In general the dead-humans turn in to Zombies by a virus that make their bodies “return in life” but it’s not a really resurrection and the brain doesn’t work well. In the fantasy stories the dead-zombies remains just with some basic instincts, just one actually: eat. They feed also animals but in general the stories are placed in the cities and they find first people. Maybe the virus is not transmissible to other animals. I remembered that in the game of Resident evil there was big rat-zombies… then I am not sure. I can be wrong but that is what I think.

they are like non-veg animals, they body systems runs on flash and blood, they can feed by animal flash also, but they loves to eat human flash bcz it gives them more taste and pleasure (its like you can get any whiskey but if you will get chance then you will like to have high quality whiskey in-stead-off low quality .. ;)

Because if they don't, they will not be called Zombies. It is by definition. Just like a Square has equal sides. we cannot ask why does a square has equal sides :)

I don't know man. Being vegetarian doesn't make us less human in the end.