Many experts believe this behavior is actually a relic of the domestic dog's days in the wild. After all, wolves and wild dogs still utilize this behavior. On the taiga or savannah, circling serves to beat down grass, dirt and snow, just like it does on your comforters. But the behavior may also be a way to clear the night's nest of bugs, snakes and other creepy crawlies.
"I have also heard that circling the area and thus flattening it leaves a visible sign to other dogs that this territory has been claimed," says author and sociologist Leslie Irvine in an interview with "Life's Little Mysteries." "Even though our dogs now sleep on cushions, the behavior endures."
As for the digging that sometimes accompanies your dog's little circle dance, this may be the animal's attempt to regulate temperature. In the wild, veterinary behaviorist Karen Sueda says dogs dig holes in order to expose cool earth. Likewise, these depressions may provide a degree of shelter that help the animals conserve heat during winter.
Obviously, the dogs we call family aren't likely to need as much temperature regulation and pest control. But old habits die hard, especially if there's no reason for the behaviors to be selected against, evolutionarily speaking. Which brings us to a final reason why your dog might put on a show each time it takes a load off: Because he knows you like it.
"Dogs will do pretty much anything to get a response from their owners," says John Bradshaw, anthrozoologist and author of "Dog Sense." "And if spinning around a few times gets it a pat on the nose from the owner, then the dog will tend to repeat that."
That means if you're like me and you fawn all over your pooch every time you find her burrowing in her bed like a feverish woodchuck, then you're actually reinforcing that behavior and making it more likely. (Hmm, that's probably also why she wolf-howls every time she wants something.)
But what if you catch your dog circling and he doesn't seem ready for bed? Well, I'd watch out: He may be trying to align himself with the Earth's north/south axis for a different reason entirely.