Yellow-bellied slider turtles have distinctive physical characteristics that can help you identify the species and the gender. A yellow-bellied slider turtle has a brown or olive green body with a yellow patch on each side of the head. Male yellow-bellied slider turtles become sexually mature when they reach 4 to 5 1/2 inches in length, while the females, which tend to grow larger, have widely varying maturity times.
Measure the length of the turtle from its head to its tail. If its body length exceeds 8 inches, it is usually a female yellow-bellied slider turtle. Male yellow-bellied slider turtles are usually only 5 to 8 inches long, so smaller turtles can be males or immature females.
Hold one of the turtle's front legs between your thumb and index finger and look at the claws. Females have small claws of uniform length. Males have exceptionally long claws, with the three middle claws longer than the others.
Turn the turtle upside down and observe its tail. A male turtle has a long, thick tail with an opening located close to the tip of the tail. A female turtle has a small, thin tail with an opening located nearer to the body. The opening, also known as cloaca, releases excretory and genital materials.
Observe the turtle's colour. Older yellow-bellied slider males can become very dark.