Cagle, 1953a
Ouachita map turtle
Recognition
The oval carapace (to 24 cm) has a distinct medial keel bearing conspicuous low spines, and a serrated posterior rim. Vertebrals are usually broader than long, but the 1st, which is smallest, may be as broad as long or longer than broad. The carapace is olive or brown, and each pleural has yellow vermiculations and dark blotches. Upper and lower edges of the marginals have a yellow ocellus at each seam. The bridge is marked with dark bars. The plastron is cream to olive yellow with longitudinal dark lines. Its hindlobe is posteriorly notched. The plastral formula is: abd > an > fem > pect > hum >< gul. The head is narrow to moderately broad with a nonprotruding snout and no medial notch or hook on the upper jaw. Skin is olive to brown or black with numerous narrow yellow stripes on the legs, tail, chin, and neck. The postorbital mark is either square to rectangular or elongate to oval, and usually consists of a downward extension of a neck stripe behind the orbit; one to nine neck stripes reach the orbit. Two large, light spots may occur on each side of the face, one just under the eye and another on the lower jaw, and transverse bars are often present under the chin.
Diploid chromosomes total 50: 26 macrochromosomes with 48 arms, and 24 microchromosomes with 24 arms (McKown, 1972; Killebrew, 1977a).
Adult males have long, thick tails, with the vent posterior to the carapacial rim, and elongated foreclaws (especially the third). Adult males are 10-14 cm in carapace length, females 16-24.
Distribution
Graptemys ouachitensis ranges from Texas and Louisiana north and eastward to Nebraska, Minnesota, Wisconsin, Indiana, Ohio, and West Virginia.
Geographic Variation
The two subspecies of Graptemys ouachitensis were formerly considered subspecies of G. pseudogeographica (Cagle, 1953a), but Vogt (1980) has compiled sufficient data to show the northern subspecies ouachitensis to be separate from sympatric G. pseudogeographica. G. o. ouachitensis Cagle, 1953a, the Ouachita map turtle, ranges from the Ouachita River system of northern Louisiana west to Oklahoma and northward to Kansas, Minnesota, Wisconsin, Indiana, Ohio, and West Virginia. It has an extensive square to rectangular postorbital mark, one to three neck stripes touching the orbit, and two large, light spots on each side of the face, one just under the eye and another on the lower jaw. The Sabine map turtle, G. o. sabinensis Cagle, 1953a, is restricted to the Sabine River system of Texas and Louisiana. It has an elongate or oval postorbital mark, five to nine neck stripes reach the orbit, the two light spots on each side of the face are reduced in size.
Habitat
This is a riverine species, inhabiting areas with swift currents and submerged vegetation (Vogt, 1980; Harvey, 1992). Shively and Jackson (1985) studied the habitat in Louisiana, and reported that the most important proximate determinants of the species density were the amount of algal growth on logs and basking site area, but stream width was the ultimate determinate restricting the upstream limit of distribution. G. ouachitensis can tolerate sites with sand bottoms and relatively high water temperatures (Fuselier and Edds, 1994).
Natural History
Males mature in years 2-3 at plastron lengths of 6-7 cm (Cagle, 1953a; Webb, 1961). Females mature at about 15-16 cm in plastron length in years 6-7 (Webb, 1961). Courtship and mating occur in the spring; the male strokes the female's face with his elongated foreclaws.
Nesting takes place from late May through June and several clutches of 8 to 17 eggs are laid each year. The elliptical eggs (28-36 x 20-29 mm) have leathery shells. Incubation takes 60-75 days and the round, keeled hatchlings are about 30 mm in length. Eggs incubated at 25°C hatch into males, those incubated at 30.5°C hatch into females (Bull and Vogt, 1979).
Graptemys ouachitensis is omnivorous, feeding on algae and a variety of higher aquatic plants, mollusks, insects, worms, crayfish, and fish. It is fond of basking, but is very wary and difficult to approach.
IUCN Red List Status (1996)
Not listed.