Reptiles of North Carolina
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NC Records

Liodytes pygaea - Black Swampsnake


Photo: E. Hofmann
Photo: E. Hofmann
Taxonomy
Class: Reptilia Order: Serpentes Family: Colubridae Subfamily: Natricinae Synonym: Seminatrix pygaea Other Common Name(s): Black Swamp Snake
Taxonomic Comments: Liodytes, as currently considered, consists of three species of small to medium-sized semiaquatic snakes native to the southeastern United States.

Species Comments: Liodytes pygaea, the Black Swampsnake, is one of two Liodytes in North Carolina. This species is found in the southeastern United States from North Carolina to Florida, and west to the Florida Panhandle. In North Carolina, L. pygaea is restricted only to the eastern Coastal Plain, with its distribution limited essentially to coastal counties.

Some authors recognize three subspecies of Black Swampsnake; North Carolina populations can be assigned to L. p. paludis, the "Carolina Swampsnake". More complete molecular sampling is needed to determine if those subspecies correspond to discrete units.

Liodytes pygaea was previously placed in the genus "Seminatrix" for many years. McVay and Carstens (2013) revised the Thamnophiini tribe and resurrected Liodytes based on molecular phylogenetic support and taxonomic priority. However, results of a recent work by Nuñez et al. (2023) challenged this change. They suggested returning this species to the genus Seminatrix based on its placement as sister to other Liodytes and "notable phenotypic and ecological differences between the species" (8). For now, we will keep this species listed as Liodytes pygaea, pending broader acceptance of the taxonomic change.

The generic epithet Liodytes is derived from the Greek leios, "smooth", and dytes, "diver". The specific epithet pygaea is from the Greek pyge, meaning "the rump", apparently because of the shape of the posterior portion of the holotype.

Taxonomic References: Dowling (1950); Dorcas et al. (1998); McVay and Carstens (2013); Nuñez et al. (2023).
Identification
Description: Black Swampsnakes are small snakes with heads somewhat distinct from the neck. Their dorsum is glossy black to dark brown, with thin longitudinal lines on some lateral scales which superficially resemble keels. The venter is red to orange, with dark bars appearing on the lateral edges of the ventral scales. The mental area may be lighter brown to yellow, and greenish-yellow pigment may be seen on the labials.
Morphological Features: Black Swampsnakes have 17 smooth midbody scale rows. Ventral counts range from 112-141 (127-141 in NC specimens; Palmer and Braswell, 1995), with 35-56 subcaudals and a divided anal plate. Head scale counts are typically as follows: 8 supralabials, 9 infralabials, 1 loreal, 1 nasal, 1 preocular, 2 postoculars, and 1+2 temporals. Palmer and Braswell (1995) noted some variation in scalation across multiple specimens in NC.

Black Swampsnakes have a maximum recorded total length of 55.5 cm (21.8 inches). Palmer and Braswell (1995) reported a 48.9 cm female specimen from NC. Tail lengths account for approximately 15-25% of total length. Females reach larger sizes than males; males have longer tails and more subcaudals, as well as suranal keels.

Black Swampsnakes lack enlarged, grooved posterior teeth or Duvernoy's glands, meaning they are incapable of producing venom. If threatened,they tend to flee towards water. They rarely bite when handled, but may expel musk. They are harmless to humans and pets.
Technical Reference: Palmer and Braswell (1995); Ernst and Ernst (2003).
Field Guide Descriptions: Palmer and Braswell (1995); Ernst and Ernst (2003); Beane et al. (2010).
Online Photos:    Google   iNaturalist   GBIF
Observation Methods: Black Swampsnakes are secretive and difficult to sample. Aquatic sampling with naturally baited plastic minnow traps (Winne, 2005) may be most effective, though this species exhibits a high escape probability (Willson et al., 2005; Royal et al., 2023). They are occasionally found on roads at night, moving between bodies of water.
Distribution in North Carolina
Distribution Comments: Until recently, records of this species were restricted to counties bordering the ocean or sounds in the NC Coastal Plain. However, a recent inland specimen from the Sandhills was reported from Hoke Co. (Ball and Beane, 2023).
County Map: Clicking on a county returns the records for the species in that county.
Key Habitat Requirements
Habitat: Black Swampsnakes are associated with a variety of permanently flooded habitats in the Outer Coastal Plain, including ponds, swamps, streams, and canals, especially with abundant mats of sphagnum or floating or emergent vegetation (Palmer and Braswell, 1995; Beane et al., 2010).
Biotic Relationships: Black Swampsnakes forage aquatically and consume a variety of invertebrates and small vertebrates, in contrast to other closely related natricids (Liodytes rigida and Regina septemvittata) that primarily eat crayfish. Reported invertebrate prey of Black Swampsnakes include oligochaete earthworms and leeches. Vertebrates consumed include fish (including mosquitofish and sunfish), frogs and their tadpoles (including cricket frogs, tree frogs, true frogs, and toads), and salamanders (including larval Ambystoma opacum, Desmognathus fuscus, Eurycea quadridigitata, Plethodon cinereus, and dwarf sirens) (Palmer and Braswell, 1995; Ernst and Ersnt, 2003; Gibbons and Dorcas, 2004; Durso et al., 2013).

Reported predators of Black Swampsnakes include large fish (including largemouth bass), ophiophagous snakes (kingsnakes and coralsnakes), wading and predatory birds (including egrets, herons, ibises, hawks, and potentially bald eagles), and armadillos (Kean and Tuberville, 1995; Aycrigg et al., 1996; Ernst and Ernst, 2003; Gibbons and Dorcas, 2004; Durso and Rosenthal, 2016; Durso et al., 2017; Hofmann and Wilkinson, 2021).
Life History and Autecology
Breeding and Courtship: Detailed reproductive data, including size at sexual maturity, are lacking for Black Swampsnakes. Mating likely occurs in the spring and early summer.
Reproductive Mode: Black Swampsnakes are viviparous; young are typically born in late summer (July to October). Litters average 8 neonates; litter size is correlated with body size (Ernst and Ernst, 2003).

Neonates are approximately 14 cm in total length and weigh 1 g on average.
Aquatic Life History: Black Swampsnakes are highly aquatic, preferring areas with abundant aquatic vegetation such as cypress swamps, marshes, and slow-moving rivers; they will burrow into mats of aquatic vegetation. They are salt tolerant, and have been found in brackish waters and tidal marshes. Importantly, they seem highly susceptible to evaporative water loss compared to other sympatric natricids (Winne et al., 2001).
Terrestrial Life History: Black Swampsnakes are notoriously secretive and may be difficult to find even in areas of local abundance. They rarely venture far from water but have been found crossing roads between habitats or during heavy rains, or under mosses, plant debris, and logs near water. They are primarily nocturnal and have been recorded in North Carolina from March–November; most records are from May and August.

Much remains to be learned about the natural history of this species. Home range estimates have not been reported.
General Ecology
Adverse Environmental Impacts
Status in North Carolina
NHP State Rank: S2
Global Rank: G5
Status in North Carolina: SC

Photo Gallery for Liodytes pygaea - Black Swampsnake

4 photos are shown.

Recorded by: Jackie Goodman
Dare Co.
Comment: 		Recorded by: Jackie Goodman
Dare Co.
Comment:
Recorded by: Erich Hofmann
Craven Co.
Comment: 		Recorded by: Erich Hofmann
Craven Co.
Comment: