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Whether they’re moving bears, beavers, or bull trout, conservation biologists often rely on translocation to resuscitate ailing wildlife populations. The premise is simple: grab some animals from a robust group, stick them in unoccupied habitat, and, if all goes well, watch them flourish. But not all species appreciate being hauled far from home—and few creatures are as uncooperative as sea turtles.
That’s what Takahiro Shimada, an environmental scientist at Australia’s James Cook University, has come to understand after years of moving loggerhead, green, hawksbill, and olive ridley turtles during research projects. Many of his study subjects, Shimada noticed, seemed to wander tens of kilometers back to their foraging grounds—regardless of where he’d put them.
Shimada found himself wondering about these homeward migrations. Previous research has shown that sea turtles likely migrate using both geomagnetic fields and chemical cues. Shimada wondered to what lengths turtles would go to make the homeward trek.
To find out, Shimada and his team analyzed data from 59 turtles that had been captured, outfitted with tracking devices, and relocated along the coast of Queensland, Australia. The results were expected, but still striking: a whopping 88 percent of the displaced animals returned to their home territory. Even the turtle that had been moved the farthest—117 kilometers—made its way back. The successful migrants also included an injured animal that remembered its route despite being held captive at a rehabilitation center for nearly 18 months. Neither distance nor time seemed to deter the homesick reptiles. Shimada believes turtles return home because they’re seeking a home-field advantage: after all, it’s easier to find food and evade predators in familiar waters.
“Some turtles were able to pinpoint a very small home range, just a few square kilometers,” Shimada says. “I expected a lot of them to go back, but I didn’t expect such amazing accuracy.”
Though moving adult turtles may not be a particularly effective conservation tactic, sometimes relocating eggs is the best option. In 2010, for instance, the Deepwater Horizon oil rig spilled an estimated 4.2 million barrels of crude into the Gulf of Mexico—and directly into the path of tens of thousands of loggerhead turtle hatchlings set to emerge from nests across the Florida Panhandle. To prevent catastrophe, the federal government, with the help of the nonprofit organization Sea Turtle Conservancy, unearthed hundreds of nests, packed the ping-pong ball-sized eggs in styrofoam and sand, and moved them en masse to Florida’s Atlantic coast. When clutches began to hatch, technicians rushed the babies to the beach.
“They were probably pretty confused when they hit the water, but the project gave them a good chance at survival,” says David Godfrey, executive director of the Sea Turtle Conservancy.
Because the transplanted hatchlings were too small and fragile to be tagged or marked, we’ll likely never know their fate. Godfrey, however, suspects that they’ll someday return to nest along the Gulf Coast where they’d been deposited as eggs, rather than the Atlantic beaches where they’d been set free—all the more reason to ensure that the Gulf’s beaches truly recover. “They’re likely born with prior genetic knowledge of what their geomagnetic map looks like,” Godfrey says.
So what does this remarkable site fidelity mean for conservation? It depends who you ask. If you’re a wildlife rehabber, it’s encouraging: it means you can heal a wounded turtle in captivity while remaining confident that it will head home once you turn it loose. But turtles’ unerring homing abilities also come with a downside: once a beach loses its population, translocations almost certainly won’t bring it back. “The best strategy would be to conserve sea turtle habitat in the first place,” Shimada says—advice that advocates of every species would do well to heed.