Small Male Chimps Use Politics, Rather Than Aggression, To Lead The Pack

http://www.sciencedaily.com/releases/2009/02/090202174958.htm

ScienceDaily (Feb. 3, 2009) — With most mammals, the biggest and most aggressive male claims the alpha male role and gets his choice of food and females. But a new study from the University of Minnesota suggests that at least among chimpanzees, smaller, more mild-mannered males can also use political behavior to secure the top position.

The finding was gleaned from 10 years of observing dominant male chimpanzees in Gombe National Park, Tanzania, looking at behaviors they used to compete for alpha male status relative to their size. Analysis showed that larger males relied more on physical attacks to dominate while smaller, gentler males groomed other chimpanzees, both male and female, to gain broad support.

The study focused on three alpha males who reigned between 1989 and 2003. Frodo, one of the largest and most aggressive male chimpanzees ever observed at Gombe, weighed 51.2 kg (112.6 lbs.) at his peak. He relied on his size and aggression to rule. While he allowed other chimpanzees to groom him, he seldom returned the favor. At the other end of the spectrum, Wilkie, who weighed only 37 kg (81.4 lbs.), obsessively groomed both male and female chimpanzees to maintain his top position. And Freud, who weighed 44.8 kg (98.6 lbs.), used a combination of the two strategies. (The average male chimp in Gombe weighs about 39 kg (85.8 lbs.).

The findings are reported in the February issue of the American Journal of Primatology. While it's widely known that grooming plays an important role in chimpanzee social interaction, this study is the first to show that it can be a strategy for achieving dominance.