First appeared on the Discover Magazine blog
“Magnetic Cows Are Visible From Space” is a memorable headline, and writers had occasion to use it several years ago, when, after poring over satellite pictures from Google Earth, a German research team reported that cows in the images reliably lined up along the magnetic field lines that run across the Earth. The magnetic field may be invisible to us without a compass (although we have sensors in our eyes that are theoretically capable of detecting it), but various animals, including sharks and turtles, are able to sense it, and one explanation for how birds manage to navigate on cross-continent migrations is that they are steering by the magnetic field. Are cows, too, endowed with magnetic field-sensing equipment?
That first paper, in 2008, and a follow-up in 2009, which showed that cows didn’t line up when they were near high-voltage powerlines (known to distort magnetic fields), seemed to indicate that they are. But an analysis of Google Earth images by another team finds no such lining up. In a back-and-forth over the last year in scientific journals, the first team reanalyzed the second’s data and said that half of the images were useless, since they were near high-voltage power lines or contained hay bales or sheep instead of cows. Plus, the first team points out that the second team looked at single cows within herds instead of herds as a whole, and it’s pretty clear at this point that animals in herds and flocks aren’t operating as independent entities. The second team retorts that their images were too okay to use, and the first team may have been looking at the wrong pictures.
So can cows sense magnetic fields? An outside researcher interviewed by Nature News says that in his opinion, taking into account the second group’s findings, the original results, “while mysterious, still stand.” And there are certainly other factors known to contribute to how cows line up, including the wind and the sun (they’ll turn into the wind and against the sun, to minimize the heat lost to wind and maximize the amount of warmth they get), although the first study did attempt to address this by using images that were from a variety of places and days.
Me, I’m holding out for the discovery of magnetism-sensing organs in cows. Ever since I read about the tiny tubes of electromagneto-sensing jelly sharks have running through their heads, I’ve wanted them for myself.