Flatback Sea Turtle
IUCN Listing Status: Unknown - Data Deficient
The Latin species name "depressa" means flat. This name refers to the flatness of this sea turtle's carapace.
As adults, the flatback has a yellow-grey or a green-grey colored oval shaped carapace. The plastron is typically a pale yellow. There is a yellow band underneath and outlining the marginal scutes. Adults may weigh as much as 198 pounds (90 kilograms) and measure 39 inches (100 centimeters) long. There is a single pair of prefrontal scales on the head. The carapace has four pairs of costal scutes. The head is relatively larger than that of a comparable sized green turtle and is more triangular in shape. Similar to the Leatherback sea turtle (Dermochelys coriacea), the flatbacks have a soft shell.
Hatchling flatbacks are a light tannish-grey color with bright black outlines along the carapace scutes. The plastron is white. They also have white-tan fringing along the marginal scutes and flipper edges.
At one time, this turtle was considered a relative of the green sea turtle, but it was returned to it's own genus, Natator, by Limpus et al. (1988) and Zangerl and Hendrickson (1988).
Habitat and Distribution
The flatback sea turtle inhabits coastal coral reefs and grassy shallows of Australia and Indonesia. It feeds primarily on sea cucumbers and crustaceans, and is found primarily in the northern coastal area of Australia and the Gulf of Papua New Guinea. This species nests exclusively in Australia.
According to Limpus et al. (1988), the flatback nests up to 4 times per season at 13 to 18 day intervals. The flatbacks lay relatively small clutches of eggs (average 50).
The nesting season in Queensland Northern Territory is from October - February, but it may nest year-around in Northwestern Australia.
Unique Traits of the Flatback
The saltwater crocodile (Crocodylus porosus) is a known predator of nesting flatback sea turtles. Crocodiles have been known to actively track down the nesting turtles. This same species of crocodile is also known to consume nesting Olive ridley (Lepidochelys olivacea) at Playa Nancite in Costa Rica. Other nest predators include dingoes and foxes.
Although they lay relatively fewer eggs than other sea turtle species, relative to body size, the flatbacks lay the largest eggs of the sea turtles. An average egg for a flatback weighs 2.7 oz (77g) – which is about the same as that of the huge leatherback sea turtle! Due to the large egg size, flatback hatchlings are the largest of all sea turtle species.