This guide: viewtopic.php?f=42&t=54070#p717134
It's a pretty good read for those that haven't figured out the basics of the combat system yet. There is a chart down the post a bit that gives the approximate values for the different animals. Some of the rest of the post is dated, but as far as I'm aware, the animal information is still accurate. (Note: animal armor for larger animals is not included as that was just added this world.)