Red-eared slider turtles display elaborate courtship behavior underwater, and if the female is not interested, she becomes aggressive. If she is willing to mate, she goes to the bottom. Mating takes only about 10 minutes after a 45-minute courtship.
Red-eared sliders usually reach sexual maturity when they are about three to four years old, although ability to mate depends more on their size than their age. Males are sexually mature when they are about four inches long, while females reach six to seven inches in length by the time they are sexually mature. Males have longer claws than females, which they use during courtship and mating. When a male courts a female, he circles her and vibrates his claws around her head. Although sexually immature turtles may mimic this behavior, they do not mate afterward.
The female adjusts her diet and spends extra time in the sun after mating. Egg-laying occurs within days or weeks, and the eggs become fertilized when the female lays them. However, if the egg-laying does not occur until the following season, the male's sperm remains viable within the female. Just before laying her eggs, the female finds a suitable site and digs a hole, usually near the shore of a body of water. She can lay five to six clutches a year, and each clutch contains two to 30 eggs. Incubation time depends on the temperature, but it ranges from 59 to 112 days.