Posted by Stephanie Payne-Jacobs, gorilla keeper EDITOR'S NOTE: Adult male gorillas are known as silverbacks because of the striking silver hair that grows across their back all the way down to their hips. This is not only a mark of maturity (silver hairs appear around 12 years-old), but a sign that one might be strong and determined enough to protect his troop. In most gorilla troops, the silverback is the center of attention. He is responsible for guarding the troop against outsiders, finding choice feeding sites and playing mediator between the other gorillas in the group. While silver hairs, larger canines and handsome red crowns (in Western lowland gorillas) are all visual characteristics of a mighty silverback, it is the personality and behavior of these males that determine if they will lead. This is the story of how one such silverback, Leonel, has come into his own as a protector, leader and peacekeeper — in part with a little help from a tiny, adorable baby called Yo