The Suppression of Mounting Behaviour and Ejaculation in Male Rhesus Monkeys (Macaca Mulatta) by Administration of Progesterone to Their Female Partners

Abstract

SUMMARY Sexual behaviour was studied quantitatively by observing six pairs of oppositely sexed, adult rhesus monkeys during 209 hourly test sessions conducted over a period of 7 months; at all other times, animals were housed singly. The effect on male—female sexual interaction was studied when ovariectomized, oestrogen-treated females were given s.c. injections of progesterone. Administration of 25 mg. progesterone resulted in a highly significant decrease in male mounting activity, in ejaculation, and in the number of sexual invitations made by females. At the same time there was a highly significant increase in the number of female refusal reactions. In three pairs, mounting attempts by males remained constant and the decline in the number of mounts resulted primarily from a large increase in refusal reactions. In three other pairs, the decline in the number of mounts resulted, primarily, from a marked decrease in male mounting attempts. The two principal mechanisms, loss of female receptivity and loss of female attractiveness, previously observed during the luteal phase of the female's menstrual cycle, were thus reproduced by giving progesterone to the ovariectomized, oestrogen-treated female partners.

The Menstrual Cycle and Sexual Behaviour in a Troop of Free Ranging Chacma Baboons (Papio Ursinus)

“…Experiments with pairs of animals with ovariectomised partners, in which the sexual perform ance of the males was reduced ), de m onstrated th at replacement therapy with oestrogen restored high levels of mounting behaviour and the capacity of males to ejaculate whereas these effects were antagonised by the addition of progester one (Michael; H erbert and Saayman [1966]). Two endocrine de pendent mechanisms, m ediating changes in behaviour, were con ceptualised: (1) female sexual attractiveness (measured by the suc cess of female sexual presentations and by the num ber of mounting attem pts by the male) and (2) female sexual receptivity (measured by the num ber of female sexual presentations and by the num ber of female refusals of mounting attem pts by the male) (Michael; Saay man and Zumpe [1967 a]). The loss of female sexual attractiveness and the loss of female sexual receptivity, previously shown to he associ ated with the conspicuous decline in mounting activity during the luteal phase of the m enstrual cycle, were reproduced by the ad m inistration of subcutaneous injections of progesterone to the ovariectomised, oestrogen-treated partners (Michael;Saayman and Zumpe [1967b;1968]).…”

Changes in the Sexual Behaviour of Male Rhesus Monkeys (M. mulatta) at Puberty

“…The so cial encounters took place in special observation cages 46 in wide x 36 in high x 43 in deep, into which first the male and then the female were introduced at the beginning of each period of observation. Pairs were observed for 1 h each weekday, and throughout the 30-month period of study the frequency, duration and order of testing were kept constant [Michael et al, 1968], Recording behaviour commenced the moment the fem ale entered the cage occupied by the male and continued without interruption for the duration of the test. The scoring system described behavioural sequences during conse cutive 30-sec epochs [Michael and Saayman, 1967a, b].…”

“…Subadult males may also grip the female's legs with one foot only, the other remaining on the ground, or they may clasp the female's waist and thrust with both feet on the ground. (3) Mean number o f ejaculations per test [Michael et al, 1967], (4) Ejaculation time: time in minutes from the first mount (as defined above) until the occurrence of ejaculation [Michael and Saayman, 1968]. (5) Latent period to the first mount: time in minutes from the start of the test to the first mount by the male.…”

Psychobehavioral Effects of Hormonal Contraceptive Use

“…This research further provides experimenters with a method infrequently used in humans for ethical reasons, thereby providing valuable demonstrations of the experimental (versus correlational) effect of HCs on social behavior. HCs appear to influence sexual behavior, with reported or apparent reduced sexual functioning and interest in humans (Bancroft et al, 1987;Caruso et al, 2004;Graham et al, 1995;Sanders et al, 2001;Wallwiener et al, 2010; but see Caruso et al, 2005) and in other primates (Guy et al, 2008;Michael, Saayman, and Zumpe, 1968;Nadler, Dahl, Gould, and Collins, 1993;Shimizu, Takenoshita, Mitsunaga, and Nozaki, 1996;Steklis et al, 1982). However, human female HC use is also associated with a greater number of reported sexual partners (Little, Jones, Penton-Voak, Burt, and Perrett, 2002) and significantly greater interest in engaging in short-term sexual relationships across all phases of the menstrual cycle (Guillermo, Manlove, Gray, Zava, and Marrs, 2010), indicating that women who choose to use HCs may differ from others in their degree of sociosexuality.…”