The genitals of tortoises are internal, so these animals are typically sexed through looking at secondary sexual characteristics. These secondary sexual characteristics include the shape of the animal's shells, the length and thickness of the tail and the shape of certain claws. When using secondary sexual characteristics to sex tortoises, it is best to have both a male and female to compare the various anatomical characteristics. Using these characteristics you can sex a tortoise.
Lift the tortoise high enough to examine its belly, if it is small enough. Gently flip the animal onto its back if it is too large to lift up.
Examine the plastron, which is the shell that protects the tortoise's belly. Male animals have a concave plastron. This depression enables them to mount the female's domed top shell during mating. Female tortoises have a flat plastron.
Look for modified scales on the plastron of certain species of tortoises, such as the Sulcata's tortoise. These protrusions, termed gular scutes, extend from the plastron and form a ledge under the neck of the tortoise. The gular scutes are very pronounced in male animals.
Watch the tortoise closely when it defecates and urinates. The animal extends its tail, which is much thicker at the point where it joins the body and longer in male tortoises. You may also be able to extend the tail in small individual animals to verify your sexing.
Place the tortoise on an elevated surface and watch the animal from behind. In certain species, such as the Russian tortoise, the longer tail of the male animal turns to the side and lies against the tortoise's body. The female animal in this species has a short tail that does not turn to the side.
Observe the anus. The male's anus is positioned well away from the edge of its shell. The anus of the female tortoise is located close to her body, normally within the edge of the shell.
Observe the tip of the tail on the Hermann tortoise. The male animal has a much longer spur than the female. Hermann tortoises need to be at least 5 years old before they can be sexed correctly.
Observe the height in adult leopard tortoises. Adult females are higher domed and slightly larger animals than the males.