Perineal swellings: A social and endocrine advantage for Barbary macaque females (Macaca sylvanus)

This study focuses the relationship between social rank, intersexual behavi or, age, fecal cortisol equivalent excretion rates and perineal swelling si ze in contraceptive- treated Macaca sylvanus females. Behavioral data and f ecal samples were collected during a twenty-week period from 24 females. Fe males were categorized with regard to perineal swelling (enlarged or reduce d), and to their dominance rank (high or low); we found that swelling size was not associated with it. However females with an enlarged perineum recei ved more male grooming interactions, had closer spatial relations to males, and received significantly more interventions from males than did the othe rs. Endocrinologically, females with enlarged swelling showed decreased fec al cortisol equivalent excretion rates. Multiple regression models showed a positive relationship between the extent of the swelling size and grooming , inspection and spatial relation. There was a negative relationship betwee n the extent of swelling size and fecal cortisol equivalents. These results imply that enlarged perineal swellings among implanted Barbary macaque fem ales have a greater impact on intersexual contact and adrenocortical activi ty than does social rank or age.