If I were inclined to fight over a bone, which I am not, I would probably want to know the size of the brute I’d be taking on. After all, with a really delectable and much loved bone I might be willing to take on someone my own size or smaller, but a Schwarzenegger-sized opponent might be a bit much. Makes sense to me, and apparently to dogs as well. The size of one’s opponent would be good information to have before making a decision. But animals can be amazingly deceptive about their size if it is based on sight. Pigeons come to mind. I have seen some city pigeons that look to be the size of small badgers when their feathers are fluffed. Pufferfish will puff up when threatened and appear many times larger. If you look closely at this one, he looks distinctly self-satisfied and pleased with himself. He almost appears to be smiling.
Dogs have a a pretty large repertoire of vocalizations. And a recent experiment, has shown that dogs have an uncanny ability to match the recorded sound of a growl to an image of the growler. This is an oversimplification, but basically a dog was shown two images of a dog. One image was matched to the size of the actual growling dog, while the other image was either 30% larger or 30% smaller. A speaker, with a recording of a growl which in dog language said “this here bone is MINE” was placed between the two images.
When shown the two images and the recording growl, they found that the test dogs more frequently, actually much more frequently, looked at the matching picture first and for longer periods.