The
flatback turtle (
Natator depressus) is a
sea turtleSea Turtles inhabit all the world's oceans except the Arctic.-Distribution:The superfamily Chelonioidea has a worldwide distribution; sea turtles can be found in all oceans except for the polar regions. Some species travel between oceans...
that is
endemicEndemism is the ecological state of being unique to a particular geographic location, such as a specific island, habitat type, nation, or other defined zone. To be endemic to a place or area means that it is found only in that part of the world and nowhere else. For example, many species of lemur...
to the
continental shelfThe continental shelf is the extended perimeter of each continent and associated coastal plain, and was part of the continent during the glacial periods, but is undersea during interglacial periods such as the current epoch by relatively shallow seas and gulfs. The continental rise is below the...
of
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
.
Flatback turtles are usually found in bays, shallow, grassy waters, coral reefs, estuaries and lagoons on the northern coast of Australia and off the coast of
Papua New GuineaPapua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
.
The Flatback turtle is known to be rather broad in its eating habits and can eat a variety such as seagrass, marine invertebrates (such as mollusks, jellyfish and shrimp) and fishes.
The
flatback turtle (
Natator depressus) is a
sea turtleSea Turtles inhabit all the world's oceans except the Arctic.-Distribution:The superfamily Chelonioidea has a worldwide distribution; sea turtles can be found in all oceans except for the polar regions. Some species travel between oceans...
that is
endemicEndemism is the ecological state of being unique to a particular geographic location, such as a specific island, habitat type, nation, or other defined zone. To be endemic to a place or area means that it is found only in that part of the world and nowhere else. For example, many species of lemur...
to the
continental shelfThe continental shelf is the extended perimeter of each continent and associated coastal plain, and was part of the continent during the glacial periods, but is undersea during interglacial periods such as the current epoch by relatively shallow seas and gulfs. The continental rise is below the...
of
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
.
Habitat
Flatback turtles are usually found in bays, shallow, grassy waters, coral reefs, estuaries and lagoons on the northern coast of Australia and off the coast of
Papua New GuineaPapua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
.
Tropic ecology
The Flatback turtle is known to be rather broad in its eating habits and can eat a variety such as seagrass, marine invertebrates (such as mollusks, jellyfish and shrimp) and fishes. It also is known to be a consumer of soft coral, sea cucumbers and other soft-bodied creatures.
Nesting
The Flatback turtle is unusual because it lays fewer, but larger eggs than the other
sea turtleSea Turtles inhabit all the world's oceans except the Arctic.-Distribution:The superfamily Chelonioidea has a worldwide distribution; sea turtles can be found in all oceans except for the polar regions. Some species travel between oceans...
species. Females emerge onto the beach on which they hatched more than 30 years ago and make their way up the beach to lay their eggs.
(Male turtles never return to the shore, as mating occurs at sea.) This takes around an hour and a half. The female digs a pit using her front
flippersA flipper is a typically flat limb evolved for movement through water. Various creatures have evolved flippers, for example most fish , as well as certain mammals , reptiles , and birds .Flippers sometimes occur in...
to clear away the topmost layer of dry sand,. She then uses her rear flippers to dig a small egg chamber. After laying between 50 and 75 eggs she covers them first with her hind flippers, and then flings sand back with her front flippers. Females will lay a clutch of eggs around every 16-17 days during the nesting season, with between one and four nests being laid in total. They will only nest every 2-3 years. There are around 54 eggs in each clutch, and the rookeries are usually small.
These eggs are vulnerable to predation by
dingoThe Dingo is a domestic dog which has reverted to a wild state for thousands of years and today lives largely independent from humans in the majority of its distribution....
es, sand
goannaGoanna is the name used to refer to any number of Australian monitor lizards of the genus Varanus, as well as to certain species from Southeast Asia.There are around 30 species of goanna, 25 of which are found in Australia...
s (
Varanus gouldii) and the introduced pest species - the
foxFox is a common name for many species of carnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail ....
. An altered ecology at known nesting sites, such as Port Hedland, has resulted in disturbances to the breeding behaviour of the turtle. Adult specimens are also found in the nets of fishing trawlers, and are still consumed by the indigenous peoples of its distribution range.
Hatching
Hatching is the most dangerous time for flatback. Guided by the low, open horizon, the newborns make a dash for the sea. Only safety in numbers will protect them from birds and crabs. However, even the sea is not safe. Sharks and fish patrol shallow waters, waiting to prey upon the hatchlings. Scientists estimate only 1 out of 100 turtles live to become an adult. However, as these turtles become adults there are very few organisms that predate them. The
survivorship curveA survivorship curve is a graph showing the number or proportion of individuals surviving at each age for a given species or group...
is known as a Type III because there is high mortality for these animals as hatchlings but there is a very low mortality rate as they become older..
Anatomy
The
carapaceA carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids as well as vertebrates such as chelonians, order Testudines, turtles and tortoises.-Crustaceans:In crustaceans, the carapace is a part of the exoskeleton...
of the adult is on average 90
cmA centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the current SI base unit of length. Centi is the SI prefix for a factor of...
long. This is low domed, the edge is upturned and has four pairs of costal scales–fewer than other marine turtles of the region. An olive-grey colour is found on the upper parts, and it is more pale ventrally. A single pair of scales are located at the front of the head, which also distinguish this species.
Distribution
Flatback turtles are found in coastal waters. The species may feed in the waters off
IndonesiaThe Republic of Indonesia is a country in Southeast Asia and Oceania. Indonesia comprises 17,508 islands. With an estimated population of around 237 million people, it is the world's fourth most populous country, with the world's largest population of Muslims.Indonesia is a republic, with an...
and Papua New Guinea, but it nests only in Australia. Nesting occurs across the top half of Australia, from
ExmouthExmouth is a town on the tip of the North West Cape in Western Australia. The town is located north of the state capital Perth and southwest of Darwin....
in Western Australia to
Mon ReposMon Repos may refer to:*Monrepos, a Rococo water pavilion in Ludwigsburg, Germany.*Mon Repos, a landscape garden in Vyborg, Russia.*Mon Repos Conservation Park, a turtle rookery near Bundaberg, Queensland, Australia....
in Queensland. The most significant breeding site is Crab Island in the western
Torres StraitThe Torres Strait is a body of water which lies between Australia and the Melanesian island of New Guinea. It is approximately wide at its narrowest extent. To the south is Cape York Peninsula, the northernmost continental extremity of the Australian state of Queensland...
. Breeding may also occur on the islands of the southern
Great Barrier ReefThe Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometres over an area of approximately...
, and on mainland
beachA beach is a geological landform along the shoreline of a body of water. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles, or cobblestones...
es and offshore islands north of
GladstoneGladstone is an Australian city located some 550 kilometres by road north of Brisbane and 100 kilometres south-east of Rockhampton. The city is situated between the Calliope River to the north and the Boyne River some 14 kilometres to the south. Between the two river mouths lies the deep water...
.
Naming and taxonomic history
This species is contained by a
monotypicIn biology, a monotypic taxon is a taxonomic group with only one type. The usage differs slightly between botany and zoology:In botany, a monotypic taxon is a taxon that has only one species: Ginkgo is a monotypic genus, while Ginkgoaceae is a monotypic family...
genus,
Natator, that is found in the Cheloniidae family.
depressus, the species indicator (the second part of the scientific name) means "flat" in Latin. This refers to the flatness of the Flatback's shell. The
Bardi peopleThe Bardi people are the Indigenous Australians from the area north of Broome and parts of the Dampier Peninsular in the Kimberley region of Western Australia.Djarindjin, Lombadina and One Arm Point are three Bardi communities in the area....
called this animal
barwanjan, and it was known to the Wunambil as
madumal.
Conservation
The species is considered vulnerable to extinction in
Western AustraliaWestern Australia is a state of Australia, occupying the entire western third of the Australian continent. Australia's largest state and the second largest subnational entity in the world, it has 2.2 million inhabitants , 85% of whom live in the south-west corner of the state.The state's capital...
, but the Red list of the IUCN notes that is data deficient and unable to be correctly assessed.
External links