Australo-American Side-Necked Turtles: Chelidae
AUSTRALO-AMERICAN SIDE-NECKED TURTLES: ChelidaeMATAMATA (Chelus fimbriatus): SPECIES ACCOUNT
Australo-American side-necked turtles are a varied group of medium-sized to rather large turtles with necks that fold sideways under their shells, rather than retracting, or pulling backward, into the shell. In some cases, the neck can be as long as the upper shell, or carapace (KARE-a-pays) or even longer. A few side-necked turtles, however, have very short necks. Depending on the species, the upper shell of adults can range in length from 6 to 19 inches (15–48 centimeters). Most turtles have dark upper shells, and a few have brightly colored lower shells, or plastrons (PLAS-truns); heads; necks; legs; or tails. These parts of the body may be red, orange, or yellow. Often, the juveniles (JOO-vuh-nuhls), or young turtles, are the most brightly colored; the color fades as they age. Some of these turtles have glands, or special organs, that give off a bad smell, which wards off predators, or other animals that hunt and kill the turtles. Males and females look quite similar, although the females in most species are larger than the males. In a few cases, the males have especially long tails that they may use in mating with females.
The Australo-American side-necked turtle typically lives in freshwater lakes, ponds, rivers, and streams that are always filled with water, but they spend part of their time in wetlands or flooded forests that are wet for just a short period of time each year. Only one species, the New Guinea snake-necked turtle, can be found in estuaries (EHS-chew-air-eez), or that part of a river where it meets the sea, and other areas of partially salty water.
Most members of this family eat meat or both meat and plants. The adult northern Australian snapping turtle may live only on vegetation, including algae (AL-jee), which are tiny plantlike growths that live in water, and the leaves and fruits of waterside trees they find during the dry season. The meat eaters may feed on worms, insects, fishes, and frogs. Some also eat mollusks, such as clams; crustaceans (krus-TAY-shuns), such as shrimp; or dead animal matter. Many of the mollusk eaters have large, broad jaws that they use to crush their prey's shell. Other species, particularly those that dine on fishes, have long necks that burst through the water when they are going after prey. As the turtle opens its mouth, both water and prey rush in. The turtle then spits out the water and swallows the animal.
OUT OF ANTARCTICA?
Australo-American side-necked turtles, both living animals and fossils (FAH-suhls), or remains of animals that lived long ago, are found in Australia and South America, but nowhere else. The large gap in their geographic range makes scientists believe that the South American and Australian species are related through a common ancestor that lived long ago in Earth's history, when the two continents were still linked together by what is now Antarctica. This common ancestor, which spread across Antarctica, could have migrated, or traveled, into the areas that eventually split off to become South America and Australia.
BEHAVIOR AND REPRODUCTION
Many Australo-American side-necked turtles feed mainly at night and spend their days basking, or warming themselves, in the sun. When a dry spell strikes, some species bury themselves in the mud and become inactive until the rains come. Stein-dachner's turtle is one example. This turtle can survive droughts (DROWTS), or dry spells, as long as two years by living off water that it stores inside its body in sacs, or pouches, called "accessory bladders." In cooler climates, some also hibernate, or become inactive, during the winter months. Most hibernate alone, but the common snake-necked turtle of Australia hibernates in groups. Other turtles, like the Argentine side-necked turtle, will take occasional breaks from hibernation (high-bur-NAY-shun) on warm days, when they venture out to a sunny spot and stretch out in the sun.
Except for the most tropical of species, which may breed all year, side-necked turtles mate in the early spring. Depending on the species, the female lays one to twenty-eight round or oblong eggs in a shallow depression, or hollow, under leaves; in an underground nook, or sheltered space; or in some other nest. The female of one species, the northern snake-necked turtle, lays her eggs underwater in the muddy bottom of a temporary pond. The eggs develop only after the pond dries up, and the young hatch before the next rainy season arrives. For those eggs laid in underground nests, the young hatch out of the eggs but stay in the nest until the rains come to soften the soil above them. Then they claw their way to the surface and take their first steps aboveground. The outdoor temperature has no effect on whether the eggs hatch into males or females, as it does with many other turtles.
AUSTRALO-AMERICAN SIDE-NECKED TURTLES AND PEOPLE
Some people hunt and kill these turtles for their meat, which they use as food. Although certain species are kept as pets, the pet trade does not harm their survival.
The World Conservation Union (IUCN) lists three species as Critically Endangered, or facing an extremely high risk of extinction, or death, in the wild, and four as Endangered, or facing a very high risk of extinction. Six are Vulnerable, meaning that they face a high risk of extinction, and eight are Near Threatened, meaning that they face the risk of becoming extinct in the near future. One of the Critically Endangered turtles is the western swamp turtle, of which fewer than four hundred individuals survived in 2003, and all live in a few small areas of Brazil. Another turtle, called Hoge's side-necked turtle, is also very rare, existing in just a few spots in the same country. The U.S. Fish and Wildlife Service lists two species as Endangered. The main reason for concern about these species is loss of their habitat, through either damage or complete destruction. Efforts are under way to save these threatened species from extinction by removing them from the wild and breeding them in captivity, possibly for future release back into the wild.
Physical characteristics: The matamata is one of the larger side-necked turtles as well as one of the biggest freshwater turtles; its dark upper shell can reach up to 18 inches (46 centimeters) in length, and it can grow to a weight of 27 pounds (12 kilograms). It has a flat, lumpy, triangular head, with a rough fringe, or edging. The head sticks out from a flat, knobby shell. Two tiny eyes dot the head. The turtle's upper shell is mostly dark brown. Juveniles have a pinkish-orange lower shell. Often, only the turtle's head is visible in the water, and sometimes just its tube-shaped nose breaks the water's surface as the turtle moves about underwater. Females usually are larger than males.
Geographic range: The matamata lives in northern South America.
Habitat: These turtles prefer still or slow-moving freshwater habitats, or areas in which to live, but some are able to live in saltier waters. Although matamatas sometimes live in swift-moving rivers, they stay out of the current and move beneath underwater banks or logs.
Diet: The matamata is mainly a fish-eating species; it ambushes, or attacks, its prey by settling on the bottom and waiting for a fish to approach. Water currents brush the turtle's head fringes back and forth, and many scientists think that this movement attracts fishes. When the prey is close enough, the turtle darts out its head while enlarging its neck and mouth, and sucks in a great gulp of water along with the prey. The turtle then releases the water from its mouth and eats the fish. Some turtle experts believe that the skin flaps, or fringes, on the head may also help the turtle sense water movement and know when prey species are swimming through the murky, or dark, water of muddy ponds.
Behavior and reproduction: Rarely seen, this side-necked turtle often travels through the water by walking along the bottom and only occasionally takes an awkward swim. Juveniles are known to bask, but adults do not. Once a year, the females make nests, sometimes in riverbanks, where they lay eight to twenty-eight round eggs that measure 1.4–1.6 inches (3.6–4 centimeters) in diameter, or width. The eggs hatch more than six months later. Little is known about courtship, mating, or other activities of these turtles in the wild.
Matamatas and people: Matamatas are quite popular in the pet trade, probably because of their unusual fringed heads.
Conservation status: This turtle is not threatened. ∎
FOR MORE INFORMATION
Burnie, David, and Don E. Wilson, eds. Animal: The Definitive Visual Guide to the World's Wildlife. London: Dorling Kindersley, 2001.
Cann, John. Australian Freshwater Turtles. Singapore: Beaumont Publishing, 1998.
Pritchard, Peter C. H., and Pedro Trebbau. The Turtles of Venezuela. Athens, OH: Society for the Study of Amphibians and Reptiles, 1984.