Chicken turtle
The chicken turtle (Deirochelys reticularia ) is a turtle native to the southeastern United States. It is the only extant member of the genus Deirochelys and is a member of the freshwater marsh turtle family Emydidae. The chicken turtle's scientific name refers to its extremely long neck and distinctive net-like pattern on its upper shell. There are three regionally distinct subspecies (eastern, western and Florida), which are thought to have evolved when populations became separated during periods of glaciation. These subspecies can be distinguished by their appearance; the western chicken turtle displays dark markings along the seams of its plastron (lower shell), while the plastron of the Florida subspecies is a bright yellow or orange color. Fossil records show that the chicken turtle has been present in the region for up to five million years.
Chicken turtles inhabit shallow, still or slow-moving bodies of water with plenty of vegetation and a muddy substrate. They are not found in rivers or deeper lakes that may be home to predators such as alligators and large fish. The chicken turtle is predominantly carnivorous and feeds mostly on invertebrates such as crayfish, dragonflies and spiders, but is also known to eat tadpoles, carrion and occasionally plant material. It is an active hunter and its long neck allows it to catch fast-moving prey. Although feeding and mating take place in aquatic environments, the chicken turtle is very well adapted to living on land and may spend more than half the year out of the water. Like many reptiles, it spends much of the day basking in the sun to regulate its body temperature, but unlike most other aquatic turtles, it hibernates over the winter months except in the warmer, southernmost reaches of its range.
The chicken turtle is relatively small compared to other related turtles, with males measuring up to around 16.5 cm (6.5 in) and females around 26.0 cm (10.2 in). It is also one of the world's shortest-lived turtles, reaching a maximum age of 20–24 years. There are thought to be around 100,000 adult chicken turtles in the wild. Although the population as a whole is considered secure, its status in some areas is less certain and several states have listed it as threatened or introduced regulations to manage hunting or taking. The word "chicken" in the turtle's vernacular name is apparently a reference to the taste of its meat, which was once popular in turtle soup and commonly sold in southern markets.
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starts withThe chicken turtle resembles the painted turtle (Chrysemys picta ) and some species of cooter (genus Pseudemys ) in appearance, but has an unusually long neck that is close to the length of its shell. It often also has black blotches on the underside of the bridge (the part of the shell connecting the carapace and plastron), which are not present in these other species. The carapace of the chicken turtle is elongated and pear-shaped, with the rear half noticeably wider than the front. It ranges from dark green to brown in color, and features a distinctive yellowish net-like pattern across its entire upper surface. The scutes of the upper shell have a ridged or wrinkled texture and are rough to the touch. Beneath its shell, the chicken turtle has particularly slender ribs, supposedly developed to accommodate its long, muscular neck. Although the chicken turtle shares morphological features with Blanding's turtle (Emydoidea blandingii ), such as these elongated ribs and the shape of the skull, DNA analysis has shown they are not closely related.
Descriptions of the chicken turtle disagree on the base color of its skin but it is generally reported to be darker than the carapace, varying from olive to brown to black. One of the distinguishing features of D. reticularia is a broad yellow stripe on the forelegs. The skin of the neck and head also has light stripes, although narrower, while the tail and rear legs show vertical yellow markings. The head itself is elongated with a somewhat pointed snout but no other distinguishing features, and the digits of the feet are webbed and tipped with claws.
Compared to other turtles, the chicken turtle is small to medium in size. Adults vary in length from around 10–25 cm (4–10 in), with an average length of around 13 cm (5 in). The width of the carapace is roughly 65 percent of its length. Mature chicken turtles exhibit some degree of sexual dimorphism; the females are larger and heavier than males, although the males have longer, thicker tails. Unlike the painted turtle, there is no difference between the sexes in terms of the length of the foreclaws.
Chicken turtle hatchlings measure approximately 28–32 mm (1.1–1.3 in) and weigh around 8–9 g (0.28–0.32 oz). The shell is much rounder than the adults', and the shell and skin are considerably brighter in color, with a greater number of light stripes. The young of the western chicken turtle hatches with the distinctive dark markings on its plastron already present.
The chicken turtle is found throughout the southeastern United States; its range extends from the Atlantic coastal plain and states such as North Carolina, South Carolina, Georgia and Florida westward through the Gulf plain towards the Mississippi River. It tends to remain in coastal areas and is largely absent from the Piedmont plateau and more mountainous regions in the north of these states. West of the river, its territory reaches as far north as Missouri and as far west as Oklahoma and central Texas. Across its range, the chicken turtle may inhabit many hundreds or possibly thousands of wetland sites, although populations in any particular location are generally small.
Chicken turtles are semiaquatic, equally comfortable in wetland habitats and on land. All three subspecies have similar preferences; they like quiet, still or slow-moving bodies of water such as shallow ponds, oxbow lakes, drainage ditches, borrow pits, marshes, swales, cypress swamps, and Carolina bays. Generally, the chicken turtle prefers water with a maximum depth of around 70 cm (2.3 ft), but it is known to inhabit ponds up to 2 m (6.6 ft) deep. It rarely inhabits moving water such as streams or rivers, but may sometimes colonize quieter rivulets or pools in the riparian zone. Furthermore, it strongly favors fresh water, avoiding brackish water wherever possible.
The chicken turtle thrives in bodies of water with dense aquatic vegetation and a soft, muddy substrate. Often these are ephemeral or temporary wetlands that readily dry out during the summer or in periods of drought. Such habitats tend to be free both of fish, which would provide competition for food, and potential predators such as alligators. When drying occurs, chicken turtles will migrate to the land and burrow into the soil or hide under foliage to avoid dry weather. Although they are well adapted to living terrestrially, they rarely abandon their original habitat even during extended dry spells, and will relocate to the water once it returns.
Although the chicken turtle does not generally inhabit islands, isolated groups are also known in the Outer Banks chain of barrier islands off North Carolina. These maritime forest habitats are prone to drying out easily in the summer and can be affected by storms and sea spray, but research into one of these groups found no meaningful differences in longevity, growth rate or sex ratio between members of this population and their mainland counterparts.
The chicken turtle is diurnal; its main periods of activity, such as feeding and mating, take place in the morning and late afternoon, either side of the warmest hours of the day. Like all reptiles, chicken turtles are cold-blooded and must regulate their body temperature. The main way they do this is through basking; they will spend many hours in the sun and can often be seen sitting on logs or tree stumps with their neck outstretched. However, they tend to spend less time basking than their herbivorous relatives. In order to be active, chicken turtles require an internal body temperature of around 25.5 °C (77.9 °F), therefore they are generally more active on warm, cloudy days than on hot, sunny ones. Like other turtles, the chicken turtle is extremely wary while basking and can be startled easily. Some have been known to bite and scratch in response to threats while others are more timid and retiring. Males may display particularly hostile behavior towards each other.
Unusually for an aquatic turtle, the chicken turtle is known to hibernate in winter throughout the northern part of its range. It leaves the water in late September to find a suitable site for the winter, usually either in mud and vegetation around the edges of the ponds and swamps which it inhabits. Alternatively, it may bury itself under fallen leaves in surrounding woodlands or in the mud at the bottom of a pond. Hibernating chicken turtles remain out of the water for up to six months before becoming active again in the spring. They are able to spend long periods on land without feeding due to their large stores of body fat. The first few days of activity following hibernation are generally dedicated to nesting and egg-laying by females, with males emerging slightly later around early April. In the southernmost part of its range where winters are milder, the chicken turtle remains active all year round apart from on especially cool days.
Chicken turtles are also frequently encountered on land during the summer months when the temporary wetlands they inhabit dry out. Males especially wander onto the land during this period and may travel great distances in search of alternative water, whereas gravid females remain in the wetland as long as possible since extra water is needed for egg production. Turtles unable to find a suitable aquatic habitat during particularly dry years may migrate to higher ground and burrow into the earth to undergo aestivation, a period of dormancy similar to hibernation. Survivorship rates among small juveniles are lower during this period, possibly because they lack the fat and water reserves required to withstand long periods without feeding. Individuals are known to return to the same terrestrial refugia from one year to the next. In total, a chicken turtle may spend up to 285 days per year on the land.
Like many emydids, chicken turtles are almost completely carnivorous during the first year of their lives. However, they are unusual in preferring a carnivorous diet into adulthood. It has been suggested that this explains the smaller local populations of D. reticularia compared to other related turtles due to competition with fish for food, especially insects. In the wild they are known to prey on crayfish, invertebrates, tadpoles, vegetation and carrion, including dead fish and other animals. Carr described having seen a chicken turtle eating Nuphar (bonnet-lily) buds, while captive adults have been observed feeding on gopher frog tadpoles, lettuce, and canned fish.
In a 1997 study of chicken turtle fecal matter collected during the summer months in South Carolina, dragonfly nymphs were the most commonly observed food, along with snails, spiders and insects such as backswimmers and water bugs. Only six out of forty-three specimens had ingested plant material. Investigations into the digestive tract contents of chicken turtles in north-central Florida, where the eastern and Florida subspecies coexist, found similar results. Decapods (including crayfish and shrimp), dragonflies and beetles were the most frequently encountered foods; six out of twenty-five turtles had consumed trace amounts of plants or algae. Research in Oklahoma found evidence that adults of the western subspecies follow a more omnivorous diet than their relatives. While crayfish and bugs were still present in the majority of fecal samples, 92.6 percent of samples also contained material or seeds of various plants, including the common rush and broadleaf cattail.
The chicken turtle is an aquatic hunter. It waits in the water and strikes its long neck out quickly with its mouth open to catch live food, relying on sight to detect its prey. The length of the neck allows it to capture fast-moving prey such as fish and spiders, which would otherwise be able to escape. Like Blanding's turtle, the chicken turtle uses a sucking motion when feeding; any water taken in during the process is expelled before the food is swallowed whole. The Florida chicken turtle is known to feed passively, swimming along with its long neck extended and foraging in clumps of vegetation.
The chicken turtle population as a whole is currently considered secure and is thought to consist of at least 100,000 adults. Local populations are often small but stable, however the species is designated by NatureServe as S1 (critically imperiled) in Virginia and Missouri and S2 (imperiled) in Arkansas, Louisiana, North Carolina and Oklahoma. The chicken turtle does not appear on the IUCN's Red List of Threatened Species, although the Tortoise and Freshwater Turtle Specialist Group's own provisional list considers it Near Threatened. At the state level, the chicken turtle is protected by various local laws. In Virginia, where only around 30 adults are thought to remain, it has been listed as "vulnerable" since 1987. It is also considered at risk by the Alabama Natural Heritage Program; local regulations state that only two turtles may be kept and these must be for personal use (e.g. as pets). Along with other native reptiles, removal of chicken turtles from their natural habitat is regulated in several states throughout its range including Texas, Georgia and North Carolina. The chicken turtle is subject to a ban on commercial taking in Arkansas, where it is "extremely rare". In Missouri, where until 1995 no sightings had been recorded for at least 33 years, it is listed as an endangered species, making hunting illegal.
Habitat loss appears to be the most significant threat to the stability of chicken turtle populations. Human activity is one cause of this; the turtle's preferred wetland habitats are often converted for agriculture, such as rice farming, or building developments. In Missouri and Arkansas in particular, the destruction of swampland and bottomland hardwood forests is a direct threat to the chicken turtle. Man-made obstacles such as fences and road barriers can also lead to populations becoming isolated. Since it prefers to live in small, shallow bodies of water that can easily dry out during the hotter months, the chicken turtle is also susceptible to the loss of upland habitats surrounding wetlands to which it migrates during periods of drought. Migration also leads to turtles, especially females in search of suitable nesting sites, walking onto roads where they are killed by traffic. Fire is a further threat; wildfires are becoming increasingly common and while controlled burns can help to protect wetland habitats by decreasing the risk of wildfire, chicken turtles that are overwintering on land or have been forced onto the land during drier months can be caught up in them.
Several locations inhabited by chicken turtles are already under protection, having been designated as wildlife reserves or conservation areas. However, further preservation of wetlands, especially temporary ones, would be beneficial in ensuring the continued stability of the population. In particular, the protections currently in place rarely include the surrounding areas of land that the chicken turtle inhabits for much of the year. Scientists in Oklahoma have developed quantitative polymerase chain reaction assay tests to enable the presence of four uncommon or vulnerable reptiles, including the chicken turtle, to be identified through environmental DNA.
