Dogs bury anything they consider of value, especially bones.
Before they figured out how to earn humans’ affection, dogs spent years developing other survival skills.
As pack animals, dogs search for food as a team, but compete with the rest of their back for the spoils. Not knowing when they’d find their next meal, dogs would take the nutrient–loaded bones and bury them near the pack den, to keep other animals from stealing them. When food was scarce, they would dig up their cache of bones and feed.
Today’s domesticated pet dogs have their food served up daily, but this practice is so ingrained that dogs continue to bury bones and other favorite things.
Burying bones and toys is just a natural instinct. So one day, if you feel something strange in your bed, it could be an item your dog is saving for a rainy day.