Tamed 1 and 2 stars will try to return to their spawn point. Once its tamed name it. Once you have 4 more starred boars cull all the no stars and your named boar. The boars you bred will stay where they were born and not try to go to the spawn point.

I thought I saw someone mention that they changed the harpoon for Mistlands so that it doesn't work on boars any more.