Primate socioecology: New insights from males

Primate males have only recently returned to the center stage of socioecolo gical research. This review surveys new studies that examine variation in t he behavior of adult males and their role in social evolution. It is shown that group size, composition, and social behavior are determined not only b y resource distribution, predation risk, and other ecological factors, but that life history traits and social factors, especially those related to se xual coercion, can have equally profound consequences for social systems. T his general point is illustrated by examining male behavior at three levels : the evolution of permanent associations between males and females, the ca uses and consequences of variation in the number of males between group-liv ing species, and the determinants of social relationships within and betwee n the sexes. Direct and indirect evidence reviewed in connection with all t hree questions indicates that the risk of infanticide has been a pervasive force in primate social evolution. Several areas are identified for future research on male life histories that should contribute to a better understa nding of male reproductive strategies and corresponding female counterstrat egies.