I've hit a ton of gophers over the years and most of them didn't survive the impact. I hit a muskrat last year with my fixed gear riding home at night. I was kinda drunk, didn't see him, and rolled right across the back of his neck. I think that's the biggest animal I've ever killed with a bicycle. I also nearly hit a deer one night biking home, I missed him (he was nice sized buck) by about an inch and a half. Just a guess, but I think he would have fared better than me.