The role of males in the stimulation of reproductive function in female cotton-top tamarins, Saguinus o. oedipus

When mature female cotton-top tamarins are removed from the reproductive suppression of their mother, reproductive hormone levels and scent-marking behaviour increase, but the females do not ovulate until paired with an unfamiliar male. This study determined the effects of exposure to male urine and direct contact with both familiar and unfamiliar males on sociosexual behaviour and urinary oestrone and gonadotropin secretion in pubertal females. Seven females were observed when they resided with family members, in isolation, and after pairing with an unfamiliar male. Initially, the females were housed either in their natal group or with a familiar male(s) only. When housed in isolation, the females were exposed daily to either male urine or water. Neither urinary hormone levels nor sociosexual behaviour differed between females housed with their natal group and those housed only with familiar males. In isolation, urinary oestrone and scent marking increased, but hormonal excretion was acyclic; daily exposure to male urine did not influence hormones or behaviour. Sexual behaviour was almost never observed when females lived with family members but increased significantly after pairing. One female began ovulatory cycling in the presence of a familiar male, no female began cycling in isolation, and five females began cycling after pairing. The results from this and previous studies indicate that the onset of sexual behaviour and ovarian cyclicity may require not only release from suppression by the mother but also release from suppression by other family members as well as direct contact or stimulation from an unfamiliar male. The combination of suppressive and stimulatory factors may serve as mechanisms for avoidance of inbreeding and to promote group dispersal.