They look young so I don't think it's the drake at this point but either or both of the pig and goat. If the pig he may keep on till he eats her completely[I read pigs will eat anything] so your doing right by getting both of them away from them. I really don't think you would need to keep the 2 ducks separate yet but be mindful of what Amiga said the drakes can be over powering once hormones begin to flow, If mom would allow it maybe consider getting a couple more females to go with these 2.