Systematics: Originally described as Testudo concinna by John LeConte in 1829 from specimens he saw from the rivers of "Georgia and South Carolina." Schmidt (1953) restricted the type locality to the vicinity of Columbia, South Carolina. The first use of the genus Pseudemys for this species was by Gray (1855).

Only two subspecies are recognized here: Pseudemys concinna concinna, and P. c. floridana. Seidel (1994, Chelon. Conserv. Biol. 1: 117–130) demonstrated that P. c. hieroglyphica and P. c. metteri are not distinct and represent only clinal variation; he elevated P. c. suwanniensis to species status; and he relegated P. floridana to a subspecies of P. concinna. The taxonomy adopted here has recently been followed by Ernst and Lovich (2009, Turtles of the United States and Canada. Second Edition. John Hopkins Univ. Press, Baltimore).

Notes on genus: Spinks et al. (2013, Mol. Phylogenet. Evol. 68: 269–281) examined variation in mitochondrial and nuclear DNA across all recognized taxa of Pseudemys, and revealed almost no support for the currently recognized species groups, species, or subspecies. They concluded that the genus was probably over-split, but offered no explicit taxonomic suggestions. Pending more extensive genetic sampling and phylogenetic analyses, and in the interest of stability, we continue to follow the content recommended by Seidel (1994, Chelonian Conserv. Biol. 1: 117–130).

Description: A large riverine freshwater turtle reaching a maximum carapace length (CL) of 420 mm (16.5 inches) (Ward, 1984). In Virginia, known maximum CL is 310 mm, maximum plastron length (PL) is 297 mm, and maximum body mass is 3,700 g.

Morphology: Carapace elongated, with rugosities in adults, and weakly serrated along posterior margin; marginals 12/12, pleurals 4/4, and vertebrals 5; hingeless plastron 79-97% of CL.

Native Pseudemys Face Comparisons

Coloration and Pattern: Carapace brown to greenish brown with yellowish to cream markings; a yellowish, C-shaped figure, bordered by black or brown, occurs on the 2nd pleural scute (and also on 1st and 3d scutes on some individuals), is always directed posteriorly; remaining pattern highly variable and, when visible, often occurs as reticulations; dorsum of marginals bears a dark area, sometimes comprised of concentric circles, and often a yellowish transverse bar; venter of marginals bears several dark spots with yellowish centers that border edge of shell and are usually divided by seams of marginal scutes; bridge with 1 to several dark spots on axillary and inguinal scutes; plastron usually yellowish and with highly variable, narrow, dark figure that follows seams- most of figure is usually confined to anterior portion of plastron in adults; plastral patterns of some individuals obscured; skin color brown to olive with yellowish lines on head and limbs; dorsum of head has a short yellow line that extends to tip of snout; a pair of thin lines bisected by the short line extends posteriorly forming a violin pattern; an oblique stripe lies above and behind eye and another one that parallels it directly behind eye; chin and neck stripes wider than head stripes; upper one forks over upper and lower jaws and chin stripes usually meet anteriorly; >11 lines on head and neck at posterior margin of tympanum; usually no cusps on upper jaw on either side of notch, but some individuals have weakly formed cusps.

Sexual Dimorphism: This species is sexually dimorphic. Adult males averaged 252.3 ± 18.1 mm CL (220-289, n = 19), 225.3 ± 16.2 mm PL (190- 256, n = 19), and 1,563.8 ± 335.0 g body mass (1,066-2,371, n = 19). Adult females averaged 290.2 ± 20.5 mm CL (265-310, n = 5), 273.8 ± 19.3 mm PL (248-297, n = 6), and 3,193.3 ± 607.4 g body mass (2,520-3,700, n = 3). Sexual dimorphism index was 0.15. The elongated tail in males (precloacal distance 37-47 mm, ave. = 42.8 ± 4.0, n = 11) extends the anal opening beyond the posterior edge of the carapace. The anal opening in females does not extend beyond the carapace. The middle right foreclaw length in a single adult male measured 28.3 mm and 13.5 mm in a single adult female.

Juveniles: Juveniles are highly variable and resemble adults in general pattern. The carapace at hatching is greenish with yellow markings and has a keel. The C-shaped mark may not always be present. The only consistent character is the reduced dark pattern along the seams of the scutes on the anterior plastron. Virginia hatchlings were 31.9-36.8 mm CL (ave. = 34.1 ± 1.5, n = 29) and 28.0-34.1 mm PL (ave. = 31.2 ± 1.8), and weighed 6.8-11.0 g (ave. = 8.7 ± 1.2).

Confusing Species: Eastern River Cooters are most likely to be confused with Pseudemys rubriventris, which has a single, wide, vertical bar on each pleural scute, extensive rugosity of the carapace, a pair of prominent cusps on the upper jaw, and arrow-shaped lines on the dorsum of the snout. Pseudemys c. floridana has <11 lines on the head and neck, and lacks the C-shaped mark on the 2d pleural scute and markings on the plastron. Chrysemys picta has 2 yellow spots behind each eye and a light transverse bar across the entire carapace.

Geographic Variation: Geographic variation in Virginia is notable only between the two subspecies. Variation in color and pattern within populations of P. c. concinna is as extensive as between populations. Seidel (1981), Ward (1984), and Ernst and Barbour (1989a) described the variation in named subspecies.

Biology: The Eastern River Cooter is aptly named because it occurs mostly in large rivers. However, the species also occurs in lakes and large ponds in the Piedmont. Preferred habitat appears to be characterized by basking sites (logs, rocks), abundant submerged aquatic vegetation, pools with slow water flow, and places for shelter and overwintering. Not all of the sites at which I have seen them have abundant vegetation, but movement to basking sites can cover large distances-up to 777 m in the New River in West Virginia (Buhlmann and Vaughan, 1991). These researchers reported that the activity season was March to November and occurred when the air temperature exceeded 18°C. Ernst and Barbour (1972) noted that terrestrial activity occurred only during nesting season, but I have three records of males found on major highways outside of this period.

Cooters are predominately herbivorous. Only unidentified plant parts occurred in the feces I examined. Cahn (1937) found crayfish, tadpoles, small fish, snails, insects, algae, and plants in individuals of P. c. concinna he examined in Illinois. Buhlmann and Vaughan (1991) found that adults in West Virginia ate filamentous algae, Elodea, eelgrass (Vallisneria americana), pondweed (Potamogeton crispus), leaves and seed pods of river birch (Betula nigra) and slippery elm (Ulmus rubra), crayfish, fish carrion, and Asiatic clams (Corbicula fluminea). Hatchlings and juveniles ate insects (notably trichopterans), crayfish, and a log perch (Percina caprodes), in addition to Elodea, eelgrass, and pondweed. Predators of adults, other than humans, have not been documented. Ernst and Barbour (1972) and Buhlmann (1986) thought smallmouth bass (Micropterus dolomieu), Snapping Turtles (Chelydra serpentina), snakes, wading birds, and minks (Mustela vison)preyed on juveniles and hatchlings. Eggs are probably depredated in the nest by raccoons (Procyon lotor), skunks (Mephitis, Spilogale), opossums (Didelphis virginiana), and foxes (Urocyon, Vulpes).

Reproduction has been little studied in P. concinna. Copulation was observed in West Virginia by Buhlmann and Vaughan (1991) on 29 April. Nesting behavior has not been described, but nests are placed in sandy soil less than 30 m from water (Ernst and Barbour, 1972). Females with oviductal eggs were found in Virginia on 16 June and 1 July. The female collected on 16 June contained 20 oviductal eggs, nine enlarged follicles, and two sets of corpora lutea. Buhlmann and Vaughan (1991) noted that the smallest mature female was 265 mm PL and the smallest male was 185 mm PL. Clutch size in the Virginia sample was 12-20 eggs (ave. = 15.6 ± 3.9, n = 4). Eggs averaged 36.5 ± 1.3 x 24.5 ± 0.9 mm (length 34.2-39.7, width 23.4-26.1, n = 31) and weighed 11.6-15.4 g (ave. = 12.7 ± 1.2). Laboratory hatching dates were 1 September and 4 October. Seidel (1981) reported a clutch of eight eggs from a female from the New River in West Virginia that hatched on 4 September after incubating for 45-56 days at 30-35°C. One nest excavated on 23 September in Chesterfield County contained hatch-lings that had emerged from their egg shells. Hatchlings apparently overwinter in the nest and emerge the following spring (Buhlmann and Vaughan, 1991).

The population ecology of P. concinna in Virginia is unknown. In West Virginia, Buhlmann and Vaughan (1991) found 64 adult cooters in an 84- km stretch of the New River. Population size estimates for turtles in three pools were 14-23. Linear growth of adults was 2.4 mm per month for females and 6.0 mm per month for males. One hatchling grew 30 mm in 139 days. Two adults were found to overwinter in small pockets of backwater channels with silt substrates.

Cooters are active only during the day and are sometimes seen basking on logs and rocks. They are extremely wary and will drop into the water at the slightest disturbance. I have never seen more than one on the same log or rock in large rivers, but M. E. Seidel (pers. comm.) has observed several on logs in the West Virginia portion of the New River. Aggressive behavior has not been reported. Belkin (1964) reported that pseudemyd turtles do not need to break the surface of the water to breathe. The nasal area establishes a small depression in the surface film and the cooter can breathe without projecting any part of the body above the water. Perhaps this helps to explain why P. concinna is not as commonly seen as other turtles.

Remarks: A vernacular name used in Virginia is "barred terrapin" (Mitchell, 1990b).

Conservation and Management: This turtle appears to be secure in Virginia, although this determination is based on few real data. Studies of the population ecology and life history of this turtle would provide needed information to assess demography, population dynamics, and life history parameters. Such data would allow us to identify problems and threats, if they indeed exist, and the development of appropriate management plans. The shooting of these turtles as they bask on logs and rocks in rivers and lakes should be illegal. Conservation education on the roles of these turtles in the river community may lessen this type of human impact.

U.S. Range