When you’re one of the world’s largest reptiles, you can invent your own rules. The leatherback, which can weigh up to 900 kilograms, is the only sea turtle to have a leathery skin on its back instead of a hard shell. It is the only one without claws on its flippers. The leatherback does not have the ability to retract its limbs and head. Because of biological adaptations such as a dark colour and a thick layer of fat, it can survive in far colder water than other marine turtles. This means it can travel farther than any reptile on Earth — sometimes crossing entire oceans by moving its front flippers like wings.
These unique characteristics, combined with the leatherback’s staunch elusiveness, make it a tantalizing subject for wildlife research. Biologists know that leatherbacks feed primarily on jellyfish and that ocean pollution, especially plastic shopping bags, can become lethally tangled in their digestive systems.
Researchers also know that leatherbacks lay their eggs on hot southern beaches and that a single baby turtle faces poachers, natural predators and disorientation on its long trek to water. Amidst these dangers, the leatherback’s worldwide population has declined by more than 60 per cent in the last 30 years, which has accelerated the need to learn more about them and how to prevent their extinction.
Much about the leatherback remains a mystery, though. Although each turtle develops a pink patch on its head as unique as a human fingerprint, scientists have difficulty tracking them throughout their worldwide travels. Because they only swim forwards, they cannot be studied in captivity; a captive leatherback will collide with the walls of its tank until it seriously wounds itself.
These turtles are meant for the open ocean. They deserve respectful, discrete observation. Here at the Canadian Wildlife Federation, we plan to protect them from the many dangers threatening their survival.
Hatching and Nesting
The leatherback sea turtle population faces extreme challenges as an endangered species in Canada, but did you know that many of those challenges can occur before the hatchlings even reach the water’s edge? Only if a mother sea turtle has laid her eggs clear of predators on land, if the hatchling can navigate and survive its journey to sea and if the young sea turtle can adapt to the harsh realities of ocean life does it have a chance of survival.
Like other sea turtles, leatherbacks are known to display remarkable loyalty to the nesting beach where they were born. Upon reaching maturity, leatherbacks will usually return to lay their eggs in the same area where they were born a few decades before. Getting to the beach can require unfathomable navigation skills; once the leatherback reaches the beach, it faces a host of natural processes and human activities during its nesting process.
Leatherbacks usually prefer to nest on open beaches, near deep water. Flooding and erosion hazards in these areas can create a loss of nests. The collection of eggs for sale at local markets is a widespread problem for this species on nesting grounds, especially since the turtles will continue to return to these same beaches time after time. That, combined with increasing beach development, the creation of retaining walls, mechanical raking of beaches and off-road vehicles are all factors that have completely affected the leatherback sea turtle species.
Upon nesting, female leatherbacks use their hind flippers to dig and create a nest in which they lay anywhere between 50 and 166 eggs. They will lay their eggs at eight- to 12-day intervals, producing an average of six clutches per season. It is during a roughly 65-day incubation and emergence period that predation is highest for the sea turtle eggs. They may face domestic dogs, vultures, skunks, sea gulls, raccoons, lizards, opossums, jaguars and even ants, which have all been recorded preying upon nests and hatchlings. And if the turtles can beat those odds, artificial lighting in the vicinity of the beaches can lead to disorientation for both adults and hatchlings. For the adults, this contributes to failed nesting attempts, yet another reason this species is in so much trouble.
Feeding
The leatherback sea turtle is likely the fastest-growing reptile in the world. Starting their lives as 40- to 50-gram hatchlings, leatherbacks grow 10,000 times this size over the course of their lives. How? By chowing down — a lot. In order to grow to epic proportions, hatchlings eat their body mass in food every day — as adults, they eat 50 per cent of their body mass per day. However, leatherbacks lack the strong jaws and teeth they’d need to eat hard-bodied prey, like crustaceans. As a result, their diet is restricted to soft-bodied, often gelatinous prey like jellyfish, which they grab with two cusps on their upper and lower jaw that help prevent the jellyfish from escaping. Their throats are lined with sharp spines that latch on and shred the jellyfish into pieces as they swallow.
The Canadian Sea Turtle Network found that Atlantic Canadian waters are crucial to leatherbacks. Every July and August, turtles arrive from the U.S.A., Costa Rica, Panama, Colombia, Puerto Rico, Anguilla, Venezuela, Grenada, Trinidad, Guyana, Suriname and French Guiana to forage in Canadian waters. They can usually be found just off the coast of Nova Scotia, Newfoundland and the northern Gulf of St. Lawrence, and they have been spotted in the Bay of Fundy as well. So why are leatherbacks lured to Canada? Location, location, location. The Scotian Shelf is closer to major nesting areas in the western Atlantic, making the turtles’ journey easier, and leatherbacks heading northward along the U.S. coast are channelled onto the Scotian Shelf. Moreover, the Atlantic coast has high zooplankton and gelatinous populations, making Atlantic Canada the ideal locale for foraging.
Approximately 6.4 million tonnes of marine debris is dumped into our oceans every year, and between 60 and 80 per cent of it is made up of plastics. Moreover, 60 per cent of the trash strewn on the beach and 90 per cent of debris floating in oceans is plastic. To leatherback sea turtles, many of these bits look like jellyfish, which the turtles gobble down. While the turtles may be able to digest smaller plastic pieces, the larger pieces can plug up the digestive passage and cause internal injury and infection.
In the last 40 years, over a third of the leatherback sea turtles examined had ingested plastic. Where does all the plastic come from? You might be surprised to hear that approximately 80 per cent is from land — landfills, industrial facilities, sewage and storm runoff. The remaining 20 per cent is due to merchant and passenger ships; offshore oil and gas platforms; recreational, commercial and military craft; and fish-farming operations.
Migration
Leatherback sea turtles migrate farther than any other reptile on Earth. En route to nesting and feeding grounds, they can travel across entire ocean basins, including the Atlantic, Pacific and Indian Oceans. Atlantic leatherbacks head from the southern nesting grounds of French Guiana, Suriname, Grenada, the U.S. and Trinidad to foraging grounds off the east coast of Canada. Eastern Pacific leatherbacks nest on the beaches of Costa Rica and Mexico and head southward to Galapagos, Peru and Chile, whereas western Pacific leatherbacks make more varied treks — south into the South Pacific, east into coastal waters off North America, north into waters off Japan and west into waters off the Philippines and Malaysia.
For years, researchers believed female leatherbacks made the long trek from nesting to foraging sites solitarily. However, the Canadian Sea Turtle Network recently found that males and females make the journey together, which means all leatherbacks face the same hazards in the wild. So how do they travel such vast expanses? Scientists are still perplexed by how this feat is made. Like any object in the sea, leatherbacks are subject to sea currents, which can force them off course. However, the very fact that they do eventually make it to their target destinations year after year suggests that leatherbacks navigate, in one way or another, in spite of the current drift they may experience along the way. Researchers believe that when the leatherbacks are faced with sweeping currents, they may take into account the displacement they experience from the drift and then get back on track with their long and powerful flippers, which can propel them more than 95 kilometres a day. Or they might fix their position towards their destination, wait for the drift to subside and then work overtime, swimming at up to 9.3 kilometres per hour.
Currents aren’t the only obstacles the leatherback faces in the ocean. Coming into contact with fishing gear remains the primary threat to these reptiles. While leatherbacks can swim under water for over 80 minutes before they need to surface to breathe, if they get tangled in plastic straps, ropes, lines and nets they can incur serious injuries trying to break free or even drown. When fishing nets called ghost nets are lost at sea or thrown overboard, they can travel the waters for up to 600 years and expand up to 15 metres in depth and 90 kilometres in length, gathering marine wildlife in their midst. Leatherbacks also get caught in fishing gear by swimming too close to fishing lines and attempting to eat the bait. Between 3.8 and 5 million baited hooks are set every day in the world’s oceans, and researchers estimate that more than 50,000 leatherbacks were likely taken as pelagic longline bycatch in 2000 alone.
What CWF is Doing
The leatherback sea turtle is listed as endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and critically endangered across the globe by the International Union for the Conservation of Nature (IUCN).
In 2010, CWF’s Endangered Species Program provided funding to the Canadian Sea Turtle Network for two leatherback turtle projects. The first project monitors the leatherback turtle population in Atlantic Canadian waters and examine the behaviour of leatherbacks feeding close to the shores of Nova Scotia.
The second project looks at the risk that commercial fishing gear poses to leatherback turtles in Nova Scotia waters. The Atlantic waters off of Nova Scotia have been identified as a critical habitat for leatherbacks, and entanglement in fishing gear is a major cause of death in leatherbacks at sea. CSTN has been working with the commercial fishing industry to reduce the risks of entanglement. The project is helping identify when leatherbacks and specific types of fishing gear are likely to interact. This information will be used to establish better practices and conservation efforts to minimize future entanglements.
CWF’s Endangered Species Program has also provided funding to Dalhousie University for research on identifying and understanding human threats to leatherback turtles in Atlantic waters. The researchers will also study the life history of leatherback turtles and identify their critical habitats. This information will be used to minimize the risks to leatherback turtles.
How You Can Help
The leatherback sea turtle is just one of many aquatic species under assault from a growing number of threats to our water. Fortunately, there are many things that each of us can do to make a difference to the future of our aquatic wildlife and the waters they call home:
- Donate to CWF’s $1-million Endangered Species Program, which supports research that will benefit the conservation of species at risk, with particular focus on aquatic species.
- Reduce the risk of entanglement in fishing gear and garbage, and protect the leatherback’s habitat by helping turn the tide on pollution with simple, everyday activities. .
