The Flatback Sea Turtle (Natator depressus) is a unique marine reptile distinguished by its low-domed, smooth carapace, which lacks the hard protective layer found on most other sea turtles. This species is the only sea turtle whose entire breeding range is restricted to the continental shelf waters of a single nation. Unlike its relatives that traverse vast open oceans, the Flatback lives almost exclusively within the shallow, tropical, and subtropical seas surrounding Australia.
Overall Geographic Distribution
The Flatback Sea Turtle possesses the most restricted geographic range of all seven sea turtle species worldwide, centering on the northern waters of the Australian continental shelf. Its distribution extends along the coastlines of Queensland, the Northern Territory, and Western Australia, predominantly north of the Tropic of Capricorn. The core foraging habitat includes the Arafura Sea, the Timor Sea, and the Gulf of Carpentaria, which are all shallow maritime areas lying over the continent’s submerged shelf.
While the species is fundamentally Australian, its foraging range sometimes extends into the territorial waters of neighboring countries. Flatbacks have been sighted in the coastal areas of Southern Papua New Guinea and southern Indonesia, particularly near the islands of the Aru Archipelago. These sightings are extensions of their feeding grounds, but the vast majority of their life is spent within the coastal zone of the Australian mainland, rarely venturing into deep pelagic waters.
Critical Nesting Locations
All known nesting sites for the Flatback Sea Turtle are located on the sandy beaches of Australia, making the country the sole breeding ground for the species. Nesting activity is concentrated along the northern half of the continent, with significant rookeries found in both the east and the west. In Western Australia, important nesting areas are situated on the North West Shelf, including Barrow Island and Mundabullangana Beach, which support thousands of nesting females annually.
Further east, major breeding aggregations occur in the Gulf of Carpentaria and the Torres Strait. Crab Island, off the northwest coast of Cape York Peninsula in Queensland, is recognized as the largest single Flatback rookery. Other significant eastern sites include Curtis Island and Mon Repos near Bundaberg, which marks the southernmost regular nesting location. These beaches are typically characterized by low-energy, soft sand and often lie behind broad intertidal zones.
Habitat Requirements and Water Depth
The Flatback’s habitat selection is driven by a strong preference for shallow, nearshore marine environments, which explains its limited geographic spread. Unlike species that utilize the open ocean, the Flatback remains strictly associated with the continental shelf, a preference reflected in their common presence in waters generally less than 60 meters deep. This shallow water focus also means they often inhabit turbid, or cloudy, coastal areas, including bays, lagoons, and estuaries.
This dependency on the shelf is tied directly to their diet and feeding strategy. Flatbacks are carnivorous, feeding primarily on soft-bodied invertebrates like sea cucumbers, jellyfish, and mollusks, which are abundant in the soft, muddy, or sandy seafloors of these coastal zones. Because the turtles do not undergo an oceanic dispersal phase, even the hatchlings remain in the inshore waters, utilizing the same shallow environment as the adults.