Search Results
You are looking at 1 - 10 of 17 items for
- Author: R. P. MICHAEL x
- Refine by access: All content x
Search for other papers by R. P. MICHAEL in
Google Scholar
PubMed
Search for other papers by G. S. SAAYMAN in
Google Scholar
PubMed
SUMMARY
The behavioural interactions between pairs of oppositely sexed, adult rhesus monkeys were studied during 1307 mating tests, each of 1 hr. duration. Females were ovariectomized and the effects of administering oestrogen subcutaneously, intravaginally, and directly to the sexual skin at different daily dose rates were compared. The subcutaneous route resulted in a greater enhancement of the overall sexual activity of the pair, and in a greater stimulation of the females' sexual invitations. In contrast, the intravaginal route of administration resulted in a greater stimulation of the males' sexual interest and of the males' mounting attempts: this occurred without a corresponding increase in female sexual receptivity and, in two pairs, resulted in increased aggression. It is concluded that communication between these primates was influenced by oestrogen-dependent changes in the vagina, and the findings point to the existence of a substance with a pheromone-like action.
Search for other papers by R. P. MICHAEL in
Google Scholar
PubMed
Search for other papers by J. WELEGALLA in
Google Scholar
PubMed
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.
Search for other papers by R. P. MICHAEL in
Google Scholar
PubMed
Search for other papers by C. WELLER in
Google Scholar
PubMed
Telemetry offers special advantages for recording electromyographic changes in the uterus of rhesus monkeys, and this technique has been successfully employed to study animals moving freely and interacting with others in our colony. The transmitter used was of the F.M./F.M. type, with a carrier frequency of approximately 100 MHz. A three-stage pre-amplifier gives a gain of 400; the transistors are operated at low collector currents to give a high input resistance and low-power consumption. Negative feedback over each stage increases the input resistance still further and ensures stability and low distortion. The frequency response is flat from 0·5 Hz to 4 kHz and the noise level over this frequency band is below 5 μv (source resistance 10 kΩ the input resistance is > 1 MΩ The subcarrier oscillator is a multivibrator of centre frequency 6·5 kHz. This circuit gives good linearity, has a high input impedance and low power consumption;
Search for other papers by E. B. KEVERNE in
Google Scholar
PubMed
Search for other papers by R. P. MICHAEL in
Google Scholar
PubMed
SUMMARY
Vaginal secretions were collected by lavage from ovariectomized, oestrogen-treated female rhesus monkeys. Ether extracts of these secretions were applied to the sexual skin of long-ovariectomized, untreated females immediately before mating tests with males. Application of extracts resulted in an immediate and marked stimulation of the sexual activity of males which had been inactive with these females during pretreatment tests when control material was applied. Extracts caused increases in male mounting activity, in ejaculations and in male grooming times, in the apparent absence of any behavioural or genital tract signs of female receptivity. It is concluded from these and other observations that male sex-attractant pheromones, with powerful behavioural effects, are present in ether extracts of oestrogen-stimulated vaginal secretions: this will facilitate their chemical characterization.
Search for other papers by DORIS ZUMPE in
Google Scholar
PubMed
Search for other papers by R. P. MICHAEL in
Google Scholar
PubMed
SUMMARY
A description is given of the turning round, looking backwards, lipsmacking, clutching and biting behaviour of the female rhesus monkey that occurs during the ejaculatory mount of the male: this behavioural sequence has been designated the clutching reaction. It was observed during almost all ejaculations in intact females, but the incidence decreased after bilateral ovariectomy. Oestrogen administration to ovariectomized females restored it to the levels in intact females and progesterone administration diminished it to levels lower than those in any other condition. It is suggested that this behavioural reaction is an external expression of consummatory sexual behaviour in the female rhesus monkey, and its homology with orgasm in the human female is discussed.
Search for other papers by R. P. Michael in
Google Scholar
PubMed
Search for other papers by Doris Zumpe in
Google Scholar
PubMed
Olfactory influences are important in the control of reproductive function in many mammalian species including primates. Previous studies have shown that a mixture of volatile aliphatic acids (copulins), normally present in the vaginal secretions of rhesus monkeys, can exert a stimulatory effect on the sexual behaviour of males when pairs are tested in small cages. The present study deals with the role of these substances when tested in social groups of rhesus monkeys housed in a large testing arena, the purpose being to assess the effectiveness of olfactory signals under more nearly naturalistic conditions. Each group consisted of one male with four long-term ovariectomized females from which the male could choose. A counter-balanced experimental design was used in which each female of a testosterone-treated pair was given applications to the sexual skin of either copulins or control ether immediately before each 1-h behaviour test. After 16 tests, the procedure was repeated with the previously untreated pair in each group, and nine groups were separately studied. Testosterone was used here simply to enhance female proceptivity. The results showed that females received significantly more ejaculations (P <0·05). mounting attempts (P <0·01) and mounts (P <0·05) when bearing copulins than when bearing control ether. There were positive responses to copulins in 12 of the 36 male–female pairs, involving all males, and positive responses to ether in five of 36 pairs, involving four males. Copulins resulted in a change in the choice of sexual partner in five males, but there were no changes in the choice of partner with ether. Social factors, such as dominance, could override the responses to olfactory signals, and there was a significant treatment order effect, but this was eliminated by the counter-balanced design. These findings indicate a significant role for olfactory communication in mate selection in a socially living higher primate.
Search for other papers by E. B. KEVERNE in
Google Scholar
PubMed
Search for other papers by R. P. MICHAEL in
Google Scholar
PubMed
The occurrence of menstruation in female rhesus monkeys is difficult to assess reliably under field conditions, but quantitative data obtained in the laboratory (Hartman, 1932) have indicated that menstruation in this species is infrequent and irregular during the summer months; similar views have been expressed by others (van Wagenen, 1945; Corner, 1945; Kerber & Reese, 1969). However, Rowell (1963) found scant evidence of a summer period of amenorrhoea but reported that cycles were shorter in winter than in summer. Data on changes in the menstrual rhythm throughout the year tend to be confused by the interruptions caused by pregnancy and lactation, and we report here on annual changes in the occurrence of menstrual bleeding in female rhesus monkeys whose Fallopian tubes were ligated to prevent pregnancy.
Thirty adult female rhesus monkeys (body wt 5·0–8·3 kg) were obtained from northern India and studied over a 6-yr period between May 1964 and
Search for other papers by R. P. MICHAEL in
Google Scholar
PubMed
Search for other papers by J. HERBERT in
Google Scholar
PubMed
Search for other papers by JUDY WELEGALLA in
Google Scholar
PubMed
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.
Search for other papers by R. P. MICHAEL in
Google Scholar
PubMed
Search for other papers by J. HERBERT in
Google Scholar
PubMed
Search for other papers by J. WELEGALLA in
Google Scholar
PubMed
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
Google Scholar
PubMed
Search for other papers by K. D. R. SETCHELL in
Google Scholar
PubMed
Search for other papers by T. M. PLANT in
Google Scholar
PubMed
SUMMARY
The assays of testosterone and corticosteroids in plasma from adult male rhesus monkeys using competitive protein-binding and radioimmunoassay techniques are described. The radioimmunoassay for testosterone was conducted without chromatography and, therefore, additionally estimated 17β-hydroxy-5α-androstan-3-one (dihydrotestosterone). Levels of testosterone in the peripheral plasma of 14 intact male rhesus monkeys showed marked fluctuations over a period of 24 h. Concentrations of testosterone at 22.00 h (1776 ± 814 ( ± s.d.) ng/100 ml) were approximately double those at 08.00 h (858 ± 407 ng/100 ml), 12.00 h (898 ± 316 ng/100 ml) and 16.00 h (784 ± 530 ng/100 ml). Castration resulted in low plasma testosterone levels (85 ± 29 ng/100 ml), and the increases at 22.00 h were no longer observed. In intact males, the 'basal' plasma corticosteroidlevel(08.00 h) was 22·4 ± 6·0 μg/100 ml. Administration of synthetic corticotrophin raised plasma corticosteroid levels without changing plasma testosterone concentration. Because plasma testosterone levels were not related to changes in adrenocortical activity, the noctural rises appear to be due to changes in testicular secretion.
