False Map Turtle (Graptemys pseudogeographica)

Distribution: Found primarily in large streams of the Missouri and Mississippi River systems from Ohio, Indiana, Illinois, Wisconsin, Minnesota, and the Dakotas southward; possible to extreme southwestern Alabama, southern and western Mississippi, Louisiana, and eastern Texas.

Habitat: Typically found in large rivers and their backwaters, but also occupies lakes, ponds, sloughs, bayous, oxbows, and occasionally marshes. The false map turtle prefers water with abundant aquatic vegetation, places to bask, and slow currents, but can be found in swiftly flowing channels of large rivers.

Behavior: Activity varies geographically, but generally ranges from late March to mid-October (Johnson 1983). Emergence from overwintering (observed in Wisconsin) occurs in April when water temperatures are 4-7 o C (Vogt 1980). Overwintering sites typically include muskrat lodges or bank burrows. It is not uncommon for the false map turtle to be seen basking during winter days in its more southerly range. It spends the majority of its day basking (from 0900 to 1800 hr) on muskrat lodges, logs, rock piles, sandbars, or stumps. Basking rarely occurs on or near shore. Basking turtles stretch their hind limbs, spread the webbing between the toes, and extend the head and forelimbs. Basking turtles are extremely wary and difficult to approach. Entrance into the water by one turtle is usually followed by all those basking in the general vicinity. Movement data of this turtle is sparse. In summer months, most males move into quiet backwaters to forage. Females also move into backwaters to forage after laying their first clutch of eggs (Vogt 1980).

Reproduction: Mating (data obtained from one study in Wisconsin) probably occurs in April and again in October and November (Vogt 1980) but has been observed in a captive male in July (Ernst 1974). The nesting season (Wisconsin) lasts from mid-May to late July. First clutches are usually laid by mid-May to mid-June (Vogt 1980). Nest construction occurs from 0545 and 2030 hr; however, most clutches are deposited from 0630 to 1000 hr on overcast days. Nests are located in open sand areas or in areas dominated by low shrubs. Nests are flask-shaped and dug with the hind limbs. Two and possibly three clutches, from 8-22 eggs (varies with subspecies), are laid per year. Natural incubation lasts from 60 to 82 days (Ewert 1979a). Gender determination correlates with incubation temperature (males at < 25 oC; females at > 30 oC).

Food Habits: The false map turtle is omnivorous, feeding on mollusks, insects (e.g., mayfly and damselfly larvae), and plant material (Vallisneria, Potamogeton, and Lemna). In addition to consuming the same insects as females, males eat beetles, flies, and fish carrion (Vogt 1981a, 1981b). In its southern range, mollusks are the principal component of the diet.

Populations: Declining populations in Missouri are attributed to several factors, including water pollution, river channelization, reduction of suitable nesting sites, siltation, and unlawful shooting (Johnson 1983). In the past, the pet trade has also influenced population stability. Commercial fish-ermen reported that the species was more abundant 25 years earlier in the Missouri and Mississippi Rivers, but has now become uncommon and all but eradicated for several river miles below Kansas City and St. Louis. They attributed this decline to water pollution.