Bog Turtle
Glyptemys muhlenbergii

* Federal Threatened State Endangered *

Common Name:

Bog Turtle

Scientific Name:

Glyptemys muhlenbergii



Giypt is Greek meaning "carved", emys is Greek meaning "turtle".


muhlenbergii - was assigned to honor Reverend Gotthilf Heinrich Ernst Muhlenberg, an 18th century botanist from Pennsylvania who first found this turtle in his millpond.

Average Length:

3 - 3.5 in. (7.5 - 9 cm)

Virginia Record Length:

4 in. (10.2 cm)

Record length:

4.5 in. (11.4 cm)

Systematics: Originally described as Testudo muhlenbergii by Johann David Schoepff in 1792-1801, based on a specimen sent to him by Gotthilf Heinrich Ernst Muhlenberg from "Pensylvaniae." Stejneger and Barbour (1917) restricted the type locality to Lancaster County Pennsylvania. The genus Clemmys was first used for this species by Fitzinger (1835); all Virginia authors have followed this nomenclature. Work by Bickham et al. (1996, Herpetologica 52: 89–97), Burke et al. (1996, Herpetologica 52: 572–584), Lenk et al. (1999, Mol. Ecol. 8: 1911–1922), Holman and Fritz (2001, Zoolog. Abhand. Staat. Mus. für Tierkunde Dresden 51: 331–354), Feldman and Parham (2002, Mol. Phylogenet. Evol. 22: 388–398), Seidel (2002, Copeia 2002: 1118–1121), Stephens and Wiens (2003, Biol J. Linn. Soc. 79: 577–610), Wiens et al. (2010, Biol. J. Linn Soc. 99: 445-461), and Fritz et al. (2011, Zootaxa 2791: 41-53) provided ample evidence that the genus Clemmys as previously recognized (e.g., McDowell, 1964, Proc. Zool. Soc. Lond. 143: 239–279) was paraphyletic with respect to the sister genera Emys and Emydoidea, and also possibly Terrapene. Two taxonomic schemes reflecting these relationships are currently in contention. Both would place sister taxa insculpta and muhlenbergii in the genus Glyptemys and leave guttata in the monotypic genus Clemmys. No subspecies are recognized.

Description: A small freshwater turtle reaching a maximum carapace length (CL) of 115 mm (4.5 inches) (Ernst and Bury 1977). In Virginia, known maximum CL is 102 mm, maximum PL is 89 mm, and maximum body mass is 132 g.

Morphology: Carapace usually roughened with growth annuli or smooth in old individuals without serrations along the posterior margin; marginals 12/12, pleurals 4/4, and vertebrals 5; hingeless plastron 86-91% of CL.

Coloration and Pattern: Carapace black to brown, sometimes with irregular radiations or light markings; centers of pleural scutes may be lighter than the surrounding area; color of marginals above and below and bridge same as carapace; hingeless plastron usually black with irregularly shaped blotches of yellow to cream along midline; skin on head, neck, and limbs brown to pinkish brown; red mottling occurs on limbs of some turtles; a large, conspicuous orange, yellow, or red blotch behind each eye.

Sexual Dimorphism: Adult males have a concave plastron and an elongated tail with the cloacal opening extending beyond the posterior edge of the carapace (average precloacal distance = 24.8 ± 5.0 mm, 16-31, n = 12). Adult females have a flattened plastron, a higher and wider carapace, and a shorter tail (average precloacal distance = 14.4 ± 3.5 mm, 11-18, n = 5). Virginia males averaged 91.3 ± 8.0 mm CL (70.2-101.7, n = 17), 79.0 ± 6.2 mm PL (63-88.7, n = 17), and 106.1 ± 25.0 g body mass (54-132, n = 12). Females averaged 87.3 ± 7.5 mm CL (72.3-102.0, n = 15), 79.0 ± 5.9 mm PL (66.8-87.8, n = 15), and 108.2 ± 19.7 g body mass (65-130, n = 11). Sexual dimorphism index based on CL was -0.05.

Juveniles: Juveniles differ slightly from adults. The carapace is round and dark brown in color, and usually has a conspicuous keel. The plastron is yellow with a large black blotch in the center. The bright orange patch behind the eye is present at hatching. The only known hatchlings from Virginia were 27.7-28.5 mm CL (ave. = 28.1, n = 3; Herman, 1987b).

Confusing Species: Bog Turtles may be confused with small Terrapene Carolina, but the latter has a hinged plastron and a brightly multicolored carapace, and lacks the single, large orange spot behind the head. No other similar freshwater turtle occurs within its range in Virginia. Glyptemys insculpta is larger, and has a sculptured carapace and a long tail.

Geographic Variation: None known for Virginia. Studies of genetic and morphometric variation among the various geographically separate isolates have not been published.

Biology: Bog Turtles are found in upland freshwater wetlands characterized by open fields or meadows with slow-moving streams, ditches, and Boggy areas. Alder (Alnus serrulata), skunk cabbage (Symplocarpus foetidus), and sedges (Carex spp.) are common plant associates. Grasses that are dead and matted in winter and early spring form a dense ground cover during late spring and summer. Consequently, Bog Turtles are usually seen only in early spring and during nesting season (see below). Seasonal distribution of 172 individual records from Virginia are as follows: March (0.05%), April (2.9%), May (62.2%), June (21.5%), July (5.2%), August (0.05%), and September (6.9%) (Herman, 1987b, 1988; J. C. Mitchell and K. A. Buhlmann, unpublished). The earliest observation was on 5 March and the latest was on 29 September. Using radiotelemetry, Lovich et al. (1992) discovered that Bog turtles in North Carolina were more active in summer and fall months than had been previously documented. In winter, Bog turtles hibernate in muskrat (Ondatra zibethicus) burrows, sedge clumps, or the mud of waterways (Ernst, 1977; Ernst et al., 1989).

Nothing is known of the prey of Bog Turtles in Virginia. Elsewhere in their range they are omnivores (Ernst and Barbour, 1989a). Bog Turtles eat in or out of the water. Known prey include a variety of insects, earthworms, slugs, snails, millipedes, crayfish, tadpoles, duckweed (Lemna spp.), watercress (Barbarea spp.), skunk cabbage, blackberries (Rubus spp.), strawberries (Fragaria spp.), and seeds of pondweed (Potamogeton spp.) and sedges (Ernst and Barbour, 1972; Bury, 1979a). Carrion-dead frogs and insects-are sometimes eaten. Predators of eggs, juveniles, and adults are raccoons (Procyon lotor), skunks (Mephitis, Spilogale), opossums (Didelphis virginiana), dogs, foxes (Urocyon, Vulpes), and some wading birds. Several individuals are killed by vehicles on roads each year (J. C. Mitchell and K. A. Buhlmann, unpublished). Adults are sometimes found with missing limbs and gnawed shells.

Mating occurs in late April to early June in shallow water and on land (Ernst and Barbour, 1989a). Virginia records are 5 and 23 May (K. Nemuras, pers. comm.; J. C. Mitchell and K. A. Buhlmann, unpublished). Nemuras (1974) noted that his observation took place in rainy weather; the pair found by Mitchell and Buhlmann were under grass in sunny weather. Mating is similar to that described for Wood Turtles, with the male clinging tightly to the edge of the female's carapace and juxtaposing his tail beneath hers; shell pounding has not been observed. Size at maturity in a Pennsylvania population was 70 mm PL at an age of 6 years for both males and females (Ernst, 1977). Eggs are laid in May to July in shallow nests in grass tussocks, moss, or soft soils (Ernst and Barbour, 1989a). Herman (1987b) reported a captive egg-laying date of 20 June for a Virginia Bog Turtle. Known clutch size for Virginia Bog Turtles is 3-4 (n = 2). Multiple clutches are possible, at least in captivity (Herman, 1986). Laboratory incubation time for one clutch was 46 days (Herman, 1987b); it is unknown for natural populations. The only known hatching date for a Virginia clutch is 4 August (Herman, 1987b). Most hatching occurs in August, but emergence may be delayed until October or the following April or May (Mitchell et al., 1991). Twin embryos from a single North Carolina egg was reported by Herman (1987a).

The population ecology of this species has been little studied in general and not at all in Virginia. Populations of 5-125 individuals have been reported elsewhere in its range (Bury, 1979b). Chase et al. (1989) found populations of 7-213 Bog Turtles in Maryland wetlands. Populations of 3-300 have been seen in Pennsylvania and most seem to be comprised of adults; juveniles are very secretive (Mitchell et al., 1991). Average home range of adults in Pennsylvania was 1.3 hectares, and the longest distance moved was 225 m (Ernst, 1977). Males occupied larger home ranges (0.176 hectare) than females (0.066 hectare) in Maryland (Chase et al., 1989). Growth rates decline with age; adults grow 1.7 to 4.0 mm per year (Ernst, 1977). Herman (1987b) reported that during the 11 years between captures, the plastron of a North Carolina female grew 6.6 mm but the carapace did not grow at all. Bog turtles bask during midday on grass mats or in shallow rivulets. Body temperatures of basking turtles were 22.0-31.0°C in a Pennsylvania population (Ernst, 1977). Feeding and searching for prey occurs in the morning and late afternoon. Considerably more activity occurs on cloudy days than on bright sunny days. These turtles escape potential predation, including human, by turning themselves on end and diving into soft mud, swimming through it as if it were water. They are not aggressive.

Remarks: Common names in Virginia are "Muhlenberg's turtle" (Dunn, 1936) and "red neck turtle."

This little turtle is a reptile pet fancier's prize. Several individuals are poached every year or two despite the legal protection placed on this species in every state in which it lives. Because Bog Turtles are small and colorful, are generally easy to keep, and respond well to behavioral conditioning, it is easy to imagine why they are sought after.

Conservation and Management: This species was listed as endangered under Virginia law on 1 October 1987. Its listing was in response to pet trade activity. The primary threats to Virginia populations are loss of habitat by draining of wet meadows and other wetlands, and illegal collecting for the pet trade. Several populations occur on National Park Service property but most occur on private lands. Conservation efforts must include a three-pronged approach. These are the accumulation of critical data on population ecology and demography (e.g., home range size, movements, population structure, survivorship, and recruitment rate), the education of private land owners in the range of this turtle, and the protection of the wetlands used by this species. Mitchell et al. (1991) provided a more extensive list of recommendations and management options. A comprehensive regional conservation plan that incorporates landscape and population ecology with culture and economics is needed to ensure the long-term survival of the species.

References for Life History


*Click on a thumbnail for a larger version.

Verified County/City Occurrence

Carroll County
Floyd County
Franklin County
Grayson County
Patrick County
Roanoke County
Verified in 6 Counties/Cities.

Box Turtle Reporting

VHS Amazon Smile

Spadefoot Reporting