Muhlenberg turtle (Bog turtle)

Identifying Characteristics

Photo by J.D. Kleopfer/DWR

Photo by USFWS

North America’s smallest turtle, the bog turtle is a freshwater turtle that has a maximum carapace length of 4.5 inches. The carapace is light brown to mahogany or black, and slightly domed with a low keel. The carapace is roughened with growth rings that are dark brown to black, sometimes with irregular radiations or markings, and has a smooth posterior rim. A conspicuous orange, yellow, or red blotch occurs behind each eye. The hinge-less plastron is mostly black, with some irregular yellow to cream-colored blotches and is concave in males. Males are larger than females, with a noticeably larger tail.

This species is not sexually mature until 6 years of age. It breeds from late April to early June, in shallow water and on land, and eggs hatch in the fall. There may be two clutches per year and it takes from 50-59 days for the eggs to hatch. The eggs are laid in shallow nests in grass tussocks, moss, or soft soils.

Photo by Mike Knoerr

This species is active only during April, May, June and September and aestivates during high temperatures. It is usually seen only during the early spring and during the nesting season because the dead and matted grasses and sedges form a dense ground cover during late spring and summer. During the winter, this turtle hibernates below the frost depth in holes, muskrat burrows, in sedge clumps, or in the mud of waterways. The mean home range is 3.2 acres. Bog turtles bask during midday on grass mats or in shallow rivulets.

Habitat

Bog turtles occupy spring-fed wetlands, and use areas with soft, deep substrate and persistent shallow water. Sedge-dominated wetlands may provide important structure through their tussock or hummock-forming growth. Wetlands occupied by bog turtles tend to have areas that are permanently saturated, even in draught years, and low-strength soils.

Nests are placed at slightly elevated locations, often on sedge or sphagnum hummocks in wetland areas with sun exposure. Egg mortality can occur if nests flood or the eggs desiccate.

Distribution:

This species is found in six counties in southwest Virginia, only in the southern Blue Ridge Plateau above 610 meters elevation. It inhabits sphagnum bogs or wet sedge meadows in or near slow-moving streams with a muddy bottom. The highest populations occur in the shrub stage of forest succession. Alder, skunk cabbage, and sedges are common plant associations.