Question about the 5 herd roles

[Nanno]

I have the book and I looked up the chapter that deals with herd pecking order and I see "protector" (dominant male), "leader" (top female), "babysitter" (female designated by the leader), and "social director" (a male or female in the middle of the pecking order). I'm not seeing a fifth role. I usually call the guy at the back of the string "bear bait" though.