Our 4 mth old Shih Tzu normally sleeps in the bedroom with us. We bring him out for his last bathroom break around 11pm and he's never soiled it until last night. We woke up to find him barfng some brown liquid that smelled absolutely putrid! My husband figured out he pooped and then ate it. Why Why Why? What would possess him to do this? Is it normal? What can we do so he doesn't do this again?