Board Thread:General Discussion/@comment-3257939-20140521172812/@comment-3146930-20140523025348

Except Grimm aren't animals. Pyrrha mentions that every living thing has a soul, so in theory this would include animals as well and what makes Grimm the enemy of mankind isn't their lack of soul, but their destructive nature (lacking a soul just means you can kill them without feeling bad) (Pyrrha also calls them the "manifestation of anonymity," meaning that Grimm may not be alive at all and simply exist by some means outside what we see as a life cycle; sort of like how monsters in the Percy Jackson and the Olympians series never really die, but when killed their essence reforms after a certain amount of time). However in every area we have seen the Grimm inhabit, normal animals like birds or deer are mysteriously absent, as if the Grimm forced all other living creatures in the area out or the more Grimm possibility that they killed all the other animals (or the animators were lazy).

But once again, this is a different conversation and I'm trying my best to keep things on topic here.