Most critters have really tough hide & contrary to what one may think, bicycle spokes will not slice thru it. Catch a critter in your wheel & you are going down. So best to avoid them for your own sake as well as theirs.
I've noticed that especially in springtime squirrels seem to play a game of "how close to the bike can we get" that's a bit unnerving. One theory is that they are young males out to prove themselves. The will sit up, on the side of the road as you approach, and dart out across the road. I had one try it, thinking I was going to hit him, I braked hard, he stopped, then darted behind my front wheel, only to get hit by the rear. A rider some ways behind me reported that he did continue across the road, but seemed a bit the worse for the contact.
dougP