"Why Dogs Bury Bones"

This is what I found on the Net:

Essentially, dogs bury bones for the same reason squirrels bury nuts: as a hedge against the lean times. Not that the typical dog has to worry about where his next meal will come from, but his wild ancestors figured out a long time ago that when food is easy to come by, it's a good idea to put some aside --- kind of like setting up a savings account that can be drawn on in an emergency. This behavior is called"caching," and it's common among wolves and certain species of foxes as well as dogs.

http://www.ultimutt.com/bones.asp