>>27904835It's perfectly natural for a woman to have sex with an animal. Animals are capable of consenting
(the fact he mounts her and shoves it in is obviously consent) and it causes no harm to either your sister or the animal.
Intact dogs who do not have sex whatsoever are at a much higher risk of gonad-related cancers (testicular cancer is especially popular in males, and can kill your dog). Your sister might literally be saving your dog's life.
If you're genuinely curious and don't want to alert your sister, what you need to do is see if your dog is easily aroused by touching his genitals, and then getting on all fours.
If he responds, you can then confirm by tasting his dick, to see if it tastes like your sister's vaginal secretions. :^) :^) 
