Glyptemys muhlenbergii 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Testudines Emydidae

Scientific Name: Glyptemys muhlenbergii
Species Authority: (Schoepff, 1801)
Common Name(s):
English Bog Turtle
Clemmys muhlenbergii (Schoepff, 1801)
Clemmys nuchalis Dunn, 1917
Testudo muhlenbergii Schoepff, 1801
Taxonomic Notes: Previously this species was known as Clemmys muhlenbergii, under which name it appeared in IUCN Red Lists until 2008. Paraphyly of the traditional genus Clemmys (sensu McDowell, 1964) required placement of muhlenbergii and insculpta into Glyptemys.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2cd+4ce ver 3.1
Year Published: 2011
Date Assessed: 2010-08-01
Assessor(s): van Dijk, P.P.
Reviewer(s): Horne, B.D., Mittermeier, R.A., Philippen, H.-D., Quinn, H.R., Rhodin, A.G.J., Shaffer, H.B. & Vogt, R.C

The Bog Turtle, Glyptemys muhlenbergii, has lost the great majority of its suitable habitat in historic and recent times It has suffered further impact from past collection for the pet trade, fragmentation and degradation of remaining habitats, and possibly roadkill and increased predation rates; while emergence of epidemic disease, and climatic change, are recent developments of unknown but potentially severe future impact. Detailed quantitative range-wide estimates are not available, but overall reduction is likely to have exceeded 80% of habitat and 90% of individuals over the course of the 20th century, with declines stabilized in many but not all sites at present, and only localized population increases. Due to the species’ highly fragmented occurrence in habitats subject to vegetational succession, intensive management is needed to retain existing populations; creation of alternative sites is challenging; and the species’ low reproductive output (on average under four eggs/year per mature female) and relatively late maturity (about six years) means recovery is a slow gradual process at best.

Based on available data, the Bog Turtle is on the boundary between Endangered and Critically Endangered, since the generation time and thus assessment period are uncertain; at a generation time of 15 years (likely a severe underestimate), an 80% decline in total number of individuals over the past three generations (A2), as well as the past two plus the next generation (A4), appears realistic, qualifying the species as Critically Endangered by criteria A2cd and A4ce.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Glyptemys muhlenbergii occurs in disjunct populations (Iverson 1992):
  • Southeastern Appalachian foothills: western North Carolina and immediately adjoining areas of Virginia, South Carolina, Georgia and Tennessee;
  • Northwestern Pennsylvania;
  • Northeastern Maryland through SE Pennsylvania, possibly northern Delaware, much of New Jersey, southeastern New York and up the Hudson valley, western Connecticut and western Massachusetts;
  • Scattered locations in upstate New York;
  • A questionable record from Rhode Island.
Countries occurrence:
United States (Connecticut, Delaware, Georgia, Maryland, Massachusetts, New Jersey, New York, North Carolina, Pennsylvania, South Carolina, Tennessee, Virginia)
Additional data:
Number of Locations:460Continuing decline in number of locations:Yes
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Population densities for Bog Turtle occurrences have been reported ranging from one to 213 turtles per hectare. Given the small size of most sites inhabited by bog turtles (average of about one hectare in the south, variable size in the northern population), individual sites rarely comprise more than 40 adult individuals (Chase 1989, Mitchell 1991). Exchange of individuals between local sites has not been reported. Juveniles represent substantial proportions of the population in some sites (MD: Chase et al. 1989; NY: Warner 2005), but are rarely encountered at other sites (NJ: Arndt, 1986).

Northern populations (Massachusetts to Maryland) were determined to have declined in range and numbers by over 50% during the period 1977–1997, with 360 sites of occurrence remaining, of which 95% are on privately-held lands (FWS 2001).

Extensive surveys of southern population in the 1980s identified 96 sites of occurrence, of which only 52 were considered viable; about 85% of occurrences were on private lands (Tryon and Herman 1991).

Beth Walton (Ph.D thesis, 2006) analysed habitat trends in Ashe County, North Carolina, and concluded that 2–3% of suitable habitat remains.

Current Population Trend:Unknown
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:Glyptemys muhlenbergii is a near-exclusive inhabitant of marsh and swamp habitat away from large water bodies; typical habitats include stream-head sedge meadows, spring-fed sphagnum bogs, fens, and open shrubby swamps, and nearby small streams. In contrast to its vernacular name, the Bog Turtle generally avoids strongly acidic bogs (pH <5.5). As Ernst and Lovich (2009) noted, these are often ecologically ephemeral habitats due to vegetation succession. Bog Turtles have small home ranges, at the order of fractions of a hectare, but moderate-distance movements have been reported travelling both overland and using small streams (Carter et al. 2000, Pittmann et al. 2009).

Bog Turtles are opportunistic omnivores, feeding on a great variety of invertebrate and small vertebrate animal prey as well as seeds, fruits and occasionally other parts of a range of herbs, grasses, sedges and shrubs (see review by Ernst and Lovich 2009).

Bog Turtles can reach up to 11.5 cm carapace length (CL) in males, and 9.6 cm CL in females. Size and age at maturity has been reported as about 7–8 cm CL and 4–6 years in males, and half a cm larger and likely a year later in females. Females normally produce a single clutch of 3–4 (range 1–6) eggs; not all females reproduce in any given year. Hatchlings measure on average 26–28 mm CL. Longevity may exceed 30 years; generation time has not been calculated (see review by Ernst and Lovich 2009).

Systems:Terrestrial; Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: Glyptemys muhlenbergii is protected from exploitation under the Endangered Species Act. Nevertheless, it is still in small but high demand in the pet trade.

Threats [top]

Major Threat(s):

Much Bog Turtle habitat has been destroyed by drainage and conversion in recent centuries as its wetland habitat is generally located in optimal agricultural soils and landscapes, processes that continue to some extent into the present. Being often located at the lower edges of intensively farmed lands, sedimentation and agrochemical run-off into wetland habitat is an issue.

The Bog Turtle's range is localized, both at the geographic scale (scattered areas of occurrence with extensive areas where the species is absent from suitable habitat) and at the local landscape scale, where suitable habitat is localized in a mosaic of other habitat types. Fragmentation of habitat has continued with agricultural intensification and optimization, and infrastructure, residential and industrial development.

Within protected wetland habitat areas, vegetation succession by both native plants and invasives can reduce the suitability of wetlands to bog turtles.

While fully protected throughout its range, the Bog Turtle remains in small but high demand in the pet trade by virtue of its small size, attractive colouration and reputed rarity. Because of the small home range size and sensitivity of its wetland habitat, disturbance and habitat trampling are greater concerns for this species than most other turtles.

Road mortality and increased predation of eggs and hatchlings from subsidized raccoons has been indicated. The impact of global warming, under various predicted scenarios, on hydrology and habitat supporting the Bog Turtle has not yet been evaluated in detail but warrants concern.

Reports of die-offs, presumed related to disease, emerged in 2009; the extent and severity of epidemic disease has not been documented range-wide, but Brenner et al. (2002) and Carter et al. (2005) reported incidence of bacterial and mycoplasma potential pathogens in NC and VA populations.

Conservation Actions [top]

Conservation Actions: Glyptemys muhlenbergii (as Clemmys muhlenbergii) is federally protected under the Endangered Species Act (ESA) since 4th November 1997, with the northeastern populations (Maryland to Massachusetts) listed as Threatened, and the populations of GA, NC, SC, TN and VA listed as Threatened by Similarity of Appearance. The species is protected by legislation or regulation in each of the States where it occurs. It is included in CITES Appendix I, precluding all international commercial trade. A recovery plan was compiled for the northern population in 2001.

A number of sites inhabited by Bog Turtles are under government or NGO ownership and management, while owners of lands where bog turtles occur are engaged where possible to manage bog turtle sites optimally. Due to the high risk of illegal collection, localities are generally held in secrecy.

Key conservation measures required focus on safeguarding remaining habitat from destruction, degradation, pollution and conversion, managing habitat with regard to vegetation succession and invasives (through grazing, winter burning, or other measures), and landscape planning and management measures to prevent and reverse fragmentation of populations. Further population monitoring and surveys, research on conservation biology, climatic change impacts and disease issues, law enforcement action to address any illegal take and trade, and stakeholder outreach, all need to accompany these habitat measures.

Genetic study is needed to evaluate phylogeography with regard to the two main distribution areas, and to inform intensive management options including head-starting and translocation. 

Extensive literature exists detailing population data, threats and recommended conservation measures; useful entry points into the literature are USFWS (2001), NatureServe (2005) and Ernst and Lovich (2009).

Errata [top]

Errata reason: An errata assessment is required to generate a revised PDF without the range map which had been included in error; no range map was available when this assessment was originally published.

Classifications [top]

5. Wetlands (inland) -> 5.1. Wetlands (inland) - Permanent Rivers/Streams/Creeks (includes waterfalls)
5. Wetlands (inland) -> 5.3. Wetlands (inland) - Shrub Dominated Wetlands
5. Wetlands (inland) -> 5.4. Wetlands (inland) - Bogs, Marshes, Swamps, Fens, Peatlands
suitability:Suitable  major importance:Yes
5. Wetlands (inland) -> 5.7. Wetlands (inland) - Permanent Freshwater Marshes/Pools (under 8ha)
1. Land/water protection -> 1.1. Site/area protection
2. Land/water management -> 2.1. Site/area management
2. Land/water management -> 2.2. Invasive/problematic species control
2. Land/water management -> 2.3. Habitat & natural process restoration
3. Species management -> 3.2. Species recovery
3. Species management -> 3.3. Species re-introduction -> 3.3.1. Reintroduction
3. Species management -> 3.4. Ex-situ conservation -> 3.4.1. Captive breeding/artificial propagation
4. Education & awareness -> 4.3. Awareness & communications
5. Law & policy -> 5.4. Compliance and enforcement -> 5.4.2. National level
5. Law & policy -> 5.4. Compliance and enforcement -> 5.4.3. Sub-national level

In-Place Research, Monitoring and Planning
  Systematic monitoring scheme:Yes
In-Place Land/Water Protection and Management
  Conservation sites identified:Yes, over entire range
  Occur in at least one PA:Yes
  Area based regional management plan:Yes
  Invasive species control or prevention:Yes
In-Place Species Management
  Harvest management plan:No
  Successfully reintroduced or introduced beningly:No
  Subject to ex-situ conservation:Yes
In-Place Education
  Subject to recent education and awareness programmes:Yes
  Included in international legislation:Yes
  Subject to any international management/trade controls:Yes
1. Residential & commercial development -> 1.1. Housing & urban areas
♦ timing:Past, Likely to Return ♦ scope:Minority (<50%) ♦ severity:Very Rapid Declines ⇒ Impact score:Past Impact 

1. Residential & commercial development -> 1.2. Commercial & industrial areas
♦ timing:Past, Likely to Return ♦ scope:Minority (<50%) ♦ severity:Very Rapid Declines ⇒ Impact score:Past Impact 

11. Climate change & severe weather -> 11.1. Habitat shifting & alteration
♦ timing:Ongoing ♦ scope:Whole (>90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Medium Impact: 7 

11. Climate change & severe weather -> 11.2. Droughts
♦ timing:Ongoing ♦ scope:Minority (<50%) ♦ severity:Causing/Could cause fluctuations ⇒ Impact score:Low Impact: 5 

2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.2. Small-holder farming
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Medium Impact: 6 

2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.3. Agro-industry farming
♦ timing:Ongoing ♦ scope:Minority (<50%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Low Impact: 5 

2. Agriculture & aquaculture -> 2.3. Livestock farming & ranching -> 2.3.2. Small-holder grazing, ranching or farming
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Causing/Could cause fluctuations ⇒ Impact score:Medium Impact: 6 

2. Agriculture & aquaculture -> 2.3. Livestock farming & ranching -> 2.3.3. Agro-industry grazing, ranching or farming
♦ timing:Ongoing ♦ scope:Minority (<50%) ♦ severity:Causing/Could cause fluctuations ⇒ Impact score:Low Impact: 5 

4. Transportation & service corridors -> 4.1. Roads & railroads
♦ timing:Ongoing ♦ scope:Whole (>90%) ♦ severity:Slow, Significant Declines ⇒ Impact score:Medium Impact: 7 

5. Biological resource use -> 5.1. Hunting & trapping terrestrial animals -> 5.1.1. Intentional use (species is the target)
♦ timing:Past, Unlikely to Return ♦ scope:Majority (50-90%) ♦ severity:Rapid Declines ⇒ Impact score:Past Impact 

6. Human intrusions & disturbance -> 6.3. Work & other activities
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Negligible declines ⇒ Impact score:Low Impact: 5 

8. Invasive and other problematic species, genes & diseases -> 8.1. Invasive non-native/alien species/diseases -> 8.1.1. Unspecified species
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Unknown ⇒ Impact score:Unknown 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

1. Research -> 1.1. Taxonomy
1. Research -> 1.2. Population size, distribution & trends
1. Research -> 1.3. Life history & ecology
1. Research -> 1.5. Threats
1. Research -> 1.6. Actions
2. Conservation Planning -> 2.1. Species Action/Recovery Plan
3. Monitoring -> 3.1. Population trends
3. Monitoring -> 3.4. Habitat trends

Bibliography [top]

Ernst, C.H. and Lovich, J.E. 2009. Turtles of the United States and Canada. Second edition. Johns Hopkins University Press, Baltimore.

IUCN. 2011. IUCN Red List of Threatened Species (ver. 2011.1). Available at: (Accessed: 16 June 2011).

IUCN. 2016. The IUCN Red List of Threatened Species. Version 2016-1. Available at: (Accessed: 30 June 2016).

Iverson, J.B. 1992. A Revised Checklist with Distribution Maps of the Turtles of the World. Privately published, Richmond, Indiana.

NatureServe (Hammerson, G., Wilkinson, A.M., Master, L., & Whitlock, A.). 2005. Glyptemys muhlenbergii - (Schoepff, 1801) Bog Turtle. (Accessed: August 3, 2010).

U.S. Fish and Wildlife Service (prepared by M. Klemens). 2001. Bog Turtle (Clemmys muhlenbergii), Northern Population, Recovery Plan. US FWS, Hadley, MA.

Citation: van Dijk, P.P. 2011. Glyptemys muhlenbergii. In: (errata version published in 2016) The IUCN Red List of Threatened Species 2011: e.T4967A97416755. . Downloaded on 17 January 2017.
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