Source: Department of Conservation
By Krysia Nowak and Karen Middlemiss
*While leatherback turtles don’t actually have a shell, they have pretty thick skins, so we think they wouldn’t mind the pun.
What if we told you the largest sea turtles in the world visit Aotearoa New Zealand and that our waters are important to their survival? That they’re Critically Endangered, and that we know almost nothing about how they spend their time here?
You might say it’s about time we learn about them, and that’s exactly what we’re doing in our new research collaborating with USA-based Upwell Turtles.
Turtles crossing borders
Leatherback turtles aren’t worried about international boundaries.
The leatherbacks which visit New Zealand waters are part of the Western Pacific population that forage on the US West Coast and then migrate some 12,000km to nesting beaches in Indonesia, Papua New Guinea, New Caledonia, and the Solomon Islands.
Leatherbacks have been tagged for monitoring when they come ashore at nesting beaches overseas, but there aren’t many known foraging areas where it’s possible to tag them in open water and study their movements. The Bay of Plenty is one of those known areas.
For the love of jelly(fish)
We have the opportunity to tag turtles at sea during summer and early autumn when our waters are full of their favourite food – jellyfish!
Leatherbacks can weigh more than 350 kilograms and need to eat more than 1/2 their body weight in jellyfish to get enough energy for long trips. The jellyfish-rich waters off the Bay of Plenty are important to leatherback migration success.
Running the gauntlet
Leatherbacks face many risks in various countries across the huge distances they travel between foraging grounds and nesting beaches. Threats can include unintentional capture by fisheries (bycatch), the harvesting of adult turtles and eggs, plastic pollution, nesting beach habitat loss, climate change, and vessel strike.
Currently, the biggest threat to leatherback turtles, globally, is from commercial fishing. Most turtles accidentally caught by fisheries in New Zealand waters are released alive, but we need to learn how to reduce bycatch numbers to better protect them.
It’s a minefield for a turtle travelling across international boundaries, and we’ve seen a decline in this population of over 80% in the last 40 years. That’s why international collaboration is so important for their research and conservation if we are to have any chance of recovering the population.
Collaborating for conservation
We’re working with scientists who have been studying leatherbacks for decades. Being able to work together to study their habitat use in New Zealand waters will be another piece in the migration puzzle for these ancient turtles.
Dr George Shillinger, Executive Director of Upwell Turtles, says leatherbacks are among the most highly migratory and transboundary marine species on the planet.
“Effective conservation requires international collaboration from nesting beaches all the way to distant foraging habitats.”
Taking to the air
Our turtle-team recently took to the air over the Bay of Plenty as a starting point to find out more about leatherbacks in New Zealand waters. We worked with Upwell Turtles, and with support and expertise from NIWA, Monash University (Australia), and Moss Landing Marine Laboratories (USA).
While we had George and Scott here from Upwell Turtles, they graciously gave us some of their time and expertise, to help develop our own techniques to catch and tag leatherbacks.
Practice Makes Perfect
Along with our international experts, we assembled an array of technical equipment, and formed a team including Tauranga DOC staff, Tuhua Island kaitiaki, and a local marine conservationist, all eager to embrace the challenge of finding and netting such large animals.
Heading out on our DOC boat off the coast of Tauranga on calm, sunny weekend in March we focused our efforts on a large rubber fender co-opted as a ‘pretend’ turtle. Few fenders have had such an exciting couple of days!
The team has now honed the required skills and techniques to safely net actual turtles. In future, when we do this for real, we will have a spotter plane in the air and other boats on the water to help us find turtles – leatherbacks can be tricky to spot from sea level.
Where to from here?
Because leatherback turtles have historically visited the Bay of Plenty, we’re working to build partnerships with local iwi and hapū, and the Bay of Plenty community, as well as collaborating with our research partners.
We’re starting to plan our next steps into the world of tagging, aiming for next summer when the turtles and jellyfish have returned to the Bay.
Everything we learn from tagging studies of leatherback turtles in our waters will help inform future conservation efforts for this species, which is so ancient we call it the tuatara of our oceans. We’ll be doing our part in the international effort to protect a species on the brink of extinction.
How you can help leatherback turtles:
• No marine turtles nest on beaches in New Zealand, any turtle on the beach should be reported immediately to 0800 DOC HOT (0800 362 468).
• Spot a sea turtle in the water around New Zealand? You can report sightings to turtles@doc.govt.nz
• You can help protect leatherbacks and other marine animals by preventing plastics and pollution from reaching our oceans.
