Clemmys muhlenbergii
bog turtle

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, Lovich, and Barbour, 1994; Harding, 1997; Herman, 1981)

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, Lovich, and Barbour, 1994; Harding, 1997; Herman and Pharr, 1986; Tryon, 1990)

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, Lovich, and Barbour, 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, Lovich, and Barbour, 1994; Harding, 1997)

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

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, Lovich, and Barbour, 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)

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)

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

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.

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.

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, Dunham, and Van Loben Sels, 1993; Ernst, Lovich, and Barbour, 1994; Harding, 1997; Herman, 1981; Holub and Bloomer, 1977; Tryon and Herman, 1991; Tryon, 1990)

Recent taxonomic studies of turtles in the subfamily emydinae show that bog turtles are most closely related to wood turtles (Glyptemys insculpta, previously Clemmys 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, Leuteritz, and Wolf, 1996; Ernst, Lovich, and Barbour, 1994; Feldman and Parham, 2001; Feldman and Parham, 2002; Gaffney and Meylan, 1988; Holman and Fritz, 2001)