Costs and Benefits of Alternative Mating Strategies in Samango Monkey Males

In samango monkeys (Cercopithecus mitis labiatus), males compete for residency in unimale troops where they defend females against other males, although extratroop males may sneak copulations with females opportunistically. Here, we attempt to determine whether these are alternative strategies yielding equivalent lifetime reproductive success, or whether the extratroop male component is simply a tactic followed by males who are unable to follow the resident troop male strategy because of their age or physical condition. Observations of mating success and male-male competition support the latter of these hypotheses. Modeling the expected reproductive success of males following the different strategies suggests that dedicated extratroop males in this population would not be able to live for long enough to compensate for their extremely low rate of mating success compared with males achieving troop residency. However, other studies of Cercopithecus mitis have revealed a much higher proportion of mating by extratroop males, and it is suggested that ecological and demographic factors may affect the costs and benefits of these two male strategies.