A tale of 2 leatherback sea turtles tagged off Nova Scotia
Good luck, persistence and international co-operation has delivered a rare trove of data from two endangered leatherback turtles tagged off Nova Scotia last summer.
The turtles, Ruby and Isabel, were carrying a tracking transmitter and a device that stored a huge cache of precise GPS locations accumulated during their 12,000-kilometre migration from Canada to Trinidad, off South America.
This month, when the nesting leatherbacks crawled ashore on separate beaches, researchers and volunteers on the island managed to intercept them, retrieve their tags and 10 months of stored data.
“We’re really excited,” says Mike James, lead scientist with the sea turtle unit at Fisheries and Oceans Canada.
“In the case of Isabel’s data, it downloaded yesterday and we had over 12,000 GPS positions that have been collected for that turtle since she was tagged last July.”
The data allows scientists to reconstruct the movements of the sea turtles throughout their migration, including where it’s needed most — in and around Trinidad, the nesting destination for most of the declining northwest Atlantic population that are in Canadian waters.
“We know that there are a lot of threats to the turtles in those areas and there are a lot of interactions with local artisanal fisheries, and there are a lot of places where there happens to be a lot of human impact on the turtles. But we just don’t have the data to understand that very well,” James said.
Recovering an archival tag, as it is known, is rare.
Sometimes the tags fall off during mating or are otherwise lost on the journey.
In the 20 years leatherbacks have been tagged in Atlantic Canada, archival tags have been recovered only four times: in Panama, French Guiana and twice in Colombia. The most recent case was seven years ago.
Within a single week in May, two were recovered in Trinidad.
“I have never recovered this much data from leatherbacks at one time,” James said.
It took 10 hours to process the data Isabel was carrying.
Ruby and Isabel were tagged two days apart in waters south of Halifax in July 2019.
Ruby is one of the biggest leatherbacks ever captured in Atlantic Canada. She is the size of a pool table and weighs a tonne. A flipper tag told scientists she had previously nested in Trinidad.
Isabel had no markings.
In the summer and fall, leatherbacks feed on jellyfish in Atlantic Canada before migrating south to breed.
Data shows Isabel travelled 12,252 km and Ruby 12,891 km after being tagged.
The recovery operation was run out of Mike James’s Halifax home, where he’s been working since the pandemic.
When it became clear where the turtles were headed, James got in touch with the Trinidad and Tobago Ministry of Lands, Agriculture and Fisheries, and conservation groups on the island.
Finding the tagged turtles was not a sure thing.
Female leatherbacks nest on 10-day cycles, spending 90 minutes laying eggs on shore at night before heading back to sea and returning again several more times to nest.
“Generally they return to the same stretch of coastline and if you’re lucky to the same beach on that stretch of coastline. And in both cases, both these animals did that,” James said.
“We found out when and where they laid their initial nest. They were successfully intercepted … and their instruments were removed and new instruments were deployed on the turtles which is the next chapter.”
James gives credit to teams in Trinidad that spent nights waiting for the turtles.
One of the researchers was Kyle Mitchell, of Nature Seekers, a conservation group that pays for itself by conducting ecotourism.
He was in Nova Scotia on an exchange last summer and on board to help tag Ruby.
Ten months later, he was on hand when Isabel first came ashore at Matura Beach.
Unfortunately, there was not enough time to remove the tag, so he watched her crawl back into the ocean in the hopes of getting a second chance.
“We were a bit skeptical that we might find her back again because usually, to get that much luck twice in a row, is not something that happens that often,” Mitchell said. “I was very fortunate to be a part of both sides. It was definitely overwhelming. Overwhelming and tiring, but definitely worth it.”
The Las Cuevas Turtle Group and Nature Seekers recovered Ruby on the north coast.
With new satellite transmitters attached, scientists will be able to track the complete year-long migration loop when Isabel and Ruby return to Nova Scotia sometime in August.
But that too was a close call.
Normally, Canadian scientists with tracking tags would be in Trinidad for the nesting period.
But this year, COVID-19 kept them, and their equipment, in Nova Scotia. When Ruby and Isabel showed up, tags were rushed by courier from Nova Scotia and from colleagues in Florida.
They arrived in the nick of time.
“Both packages were received the week that they were needed. The one tag [from Florida] arrived the day that it was needed for the deployment on Isabel. So it was that tight,” James said.
“Our box arrived a day or two later, but we had about 48 hours of comfort zone in the end before that second instrument was needed for Ruby.
“But it was an Amazing Race-situation, tracking information on the various courier providers websites.”
With Fisheries and Oceans Canada shut down by the pandemic, it’s not clear whether leatherback tagging will happen in Nova Scotia this summer.
The program starts in July and no decision has been made.
Ruby was named after the mother of noted Acadia University scientist, Sherman Bleakney, an academic who first proposed that leatherbacks were regular visitors to Atlantic Canada back in the 1960s.
Bleakney died last October.
Isabel was named by children attending an annual sea turtle summer camp in Halifax.
www.cbc.ca 2020-05-25 09:00:00