A comparative diagram of deer butts. From Life-histories of Northern Animals: An Account of the Mammals of Manitoba by Ernest Thompson Seton

I. white tailed deer (Odocoileus virginianus)
II. mule deer (Odocoileus hemionus)
III. black tailed deer (Odocoileus hemionus columbianus)
IV. elk (Cervus candanensis)
V. red deer (Cervus elaphus)

Oh, hey, excuse me sir. You may not believe this, but I didn’t even see you standing there when I stopped here. I saw a Blue-grey Gnat catcher dart down into the weeds in that ditch right there between us. No, really, I’m serious. Did you see it? Know which way it went? No? Ok, thanks anyway. I’ll just move along now, thanks for the photo. It’ll be on tumblr, tell all your friends.