The Flatback Sea Turtle (Natator depressus) is a marine reptile found exclusively on the continental shelf of Australia, Papua New Guinea, and Indonesia. It is the sole member of its genus and has the most geographically restricted range of all seven sea turtle species. The flatback’s name comes from its distinctively low-domed, flattened shell, unlike the highly curved carapaces of its relatives. The International Union for Conservation of Nature (IUCN) lists the species as Data Deficient, indicating insufficient scientific information to determine its global conservation status. It is considered Vulnerable under Australian national legislation due to threats like coastal development and fishing bycatch.
Primary Food Sources
The Flatback Sea Turtle’s diet is overwhelmingly carnivorous, preferring soft-bodied invertebrates found on the seafloor. Stomach content analyses frequently reveal consumption of sea cucumbers, which are slow-moving echinoderms abundant in soft-bottom habitats. They also consume cnidarians, such as jellyfish and sea pens, taking advantage of this gelatinous, easily digestible prey.
Their diet extends to soft corals, mollusks, and crustaceans like prawns and shrimp. Although occasional consumption of seagrasses or other plant material is noted, the diet remains dominated by animal matter, reflecting adaptation to the benthic environment.
Foraging Behavior and Habitat
Flatback Sea Turtles live their entire lives within the neritic zone, the shallow water over the continental shelf, without an oceanic migratory phase. They favor shallow, coastal habitats, including bays, lagoons, and estuaries, often characterized by turbid, soft-bottomed substrates. This habitat preference is directly linked to the distribution of their invertebrate prey.
The turtles are benthic feeders, meaning they forage along the seabed. Their strategy involves cruising close to the bottom, using suction and gentle biting to capture soft prey. This contrasts with species that forage in the water column or on hard coral reefs.
Dietary Comparison to Other Sea Turtles
The Flatback’s diet of soft invertebrates distinguishes it within the sea turtle family, which exhibits a broad range of specialized feeding niches. The Green Sea Turtle is primarily herbivorous as an adult, feeding on seagrasses and algae using a finely serrated beak. The Hawksbill Sea Turtle is a specialist spongivore, relying on a narrow beak to consume sponges found in reef crevices.
Other carnivores, like the Loggerhead Sea Turtle, use massive heads and powerful jaws to crush hard-shelled prey such as crabs and whelks. The Flatback’s reliance on soft-bodied prey suggests its jaw structure is adapted for a less forceful, more suction-based capture method, rather than crushing tough materials.