User blog comment:Zathronas/Speculative author: Where are the Grimm?/@comment-78.42.186.25-20140913152032/@comment-24218038-20140914122020

We just don't know. from what we've seen as of this blog, they seem to react on instinct. I've been twisting myself to find ways to make the Grimm dangerous because Monty has made a pretty good job at showing them as mostly inoffensive.