The bog turtle is one of the smallest turtles in North America. Bog turtles in the northern part of the range are generally less than 100 millimeters (4 inches) in length, while turtles father south reach sizes of up to 115 millimeters (4.5 inches) (USFWS 2001).
While more than 20 extant populations are currently known in New York, significant threats to these populations exist. Many of the populations are comprised of few individuals and the habitats that support them are often small in size. While additional bog turtle sites will probably be discovered, some of these may be determined to be part of existing metapopulations and most new sites are expected to have at least some threats.
Survey efforts have recently been aimed at marking individual turtles at multiple sites to obtain population data and it is too early to determine short-term trends. The best populations are likely to contain fewer than 100 individuals and most are likely to have far fewer individuals. Twelve populations have between 10 and 92 individuals documented from them and it is probable that an unknown number of additional turtles are also present. Far fewer individuals are known from the remaining 73 populations. Four populations are known to be extirpated and it is likely that many of the populations with records from the 1970s or earlier are extirpated as well.
A spotty distribution and specialized habitat requirements make this species vulnerable to local extirpation. Declines are primarily due to loss, degradation, and fragmentation of habitat. Road mortality, an increase in subsidized predators, natural succession, and the expansion of invasive exotic vegetation are associated with these primary threats. Illegal collecting for the pet trade is also a direct threat to populations.
The control of exotic species and natural succession is warranted at a number of sites. The control of subsidized predators may be desirable if predation of eggs and juveniles is unusually high.
Additional research on population size, intra-habitat use, and inter-habitat movements and migration is needed.
In New York, bog turtles occur in open-canopy wet meadows, sedge meadows, and calcareous fens. The known habitat in the Lake Plain region of the state includes large fens that may include various species of sedges, such as slender sedge (Carex lasiocarpa), bog buckbean (Menyanthes trifoliata), mosses (Sphagnum spp.), pitcher plants (Sarracenia sp.), scattered trees, and scattered shrubs. In the Hudson River Valley, bog turtle habitats may be isolated from other wetlands or they may exist as part of larger wetland complexes. These wetlands are often fed by groundwater and the vegetation always includes various species of sedges. Other vegetation that is frequently found in southern New York bog turtle sites includes shrubby cinquefoil (Potentilla fruticosa), grass-of-parnassus (Parnassia glauca), mosses (Sphagnum spp.), horsetail (Equisetum sp.), scattered trees such as red maple (Acer rubrum), red cedar (Juniperus virginianus), and tamarack (Larix laricina), and scattered shrubs such as willows (Salix spp.), dogwood (Cornus spp.), and alder (Alnus spp.).
Although historical records come from a larger area of the state, extant populations are known from small portions of six counties in the lower Hudson River Valley (Columbia, Dutchess, Putnam, Ulster, Orange, and Sullivan). There are a few records of bog turtles in Westchester County from the 1990s, but it is not known if any extant populations remain in this county. Extant bog turtle populations are also known from a small portion of Oswego County and single locations in Seneca County and Wayne County.
The bog turtle occurs in twelve states in the United States and has a discontinuous distribution throughout its range. The northern portion of the range includes central and eastern New York, western Massachusetts, western Connecticut southward to Pennsylvania, New Jersey, Maryland, and northern Delaware. The southern part of the species range includes southeastern Virginia, western and central North Carolina, extreme western Tennessee, and western South Carolina and Georgia. There is a large hiatus of about 250 miles between the northern population and the southern population. Bog turtles occur from sea level to 4,200 feet in elevation in the Appalachians, although populations are usually found below 800 feet in the north. Bog turtles are believed to be extirpated in western Pennsylvania and in the Lake George region of New York.
This is a small turtle with adult carapace (upper shell) lengths ranging from 3 to 4.5 inches in length. The carapace is light brown to black, may have a faint yellowish or reddish pattern visible on the large scutes, and is strongly sculptured with growth lines visible, except in very old adults where the growth lines may be worn smooth. An inconspicuous keel is also present along the dorsal midline of the carapace. The plastron (lower shell) is mainly dark brown to black and may also have large yellowish or reddish blotches present. The head is black with two large orange or yellow blotches above and behind the tympanum (ear) on each side of the head.
The small size and normally orange (sometimes yellow) head blotches are split into two parts and are characteristic of the species.
The diet of the bog turtle has been reported to include insects, plants, frogs, and carrion (Bury 1979). Fecal samples from Massachusetts have contained spiders (Aracnida), beetles (Coleoptera), millipedes (Diplopoda), flies (Diptera), snails (Gastropoda), ants (Hymenoptera), moths (Lepidoptera), dragonflies (Odonata), caddisflies (Trichoptera), and plant fragments (Klemens 1993). Slugs (Arion subflavus) have been reported as food items in southeastern New York, while slugs and crayfish have been reported as food items in North Carolina (USFWS 2001).
Bog turtles are diurnal and are normally active during the early morning to mid-day hours, often in the direct sun. This species hibernates communally and shows site-fidelity to hibernacula.
The time of year you would expect to find Bog Turtle present and reproducing in New York.
Glyptemys muhlenbergii (Schoepff, 1801)
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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.
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Herman, D.W. 1981. Status of the bog turtle in the southern Appalachians. pp. 77-80. In R.R. Odom and J.W. Guthrie (eds.). Proceedings of the nongame and endangered wildlife symposium. GA Dept. of Nat. Res., Tech. Bull. WL5, 179 pp.
Holman, J. A., and U. Fritz. 2001. A new emydine species from the Medial 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 fur Tierkunde Dresden 51(19):321-344.
Kiviat, E. 1978. Bog turtle habitat ecology. Bulletin of the Chicago Herpetological Society. 13(2):29-42.
Klemens, M. W. 1993. Amphibians and reptiles of Connecticut and adjacent regions. State Geological and Natural History Survey of Connecticut, Bulletin 112. xii + 318 pp.
Landry, J.L. 1979. A bibliography of the bog turtle, Clemmys muhlenbergii (biology, ecology and distribution). Smithsonian Herpetological Information Service, no. 44:1-21.
Lovich, J. E., C. H. Ernst, R. T. Zappalorti, and D. W. Herman. 1998. Geographic variation in growth and sexual size dimorphism of bog turtles (Clemmys muhlenbergii). American Midland Naturalist 139:69-78.
Lovich, J. E., et al. 1991. Relationships among turtles of the genus Clemmys (Reptilia, Testudines, Emydidae) as suggested by plastron scute morphology. Zoologica Scripta 20:425-429.
McDowell, S. B. 1964. Partition of the genus Clemmys and related problems in the taxonomy of the aquatic testudinidae. Proc. Zool. Soc. London 143:239-279.
Merkle, D. A. 1975. A taxonomic analysis of the Clemmys complex (Reptilia: Testudines) utilizing starch gel electrophoresis. Herpetologica 31:162-166.
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.
Morrow, J. L., J. H. Howard, S. A. Smith, and D. K. Poppel. 2001. Habitat selection and habitat use of the bog turtle (Clemmys muhlenbergii) in Maryland. Journal of Herpetology 35:545-552.
Morrow, J. L., J. H. Howard, S. A. Smith, and D. K. Poppel. 2001. Home range and movements of the bog turtle (Clemmys muhlenbergii) in Maryland. Journal of Herpetology 35:68-73.
New York Natural Heritage Program. 2019. New York Natural Heritage Program Databases. Albany, NY.
New York Natural Heritage Program. New York State Department of Environmental Conservation. 625 Broadway, 5th floor. Albany, NY 12233-4757. (518) 402-8935.
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Reilly, E.M., Jr. 1958. Turtles of New York. New York State Conservationist.
U.S. Fish and Wildlife Service (USFWS). 2000. Bog turtle (Clemmys muhlenbergii), northern population, recovery plan, agency draft. Hadley, Massachusetts. viii + 90 pp.
U.S. Fish and Wildlife Service (USFWS). 29 January 1997. Proposed rule to list the northern population of the bog turtle as threatened and the southern population as threatened due to similarity of appearance. Federal Register 62(19):4229-4239.
U.S. Fish and Wildlife Service (USFWS). 4 November 1997. Final rule to list the northern population of the bog turtle as threatened and the southern population as threatened due to similarity of appearance. Federal Register 62(213):59605-59623.
United States Fish and Wildlife Service. 2001. Bog turtle (Clemmys muhlenbergii), northern population, recovery plan. Hadley, Massachusetts. 103 pp.
Information for this guide was last updated on: July 4, 2005
Please cite this page as:
New York Natural Heritage Program. 2019. Online Conservation Guide for Glyptemys muhlenbergii. Available from: https://guides.nynhp.org/bog-turtle/. Accessed April 18, 2019.