MELISSA BLOCK, BYLINE: From NPR News this is ALL THINGS CONSIDERED I'm Melissa Block.
ROBERT SIEGEL, BYLINE: And I'm Robert Siegel. Biologists in Africa have discovered something they've never seen before - a marathon migration by at least 2000 African zebras across some of that continent's wildest terrain. They've determined this migration covers more miles than any other by mammals in Africa. NPR's Christopher Joyce has the story.
CHRISTOPHER JOYCE, BYLINE: You'd think that a gigantic herd of 700-pound zebras travelling across a big swath of Africa would draw some notice. Well, wildlife biologists say, no, they didn't know about this at all, not from observations nor from any local people who might have seen it. What got them onto this was something they noticed in the West African country of Namibia.
ROBIN NAIDOO: A large number of zebras seemed to be showing up in the very northeast of the country, and then they seem to disappear.
JOYCE: Robin Naidoo studies migratory animals at the World Wildlife Fund. This disappearance intrigued him and other biologists in Namibia, so they put radio collars on eight of the disappearing zebras and tracked their movements. It turns out they walk about 350 miles round trip into neighboring Botswana and back.
NAIDOO: The sheer length of it is something that we haven't seen before.
JOYCE: Now, the wildebeest and Africa's Serengeti horned animals, similar to wild cattle, migrate in higher numbers, but Naidoo say no mammal goes as far as the zebras in Africa.
NAIDOO: And what's really impressive is just how straight a direction they go. It's as if the zebras set a compass to due south in Namibia and just head in that direction.
JOYCE: The reason the zebras do this this appears to be water.
NAIDOO: We think what triggers the migration is rains at the end of the dry season. So zebras catch wind of rains occurring in the direction that they've traditionally headed to.
JOYCE: Naidoo acknowledges that this explanation is just a guess for now. He describes the migration in the wildlife journal called Oryx. Conservationists note that the migration takes place entirely in a string of nature preserves that several countries have created to protect wildlife. Christopher Joyce, NPR News.
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