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Abstract
Sexual behavior has been described as the outcome of cyclic fluctuations of reproductive steroids (Baum, 1983; Baum, et al., 1977; Beach, 1976; Michael, et al., 1972) and or social relationships (Bernstein, et al., 1983; Wallen & Winston, 1984). The social biology of a given species may determine the extent to which either of these factors influence social and sexual behaviors. The purpose of this study was to investigate the impact of relationship quality, number of exposures, and the female reproductive cycle on sociosexual interactions in a monogamous primate, the golden lion tamarin (Kleiman, 1977a; Smuts, et al., 1987). Sociosexual behavior in this species typically occurs within the context of a long term social relationship. Therefore, the patterning of sociosexual behavior, and its modulation by hormones, may be affected by the quality of the relationship.
Four females and six males served as subjects. The quality of the social relationship was manipulated by conducting 90 standard "pair tests" (Michael & Bonsall, 1977; Wallen, 1982) with heterosexual pairs in three conditions: Unfamiliar (partners were systematically rotated), Permanent (pairs were constant), and Cohabitation (pairs were constant and housed in adjacent cages). Radioimmunoassay of excreted estrogen (French & Stribley, 1985; 1987) was used to monitor the female reproductive cycle.
The most influential factor regulating sociosexual behaviors between males and females was the quality of the relationship. All sociosexual behaviors were found to increase in the Cohabitation condition. Sexual interactions occurred significantly more often in the Cohabitation condition. Sociosexual interactions were not influenced by the number of encounters between pairs. Male mounts were highest during the Pre-ovulatory and Peri-ovulatory phases of the female reproductive cycle and decreased sharply in the Post-ovulatory phase. These patterns of behavior were consistent with hormonal modulation of male sexual behavior and the behavioral mechanism by which the female cycle was communicated, in the absence of a pair bond, was identified.
