To identify the species of a turtle, examine the shell, head, color, location and size. Leg and toe shape are also key factors in determining a turtle's type.
A turtle's shell has multiple aspects that can be used for identification, including the number of scutes on the bottom, the texture of the top shell, the vertebral keel of the top shell and the top shell pattern. For example, leatherback turtles have a leathery top shell, while desert tortoises have a drastically domed top shell and easily visible growth lines on each scute.
Head shape, including identification factors such as an elongated snout and color patterns on the head and shell, are easy to see. A turtle with red stripes on its head is likely to be a red-eared slider, while yellow markings are found on western painted turtles. Where the turtle is found helps to narrow down the potential species, though non-native species can sometimes be found in wet or highly populated locations.
Flippers that lack toes are indicative of sea turtles, while turtles and tortoises have more pronounced toes. Whether they have webbed or separate toes and the general shape of the feet can help determine the species of turtle.