Science - April 12, 2018

Cows do not have a built-in compass

Roelof Kleis

Cows do not lie with their heads facing north significantly more often than any other direction, and it is unlikely that they have a built-in compass with which they register the earth’s magnetic field. This finding comes from experimental Wageningen research.

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Many animals can feel the earth’s magnetic field. This capacity is a big part of the explanation for migrating birds’ amazing powers of orientation. But can cows do it too? And is that why they so often face north when they lie down? Some studies say so, but the evidence is meagre, says Ignas Heitkönig of Resource Ecology.

Cow with a magnet around the neck. © Debby Weijers
Cow with a magnet around the neck. © Debby Weijers

MSc student Debby Weijers set out to find a conclusive answer based on experimental research. Under the supervision of Heitkönig and statistician Lia Hemerik of Biometris, she studied the orientation of 659 cows on six difference farms in Portugal when they were lying down during the day, on one or more occasions.There was no question of any preference for a north-south orientation. There was on average a slight preference for a position facing south-east. But there is another explanation for that. That alignment (130 degrees on a compass) correlates significantly with the position of the sun at the time the data was collected, and it reduces exposure to the sun, helping the cow to avoid overheating. This sun-avoiding orientation has previously been observed among wildebeests, impalas and eland in Africa, says Heitkönig.

Weijers also studied 34 cows to see what happens if you hang a strong magnet around their necks, which would disrupt any internal compass. She found this had no effect on the cows’ orientation when lying down.

Is this the last word? No, says Heitkönig. ‘This is a first experimental study among large ruminants, and it suggests there is no reason to suspect the presence of an internal compass. But the study should really be repeated at night.’ Any student who would like to do that should get in touch.