That was my first thought too, but I wondered if they were too big for that? Also, the rat poo I've seen before was much darker in colour.
Quite possibly rat, but could also be squirrel. They look very similar, but you can usually tell by the smell. If you look carefully, there appear to be long grey hairs attached to some of them (squirrel tail hair?) Hard to tell without more context, but it is definitely one of the two..
Awesome series of posts and pictures, thank you for educating me