Unless you're experienced at telling the difference between male and female salamanders, sexing your tiger salamander can be difficult. There are no differences between the two at first glance and only subtle clues give away the gender. The best time to determine the sex of your salamander is during breeding season.
During mating season, in early spring, look at your salamander's tail. A male's tail will change slightly during this time, flattening out from side to side. His tail also usually is longer than a female's, often longer than his body, while a female's tail rarely exceeds the length of her body. The male's vents near his reproductive organs also swell during breeding season. These vents can be seen by looking between his rear legs, near the base of his tail. You also may see small protruding sex organs. Compared to a female, a male tiger salamander usually has thicker, stouter back legs.