Why Do Dogs Bury Their Food? 

Ancient dogs survived on whatever they could find or catch. If they managed to get more than they could eat in a sitting, they had to make sure it would be there when they came back to it later. "They stored spare food by burying it," says Benjamin Hart, D.V.M., Ph.D., professor of physiology and behavior at the University of California School of Veterinary Medicine at Davis. "It was a pretty resourceful way of keeping leftovers." Dirt may be gritty and hard on the teeth, but it is also protective. 

The temperature in the ground is cooler than it is in the air, so burying food helped it stay fresh longer. Buried food did not roast in the sun. It did not immediately get covered with flies and insect. All in all, burying food and juicy bones was a very good solution.

Dogs do not need to bury their food anymore. But when they have an excess of rations, they feel that old urge coming on. So they look for a secluded spot, dig a quick hole, and put some goodies away for a rainy day...