Gorillas are the largest-bodied primates living today. Adult male gorillas are called silverbacks, due to the silvery hair that develops across their backs with maturity. Silverbacks in the wild stand 5½ - 6 feet tall when on two legs and weigh more than 350 lbs. Female gorillas are considerably smaller – only about half the size of males. Gorillas typically form polygynous groups, including a dominant silverback and several females with offspring. Because the sex ratio at birth is 50:50, this leaves a lot of males without a group of females. Sometimes males form bachelor groups, loose associations of young males who travel and feed together until each male is able to take over a group of females. In some areas, researchers have documented groups with two silverbacks. In these cases, an adult son of the dominant male remains in the group to help protect it against take-overs by unrelated males.
Dr. Sylvia Amsler is a lecturer in anthropology at the University of Arkansas at Little Rock.