These turtles are poikilotherms, so are unable to regulate their body temperatures independently; they are completely dependent on the temperature of their environments. For this reason, they continually need to sunbathe to warm themselves and maintain their body temperatures. If their body temperature falls below a threshold of 21°C, they are unable to carry out normal functions of digestion and defecation.
The shell is divided into two sections: the upper or dorsal carapace and the lower, ventral carapace or plastron. The upper carapace consists of the vertebral scutes, which form the central, elevated portion, pleural scutes that are located around the vertebral scutes and then the marginal scutes around the edge of the carapace, the rear marginal scutes are notched. The scutes are bony keratinous elements. The carapace is oval and flattened (especially in the male) and has a weak keel that is more pronounced in the young. 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 born 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 centre of most scutes. The plastron is highly variable in pattern. The head, legs, and tail are green with fine, yellow, irregular lines. The whole shell is covered in stripes and marks that aid in camouflaging an individual.Behavior
Red-eared sliders are almost entirely aquatic, but, as they are cold-blooded, they leave the water to sunbathe to regulate their temperature. They are excellent swimmers. When they are out of the water, they remain alert and flee from any predators or from humans. On sensing a threat, they rapidly launch themselves back into the water. During the day, they usually alternate between warming themselves in the sun and spending time in the water. They can become aggressive if they become overcrowded or if the ratio of the sexes is not balanced. In captivity, a ratio of two or three females per male is usually recommended.Reproduction
courtship and mating activities for red-eared sliders usually occur between March and July, and take place under water. During courtship, the male swims around the female and flutters or vibrates the back side of his long claws on and around her face and head, possibly to direct pheromones towards her. The female swims toward the male and, if she is receptive, sinks to the bottom for mating. If the female is not receptive, she may become aggressive towards the male. Courtship can last 45 minutes, but mating takes only 10 minutes. On occasion, a male may appear to be courting another male. In reality, this is a sign of dominance and the males may start to fight. Young turtles may carry out the courtship dance before they reach sexual maturity at five years of age, but they are unable to mate.Red-eared sliders as pets
The red-eared slider is the most common type of water turtle kept as pets. 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. Red-eared sliders can be quite aggressive—especially when food is involved. Behavior is usually noted to become this way when fed live food. If being kept as a pet, care must be taken to prevent injury or even death of smaller tank mates. Additional care is needed if shrimp are used as food. Smaller red-eared sliders less than a year old have been known to choke on the shells of the shrimp and suffer from lung puncture.