I also love animals, and have won multiple awards for marksmanship (shotgun and rifle- not yet bow), and I never aim for the head (except for turkeys). I know exactly where the heart is, so I can guarantee a clean kill with a shot there. When they run after that, they're already dead. their muscles are still just reacting (my hunting guide told me that, and seems true enough), I feel confident with taking a head shot and killing it, I just go for the traditional heart shot that I was taught as a young hunter.