MELISSA BLOCK, host:
From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.
MICHELE NORRIS, host:
And I'm Michele Norris.
One of the great spectacles in the natural world is the migration of big animals. Think of the wildebeest in Africa or caribou in Alaska. Thousands of animals move together across the landscape to find food or water or to escape deep snow. But these migrations are disappearing, and scientists are just now noticing.
NPR's Christopher Joyce has this report on an endangered act of nature.
CHRISTOPHER JOYCE: Grant Harris, a wildlife biologist with the U.S. Fish and Wildlife Service, is fascinated with ungulates - hoofed, grass-eating animals like caribou, gazelle and wildebeest. Harris calls them charismatic megafauna because they are big and showy and, in the case of ungulates, their migrations can be spectacular.
Dr. GRANT HARRIS (Wildlife Biologist, United States Fish and Wildlife Service): Here we have these charismatic megafauna marching hundreds of kilometers from, like, New York to Boston and back, those sorts of distances, in aggregations of the thousands.
JOYCE: Harris and his colleagues documented 24 great ungulate migrations from the historical record: wildebeest and oryx in Africa, caribou and bison in North America, the Mongolian gazelle and the antelope-like chiru in Asia. They say it's the first time anyone's studied all these migrations systematically, and they found that many of them have disappeared in the last several decades.
Dr. HARRIS: So of those 24, we've lost six species that do not migrate in large masses, in long distance anymore.
JOYCE: So that's one quarter no longer migrate.
Dr. HARRIS: Correct. Shame on us. We've missed a ball, and we're losing these migrations.
JOYCE: In some cases, the animals are extinct. Hunting killed off many big herds. Where they weren't shot, it was roads, towns and especially modern agriculture, with miles of fencing that cut off migration routes.
These animals now survive in reserves or parks managed by people. That's the case with the scimitar-horned oryx. Once, it traveled across the North African desert by the thousands in search of grass and water in a desert that was constantly changing.
Like other migrating ungulates, its grazing controlled what vegetation grew where, and its feces fertilized the land. Now, you have to go to a zoo to find the scimitar-horned oryx.
Dr. STEVEN MONTFORT (Acting Director, National Zoological Park Research, Smithsonian Institute): You're looking at one of the most beautiful animals known to man.
JOYCE: Steve Montfort describes a half-dozen scimitar-horned oryxes, nibbling grass in a fenced enclosure at the National Zoo in Washington, D.C. Montfort runs the zoo.
Dr. MONTFORT: They are large, about 250- to 300-pound animal, mostly white-bodied, and they have these magnificent, long, sloping horns that are several feet long that are shaped like swords or scimitars, and so they were named the scimitar-horned oryx.
JOYCE: There are only a few hundred left now.
Dr. MONTFORT: So here we have one of the largest numbers of large mammals that ever existed - disappeared without a whimper. Nobody knew they were there; nobody cared that they were gone. And so what was the problem there? Well, the problem was they were in a very unpopular part of the world. Let's be honest. Most people think of the Sahara as a wasteland.
JOYCE: So scientists didn't notice. Now, zoos and reserves must hold off extinction, but Montfort says it's much harder to restore a migration.
Dr. MONTFORT: If you've fenced in scimitar-horned oryx, and I really don't care how big of a fenced area, there's a chance that the rain and the grasslands are going to fall outside of that fenced area. They're going to go right to the fence line, and then they're going to starve to death.
JOYCE: As for the remaining 18 ungulate migrations, many are no longer what they used to be. Joel Berger of the Wildlife Conservation Society worked with Harris on the migration study.
Dr. JOEL BERGER (Senior Conservation Biologist, Wildlife Conservation Society): Longhorn migrations are a mere sliver of what they used to be. Elk migrations are a sliver of what they used to be, and so I think our 25 percent glimpse globally is probably a huge underestimate.
JOYCE: Harris and Berger, whose study appears in the journal Endangered Species Research, say there's hope in wildlife corridors, protected areas - even only a mile wide - that connect wild animals to different grazing grounds. That could work for some animals like bison or antelope. Wildlife biologists like Steve Montfort at the National Zoo say it could be a lot harder preserving the really big migrations, like the wildebeest in Africa's Serengeti.
Dr. MONTFORT: Literally, hundreds of thousands of wildebeest for as far as the eye can see, it's just incredible. And you can't help but wonder what would happen if they weren't there.
JOYCE: Christopher Joyce, NPR News.