The Red-eared slider is a semiaquatic turtle belonging to the family Emydidae. It is a subspecies of the Pond slider. It is the most popular pet turtle in the United States and is also popular as a pet in the rest of the world. It has, therefore, become the most commonly traded turtle in the world. Red-eared sliders get their name from the small red stripe around their ears and from their ability to slide quickly off rocks and logs into the water. Their shell is divided into two sections: the upper or dorsal carapace, and the lower, ventral carapace or plastron. The color of the carapace changes depending on the age of the turtle. The carapace usually has a dark green background with light and dark, highly variable markings. In young or recently hatched turtles, it is leaf green and gets slightly darker as a turtle gets older, until it is a very dark green, and then turns a shade between brown and olive green. The plastron is always a light yellow with dark, paired, irregular markings in the center of most scutes. The head, legs, and tail are green with fine, irregular, yellow lines. The females of the species are usually larger than the males.
Red-eared sliders originated from the area around the Mississippi River and the Gulf of Mexico, in warm climates in the southeastern United States. Their native areas range from the southeast of Colorado to Virginia and Florida. Owing to their popularity as pets, Red-eared sliders have been released or escaped into the wild in many parts of the world. Feral populations are now found in Australia, Europe, Great Britain, South Africa, the Caribbean Islands, Israel, Bahrain, the Mariana Islands, Guam, and southeast and far-east Asia. In nature, these turtles inhabit areas with a source of still, warm water, such as ponds, lakes, swamps, creeks, streams, or slow-flowing rivers. They live in areas of calm water where they are able to leave the water easily by climbing onto rocks or tree trunks so they can warm up in the sun. Turtles in the wild always remain close to water unless they are searching for a new habitat or when females leave the water to lay their eggs.
Red-eared sliders are diurnal and spend most of the time in the water; however, as they are cold-blooded, they leave the water to sunbathe to regulate their temperature. They are often found sunbathing in a group or even on top of each other. Red-eared sliders do not hibernate, but actually brumate; while they become less active, they do occasionally rise to the surface for food or air. Brumation can occur to varying degrees. In the wild, Red-eared sliders brumate over the winter at the bottoms of ponds or shallow lakes. They generally become inactive in October, when temperatures fall below 10 °C (50 °F). During this time, the turtles enter a state of sopor (deep sleep), during which they do not eat or defecate. They remain nearly motionless, and the frequency of their breathing falls. Individuals usually brumate underwater, but they may also be found under banks and rocks and in hollow stumps. In warmer winter climates, they can become active and come to the surface for basking. When the temperature begins to drop again, however, they quickly return to a brumation state. Slider turtles have very sharp vision. Their eyes have receptors that can see ultraviolet, violet, blue, green, and red light. In order to communicate with each other, they use eye-rolling, vibrations, touches and displays.
Little is known about the mating system in Red-eared sliders. They usually breed between March and July. During courtship, the male swims around the female and flutters or vibrates the backside of his long claws on and around her face and head, possibly to direct pheromones towards her. After mating, the female spends some time basking to keep her eggs warm. A female can lay between 2 and 30 eggs depending on body size and other factors. One female can lay up to 5 clutches in the same year, and clutches are usually spaced 12-36 days apart. During the last weeks of gestation, the female spends less time in the water and smells and scratches at the ground, indicating she is searching for a suitable place to lay her eggs. She excavates a hole, using her hind legs, and lays her eggs in it. Incubation takes 59-112 days. A new hatchling breaks open its egg with its egg tooth, which falls out about an hour after hatching. This egg tooth never grows back. Hatchlings may stay inside their eggshells after hatching for the first day or two and begin their independence from the day they emerge from their eggs. Young turtles reach reproductive maturity at five years of age, but they are unable to mate.
There are no major threats to Red-eared sliders in the wild. However, these turtles are taken from their natural habitat and are used in the pet trade and are also used for food in Asia.
According to IUCN, the Red-eared slider is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
These turtles are considered one of the world’s worst invasive species. They cause negative impacts on the ecosystems they occupy because they have certain advantages over the native populations, such as a lower age at maturity, higher fecundity rates, and larger body size, which gives them a competitive advantage at basking and nesting sites, as well as when exploiting food resources. They also transmit diseases and displace the other turtle species with which they compete for food and breeding space.
Red-eared slider turtles are the world’s most commonly traded reptile, due to their relatively low price, and usually low food price, small size, and easy maintenance. As with other turtles, tortoises, and box turtles, individuals that survive their first year or two can be expected to live generally around 30 years. When they mature they can inflict painful bites, leading irresponsible owners to release them into the wild with negative ecological, social and, economic impacts. Red-eared sliders are included in the list of the world's 100 most invasive species published by the IUCN.