The breeding season of the flatback turtle varies depending on the location. For example, in southern Queensland, the flatback turtle begins mating in October and nesting occurs between October and January with a peak in December, while in northern Australia the flatback turtle nests between June and August. Each nesting season, the female lays between two and three clutches, 15 days apart (3).
The female hauls herself out of the ocean, usually at night (2), and finds a suitable spot on the beach; most nests are constructed on top of dunes or as high as possible on seaward slopes (7). A hole is then excavated using alternate sharp jerks of the hind-flippers to throw sand away. Into the hole, measuring around 22 centimetres across and 30 centimetres deep, the female lays an average of 50 to 60 eggs within ten minutes. The hole is then filled with sand, and further sand is piled on top to form a mound. The female then leaves for the sea (2).
Around six weeks later, the incubating eggs hatch and the hatchlings emerge from the nest chamber (2). The temperature at which the eggs have been incubating is critical; below 29°C and the clutch will be male, above 29°C and females are produced (3). The hatchlings instinctively head for the sea, fanning out as they run to the water rather than following each other (2). Unlike other sea turtles, flatback turtles do not spend any part of their life in the deep ocean, remaining instead in the surface waters of the continental shelf (3). Flatback turtles spend much of their day floating on the sea surface, basking in the sun, and it is not unusual to see birds resting on the turtle’s back (2).
While little is known about the diet of the flatback turtle (3), it is thought to be a predominantly carnivorous species (7), feeding on organisms that are found on the sea floor. This includes cuttlefish, hydroids, soft corals, crinoids, molluscs and jellyfish (3).