Influences of sexual and social stimuli upon circulating levels of testosterone in male pigtail macaques

Circulating testosterone concentrations of adult male pigtail macaques (Macaca nemestrina) were assessed in three social conditions: (1) subjects housed in a stable heterosexual group (continuous contact with females); (2) subjects housed in an all-male group (no contact with females); and (3) subjects housed in a newly established heterosexual group (female presence as novel stimulus). Pigtail males living continuously with females throughout the year did not exhibit seasonal cyclicity in testosterone values and maintained mean levels equivalent to those observed in the rhesus monkey during the breeding season. Members of all-male groups had mean testosterone concentrations equivalent to males living with females, but these values rose significantly following the addition of females to the group.