Burying bones or other treats is an example of the dog's instinctive tendency to hoard food for later consumption. Dogs living in the wild and fending for themselves would sometimes take down large prey and hide part of the carcass somewhere that other animals would be unlikely to find it. This allowed the dogs to dig it up later when they were hungry again.
Although most dogs do not have a practical need for food hoarding, many of them still retain the instinctive drive to do it. Dogs on carefully portioned diets often hide toys instead of food treats. Some may even hoard their owners' belongings.
Despite the traditional image of dogs burying their bones in the dirt, many dogs use a more subtle form of hiding. Hiding toys or treats in bedding or piles of laundry is a common behavior. Some may just put things behind or under furniture. All of these behaviors stem from the same instinctive urge to save desirable things for later.
Some of this hoarding behavior may stem from boredom. Digging is a fun activity for dogs, but a tired dog is less likely to engage in it. Dogs who have an excess of food are more likely to hoard it, so avoiding free-feeding and only giving treats occasionally can help prevent hoarding. Although toy hoarding is fairly safe, buried food can decay and cause illness when eaten