Things You'll Need
- Measuring tape or ruler
Instructions
Notice your turtle's coloring. Red-eared sliders are brightly colored when they are less than six months old; hatchlings' shells are often kelly green with light yellow markings. After age 1, these colors fade to a muddied, olive hue. After age 2, the turtle will continue to become increasingly darker until its tell-tale red "ears" seem to disappear and its shell turns an almost brown or ochre shade.
Measure the diameter of your turtle's carapace, edge to edge. When these animals are hatched, their shells can be no bigger than a thumbnail. However, by the time they're 4 inches long (which is when they can be purchased from pet stores), the turtles will have likely reached the age of 2. By the age of 4, a turtle can be anywhere between 6 and 8 inches long. Growth can then continue until the turtle reaches about 12 to 13 inches, after which point it is almost impossible to determine age by size alone.
Examine your turtle's front and back ends. After the age of 2, male red-eared sliders develop elongated claws and tails. The claws are especially prickly and refined between the ages of 2 and 3 and become duller and shorter over time.