Ouachita Map Turtle (Graptemys ouachitensis)

Distribution: The Ouachita map turtle range extends from Texas and Louisiana north and eastward to eastern Kansas, eastern Iowa, Minnesota, Wisconsin, Illinois, Indiana, Kentucky, Tennessee, and northern Alabama. A population, separated from the main range by 200 km, exists in two counties in Kansas (Mitchell and Pawnee Counties) and in south-central Ohio.

Habitat: The Ouachita map turtle is primarily riverine, inhabiting areas with swift currents and submerged vegetation (Harvey 1992). It can also be found in impoundments, lakes, oxbows, and riverbottom swamps. Sand and silt bottoms are preferred over those of gravel, stone, or mud (Ewert 1979b). Density is influenced by a number of factors, including the amount of algal growth on logs and basking sites available; however, stream width is the primary factor restricting the upstream limit of distribution.

Behavior: Behavior of the Ouachita map turtle is similar to Graptemys pseudogeographica with several important differences. In Wisconsin, where the two species are sympatric, male G. ouachitensis remain in river channels during the summer but G. pseudogeographica move into quiet backwaters to forage. Female G. ouachitensis move to patches of vegetation adjacent to sloughs or river channels after laying their second clutch (Vogt 1980). Both species spend the majority of the day basking during the active season, and are frequently seen basking in large groups (Lovich et al. 1990). Very little is known about the ecology and behavior of this species in the southern part of its range.

Reproduction: Studies conducted in Wisconsin by Vogt (1980) observed courtship and mating in April, October, and November. These studies indicated the nesting season begins in mid-May and lasts until late July, with the first clutch of the season laid from mid-May to mid-June. Nests are constructed between 0545-2030 hr, but peak activity occurs between 0630-1000 hr. Nesting occurs throughout the day on overcast days, but is interrupted by rain. Nest locations and nest construction are similar to G. pseudogeographica. Two and possibly three clutches are laid per year in Oklahoma and Wisconsin (Vogt 1980). Clutch sizes have a mean range of 6 to 15 eggs, with an overall mean clutch size of 10.5. Overwintering in the nest by hatchlings is not common (Ernst et al. 1994). Incubation lasts from 60-82 days. Gender is correlated with incubation temperature. Eggs incubated at 28 oC produce 100 percent males, whereas eggs incubated at 30 oC produce almost no males (Ewert and Nelson 1991).

Food Habits: The Ouachita map turtle is omnivorous, with females feeding on mollusks, insects (caddisfly cases, mayfly larvae, and damselfly larvae), and plant material (e.g., Vallisneria, Potamogeton, Lemna). Males eat the same insects as females, as well as beetles, flies, mollusks, fish carrion, and trace amounts of vegetation. The relatively narrow crushing surfaces of its jaws probably prevent this species from feeding predominantly on mollusks. Feeding begins in late May and continues until mid-September (Vogt 1980).

Populations: Some studies have shown a large female-biased sex ratio (3:1), which may be due to either the effects of temperature-dependent gender determination or to sampling bias (Shively and Jackson 1985).