Despite a few key anatomical and behavioral differences, male and female crocodiles may be difficult to tell apart. Carefully examine size, shape, reproductive organs and behavior. The differences may not always be immediately obvious, but a closer look allows you to tell which are which.
Size and Shape
No matter the type of crocodile, males grow larger than females. The male saltwater crocodile, for example, can grow up to 17 feet long, while the female does not quite reach 11 feet. The sexes may also have different proportions from males; for example, depending on the species, the females may have slimmer bodies relative to their length. In all 23 species, males grow larger than females, making size comparisons a fast and dependable way of identifying the sex.
Male and female crocodiles have internal sex organs, which may make it difficult to tell them apart unless you are conducting a close inspection. Both sexes have a “vent,” or a slit that houses the sex organs—unless mating is going on, male and female vents are typically indistinguishable. When males are ready to mate, the penis extends out of the vent so it can enter the female’s vent. His testes remain inside the body at all times.
After mating, a female crocodile builds a nest where she can incubate and lay her eggs. The type of nest varies from species to species, but generally consists of a hole or mound dug into the soil. The mother incubates her eggs for a period of about 90 days, guarding them from predators. Though not all mothers are especially reliable protectors—the American crocodile, for example, is prone to abandoning the nest out of fear—it is always they, and not the males, that incubate their young.
Raising the Young
Watching the way a crocodile behaves with young crocodiles can help you determine the sex. A mother protects her young until they are about 1 year old, keeping predators at bay and even carrying the young in her mouth. The only species in which the female does not do this is the gharial, and only because her mouth is too small to carry her young—she still, however, protects them from predators.
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Tom Ryan is a freelance writer, editor and English tutor. He graduated from the University of Pittsburgh with a degree in English writing, and has also worked as an arts and entertainment reporter with "The Pitt News" and a public relations and advertising copywriter with the Carnegie Library of Pittsburgh.