Wood turtle
The wood turtle is a species of turtle in the family Emydidae. The species is native to northeastern North America. The genus Glyptemys contains only one other species of turtle: the bog turtle . The wood turtle reaches a straight carapace length of, its defining characteristic being the pyramidal shape of the scutes on its upper shell. Morphologically, it is similar to the bog turtle, spotted turtle, and Blanding's turtle . The wood turtle exists in a broad geographic range extending from Nova Scotia in the north to Minnesota in the west and Virginia in the south. In the past, it was forced south by encroaching glaciers: skeletal remains have been found as far south as Georgia.
It spends a great deal of time in or near the water of wide rivers, preferring shallow, clear streams with compacted and sandy bottoms. The wood turtle can also be found in forests and grasslands, but will rarely be seen more than several hundred meters from flowing water. It is diurnal and is not overtly territorial. It spends the winter in hibernation and the hottest parts of the summer in estivation.
The wood turtle is omnivorous and is capable of eating on land or in water. On an average day, a wood turtle will move, a decidedly long distance for a turtle. Many other animals that live in its habitat pose a threat to it. Raccoons are over-abundant in many places and are a direct threat to all life stages of this species. Inadvertently, humans cause many deaths through habitat destruction, road traffic, farming accidents, and illegal collection. When unharmed, it can live for up to 40 years in the wild and 58 years in captivity.
The wood turtle belongs to the family Emydidae. The specific name, insculpta, refers to the rough, sculptured surface of the carapace. This turtle species inhabits aquatic and terrestrial areas of North America, primarily the northeast of the United States and parts of Canada. Wood turtle populations are under high conservation concerns due to human interference of natural habitats. Habitat destruction and fragmentation can negatively impact the ability for wood turtles to search for suitable mates and build high quality nests.
Taxonomy
Formerly in the genus Clemmys, the wood turtle is now a member of the genus Glyptemys, a classification that the wood turtle shares with only the bog turtle. It and the bog turtle have a similar genetic makeup, which is marginally different from that of the spotted turtle, the only current member of the genus Clemmys. The wood turtle has undergone extensive scientific name changes by various scientists over the course of its history. Today, there are several prominent common names for the wood turtle, including sculptured tortoise, red-legged tortoise, and redleg.Although no subspecies are recognized, there are morphological differences in wood turtles between areas. Individuals found in the west of its geographic range have a paler complexion on the inside of the legs and underside of the neck than ones found in the east. Genetic analysis has also revealed that southern populations have less genetic diversity than the northern; however, both exhibit a fair amount of diversity considering the decline in numbers that have occurred during previous ice ages.
Description
The wood turtle usually grows to between in straight carapace length, but may reach a maximum of. It has a rough carapace that is a tan, grayish brown or brown in color, with a central ridge made up of a pyramidal pattern of ridges and grooves. Older turtles typically display an abraded or worn carapace. Fully grown, it weighs. The wood turtle's karyotype consists of 50 chromosomes.The larger scutes display a pattern of black or yellow lines. The wood turtle's plastron is yellowish in color and has dark patches. The posterior margin of the plastron terminates in a V-shaped notch. Although sometimes speckled with yellowish spots, the upper surface of the head is often a dark gray to solid black. The ventral surfaces of the neck, chin, and legs are orange to red with faint yellow stripes along the lower jaw of some individuals. Seasonal variation in color vibrancy is known to occur.
At maturity, males, which reach a maximum straight carapace length of, are larger than females, which have been recorded to reach. Males also have larger claws, a larger head, a concave plastron, a more dome-like carapace, and a longer tail than females. The plastron of females and juveniles is flat while in males it gains concavity with age. The posterior marginal scutes of females and juveniles radiate outward more than in mature males. The coloration on the neck, chin, and inner legs is more vibrant in males than in females, which display a pale yellowish color in those areas. Hatchlings range in size from in length. The plastrons of hatchlings are dull gray to brown. Their tail usually equals the length of the carapace and their neck and legs lack the bright coloration found in adults. Hatchlings' carapaces also are as wide as they are long and lack the pyramidal pattern found in older turtles.
The eastern box turtle and Blanding's turtle '' are similar in appearance to the wood turtle, and all three live in overlapping habitats. However, unlike the wood turtle, both Blanding's turtle and the eastern box turtle have hinged plastrons that allow them to completely close their shells. The diamondback terrapin has a shell closely resembling the wood turtle's; however its skin is gray in color, and it inhabits coastal brackish and saltwater marshes. The bog turtle and spotted turtle are also similar, but neither of these has the specific sculptured surface found on the carapace of the wood turtle.
Distribution and habitat
The wood turtle is found in most New England states, Nova Scotia, west to Michigan, northern Indiana and Minnesota, and south to Virginia. Overall, the distribution is disjunct with populations often being small and isolated. Roughly 30% of its total population is in Canada. It prefers slow-moving streams containing a sandy bottom and heavily vegetated banks. The soft bottoms and muddy shores of these streams are ideal for overwintering. Also, the areas bordering the streams are used for nesting. Spring to summer is spent in open areas including forests, fields, bogs, wet meadows, and beaver ponds. The rest of the year is spent in the aforementioned waterways.The densities of wood turtle populations have also been studied. In the northern portion of its range, populations are fairly dilute, containing an average of 0.44 individuals per, while in the south, over the same area, the densities varied largely from 6 to 90 turtles. In addition to this, it has been found that colonies often have more females than males.
In the western portion of its range, wood turtles are more aquatic. In the east, wood turtles are decidedly more terrestrial, especially during the summer. During this time, they can be found in wooded areas with wide open canopies. However, even here, they are never far from water and will enter it every few days.
Evolutionary history
In the past, wood turtle populations were forced south by extending glaciers. Remains from the Rancholabrean period have been found in states such as Georgia and Tennessee, both of which are well south of their current range. After the receding of the ice, wood turtle colonies were able to re-inhabit their customary northern range.Nesting behavior
The wood turtle is oviparous. It produces offspring by laying eggs, and does not provide parental care outside of nest-building. Thus, the location and quality of nesting sites determine the offspring survival and fitness; so females invest significant time and energy into nest site selection and construction. Females select nest sites based on soil temperature, but not soil composition. Average nest size is four inches wide and three inches deep. Also, females build nests in elevated areas in order to avoid flooding and predation. After laying eggs, female wood turtles will cover the nest with leaves or dirt in order to hide the unhatched eggs from predators, and then the female will leave the nest location until the next mating season. Nesting sites can be used by the same female for multiple years. Because nest building occurs along rivers, females tend to spend more time along river areas, compared to male turtles.Ecology and behavior
During the spring, the wood turtle is active during the daytime and will almost always be found within several hundred metres of a stream. The early morning and late afternoon are preferred foraging periods. Throughout this season, the wood turtle uses logs, sandy shores, or banks to bask in sunlight. In order to maintain its body temperatures through thermoregulation, it spends a considerable amount of time basking, most of which takes place in the late morning and late afternoon. The wood turtle reaches a peak body temperature of after basking. During times of extreme heat, it has been known to estivate. Several reports mention individuals resting under vegetation, fallen debris and in shallow puddles. During the summer, the wood turtle is considered a largely terrestrial animal. At night, its average body temperature drops to between and it will rest in small creeks or nearby land.During colder weather, the wood turtle stays in the water for a larger percentage of the time. For this reason, during the winter months it is considered an aquatic turtle. November through February or March is spent in hibernation at the bottom of a small, flowing river. The wood turtle may hibernate alone or in large groups. During this period, individuals bury themselves in the thick mud at the bottom of the river and rarely move. During hibernation, it is vulnerable to flash floods. Emergence does not occur until March or sometimes April, months that mark the beginning of its activation period.
Males are known to be aggressive, with larger and older turtles being more dominant. Larger males rank higher on the social hierarchy often created by wood turtle colonies. In the wild, the submissive turtle is either forced to flee, or is bombarded with physical abuses, which include biting, shoving, and ramming. Larger and more dominant males will sometimes try to remove a subordinate male while he is mating with a female. The defender will, if he does not successfully fight for his position, lose the female to the larger male. Therefore, among males, there is a direct relationship between copulation opportunities and social rank. However, the outcome of encounters between two turtles is more aggression-dependent than size-dependent. The wood turtle that is more protective of his or her area is the victor. Physical bouts between wood turtles increases marginally during the fall and spring.
The wood turtle is omnivorous, feeding mainly on plant matter and animals both on land and in water. It eats prey such as beetles, millipedes, and slugs. Also, wood turtles consume specific fungi, mosses, grasses, various insects, and also carrion. On occasion, it can be seen stomping the ground with alternating hits of the left and right front feet, known as worm charming. This behavior imitates the vibrations caused by moles, sometimes causing earthworms to rise to the surface where they quickly become easy prey. When hunting, the wood turtle pokes its head into such areas as dead and decaying logs, the bottoms of bushes, and in other vegetation. In the water, it exhibits similar behavior, searching algae beds and cavities along the sides of the stream or river.
Many different animals are predators of or otherwise pose a threat to the wood turtle. They include snapping turtles, raccoons, otters, foxes, and cats. All of these species destroy unhatched eggs and prey upon hatchlings and juveniles. Several animals that often target wood turtle eggs are the common raven and coyote, which may completely destroy the nests they encounter. Evidence of predatory attacks are common on individuals, but the northern populations tend to display more scarring than the southern ones. In addition to these threats, wood turtles also suffer from leech infestations.