Animal magnetism: Why dogs do their business pointing north

Wiebke

By Henry Nicholls

Every dog owner knows how seriously their pet takes the decision of where to do its business. First it will pace in circles, nose to the ground, searching intently for the perfect spot. Once selected, there are another few turns and a shimmy until, finally, it is ready to commit. If you’ve ever wondered what’s going through a dog’s mind as it does this, the answer could be something like the spinning of a compass needle. Dogs prefer to defecate with their spine aligned in a north-south position, and they use Earth’s magnetic field to help them position themselves.

It has long been suspected that animals such as turtles and birds use magnetoreception to navigate, but it is becoming increasingly obvious that many other animals sense magnetism too, seemingly when they’re doing very little. Insects like to align their bodies along a north-south axis, as do sleeping warthogs, fish in tanks, nesting house mice and foxes on the hunt. So how are they are doing it and, more head-scratchingly, why?

Early evidence that animals align themselves in a particular direction was dug up more than 50 years ago by entomologist Purushottam Deoras. Called to a farm in a suburb of Mumbai with a severe termite infestation, including several mounds that had erupted inside the farmer’s hut, Deoras searched high and low for the queen – the key to eradicating the infestation. He eventually found her lying with her head pointing north, beneath a smattering of mounds that were orientated east-west. When Deoras looked at other colonies, he spotted that in almost every case, the queen aligned herself in this