The bog turtle (Glyptemys muhlenbergii) is a turtle that is endemic to the eastern United States. It is the only turtle protected under the Federal Endangered Species Act and is considered threatened at the federal level and endangered in some states. It is illegal to collect or keep a bog turtle or its eggs. It is the smallest species of turtle in North America (and one of the smallest in the world). To the untrained eye, the bog turtle looks similar to the Painted turtle and the Spotted turtle because all three have similar patterns on their skin. One difference between it and the spotted turtle is that the bog turtle does not have any coloration on the upper shell but the spotted does. Due in part to its small size and unique characteristics, it is often in high demand in the black market pet trade. The Bronx Zoo was the first place to sucessfully breed bog turtles in captivity and has been doing so since 1973.

Description

The bog turtle weighs approximately when fully grown. A full-grown male is in length, while the females are . Hatchlings are about long. The head is a dark brown color that matches the shell; however, they have a bright yellow, orange, or red spot on each side of their neck. Bog turtles are dark in color with an orange-red wash on the inside of the legs of some individuals. The carapace is domed and rectangular, often with prominent rings on the scutes. In some older individuals, and those that burrow frequently in coarse substrate, the shell may be smooth. Although generally black, a chestnut sunburst pattern in each scute is sometimes present on the carapace. The plastron is hingeless, with a pattern of cream and black blotches. The plastron of the male is slightly concave while the female's is flat. The male's tail is longer and thicker than the female's.

Taxonomy

The bog turtle was first discovered and scientifically identified by Gotthilf Heinrich Ernst Muhlenberg, a self-taught colonial botanist and clergyman, in Lancaster County, Pennsylvania. Muhlenberg, who named more than 150 North American plant species, was conducting a survey of the flora of Lancaster County, when he accidentally discovered the small turtle.

In 1801, the bog turtle was named Clemmys muhlenbergii, or Muhlenberg's tortoise, in honor of Muhlenberg. However, the species' common name was changed to bog turtle in 1956.

Distribution and Habitat

Bog turtles congregate in colonies in southwestern Vermont, northern New York, northeastern Ohio, and south to the Appalachian Mountains in Georgia and South Carolina. They prefer calcareous wetlands including meadows, bogs, marshes, and spring seeps that have not only wet areas but dry regions as well. Bog turtles can sometimes even be found in cow pastures or beaver complexes. Small differences in climate that result from the varied humidity aid in the incubation of eggs and thermoregulation. Deep, muddy soil allows bog turtles to survive extreme weather changes and predators. Spring seeps and groundwater springs provide optimum locations for hibernation during winter. Also, the prefered habitat size is relatively the same for both males and females, averaging only about 1.28 hectares (3.16 acres).

Rushes, tussock sedge, cattails, jewelweed, sphagnum, and various native true grasses are a few of the plants that are commonly found in the bog turtle’s habitat. Willows, red maple, and alder are examples of trees and shrubs found in such habitats. It is important for the bog turtle’s habitat to have an open canopy because they spend a considerable amount of their lives basking in the sunlight. An open canopy allows a copious amount of sunlight to reach the ground level where the turtles dwell so that the bog turtles can manage their metabolic processes through thermoregulation. The incubation of eggs requires appropriate levels of sunlight too.

The ideal bog turtle habitat is early successional. Early successional habitats are without mature trees that block sunlight from reaching the ground level and prevent the subsistence of the turtles. Unfortunately, erosion and runoff of nutrients into the wetlands accelerate succession. Human-stimulated successions have engendered the eradication of bog turtles from areas where they would normally survive as well.

Northern and Southern Ranges

The northern community of bog turtles makes its home in states as far north as Connecticut and Massachusetts and as far south as Maryland. It is the bigger of the two but the bog turtles in these areas live in very scattered ranges. They live at low altitudes, often under . This group is known to have less than 500 bog turtle sites left, a number that is without a doubt decreasing.The southern range of bog turtles is much smaller and exists in states including North Carolina, South Carolina, Georgia and Tennessee. They are even more scattered than the northern population but live at higher altitudes, anywhere up to .

Behavior

General

The bog turtle is active exclusively during the daytime. During colder days they spend much of their time in dense underbrush, underwater, or buried in the mud. This makes them very difficult to locate and to estimate their population. However, on warmer days their activities include scavanging, mating (during early spring), and basking in sunlight. The temperature that the bog works to achieve when basking is usually 84 to 94 degrees Fahrenheit ( 29 to 34 degrees Celsius). At night, the bog turtles bury themselves in soft nests either made of soil or located in areas of densly rooted vegitation.Its only defense when threatened by a predator is to bury itself in mud and hide.

Hibernation

The bog turtle usually spends mid October to late March in hibernation. They either hibernate alone or in small collections. These communities number up to twelve turtles, sometimes containing other similar species such as the spotted turtle. Bog turtles try to find an area of dense soil, like a strong root system, for protection during their dormant period.

Movement

Turtles, like most other reptiles, move for four reasons: feeding, mating, basking in sunlight, and protection. The bog turtle may perform all four movements in one day: traveling to eat food, reproduce with another individual, take in the sun, and burrow from a predator. However, moving for protection is becoming increasingly more common among bog turtles. Bog turtles, when their immediate environment becomes unsuitable, will travel to a new location, perhaps miles away. This is called an extrapopulation movement and for bog turtles the distance it must travel for its journey to be classified as such is about a third of a mile (half a kilometer). They may do this because its former area no longer sustained enough food or mates. Perhaps an inadequate amount of sunlight reached them through the vegetation in the surrounding area or the area no longer contains suitable nesting material. For whatever reason, the bog turtle may perform an extrapopulation movement several times throughout its life. On a day to day basis, these turtles move very little, often just basking and hopeing upon chance prey. Male bog turtles move slightly more than females, on average, perhaps because they are the ones seeking out companions during mating season. Overall though, the bog turtle moves far less throughout their lives than most other turtles.

Threats

Bog turtles are often preyed upon by a variety of mammals and birds including raccoons, skunks, foxes and dogs. In addition to natural threats the turtles are also susceptible to man made threats and invasive plants.

Man made threats to the bog turtle include the destruction of their habitat and illegal collection, often for international pet trade. As a bog turtle's habitat deteriorates, it relocates to a new wet meadow, usually created by fires, beavers, or other variables. The development of new neighborhoods and roadways obstructs this movement and inhibits the establishment of new populations.Although the collection of bog turtles is illegal and the U.S. Fish and Wildlife Service has listed it as threatened since 1997, there are many cases of the turtle being taken from its habitat. Pesticides, run-off and industrial discharge are all harmful to the habitat and food supply of the bog turtle and therefore the turtle itself. The population of bog turtles in North Carolina alone has decreased by 50% between the late 1970s and 1997.

Bog turtles are also threatened by the invasion of non-native plants into their habitat. Although there are various plants that disrupt the ecosystem, the two most often found are the purple loosestrife (above) and reed plants.These grow thick and tall and are believed to constrict the native plant's root systems. The bog turtle therefore loses a certain percentage of its food and protection because of these plants.

Diet

Bog turtles are omnivorous and are known to eat aquatic plants (such as duckweed and water lettuce), seeds, berries, worms, snails, slugs, frogs, insects, and in some cases snakes. They feed only during the daytime, but rarely during the hottest hours of the day. Although uncommon, the turtles will eat carrion.

Reproduction

Bog turtles mate in the spring after emerging from hibernation. The male turtles tend to bite and nudge the female turtles’ heads during the courtship ritual. The mating session of the bog turtle usually lasts anywhere from five to 20 minutes. Nesting takes place during the months of May, June, and July. Most females lay their eggs in sedge tussocks or on sphagnum moss that are both located in dryer areas of a bog and receive an abundant amount of sunlight. Like most other species of turtle, the bog turtle constructs its nest using its hind feet and claws. The majority of bog turtle eggs are laid in June. Pregnant females lay one to six eggs per clutch, and lay only one clutch per year. However, female bog turtles do not breed every year, which is another reason why the species' population is depleted. Also, a large percentage of bog turtle eggs are infertile and do not survive. The eggs are white, flexible, and average around 3 cm in length. After the eggs are laid, they are left by the female bog turtle and undergo an incubation period that last for 45–65 days. In colder climates, however, eggs may incubate all winter and hatch in the spring when there is a more substantial food supply. During the incubation period, the eggs are vulnerable and often fall prey to a number of mammals and birds. It is unknown if the gender of the bog turtle offspring is temperature-dependent Within the first years of development, the turtles have a tendency to grow at a rapid rate. Both male and female bog turtles reach sexual maturity at anywhere between 4–10 years of age.

Longevity

Bog turtles live 20 to 30 years, remaining almost exclusively in the same wetlands where they hatched. Many bog turtles do not live this long however, because they are threatened by many natural and man made factors. Some of the oldest known are currently in The Bronx Zoo's on-display population; several of its turtles are 35 years old or more.

References