Tracking the Titans: Research on Endangered Leatherback Turtles Informs a Recovery Strategy
In the wee hours of the morning on March 22, 2014, there is no sleep for Fisheries and Oceans Canada sea turtle biologist Dr. Mike James. Instead, he monitors his laptop screen for updates on the location of a Leatherback Turtle as it nears the coast of the Caribbean island of Trinidad. Seven months earlier, in August 2013, Dr. James and his team captured the same turtle feeding off the coast of Cape Breton Island, Nova Scotia, and equipped it with a satellite tag to track its movements in Canadian waters and its subsequent journey to the tropics.
Satellite-linked tags gather data on the horizontal movements and dive behaviour (depth) of Leatherbacks, as well as the water temperatures they encounter, providing scientists with information about how they use the water column and what habitats they select for feeding. To date, about 100 satellite tags have been deployed on these turtles in Canadian waters.
An endangered survivor
The ancestors of Leatherbacks have roamed Earth for more than 100 million years. Propelled by immense front flippers, these gigantic yet graceful titans can swim up to nine kilometres-an-hour, migrate up to 18,000 kilometres a year, and dive to more than 1,300 metres—farther and deeper than any other reptile. The findings of satellite telemetry studies and other research led by Dr. James are providing new insights into the world's largest reptile, which is listed as endangered in Canada (under the Species at Risk Act) and the United States.
"One reason Leatherbacks are endangered is they're prone to becoming tangled in vertical lines and other fishing gear throughout their range. They often drown before fishers or other help arrives to release them," says Dr. James.
Added to these risks are the extremely low odds of hatchings surviving to reach adulthood at 15 years of age or older. And despite laws protecting sea turtles around the world, in many countries they are still in danger of having their eggs harvested or being slaughtered for meat. Fortunately, efforts are underway to end illegal poaching.
The research findings inform the Recovery Strategy for the Leatherback Turtle (Dermochelys coriacea) in Atlantic Canada, which identifies the steps necessary to stop or reverse the decline of this species by mitigating human impacts.
"The overall goal of our research is to gather information that will further the recovery planning process, including improving our knowledge of sea turtle biology and where critical habitat for Leatherback and Loggerhead turtles is in Canadian waters," says Dr. James. Key to the research is a focus on collaboration with the fishing industry, other scientists, and non-governmental organizations, both in foraging areas, like Canada, and in countries where sea turtles nest.
For several days leading up to March 22, data received from the satellite tag showed the female turtle hovering off the north coast of Trinidad before moving close to shore near Grande Riviere Beach, an important Leatherback nesting area. Eventually, Dr. James alerted members of community organizations who patrol the nesting beaches in hopes they could find her and recover the tag when she came ashore to nest. Tags can only be retrieved from mature females since males and sub-adults don't go ashore.
"Data transmitted from turtles equipped with satellite tags provides us with summaries of what they're doing. However, actually recovering a tag gives us access to the detailed, second-by-second behavioural record of the turtle, which is stored in the tag's internal memory. From a science perspective, that's the data goldmine," says Dr. James. The tag recovered in March 2014 provided novel information about the behavior of female turtles in the months, weeks and hours before nesting.
"There's been a lot of speculation about when and where mating occurs, how close females will remain to a nesting colony that's their eventual destination, and what cues they use to orient to their specific beach," he says. "The tag showed us this turtle didn't go directly to her nesting beach, but instead travelled to the coast of Venezuela first, possibly because her eggs were not completely developed or she hadn't honed in on her nesting beach yet."
Leatherbacks in Canadian waters
Until the late 1990s, the importance of Canadian waters to Leatherbacks was not recognized, and they were still considered by many to be mainly a tropical species. In 1997, as part of his graduate studies research, Dr. James began distributing posters with the question "Have You Seen This Turtle?" to over 300 fishing wharves in Nova Scotia. In 1998 alone, 200 sightings were reported. Since then, an at-sea research program led by Dr. James has revealed that Eastern Canada provides critical foraging habitat for the species. Though Leatherbacks also exist on the West Coast, their numbers there are much lower.
Eastern Canada, it turns out, represents one of the most important foraging habitats for the Atlantic Leatherback population. They roam these waters from May to as late as mid-November, gorging on as much as their entire body weight of jellyfish, or more, in a single day. Leatherbacks captured here have ranged from 170 to 700 kilograms, with an average weight of about 350 kilograms.
Where do they go when they're not here? Findings from other elements of Dr. James' research—including the recapture of individuals marked with external flipper tags and/or internal microchips—have been used to 'ground-truth' genetics studies of the nesting origins of Leatherbacks in Canadian waters.
"We've discovered that more than 50 percent of Leatherbacks in the Canada's Atlantic waters come from the island of Trinidad, and that all western Atlantic nesting stocks are represented in our population, in proportions reflecting the relative sizes of those stocks," says Dr. James.
Identifying critical habitat
Satellite telemetry data from about 80 turtles has enabled Dr. James and his team to identify critical habitat for Leatherbacks in Canadian waters—an essential component of a Species at Risk Act action plan under development, which will outline the projects or activities necessary to meet recovery strategy goals.
"The key areas where Leatherbacks gather every year include from the southern Gulf of St. Lawrence through to Sydney Bight, off Cape Breton Island; the Northeast Channel near the boundary between Canadian and U.S. territorial waters, and the south coast of Newfoundland near Placentia Bay," says Dr. James. "Based on our research results, these areas have been proposed as critical habitat under the Species at Risk Act."
Other recent findings include insights into the foraging behaviour of Leatherbacks in Canadian waters. From 2008 to 2013, Dr. James mounted video cameras equipped with GPS, temperature and depth sensors on the shells of 30 free-swimming Leatherbacks to record their behaviour over two to four hours.
"Until we started using these camera tags, we were largely only speculating about the feeding habits of these turtles," says Dr. James. "Retrieving the first video data was by far one of the most exciting moments for me because it revealed turtle behaviour at a finer scale than is possible with satellite telemetry, and we could see Leatherbacks searching for, capturing, and handling their prey, all from their perspective."
The video cameras revealed that, at least in Canadian waters, Leatherbacks are entirely visual predators, feeding only during daylight hours, and mainly in the top 30 metres of the water column.
"Even though jellyfish are about 95 percent water, these turtles consume so many that when they leave Canadian waters to migrate south, they are 33 percent heavier than when they first arrived. So there is tremendous energetic value in the foraging habitat here," says Dr. James. "Atlantic Canadian waters have emerged as incredibly important habitat for this endangered species. Long-term protection and monitoring of the population here represents a key contribution to international recovery efforts. Collaborative research and conservation work in Canada, and with individuals and organizations in other areas of the Leatherback's range, will help safeguard the future of this species in the Northwest Atlantic."
For more information:
- Aquatic Species at Risk - Leatherback Sea Turtle (Atlantic population)
- Aquatic Species at Risk - Leatherback Sea Turtle (Canadian Pacific population)
- Sea Turtles — Frequently Asked Questions
- Leatherback Sea Turtle: Tips for Handling and Releasing (in the Gulf Region)
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