Swimming with the Leatherback Turtle
With what is likely to be one of the most terrifying mouths in nature, the Leatherback Turtle is unfortunately in decline across the world. Once prevalent in oceans across the world (apart from the Arctic and Antarctic), many of these turtles fall victim to human activity as well as natural prey.
Often known as the Lute Turtle or Leathery Turtle, the Leatherback turtle is the largest of all living turtles and is only beaten by three crocodile species when comparing reptiles by weight. Leatherback turtles are easily distinguished from other sea turtle species– the carapace is covered by skin and oily flesh rather than a bony like substance and ridges along the carapace allow these turtles to dive to depths of over 1,200 metres, staying down for up to 85 minutes.
Eating to Grow
Starting out between 15 – 30gms and at just 5 – 7 centimetres long on average at birth, Leatherback turtles end up being the largest sea turtle species across the world. Fully grown, they can reach lengths of two metres and can weigh up to 900kg. In comparison, the smallest sea turtle is the Olive Ridley or Pacific Ridley which only reaches one metre in length and averages out at 45kg in weight once fully grown.
With large food requirements, the leatherback turtle is always on the search for food. The oesophagus is lined with papillae, sharp, keratinized prongs that allow this species to mainly eat jellyfish and other soft-bodied animals. These prongs, made from cartilage, line the throat allowing the turtle to grip onto the jellyfish. Without these prongs, as the turtle expels excess water, the jellyfish would slip straight back out. The papillae also help to protect from jellyfish stings while eating.
What begs the question however, is just how such a large animal survives on a jellyfish diet, which is essentially water, and a small amount of protein and fat.
The Leatherback turtle has quite a long oesophagus leading from the mouth through to the back of the body, and then looping up again until it reaches the stomach. Essentially, it acts as a storage unit, and as food is digested and released, more food enters the stomach; it’s like a never-ending procession of food through the body.
Where will you travel?
Leatherback turtles can be found in almost all oceans in the world and while they feed in temperate waters, their breeding is done in tropical areas. They are oceanic and it is rare to find one close to shore, particularly here in Australia, unless they are one of the few laying eggs in the Great Barrier Reef region.
It is thought that Leatherback turtles take one of the longest migration routes between breeding areas and feeding areas, with an average of 6,000km each way – that’s just under a return trip between Brisbane and Perth.
Despite feeding in temperate regions and breeding in tropical regions, they have been found in waters with temperatures as low as 4 degrees Celsius (approx. 40 degrees Fahrenheit) and are the only reptile known to remain active at these low water temperatures.
Life as a Leatherback turtle
There are four main subpopulations of the Leatherback turtle found across the world – the Atlantic subpopulation, the Pacific subpopulation, the South China Sea subpopulation and the Indian Ocean subpopulation.
Atlantic Leatherback turtles are found in waters from the North Sea to the Cape of Good Hope, feeding in areas near Quebec and Newfoundland, and nesting in the regions of Trinidad and Tobago, Gabon and Antigua. The coastline of the Mayumba National Park is home to one of the largest nesting populations with almost 30,000 turtles visiting every year. Small nesting areas are also located on the east coast of Florida, and in Costa Rica.
Pacific Leatherback turtles have two distinct populations, the first nesting on beaches around Indonesia and the Solomon Islands, and feeding in regions such as California, Oregon and Washington to feed. The other finds food in the regions around South America and nest in Mexico, El Salvador and Nicaragua.
Unfortunately, the Leatherback turtles in the South China Sea region, namely Malaysia, have all but disappeared. In years past there could be up to 10,000 nests in Terengganu, however egg consumption by humans have added to the decline. So far, conservation efforts have failed.
The last sub-population is those living in the Indian Ocean. There is little known about the turtles living in this region, however it is thought that nesting areas are around Sri Lanka and the Nicobar Islands.
The Struggle to Survive
It is estimated that only one in a thousand hatchlings survive to adulthood and like many other creatures, one of the largest threats to the Leatherback turtle is human activity, and this happens from birth through to old age.
In some areas of the world, turtle eggs are taken from nests to be used as food or aphrodisiacs. They also fall victim to fishing nets and lines, boats and plastic, which is often mistaken for jellyfish. Some Leatherback turtles have been found with almost 5kgs of plastic in their stomachs.
Other predators strike while the iron is hot so to speak, and many hatchlings don’t make it to the water. Fish, dogs, seabirds, crabs, saltwater crocodiles, lizards, dingos and foxes all prey on eggs and hatchlings, while for adult turtles, the main predators are sharks, killer whales and crocodiles.
According to the World Wildlife Fund, the population of Pacific Leatherback turtle has declined the most over the last 20 years, with as few as 2,300 adult females thought to remain in the wild; this means the Pacific Leatherback turtle is the more endangered marine turtle population. It is also thought that the Atlantic population, while currently more stable, will start to decline as fishing increases.
Where you can see them
You’ll find Leatherback turtles in coastal countries across the world. Found in all tropical and subtropical oceans, at times they also extend into the Arctic Circle. From Alaska and Norway through to the southern tip of New Zealand, you may be lucky enough to spot a Leatherback turtle.
There are turtle rookeries along both the Queensland coastline where you may get the rare opportunity to see Leatherback turtles lay eggs and hatch. They have been known to occasionally feed and nest within the Great Barrier Reef Marine Park, and have sporadic nesting points throughout Queensland.
With the Leatherback turtle in decline across the world, developing safe rookeries is essential as is ensuring that items such as plastics are kept out of the water. While natural predators will always be around, there are plenty of steps we can take to ensure the future of these turtles.