The pig-nosed turtle (Carettochelys insculpta), also known as the Fly River turtle, the pitted-shelled turtle, and the Warrajan, is a unique species of turtle native to northern Australia and southern New Guinea. C. insculpta is the only living member of the genus Carettochelys, the subfamily Carettochelyinae, and the family Carettochelyidae. Carettochelyidae is one of two families in the Trionychia, alongside Trionychidae (softshell turtles). Belonging to the diverse Testudines family, the Fly River turtle is one of the most ancient reptiles still alive today. This article delves into the fascinating aspects of the Fly River turtle, exploring its diet, habitat, and the conservation challenges it faces.
Distinctive Characteristics
The pig-nosed turtle is unlike any other species of freshwater turtle in its combination of traits. The pig-nosed turtle's unique features set it apart from other freshwater turtles. Its feet are flippers, resembling those of marine turtles. The nose looks like that of a pig, having the nostrils at the end of a fleshy snout, hence the common name. Fly River turtles use their disk-shaped snouts for snorkeling. Their distinctive noses can detect scents underwater and help locate prey such as larvae, shrimp, and snails. The carapace is typically grey or olive, with a leathery texture akin to that found in softshell turtles, while the plastron is cream-coloured. The carapace can vary between different shades of brown to dark gray. Unlike the soft-shelled turtles of the family Trionychidae, the pig-nosed turtle retains a domed bony carapace beneath its leathery skin, rather than a flat plate. Along the sides of the carapace are pale blotches which become less distinct with age. Males can be distinguished from females by their longer and narrower tails; males are known to have a longer and thicker tail. Females are a bit larger, but males have a longer, thicker tail. The top of the tail is covered with crescent shaped scales which diminish in size towards the tip; the male tail is longer and heavier with the cloaca midway along, whereas the female cloaca is at the base of the tail.
Habitat and Distribution
These turtles are found in northern Australia, Irian Jaya and southern New Guinea. Pig-nosed turtles inhabit freshwater and estuarine bodies of water, rivers, and thermal springs. Highly aquatic, they prefer freshwater rivers, and billabongs with a soft bottom and a depth of one to three metres with dense forests of broadleaf trees along the shores. The habitat water bodies tend to have forested banks and may also have fallen trees and branches, undercut banks, exposed tree roots and litter accumulation for cover. They move around according to the wet and dry seasons. During the wet season, they are found in deep, turbid water. These turtles move around according to the wet and dry seasons. During the wet season, they are found in deep, turbid water and pools.
The Fly River turtle gets its name from the Fly River in Papua New Guinea, where the species originates from. The species is particularly associated with large, slow-moving water bodies that have an abundance of aquatic vegetation.
Diet and Feeding Habits
Pig-nosed turtles are omnivorous but prefer to eat plants more than animal matter. The diet of pig-nosed turtles varies by life stage. Fly River turtles are opportunistic omnivores but are mainly herbivores. They eat mainly fruit such as figs and bush apples which fall from the shoreline trees. They also eat flowers, leaves and seeds too. They consume algae and submerged plants as well as insects, molluscs, crustaceans, fish, and mammals. The prominent nose is also a sense organ which can detect food sources, even in muddy water.
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Hatchlings initially rely on the left-over yolk of the egg. Juveniles consume insect larvae, small shrimp, and snails. Adults consume plants, such as flowers, fruits, and leaves found at the riverbank.
Reproduction and Life Cycle
Females of C. insculpta reach maturity at 18 or more years, and males around 16 years. Pig-nosed turtles are oviparous and breed during the dry season. Nesting occurs late in the dry season which would occur from September to January in New Guinea and from June to November in northern Australia. Before the nests are dug on sandy, coastal sea beaches, groups of females are seen in shallow water making individual forays onto the beach at night and even digging test nests. Eventually, all the females leave the water and begin to dig nests to a depth of 6 - 21cm using only their hind limbs. The nests are up to five metres from the shore. The clutch size is between seven and 39 eggs. In Australia, it has been noted that larger turtles lay larger and more numerous eggs. As well, very wet seasons are followed by larger and more numerous eggs being laid, probably because the females have better nutrition. Turtles in Australia have larger, and lay a greater number of eggs than those living in New Guinea. Incubation takes about 102 days but after the yolk is absorbed (approximately 69 days) hatching can be delayed up to 50 days as they stop developing until the rainy season begins which results in the nest becoming flooded. With the oxygen level greatly reduced hatching is triggered. It is thought they make their way to the fresh water rivers by seeking water with less and less salinity. Since the turtles hatch at the same time, there is safety in numbers. The sex of the turtles is determined by the heat of the nest with females being produced at higher temperatures. A steady 90 degrees Fahrenheit will produce both males and females. Cooler temperatures produce mostly males.
When the offspring are fully developed, they will stay inside the eggs in hibernation until conditions are suitable for emergence. Using environmental triggers, along with vibrations created by other hatching turtles in the same clutch, gives a better chance for survival. Using a universal trigger rather than simply waiting for incubation to finish means they all hatch at the same time. Females travel together when they are ready to lay eggs so they can communicate to each other which beaches are safe.
Behavior and Adaptations
The pig-nosed turtle is not completely aquatic. After the hatchlings reach the water, they do not leave this aquatic habitat except to lay eggs. Little is known about its general behaviour, as there have been few studies in the wild. Its known extreme aggression in captivity suggests the species is markedly more territorial than most other turtles and tortoises. One consultant noted they tend to be slow-moving and mellow but can bolt quickly when startled, and are generally non-aggressive with short necks & slow motion but can bite very hard if poked at. He noted some like a head rub in the water; your mileage may vary but be careful.
The elongated snout with its protruding nostrils allows them to inhale air without being exposed. In addition to breathing air at the surface through their noses, Fly River turtles are also able to breathe underwater by gulping water and absorbing the oxygen in the water. The plastron bones which are not fused enable more efficient respiration. As well, there are papillae lining the throat which can absorb oxygen when these turtles are swimming underwater. The counter shading colours if viewed from below appear white like the clouds and from above seem grey or olive like the reflection of the trees lining the rivers. The flipper shaped forelimbs, which they use in unison, ensure they have powerful forward locomotion. The hind limbs, with wide webbed surface along with the flap of skin that goes from the hind limbs to the tail, acts as a steering rudder which speeds their escape from predators like crocodiles. They can also use the front limbs individually which aids steering too. They have very strong jaws with massive muscle attachments at the back of the skull. This adaptation helps with defense and enables the eating of an omnivorous diet which includes crustaceans. The omnivorous diet is an adaptation to drastic shifts in amount and kinds of food available. These turtles are known to congregate under overhanging branches which drop fruit and nuts. Since they are found in coastal waters, they are adapted because of their size to tolerating a salty environment. They also use thermal springs in river beds to warm themselves. This behaviour intensifies during colder weather, and is especially true of gravid females.
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Threats and Conservation Status
C. insculpta experienced a population decline of more than 50% in the thirty years between 1981 and 2011. Wild populations of this turtle are declining rapidly because of illegal capture for the pet trade. Populations in New Guinea have declined almost 60 percent in the past 30 years, largely due to human consumption and the international pet trade. Technological advancements, such as outboards, have made hunting turtles easier. In addition, an increase in commercial activity, such as logging, mining and fishing, is bringing human populations into closer contact with these turtles.
Illegal harvest and trafficking of pig-nosed turtles continues on a large scale. Although the pig-nosed turtle is protected in Indonesia under Law No. 5/1990 on Natural Resources and Ecosystems Conservation, smuggling occurs. Some 11,000 pig-nosed turtles captured from smugglers were released into their habitats in the Wania River, Papua Province, Indonesia, on 30 December 2010. In March 2009, more than 10,000 pig-nosed turtles retrieved from smugglers were also released into the Otakwa River in Lorentz National Park. 687 pig-nosed turtles were seized at an Indonesian airport in March 2013.
In Australia, the biggest threat to this species is habitat loss and degradation. Agricultural practices, such as the extraction of water for irrigation and pastoral activities, reduces the flow of water and changes the siltation of rivers. Since the introduction of water buffalo to northern Australia, nesting sites are being trampled and the water vegetation that turtles eat, especially in the dry season, is being eaten by the water buffalo. Among the more prominent threats is the introduction of water buffalo and other livestock. Feral buffalo trample over nesting sites, eggs and hatchlings. In Papua New Guinea the indigenous people collect the eggs as well as capture the turtles resulting in a marked decrease of these turtles in the western Papua New Guinea area.
As the last member of the Carettochelyidae family, the Fly River turtle is of particular importance and could serve as a flagship species. They are protected in Australia in the Kakadu National Park. Exportation of Fly River turtles has been banned.
Captive Care
Pig-nosed turtles have become available through the exotic pet trade, with a few instances of captive breeding. While juveniles are small and grow slowly, their high cost and large potential size makes them suitable only for experienced aquatic turtle keepers. They tend to be shy and prone to stress. They get sick easily, which can cause problems with their feeding, but they are known to eat commercially available processed turtle pellets or trout chow, as well as various fruits and vegetables.
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For adults, minimum 200 gallon tank (mine's 7'x2'x2'), and much larger preferred. In the minimum, the turtle may have to tuck its head in to sit facing forward! A proper enclosure could weigh a few tons, so planning must include flooring capable of supporting it. Aquariums in this size range will be acrylic. Both adults & young juveniles tolerate water a few feet deep, although particularly for the latter there should be 'rest areas' (i.e.: driftwood, synthetic logs, etc…) near the surface. Recommended only as a solo turtle.