Last night I watched the 4K Remastered Edition of The Good, the Bad, and the Ugly. What a great movie!
Now I noticed something I'm curious about. There are several (at least 3, maybe 4) appearances of dogs in the movie. What does Leone want to say with the wild dogs? I think it's too easy to say the dogs stands for something like freedom or to try to illustrate the empty desert better. The pictures are the first and the last appearance of dogs in the movie.
Maybe the last dog is important to answer the question. It looks like the dog wants to run to Tuco but he scares the dog, so it runs out of the picture.
On youtube you can find the whole movie if you have to rewatch it ;-)