for National Geographic News
Cattle and deer all over the world tend to align themselves with Earth's magnetic field, according to new research.
Both types of animals appear to graze in a north-south direction that aligns with magnetic north, not geographic north, according to European researchers who scrutinized thousands of Google Earth images.
Birds, turtles, and fish are known to use magnetic guidance in migration. And among small mammals, a handful of rodent and one bat species have been shown to possess a magnetic compass.
Sabine Begall, a zoologist at the University of Duisburg in Essen, Germany, and her colleagues propose that large mammals may also sense Earth's magnetic field.
But why the nonmigrating animals would align themselves according to Earth's magnetism is still a mystery, the authors say.
The study appears in this week's issue of the Proceedings of the National Academy of Sciences.
Begall said her team first got the idea to look for cows' sensitivity to magnetism after one of the co-authors, Hynek Burda, also of the University of Duisburg, discovered such sensitivity in African mole rats.
(Related story: "Rat Radar: Rodent Uses Natural 'GPS'" [January 29, 2004])
"At one point last year the question came up whether large animals could also sense the Earth's magnetic field," she wrote in an email. "But of course, it is difficult, or maybe impossible, to do these studies in the lab."
Instead, Begall and her team surveyed Google Earth images of 8,510 cattle in 308 pastures and plains around the world and examined other data collected on 2,974 deer in more than 225 locations in the Czech Republic.
They found that the animals, when grazing or resting, tended to face either magnetic north or south.
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