Mate guarding and paternity in mandrills : factors influencing alpha male monopoly.

Abstract

We used long-term data on mate guarding and paternity in mandrills, Mandrillus sphinx, (1) to examine cycle day and cycle selection by males; (2) to examine associations between male rank, periovulatory mate guarding and paternity outcome; (3) to test the predictions of the priority-of-access model; and (4) to investigate factors influencing the ability of alpha males to monopolize females. Males mate-guarded on periovulatory days more than on other receptive days, and during conceptive cycles more than during nonconceptive cycles. Both periovulatory mate guarding and paternity outcome correlated significantly with male rank. Alpha males accounted for 94% of periovulatory mate guarding and 69% of paternity, confirming the existence of extremely high reproductive skew in this highly sexually dimorphic species. The fit of the observed distributions of mate guarding and paternity to predictions from the priority-of-access model was good, but in both cases the alpha males accounted for a greater proportion of reproduction than predicted. Mate guarding was a good predictor of paternity, but consistently overestimated the reproductive success of the alpha male. Splitting data into group-years revealed that the percentage of mate guarding by the alpha male decreased with increasing numbers of adult males, and the percentage of paternity decreased with increasing numbers of reproductive males (all postpubertal males). Furthermore, mate guarding became less effective as the number of reproductive males increased. We attribute this to the fact that only males aged 8 years or more mate-guarded, but that all males aged at least 3.8 years may sneak copulations, reducing the effectiveness of mate guarding and therefore reducing paternity concentration in the alpha male.