Separation anxiety is a complex issue. It can happen to any dog and Staffy's are particularly prone to it as they love being with people. He has come from a home where there was somebody always with him. When I got him, I'd generally be out for a few hours of a morning and thought no more of it. When I got my pet cam (Just to keep an eye on him) I noticed that he was pissing in the livingroom, despite being house trained, whenever I was out for more than an hour or so. He then started howling as well in my absence. That's separation anxiety where they basically go into a blind panic. Thankfully, it only seems to be a mild case. Some dogs will literally claw their way through doors thinking that they can escape in order to find you☹️.