The river cooter Pseudemys concinna is a freshwater turtle native to the central and eastern United States, from Virginia south to mid-Georgia, west to eastern Texas, Oklahoma, and north to southern Indiana. They are usually found in rivers with moderate current, as well as lakes and tidal marshes. Around 10 are now breading in the UK
River cooters enjoy basking on logs or sun-warmed rocks, and are frequently found in the company of other aquatic basking turtles (sliders and painteds) sometimes piled up on top of each other. All are quick to slip into the water if disturbed. Diurnal by nature, these turtles wake with the warming sun to bask and forage. They can move with surprising speed in the water and on land. It is not unusual for them to wander from one body of fresh water to another, but many seem to develop fairly large home ranges, which they seldom or never leave. They sleep in the water, hidden under vegetation. While those that live in areas that are quite warm remain active all winter, river cooters in cooler climes can become dormant during the winter for up to two months, in the mud, underwater. They do not breathe during this time of low metabolism, but can utilize oxygen from the water, which they take in through the cloaca. River cooters prefer to be well hidden under aquatic plants during the winter dormancy period or while sleeping each night.
While the species is highly omnivorous, river cooters will eat anything, plant or animal, dead or alive. Diet seems to be determined by available food items. While some writers feel that these turtles will not eat meat, predatory behavior has been observed. Although this animal cannot swallow out of water, it will leave the water to retrieve a tasty bug or worm, returning to the water to swallow. Cooters will also enthusiatically chase, kill and eat small fish. They have also been observed eating carrion found along the river's edge. River cooters have tooth-like cusps in the upper jaw, probably an adaptation to aid in eating leaves and fibrous vegetation. Their primary diet would include a wide variety of aquatic plants, and some terrestrial plants that grow near the water's edge. They will happily take fallen fruits as well. In captivity, any kind of plant will be eaten, and some "meats", too. Turtles will also take calcium in a separate form, such as a cuttlebone, so that the turtle can self-regulate calcium intake.
River cooters are faced with loss of habitat, predation by animals, slaughter on the highways and use as a food source by some people. Hatchlings are particularly vulnerable. During their overland scramble to the river, many will be taken by avian and mammal predators. Alligators and muskrats await them in the water. Some will be taken and sold to pet stores. Populations are down in some areas, and there have been increasing reports of injured turtles, but this species as a whole is hardy, and continues to thrive. These turtles can live 40 years or more.
River cooters mating habits are very similar to a red-eared slider. As with the other basking turtles, the males tend to be smaller than females. The male uses his long claws to flutter at the face of the much larger female. Often, the female ignores him. After detecting what may be a pheromone signal while sniffing at a female's tail, a male river cooter will court a female by swimming above her, vibrating his long nails and stroking her face. Females have also been observed doing this to initiate courtship. If the female is receptive, she will sink to the bottom of the river and allow the male to mount for mating. If they do mate, after several weeks the female crawls upon land to seek a nesting site. They often cross highways looking for suitable nesting spots. Females will lay between 12 to 20 eggs at a time, close to water. The eggs hatch within 45 to 56 days and the hatchlings will usually stay with the nest through their first winter.
Mating takes place in early spring. Nesting usually occurs from May to June. The female chooses a site with sandy or loamy soil, within 100 ft (30 m) of the river's edge. She looks for a rather open area, with no major obstacles for the future hatchings to negotiate on their way to the river. The nest is dug with the hind feet. She lays 10–25 or more eggs in one or more clutches. Eggs are ellipsoidal, approximately 1.5 inches (4 cm) long. Incubation time is determined by temperature, but averages 90–100 days. Hatchlings generally emerge in August or September. There have been reported instances of late clutches over-wintering and hatching in the spring. A hatchling will have a round carapace, about 1.5 inches (4 cm) diameter, that is green with bright yellow markings.
In the wild they feed on aquatic plants, grasses, and algae. Younger ones tend to seek a more protein enriched diet such as aquatic invertebrates, crustaceans, and fish. Older turtles may occasionally seek prey as well, but mostly partake of a herbivorous diet.
These turtles can sometimes be found basking in the sun, but are very wary and will quickly retreat into the water if approached. Otherwise, they are difficult to find in the water, which may be due to their ability to breathe while fully submerged. As a result, little is known about their biology and behavior.
River cooters live in a wide variety of freshwater and even brackish locations. Rivers, lakes, ponds and marshes with heavy vegetation provide ideal habitat. Large webbed feet make the river cooter an excellent swimmer, capable of negotiating moderately strong river currents of major river systems. They will collect in large numbers on peninsular floodplains associated with a river oxbow.