Female Mounting Research Articles

Male–Female and Female–Female Mounting in Japanese Macaques: A Comparative Study of Posture and Movement

Mounting is generally considered to be a male-typical behavior. Female Japanese macaques, in certain populations, are unusual, in that they routinely mount other females. In this study, we examined to what extent female Japanese macaques mount same-sex partners in a male-typical manner. We compared the mount postures males and females adopt and their rate of pelvic thrusting. In addition, we employed a modified form of Laban Movement Analysis (LMA) to compare patterns of pelvic movement during mounts. LMA is a universal language for movement that describes quantitative features of movement, such as changes in the relation of the body segments, as well as qualitative features, such as the style of movements. Our results indicate that female Japanese macaques do not mount in a male-typical manner. Females exhibited a much greater variety of mount postures than did males. Some of the most common types of mount postures employed by females were never exhibited by males. Females performed fewer pelvic thrusts per mount than males, but they executed more pelvic movements per mount, as well as, greater variety and complexity of movement. In addition, the qualitative style of pelvic mounting that females employed differed, in general, from that of males. We argue that these sex differences in mounting can be explained by the fact that both sexes sought sexual reward via genital stimulation during mounting, but they did so in different ways owing to the constraints imposed by their genital architecture. This study raises the larger question as to what constitutes a male-typical or female-typical behavior.

Female–female mounting among goats stimulates sexual performance in males

The hypothesis that female–female mounting is proceptivity in goats, in that male goats are aroused by the visual cues of this mounting behavior, was tested. Once a week, male goats were randomly selected and placed in a test pen in which they were allowed to observe one of six selected social or sexual stimulus conditions. The stimulus conditions were one familiar male with two estrous females (MEE); three estrous females that displayed female–female mounting ( E m); three estrous females that did not mount ( E nm); three non-estrous females ( N E); three familiar males ( M); and no animals in the pen (Empty). After 10 min, the stimulus animals were removed, and an estrous female was placed in the test pen with the male for a 20-min sexual performance test. During sexual performance tests, the frequencies and latencies of all sexual behaviors were recorded. This procedure was repeated so all males ( n = 6) were tested once each test day, and all the stimulus conditions were presented each test day. This was repeated weekly until all males had been exposed to each stimulus condition. Viewing mounting behavior, whether male–female or female–female, increased the total number of sexual behaviors displayed, increased ejaculation frequency, and decreased latency to first mount and ejaculation, post-ejaculatory interval, and the interval between ejaculations. We conclude that male goats are aroused by the visual cues of mounting behavior, and that female–female mounting is proceptivity in goats.

Sensory mediation of female–male mounting in the rat: II. Role of tactile and conspecific cues

Although previous research has shown that olfactory cues mediate female–male mounting (FMM) in the rat, the role of other sensory modalities on FMM has not been investigated. The present study examined the display of female mounting of castrated male rats in bilevel chambers following different tactile or locomotor activity manipulations. Female rats ( N = 40) were ovariectomized (OVX), primed with estrogen (E) and progesterone (P), and given either vaginocervical stimulation (VCS), flank/perineum stimulation (FPS), combined VCS and FPS, or general handling, immediately before each test with a castrated male rat for five trials. Compared to handling, the FPS females showed an increase in FMM behavior, whereas females given VCS, or combined VCS and FPS, showed a decrease in FMM behavior. A second experiment examined the effect of a 15-min delay between stimulation and testing using identical experimental and control conditions. There were no significant differences in the amount of FMM behavior between these groups. Finally, OVX rats primed with E and P were tested with castrated males that had been given injections of a ketamine/xylazine anesthetic mixture, saline, or amphetamine, to induce three levels of conspecific locomotor activity: none, moderate, or high, respectively. A positive linear relationship was found between male activity level and FMM. These data indicate that both tactile cues and cues associated with locomotor activity of the stimulus male modulate FMM.

Mating behaviors of the proboscis monkey (Nasalis larvatus)

The mating behaviors of the proboscis monkey were observed in a riverine forest along a tributary of the Kinabatangan River, Sabah, Malaysia, for a period of 30 months. Solicitation for copulation was initiated frequently by males and occasionally by females. Most copulations involved only one mount; however, some multiple-mount copulations were observed and a maximum of six mounts per copulation were recorded. The mean duration of mounts was about 27 sec. Nonsexual mounts (female-female, female-juvenile/infant, juvenile-juvenile, and juvenile-infant) were also observed. Female-female mounts occurred shortly after failed solicitations toward males were observed. Harassment by juveniles and/or infants was observed during copulation; however, these harassments apparently did not interfere with copulation. Sexual swelling was evident in 77.4% of copulating females, with copulating subadult females showing the most distinct swelling.

Hormonal and experiential control of female–male mounting in the female rat

Mounting behavior in the female rat has been studied extensively in same-sex interactions, but not in the heterosexual dyad. The present study examined the display of female mounting of castrated noncopulating male rats (FMM). Ovariectomized (OVX) sexually naive female rats ( N = 80) were given either estrogen (E) + progesterone (P), E + oil (O), P + O, or O + O treatment for five tests with castrated male rats. FMMs were observed in both the E + P and E + O females. The influence of the ovarian cycle on FMM was also investigated. Vaginal smears from sexually naive females ( N = 16) were taken daily for 12 days immediately after testing with castrated males. FMM frequency was greatest during Proestrus. Finally, OVX females ( N = 30) treated with E + P were given either 0, 1, 10 multi-ejaculatory heterosexual experiences with intact, sexually experienced males, prior to tests with intact, copulating or castrated, noncopulating males for five tests. Sexually naive females displayed a greater number of mounts relative to the sexually experienced females when tested with castrated, noncopulating males. In contrast, very few FMMs were observed in females of any group tested with intact, copulating males. These data suggest that FMM occurs naturally in rats as a “super-solicitational” behavior that is modified by hormone treatment and prior heterosexual experience.

A sexually dimorphic hypothalamic nucleus in a macaque species with frequent female–female mounting and same-sex sexual partner preference

In some captive and free-ranging populations, unmanipulated female Japanese macaques ( Macaca fuscata) routinely court, mount (with pelvic thrusting), compete for, and even prefer, on occasion, certain female sexual partners over certain males. The goal of this study was to determine if the cytoarchitecture of the dorsocentral portion of the anterior hypothalamic nucleus (AHdc), was male-typical in female Japanese macaques drawn from one such population. The AHdc is located in the medial preoptic anterior hypothalamus (MPO-AH), a region of the brain that is known to regulate sexual behaviour in primates. Despite their potential for male-typical sexual behaviour and sexual partner preference, our female subjects did not possess male-typical AHdc. The AHdc was significantly larger in males than it was in females, a difference that could be attributed to the significantly larger number of neurons in the male AHdc compared to that of the females. The AHdc of female Japanese macaques were no more male-typical in size than those of female rhesus macaques, a closely related sister species in which females rarely exhibit male-typical sexual behaviour. Although the AHdc may be involved in the regulation of sexual behaviour, this study indicates that a male-typical AHdc is not a prerequisite for the expression of male-typical sexual behaviour and sexual partner preference in Japanese macaques. This study is the first to examine the relationship between sex-atypical sexual activity and the cytoarchitecture of a hypothalamic nucleus in hormonally unmanipulated females.

Comparison of oligosaccharide compositions in male nuptial secretions of three cockroach species of the genus Blattella.

Male cockroaches of the genus Blattella secrete courtship pheromones from abdominal tergal glands. Conspecific females mount courting males and feed on their tergal exudates. In the German cockroach, B. germanica, a complex mixture of oligosaccharides was previously identified as the major phagostimulants in the male tergal secretion. We compared the oligosaccharide compositions of three Blattella species from different habitats, B. germanica (house), B. lituricollis (field), and B. nipponica (forest), by gas chromatographic (GC) analysis of their trifluoroacetylated derivatives. The three possessed a series of maltooligosaccharides and oligoglucosyl trehaloses with alpha1-->4 and alpha1-->1 linkages in common. However, B. germanica was conspicuous for its accumulation of a oligoglucosyl trehalose with a alpha1-->6 linkage [O-alpha-D-glucopyranosyl-(1-->6)-alpha-D-glucopyranosyl alpha-D-glucopyranoside] as the most prominent component of the secretion. Such diversification of the male pheromonal compositions within the genus might be reflected by biosynthetic systems in males and chemosensory properties in females suited for their natural habitat.

Sex and Context: Hormones and Primate Sexual Motivation

Gonadal hormones regulate the ability to copulate in most mammalian species, but not in primates because copulatory ability has been emancipated from hormonal control. Instead, gonadal hormones primarily influence sexual motivation. This separation of mating ability from hormonally modulated mating interest allows social experience and context to powerfully influence the expression of sexual behavior in nonhuman primates, both developmentally and in adulthood. For example, male rhesus monkeys mount males and females equally as juveniles, but mount females almost exclusively as adults. Having ejaculated with a female better predicted this transition to female mounting partners than did increased pubertal testosterone (T). It is proposed that increased pubertal T stimulates male sexual motivation, increasing the male's probability of sexual experience with females, ultimately producing a sexual preference for females. Eliminating T in adulthood reduces male sexual motivation in both humans and rhesus monkeys, but does not eliminate the capacity to engage in sex. In male rhesus monkeys the effects of reduced androgens on sexual behavior vary with social status and sexual experience. Human sexual behavior also varies with hormonal state, social context, and cultural conventions. Ovarian hormones influence female sexual desire, but the specific sexual behaviors engaged in are affected by perceived pregnancy risk, suggesting that cognition plays an important role in human sexual behavior. How the physical capacity to mate became emancipated from hormonal regulation in primates is not understood. This emancipation, however, increases the importance of motivational systems and results in primate sexual behavior being strongly influenced by social context.

THE RELATIONSHIP OF HABITAT AND SPATIAL DISTRIBUTION OF NESTS WITH BROWN-HEADED COWBIRD PARASITISM OF RED-WINGED BLACKBIRDS

I studied the relationship of nesting habitat and the spatial distribution of Red-winged Blackbird (Agelaius phoeniceus) nests with the frequency of brood parasitism by Brown-headed Cowbirds (Molothrus ater). For all nests combined, parasitism was over 18 times more frequent in the upland habitat. It is unlikely that the low frequency of parasitism in the marshes was due solely to an increase in the incidence of aggregate nesting. For aggregated nests, parasitism was over nine times more common in upland habitat than in marshes. Because Red-winged Blackbirds are known to react to and deter cowbirds when cowbirds are detected near nests, I assessed whether the ability of Red-winged Blackbirds to detect cowbirds may contribute to the low parasitism frequency observed in marshes. Red-winged Blackbirds nesting in marshes more often reacted aggressively to female cowbird mounts 1 m from a nest than those in upland habitat, indicating that cowbirds are more likely to be molested near nests in marshes. In upland habitat the frequency of parasitism of unaggregated nests was three times greater than that of aggregated nests. These results suggest that Red-winged Blackbirds can defend their nests against cowbirds and successfully prevent brood parasitism and that the effectiveness of nest defense varies with habitat and the spatial distribution of nests. This study provides the first direct evidence that hosts can sometimes prevent parasitism.

Intrasexual mounting in the beetle Diaprepes abbreviatus (L.).

The weevil Diaprepes abbreviatus shows three kinds of same-sex mountings: males mount other unpaired males, males mount males already engaged in copulation and females mount other females. Four hypotheses were evaluated in order to explain same-sex matings by males: (i) female mimicry by inferior males, (ii) dominance of larger males which affects the behaviour of small males, (iii) sperm transfer in which smaller males gain some reproductive success by 'hitchhiking' their sperm with the sperm of larger males, and (iv) poor sex recognition. Data from mate choice and sperm competition experiments rejected the female mimicry, dominance and sperm transfer hypotheses and supported the poor sex recognition hypothesis. We tested three hypotheses in order to explain female mounting behaviour: (i) females mimic male behaviour in order to reduce sexual harassment by males, (ii) females mount other females in order to appear larger and thereby attract more and larger males for mating, and (iii) female mimicry of males. The results of our mate choice experiments suggested that the female mimicry of males hypothesis best explains the observed female mounting behaviour. This result is also consistent with the poor sex recognition hypothesis which is the most likely explanation for male and female intrasexual mating behaviour in many insect species.

Male beetles attracted by females mounting

Intrasexual mounting is performed by males and females of many taxa1, and female–female mounting occurs in insects, lizards, birds and mammals1,2. Although the adoption by females of other male-like characters, such as mimicry of male colour patterns3,4,5, is known to be advantageous, the benefits of female–female mounting have remained mysterious. Here we describe a pattern of female–female mounting in the beetle Diaprepes abbreviatus (Curculionidae) and demonstrate that it conveys a possible evolutionary advantage by providing a greater opportunity for the females to mate with larger males. This explanation may also apply to female intrasexual mounting in several other insect species.

Vaginocervical Stimulation Inhibits Female–Female Mounting in Laboratory Rats

The objective of this study was to examine how vaginocervical stimulation (VCS) affects female–female mounting in laboratory rats. After receiving sexual stimulation from the male, the latency for the female to mount another female was significantly longer than that of control females. In the absence of any copulatory stimulation, the latency to initiate mounting of another female was about 3 min. However, following three mounts or three intromissions by a male, the latency for the experimental female to initiate mounting increased to about 10 min, and ejaculation abolished mounting for almost 2 h. Once females began mounting, regardless of the copulatory stimulation they received prior to testing, their mounting rate (mounting frequency/2 h) did not differ from stimulus control females. Artificial VCS also inhibited female mounting and anesthetization of the vaginocervical area diminished the inhibiting effect of ejaculation. Taken together, the present results provide evidence that VCS can temporarily inhibit female mounting, and that the duration of the inhibition is related to the amount of VCS received. These data are interpreted within the perspective that female mounting behavior is not a sexual behavior and is consequently suppressed within the context of normal copulation.

Sex Differences in Male-Typical Copulatory Behaviors in Response to Androgen and Estrogen Treatment in Rats

The present experiment was performed to test the hypothesis that gender differences in the capacity for brain estrogen synthesis could constitute a sexually dimorphic mechanism that limits the activational effects of testosterone (T) in females, and enhances them in males. We determined the effects of treatments with equivalent levels of either T or estradiol (E₂) on olfactory behavior and mounting in age-matched heterosexually naive gonadectomized male and female rats that were genitally ansthetized with lidocaine paste in order to minimize the contribution of sexually dimorphic somatosensory inputs to the expression of copulatory behavior. We found that T stimulated mounting to a greater extent in males than in females, but had equivalent effects on mount latency and genital investigation in the two sexes. On the other hand, E₂ stimulated equivalent levels of mounting in males and females and reduced mount latency to a similar extent in males and females. However, E₂ had a pronounced effect on the levels of genital investigation in males but not in females. Serum steroid levels and the levels of nuclear steroid receptor occupation in the brain were not different between males and females, suggesting that the behavioral differences between males and females cannot be attributed to differences in peripheral steroid metabolism or brain uptake. The results obtained corroborate previous studies suggesting that female rats normally undergo considerable male-typical behavioral masculinization during fetal development. However, such male-typical features of normal development in female rats do not extend to the regulation of preoptic aromatase activity or to the capacity of females to display olfactory behaviors in response to adult E₂ exposure, functions which are sexually dimorphic even in the rat. The present results support the view that gender differences in the capacity for brain estrogen synthesis contribute to the sexually dimorphic display of T-stimulated male-typical sexual motivation and copulatory behavior in rats.

Contextual determinants of female–female mounting in laboratory rats

Female–female mounting is widespread among mammalian species, but little is known about the proximal function of this behaviour. While such mounting is often regarded as a ‘masculine’ trait, its widespread occurrence may indicate that it serves specific functions within the context of female–female social behaviour. We valuated female mounting behaviour in Long–Evans rats in standard observation chambers and in a seminatural enclosure. Under these conditions, we examined a number of potential factors that might influence mounting, including the oestrous cycle, social hierarchy, familiarity and male presence. The female’s mounting was not influenced by her own oestrous cycle, but did vary with the oestrous cycle of the stimulus female. Socially dominant females mounted significantly more than subordinate females, and mounting by the dominant female was most frequent when the subordinate female was sexually receptive. Females mounted (and fought with) unfamiliar females significantly more than they did with familiar cagemates. Female–female mounting was dramatically reduced when males were present. Further testing showed that female mounting did not affect the induction of the progestational state of pregnancy, suggesting that female mounting does not function as a pseudomale behaviour that can substitute for genital stimulation provided by the male. Based on these data, female mounting does not appear to function as a sexual behaviour per se, but may serve as a form of female social behaviour related to maintenance of the female’s social status within female groups. In this regard, the results of this study suggest that female mounting is part of the normal female’s complex behavioural repertoire and does not necessarily reflect masculinization of some underlying neural substrate.

Presence of sex pheromones in Anocentor nitens (Acari: Ixodidae).

The aim of this study was to investigate whether there are sex pheromones in the tropical horse tick, Anocentor nitens (Neumann). When virgin males and females, fed on rabbits for 3-7 d, were tested reciprocally, there was a direct correlation between attractiveness and the period of feeding; attraction was greater (and with the fastest responses) in males and females fed for at least 6 d (sexually active males and confirmed attractive females). The capacity of sexually active males to orient topward confirmed attractive females decreased as the emission distance increased; the maximum distance that evoked a response by males was 6 cm. Confirmed attractive females lost their attractiveness approximately 2 h after being separated from the host, or after being killed by ethanol injection, although some females continued to attract sexually active males up to 4 h after death. An extract was produced by immersing confirmed attractive females in hexane and submitting them to ultrasound. Sexually active males were more attracted to and spent more time on glass bead dummies treated with this extract when compared with those treated with the hexane alone. Our results indicate the presence of at least 2 sex pheromones (attractant and mounting) in attractive females of A. nitens.

Air-movement `signals' are not required for female mounting during courtship in the cricket Teleogryllus oceanicus

Wing movements associated with stridulation by the male during cricket courtship generate air movements that have been proposed to serve as signals to the female. We assessed this putative signaling role by interfering with the presumed communications channel in two ways: (1) by removing the female's cerci, which are candidate sensory organs for signal reception, and (2) by trimming the male's forewings and thus manipulating the signal itself. We measured the effects of these treatments on the probability and latency with which females mounted courting males. We found that neither treatment affected female mounting behavior. This was true both for old, highly motivated females and for younger females, which are less highly motivated and possibly more selective. We conclude that air movements play little or no role as signals that release female mounting behavior during courtship.

What cues do brown-headed cowbirds use to locate red-winged blackbird host nests?

I examined ecological and behavioural variables influencing the susceptibility of red-winged blackbird,Agelaius phoeniceus, nests to brood parasitism by brown-headed cowbirds,Molothrus ater, in a prairie-nesting population of redwings in southern Wisconsin. I compared the following variables between parasitized and unparasitized nests: proximity of nests to trees and other prominent perches; physical characteristics of nests such as nest height and cover; and aspects of host behaviour, including vocal behaviour and aggression directed towards female cowbirds. I used these data to discriminate among four non-exclusive hypotheses for how brood parasites locate host nests: the perch-proximity, nest-exposure, nesting-cue and host-activity hypotheses. Parasitized nests were significantly closer than unparasitized nests to trees in the 2 years of the study. There was no evidence that nest height or nest cover differed significantly between parasitized and unparasitized nests, suggesting that cowbirds do not use nest exposure as a cue for locating redwing nests. The responses of both parasitized and unparasitized redwings towards a female cowbird mount decreased with increasing mount presentation distance from the nest. There were no significant differences in responses towards the mount between parasitized and unparasitized redwings, giving no support for the nesting-cue hypothesis. Female redwings whose nests were subsequently parasitized gave significantly more nest-associated (type I) vocalizations during the egg-laying period than did unparasitized females. These findings suggest that female brown-headed cowbirds in search of potential host nests use trees to search from, and that female redwing vocalizations may serve as a proximate cue for cowbirds to locate redwing nests at appropriate stages for parasitism, giving support for both the perch-proximity and host-activity hypotheses.

Characterization of two male-specific polypeptides in the tergal glands secretions of the cockroach Leucophaea maderae (Dictyoptera, blaberidae)

During the sexual behavior of cockroaches, the female mounts the courting male to feed on the proteinaceous secretion of the tergal glands. Polyacrylamide gel electrophoresis of male and female protein extracts after cuticle wiping revealed three major bands. Two of 18 and 22 kDa, named Lma-P18 and Lma-P22, are specific to the male tergal extracts. Moreover, Lma-P22 is only found in the male second tergite extracts. The third one of 54 kDa, named Lma-P54, is common to male and female extracts and could be considered as an ubiquitous surface protein. Several other minor proteins are also present on the body surface of adults of both sexes. Quantitation of the total protein amount of the male tergal gland secretion shows a progressive accumulation from adult ecdysis to sexual maturity. Western blot analysis using antibodies raised against Lma-P22 and Lma-P54 confirms that Lma-P22 is only secreted by the male second tergite glands. Immunohistolocalization demonstrates that these three major proteins are produced by class 3 glandular cells.

Red-winged blackbird parental investment following brood parasitism by brown-headed cowbirds: is parentage important?

Parental investment by red-winged blackbirds (Agelaius phoeniceus) in response to natural and experi‐mental parasitism by brown-headed cowbirds (Molothrus ater), and in response to freeze-dried, female cowbird mounts presented near redwing nests during the egg-laying period was measured. Two measures of redwing parental investment were used: nest defense effort toward a model predator, and rate of feeding nestlings. There were no significant differences in levels of parental investment among unparasitized nests, naturally parasitized nests, or experimentally parasitized nests. Similarly, parental investment did not differ between redwings that were exposed to the cowbird mount and those that were not exposed to the mount, or among redwings exposed to the cowbird mount at different distances from the nest. This suggests that red-winged blackbirds do not recognize when they have been parasitized, and hence do not associate parasitism with a decrease in their parentage, or that parentage is not an important predictor of parental investment in this species.

The role of antennal sensory cues in female responses to courting males in the cricket Teleogryllus oceanicus

Courtship communication in the field cricket Teleogryllus oceanicus is multimodal, involving a minimum of both acoustic and chemical cues. The acoustic signal, or courtship song, is necessary to elicit normal levels of female mounting of the male during courtship. Antennal input is also crucial since antennectomized females show highly reduced levels of mounting. Immobilization of the scape­pedicel and pedicel­flagellum joints of female antennae had no effect on mounting probability, suggesting that mechanosensory input from chordotonal organs at the base of the antenna is not necessary. The antennal flagellum is a multimodal sensory organ, which contains both mechanoreceptors and chemoreceptors. In order to dissect the roles of different flagellar modalities, we treated antennae with zinc sulphate. This suppressed a well-characterized contact-chemosensory behaviour, initiation of courtship by males, and eliminated responsiveness of most chemosensory hairs as assayed electrophysiologically. Zinc sulphate treatment had no effect on a tactile antennal reflex, indicating that it selectively silenced chemoreceptors. Treatment of antennae with zinc sulphate reduced mounting levels nearly as much as antennectomy, suggesting that the main antennal cue required for the mounting responses is chemosensory, rather than mechanosensory, in nature.