The bog turtle is one of North America’s smallest turtle species is also one of its rarest.
With conspicuous orange blotches on each temple, the diminutive bog turtle (Glyptemys muhlenbergii) is one of the most distinctive turtles native to North America. Sometimes referred to as Muhlenberg’s turtle, the bog turtle is also one of the rarest and possibly most endangered. Although the bog turtle's range includes at least 10 states along the Atlantic seaboard of the United States, actual habitat areas are generally fairly small and distribution is spotty. Fortunately there are a handful of captive-breeding groups, and their captive-bred bog turtles have proven adaptable and hardy. Individual lifespan of the bog turtle in the wild is not known for certain, but due to natural and human-influenced threats, it is thought to be less than the 30-odd years documented in captivity.
The bog turtle is one of North America’s smallest turtle species is also one of its rarest.
Seldom exceeding 4 inches straight carapace length, the bog turtle is one of the smallest turtle species in the world. Aside from the head coloration, the bog turtle is rather nondescript in color and pattern. With a very dark brown to almost black base color, the carapace is somewhat marbled or streaked with deep red and brown. The ventral surface is basically black with some tan or beige areas near the center of the plastron. Legs and other soft parts are dark brown to black with red or orange edging on the leg scales.
Sexual dimorphism is moderate in G. muhlenbergii. Male bog turtles are slightly larger (by a fraction of an inch) than female bog turtles, but the sexes are not significantly different in overall shape. The plastron of the male is moderately concave to facilitate breeding, while the plastron of the female is flat. Males also have a longer, thicker tail than the female, with the vent closer to the tip.
Bog Turtle Natural Habitats
Like the common name suggests, the typical habitat of G. muhlenbergii consists of bogs, swamps and shallow marshes. Areas with a combination of wet and dry, open and canopied, with low-growing vegetation and soft substrates, are preferred. Shallow, clear, slow-flowing water is always present in a bog turtle habitat, but the nature of the habitat itself would seem to contribute to the pressure on the species’ survival. Bogs and marshes are generally considered ephemeral environments, meaning that they are a natural transitional stage between one type of habitat and another. As wetlands slowly drain, they transition through the bog stage ultimately to a drier habitat that is unsuitable for bog turtle survival. This, coupled with pressures induced by humans, has caused the continuing elimination of bog turtle habitat in many parts of its historic range.
Bog turtles are known to share their habitat with several other North American turtle species, including spotted turtles (Clemmys guttata), common musk turtles (Sternotherus odoratus), eastern mud turtles, (Kinosternon s. subrubrum), North American wood turtles (Glyptemys insculpta), eastern box turtles, (Terrapene c. Carolina) and occasionally Blanding’s turtles (Emys blandingii). The bog turtle is primarily active during daylight hours, but it has occasionally been observed breeding or foraging just prior to dawn or shortly after sundown. Seasonally, they are most active in spring and fall, spending the hottest part of summer aestivating and the colder parts of winter brumating.
Two Bog Turtle Populations
There are two separate bog turtle populations. The northern population occurs in southwest Massachusetts southward to northern Maryland and Delaware, with disjunct locales in northern New York. This population is severely endangered, and has been reduced by up to a third from its known historic range. The southern population occurs east of the Tennessee-North Carolina border, from south-central Virginia south and westward into extreme northern Georgia.
Mystery Disease Affecting the Bog Turtle
In 1997, the northern population of the bog turtle was listed as Threatened by the U.S. Fish and Wildlife Service’s Endangered Species Act, with the southern population being likewise protected on the basis of similarity of appearance. The primary threats to wild populations are habitat loss due to development and modification, and poaching by unscrupulous collectors. Recently, a number of dead bog turtles infected by an unknown pathogen have been discovered in otherwise apparently stable populations, raising concern that disease may now present a serious threat to the survival of this already imperiled species.
Captive-Bred Bog Turtles Only
As with any species of exotic animal, it is best to seek out captive breeders when acquiring new specimens. Removing any turtle from the wild, especially a species as endangered as the bog turtle, is not only illegal but also highly detrimental to the remaining wild populations clinging tenuously to survival. Additionally, captive breeders have the knowledge and experience required to help you provide adequate husbandry for your new bog turtle.
Bog Turtle Captive Housing
With attention to a few simple details, G. muhlenbergii is a hardy and responsive captive. The bog turtle has relatively simple housing requirements, will accept a wide variety of food items, and typically breeds readily if provided with suitable housing and care. Bog turtles are remarkably intelligent and quickly learn to associate their human caretakers with dinner time.
The best approach to providing housing for G. muhlenbergii is to consider their natural habitat and provide them roughly equal areas of land and shallow water. Anyone keeping bog turtles should provide them with as large an enclosure as they can manage. At a minimum, a single turtle can be kept in a 3-foot by 2-foot tank. Two bog turtles should be provided with at least twice this area, with plenty of sightline breaks and hiding places. Male bog turtles are best housed separately, as they will usually fight doggedly over territory. Soft substrate, such as leaf litter or fine mulch, is preferable for the terrestrial section, and adequate cover is necessary to provide hiding and sleeping spots. Hollow logs or terracotta flower pots split in half can provide suitable shelter; just make sure they are large enough for the turtle to turn around in and still remain hidden. Natural and artificial plants can provide additional cover on the land area. Substrate is not necessarily required for the aquatic section, but areas of varying water depth should be provided. Anything deeper than the length of the turtles’ shells will likely not be used and should be avoided to prevent accidental drowning. Water should be kept relatively clean. Filtration can be challenging, as the bog turtles will often track terrestrial substrate into the water, so a design that allows frequent and complete water changes may be more practical when keeping bog turtles.
Although some keepers have found it possible to maintain bog turtles at relatively constant temperatures and photoperiods year round, to maintain optimum health and promote breeding, it is preferable to attempt to replicate seasonal variations. Full aestivation and brumation are not absolutely required for breeding to occur, but there are indications that fertility increases if G. muhlenbergii is subjected to these conditions. However, these are very complex processes that should only be attempted by experienced keepers, and the level of detail required to describe these processes does not fall within the scope of this article.
Simulating seasonal fluctuations of daylight and temperature can be achieved with electrical timers and heaters. Adjusting the duration of light exposure throughout the year, from approximately 16 hours during the summer to 10 hours during the winter, will cover average day/night cycles across the bog turtle's natural range. Additionally, the basking habit is well developed in bog turtles, so a basking spot should be provided with unimpeded exposure to a good source of UVB lighting. Bog turtles are generally active when air temperature ranges between about 65 and 94 degrees Fahrenheit, and aquarium and terrarium heaters can be used to adjust this accordingly for the season. However, take care to ensure that turtles do not quit feeding while remaining active when temperatures approach the lower or higher ends of this range. If feeding stops but activity does not, the temperatures should be adjusted accordingly until feeding resumes. In general, water temperatures ranging from 65 to 75 degrees Fahrenheit, air temperatures ranging from 75 to 85 degrees, and basking temperatures ranging from 85 to 90 degrees should result in healthy, active bog turtles.
What To Feed Bog Turtles
The bog turtle is an omnivore, with a slight preference for animal matter. Insects are the predominant menu item of wild bog turtles, but they will also readily feed on berries and several plant species. To satisfy their carnivorous cravings, captive G. muhlenbergii will readily accept commercial pellets; insects such as crickets and roaches; earthworms; thawed frozen pinky mice; and cut fish. Additionally, they will also consume strawberries, melon, grapes and occasionally green leafy vegetables, such as romaine lettuce.
Offering bog turtles a wide variety of both animal and plant items will help ensure that proper nutrition is maintained. Nearly-grown and adult bog turtles only require feeding three to four times per week. A ratio of about 2-to-3 animal matter to 1-to-3 vegetable matter should provide adequate variety, and vitamin/mineral supplements can be added in moderation.
Breeding Bog Turtles
The culmination of any captive-breeding project is, of course, the successful propagation of the subject species. Because bog turtles (Glyptemys muhlenbergii) are rare and captive-bred specimens are often difficult and expensive to acquire, the ultimate goal of any keeper of this species should be to produce offspring. As previously mentioned, existing and potential threats to the survival of this species in the wild indicate that, sadly, a day may come when the only viable and sustainable populations are captive ones.
Fortunately bog turtles have proven to reproduce consistently under captive conditions. Breeding bog turtles is a relatively straightforward process, and no elaborate courtship habits have been observed. Male bog turtles will typically identify females visually and presumably through pheromone recognition, and proceed to attempt to mount. Copulation occurs most frequently in the water but does occasionally occur on land as well. In either case, the male bog turtle will pursue a fleeing female and attempt to subdue her with bites to her legs, tail or any other available body part. Because pursuit and biting can become quite violent, it may be necessary to maintain male bog turtles and female bog turtles separately, introducing them only for the purpose of breeding and then only under constant and careful supervision.
After up to six months of brumation, breeding season for the bog turtle occurs between March and June, and once successful fertilization occurs, female bog turtles will deposit a clutch of up to six small, elliptical, parchment-shelled eggs in a shallow nest. Typical clutch size is about three eggs, but older, larger females produce larger eggs and larger clutches. One clutch per season is normal, but occasionally a second clutch is produced. Nesting usually occurs in the late afternoon or early evening. A nest box measuring at least 10 inches long and 8 inches wide, filled 4 inches deep with sandy soil, should be provided for the females enclosure. Female bog turtles are known to dig test holes when gravid, and given that they will sometimes eat their own eggs, careful observation should follow once a female begins to display nesting behavior.
Once eggs have been removed from the bog turtle nest, they should be incubated in a moist substrate. Sphagnum moss, vermiculite, loamy soil and even shredded newspaper have proven successful as mediums. Incubation duration varies according to temperature, and hatching can occur in as few as 40 days and up to twice that duration. Temperatures ranging from 78 to 84 degrees Fahrenheit have produced good results. Like its congener the North American wood turtle (Glyptemys insculpta), the bog turtle appears to exhibit chromosomal sex determination, meaning that unlike most other North American turtle species, incubation temperature has no influence on the resulting gender of the hatchling.
On the happy day that the neonate bog turtles are ready to leave the incubator, they can be transferred to an enclosure identical to that of the adults. However, adult bog turtles have been known to eat their offspring, so youngsters should be kept separately until they are too large to be viewed as food items for the adult bog turtles. The tiny baby bog turtles can be offered the same diet and vitamin/mineral supplementation as the adults, and if fed every other day, they can grow to maturity in around five years.
Bog Turtles are Small and Scarce
It is somewhat coincidental that one of North America’s smallest turtle species is also one of its rarest. The palm-size bog turtle is faced with enormous threats to its survival, both from natural and human causes. The bog turtle has proven to be hardy and readily adaptable to life in captivity, however, providing hope that even if the bog turtle is not able to endure in the wild, G. muhlenbergii may yet persevere in captivity.