Afro-American River Turtles: Podocnemididae
AFRO-AMERICAN RIVER TURTLES: PodocnemididaeSOUTH AMERICAN RIVER TURTLE (Podocnemis expansa): SPECIES ACCOUNT
The Afro-American river turtle is described as a "side-necked" turtle because it cannot pull its neck and head straight back into the shell. Instead, it folds its neck sideways under its shell. The largest member of this family has an upper shell, or carapace (KARE-a-pays), that reaches 42 inches (107 centimeters) in length. Afro-American river turtles have only four toes on their hind feet. Some species also have barbells (BAR-buhls), which are bits of flesh that dangle from their chins. Some scientists believe that these turtles should be grouped with similar turtles in the family Pelomedusidae, which live in mainly in Africa.
Afro-American river turtles are found in Madagascar and northern South America.
Many of these freshwater turtles live on riverbanks and in large lakes, but some also live in streams and swamps, wetlands partly covered with water. Sometimes they move into flooded forests. Their range, or the area in which they live and feed, includes Madagascar, which lies off the eastern coast of southern Africa, and northern South America.
Afro-American river turtles are mainly plant eaters; they are especially fond of fruits that drop off the trees on the shore and fall into the water. They also eat stems, leaves, and grasses. They dine on meat once in a while, and when they do, they eat insects, fishes, or other freshwater animals.
BEHAVIOR AND REPRODUCTION
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.
THE LARGEST TURTLE EVER
Afro-American river turtles live only in South America and thousands of miles away in Madagascar, but it was not always that way. Scientists have found fossils (FAH-suhls), or the dead remains, of these turtles on every continent except Australia and Antarctica. Although the river turtles live only in freshwater rivers, ponds, and streams, the fossils show that the turtles once also lived in saltwater and on land. One of the species in this family was the largest turtle that ever lived. This turtle, known as Stupendemys geographicus, had an upper shell that measured 7.5 feet (2.3 meters) in length and might have weighed 4,000–5,000 pounds (1,814–2,268 kilograms).
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.
AFRO-AMERICAN RIVER TURTLES AND PEOPLE
People hunt these turtles for their meat and their eggs.
According to the World Conservation Union (IUCN), seven of the eight species face some threat of survival. Two species are Endangered, meaning that there is a very high risk that they will become extinct in the wild soon. Four species are Vulnerable, facing a high risk of extinction. One species is listed as Lower Risk: Conservation Dependent, meaning that its survival depends on conservation measures. The U.S. Fish and Wildlife Service lists two species as Endangered. Much of the decline in this family of turtles can be traced to too much hunting of adults and collecting of their eggs. Efforts are under way to protect the turtles' nesting areas, so that the females have a safe place to lay their eggs.
Physical characteristics: Also known as the arrau or tartaruga, the South American river turtle sometimes is described as "giant" because it is so large. The upper shell can measure more than 3.5 feet (1 meter) in length. The carapace is rather flat and a bit wider at the rear than it is at the front. It is typically dark brown, but in spots it may be worn away to a paler, almost orange color in older turtles. The head is dark on top and down the cheeks but pale yellowish-tan on the bottom and on the neck. Two barbels hang from its chin. Young turtles have a more patterned head with yellow blotches outlined or spotted in black.
Geographic range: These turtles live in northern South America.
Habitat: These freshwater turtles live in large river branches in the Orinoco and Amazon river systems of northern South America. If the water rises high enough and overflows into areas next to the rivers, they may move into these flooded areas, too.
Diet: This species eats plants, insects, and sponges, but it prefers the fruits of riverside trees.
Behavior and reproduction: Nesting begins shortly after the rainy season ends. During the nesting period, which may last ten to sixty days, the female travels upstream or downstream to reach a nesting site, which she shares with other females. Late at night the females climb onto a sandbar, and each one uses both her front and hind legs to dig a hole more than 1 yard (1 meter) around and 1.5 feet (0.5 meters) deep. At the bottom of the hole, the female uses only her hind legs to continue digging another pit, where she lays her eggs. Unlike other members of the family, which lay oblong eggs, the South American river turtle lays round eggs. Most of the eggs are about 1.6 inches (4 centimeters) across, but one or two may have a diameter twice that size. A typical nest holds about eighty eggs, but it contain as few as forty-eight eggs or as many as 156 eggs.
The females make only one nest per year. After laying her eggs, the female covers up at least the bottom hole, containing the eggs, and sometimes also the hole above it. The eggs hatch in about a month and a half; within a couple of days after hatching, the young make their way out of the nest. The sex of the hatchlings, or young turtles, depends on the temperature of the nest: extremely warm or very cool temperatures produce females, whereas temperatures that are more moderate, or mild, produce males. Scientists know few details about other activities of these large turtles.
South American river turtles and people Although it is now illegal to do so, some people still hunt and kill adults and sometimes even baby turtles for their meat and collect eggs for the oil they contain.
Conservation status The U.S. Fish and Wildlife Service lists this turtle as Endangered, which means that it is facing a risk of extinction in the wild. The World Conservation Union (IUCN) lists it as Lower Risk/Conservation Dependent, which means that its survival relies on sound conservation efforts. These listings result from the fact that humans have killed adults and destroyed their eggs over many decades. The turtle's range became smaller and smaller as the hunting and collecting continued. Efforts are under way to protect their nesting areas and to prevent further collecting of turtles or their eggs. ∎
FOR MORE INFORMATION
Burnie, David, and Don E. Wilson, eds. Animal: The Definitive Visual Guide to the World's Wildlife. London: Dorling Kindersley, 2001.
Pecor, Keith. "Pelomedusidae." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Pelomedusidae.html (accessed on August 6, 2004).