PIG-NOSE TURTLE: Carettochelyidae

PHYSICAL CHARACTERISTICS

This family has only one member: the pig-nose turtle. This is quite a large freshwater turtle, with an upper shell that can reach 22 inches (56 centimeters) in length and 14 inches (35.6 centimeters) in width. It may weigh up to 50 pounds (22.7 kilograms). It often swims with just its long snout sticking out of the water. That long snout is one of its most notable features. A fleshy, tube-shaped structure, it is similar in appearance to the snout of a pig. The shell of the pig-nose turtle is also different from that of most other turtles. The shells of most turtles are covered in bony plates, called "scutes" (SCOOTS). The pig-nose turtle, on the other hand, has a hard shell with a leathery covering.

This turtle also has long front legs that can stretch to a length almost half as long as the carapace (KARE-a-pays), or upper shell. The legs are flat and wide, like paddles or flippers. In fact, the limbs, or legs, more nearly look like the front legs of marine turtles, or turtles that live in the sea, than those of other freshwater turtles. Each front limb is tipped with two claws. In color, the turtle is mostly olive or gray on the tops of its limbs and high-domed upper shell and is whitish or yellowish on its bottom shell, or plastron (PLAS-trun), and on its chin, lower neck, and the undersides of its limbs. Males and females look very much alike, except for the male's larger tail. Besides their smaller size, juveniles (JOO-vuh-nuhls), or young turtles, differ from adults in the smoothness of the carapace. The juvenile carapace has a lumpy ridge, called a "keel," down the middle and is jagged along the edge, whereas the adult carapace does not have a keel anywhere except toward the back, and it is rounded at the edge.

At one time scientists believed that these turtles should be included with the side-necked turtles, a group known as the Pleurodira, rather than the hidden-necked turtles, or the Cryptodira. The better-known hidden-necked turtles pull their heads and necks straight back into their shells, whereas side-necked turtles fold their necks sideways. Scientists based their decision mostly on the location of the first turtle discovered back in the late 1800s. The original specimen (SPEH-suh-muhn), or example, was not whole; it was missing the part of its backbone that would have shown scientists whether it was a side-necked or a hidden-necked turtle. Because it was found in New Guinea and all of the other turtles known from New Guinea or from Australia at that time were of the side-necked variety, the scientific community assumed that the pig-nose turtle must be a side-necked turtle too. As more of these turtles turned up, however, scientists were able to take a closer look at the backbone, and they discovered that this species should be considered a hidden-necked turtle.

GEOGRAPHIC RANGE

This turtle is found in southern New Guinea and northern Australia.

A TURTLE BY ANY OTHER NAME

Although the family Carettochelyidae contains only one species, a person might think several exist. The reason is that the one species, Carettochelys insculpta, goes by the common names pig-nose turtle, pig-nosed turtle, Fly River turtle, and pitted-shelled turtle, to name just a few. They are one and the same turtle. Sometimes common names describe a body feature. For instance, "pig-nose" refers to the turtle's piglike snout. Common names can also identify the species' home. "Fly River," for example, names one of the places the turtle is found in New Guinea.

HABITAT

The pig-nose turtle usually lives in freshwater rivers, lakes, swamps, and other water bodies with shady shorelines. Sometimes it makes its home in saltier estuaries (EHS-chew-air-eez), or the wide parts at the lower end of rivers that link these water bodies to the ocean. They tend to prefer slower-moving and even unmoving waters that have soft bottoms of silt, or loose earth, on top of sand or gravel. The pig-nose turtle is sometimes also called Fly River turtle, because it is found in the Fly River in Papua, New Guinea. Scientists once thought the turtle lived only in New Guinea, but ten of the turtles were discovered in Australia's Daly River in 1970. They later were also found in the Alligator River system of Australia about 240 miles (386 kilometers) from the Daly River site, as well as other places in northern Australia.

DIET

Pig-nose turtles will eat just about anything they can find. They seem to prefer plants; they especially like figs and other fruits that drop from trees along the shoreline, but they will eat leaves, flowers, underwater plants, and the tiny plantlike growths called algae (AL-jee). They will also eat hard cones that require a solid bite to break open. They are not strict plant eaters, however. If the turtles find the wormlike young form of an insect, called a "grub"; a beetle; or an ant, they will eat those too. They will even partake of freshwater snails or other mollusks, crustaceans (krus-TAY-shuns) such as shrimp, or even dead mammals or birds.

BEHAVIOR AND REPRODUCTION

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.

PIG-NOSE TURTLES AND PEOPLE

Pig-nose turtle eggs often fall victim to local people in New Guinea, who find the turtle's beach nests and collect the eggs for food. In both New Guinea and Australia, local people trap, net, spear, fish, and simply collect the turtles by hand for their meat. The turtle also is popular in the international pet trade, although it is protected in Australia.

CONSERVATION STATUS

Collection of the pig-nose turtle for food and as pets, combined with loss or destruction of their habitat, or preferred living areas, have all threatened this turtle. The World Conservation Union (IUCN) has given its status as Vulnerable, meaning that it faces a high risk of extinction, or dying out, in the wild. Logging and farming can destroy waterside plants and drastically increase erosion (ih-ROH-zhen), or wearing away of the land, both of which can affect the turtles. In addition, the passage of water buffalo on their way to watering holes may also hurt the turtles' chances of survival. The buffalos crush the plants that the turtles eat, and they also trample across the beaches used by the turtles to lay their eggs. Heavy foot traffic can destroy the nests and the eggs inside.

FOR MORE INFORMATION

Books:

Cann, John. Australian Freshwater Turtles. Singapore: Beaumont Publishing, 1998.

Periodicals:

Bargeron, Michael. "The Pig-nosed Turtle, Carettochelys insculpta." Tortuga Gazette 33, no. 3 (March 1997): 1–2.

Web sites:

"Carettochelyidae." Herpetology: Reptiles and Amphibians. http://www.nafcon.dircon.co.uk/Carettochelyidae.htm (accessed on August 19, 2004).

"The Pig-nosed Turtle." University of Canberra Australia Applied Ecology Research Group. http://aerg.canberra.edu.au/pub/aerg/herps/fncchely.htm (accessed on August 2, 2004).