The red-eared slider or red-eared terrapin (Trachemys scripta elegans) is a subspecies of the pond slider (Trachemys scripta), a semiaquatic turtle belonging to the family Emydidae. Native to the southern United States and extreme northern Mexico, it is popular as a pet across the world, and is the most invasive turtle. It is the most commonly traded turtle in the world.
The red-eared slider is native to the Midwestern United States and northern Mexico, but has become established in other places because of pet releases, and has become invasive in many areas where it outcompetes native species. The red-eared slider is included in the list of the world's 100 most invasive species.
Red-eared slider young look practically identical regardless of their sex, making distinguishing them difficult. One useful method, however, is to inspect the markings under their carapace, which fade as the turtles age. Distinguishing the sex of adults is much easier, as the shells of mature males are smaller than those of females. Male red-eared sliders reach sexual maturity when their carapaces' diameters measure 10 cm (3.9 in) and females reach maturity when their carapaces measure about 15 cm (5.9 in). Both males and females reach sexual maturity at 5–6 years old. Males are normally smaller than females, although this parameter is sometimes difficult to apply, as individuals being compared could be of different ages.
Males have longer claws on their front feet than the females; this helps them to hold onto a female during mating, and is used during courtship displays. The males' tails are thicker and longer. Typically, the cloacal opening of a female is at or under the rear edge of the carapace, while the male's opening occurs beyond the edge of the carapace. The male's plastron is slightly concave, while that of the female is completely flat. The male's concave plastron also helps to stabilize the male on the female's carapace during mating. Older males can sometimes have a dark greyish-olive green melanistic coloration, with very subdued markings. The red stripe on the sides of the head may be difficult to see or be absent. The female's appearance is substantially the same throughout her life.
The red-eared slider 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. In nature, they 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. Individuals are often found sunbathing in a group or even on top of each other. They also require abundant aquatic plants, as these are the adults' main food, although they are omnivores. They are, however, carnivorous as juveniles as they require a high protein intake for growth.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.
Invasive red-eared sliders cause negative impacts in the ecosystems they are introduced to 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.
