Humans don’t typically have any complex pre-poop rituals. Most just make sure they’ve got their phone on them, lock the door, and go for it. But dogs have a tendency to preface their bowel movements with a bit of rotating, spinning around for a while before getting down to business.

What’s going on? Is there a complex reason behind it, or is it just the dog poop equivalent of shaking a bottle of ketchup?

Various theories have been bandied about over the years. Some thought it was originally a method of flattening grass in order to create a more pleasant, less anus-spiking place to poop. Others suggested it was a safety issue—a quick scan for predators before getting into a vulnerable position.

However, a 2013 paper in the journal Frontiers in Zoology suggests that something more complex is going on—and that a pup's pre-poop pirouettes actually have something to do with calibrating themselves in relation to the Earth’s magnetic field, or at least trying to. Just as birds use the planet’s magnetic poles to navigate (a.k.a. magnetoreception) during migrations, dogs use theirs to plan the perfect plop.

Zoologist Hynek Burda and his team spent two years analyzing dumping hounds, watching 1893 poops get pooped and measuring the dogs’ alignment. During the 20 percent or so of daylight hours in which the Earth’s magnetic field is stable, dogs will align themselves to be facing either due north or south while pressing one out. In times of less magnetic stability, when they can’t detect the poles, they’ll try for a while (by spinning around) and then face any direction.

Why? Burda suggests that aligning themselves might help dogs to remember the spot, which is important information when marking their territory.

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