Scientists are increasingly seeing personality as a key factor in an animal’s ability to survive, adapt, and thrive in its environment. But this topic isn’t an easy one to study scientifically, says primatologist Dorothy Cheney of the University of Pennsylvania. “Research in mammals, birds, fish, and insects shows individual patterns of behavior that can’t be easily explained. But the many studies of personality are based on human traits like conscientiousness, agreeableness, or neuroticism. It isn’t clear how to apply those traits to animals,” Cheney says. 

Along with a group of scientists—including co-authors Robert Seyfarth, also at the University of Pennsylvania, and primatologist Joan Silk of Arizona State University, Tempe—Cheney has studied wild baboons at the Moremi Game Reserve in Botswana for almost 20 years. Besides providing detailed, long-term observations of behavior in several generations of baboons, the research has yielded a wealth of biological and genetic information.

In previously published research, Cheney and co-workers showed that females lived longer, had lower stress hormone levels, and had more surviving offspring when they had close, long-lasting relationships with other females (characterized chiefly by spending time together and grooming). Although dominance rank was significant for male baboons—alpha male baboons may live longer than lower-ranking males—this wasn’t true for the females. Nor was an abundance of kin the key to longevity. Not all of the longer-lived, less-stressed females had large families.