeast Virginia and southern Maryland. In North Carolina, it is known primarily from the Coastal Plain and Sandhills.

Two subspecies were traditionally recognized based on differences in color and pattern: F. e. erytrogramma (the common rainbow snake), which comprises the majority of the species's range (including North Carolina); and F. e. seminola (the southern Florida rainbow snake) known from only three specimens collected in southern Florida between 1949-1952 and now presumed extinct.

The generic epithet Farancia is a New Latin coined name with apparently no meaning. The specific epithet erytrogramma is a combination of the Greek erythros ("red") and gramma (meaning a letter, picture, marking, or line as in writing), in reference to the red dorsal stripes of the species.

Taxonomic References: Neill (1964); Mitchell (1982a, 1982b).
Identification
Description: Rainbow Snakes are among North Carolina's most recognizable species. They are large snakes with thick, glossy bodies and wedge-shaped heads approximately as wide as the neck. Their dorsum is glossy black, sometimes violet/violet-blue, with three red longitudinal stripes. The middorsal stripe extends to the base of the tail, and the first few scale rows are often bicolored, yellow and red. The top of the head is primarily black, while the labials, mental, and underside are often yellow-orange; these typically have an central dark spot. The ventral scutes are typically reddish, with prominent lateral black spots forming broken lines running the length of the venter. Some specimens have less prominent midventral spots as well. Hatchlings are similarly patterned as adults.

Generally, males have more ventral spotting with less subcaudal spotting than females, but this is not always a reliable character (Gibbons et al., 1977; Palmer and Braswell, 1995).
Morphological Features: Rainbow Snakes typically have 19 smooth scale rows at midbody. Ventral counts range from 155-182 (NC specimens: 155-177; Palmer and Braswell, 1995), with 34-50 subcaudals and a divided anal plate. The tail ends in a noticably conical spine. Head scale counts are typically as follows: 7 supralabials, 7-8 infralabials, 1 nasal, 2 internasals, 1 loreal, 0 preoculars, 2 postoculars, and 1+2 temporals. Palmer and Braswell (1995) noted some variation in scalation across multiple specimens in NC.

These are fairly large snakes, with a maximum reported total length of 173.3 cm (68.2 inches). Tail lengths range from 10-19% of total length. Like the closely related mudsnake (Farancia abacura), females reach larger size than males, have smaller tail lengths relative to body, and average more ventral scales and fewer subcaudal scales. Males are smaller on average but with longer tails relative to body length, meaning fewer ventrals and more subcaudals. Either sex may exhibit anal ridges on the body scales near the anal plate (typically more pronounced in males), but females typically do not show reduction in posterior dorsal scale rows (retaining 19 the length of the body) while males often show reduction to 18 or 17 scale rows.

Rainbow Snakes have enlarged posterior teeth and a Duvernoy's gland, but they are completely harmless to humans and pets, almost never attempting to bite. Whether they use a weak venom to capture prey is unknown. When captured, rainbow snakes may release musk or poke the tailspine into the collector, but despite southern folklore declaring the tail spine dangerous, it is entirely harmless and will not break skin.
Technical Reference: Gibbons et al. (1977); Mitchell (1982b); Palmer and Braswell (1995); Ernst and Ernst (2003).
Field Guide Descriptions: Beane et al. (2010).
Online Photos:    Google   iNaturalist   GBIF
Observation Methods: Passive trapping with partially-submerged minnow traps or larger "trashcan traps" can be effective at capturing foraging aquatic snakes, including F. erytrogramma (Luhring and Jennison, 2008; Durso et al., 2011 and references therein). Drift fences with pitfall traps enclosing bodies of water can also be effective (Gibbons et al., 1977).
Distribution in North Carolina
Distribution Comments: Rainbow Snakes are found in North Carolina in the eastern and southern Coastal Plain. They are known from the Outer Banks north of Oregon Inlet, and reach only into the eastern Piedmont. They are entirely absent from the western Piedmont and Mountains.
Distribution Reference: Palmer and Braswell (1995)
County Map: Clicking on a county returns the records for the species in that county.
Key Habitat Requirements
Habitat: Habitats used by Rainbow Snakes include rivers, lakes, and brackish and freshwater marshes (Palmer and Braswell, 1995). They also use canals and large ditches (Beane et al., 2010), although they may not be as partial to sluggish water sites with abundant aquatic vegetation as the Mudsnake.
Biotic Relationships: Rainbow snakes primarily predate American eels (Anguilla rostrata), as well as tadpoles and salamanders (Neill, 1964; Ernst and Ernst, 2003; Durso et al., 2013).

They are known prey of large frogs, ophiophagous snakes, and birds (Ernst and Ernst, 2003).
Life History and Autecology
Breeding and Courtship: More data is needed on sexual maturity in Rainbow Snakes, but it has been reported to be reached at total body lengths of 87.4 cm (male) and 88.6 cm (female) by Mitchell (1994). The mating period is not known, but nests occur in the summer (June-August).
Reproductive Mode: Rainbow Snakes are oviparous and lay eggs in the summer that hatch in the fall (September-October). Clutches have been reported to contain 10-52 eggs, all elongate, white with leathery shells, 3.1 x 2.0 cm average size (Palmer and Braswell, 1995).

Hatchlings are 17.9-22.8 cm in total length (Palmer and Braswell, 1995) and weigh 3.6-8.7 g (Ernst and Ernst, 2003).
Aquatic Life History: Rainbow Snakes are highly aquatic and seem to prefer larger streams and lakes rather than shallow, fresh or brackish water. Neill (1964) noted that they were rarely found in the same habitats as the closely related Mudsnakes, and Palmer and Braswell (1995) noted that the only areas of direct sympatry between these species in North Carolina are Lake Ellis (Craven Co.), Holts Lake (Johnston Co.), and Merchants Millpond (Gates Co.).
Terrestrial Life History: Rainbow Snakes are notoriously secretive, difficult to find, and seem to be relatively uncommon. They will disperse overland away from water, especially if local water sources are drying up, and are known to burrow in soggy soil and nest on land (Steen et al., 2013). They are primarily nocturnal, and have been recorded in North Carolina in every month; most records are from April to June.

Much remains to be learned about the natural history of this species. Home range estimates have not been reported.
General Ecology
Adverse Environmental Impacts
Interactions with Humans: Though primarily aquatic, Rainbow Snakes will move over land, and as such are occasionally killed on roads by motor vehicles (Steen et al., 2013).
Status in North Carolina
NHP State Rank: S3
Global Rank: G4
Status in North Carolina: SR

Photo Gallery for Farancia erytrogramma - Rainbow Snake

12 photos are shown.

Recorded by: Angie Shipp-Pennock
New Hanover Co.
Comment: 		Recorded by: W. Morris, E. Staib
Wayne Co.
Comment:
Recorded by: B. Bockhahn, B. Herman, hundreds of kids
Robeson Co.
Comment: 		Recorded by: D. Crilley, T. Walters
Robeson Co.
Comment:
Recorded by: C Rose
Beaufort Co.
Comment: 		Recorded by: N. Crider
Beaufort Co.
Comment:
Recorded by: j.wyche
Gates Co.
Comment: 		Recorded by: Tommy Lynn Walters and John Privette
Robeson Co.
Comment:
Recorded by: K. Bischof, S. Becker
Beaufort Co.
Comment: 		Recorded by: K. Bischof, S. Becker
Beaufort Co.
Comment:
Recorded by: Justin Miller and Tommy Lynn Walters
Robeson Co.
Comment: 		Recorded by: FKW
Gates Co.
Comment: