My Lab caught a big old male squirrel. It chewed her up a bit before she was able to kill it. She had a couple of bite wounds on her nose. She didn't yelp or squeal - she gave a low moan, like a human in pain, and then gave Mr. Squirrel a good hard shake that finished him off.
No stitches needed, but she was on antibiotics for a week. Apparently squirrels' mouths are totally filthy.