Turtles have been in our oceans for over 120 million years, from before dinosaurs were walking the earth. There are 7 species of marine turtle, and we find 6 of those 7 on the Great Barrier Reef (GBR). The most common being the green turtle, so called because of the green colouring of the turtle’s fat beneath its shell, caused by seagrass and algae in their diet. Green turtles can grow over 1.1m, weigh over 90kg and can live for over 80 years. They feed on seagrass and algae but are omnivorous and can also eat jellyfish and sponges.
You find green turtles in seagrass rich areas and on coral reefs, however, where they go in the first few years of their lives is a mystery to science. Green turtles are endangered and their population numbers are decreasing throughout their full subtropical and tropical range. However, we are very lucky on the GBR; it’s a haven for turtles and harbours important feeding and nesting sites. In fact, one island on the GBR – Raine Island – is home to the largest green turtle rookery in the world.
Turtles spend most of their time in the water, however the females must come back to land to lay eggs. Often, the beach will be their natal beach and individuals have been known to travel thousands of kilometres to get there from their feeding grounds. The mature females haul themselves up the beach at night and use their hind flippers to dig a hole and lay their clutch.
The females will come back and forth from the water to the beach over a few weeks and lay about 1000 eggs in total. The eggs take a couple of months to develop and once ready, the hatchlings wait until nightfall then come spilling out and run the gauntlet down the beach into the water.
These turtle hatchings face many risks; as eggs they could drown in the nest, or be harvested by people or predated on by feral animals. As juveniles they are heavily predated on by seabirds, sharks and even crocodiles, then they face the mystery years from where most don’t return. As adults they’re under threat from various natural and human induced threats, most noticeably by harvesting of their shells and meat, coastal development, pollution, climate change and marine debris.
Green turtles mature very late, at about 30-40 years in the Indo Pacific, so they’re very sensitive to changes in their environment. As with many endangered species, turtles have typical traits that make them prone to overexploitation; they’re long-lived and late to mature with a long juvenile stage. Therefore, populations could take a long time to recover from recent declines.
We adore turtles on Wavelength and see them frequently at our exclusive site ‘Turtle Bay’ on Tongue Reef. However, all 7 species of marine turtle are endangered and will be close to extinction unless we continue to make changes to help protect them.
Turtles are reptiles and breathe air so they come up to the surface to take a breath of air from time to time. If we are very quiet and relaxed when snorkelling with them, we can often see them come to the surface to breathe; a magical experience. Check out our videos to see some of the really special turtle encounters we’ve had on Wavelength.