Species Description
Bog Turtles are the smallest North American Turtle, and although the shell of the largest Bog Turtle ever documented 4.5 inches long, most are less than 4 inches. They have a prominent yellow or orange patch on each side of their head, while the rest of their skin is dark brown, or almost black. Some Bog Turtles also have a faint orange or reddish hue on their legs between their scales. The top of their shell, called a carapace, is also dark brown, and each side forms a straight edge that gives the turtle an elongated appearance when viewed from the top. The scutes (armored plates) of the carapace often feature circular rings that correspond to the age of younger turtles, but as the shells of older turtles wear down the rings are polished smooth. On some individuals, the scutes are also highlighted with a chestnut or sunburst coloration in varying patterns. A Bog Turtle’s plastron (bottom of the shell) has dark blotches separated by yellow, but sometimes the yellow is greatly reduced or the plastron appears solid black, especially on juveniles.
Taxonomy
The Bog Turtle shares its genus, Glyptemys, with only one other species; the Wood Turtle (G. insculpta). First classified as Testudo muhlenbergii in 1801, the species was reclassified several times, before eventually landing in the Clemmys genus with Spotted Turtles and, at the time, Wood Turtles, where it stayed for almost 100 years. Wood and Bog Turtles were moved their own genus, Glyptemys, in 2001. In some areas they are also called mud turtles, marsh turtles, yellowheads, or snappers, although it should be noted that several of those names are applied to nearly every freshwater turtle species.
Distribution
Bog Turtles occur in scattered populations throughout the eastern United States within two separate broad geographic areas. The more southern grouping of Bog Turtles used to be widespread within the Blue Ridge Mountains, from northeastern Georgia, through eastern North Carolina, and into southeastern Virginia. Separated from the southern populations by more than 250 miles, the Northern Bog Turtles are found from eastern Pennsylvania and southern New York into western Massachusetts down to northeastern Maryland. Additional disjunct populations are also found in central New York, south of Lake Ontario, and potentially in extreme northwestern Pennsylvania where the species may be extirpated. Additional remnant populations may remain undetected in remote areas virtually anywhere in the areas between known areas occupied by Bog Turtles.
Habitat
In northern portions of their range, Bog Turtles usually occur low-lying, sunny wetlands surrounded by woodlands, but in the south, many of their populations are found in highly mountainous areas along the Blue Ridge Mountains where they occupy wetlands nestled within isolated mountain hollows. Regardless of elevation and region, calcareous fens, acidic sphagnum bogs, beaver complexes, sedge meadows with emergent vegetation, and pasture wetlands make up the bulk of their habitat. In most cases, sphagnum or other mosses are a prominent feature in their habitat, and there is slow, yet continuous water flow seeping through the soils. To forage, bask, nest, and overwinter, Bog Turtles need a variety of microhabitats in the same wetland throughout the year, including mucky substrates, dry patches, and at some areas that periodically flood.
Bog Turtles hibernate submerged in their wetlands, typically in densely vegetated ares within narrow channels or tunnels through the moss and soil substrate, or under shrub hummocks in the spaces between roots. If available, they may also overwinter in the highly oxygenated narrow channels or rivulets stemming from natural springs that, in some cases, are the primary source of water for their wetlands.
Historically, natural succession maintained open habitat within wetlands, aided by beaver activity and deer browse. Whenever canopy cover became prohibitively dense or if beavers raised water levels too high, Bog Turtles would shift to other nearby wetlands, or different areas within the same wetland. With their habitat highly fragmented today, Bog Turtles are not able to easily move between wetlands, so active management is needed to maintain the open character of Bog Turtle wetlands. Carefully planned grazing by livestock can be used to recreate natural processes that maintain the open character of wetlands inhabited by Bog Turtles.
Movement and Home Range
Bog Turtles are active from April through September. Out of all turtles in the Emydinae subfamily, which also contains Spotted, Wood, and Blanding’s Turtles, Bog Turtles have the smallest average home range sizes and dispersal distances. Typical home ranges, where Bog Turtles spend the vast majority of their time, range from just over one acre up to about five acres. Many will spend their entire lives in a single wetland, but in some areas, a small percent of Bog Turtles regularly travel through forested habitat to other wetlands more than 200 yards away.
In at least one instance, a young male Bog Turtle traveled over 1.6 miles before researches lost track of its location. Generally speaking, Bog Turtles tend not to disperse to different wetlands except in response to habitat changes caused by disturbance or natural succession, in which case they shift their territories to habitat within the same wetland complex, or disperse through forested habitat in search of different wetlands.
Diet
Similar to other semiterrestrial turtles, Bog Turtles can forage on both land and in water, and have a highly varied diet. The results of studies vary in terms of whether Bog Turtles feed primarily on plant or animal matter, but their diet includes seeds, beetles, weevils, millipedes, caddisfly and dragonfly larvae, snails, crayfish, amphibian larvae, pondweed, watercress, skunk cabbage, and various fruits. There appears to be variation in the diet of Bog Turtles studied in different geographic regions, suggesting the species is generalist omnivore and will take advantage of locally available sources of food.
Reproduction
The species has low reproductive rates, laying on average, three to five eggs in one clutch each year, and sometimes as few as only one egg. Eggs are often laid in moss hummocks within the same wetlands where adults forage and overwinter. The survival rates of nests and hatchlings are low, with mortality rates dropping each year until the turtle’s shells are strong enough to protect them from most predators. They mature in eight to eleven years and probably live into their 50s with some regularity, but may live longer, similar to Spotted and Turtles.
Conservation Concerns
The degradation of wetlands and fragmentation of forested habitat greatly threaten Bog Turtles. Wetlands habitat for Bog Turtles can be impaired a number of ways, from nutrient pollution from farm fields and septic runoff, invasive plants, ATV traffic, and the deliberate draining and filling of waters. Because Bog Turtles need good sun exposure within their wetlands, open bogs colonized by invasive shrubs such as glossy buckthorn can overrun their habitat and limit basking opportunities. Other invasive plants, such as common reed purple loosestrife, can also degrade the Bog Turtle’s nesting habitat.
Historically, if an entire wetland or portion of a wetland became unsuitable to Bog Turtles, they would shift their movements to nearby wetlands by moving through forested environments. Today, many Bog Turtle wetlands are separated by vast open landscapes and highways that impede the Bog Turtle’s limited ability to disperse, with those that try at risk of being crushed by motor vehicles.
With remaining populations of Bog Turtles dwindling in numbers and separated by vast distances, the species was federally listed as threatened in 1997, and is threatened or endangered in every state the species occurs.