Flatback turtles are unique as the only sea turtle species not to have an oceanic phase as hatchlings. As such they remain over the Australian continental shelf and although they are found in Indonesia and Papua New Guinea they only nest on Australian beaches. Previously identified as being a close relative of the green turtle, DNA testing now shows that they are a unique species.

Scientific Name
Natator depressus

Conservation status
Flatback turtles are classified as Data Deficient by the International Union for Conservation of Nature (IUCN) though previously they were listed as vulnerable. This change in classification in no way implies flatback populations are recovering. It simply indicates a lack of recent research into their abundance and distribution.

Description
Adults’ carapace (top of shell) is low-domed with upturned edges. The carapace is olive green to grey and the flippers and head are grey. Underneath they are a creamy yellow colour.  The soft skin covering the carapace is easily damaged and can show the scars of mating or collisions with boats. Adult carapace length averages 0.9 metre.

Hatchlings share the adult’s counter shading and have a white border to the carapace and black outlines around each scute (bony external plate on the shell).

Distribution
Flatbacks remain on the Australian continental shelf and can be found in tropical Australian waters, Indonesia and Papua New Guinea. They only nest on tropical and subtropical Australian beaches.

Habitat
Flatbacks prefer subtidal coastal waters away from reefs. They feed mainly in shallow, murky bays inshore of the outer Great Barrier Reef, and similar habitats around northern Australia.

Lifecycle
The Flatback turtle is unique in that hatchlings remain in coastal waters and do not have an oceanic phase. Surprisingly as they stay close to shore, little is known of this stage of their lives. Females nest every 2 to 3 years on beaches across Northern Australia.

Diet
Flatback turtles are carnivorous, feeding mainly on soft-bodied invertebrates such as soft corals, sea pens, sea cucumbers and jellyfish.

Nesting
Flatbacks lay few but relatively large eggs. The reason is unknown, though perhaps their strategy is that fewer predators are able to make a meal of bigger hatchlings. Ghost crabs struggle to hold flatback hatchlings for example. Also the larger the egg the greater its ability to withstand high temperatures and flatback nests can have the highest temperatures found in any turtle’s nest. Hatching success can be as high as 95% if the nest is undisturbed. However a variety of predators – native and feral – can seriously reduce hatchling numbers.