Green Pages

Teenage Turtle Tales

Using satellite telemetry to study the lives of sea turtles.

Story & Photos By Dr. Peter Richardson and Amdeep Sanghera, Marine Conservation Society

Earlier this year, we finally published the results of 18 years of sea turtle research carried out with our partners at the Turks & Caicos Islands Government’s Department of Environment & Coastal Resources (DECR), the University of Exeter and a host of other partners. There’s something very satisfying about publishing a scientific paper about satellite tracking sea turtles. The concise text, sharp figures and maps, extended bibliography and acknowledgements create another neat little piece to be fitted into the enormous jigsaw puzzle that makes up our knowledge of these fascinating marine reptiles. But the paper, rather efficiently entitled “Spatial Ecology of Sub-Adult Green Turtles in Coastal Waters of the Turks and Caicos Islands: Implications for Conservation Management,” only tells half the story.

Young green turtles feed on seagrass beds and tidal creeks within TCI’s RAMASAR site.

Attaching a tag to a turtle in the Turks & Caicos Islands and then tracking it is no simple task—it takes a lot of effort, time, patience, people, learning, money, project partners’ support and skill, as well as a heap of anxious hope when you finally release the turtle back where it came from with thousands of dollars worth of tech on its shell. Occasionally, when the tag malfunctions soon after release, and you receive no data from the orbiting satellites—all of that effort, time, money and worry amounts to nothing—­­­that is a gut wrenching feeling, we can tell you. But it is far outweighed by the majority of successful tags that have provided incredible insights into the submarine behaviours of these ancient animals that have outlasted the dinosaurs. Through live-tracking turtles you can literally experience scientific discovery as it happens—and that feels magical! 

At the Marine Conservation Society (MCS) we have been using satellite telemetry to study the lives of sea turtles with our partners at the University of Exeter since 2005, when together we attached a tag to Malliouhana, the huge leatherback turtle after she nested in Anguilla, and who went on to migrate to Canada’s waters and back. Since then we tracked adult female green turtles from their nesting beach in Sri Lanka, and more recently we have tracked green and hawksbill turtles in the Turks & Caicos Islands as part of the TCI Turtle Project. This last paper focused on the tracking of 16 sub-adult (or teenage) green turtles captured while foraging in the North, Middle and East Caicos Nature Reserve. The area is an internationally recognised RAMSAR site, protected for its complex and productive mosaic of wetlands, tidal creeks and seagrass meadows and the fantastic wildlife that they support, including an abundance of green turtles.

This satellite tracking research, combined with our ongoing flipper-tagging programme, has highlighted how important this protected area is to regional green turtle populations. Young green turtles spend several years feeding and growing fat on the seagrass beds and tidal creeks within the RAMSAR site. One flipper-tagged turtle spent at least five years there, from when we first caught, measured, tagged and released it, to when we eventually recaptured it, measured it and released it again. No doubt they stay there for much longer than that, between their arrival from the open ocean as dinner-plate sized youngsters, until their eventual departure as large, bulky teenagers. 

Twelve of the sixteen satellite tagged teenage turtles spent the entire time they were tracked within the site, most not straying too far from where we captured them, while three others spent at least 9 months there before eventually migrating away. The other turtle headed off 13 days after it was tagged and released, so we were lucky to catch it before it departed! The productive habitats within the RAMSAR marine protected area clearly provide crucial foraging grounds for these growing turtles. From our previous genetic research we know that these turtles mostly originate from nesting beaches used by the larger nesting populations in Costa Rica, Florida and Mexico, so the RAMSAR site, managed and protected by the TCI Government, is regionally important for the conservation of Caribbean green turtles.

So four of our sixteen tracked teenage turtles migrated away from the Turks & Caicos Islands, and when this happens our inner turtle-nerdery comes to the fore. We check the data maps relayed by satellite on a daily basis, get excited when they arrive at the shores of another country, and then worry about them all the while they are there . . . “Will they get caught in a fisherman’s net today?”

Fishermen from South Caicos work with Dr. Peter Richardson to tag and release a turtle for tracking.

At least one of us was present at every tracked turtle’s capture, tagging and release, working closely with our turtle fishermen friends Gilbert Jennings and Dave Clare from South Caicos. Gilbert and Dave are experts at what they do, having fished TCI waters for decades, and have taught us both an awful lot, including how to catch turtles. From capture to release, the turtles are treated with greatest care and respect, and in the short time the turtles grace us with their company, we almost feel like we get to know them—we even give them names.

Take Karman for example, named after Amdeep’s niece. Karman was one of the bigger turtles—captured by Amdeep, Gilbert and Dave on Boxing Day 2012. For more than nine months after release, Karman stayed well within the RAMSAR site, munching on seagrass and getting fat, then one day she decided to go. We have absolutely no idea how she decided it was time to move on, but once the decision had been made there was no turning back. Karman swam south, arrived at the shores of the Dominican Republic, and headed west along the shores of Haiti. Our hearts were in our mouths, for we knew that delicious green turtle meat is a favourite in those countries. But she safely passed through the Windward Passage between Haiti and neighbouring Cuba and then headed due south again, crossing the Caribbean Sea and arriving at the shores of Colombia near Cartagena. From there she headed west for about 600 miles along the coasts of Panama and Costa Rica before doing an abrupt about-turn and heading back to a foraging ground in Colombia’s inshore waters, where she stayed for five months before her tag ceased transmissions. 

We believe we recorded Karman’s “developmental migration,” a theoretical journey rarely recorded, that green sea turtles take between their juvenile foraging grounds and the adult foraging grounds where they will likely spend the rest of their lives in between their breeding migrations. Why did she travel the extra 1,200 mile swim to Costa Rica and back? We don’t know. We do know that many of the juvenile green turtles in TCI waters originate from Costa Rica’s beaches, and we know that green turtles eventually return to breed on a beach close to where they themselves hatched decades earlier. We think that the developmental migration places the turtle on an adult feeding ground much closer to the breeding grounds to reduce the distance the turtles must migrate for the rest of their adult lives when they breed. Maybe Karman was just checking out the route to her breeding grounds for when she has to make that journey in a few years’ time?

This map shows the migrations of four tagged green turtles in TCI.

This thinking is backed up by the return of TCI turtle flipper tags we have received from elsewhere—five turtles originally flipper-tagged by us on the Caicos Bank have been caught by fishermen on the vast seagrass meadows of Nicaragua, some 900 miles away from TCI as the crow flies. We know from other tracking projects that, just as the RAMSAR site provides important juvenile foraging habitat for the Costa Rican nesting populations, Nicaragua’s seagrass meadows provide key adult foraging habitat for them too. Seems like many of the young green turtles we see in TCI’s waters will eventually migrate to Nicaragua, where, incidentally, there is a turtle fishery that catches an estimated 11,000 green turtles for consumption each year.

Of the three other satellite-tagged teenage turtles that migrated from TCI, two arrived at Cuba’s northern coastal waters before their transmissions abruptly ceased. One of these turtles was named David after Dave Clare the fisherman. We will never know why these turtles went quiet, but illegal turtle fishing is rampant in Cuba since it was criminalised back in 2008, so we think they may well have been caught. Another turtle named after Gilbert the fisherman headed north, swimming through the Bahamas and then travelling up the southeastern coast of the USA before catching the Gulf Stream at North Carolina and heading out into the open ocean. After a few days in the Gulf Stream—when his swimming speed went from about 50 km per day to about 90 km per day—he dropped out and started heading south back to the Bahamas before his tag ceased transmission. Who knows what Gilbert was doing, but likely he was originally from one of the USA nesting beaches and he was looking for suitable adult foraging ground nearby. Maybe he settled in the Bahamas where there are plenty of seagrass meadows.

As with any good biological research, we have ended up with more questions than answers, but these teenage turtles have helped us understand their maritime lives and, importantly, their conservation needs. The health of the protected RAMSAR site on the Caicos Banks is crucial for turtles and many other species, as is the health of a whole network of marine protected areas in the Turks & Caicos Islands. That is why, through our UK Overseas Territories (UKOTs) Conservation Programme, we are working closely with partners in the TCI and the other Caribbean UKOTs to ensure that the management, monitoring and enforcement of marine protected areas such as this special RAMSAR site are properly supported and resourced.

     This research wouldn’t have been possible without the generous support of many individuals and organisations. We received much-needed funding from the People’s Trust for Endangered Species, the British Chelonia Group, the National Marine Aquarium, Amanyara, Princess Yachts, Big Blue Unlimited, Surfside Academy and the NERC Knowledge Exchange Fellowship. We were also supported by many individuals including Anne and Simon Notley, the Blavatnik Family, the Wiese Family, the Gerrity Family, Keith Anderson, Kenneth De Regt and Alison Overseth, Patrick and Linda Flockhart, Stephen Meringoff and Kim Charlton, Eiglys Trejo, Andrew Snead and Kathleen and Simon Wood. Thank you for enabling us to better understand and hopefully better protect these incredible creatures and their precious habitats. 

A link to the new paper can be found at https://www.frontiersin.org/articles/10.3389/fmars.2020.00690/full.

To find out more about our turtle research contact Amdeep Sanghera at amdeep.sanghera@mcsuk.org.



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On the Cover

Agile LeVin—photographer, explorer and chronicler of everything TCI on his website www.visittci.com—took this drone photo of the multi-textured wetlands of West Caicos. He was part of the expedition that investigated the site of the historic pirate attack in the area. For more information and photos, go to page 48.

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