<p>A bathtub-size female lazes through warm shallows near Indonesia's Kai Islands; remoras hitch a ride.</p>

A bathtub-size female lazes through warm shallows near Indonesia's Kai Islands; remoras hitch a ride.

Ancient Mariner

The biggest, deepest-diving, widest-ranging of all turtles, the leatherback has endured for 100 million years.

One late summer day in 1961 a biologist named Sherman Bleakney got a telephone call about a strange sea creature that fishermen had just unloaded on a wharf in Halifax, Nova Scotia. Bleakney, who lived nearby, was captivated by what he found there. Sprawled on its back amid a curious crowd was an immense black sea turtle tipping the scales at 900 pounds, with a soft, rubbery carapace, winglike front flippers, and a massive, conical head like an artillery shell. Bleakney recognized it as a leatherback, the biggest of all sea turtles. Leatherbacks, he recalled, were supposed to be creatures of the tropics, as out of place in chilly, gray Canadian waters as parrots in a Halifax park.

When Bleakney began asking around, though, he learned that fishermen saw leatherbacks swimming in the waters off Maritime Canada regularly enough to call late summer “turtle season.” The conclusion was inescapable, he wrote in 1965. “Evidently there is an annual invasion of our cool Atlantic coastal waters by turtles of tropical origin.” Their southern roots were obvious from the few dead turtles he examined. One had a twig from a tropical mangrove tree stuck in its eye; others carried warm-water barnacles. Yet the leatherbacks were surviving, even flourishing, at temperatures that would kill other sea turtles. Stranger still was what he found inside them: Their huge stomachs contained masses of chewed-up jellyfish, stinging tentacles and all, and their gullets were lined with three-inch spines, angled inward to hold in all that slippery prey.

Bleakney eventually moved on to other studies—sea slugs were a special passion of his—but he never stopped marveling at the great beasts he had encountered on the fishing piers of Nova Scotia. "It was mind-boggling," he recalled in a recent interview with Canadian conservationists. "A reptile of that size, that lives in ice water, that can thrive on jellyfish." Almost 50 years later, scientists are still astonished at the leatherback's physical prowess, though today wonder is alloyed with a more modern sentiment: fear that even before we fully understand the leatherback and its epic life story, our own activities may be driving it to extinction.

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