Older cranes know the way
Whooping cranes will soon be leaving their summer nesting grounds in Wisconsin and Alberta, Canada, and flying south to Texas and Florida for the winter, journeys of more than 1,000 miles. Their migration is not the longest trip that birds make (Arctic Terns travel from the Arctic to the Antarctic), but it is lengthy enough that we puzzle about how migratory birds—especially the youngest ones—manage to do it.
Is the map somehow encoded in their genes? Or do they learn the route? The question has been called one of nature’s greatest mysteries.
But it’s a mystery no more. In Science, a team of scientists reports that whooping cranes—and by extension all birds that migrate—do indeed learn their migratory routes. In their first years, young whoopers are like apprentices. They travel with older, more experienced birds that know the way.
Such a discovery might seem obvious to most of us, but a gut instinct is not the same thing as proof. Without proof--that is, solid data--to verify what you think is happening in another animal’s mind, you’ll always face a phalanx of skeptics who prefer to regard animals as hardwired zombies.
Whooping cranes' long journey.
The scientists studying the whooping cranes gathered eight years of migration data collected from a reintroduced population. Their analysis showed that one-year old cranes deviated less than 40 miles from a straight-line path, if they had a wise bird as a guide. Those that didn’t follow older birds veered off by 60 miles on average.
Why does this matter? It tells us that whooping cranes are smart and sentient—that they are, like us, animals actively engaged in the world, not automatons flying on autopilot. It also tells us that older animals are important in the cranes’ society. Scientists have made this same discovery about elephants and cougars. The wisest matriarchs in an elephant herd are the oldest females, and herds with older females raise more calves. And the wisest mountain lions—the ones that get into the least amount of trouble with people—are the older animals.
Tall and gawky on the ground, whooping cranes are elegant creatures in the sky, with their long white necks and black legs stretched fore and aft. Now we know that they are also students, engaged in social learning. As the birds travel, the scientists say that some type of “cultural transmission of information” is taking place. It is not obvious to our eyes, but the older birds are helping the younger ones learn the landmarks, the refueling stops, the celestial cues, and weather patterns.
All this matters, too, because whooping cranes are among the most endangered of birds. Before the arrival of Europeans to North America, there were more than 10,000 whooping cranes. Overhunting and habitat loss sent their numbers plummeting to a mere 1500 by 1870. In 1941, there were only 23 left—21 in the wild, and two in captivity. Yet not until 1967 did the IUCN finally declare the species endangered.
Operation Migration pilots lead young cranes on their first migration.
To save the cranes from extinction, biologists and conservationists have raised captive chicks, and with the assistance of the nonprofit Operation Migration
trained them to follow an ultralight aircraft to their wintering grounds. But humans assist the chicks only on their first migration. After that, the birds travel on their own; they must find their own way back to their summer nesting lands.
People do monitor the cranes’ movements using satellite transmitters, radio telemetry, and observers. And it was from these data that Thomas Mueller and his colleagues from the University of Maryland, Smithsonian Conservation Biology Institute, the US Geological Survey , and the US Department of Fish and Wildlife figured out that the cranes’ ability to stick to the shortest route wasn’t affected by their gender or genetics; the number of birds they were traveling with didn’t matter, either.
What the young cranes needed was what all students require: One wise old bird to show the way.