LINDA WERTHEIMER, HOST:

Being a wildlife biologist in the 21st century means, increasingly, rescuing rare animals from extinction. Among the success stories is the whooping crane. Seventy years ago, there were only 16 of these birds left on the planet. Their habitat had disappeared, and they were hunted for their feathers. Now there are about 600.

But breeding more birds is not enough. Scientists want to restore the crane's way of life, its culture. NPR's Christopher Joyce reports on a discovery that suggests the cranes are learning to do that themselves.

CHRISTOPHER JOYCE, BYLINE: Many of the whooping cranes in the world were born in a wooded wilderness 20 miles from the U.S. Capitol.

GREG SMITH: This is the closest I've ever been to a whooping crane.

JOYCE: Really?

SMITH: Yeah.

JOYCE: They seem sort of curious.

SMITH: They are.

(SOUNDBITE OF WHOOPER CALLING)

JOYCE: An adult whooper lets loose, as Greg Smith and I stand just outside its chain-linked enclosure. Nearby, brown-feathered one-year-olds peep. The adult is four feet tall, snow white and elegantly long-legged. Smith's a biologist and heads the Patuxent Wildlife Research Center in Maryland. A short walk through the woods leads to a labyrinth of fenced enclosures holding scores of whoopers.

Fabric screens on the fencing keep them from seeing us. That's so they won't become accustomed to humans.

SMITH: The more fear they have of humans, the better off we think their survival chances are.

JOYCE: Whooper eggs from around the country come here. Biologists hatch and raise the birds. Workers wear white coveralls and hoods and use whooper puppets to mimic adult birds. Then, the weirdest part is someone drives around the enclosures in an ultralight, one-person aircraft on the ground. The birds think it's an adult crane.

Then they ship the yearling birds to Wisconsin, where another ultralight plane awaits.

SMITH: The ultralight in Wisconsin not only circles on the ground and teaches them to follow, but also ultimately lifts up into the air and makes this great migration of between 50 to over 100 days to Florida.

JOYCE: This yearly migration was created by a group called Operation Migration. After the first time, the birds migrate all on their own. But after a dozen years of this, scientists noticed something unusual. Some groups flew a nice, tight route. But others drifted 40 or 50 miles off the ideal migration route, and it appeared there was only one difference between the straight-ahead flyers and the crooked ones: an older bird.

THOMAS MUELLER: If there was one older bird in the group, they would fly more accurately.

JOYCE: Thomas Mueller is an ecologist at the University of Maryland. He and ecologist William Fagan found that migrating groups with lots of genetically related birds didn't do any better than unrelated birds. So, apparently, it wasn't some innate genetic skill at work, here. Fagan adds that as the birds got older, their flying group got better.

WILLIAM FAGAN: It's amazing in the sense of it's a concrete demonstration of the animal's ability to learn, and how that learning can be refined over time.

JOYCE: Now, of course, adult animals do teach their young chicks to fly, chimps to dig for termites, all sorts of life skills. But Fagan says this is more unusual: younger birds learning a very complex skill, first from humans, then from unrelated older birds. And that skill improves.

FAGAN: Here is cultural learning that is an improvement in a very large-scale process, that is migration in over 1,000 kilometers distance.

JOYCE: The researchers published their findings in the journal Science. They suspect there is some innate ability involved in crane migration, too, but clearly, doing it well is learnable. Exactly what they're learning, well, they don't know for sure. Patuxent ecologist Sarah Converse suspects it's landmarks along the way. But Converse says the really important thing here isn't just navigating better. It's that birds bred and raised by humans are learning from each other how to be, well, real whooping cranes.

SARAH CONVERSE: We're actually trying to restore not just a biological population, but actually a culture. So there's a knowledge that whooping crane populations have that they pass on amongst individuals - not just genetically, but learning.

JOYCE: Converse says if the birds can refine migration skills, maybe they can learn something else they've forgotten: How to reproduce better in the wild. They're pretty terrible at that right now. They'll need to be better if they're going to make a true comeback. Christopher Joyce, NPR News.

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