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It is normal for piggies to reestablish their relationship and hierarchy when they move to a new environment. This takes around two weeks and while it is just normal dominance you just need to let them get on with it. Normal dominance is chasing and mounting and is not concerning.
Squealing from the submissive pig is very normal and is the correct response. It is called submission.
Their interactions can look rather rough to us but are normal to them
Bullying is a sustained set of behaviours and is so much more than dominance. It is relentless to the point where the submissive is never allowed to rest, loses weight through not being allowed to eat enough hay, is constantly chased and mounted. This either ends with the submissive becoming so withdrawn and depressed or has enough and physically fights back. Bullying is permanently bond breaking.
You need to ensure the cage is big enough (180x60cm or a 5x2 c&c cage), that there is enough resources and that all hides have two doors in them. Scatter hay and veg around the cage. Otherwise, for now, you do nothing. They have to sort things out between them and you cannot intervene unless a fight breaks out. I’d you interrupt their normal processes then you interrupt their bond and actually separating unnecessarily can do more harm than good.
You are going to see a lot of dominance once they hit their hormonal teens which is between the ages of 4 and 14 months. Even in compatible pairs it is normal.
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