• Can You Smile at a Crocodile?
    Awake!—2005 | March 8

    • The Big “Salty”

      Saltwater, or estuarine, crocodiles​—the biggest reptiles on earth—​can grow to a length of 23 feet [7 m] or more and weigh up to 2,000 pounds [1,000 kg]. Living exclusively in salt water, they are found in river estuaries, seas, and mangrove swamps along the coasts from India to northern Australia. Carnivorous, they eat rats, frogs, fish, snakes, crabs, turtles, and deer​—in small quantities; large males average only 18 to 24 ounces [500-700 g] of food a day. An easygoing life-style of basking in the sun or floating in the water and an efficient digestive system keep their energy requirements low. A big “salty” may occasionally attack an unwary human. Salties swim by moving their tail from side to side, with their body submerged except for nostrils and eyes, and they walk on their short legs. They can leap up to catch food and are known to gallop after prey at times. Like all other crocodiles, their senses of smell, sight, and hearing are good. The male salty is fiercely territorial during the mating season, and the female is equally fierce when guarding her eggs.

      Devoted Mothers

      The female crocodile builds a nest near the water, usually a mound of decaying vegetation and mud. She lays up to 100 oval, hard-shelled eggs, covers them, and guards them from predators. Then, she splashes water onto the nest to promote the decay of the covering vegetation, thus generating heat to incubate the eggs.

      Now something fascinating takes place. The temperature at which each egg is incubated determines the gender of the hatchling. Imagine that! When the temperature ranges between 82 and 88 degrees Fahrenheit [28 and 31°C], females are produced in about 100 days; whereas, when the temperature is 90.5 degrees Fahrenheit [32.5°C], males hatch within 64 days. Eggs incubated between 90.5 degrees Fahrenheit [32.5°C] and 91 degrees Fahrenheit [33°C] can produce either gender. A nest built with one side at the water’s edge and the other side facing the hot sun could produce males from the warm side and females from the cooler side.

      When the mother hears chirping sounds, she removes the nest covering, sometimes breaking the eggs if the hatchlings have not already done so with their specially provided shell-breaking tooth. She lifts them very gently in her great jaws and carries them in a pouch under her tongue to the water’s edge. They are independent at birth and immediately forage for insects, frogs, and small fish. Some protective mothers, however, stay close for several months, creating nursery areas in the swamps, where father can share in baby-sitting and protecting the young.