Dogs may eat rocks for a variety of reasons, including boredom, a diet lacking in nutrients and compulsive eating, although this is quite rare. The act of consuming nonfood items in dogs is referred to as pica.
Consuming rocks is the most common form of pica among dogs. Most puppies engage in this type of behavior, and outgrow it as they age. However, some dogs may continue the behavior as they age, which may signal a compulsive disorder. In addition to eating rocks, pica frequently involves consumption of various inedible objects, such as plastic bags, human clothing, containers and various wooden objects. Providing the dog with play and chew toys can help resolve pica.