Afro-American River Turtles: Podocnemididae

These turtles' behavior depends on where they live. Some of them hardly ever leave their river homes. In these species, the female often makes the only trips on land. To lay her eggs, she crawls up onto a sandbar, a ridge of sand built up by currents in the water. Besides those turtles that live only in rivers, other species live in calm pockets of water along the river, sometimes in flooded forest pools, and the females lay their eggs on riverbanks. Still other species of these turtles also make their homes in small streams and ponds, and the females make long trips over land to nest. When the dry season empties the stream or pond, they crawl underground, become inactive, and wait for the rains to return. The Madagascan big-headed turtle, for example, spends the dry season buried in the mud. Scientists know few details about the activities of the Afro-American river turtles, including whether the males "court" the females to attract them or how they mate.

Nesting time is tied to the rainy season. As the rainy season ends, the females typically start to sunbathe in the early morning and late afternoon. She then begins her migration to a nesting site, which can take a very long time. Many Afro-American river turtles nest in large groups. Each female of the group digs her own hole, where she lays and buries her eggs. The females of some species are known to use only their hind legs in digging the nest and covering up their eggs. Different species lay varying numbers of eggs in their nests. The smaller river turtles, for instance, lay about five to twenty eggs per nest, while the largest species can lay up to 156 eggs. In all species except the South American river turtle, the eggs are longer than they are wide. The South American river turtle has round eggs. Some species make one nest a year, and others make two or more. Female Madagascan big-headed turtles skip a year between nestings. Nest temperature controls the number of males and females in the nest, with very warm and sometimes particularly cold temperatures producing females, and more moderate, or mild, temperatures producing males. The eggs hatch in forty to 149 days.