Species: N. depressus
Conservation status: Data Deficient (IUCN 2.3)
Flatback sea turtles are found in coastal waters, and are reported to bask in the sun at the surface, sometimes with sea birds perched on their backs.
These turtles prefer shallow, soft-bottomed sea bed habitats that are far from reefs. They only very rarely leave the shallow waters of the continental shelf, and nest only in northern Australia, where beaches on small offshore islands are the most important sites. This is in stark contrast to the behaviour of all other marine turtle species, except for Kemp's ridley.
This species is within a monotypic genus, Natator, in the family Cheloniidae; the name means "swimmer" in Latin. Depressus, the specific name, means "flat" in Latin. It refers to the flatness of the flatback's shell. The Bardi people called this animal barwanjan, and it was known to the Wunambil as madumal.
Flatback turtles are usually found in bays, shallow, grassy waters, coral reefs, estuaries, and lagoons on the northern coast of Australia and off the coast of Papua New Guinea.
The species may feed off Indonesia and Papua New Guinea, but it nests only in Australia. Nesting occurs across the northern half of Australia, from Exmouth in Western Australia to Mon Repos Conservation Park in Queensland. The most significant breeding site is Crab Island in the western Torres Strait. Breeding may also occur on the islands of the southern Great Barrier Reef, and on mainland beaches and offshore islands north of Gladstone.
The flatback has a flat body and smooth carapace (shell) with upturned edges. It is also recognized by a single pair of prefrontal scales at the front of the head, and 4 pairs of costal scutes on the carapace.
Adults flatbacks may reach 90kg and up to 1m in length.
The carapace of this turtle is yellow-grey or a green-grey, while the plastron (underside) is usually pale yellow.
The nesting season runs from October to February in Queensland's Northern Territory, but may extend to the entire year in Northwestern Australia. Flatbacks can nest up to 4 times in a season, and the interval between each nesting event may be anywhere between 13 and 18 days. An average of 50 eggs are laid each time.
The flatback turtle is predominantly carnivorous, feeding on squid, sea cucumbers, soft corals, and mollusks.
What are the main threats?
The main threats which affect marine turtles are:
Habitat loss and degradation
Collection of eggs and meat for consumption
Incidental capture (bycatch)
Flatbacks are also threatened by predation by foxes, feral dogs and pigs and more recently the occurence of green turtle fibropapillomatosis. Its restricted range means that the flatback is extremely vulnerable to habitat loss, especially of breeding sites, but the most serious threat appears to be incidental catch by fishing vessels operating in the area.