Pig-nosed turtle  (Carettochelys insculpta)

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (3).

The pig-nosed turtle is the sole surviving member of an ancient and once widespread family (4) (5) (6) (7), and is unusual in that, with its long, paddle-like forelimbs, it more closely resembles the marine turtles than other freshwater turtle species (8) (9). A large and heavy-bodied turtle (7) (9) (10), it is superbly adapted to swimming (9). In addition to the flipper-like forelimbs, the webbed hind limbs are used for both paddling and steering, while the carapace is quite streamlined, and lacks hard protective scutes, instead being covered with soft, pitted, leathery skin. Perhaps the most unique feature of this species, which leads to its common name, is the elongated, fleshy, pig-like snout, which acts like a snorkel, allowing the turtle to breathe while the rest of the body remains submerged (4) (7) (8) (9) (10).

The body of the pig-nosed turtle is grey, olive-grey or grey-brown above, whitish below, and there is a whitish blotch behind each eye (4) (7) (8) (9) (10). The male is generally slightly smaller than the female, with a longer, thicker tail (7) (8) (9). Juveniles often have a somewhat translucent underside, through which the underlying blood vessels may show, lending it a pinkish colour, and may also bear small light patches on the carapace (7) (9). The tail bears a single line of scales on the upper surface, and each limb bears two claws (7) (8).

The pig-nosed turtle occurs in southern Irian Jaya (Indonesia), southern Papua New Guinea, and the major river systems of the northwestern Northern Territory in Australia (1) (7) (8) (9) (11). One of the alternative names of this species, ‘Fly River turtle’, comes from the Papuan river where it was first discovered (9).

The pig-nosed turtle is almost entirely aquatic, with only the female ever leaving the water to nest. The species inhabits rivers and streams, as well as lakes, swamps, lagoons and water holes, usually in water up to seven metres deep. It can also tolerate brackish water to an extent, and is sometimes found in estuaries and river deltas (4) (7) (8) (9).

The pig-nosed turtle feeds on a wide variety of foods, including aquatic plants and the leaves, flowers, fruits and seeds of riverside vegetation, as well as insects, crustaceans, molluscs, worms and fish. Mammals may also sometimes be taken, possibly as carrion (4) (7) (8) (9) (12), and younger individuals tend to eat a higher proportion of animal material than adults (9). In addition to its use as a snorkel, the unusual snout is equipped with sensory receptors that allow the turtle to locate prey in murky water or sand (9). The pig-nosed turtle does not swim like other freshwater turtles, but instead ‘rows’ itself through the water with the paddle-like forelimbs, in the manner of marine turtles (8). It also occupies a much larger home range than other freshwater turtles, covering up to ten kilometres of river, and may move into adjacent wetland areas during the wet season (13).

The pig-nosed turtle reaches maturity at about 14 to 16 years, at a carapace length of around 30 centimetres (9). Nesting usually occurs in the dry season, from July to November in Australia, or September to February in Papua New Guinea (7) (8) (9) (12), and each female will lay two clutches a year, but only breed every other year (14). The nest is built at night, the female excavating a shallow chamber in sand or mud close to water, into which are laid around 4 to 39 white, spherical eggs (7) (8) (9) (12). The sex of the offspring is determined by the temperature at which the eggs are incubated, with higher temperatures producing females, and lower temperatures producing males (7) (8) (9) (15). Incubation lasts from around 64 to 102 days (7) (8) (15), but, unusually, the fully developed embryos often delay hatching, entering a period of arrested development until stimulated to hatch by rain or flooding, which usually signals the start of the wet season (4) (7) (15). Hatchlings measure between 5.2 and 5.9 centimetres in length (8).

This unusual turtle is under threat from overharvesting for its meat and eggs, and from over-collection for the international pet trade, particularly in Indonesia and Papua New Guinea (1) (5) (8) (16) (17). Although exportation from these countries is officially regulated, an illegal market still exists (7) (9), and the problem has been exacerbated by the introduction of modern technology such as outboard motors (6) (7). In Australia, the main threat to the species is habitat loss and alteration (1), with nest sites having been trampled and riverside vegetation destroyed by water buffalo (6) (7) (9) (10), although numbers of this introduced species are now being reduced (7). Agricultural and pastoral activities are causing changes in vegetation and water flow, and increased siltation of rivers (6) (7) (10) (16), while activities such as mining, mineral and oil exploration, logging and fishing are also potential problems (6) (7) (8). The pig-nosed turtle is still a relatively poorly known species (16), and its rather restricted range and predictable nesting habits make it particularly susceptible to overexploitation (6) (7).

In addition to its listing on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning international trade in the species should be carefully controlled (3), the pig-nosed turtle is legally protected in Australia, where it occurs in Kakadu National Park in the Northern Territory (7). In light of planned agricultural development in the Daly River system in Australia, a monitoring plan was developed to assess the potential impacts on the pig-nosed turtle (18). However, further research is needed to better determine the status and distribution of the species in Australia, and to identify critical areas of habitat for future management and protection (6) (7) (16).

Domestic exploitation of the pig-nosed turtle in Papua New Guinea is largely unregulated (7), and additional research is required into population trends, the level of exploitation, and the potential for sustainable harvest systems (6) (7) (8) (16). As the sole remaining member of its family, the pig-nosed turtle is of considerable interest to scientists and conservationists, and may also serve as an important flagship species for conservation (18), helping to conserve not only this unique turtle but also the other species which share its habitat.

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about the conservation of this and other turtle species see:

• Barone, S. (2004) The pig-nosed turtle, Carettochelys insculpta, underwater glider. Reptilia, 33: 56-60. Available at:
  http://www.reptilia.net/html_english/index.htm
• Turtle Conservation Fund:
  http://www.turtleconservationfund.org/
• Carettochelys.com - Australasian Turtle Information:
  http://www.carettochelys.com/
• Asian Turtle Conservation Network:
  http://www.asianturtlenetwork.org/index.htm