The Surprising Reasons Your Dog Curls Up in a Ball Before Going to Sleep

Besides being great companions and painfully cute, dogs can be a little quirky. Between their funny expressions and odd behaviors—like rolling in grass and tilting their heads—each of our furry friends has eccentricities that make us love them even more. But some of the adorably weird things they do are actually an innate part of being a canine, which might come as a surprise to some pet parents.

Take, for example, when dogs curl up in a ball before falling asleep. To the average pet owner, this probably just seems like a way to get comfortable before dozing off. And while that could be part of it, Dr. Margaret Gruen, an assistant professor of behavioral medicine at NC State University’s College of Veterinary Medicine, said that the behavior is also evolutionary.

“When dogs sleep in the wild, especially where it’s cold, they’ll dig a nest and curl up into it,” Gruen told Vetstreet.com in 2012. “This gives them warmth—tucking into a ball conserves body heat. It also protects their most vulnerable organs in the abdomen from would-be predators.”

Yes, she’s saying your dog gets into this position so no one comes for their organs. It sounds silly for your beloved pooch, but it’s a reasonable tactic for their wild ancestors.

The next reason makes more sense: Your dog is making their own nest when they curl up in an attempt to stay safe from external threats. Even if your dog is at home, they often revert to basic instincts when getting ready for sleep, as it’s a vulnerable state.

It turns out that there’s a whole host of reasonable explanations for your dog’s other odd behaviors; here are just a few of them.

This article originally ran in 2018; it has been updated for 2023.