Green Turtle (Chelonia mydas)
|Click here to enlarge this illustration of a
generalised turtle breeding cycle.
What does it look like?
The green turtle’s smooth, high-domed shell is mottled olive green, brown and black, but the species actually gets its name from the colour of its fat. People know what green turtle fat looks like because the turtle was hunted in Australia for its eggs and meat – which was boiled into soup – until it was given legal protection in 1973.
Adults have a shell length of about 1 m and average about 130 kg, although some nesting females can weigh more than 180 kg. By comparison, their hatchlings are only 5 cm long and weigh 25 g! Hatchlings have a black carapace with white markings around the carapace, flippers and on the plastron (lower shell).
Where does it live?
The green turtle lives around coral and rocky reefs and seagrass meadows in tropical and subtropical seas. Given the enormous amount of seagrass in the Shark Bay World Heritage Area, it’s not surprising that the place is popular with turtles. They are usually spotted when out boating, but Eagle Bluff and Skipjack Point are great places to see them without getting wet. The turtles live here for decades, grazing on seagrass, seaweed and jellyfish before making their first migration back to their birthplace to breed. Like the loggerhead turtle and other species, they use a special ‘magnetic compass’ in their brain to find their home beach, which might be hundreds of kilometres away.
How does it breed?
In Western Australia, the green turtle breeds from the Ningaloo coast up to Barrow Island, the Montebello Islands, the Dampier Archipelago, Lacepede Islands and north of Broome. There have been green turtle tracks recorded in Shark Bay on Bernier and Dorre Islands, which is the southern extent of their breeding range. Breeding occurs about once every six years, nesting mostly from late October to February. Like other marine turtle species, the female mates with several males and stores the sperm for use later in the season. She lays about 115 eggs per clutch, and about five clutches per season. The eggs, which are shaped like ping-pong balls, hatch between December and May.
Any threats to its survival?
The green turtle is an endangered species
. Crabs, goannas, herons, gulls, foxes and fish such as sharks and trevally all make a meal of hatchlings. Tiger sharks also snap up juvenile and adult turtles. But the greatest threat facing green turtles is human disturbance to their feeding and nesting areas. Each year turtles drown in fishing gear and are strangled or choked by rubbish. Dredging (the removal of sediment from the sea floor to make a channel deep enough for larger boats) can damage the turtles’ seagrass beds. Coastal developments such as marinas and high-rise buildings can also disturb turtles’ nesting beaches. And in many countries, hunting has drastically reduced the turtle population. The green turtle is protected in Australian waters, and in Shark Bay, hunting is restricted to traditional use by Aboriginal people.
The green turtle likes to bask on the water’s surface, making it very vulnerable to being hit by boats. It might not see a boat coming, or be unable to swim fast enough to get out of the way. Please travel slowly in Shark Bay, especially over seagrass beds, and watch where you’re going. We must be aware of turtles and respect them in their habitat if they are to have any chance of survival.
How do you identify marine turtles?
to go to our Shark Bay
marine turtle identification guide!
For more information about Western Australian wildlife check out the WA Museum Fauna Base
to download a printable PDF of this fact sheet.