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SUMMARY
Male and female sexual behaviour was studied quantitatively by observing pairs of oppositely sexed, adult rhesus monkeys during regular hourly test sessions over 2 yr.; at all other times the animals were housed singly. Rhythmic fluctuations in the sexual invitations of both males and females, and in the refusal reactions of females, occurred in relation to the menstrual cycle. A decline in male mounting activity occurred during the luteal phase of the cycle, and resulted from two principal types of change in male—female interaction: in one, males stopped making mounting attempts, although females continued inviting (loss of female attractiveness), and in the other, males continued to attempt to mount, but females stopped inviting and began refusing (loss of female receptivity). Bilateral ovariectomy of females abolished all rhythmic variations, and the behavioural interactions were reduced to low levels; these were restored by subcutaneous injections of oestradiol into the females. These findings indicate that sexual invitations in a female primate are mediated by ovarian hormones, and that the changes in male—female interaction during the menstrual cycle can be understood in terms of endocrine-dependent changes in sexual invitations and their outcome.
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Search for other papers by J. WELEGALLA in
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SUMMARY
Grooming behaviour was studied quantitatively by observing pairs of oppositely sexed, adult rhesus monkeys during regular hourly test sessions over 2 yr.; at all other times the animals were caged singly. Rhythmic fluctuations in both male and female grooming occurred in relation to the menstrual cycle; the grooming times of males reached a maximum near mid-cycle, at which time the females' grooming was at a minimum. In some pairs, there were additional changes in the grooming times immediately before menstruation in the same direction as those near mid-cycle. Bilateral ovariectomy of the female of the pair abolished all rhythmic variations and reduced the grooming of the males. Subcutaneous injections of oestradiol into the ovariectomized female restored the grooming of males to the levels seen near mid-cycle. The subsequent addition of progesterone partially, but always consistently, antagonized the effects of oestradiol. Analysis of the hormone-induced alterations in grooming behaviour indicates a primary influence on the effectiveness of the grooming invitations of females, the proportion accepted by males increasing with oestradiol administration. These findings indicate that endocrine factors play a role in regulating grooming activity which constitutes an important aspect of the social behaviour of primates.
Search for other papers by R. P. MICHAEL in
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Search for other papers by JUDY WELEGALLA in
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SUMMARY
Male sexual behaviour was studied quantitatively by observing pairs of oppositely sexed, adult rhesus monkeys during regular hourly test sessions over 2 yr.; at all other times the animals were housed singly. Rhythmic fluctuations in the mounting behaviour of males occurred in relation to the menstrual cycles of female partners. Two patterns were seen: those with high and low levels of mounting, respectively, in follicular and luteal phases, and those with more isolated maxima near mid-cycle. Ejaculation times were shortest and mounting rates highest near ovulation. Bilateral ovariectomy of females abolished all rhythmic variations in the behaviour of the males, which also stopped ejaculating. Subcutaneous injections of oestradiol into ovariectomized females restored the sexual performance of males, an effect which was partly antagonized by the subsequent addition of progesterone. These findings indicate that sexual behaviour in a male primate is influenced, in some way, by the secretory activity of the female's ovaries.
