10 Feb 2019
HOW MUCH DO YOU KNOW ABOUT SEA TURTLES?
Australian waters are home to six of the seven species of sea turtle in the world. They’ve been swimming in our seas since the time of the dinosaurs, but now human interference is having a deadly impact.
How much do you know about these ancient mariners and the threats they face?
The mighty sea turtle
Green sea turtles are one of the world’s largest species of turtle, weighing up to 200 kilograms and measuring up to 1.5 metres long. Hawksbill turtles are slightly smaller, weighing up to 80 kilograms and 1 metre long.
What’s in a name
The green sea turtle gets its name not from the colour of its shell, but from the green fat deposits around its internal organs. Scientists believe this green coloured fat is the result of their favourite foods - seaweed and seagrass. Hawksbills are named for their bird-like beak, which is used to pry food from small crevices in coral reefs.
They love to travel
All sea turtles are prolific travellers. They can be found nesting along the coastline of more than 80 countries around the world, with the largest nesting populations found in Costa Rica and Australia. Female green turtles have been known to travel more than 2,600 kilometres in their migrations between feeding grounds and nesting beaches. Hawksbills are also known to make long journeys. WWF-Australia has used satellite trackers to help map the migration patterns and feeding areas of hawksbill turtles. We’ve found they migrate from nesting beaches in northeast Queensland and Papua New Guinea to the Torres Strait and waters surrounding Cape York. This helps us understand where they may need further protection.
But they have a soft spot for home
Depending on the species, sea turtles reach sexual maturity between 20-40 years. When they are ready to nest, adult female turtles return to the beaches where they hatched decades ago to lay their eggs. This journey is made every two to four years. Here, they dig nests roughly 55-65 cm deep and lay a ‘clutch’ of eggs.
The temperature of the sand during incubation dictates a turtle’s gender
Although different for each sea turtle, temperatures below 29 degrees Celsius predominantly produce male species whereas temperatures above this generally produce female turtles. Temperatures above 34 degrees Celsius are fatal. Because of rising temperatures we are trialling methods to cool the sand of turtle nests on Milman Island, off the coast of Far North Queensland, to help protect future populations.
Rising temperatures due to climate changes, means they are under threat
Increased temperatures means in some rookeries in the northern Great Barrier Reef virtually only female green turtles are being born. This is known as feminisation. Without males the future of the species and their ability to reproduce is threatened.
Sea turtle numbers are on the decline
The majestic sea turtle may have been present in the oceans for more than 100 million years but their numbers in many places are declining. In fact, five of the six species of sea turtle found in Australia are now listed as endangered or vulnerable. Although they are faced with threats of feminisation, illegal trade, poaching, fishery bycatch and loss of habitat, together we can help save the sea turtle. Learn more about what we are doing to combat poaching and feminisation.
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