Why does my dog walk in a circle before lying down?

Circling their sleeping place is one of the many “wild” habits that canines never evolved away from. In the wild, dogs would circle a grassy area to trample down grass and make a comfortable surface to lie on. Circling is also how dogs mark their territory, so it is possible they are also staking claim to the surface upon which they are going to lie down. Some dogs will dig at the surface they are going to lie on. Again, this is a method of making the area more comfortable.