Pig-Nose Turtle: Carettochelyidae

Unlike most other water-living turtles, the pig-nose turtle swims by paddling its large front legs, rather than using mainly its hind legs. It uses the hind limbs, which have webbing, to help them paddle and steer. They do not bask, or sun themselves, but they do warm their bodies by swimming to areas of the water with higher temperatures, such as small thermal springs, or hot springs. There, they lie on the river bottom, above the outpouring of hot water, and heat up their "cold-blooded" bodies. Like other animals that are cold-blooded, their body temperatures vary, depending on the outside temperature: In cool water, they are cool; in warm water, they are warm.

These turtles spend much of the day eating. Several of them will sometimes group together and share a good food source when they find one. Otherwise, the turtles spread out, with males and females ranging over a fairly large area: males are known to travel over a 5-mile (8-kilometer) area of river and females over a 2-mile (3.2-kilometer) area.

Males and females come together once a year or possibly once every two years to mate. Scientists know little about their courtship or other mating activities, but the turtles have been seen nesting in the evening and at night toward the end of the dry season, and some females have more than one set of young in a single year. The female makes her nest in a dry spot, often on a high beach. She scrapes out a shallow hole with her hind legs and drops in seven to thirty-nine round, brittle (BRIH-tuhl), or easily broken, eggs that measure 1.5–2.1 inches (3.8–5.3 centimeters) around and weigh 1.1–1.6 ounces (32–46 grams). The white eggs begin developing into young turtles immediately and are ready to hatch in sixty-four to seventy-four days, but the hatching time can be delayed temporarily until the rainy season starts. Because of this delay, the time from egg laying to hatching can be as little as eighty-six days or as much as 102 days. As with many other turtles, the outside temperature during the time before the eggs hatch can affect the number of male and female hatchlings. In this species, a warm spell about halfway through incubation produces females, and a cool spell produces males.