We have a blue heeler about 12 years old and we can't break her of any bad habits she had to go live at my grampas farm because all he has is Percheron drafts and she can't hurt them. She is a tire biter and chases the trucks everywhere she h learned to mind my grampa because she learned he doesn't play around plus she's protevtive she doesn't like anyone she didn't grow up around. She has gotten hit by dirt bikes, atvs, gators and snowmobiles she never quits she gets hit and goes right back for more shes gotten hit roughly 12 times By trucks once she broke herr jaw and wa back it 2 days later shes gotten kicked by cows and horses and porcupine quills and skunks. Anything animal related she learned about the fort or second time.