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MELISSA BLOCK, host:

This is ALL THINGS CONSIDERED from NPR News. I'm Melissa Block.

MICHELE NORRIS, host:

And I'm Michele Norris. Breaking news now on the bovine front. About six months ago, we reported on why cows tend to face one direction rather than the other when grazing or resting.

Scientists have done a study suggesting that cows actually sense the earth's magnetic field. Now, NPR's Nell Greenfieldboyce reports that a follow-up study of more cows has found that this magnetic sense can be disrupted by high-voltage power lines.

NELL GREENFIELDBOYCE: Hynek Burda is a zoologist at the University of Duisburg-Essen in Germany. Last year, he and his colleagues were flabbergasted by how much attention their cow study got. All kinds of newspapers and Web sites discussed the story. Burda got hundreds of emails.

Dr. HYNEK BURDA (Zoologist, University of Duisburg-Essen, Germany): At the beginning, they didn't expect it, and don't know about the matter, why the cows are so interesting.

GREENFIELDBOYCE: He and his team had found that cows tend to align their bodies so they face either magnetic north or south. The researchers used Google Earth to get overhead images of thousands of cows around the world, and while they gathered those pictures, they were already thinking about another study they could do to investigate how cows react to magnetic fields.

Dr. BURDA: If you are searching for cows in Google Earth, or if you are observing them in the fields, sooner or later you will see them also under power lines.

GREENFIELDBOYCE: High-voltage power lines create local disruptions in the earth's magnetic field. So Burda looked at over 1,500 cows in more than 150 pastures, all of them under or close to power lines. These cattle seemed confused.

Dr. BURDA: Under these power lines, the orientation of the animals is random, in all directions, so it means the animals don't show any preference for north, south, direction.

GREENFIELDBOYCE: The findings are reported in the proceedings of the National Academy of Sciences. Burda says there's more work to be done, but this adds to the evidence that big mammals, like cows, can be as sensitive to magnetic fields as certain bats and rodents. Nell Greenfieldboyce, NPR News.

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