Dominance, access to females, and mating success among coresident male mantled howlers (Alouatta palliata) at La Pacifica, Costa Rica.

The priority-of-access (POA) model posits that high dominance rank increases male mating success by increasing access to fertile females. However, the relationship between rank, access to females, and subsequent mating success is variable in primates, and there are few studies representing Neotropical taxa. The purpose here was to test the parameters of the POA model in an asynchronously breeding Neotropical primate, Alouatta palliata, to contribute to our understanding of the relationship between dominance and reproductive strategies in platyrrhines. I collected data on adult males within two large, multimale-multifemale groups exhibiting clear dominance hierarchies at La Pacifica, Costa Rica. Females were classified as sexually receptive (SR) or potentially cycling (PC) based on behavioral and birth data. Access to mates was measured based on total time in proximity to SR/PC females, and mating success was measured based on copulation frequency. Results did not support the predictions of the POA model in that first-ranked males maintained lower than expected time in proximity to SR females, did not consistently maintain the greatest proportion of time in proximity to PC females, obtained lower than expected copulation rates, and did not obtain the highest copulation rates compared to subordinates in either group. Deviations from the POA model were significantly affected by varying operational sex ratios only when considering the lower numbers of available SR females in one group. Alternative reproductive tactics by subordinate males such as tolerance by first-ranked males appeared to be operating, allowing subordinates to obtain mating success when they would otherwise be unable to do so. The study also highlighted how factors such as operational sex ratio may limit the willingness or ability of dominant males to monopolize access to females, and can vary both within and between groups in a population.