Flatback Sea Turtle Facts

Flatback turtles (Natator depressus) live primarily on the continental shelf of Australia and nest only on Australian beaches. Despite their limited range, probably less is known about this sea turtle species than the other six sea turtle species, which are more wide-ranging. Initial classification of flatback turtles led scientists to think they were related to Kemp's ridley or green sea turtles, but evidence in the 1980s led scientists to determine that they were a separate, genetically distinct species.

Description

The flatback turtle (also called the Australian flatback) grows to about 3 feet in length and weighs about 150-200 pounds. These turtles have an olive-colored or gray carapace and pale yellow plastron (bottom shell). Their carapace is soft and often turns up at its edge.

Classification

• Kingdom: Animalia
• Phylum: Chordata
• Class: Reptilia
• Order: Testudines
• Family: Cheloniidae
• Genus: Natator
• Species: depressus (referred to as depressa in the World Register of Marine Species (WoRMS))

Habitat and Distribution

Flatback turtles are found in the Pacific Ocean, primarily in waters off Australia and Papua New Guinea and occasionally off Indonesia. They tend to frequent relatively shallow, coastal waters less than 200 feet deep.

Feeding

Flatback turtles are omnivores that feed on invertebrates such as jellyfish, sea pens, sea cucumbers, crustaceans and mollusks, and seaweed.

Reproduction

Flatback turtles nest along the northern coast of Australia, from Western Australia to Queensland.

Males and females mate offshore. Mating often results in bites and scratches in the females' soft skin, which later heal. Females come ashore to lay their eggs. They dig a nest that is about 2 feet deep and lay a clutch of 50-70 eggs at one time. They may lay eggs every 2 weeks during the nesting season and return every 2-3 years to nest.

Although the egg clutch size of flatback turtles is relatively small, flatbacks lay unusually large eggs - even though they are a medium-sized turtle, their eggs are almost as big as those of the leatherback - a much larger species. The eggs weigh about 2.7 ounces.

The eggs incubate for 48-66 days. The length of time depends on how warm the nest is, with warmer nests hatching sooner. The baby turtles weigh 1.5 ounces when they hatch and carry undigested yolk, which will nourish them during their initial time at sea.

Flatback turtle nest and hatchling predators include saltwater crocodiles, lizards, birds, and crabs.

Once they reach the ocean, hatchlings do not go into deeper waters like other sea turtle species but stay in shallow waters along the coast.

Conservation

The flatback turtle is listed as Data Deficient on the IUCN RedList, and vulnerable under the Australian Environment Protection & Biodiversity Conservation Act. Threats include harvesting for eggs, bycatch in fisheries, nest and hatchling predation, entanglement in or ingestion of marine debris and habitat destruction and pollution.

References and Further Information

• Australian Government. EPBC Act List of Threatened Fauna.
• IUCN Marine Turtle Specialist Group. Flatback Turtle: Natator depressus .
• Red List Standards & Petitions Subcommittee 1996. Natator depressus. IUCN Red List of Threatened Species.
• Spotila, James R. Sea Turtles: A Complete Guide to Their Biology, Behavior and Conservation 2004. The Johns Hopkins University Press.
• SWOT. State of the World's Sea Turtles.
• Waller, Geoffrey, ed. SeaLife: A Complete Guide to the Marine Environment. Smithsonian Institution Press. Washington, D.C. 1996.