Graptemys ouachitensis (Cagle, 1953)
Key Characters: Broad, yellow, vertical bar behind eye; large yellow spot under eye and on lower jaw; low knob-bearing keel along midline of back.
Similar Species: Common Map Turtle, False Map Turtle. See Key to Adult Turtles of Illinois for help with identification.
Subspecies: Two subspecies are recognized, Ouachita Map Turtle, G. o. ouachitensis and Sabine Map Turtle, G. o. sabinensis Cagle, 1953. Only the former is found in Illinois.
Description: Medium-sized (up to 22 cm CL) turtle. Carapace brown to olive, with black or dark brown knobs, and with dark blotches on posterior portion of each scute. In some individuals, blotches are encircled by yellow or orange lines; in others lines are present without blotches. Plastron yellowish and, in juveniles, patterned with dark swirls that cover up to half the plastral area. Plastral pattern obscure in old adults. Head, neck, limbs, and tail striped. Male with elongate foreclaws and vent behind end of carapace.
Habitat: Rivers with sand or gravel bottoms.
Natural History: Regularly basks in large numbers on logs and snags near river banks. Omnivorous, eats aquatic insect larvae and vegetation. Nesting occurs mid-May to early June. Two clutches of ellipsoidal, flexible-shelled eggs (ca. 19/clutch) are laid annually. Eggs average 35 x 22 mm.
Status: Status and distribution poorly understood because of identification problems and confusion in literature. Locally common, particularly in Wabash River.
Etymology: Graptemys – grapho (Greek) for write; emydo (Greek) for ‘freshwater tortoise’; ouachitensis – (New Latin) for belonging to the Ouachita Mountains, AR.
Original Description: Cagle, F.R. 1953. Two new subspecies of Graptemys pseudogeographica. Occasional Papers of the Museum of Zoology of the University of Michigan. 546:1-17
Type Specimen: Holotype, UMMZ 104345, collected by A.H. Chaney & C.L. Smith
Type Locality: “Ouachita River, four miles northeast of Harrisonburg, Louisiana”
Original Name: Graptemys pseudogeographica ouachitensis Cagle, 1953
Nomenclatural History: Elevated to species status by Vogt (1980. Tulane Studies Zool Bot 22:17-48).