Pig-nose turtles

(Carettochelyidae)

Class Reptilia

Order Testudines

Suborder Cryptodira

Family Carettochelyidae

Thumbnail description
A turtle of moderate size with paddle-like forelimbs, a rough, leathery shell, and a pig-nose snout

Size
Up to 22 in (56 cm) and 50 lb (22.5 kg)

Number of genera, species
1 genus; 1 species (Carettochelys insculpta)

Habitat
Rivers and lakes

Conservation status
Vulnerable

Distribution
Southern New Guinea and northern Australia

Evolution and systematics

Although pig-nose turtles represent a very distinctive family, they are most closely related to the softshell turtles (Trionychidae). This turtle is also commonly known as the Fly River turtle and pitted-shelled turtle (New Guinea). No subfamilies are recognized.

The taxonomy for this species is Carettochelys insculptus Ramsay, 1886, Fly River, Papua New Guinea.

Physical characteristics

This turtle is readily distinguished by its rough leathery shell (without scutes), its paddle-like forelimbs (each with two well-developed claws), and its blunt, piglike snout. The carapace of the adult has a smooth margin and the keel along the midline of the carapace is only obvious posteriorly; however, small juveniles have a serrated shell margin and a knobby midline keel. The adult bony carapace is well developed, and not reduced as in the softshell turtles.

Distribution

The pig-nose turtle inhabits the river systems of southern New Guinea (Papua and Irian Jaya) as well as along the northern coast of Australia's Northern Territory.

Habitat

These turtles primarily inhabit freshwater ecosystems (rivers, lakes, lagoons, swamps) with slow-moving or still waters and soft bottoms. They also are found in estuaries associated with these systems.

Behavior

Little is known about the behavior of this species, since they emerge from the water only to nest. However, they are known to aggregate around food sources. In northern Australia, the average home ranges for females and males cover about 5 mi (8 km) and 2 mi (3 km) of river length, respectively. Adults will also thermoregulate underwater by lying over small thermal springs on the river bottom.

Feeding ecology and diet

Pig-nose turtles are opportunistic omnivores, with herbivorous tendencies. Their principal food is the fruits of shoreline trees, although they also eat their leaves and flowers as well as algae and other submergent plants. Animal foods include insect larvae, mollusks, and crustaceans. Fish and mammals are also eaten, but probably as carrion.

Reproductive biology

Courtship and mating have not been described. Nesting occurs late in the dry season, from September to December or possibly even January in New Guinea, and from June, July, or August (depending on locality) to October or November in northern Australia. The species produces multiple clutches, but the maximum number per year is uncertain. On the Daly River in northern Australia, females lay two clutches per season, but only nest every other year. Nests are excavated by the hind limbs at sites 20 in (50 cm) to 16 ft (5 m) above the water level. The brittle-shelled eggs are spherical, 1.5–2.1 in (38–53 mm) in diameter, and 1.1–1.6 oz (32–46 g) in mass. Clutch sizes range from 7 to 39 eggs, the number probably related to the female's size. At 86°F (30°C) embryos develop to full term in 64 to 74 days; however, they then begin estivating within the egg until rainy season flooding stimulates their hatching. Thus, the total incubation period for natural nests is 86 to 102 days. Sex is determined by temperature during the middle third of incubation, with only females produced at high temperatures and only males at low ones.

Conservation status

This species is listed as Vulnerable on the IUCN Red List. It may be negatively affected by the trampling of its nests by water buffalo and by fishing, logging, intensive grazing, and agriculture.

Significance to humans

Pig-nose turtles are consumed by people across their range. In New Guinea, indigenous peoples collect the eggs from nesting beaches and capture the turtles in nets, in traps, with spears, and by hand. In Australia, the turtles are speared, fished, and grabbed by hand, although the eggs apparently are not harvested.

Resources

Books

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

Periodicals

Doody, J. S., R. A. Sims, and A. Georges. "Use of Localized Thermal Springs to Elevate Body Temperatures by the Pig-Nosed Turtle, Carettochelys insculpta." Chelonian Conservation and Biology 4 (2001): 81–87.

Doody, J. S., J. E. Young, and A. Georges. "Sex Differences in Activity and Movements in the Pig-Nosed Turtle, Carettochelys insculpta, in the Wet-Dry Tropics of Australia." Copeia 1 (2002): 93–103.

Georges, Arthur, and Mark Rose. "Conservation Biology of the Pig-Nosed Turtle, Carettochelys insculpta." Chelonian Conservation and Biology 1, no. 1 (1993): 3–12.

John B. Iverson, PhD