A four-year study of the association between male dominance rank, residency status, and reproductive activity in rhesus macaques (Macaca mulatta)

Considerable controversy exists on the nature of the relationship between m ale dominance rank and reproductive activity. The nature of this relationsh ip has important implications for understanding the manner in which males c ompete for access to limited resources. Behavioral data on mating patterns were collected over a four-year period from one social group of rhesus maca ques on Cayo Santiago. Correlations between dominance rank and reproductive activity were not stable over a four-year period, but changed yearly. Posi tive, significant correlations were present in the first two years of the s tudy while non-significant correlations were found in the second two years. The variation found in the correlations between rank and mating activity c ould be accounted for by changes in the mating frequencies of different cla sses of males. The long-term resident males had declines in ejaculation fre quencies over the duration of the study. Males who immigrated into the grou p had yearly increases in reproductive behavior over three consecutive year s. Maturing natal males also increased their levels of reproductive activit y from year-to-year. Combining these mating patterns over time resulted in shifting the proportions of matings away from the long-term residents and i n favor of the new males. High-ranking males had an advantage in reproducti ve activity over the first two years of the study, as measured by both the total number of ejaculations and the mean number of ejaculation per male. N ew males, comprised of recent immigrants and maturing natal males, had a gr eater level of reproductive activity over the last two years. These results suggest that the effect of rank on reproductive activity is variable and t hat males utilize alternative tactics to attain access to limited resources . Simple one-factor models explaining the relationship between rank and rep roductive activity must be replaced with models explaining how alternate st rategies affect male competition and reproductive success in primates.