Abroad with the Broad Shelled Turtle
Chelodina expansa, more commonly known as the broad shelled turtle, is one of the largest freshwater turtles in Australia. The length of their shells can reach up to 50 cm (19.6 in), and their neck accounts for an additional 60-80% of their total length. Because of this length, C. expansa tucks its head in sideways as opposed to pulling it directly into its shell. At maximum, females reach a mass of 6 kg (13.2 lbs), while males only typically weigh about 4 kg (8.8 lbs). The top of the shell, or carapace, is dark brown or green, while the underside is a light cream; the same is true for the broad shelled turtle's head, neck, and legs. The feet are webbed, and have large claws which help adults to dig or fend off predators.
While they spend the winter buried in the mud, the broad shelled turtle is most active during the summer months, from November to March. During this time they are almost entirely aquatic, rarely emerging from the water even to bask. This species lives throughout the river basins of eastern Australia, and can be found in rivers, dams, lakes, and wetlands with plenty of vegetation cover. C. expansa is entirely carnivorous, feeding on crustaceans, aquatic insects, fish, and frogs via ambush, and carrion whenever it can find it. To locate prey, they have a keen sense of smell. Adults are not usually predated upon due to their thick shells and sharp claws, but eggs and juveniles are often prey for foxes, dingos, birds, rakalai, and large fish.
C. expansa nests in the winter, beginning in late February or March. Outside the mating season, individuals are generally solitary, but aggressive territoriality has not been observed. When mating time roles around, males seek out females to mate with; following the encounter, the female climbs out onto the bank and digs a nest for a clutch of anywhere from 5 to 28 eggs. To seal the nest, she then slams her body into the re-piled sand and mud, compacting it into a plug that will remain intact until the following year.
Incubation takes about 360 days, though some nests have been recorded as hatching at 500 days; this process is exceptionally slow due to the two periods of diapause, or developmental delays, that embryos pass through in order to survive the winter. Juveniles hatch in the spring, and emerge from the nest at the first heavy rain. It's unknown how long these turtles can live in the wild, but given their slow growth rate and adult invulnerability it's likely that they can live in excess of 20 years.
Conservation status: The IUCN consideres the broad shelled turtle to be Near Threatened, due primarily to habitat loss and high rates of nest predation by introduced foxes.
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Photos
Claire Treilibs
Catherine Heuzenroeder
Shanna Bignell via iNaturalist
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