The Leatherback: Earth’s Last Dinosaur

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I was 14 and in awe of the seafaring skills of my uncles Sal and Tony, but actually we’d ventured only a few miles into the Atlantic; you didn’t have to go far to catch Bluefin Tuna in the 1960s. I was wound with anticipation of a heavy fishing rod suddenly bending under the frightening power of a great fish. I was gazing with a child’s eyes into the infinity beneath us when suddenly a strange sea beast appeared at the surface about fifty yards off our stern. It was a creature so large the sea broke into whitecaps across its back. I was thinking it looked like a Volkswagen floating just under the surface, when it raised its unbelievably huge head, drank a deep breath of air, and withdrew. Thus ended my first awestruck encounter with the greatest turtle on Earth.

PARTNERSHIP: The Great Turtle Race at National Geographic

I never forgot my encounter with that astonishing beast. And so, not long ago, I decided to travel the world in pursuit of the biggest animal that a person can walk up to without being attacked: the leatherback turtle. I traveled from Nova Scotia to Georges Bank to the waters off the Carolinas, to the nesting beaches of Florida and the Caribbean. I ventured from Mexico to Costa Rica. I helped tag leatherbacks just off California, then went across the Pacific to New Guinea, where the “California” leatherbacks swam to nest, a migration that takes them over a year. They are true world travelers. My own global encounters make up my book, Voyage of the Turtle.

There exists a presence in the ocean, seldom glimpsed in waking hours, best envisioned in your dreams. While you drift in sleep, turtles ride the curve of the deep, seeking their inspiration from the sky. From tranquil tropic bays or nightmare maelstroms hissing foam, they come unseen to share our air. Each sharp exhalation affirms, “Life yet endures.” Each inhaled gasp vows, “Life will continue.” With each breath they declare to the stars and wild silence. By night and by light, sea turtles glide always, their parallel universe strangely alien, yet intertwining with ours.

– Excerpt from The Voyage of the Turtle, © 2006 Carl Safina, Henry Holt and Company

The leatherback turtle is the closest thing we have to a last-living dinosaur. But while its ancestors saw dinosaurs rule and fall, the leatherback survives to the present. It’s Earth’s last greatest monster reptile. Imagine an 800-pound turtle and you’ve just envisioned merely an average female leatherback. It’s a turtle that can weigh over a ton.

Everything about the leatherback is superlative: it’s the fastest-growing and heaviest reptile, the fastest-swimming turtle, the most widely distributed and highly migratory reptile, and the only one that could be called “warm-blooded.”

A turtle’s registered trademark, of course is their shell. But leatherbacks have, in a sense, no shell. Rather than a hard-bone carapace, the back forms over a mosaic of thousands of small, thin bones, overlain by a thick matrix of oily fat, fibrous tissue, and skin. Scratch it with your fingernail – it bleeds.

Ranging from the tropics to beyond the Arctic Circle, leatherbacks can maintain body temperature around 80º Fahrenheit (27º C) even in waters as cold as about 40º Fahrenheit (5º C).

Such temperatures would chill a human to death in minutes and kill other sea turtles. But leatherbacks generate heat, then conserve it through a combination of large body size, insulating tissue, and special heat-conserving circulatory plumbing.

Leatherbacks dive deeper than any air breathing animal – deeper than any whale. Emperor Penguins reach 1,500 feet, and several seals get to 3,000 feet (a kilometer). Sperm whales go as deep as 3,700 feet. Blowing past them all, the leatherback drills as deep as 3,900 feet (1.2 km).

At that depth, the pressure has gone from under 15 pounds per square inch at the surface, to about 1,800 p.s.i. – roughly 120 atmospheres. In such cold and dark, a human would implode like bubble-wrap. This deep squeeze may explain leatherbacks’ flexible shells – defense against cracking during the deepest dives. They can stay down over an hour. To do that, leatherbacks pre-dissolve their oxygen reserves right into their blood. They can actually load more oxygen into their blood than into their lungs.

Everything about the leatherback is astonishing. One of the most amazing things is that such ancient monsters actually remain in the world with us. They’ve survived millions of years, but they’ve never had it easy. And they still don’t.

After swimming the ocean for years, after migrations from one continent to another, females come ashore to continue the unbroken chain of leatherback being. Each female encounters a differing set of challenges every time she hits the beach. She may come where the beach is too steep; she may come on the wrong tide; she may arrive where the beach is too narrow; she may ascend to find a wrack-line obstructed with drift-logs and trash – or a man with a machete.

But so far, leatherbacks survive. And with a little help they will, for a long time to come.

Dr. Carl Safina brought ocean conservation into the environmental mainstream and is founding president of Blue Ocean Institute. His award-winning books include “Song for the Blue Ocean,” “Eye of the Albatross,” and “Voyage of the Turtle.” He’s been profiled by the New York Times, Nightline, and Bill Moyers, and his awards include a Pew Fellowship, Lannan Literary Award, John Burroughs Medal, and a MacArthur Prize, among others.

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