Balance of investment between parental care and mating effort in male baboons

Non-monogamous males that provide care to their offspring face a potential conflict in investment between paternal care and mating effort. This conflict arises either because of resource or temporal constraints. I investigated potential conflict between paternal care and mating effort among adult male baboons that are part of a wild population in the Amboseli basin, southern Kenya. Specifically, I determined whether the number of a male's immature offspring (1) is correlated with the male's intensity of paternal care, (2) constrains the male's mating effort, (3) constrains the male's intensity of mate guarding, (4) is correlated with the male's concentrations of testosterone, and (5) influences the male's dispersal decisions.;I used demographic, behavioral, and ecological data, records of genetic paternity assignments, and non-invasively derived concentrations of the male reproductive hormone, testosterone (T). First, I demonstrate that the number of immature offspring a male has in the group is indicative of the male's opportunity for paternal care. In addition, I show that mating effort was higher among high-ranking males than in low-ranking males, and higher during the wet than during the dry season. However, I did not find evidence that opportunities for paternal care constrain mating effort presumably due to differences in male body condition. Second, I show that season and female reproductive quality predict male mating effort within episodes of mate guarding. These results suggest that energetic constraints shape the evolution of reproductive behaviors in male baboons.;Third, I show that males experiencing high mating success had high concentrations of T, which is consistent with the stimulatory role of T on male mating behavior and sexual activity. I also found that older males had low concentrations of T than younger adults. This gerontological pattern of T has been reported for other species of primates including humans. In addition, I show that concentrations of T during the wet season were higher than those during the dry season. The positive correlation between mating effort and T together with the absence of a significant correlation between opportunities for paternal care and T suggest a potential decoupling between mechanisms for the secretion of T and those for the expression of care behavior. Lastly, I show that high-ranking males, old males, and males experiencing high mating success are less likely to disperse. In contrast, I did not find evidence that opportunity for paternal care influence male dispersal decisions. Overall, I have demonstrated that investment in mating effort and investment in offspring care are influenced by opportunities for each, and are under extrinsic energetic constraints.