Yes, it is quite normal for males to roll each other up. They have pretty much decided who is the dominant hog by that stage – the less dominant one just rolls up. If they aren’t quite sure, sometimes the one being pushed along tries to resist a bit i.e. doesn’t actually roll up but ‘digs his feet in’. But mostly they seem to know their place pretty well and the submissive one rolls up.
The more submissive ones probably just hope there aren’t any other males around when they meet a female! Which is quite possible as hogs are normally solitary animals. Humans are probably the cause of them meeting up more often than they otherwise would by creating feeding areas, where they might be likely to congregate a bit.
