Marine turtles in Western Australia

Six of the world’s seven species of turtles are found in WA waters:

• green
• hawksbill
• loggerhead
• flatback
• leatherback
• olive ridley.

All marine turtles in Australian waters are protected species at both State and Commonwealth levels.

• Marine turtles have existed in the world's oceans for more than 100 million years.
• These ancient mariners have cultural, spiritual and economic importance to coastal Indigenous Australians.
• Turtles feature in many stories, ceremonies, traditions and contemporary activities of Indigenous people, and are often a food source in remote coastal communities.

Marine turtles generally live for a long time and are slow to reach sexual maturity—it can take between 20 and 50 years for a turtle to begin to breed. The only time they leave the ocean is when the adult females lay their eggs on beaches, and occasionally to bask during the nesting season.

Nesting

• Male and female turtles return to the region where they were born to mate and nest, sometimes migrating thousands of kilometres between their nesting and feeding grounds—a mean feat when it may have been decades since they were last there!
• Females nest every two to eight years, and lay between one and 10 clutches of 30 to 180 eggs. The number of eggs laid and the number of times a turtle nests in each season varies between species and between different populations of the same species.
• When nesting, the female turtle slowly crawls up the beach, one to two hours on either side of the evening high tide.
  • She selects a nesting site based on the height above the high tide mark, sand composition and moisture content, then digs a pit using all four flippers.
  • She may abandon the site if she hits an obstacle or the sand is not moist enough.
  • After creating a body pit, she digs a vertical egg chamber with her hind flippers and lays the eggs, then covers them with sand, camouflages her nest and returns to the water.
• Nest temperature, in the early stages of embryo development, determines the sex of hatchlings. The temperature must be between 25-33°C for the embryos to grow. If the nest temperature is towards the cooler end of this range the hatchlings are all male, while warmer temperatures produce female hatchlings.

Links

• Recovery plan for marine turtles in Australia
• Ningaloo turtle program
• Seaturtle.org – International website on sea turtles
• Marine turtles in Australia  (Australian Department of Environment and Heritage)
• Indian Ocean Sea Turtle MoU
• Marine Parks WA (Parks and Wildlife's kid's site)
• Marine wildlife of WA's north-west identification guide2.78 MB
• Marine turtles of the Kimberley Coast2.91 MB