Glyptemys muhlenbergiiBog Turtle

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Geographic Range

Bog turtles occupy a highly discontinuous and fragmented range in the eastern United States of America; within this range they tend occur in small, often widely separated colonies. For management purposes two general "populations" are often recognized-- a northern population from eastern New York and western Massachusetts south through southeastern Pennsylvania and New Jersey to northern Maryland and Delaware (with outliers in northcentral New York and western Pennsylvania), and a southern population (generally at higher elevations, up to 4000 feet) from southern Virginia, western North Carolina, and eastern Tennessee to extreme northeastern Georgia. There are no reliable morphological differences between bog turtles in these designated populations. The bog turtle is one of the most endangered turtle species in North America. (Ernst, et al., 1994; Harding, 1997; Herman, 1981)

Habitat

Bog turtles are a highly specialized species that occupies a relatively narrow range of shallow and rather ephemeral wetland types, from sea level up to 1300 meters elevation. They occur in saturated, usually spring-fed wetlands such as bogs, fens, wet meadows, sedge marshes, and alder, tamarack, or spruce swamps. Ideal habitat is relatively open with slowly flowing small streams, rivulets, or surface seepages with soft muddy or silty bottom substrates, and with a vegetation dominated by clumped grasses and sedges. Biotic diversity is often very high in these habitats, with over 150 plant species reported in one small Tennessee bog. Natural or human -caused succession may rapidly degrade bog turtle habitats, as the turtles require more open, unshaded situations. (Chase, et al., 1989; Ernst, et al., 1994; Harding, 1997; Herman and Pharr, 1986; Tryon, 1990)

  • Range elevation
    1300 (high) m
    4265.09 (high) ft

Physical Description

This is the smallest emydid turtle, and one of the smallest turtles in the world. Adult carapace length is 7.9 to 11.4 cm (3.1 to 4.5 inches). The dark brown or black carapace may be marked with radiating light lines or a light blotch on the vertebral and pleural scutes. Scute annuli are usually prominent in juvenile and young adult specimens, but the carapace may be nearly smooth in old adults. The head, neck, and limbs are typically dark brown with variable reddish to yellow spots and streaks. A large reddish-orange to yellow blotch is visible behind and above each tympanum, sometimes merging into a continuous band on the neck. The upper jaw is weakly notched. (Ernst, et al., 1994; Harding, 1997)

The plastron is also brown or black, but often with lighter yellow blotches towards the medial and anterior scute edges. A mature male bog turtle has a concave plastron and a long, thick tail, with the vent posterior to the rear edge of the carapace with tail extended. The female has a flat plastron and a thinner, smaller tail, with the vent at or beneath the rear carapace edge. (Ernst, et al., 1994; Harding, 1997)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    7.9 to 11.4 cm
    3.11 to 4.49 in

Reproduction

Mating occurs in spring (March to May). The large bright head blotches undoubtedly serve in species recognition. Courtship can involve much nudging and biting of the female's head, legs, and shell by the male. While mounted, the male may thump the female's shell with his plastron, a behavior common in related wood turtles (Glyptemys insculpta). Copulation may take from five to 20 minutes.

The nesting season extends from mid-May to early July, with most eggs laid in June. While seeking nest sites, females tend to move to higher, better-drained parts of the habitat, though nests are sometimes contructed in the centers of emergent sedge tussocks surrounded by water. In any case, an open sunny nest site is preferred, with moist substrates of soil, sand, or sphagnum moss. Most nests are constructed with the hind feet, in typical turtle style. From one to six eggs are deposited, and a single yearly clutch appears to be the norm.

Eggs are elongate and white, with pliable shells, and average about 3 cm (1.2 inches) in length. The incubation period averages between 45 and 65 days. At this writing it is unclear whether this species has temperature-dependent sex determination. The hatchlings range in carapace length from 21.1 to 28.5 mm. Growth rates can be rapid in the first few years but taper off as the turtle nears maturity, at an age of four to ten years. (Ernst, et al., 1994; Harding, 1997; Holub and Bloomer, 1977)

  • Breeding interval
    Bog turtles breed once yearly.
  • Breeding season
    Mating occurs in spring (March to May). The nesting season extends from mid-May to early July, with most eggs laid in June.
  • Range number of offspring
    1 to 6
  • Average number of offspring
    3
    AnAge
  • Range gestation period
    45 to 65 days
  • Range age at sexual or reproductive maturity (female)
    4 to 10 years
  • Range age at sexual or reproductive maturity (male)
    4 to 10 years

Once the female deposits her eggs in a nest, there is no further parental investment. (Harding, 1997)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Potential lifespan is unknown but certainly meets or surpasses the 40 years known for a captive specimen. (Ernst, et al., 1994; Harding, 1997; Holub and Bloomer, 1977)

  • Range lifespan
    Status: captivity
    40 (high) years
  • Average lifespan
    Status: captivity
    40 years
    AnAge

Behavior

This is primarily a diurnal species, though nocturnal activity (such as nesting) has been reported. On cool days Bog Turtles spend much time basking in the sun, from the surface of shallow waterways or on sedge or grass tussocks, but during hot weather they tend to be inactive and may estivate under vegetation or in burrows in sphagnum moss substrate. In winter they hibernate in mud or vegetation beneath the shallow waters and rivulets or in their submerged burrows. The same hibernation site is often used in subsequent years, and groups of turtles may congregate in favored locations. Some bog turtles are territorial, aggressively defending a small area immediately around themselves, rarely larger than 1.2 meters in radius. (Arndt, 1977; Chase, et al., 1989; Ernst, et al., 1994; Harding, 1997; Holub and Bloomer, 1977; Morrow, et al., 2001)

Home Range

Home ranges reported for bog turtles range from less than 0.1 to 3.1 hectares. However, in some populations, the total available habitat for these turtles may not exceed these values. (Harding, 1997)

Food Habits

Bog turtles are omnivorous, and consume food both in and out of water. They eat mainly small invertebrates (insects, slugs, snails, crustaceans, worms, etc.) along with seeds, berries, and green vegetation. They also occasionally scavenge dead animals and opportunistically capture small vertebrates such as tadpoles, frogs, and salamander larvae. (Harding, 1997; Holub and Bloomer, 1977)

  • Animal Foods
  • amphibians
  • carrion
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • aquatic crustaceans
  • Plant Foods
  • leaves
  • seeds, grains, and nuts
  • fruit

Predation

Bog turtles are vulnerable to a host of natural predators because of their small size, even as adults. (Harding, 1997)

Economic Importance for Humans: Positive

Bog turtles undoubtedly consume quantities of pest insects and larvae, but are most valuable as a unique evolutionary entity and a noteworthy element of our wildlife resources. They are a "flagship" species representing a biologically diverse, but rare, fragile, and endangered habitat. These turtles are small, colorful, and visually appealing, which has led to an unfortunate demand in the commercial pet trade.

Economic Importance for Humans: Negative

As a biological species, bog turtles are completely harmless to human interests. Unfortunately, the protected status of this turtle may lead some people to consider them an an annoyance or impediment to land development.

Conservation Status

The fragile saturated wetlands required by bog turtles may have been most abundant in an earlier post-glacial stage, and the species may have once been quite abundant and widespread in eastern North America, though the fossil record of this species is sparse. The present highly fragmented range of bog turtles may reflect both natural changes in habitat distribution and the recent drastic losses in habitat due to human development and wetland drainage. While turtle populations could at one time respond to natural successional changes by simply moving up a floodplain, these routes are now often blocked by roads, farms, residences, and other development.

Bog turtles have been, and remain, popular in the commercial pet trade, due to their small size and unique coloration. During the latter part of the 20th century large numbers of the turtles were collected and sold, with whole populations sometimes being removed from existing habitat, often in violation of state laws. Legal collection of bog turtles from the wild is now precluded by both state and federal statute, but it is likely that high prices offered for "legal" captive specimens may encourage poaching, despite the threat of severe penalties.

Bog turtles certainly have a host of natural predators; egg and hatchling mortality are undoubtedly high, and the small size of the species means that even adult individuals remain vulnerable to predation. The unnaturally high population levels of certain human-adapted predators such as raccoons (Procyon lotor) and common crows (Corvus brachyrhynchos) complicate conservation efforts for bog turtles.

Like many turtle species, bog turtles have a life history strategy that balances low fecundity, high egg and hatchling mortality, and relatively late maturity, with the potential long reproductive lifespan of the adults. While populations can increase and thrive in ideal habitat, this reproductive strategy limits the ability of a turtle population to recover quickly if faced with a natural or human-caused disaster or unusually high mortality in older juveniles and adults. In addition, isolation of bog turtle habitats may increase the dangers of limited genetic exchange and inbreeding.

Conservation stategies include identification of critical habitats, the preservation of habitats, and protection of turtles from collection. Predator control may prove useful in some situations. Habitat set-asides must take into account landscape variation and natural succession; where economic concerns limit the amount of habitat protected and preclude connection of habitats via wildlife corridors, land management practices to maintain early successional stages may be required. Carefully planned captive breeding and release programs can prove useful in some situations. Public support for bog turtle conservation efforts can be maintained by encouraging voluntary management on private land and compensation for economic sacrifices where needed. (Congdon, et al., 1993; Ernst, et al., 1994; Harding, 1997; Herman, 1981; Holub and Bloomer, 1977; Tryon and Herman, 1991; Tryon, 1990)

Other Comments

Recent taxonomic studies of turtles in the subfamily emydinae show that bog turtles are most closely related to wood turtles (Glyptemys insculpta, previously Glyptemys insculpta). These studies also show that the genus Clemmys is paraphyletic, and that a new generic arrangement between bog turtles and their closest relatives is warranted (Bickham, et al., 1996; Burke et al., 1996; Gaffney and Meylan, 1988). In accordance with recent published revisions, bog turtles and wood turtles are now grouped together in the genus Glyptemys, as Glyptemys muhlenbergii and Glyptemys insculpta, respectively (Holman and Fritz, 2001; Feldman and Parham, 2001; Feldman and Parham, 2002).

Bog turtles are reported to hybridize with spotted turtles, Clemmys guttata, which is similar in size and overlaps in habitat preferences (Ernst. et al., 1994). (Bickham, et al., 1996; Burke, et al., 1996; Ernst, et al., 1994; Feldman and Parham, 2001; Feldman and Parham, 2002; Gaffney and Meylan, 1988; Holman and Fritz, 2001)

Contributors

James Harding (author), Michigan State University, Cynthia Sims Parr (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carrion

flesh of dead animals.

diurnal
  1. active during the day, 2. lasting for one day.
ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

References

Arndt, R. 1977. Notes on the natural history of the Bog Turtle, *Clemmys muhlenbergii* (Schoepff), in Delaware.. Chesapeake Sci., 18: 67-76.

Beane, J. 1993. A survey of Bog Turtle (*Clemmys muhlenbergii*) habitat in the western piedmont of North Carolina. Bull. Chicago Herpet. Soc., 28 (11): 240-242.

Bickham, J., T. Lamb, P. Minx, J. Patton. 1996. Molecular systematics of the genus *Clemmys* and the intergeneric relationships of emydid turtles. Herpetol., 52: 89-97.

Burke, R., T. Leuteritz, A. Wolf. 1996. Phylogenetic relationships of emydine turtles. Herpetol., 52: 572-584.

Bury, R. 1979. Review of the ecology and conservation of the Bog Turtle, *Clemmys muhlenbergii*.. U.S. Fish and Wildlife Serv. Spec. Sci. Rep., Wildl. No. 219: 9+.

Chase, J., K. Dixon, J. Gates, D. Jacobs, G. Taylor. 1989. Habitat characteristics, population size, and home range of the Bog Turtle (*Clemmys muhlenbergii*) in Maryland. J. of Herpet., 23(4): 356-362.

Congdon, J., A. Dunham, R. Van Loben Sels. 1993. Delayed sexual maturity and demographics of Blanding's Turtles (*Emydoidea blandingii*): Implications for conservation of long-lived organisms. Conserv. Biol., 7(4): 826-833.

Ernst, C., J. Lovich, R. Barbour. 1994. Turtles of the United States and Canada. Washington D.C.: Smithsonian Institution Press.

Feldman, C., J. Parham. 2002. A molecular phylogeny for emydine turtles: taxonomic revision and the evolution of shell kinesis. Molecular Phylogenetics and Evolution, 22(3): 388-398..

Feldman, C., J. Parham. 2001. Molecular systematics of emydine turtles.. Chelonian Conservation and Biology, 4(1): 194-198.

Gaffney, E., P. Meylan. 1988. A phylogeny of turtles. In: Benton, M.J. (Ed.): The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds. Oxford.: 157-219.

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor: University of Michigan Press.

Herman, D. 1981. Status of the Bog Turtle in the southern Appalachians. Proc. of the Non-game/Endangered Wildlife Symp., Tech. Bull. WL-5, Georgia Dept. Nat. Res., Game and Fish Div.: 77-80.

Herman, D., R. Pharr. 1986. Nat. Hist. Notes: *Clemmys muhlenbergii*. Elevation. Herpet. Review, 17: 24.

Holman, J., U. Fritz. 2001. A new emydine species from the Middle Miocene (Barstovian) of Nebraska, USA with a new generic arrangement for the species of Clemmys sensu McDowell (1964) (Reptilia: Testudines: Emydidae). Zoologische Abhandlungen Staatliches Museum für Tierkunde Dresden, 51: 331-354.

Holub, R., T. Bloomer. 1977. The Bog Turtle, *Clemmys muhlenbergii*... a natural history.. HERP: Bull. New York Herpet. Soc., 13(2): 9-23.

Morrow, J., J. Howard, S. Smith, D. Poppel. 2001. Home range and movement of the Bog Turtle (*Clemmys muhlenbergii*) in Maryland. J. of Herpet., 35(1): 68-73.

Tryon, B. 1990. Bog Turtles (*Clemmys muhlenbergii*) in the south: a question of survival. Bull. Chicago Herpet. Soc., 25: 57-66.

Tryon, B., D. Herman. 1991. Status, conservation, and management of the Bog Turtle, *Clemmys muhlenbergii*, in the southeastern United States. Proc. First Int. Symp. on Turtles and Tortoises: Conservation and Captive Breeding. Chapman Univ., Orange, California: 36-53.