Cattle and deer grazing in fields tend to align themselves with the Earth's magnetic field, suggesting that the animals may have a built-in magnetic compass. A new study shows that animals in these herds tend to face towards either magnetic north or south, which has come as a surprise even to those who spend their days with bovines.
Asked whether he had ever observed such behavior in cows, dairy farmer Rob Fletcher of Tulare, Calif., said, "Absolutely not." But, he added, "I don't spend a lot of time worrying about stuff like that" [Los Angeles Times].
Researchers used satellite imagery from Google Earth to look for patterns in more than 300 cow-filled pastures from every continent except Antarctica, and in more than 250 herds of deer in the Czech Republic. While every individual animal didn't face the same direction, the herds, on average, pointed towards either magnetic north or south.
That orientation didn’t consistently line up with any aspect of the terrain on which they were grazing, the direction from which the wind was blowing or the direction from which the sun was shining, [co-author Hynek] Burda says. In fact, many of these field observations were made at night, he notes [Science News].
The study, published in the Proceedings of the National Academy of Sciences [subscription required], adds to previous findings that animals like migratory birds and subterranean mole rats can detect magnetic fields, which may help them navigate. As for why gentle grazers might have a magnetic sense, biologist Richard
Holland says it's not clear what cows or deer would get out of it. He says it may just be a leftover from their ancestors' ancient wanderings [NPR].
Professor John Phillips, a sensory biologist from Virginia Tech University, US, commented that this sixth magnetic sense might be "virtually ubiquitous in the animal kingdom". He added: "We need to think about some really fundamental things that this sensory ability provides in animals" [BBC News].
Learn what birds see when they tap into their magnetic sense with the DISCOVER article, "Birds Navigate Using Magnetic Compass-Vision."
Image: flickr/Irish Typepad