Dogs spend a lot of their time sleeping, normally around 12–13 hours a day on average. Naturally, the interval can be even longer in very young or older pets. During these periods of rest, they sleep sideways, on their bellies, and their backs.

Why they sleep on their backs is uncertain.  Some believe they do it because they want more attention and petting from their owners. Many pets also lie on their back to show submissiveness to their owners. However, it has been proven many times that pets lie on their backs to help their bodies cool off more easily. Because a dog’s belly has less hair, it is easier to cool off when exposed to the open air and airflow. 

Pets that try sleeping on their back also ensure that most of their muscles are relaxed more, which in turn helps them rest and relax fully. It has been proven that this sleeping position is used only when the pet feels completely at ease, when it is in a familiar and safe place, surrounded by people it knows and trusts, their “human family”. Therefore, this position is almost never observed in dogs that roam freely, as they need to be on their guard at all times. In such cases, animals tend to choose positions that limit the exposure of their sensitive body parts to potential attackers and predators, which include their necks, bellies and rib cage.