By Nina Dragicevic  

For sea turtles, it’s a miracle just to survive. It’s estimated that only one out of 1,000 hatchlings will live long enough to reach adulthood.

To thrive on Earth for more than 100 million years, these ancient reptiles have had to find safety in numbers. In Turtle Beach, a documentary from The Nature of Things, a mass nesting event — called an arribada — sees tens of thousands of olive ridley sea turtles come ashore in Ostional, Costa Rica, to lay millions of eggs on the same beach where they themselves were born.

Arriving together in such numbers and synchronizing their egg-laying is thought to be a “predator swamping” behaviour: an effort to overwhelm the many animals that come to eat hatchling turtles, allowing for that very slim margin of survival.

Researchers hail the arribada as one of the most remarkable mass activities in the animal kingdom — even though many mysteries about how these turtles manage the feat, year after year, still linger.

Poaching nearly decimated sea turtle populations

Humans are one of the most voracious predators of sea turtles, and a number of turtle species are sought for their meat, fat, oil, eggs, skin or shells.

Over many centuries, widespread and catastrophic levels of consumption has decimated global sea turtle populations. Some scientists have estimated that the number of green sea turtles in the Caribbean has declined by as much as 99 per cent since the arrival of Christopher Columbus in the region.

This decline in sea turtle numbers has led to conservation efforts over the past half-century — efforts that are working, says Roldán Valverde, scientific director at the Sea Turtle Conservancy in Florida and a professor at Southeastern Louisiana University.

“In general, sea turtle populations across the globe have been rebounding,” Valverde says. “They are not up to historical levels, but they are rebounding. And the one thing in common to all conservation projects is the protection of the eggs and the beaches.”

Tracking illicit trade with GPS technology

Sea turtle conservation efforts have evolved over the decades, and increasingly technology is playing a key role.

Conservation biologist Helen Pheasey has embraced the latest in 3D printing and GPS tech for her doctoral project, which involves sneaking into the poaching underworld and tracking the illicit trade of sea turtle eggs.

Pheasey is doing this by placing 3D-printed decoy eggs, enabled with small GPS tracking devices, into clutches that may be vulnerable to poaching. “Then what she’s done is track the routes of trade, basically, in the black market,” Valverde says.

Valverde expects the illegal trade information to be published when the project wraps up later this year. Such information would be invaluable for conservation teams seeking to get ahead of the problem and reduce poaching behaviour.

But why do poachers target nests and not the turtles themselves? Culturally, he explains, the eggs are popular in the region. Sea turtle eggs don’t cook well, so they’re knocked back raw in a potent drink instead.

“Especially in Costa Rica, they make a drink that is basically tomato sauce, lime and hot sauce. It has a few components, and they add that to the egg and they just chug it raw,” Valverde says.

“The reason people do it — it’s mostly men, I would say — is because there is this notion that these eggs may be an aphrodisiac,” he says. “There’s no proof of that; everything we’ve seen shows that’s not the case. But the lore is that this happens, so many still continue to consume eggs in great numbers.”

Legal egg harvest may help maintain a healthy population

According to Valverde, legalizing small, controlled harvests of sea turtle eggs can actually benefit both humans and turtles: humans have legal access to a popular delicacy, and there tends to be less nest destruction among the turtles themselves.

It works in Ostional, he says — the site of the spectacular arribadas.

“Basically, a maximum of 8,000 nests are taken for the egg harvest,” he says. “If there was no egg harvest, a large proportion of the eggs that are laid in the first two, three nights [of an arribada] would be destroyed by the [following] nesting turtles because of the nest density.”

When one female turtle inadvertently digs up an earlier nest, Valverde explains, the eggs can easily break and contaminate new nests with potentially unhealthy microbes.

“So one of the intentions with allowing the egg harvest is to reduce the nest density … and hopefully the hatching success would increase.”

I missed Christmas with my family to film tens of thousands of sea turtles come ashore in Costa Rica
Turtle teamwork: Sea turtles help each other out before they've even left the nest

Mysterious turtle nesting behaviour still puzzles biologists

Efforts focused on the black market and a legal cull are major parts of the conservation picture. But so little is understood about arribadas — except that they are absolutely crucial for the species to survive.

Protecting the phenomenon needs to be informed by how it works, yet some aspects of arribadas remain as mysterious as when they were first discovered.

“No one knows how the arribada behaviour is regulated,” Valverde says.

He ticks off a list of unanswered questions: How do olive ridley turtles know where to nest? The beach at Ostional, for instance, stretches for eight kilometres, but turtles frequent a single, 800-metre stretch of beach over and over again.

And how do they know when to nest? The turtles congregate for weeks offshore before an arribada gets underway and they leave the waves to nest. What do they wait for? What’s the signal?

“No one knows,” he says. “My fear, personally, is that I will leave this world without knowing. Yes, that sometimes keeps me up at night.”

Watch Turtle Beach on The Nature of Things.


The Wild Canadian Year

Wild Canadian Year

Visit our website to watch the series online, discover extra behind-the-scenes stories and view Canada's nature scenes in 360. Visit Wild Canadian Year

From CBC Kids

The Nature of Thingies