Bog Turtle Natural History Profile

Habitat

The semi-aquatic bog turtle inhabits slow, shallow, muck-bottomed rivulets of sphagnum bogs, calcareous fens, marshy/sedge-tussock meadows, spring seeps, wet cow pastures, and shrub swamps; the habitat usually contains an abundance of sedges or mossy cover. The turtles depend on a mosaic of microhabitats for foraging, nesting, basking, hibernation, and shelter (USFWS 2000). "Unfragmented riparian systems that are sufficiently dynamic to allow the natural creation of open habitat are needed to compensate for ecological succession" (USFWS 2000). Beaver, deer, and cattle may be instrumental in maintaining the essential open-canopy wetlands (USFWS 2000). In the northern half of the range, other turtles most likely to occur in bog turtle habitat include the spotted turtle, painted turtle, and wood turtle.

Phenology

Most activity occurs from mid-April to late September in New Jersey and Pennsylvania. In some areas, including Pennsylvania and Delaware, there is an apparent peak in activity in May (see Bury 1979). Reportedly may estivate or at least reduce activity to a small area during hot summer periods (especially July-August). In North Carolina, radiotelemetry showed that turtles remained active through summer and fall whereas hand captures indicated primarily vernal activity (Herman and Fahey 1992). In Maryland, movement into and out of retreats was noted from November through March (Chase et al. 1989). Active during daylight hours, mostly from mid-morning to late afternoon or early evening. More active on cloudy days than on bright sunny days (Mitchell 1991). In early spring, activity occurs mainly at midday and in the afternoon; most active in the morning in late spring and summer (Mitchell 1991).

Reproduction

Mating occurs from late April to early June. Lays clutch of 1-6 (usually 3-5) eggs in May, June, or July (occasionally August). Eggs hatch in about 6-9 weeks, late July to early September. In the north, hatchlings may not emerge from the nest until October or they may overwinter in the nest. Sexually mature in 5-8 years. Not all adult females produce clutches annually. No evidence of multiple clutches within a single season. Nests are in open and elevated ground in areas of moss, sedges, or moist earth (see Bury 1979). The turtles dig a shallow nest or lay eggs in the top of a sedge tussock.

Overwintering

In Pennsylvania, bog turtles overwintered mainly in water and mud in muskrat burrows, and in mud bottom of marsh rivulets under 5-15 cm of water. In New Jersey, hibernacula were in subterranean rivulets or seepage areas where water flowed continuously from underground springs; turtles were under 5-55 cm of water and mud (see Ernst et al. [1989] for further details). In Maryland, winter retreats were shallow, just below upper surface of frozen mud and/or ice (Chase et al. 1989). Studies in Maryland and Pennsylvania noted use of the lower portion of wetlands for overwintering.

Food

Omnivorous. Feeds opportunistically on insects, worms, slugs, crayfish, snails, and other small invertebrates; also, amphibian larvae and fruits. Diet generally is dominated by insects. Apparently forages on land and in water (Bury 1979).

Home Range

Home range size averaged 1.3 ha in Pennsylvania, where the longest distance moved by any individual was 225 m (see Bury 1979). Home range was 0.04-ha to 0.24 ha in Maryland (Chase et al. 1989). Home range size averaged 0.52 ha (median 0.35 ha, range 0.02-2.26 ha, minimum convex polygon) in Virginia (Carter et al. 1999). Long-distance movements between wetlands were infrequently observed in southwestern Virginia (Carter et al. 2000). In North Carolina over somewhat less than 1 year, distances between relocations of radio-tagged turtles were 0-87 m (mean 24 m) for males, 0-62 m (mean 16 m) for females (Herman and Fahey 1992).

Populations

Population density may exceed 110/ha in some areas (see Ernst and Barbour 1972). In Maryland, population density was 7-213/ha of wetland habitat; average was 44 individuals per site at 9 sites (Chase et al. 1989). Searches of suitable habitat in North Carolina and Delaware yielded 1 bog turtle per 1.8 to 4.2 hours of search (see Bury 1979). In Pennsylvania, patches of suitable habitat had 3 to 300 individuals, mostly around 30 (see Mitchell 1991).

Predators

Eggs, young, and adults are preyed on by various Carnivora, opossums, and some wading birds. Juveniles are very secretive. - Jason Tesauro, March 2021

Adapted from: Eichelberger, C. (2018), Wilkinson, A. M., G. Hammerson, and L. Master (2011).

Link: NatureServe Conservation Status Factors

References:
1). Bury, R. B.1979. Review of the Ecology and Conservation of the Bog Turtle, Clemmys muhlenbergii. U.S. Department of the Interior, Fish and Wildlife Service. Special Scientific Report-Wildlife, No. 219.
2). Carter, S. L., C. A. Haas, and J. C. Mitchell. 1999. Home range and habitat selection of bog turtles in southwestern Virginia. Journal of Wildlife Management 63:853-860.
3). Carter, S. L., C. A. Haas, and J. C. Mitchell. 2000. Movements and activity of bog turtles (Clemmys muhlenbergii) in southwestern Virginia. Journal of Herpetology 34:75-80.
4). Chase, J. D., et al. 1989. Habitat characteristics, population size, and home range of the bog turtle, Clemmys muhlenbergii, in Maryland. J. Herpetol. 23:356-362.
5). Ernst, C. H., and R. W. Barbour. 1972. Turtles of the United States. Univ. Press of Kentucky, Lexington. x + 347 pp.
6). Ernst, C. H., R. T. Zappalorti, and J. E. Lovich. 1989. Overwintering sites and thermal relations of hibernating bog turtles, CLEMMYS MUHLENBERGII. Copeia 1989:761-764.
7). Herman, D. W., and K. M. Fahey. 1992. Seasonal activity and movements of bog turtles (CLEMMYS MUHLENBERGII) in North Carolina. Copeia 1992:1107-1111.
8). Mitchell, J. C. 1991. Amphibians and reptiles. Pages 411-76 in K. Terwilliger (coordinator). Virginia's Endangered Species: Proceedings of a Symposium. McDonald and Woodward Publishing Company, Blacksburg, Virginia.
9). U.S. Fish and Wildlife Service (USFWS). 2000. Bog turtle (Clemmys muhlenbergii), northern population, recovery plan, agency draft. Hadley, Massachusetts. viii + 90 pp.