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Masturbation in the Animal Kingdom
The Journal of Sex Research
Abstract
Masturbation is one of the most common sexual behaviors in humans. It is also a phylogenetically widespread trait of various other mammalian and some non-mammalian species. Several hypotheses have been proposed aiming to explain the function of masturbation in primates and other species. These were mainly based on observations of nonhuman primates such as rhesus macaques or bonobos and rodents such as African ground squirrels. Based on these observations various scholars suggested that masturbation improves ejaculate quality, decreases the risk of contracting sexually transmitted infections or is merely a by-product of sexual arousal and thus an alternate outlet to copulation. While these theories may explain some facets of masturbation in some species, they do not explain why masturbation is so widespread and has developed in various species as well as our hominid ancestors. Moreover, the research on which these theories are based is scarce and heavily focused on male masturbation, while female masturbation remains largely unexplored. This sex difference may be responsible for the one-sided theorizing that attributes a specific biological benefit to masturbation. We propose that the widespread prevalence of masturbation in the animal kingdom may be better explained by viewing masturbation as a primarily self-reinforcing behavior that promotes pleasure both in human and in nonhuman species.
... While masturbation has been recorded in many mammalian species, within primates, masturbation occurs somewhat regularly (Thomsen, 2001). While most accounts of masturbation in primates are of male masturbation, female masturbation has also been recorded in many species and could be historically under sampled, rather than being a rare behavior (Roth et al., 2022). On a proximate level, masturbation can be understood as a result of sexual arousal. ...
... While many hypotheses for the adaptive value of masturbation have focused on male primates, the hypothesis that masturbation is a result of selection for increased sexuality could also be applied to female primates (Roth et al., 2022). For example, observations that female whitethighed colobus masturbated during periods of proceptivity and between mating bouts could be explained by selection for increased sexuality, or to advertise sexual receptivity and attract mates (Dixson & Anderson, 2004;Teichroeb et al., 2023;Sommer et al., 2022). ...
... Reverse mounting has been observed in many species to be a common behaviour, ranging from 5 to 25% of all mountings (Ortega-Ruano & Graves 1991; Jakubas & Wojczulanis-Jakubas 2008). The partial explanation of seemingly aberrant sexual behaviour was also historically used to dismiss the evolutionary study of other non-conceptive sexual behaviours, such as SSB (Brooks 2022), masturbation (Roth et al. 2023), and sexual acts directed towards non-conspecifics (Gröning & Hochkirch 2008), since a behaviour which exists only due to individual abnormality was assumed to be evolutionary unimportant. As such, while not discounting that some rare sexual behaviours are due to aberrant individuals (Lees et al. 2015), we consider that this explanation is at best a partial one, which has in the past hindered further research on reverse mounting. ...
... Masturbation has been observed in many animal taxa and is common in dolphins (Lateefah et al. 2022). This behavior, observed mainly in captive dolphins, is still poorly understood and may be associated with sexual frustration, the elimination of excess semen, or sexual display (Morisaka et al. 2013). ...
Cetaceans use objects and interact with conspecifics for play and socializing, often exhibiting complex behaviors that we do not understand. A few seconds of activity on the water’s surface rarely indicates intraspecific behaviors and interactions. What has already been described chiefly for common bottlenose dolphins ( Tursiops truncatus ) has been extrapolated to other species, with little information on river dolphins despite their accessibility. In this chapter, we review what is known about sexually related behaviors in different contexts, such as learning, play, sexual display, aggression, and boredom (weariness and restlessness through a lack of interest) among cetacean species, especially the Amazon river dolphin ( Inia geoffrensis ).
... We report rates and descriptions of non-reproductive sexual behaviors, including masturbation and SSB for nine study groups and one all-male band over 32 months of data collection. Masturbation is an autosexual behavior that has been reported to occur in many animals (Roth et al., 2022), including many nonhuman primate species (Thomsen & Sommer, 2015), but to our knowledge, has not been previously reported among black-and-white colobus (five species and multiple subspecies across sub-Saharan Africa). Masturbation is defined as self-manipulation of the genitalia (Bagemihl, 1999;Dixson, 2012;Thomsen et al., 2003) and a few hypotheses have been proposed to explain its function (e.g., Dixson, 2012;Dubuc et al., 2013;Waterman, 2010). ...
Rare behaviors are often missing from published papers, hampering phylogenetic analyses. Here, we report, for the first time, masturbation and same-sex sexual behavior (SSB) in both male and female black-and-white colobus monkeys. We recorded these behaviors during 32 months of observation (1573 h of focal animal sampling) on Colobus vellerosus collected at the Boabeng-Fiema Monkey Sanctuary in Ghana. Males were observed masturbating and involved in SSB more than females. Subadult males were the age-sex class that engaged in both of these behaviors most often and a third of all SSB observed in young males occurred when they were forming an all-male band (AMB), which are temporally transient social groups in this species. Our data support that masturbation in males may be a sexual outlet for individuals that do not have a current sexual partner, while in females it may function in mate attraction by advertising receptivity. SSB may occur as an evolutionary byproduct but given the temporal clustering of observed events in males prior to AMB formation, our data best support the hypothesis that these behaviors facilitate male-male bonding (i.e., act as social glue). Within AMB's, males engage in coalitionary behavior to take over social groups containing females and strong bonds are important for success and later access to females, which could have selected for SSB in C. vellerosus.
... For example, variation in clitoris morphology has been linked to different degrees of sexual arousal that could lead to increased reproductive fitness by enticing females to copulate or forming social bonds. Increasing vaginal lubrication, relaxing the vaginal opening and preparing the reproductive tract to receive sperm are among other potential functions of the clitoris [8][9][10][11]. ...
Female genitalia are conspicuously overlooked in comparison to their male counterparts, limiting our understanding of sexual reproduction across vertebrate lineages. This study is the first complete description of the clitoris (hemiclitores) in female snakes. We describe morphological variation in size and shape ( n = 9 species, 4 families) that is potentially comparable to the male intromittent organs in squamate reptiles (hemipenes). Dissection, diffusible iodine contrast-enhanced micro-CT and histology revealed that, unlike lizard hemiclitores, the snake hemiclitores are non-eversible structures. The two individual hemiclitores are separated medially by connective tissue, forming a triangular structure that extends posteriorly. Histology of the hemiclitores in Australian death adders ( Acanthophis antarcticus ) showed erectile tissue and strands/bundles of nerves, but no spines (as is found in male hemipenes). These histological features suggest the snake hemiclitores have functional significance in mating and definitively show that the hemiclitores are not underdeveloped hemipenes or scent glands, which have been erroneously indicated in other studies. Our discovery supports that hemiclitores have been retained across squamates and provides preliminary evidence of differences in this structure among snake species, which can be used to further understand systematics, reproductive evolution and ecology across squamate reptiles.
... Masturbation or self-stimulation of the genitalia is part of the natural behavioral repertoire of both non-human primates (Carpenter, 1942;Dubuc et al., 2013;Ferreira et al., 2016;Linnankoski et al., 1993;Mootnick & Baker, 1994;Nakamura, 2018;Nieuwenhuusen & Neef, 1987;Roth et al., 2022;Shalauddin et al., 2021;Thomsen, 2013;Thomsen & Soltis, 2004;Thomsen & Sommer, 2015;Waterman, 2010) and humans (Baker & Bellis, 1993;Kaestle & Allen, 2011). It occurs independently of the individual's previous intercourse experience (Dekker & Schmidt, 2008). ...
Masturbation is part of the natural behavioral repertoire of primates, with visual sexual stimuli known to trigger this behavior. Here, we report masturbation events triggered by visual sexual stimulus (VSS) in the South American primate Sapajus libidinosus. We observed a multi-male multi-female captive colony of 17 bearded capuchins between January and October 2014. Over this period, we registered 11 copulation events, 68 attempt copulations, and five masturbation events. The same low-ranking male (named Fu) performed all masturbation events. Fu directly looked at other individuals engaged in sexual displays while he masturbated in three events. The masturbation events associated with VSS lasted up to 2 min and 40 s. Our observations show that VSS can trigger masturbation in capuchin monkeys. The low hierarchy rank of the male, and the consequent lack of mating opportunities in the multi-male multi-female recently formed group in captivity, may have prompted the masturbation events.
... The lack of ejaculation after genital stone-tapping/rubbing and the majority of manual masturbation instances may still be explained from a byproduct perspective. The "sexual pleasure" hypothesis is a more holistic approach recently proposed to explain masturbation (Roth et al., 2022 (Beach, 1976; but see Allen, 1977;Temerlin, 1975). Second, female masturbation is even less frequent than male masturbation (Dixson, 2012). ...
Recent reports on tool use in nonforaging contexts have led researchers to reconsider the proximate drivers of instrumental object manipulation. In this study, we explore the physiological and behavioral correlates of two stone‐directed and seemingly playful actions, the repetitive tapping and rubbing of stones onto the genital and inguinal area, respectively, that may have been co‐opted into self‐directed tool‐assisted masturbation in long‐tailed macaques (i.e., “Sex Toy” hypothesis). We predicted that genital and inguinal stone‐tapping and rubbing would be more closely temporally associated with physiological responses (e.g., estrus in females, penile erection in males) and behavior patterns (e.g., sexual mounts and other mating interactions) that are sexually motivated than other stone‐directed play. We also predicted that the stones selected to perform genital and inguinal stone‐tapping and rubbing actions would be less variable in number, size, and texture than the stones typically used during other stone‐directed playful actions. Overall, our data partly supported the “Sex Toy” hypothesis indicating that stone‐directed tapping and rubbing onto the genital and inguinal area are sexually motivated behaviors. Our research suggests that instrumental behaviors of questionably adaptive value may be maintained over evolutionary time through pleasurable/self‐rewarding mechanisms, such as those underlying playful and sexual activities. Genital‐directed stone play actions are sexually motivated in male long‐tailed macaques. Adult females show a higher level of selectivity for the texture of the stones they use to perform genital‐directed stone play. Balinese long‐tailed macaques can use stones as tools to masturbate.
The Cambridge Dictionary definition of misogyny is: “feelings of hating women, or the belief that men are much better than women.” As explained in my Meaning of Life, Human Nature and Delusions book, sedentism and in particular agriculture and the societal changes related to them, including the origin of major organized religions, strongly contributed to many of the misogynistic narratives that became so prevalent in popular culture of agricultural states. In this chapter, I will focus on the types of discussions and data that I included in that book, which analyzed the history of misogyny and the scientific biases related to it, but with an emphasis of how those topics are linked to Darwin, his writings, and his influence on both the scientific community and the broader public.
Female Arousal and Orgasm: Anatomy, Physiology, Behaviour and Evolution is the first comprehensive and accessible work on all aspects of human female sexual desire, arousal and orgasm. The book attempts to answer basic questions about the female orgasm and questions contradictory information on the topic. The book starts with a summary of important early research on human sex before providing detailed descriptions of female sexual anatomy, histology and neuromuscular biology. It concludes with a discussion of the high heritability of female orgasmicity and evidence for and against female orgasm providing an evolutionary advantage.
The author has attempted to gather as much information on the subject as possible, including medical images, anonymized survey data and previously unreported trends. The groundbreaking book gives a scientific perspective on sexual arousal in women, and helps to uncover information gaps about this fascinating yet complex phenomenon.
Masturbation is an auto-sexual behaviour, a widespread phylogenetic trait in many taxa. Masturbation in squirrels was rarely reported. We observed an Indian palm squirrel (Funambulus palmarum) doing the auto-fellatio activity away from the scurry in Bhavanisagar, Tamil Nadu. However, the auto-fellatio behaviour in F. palmarum is novel.
Masturbation occurs throughout the animal kingdom. At first glance, however, the fitness benefits of this self-directed behaviour are unclear. Regardless, several drivers have been proposed. Non-functional hypotheses posit that masturbation is either a pathology, or a byproduct of high underlying sexual arousal, whereas functional hypotheses argue an adaptive benefit. The Postcopulatory Selection Hypothesis states that masturbation aids the chances of fertilization, while the Pathogen Avoidance Hypothesis states that masturbation helps reduce host infection by flushing pathogens from the genital tract. Here, we present comprehensive new data documenting masturbation across the primate order and use these, in conjunction with phylogenetic comparative methods, to reconstruct the evolutionary pathways and correlates of masturbation. We find that masturbation is an ancient trait within the primate order, becoming a more common aspect of the haplorrhine behavioural repertoire after the split from tarsiers. Our analyses provide support for both the Postcopulatory Selection and Pathogen Avoidance Hypotheses in male primates, suggesting that masturbation may be an adaptive trait, functioning at a macroevolutionary scale.
Previous research on Japanese macaques has shown that female-to-male mounting (FMM) is performed by some females as an exaggerated form of sexual solicitation that may occur in the context of high female competition for male mates. This supernormal courtship behavior functions to prompt subsequent male-to-female mounting. In this report, we focused on the male consort partners' responses to FMM. We studied a free-ranging population of Japanese macaques at Arashiyama, Japan, in which FMM is frequent and prevalent. We analyzed 240 consortships involving 31 females and 19 males. We tested three hypotheses regarding male's tolerance, solicitation, and use of FMM. First, we found that FMM was tolerated by male mountees who were no more likely to aggress their female partners during a short time window around a FMM than they were during the rest of the consortship period. Second, we showed that FMM could be triggered by male recipients, via explicit male-to-female sexual solicitations. Third, we found that some males may utilize FMM in a quest for their own sexual stimulation, which sometimes culminated in masturbation by the male during FMM. Our findings indicate that male partners facilitate the expression of FMM both passively (via their tolerance) and actively (via their solicitation). In addition, FMM appears to enhance the sexual arousal of male partners during consortships. We argued that, for females to have expanded their repertoire of sexual solicitations by adopting FMM, male mates must have played a role in the evolutionary origins and maintenance of this nonconceptive but intense and powerful female mating tactic.
Acerodon jubatus (the Golden-Crowned flying fox) is an endemic species in the Philippines, which was suspected to be a host of the Reston strain of the Ebola virus. As nocturnal animals, the flying foxes spend daytime at the roosting site, which they use for self-maintenance and reproduction. To understand the variation in diurnal behavior and time allocation for various activities in the Golden-Crowned flying fox, we investigated their daytime behavior and activity budget using instantaneous scan sampling and all occurrence focal sampling. Data collection was performed from 0700 to 1800 hr during January 8–17, 2017. The most frequent activity was sleeping (76.3%). The remaining activities were wing flapping (5.0%), self-grooming (4.2%), hanging relaxation (3.4%), wing spread (2.9%), movement (2.4%), mating/courtship (2.4%), aggression (1.9%), hanging alert (1.2%), excretion (0.1%) and scent marks (0.05%). The frequency of sleeping, wing flapping, self-grooming, hanging relaxation, aggression, mating/courtship and movement behaviors changed with the time of the day. Females allocated more time for resting than males, while males spent more time on the activities that helped enhance their mating opportunities, for example, movement, sexual activity and territorial behavior.
In 2015, we conducted a cross-sectional, Internet-based, U.S. nationally representative probability survey of 2,021 adults (975 men, 1,046 women) focused on a broad range of sexual behaviors. Individuals invited to participate were from the GfK KnowledgePanel®. The survey was titled the 2015 Sexual Exploration in America Study and survey completion took about 12 to 15 minutes. The survey was confidential and the researchers never had access to respondents’ identifiers. Respondents reported on demographic items, lifetime and recent sexual behaviors, and the appeal of 50+ sexual behaviors. Most (>80%) reported lifetime masturbation, vaginal sex, and oral sex. Lifetime anal sex was reported by 43% of men (insertive) and 37% of women (receptive). Common lifetime sexual behaviors included wearing sexy lingerie/underwear (75% women, 26% men), sending/receiving digital nude/semi-nude photos (54% women, 65% men), reading erotic stories (57% of participants), public sex (≥43%), role-playing (≥22%), tying/being tied up (≥20%), spanking (≥30%), and watching sexually explicit videos/DVDs (60% women, 82% men). Having engaged in threesomes (10% women, 18% men) and playful whipping (≥13%) were less common. Lifetime group sex, sex parties, taking a sexuality class/workshop, and going to BDSM parties were uncommon (each <8%). More Americans identified behaviors as “appealing” than had engaged in them. Romantic/affectionate behaviors were among those most commonly identified as appealing for both men and women. The appeal of particular behaviors was associated with greater odds that the individual had ever engaged in the behavior. This study contributes to our understanding of more diverse adult sexual behaviors than has previously been captured in U.S. nationally representative probability surveys. Implications for sexuality educators, clinicians, and individuals in the general population are discussed.
Evidence is presented as an alternative to the authors' claims that in the course of evolution, a link between orgasm and ovulation has been lost in women, that evolutionary changes in clitoral anatomy underlie this loss, and that women's orgasm plays no significant role in reproduction.
Background
Although humans experience orgasms with a degree of statistical regularity, they remain among the most enigmatic of sexual responses; difficult to define and even more difficult to study empirically. The question of whether animals experience orgasms is hampered by similar lack of definition and the additional necessity of making inferences from behavioral responses.
Method
Here we define three behavioral criteria, based on dimensions of the subjective experience of human orgasms described by Mah and Binik, to infer orgasm-like responses (OLRs) in other species: 1) physiological criteria that include pelvic floor and anal muscle contractions that stimulate seminal emission and/or ejaculation in the male, or that stimulate uterine and cervical contractions in the female; 2) short-term behavioral changes that reflect immediate awareness of a pleasurable hedonic reward state during copulation; and 3) long-term behavioral changes that depend on the reward state induced by the OLR, including sexual satiety, the strengthening of patterns of sexual arousal and desire in subsequent copulations, and the generation of conditioned place and partner preferences for contextual and partner-related cues associated with the reward state. We then examine whether physiological and behavioral data from observations of male and female rats during copulation, and in sexually-conditioned place- and partner-preference paradigms, are consistent with these criteria.
Results
Both male and female rats display behavioral patterns consistent with OLRs.
Conclusions
The ability to infer OLRs in rats offers new possibilities to study the phenomenon in neurobiological and molecular detail, and to provide both comparative and translational perspectives that would be useful for both basic and clinical research.
Exercise is rewarding, and long-distance runners have described a
runner’s high as a sudden pleasant feeling of euphoria, anxiolysis,
sedation, and analgesia. A popular belief has been that endogenous
endorphins mediate these beneficial effects. However, running
exercise increases blood levels of both β-endorphin (an opioid) and
anandamide (an endocannabinoid). Using a combination of pharmacologic,
molecular genetic, and behavioral studies in mice, we demonstrate
that cannabinoid receptors mediate acute anxiolysis and
analgesia after running. We show that anxiolysis depends on intact
cannabinoid receptor 1 (CB1) receptors on forebrain GABAergic neurons
and pain reduction on activation of peripheral CB1 and CB2 receptors.
We thus demonstrate that the endocannabinoid system is
crucial for two main aspects of a runner’s high. Sedation, in contrast,
was not influenced by cannabinoid or opioid receptor blockage, and
euphoria cannot be studied in mouse models.
This book provides an authoritative and comprehensive synthesis of current research on the evolution and physiological control of sexual behaviour in the primates - prosimians, monkeys, apes, and human beings. This new edition has been fully updated and greatly expanded throughout to incorporate a decade of new research findings. It maintains the depth and scientific rigour of the first edition, and includes a new chapter on human sexuality, written from a comparative perspective.
A previously unpublished four-page pamphlet by Dr. George Murray Levick R.N. (1876–1956) on the ‘Sexual habits of the Adélie penguin’ was recently rediscovered at the Natural History Museum (NHM) at Tring. It was printed in 1915 but declined for publication with the official expedition reports. The account, based upon Levick's detailed field observations at Cape Adare (71°18′S, 170°09′E) during the course of the British Antarctic (Terra Nova) Expedition 1910, commented on frequency of sexual activity, autoerotic behaviour, and seemingly aberrant behaviour of young unpaired males and females including necrophilia, sexual coercion, sexual and physical abuse of chicks, non-procreative sex and homosexual behaviour. His observations were however accurate, valid and, with the benefit of hindsight, deserving of publication. Here we publish the pamphlet in its entirety, reinterpret selected observations and comment on its significance as a forgotten work by the pioneer of research on Adélie penguin Pygoscelis adeliae (Hombron and Jacquinot 1841) biology.
Sexual behaviour and relationships are key components of wellbeing and are affected by social norms, attitudes, and health. We present data on sexual behaviours and attitudes in Britain (England, Scotland, and Wales) from the three National Surveys of Sexual Attitudes and Lifestyles (Natsal).
We used a multistage, clustered, and stratified probability sample design. Within each of the 1727 sampled postcode sectors for Natsal-3, 30 or 36 addresses were randomly selected and then assigned to interviewers. To oversample individuals aged 16-34 years, we randomly allocated addresses to either the core sample (in which individuals aged 16-74 years were eligible) or the boost sample (in which only individuals aged 16-34 years were eligible). Interviewers visited all sampled addresses between Sept 6, 2010, and Aug 31, 2012, and randomly selected one eligible individual from each household to be invited to participate. Participants completed the survey in their own homes through computer-assisted face-to-face interviews and self-interview. We analysed data from this survey, weighted to account for unequal selection probabilities and non-response to correct for differences in sex, age group, and region according to 2011 Census figures. We then compared data from participants aged 16-44 years from Natsal-1 (1990-91), Natsal-2 (1999-2001), and Natsal-3.
Interviews were completed with 15 162 participants (6293 men, 8869 women) from 26 274 eligible addresses (57·7%). 82·1% (95% CI 81·0-83·1%) of men and 77·7% (76·7-78·7%) of women reported at least one sexual partner of the opposite sex in the past year. The proportion generally decreased with age, as did the range of sexual practices with partners of the opposite sex, especially in women. The increased sexual activity and diversity reported in Natsal-2 in individuals aged 16-44 years when compared with Natsal-1 has generally been sustained in Natsal-3, but in men has generally not risen further. However, in women, the number of male sexual partners over the lifetime (age-adjusted odds ratio 1·18, 95% CI 1·08-1·28), proportion reporting ever having had a sexual experience with genital contact with another woman (1·69, 1·43-2·00), and proportion reporting at least one female sexual partner in the past 5 years (2·00, 1·59-2·51) increased in Natsal-3 compared with Natsal-2. While reported number of occasions of heterosexual intercourse in the past 4 weeks had reduced since Natsal-2, we recorded an expansion of heterosexual repertoires-particularly in oral and anal sex-over time. Acceptance of same-sex partnerships and intolerance of non-exclusivity in marriage increased in men and women in Natsal-3.
Sexual lifestyles in Britain have changed substantially in the past 60 years, with changes in behaviour seeming greater in women than men. The continuation of sexual activity into later life-albeit reduced in range and frequency-emphasises that attention to sexual health and wellbeing is needed throughout the life course.
Grants from the UK Medical Research Council and the Wellcome Trust, with support from the Economic and Social Research Council and the Department of Health.
The beneficial and well-being effects of human sexual arousal induced by coitus or masturbation are reviewed. Greater sexual satisfaction and some health rewards are given by coitally obtained orgasms even though those from masturbation may be more physiologically intense. The functionality of the circulatory, neural and muscular systems of the male and female genitalia are maintained by arousal and orgasm (maintenance functions) both in the conscious state and when asleep. Prophylactic actions (preventative functions) occur in relation to prostate cancer, implantation and dysmenorrhoea. In the male, ejaculations keep sperm morphology and semen volume within normal ranges while leukocyte numbers are increased. In the female, with coital vaginal deposition of semen mood enhancement occurs, menstrual cycles are more often of the ovulatory (fertile) type and postmenopausal vaginal atrophy is counteracted.
Tool use has been broadly defined as the external employment of an unattached inanimate object
to alter the form, position, or condition of another object, another organism, or the user itself [1].
Tool manufacture has been considered to be a modification of the physical properties of an
inanimate object so that it can be used more efficiently as a tool. Tool use has been widely,
though sporadically, reported for all the families of nonhuman primates, except the Callitrichidae
and the prosimians [1]. Authentic examples of tool manufacture, however, are rare in monkeys
(with the notable exception of the New World genus Cebus, the capuchins, in captivity) and
appear to be restricted principally to the great apes (chimpanzees, orang-utans). Amongst the Old
World monkeys, only lion-tailed macaques (Macaca silenus) in captive social groups have been
observed to manufacture tools by detaching sticks from larger branches to extract food from the
narrow openings of enclosed containers.
Each generation has adopted views on masturbation via transforming cultural definitions of sexuality and normality. This article presents how masturbation habits have changed during the last decades in different generations and how these habits are linked to the partnership status. The analysis is based on three national follow-up sex surveys in Finland (in 1971, in 1992, and in 1999), and sex surveys in Sweden (in 1996), in Estonia (in 2000), and in St. Petersburg, Russia (in 1996).Across these countries, each new generation had been more active in masturbation than the previous one. However, in Estonia masturbation had increased in each generation about 20 years later and in St. Petersburg about 30 years later than in Finland and Sweden. The increase in masturbation was almost unrelated to the relationship status and to the years spent in the relationship. The masturbation habits that each generation had internalized in adolescence seemed to remain unchanged through the course of their lives. The implications of these findings are that masturbation did not decrease with age and that masturbation was not a compensation for a missing sex partner but an independent way to gain sexual pleasure. The results indicate that masturbation is linked to the perceptions within a given culture of its nature and consequences during the teenage years of participants.
Many ophidians exhibit prolonged copulation, a behaviour hypothesised to be the result of a slow and gradual ejaculation process or a behaviour aimed toward reducing sperm competition (male mate guarding). While observing courtship behaviour in a captive colony of the African brown house snake, Lamprophis fuliginosus, some males excreted a large amount of sperm very rapidly before the inflation and insertion of the males' hemipenis into the females' vent. This observation of premature ejaculation suggests that male snakes may be capable of rapid ejaculation and, therefore, likely copulate for an extended period of time to prevent rival males from mating with the same female, thus increasing the chance of paternity for the male.
The captive gorilla population may not be self-sustaining, in part because the overall birth rate is low and because many potential founders have failed to reproduce. We used questionnaires to collect standardized biographies of every gorilla held in North America. These biographies were searched for factors associated with reproductive success or failure.
Captive-born gorillas are reproducing at least as well as wild-borns, when reproductive success is expressed as number of infants per year of reproductive opportunity. Mother-reared females are reproductively more successful than hand-reared females, but there is no difference in the reproductive success of mother-reared and hand-reared males. Social access to conspecifics in the 1st year is associated with higher reproductive success, at least for females. Reproductively successful and unsuccessful gorillas of both sexes have had equal access to potential mates, but unsuccessful animals are less likely than successful ones to exhibit normal sexual behavior.
We conclude that many cases of reproductive failure are due to deficits in sexual behavior, which in turn may result from lack of early social experience with conspecifics. Some reproductive failure involves medical problems; interventive diagnostic techniques continue to be useful, if only to identify healthy individuals that can be managed intensively.
The probability that a female will be a competent mother is not affected by her being wild-born or captive-born, or mother-reared or hand-reared.
A runner's high describes a sense of well-being during endurance exercise characterized by euphoria and anxiolysis. It has been a widespread belief that the release of endogenous opioids, such as endorphins, underlie a runner's high. However, exercise leads to the release of two classes of rewarding molecules, endocannabinoids (eCBs) and opioids. In mice, we have shown that core features of a runner's high depend on cannabinoid receptors but not opioid receptors. In the present study, we aimed to corroborate in humans that endorphins do not play a significant role in the underlying mechanism of a runner's high. Thus, we investigated whether the development of two core features of a runner's high, euphoria and reduced anxiety levels, depend on opioid signaling by using the opioid receptor antagonist naltrexone (NAL) in a double-blind, randomized, placebo (PLA)-controlled experiment. Participants (N=63) exhibited increased euphoria and decreased anxiety after 45 min of running (RUN) on a treadmill in a moderate-intensity range compared to walking (WALK). RUN led to higher plasma levels of the eCBs anandamide (AEA) and 2-arachidonoglycerol (2-AG). Opioid blockade did not prevent the development of euphoria and reduced anxiety as well as elevation of eCB levels following exercise. Moreover, the fraction of participants reporting a subjective runner's high was comparable in the NAL and PLA-treated group. Therefore, this study indicates that the development of a runner's high does not depend on opioid signaling in humans, but makes eCBs strong candidates in humans, as previously shown in mice.
Inferring functional components of behavioral sequences is a crucial but challenging task. A systematic comparison of their temporal structure is a good starting point, based on the postulate that more functional traits are less structurally variable. We studied stone handling behavior (SH) in Balinese long-tailed macaques, a versatile form of stone-directed play. We tested the hypothesis that stones are used by male monkeys to stimulate their genitals in a sexual context (i.e., “sex toy” hypothesis). Specifically, two SH actions (i.e., “tap-on-groin” (TOG) and “rub-on-groin” (ROG), respectively the repetitive tapping and rubbing of a stone onto the genital area) gained functional properties as self-directed tool-assisted masturbation. Owing to the structural organization of playful activities, we predicted that SH sequences without TOG/ROG would exhibit higher levels of variability, repeatability and exaggeration than SH sequences with TOG/ROG. We also predicted that TOG/ROG would occur more often and last longer in SH sequences in which penile erection – a sexually-motivated physiological response in primates – was observed than in SH sequences in which penile erection was not observed.
To identify and compare recurring series of SH patterns otherwise undetectable by using conventional quantitative approaches across SH sequences containing TOG/ROG or not, we used a temporal analysis known as “T-pattern detection and analysis” (TPA). Our predictions about variability, exaggeration and temporal association between TOG/ROG in males and penile erection were supported. As expected, SH sequences without TOG/ROG were, on average, more repeatable than SH sequences with TOG/ROG, but the difference was not statistically significant. Overall, the “sex toy” hypothesis was partly supported, and our results suggested that TOG and ROG are two forms of tool-assisted genital stimulation, possibly derived from the playful handling of stones. These findings are consistent with the view that tool use may evolve in stages from initially non-functional object manipulation, such as object play.
Masturbation, as a significant sexual activity within its own right, has garnered substantial interest as a research topic only within the past 10–20 years. In this in-depth analysis of masturbation in women, we examined relationships among frequencies of, reasons for, and activities during masturbation, and investigated how such parameters predict orgasmic pleasure, latency, and difficulty. Participants were 2215 women at least 18 years of age participating in a 42-item opt-in online survey that collected detailed information about women’s orgasmic response during masturbation and partnered sex. Higher frequency of masturbation was related to lower satisfaction with partner, greater importance of sex, and higher levels of general anxiety/depression. Frequency of, reasons for, and activities during masturbation predicted both orgasmic pleasure and orgasmic difficulty during masturbation. The pattern of results enabled the development of three typologies of women who differ systematically with respect to their masturbation and partnered sex behaviors.
Background: Endocannabinoids are critical for rewarding behaviors such as eating, physical exercise, and social
interaction. The role of endocannabinoids in mammalian sexual behavior has been suggested because of the
influence of cannabinoid receptor agonists and antagonists on rodent sexual activity. However, the involvement
of endocannabinoids in human sexual behavior has not been studied.
Aim: To investigate plasma endocannabinoid levels before and after masturbation in healthy male and female
volunteers.
Outcomes: Plasma levels of the endocannabinoids 2-arachidonoylglycerol (2-AG), anandamide, the
endocannabinoid-like lipids oleoyl ethanolamide and palmitoyl ethanolamide, arachidonic acid, and cortisol
before and after masturbation to orgasm.
Methods: In study 1, endocannabinoid and cortisol levels were measured before and after masturbation to
orgasm. In study 2, masturbation to orgasm was compared with a control condition using a single-blinded,
randomized, 2-session crossover design.
Results: In study 1, masturbation to orgasm significantly increased plasma levels of the endocannabinoid 2-AG,
whereas anandamide, oleoyl ethanolamide, palmitoyl ethanolamide, arachidonic acid, and cortisol levels were not
altered. In study 2, only masturbation to orgasm, not the control condition, led to a significant increase in 2-AG
levels. Interestingly, we also found a significant increase of oleoyl ethanolamide after masturbation to orgasm in
study 2.
Clinical Translation: Endocannabinoids might play an important role in the sexual response cycle, leading to
possible implications for the understanding and treatment of sexual dysfunctions.
Strengths and Limitations: We found an increase of 2-AG through masturbation to orgasm in 2 studies
including a single-blinded randomized design. The exact role of endocannabinoid release as part of the sexual
response cycle and the biological significance of the finding should be studied further. Cannabis and other drug
use and the attainment of orgasm were self-reported in the present study.
Conclusion: Our data indicate that the endocannabinoid 2-AG is involved in the human sexual response cycle
and we hypothesize that 2-AG release plays a role in the rewarding consequences of sexual arousal and orgasm.
Objectives
For a long time taboo, the practice of feminine masturbation tends to be trivialised under the effect of a change in cultural representations and public discourse on the subject – for example, in films, music or TV series – but also the effect of much wider access for women to arousal media (e.g. on-line pornography, erotic books) or self-stimulation objects more suitable for the expectations of a feminine audience (sex toys). Symptomatic of changing cultural norms, which hang over female sexuality, this ability of women to take on the purely individual and autoerotic share of their sexuality highlights their greater ease to admit to practices, which are not within the socially-acceptable framework of the couple. Despite the fact that the behaviour of both sexes have come much closer in the matter, masturbation is still far from becoming a component of women's sexual repertoire which is as normal as it is for men, nor is it a practice that is easily admitted to a partner.
Method
The survey was carried out by self-administered questionnaire on-line with a sample of 913 women from 18 to 69 years of age, extracted from a sample of 2011 people representative of the French population aged 18 and older, in June 2017. Quotas were used to ensure that the samples used were, overall, properly representative (sex, age, occupation, region, urban unit size, marital status).
Results
The comparison of these data with those measured in 2012 using identical procedures shows that the masturbation behaviour of women is much closer to that of men than it was before. Similarly, the comparison of the autoerotic activities of women in a couple with those of single women reveals that masturbation continues in a couple for a number of women, as a substitute for or in parallel with conjugal sexual relations. But this form of solitary pleasure is far from being accepted within couples, in particular by women who are dissatisfied with the quality and quantity of their conjugal relations.
Conclusion
For many women living in a couple (45%), masturbation remains a taboo subject, no doubt because they fear that this practice would be interpreted as a sign of the inability of their partner to meet their needs. The taboo around female masturbation therefore still has great resonance, not only among women who struggle to disassociate sexuality and conjugality but also among those whose partner shows signs of failing sexuality.
Male and female primates from all extant radiations engage in autosexual behaviors, implying that masturbation is a facet of the sexual repertoire of our hominid ancestors. At a proximate level, masturbation results in relaxation and reduced aggressiveness. At an ultimate level, male masturbation might be beneficial because old and low-quality sperm are discarded, while fresh sperm production is stimulated. Convincing functional explanations for female masturbation are still lacking.
This chapter focuses on the two ejaculatory conditions most commonly reported in clinical settings, namely premature ejaculation (PE) and delayed/inhibited ejaculation (IE), both of which relate to the timing/occurrence of ejaculation. It discusses these two conditions separately, providing information about definition, prevalence, etiology, diagnosis, and treatment. Brief psychological and relationship histories, as well as assessment of current sexual functioning, can help to assess the quality of the individual's sexual response cycle-desire, arousal, and orgasm-and may call attention to individual or relationship idiosyncrasies. Similar to treating men with PE, therapeutic interventions for men with primary or secondary IE may be nested within behavioral, cognitive, and relational approaches. The chapter summarizes interventions in these three domains and presents a structured brief treatment framework that providers can use with men with either PE or IE, relying on key process interventions that might be broadly applied to either orgasmic disorder.
Beneficial effects of voluntary wheel running on hippocampal neurogenesis, morphology and hippocampal-dependent behavior have widely been studied in rodents, but also serious side effects and similarities to stereotypy have been reported. Some mouse strains run excessively when equipped with running wheels, complicating the comparability to human exercise regimes. Here, we investigated how exercise restriction to 6 h/day affects hippocampal morphology and metabolism, stereotypic and basal behaviors, as well as the endocannabinoid system in wheel running C57BL/6 mice; the strain most commonly used for behavioral analyses and psychiatric disease models. Restricted and unrestricted wheel running had similar effects on immature hippocampal neuron numbers, thermoregulatory nest building and basal home-cage behaviors. Surprisingly, hippocampal gray matter volume, assessed with magnetic resonance (MR) imaging at 9.4 Tesla, was only increased in unrestricted but not in restricted runners. Moreover, unrestricted runners showed less stereotypic behavior than restricted runners did. However, after blockage of running wheels for 24 h stereotypic behavior also increased in unrestricted runners, arguing against a long-term effect of wheel running on stereotypic behavior. Stereotypic behaviors correlated with frontal glutamate and glucose levels assessed by 1H–MR spectroscopy. While acute running increased plasma levels of the endocannabinoid anandamide in former studies in mice and humans, we found an inverse correlation of anandamide with the daily running distance after long-term running. In conclusion, although there are some diverging effects of restricted and unrestricted running on brain and behavior, restricted running does not per se seem to be a better animal model for aerobic exercise in mice.
The evolutionary explanation of female orgasm has been difficult to come by. The orgasm in women does not obviously contribute to the reproductive success, and surprisingly unreliably accompanies heterosexual intercourse. Two types of explanations have been proposed: one insisting on extant adaptive roles in reproduction, another explaining female orgasm as a byproduct of selection on male orgasm, which is crucial for sperm transfer. We emphasize that these explanations tend to focus on evidence from human biology and thus address the modification of a trait rather than its evolutionary origin. To trace the trait through evolution requires identifying its homologue in other species, which may have limited similarity with the human trait. Human female orgasm is associated with an endocrine surge similar to the copulatory surges in species with induced ovulation. We suggest that the homolog of human orgasm is the reflex that, ancestrally, induced ovulation. This reflex became superfluous with the evolution of spontaneous ovulation, potentially freeing female orgasm for other roles. This is supported by phylogenetic evidence showing that induced ovulation is ancestral, while spontaneous ovulation is derived within eutherians. In addition, the comparative anatomy of female reproductive tract shows that evolution of spontaneous ovulation is correlated with increasing distance of clitoris from the copulatory canal. In summary, we suggest that the female orgasm-like trait may have been adaptive, however for a different role, namely for inducing ovulation. With the evolution of spontaneous ovulation, orgasm was freed to gain secondary roles, which may explain its maintenance, but not its origin.
The paper emphasizes that ideas about masturbation are crucial to understanding any societal attitudes toward sex. It examines attitudes to masturbation in ancient Egypt, Tigris Euphrates Valley, India, and China. It looks at Biblical views and their misinterpretations and at the Greek and Roman descriptions of masturbatory practices. Key to the development of western attitudes was the Augustinian version of sex which was influenced by Augustine's personal background in Manichaeanism, a religion which was based on ancient Persian beliefs. The Augustinian view of all non-procreative sex as a sin was carried over into medicine in the eighteenth century which changed sins into pathologies. The only advantage this had over the sin model (which still remained for large segments of the population) was that it allowed research to challenge past assumptions and as medical ideas changed so did those about sex. It was not until the beginning of the twentieth century with new scientific discoveries about sexually transmitted diseases that masturbation could be studied more objectively. Attitudes were slow to change but as they did so attitudes towards human sexuality also changed. The two changes, it is held, are closely tied together and this is why an understanding of attitudes toward masturbation is a key to understanding changing development in attitudes toward human sexuality.
The search for the legendary, highly erogenous vaginal region, the Gräfenberg spot (G-spot), has produced important data, substantially improving understanding of the complex anatomy and physiology of sexual responses in women. Modern imaging techniques have enabled visualization of dynamic interactions of female genitals during self-sexual stimulation or coitus. Although no single structure consistent with a distinct G-spot has been identified, the vagina is not a passive organ but a highly dynamic structure with an active role in sexual arousal and intercourse. The anatomical relationships and dynamic interactions between the clitoris, urethra, and anterior vaginal wall have led to the concept of a clitourethrovaginal (CUV) complex, defining a variable, multifaceted morphofunctional area that, when properly stimulated during penetration, could induce orgasmic responses. Knowledge of the anatomy and physiology of the CUV complex might help to avoid damage to its neural, muscular, and vascular components during urological and gynaecological surgical procedures.
Male Tooth-billed Bowerbirds Scenopoeetes dentirostris were filmed (n = 25), directly observed (n = 28) and audio-recorded (n = 84). Courtship display consisted of two discrete components: a period of vocal mimicry from a concealed location followed by vigorously animated posturing and vocalisation across the display court. A contrastingly pigmented mouth interior, erected throat feathers and leaps accompanied by wing flaps and swinging tail movements were used in this visual display. Displays of Toothbilled Bowerbirds are most similar to those of Arnblyornis bowerbird species and an unrelated African ploceid finch Euplectes jacksoni, in which males hide behind vegetation and produce sounds prior to visual display and mating. Besides the use of bowers, there are marked similarities between male displays of Sc. Dentirostris and Arnblyornis spp. and, to a lesser degree, Sericulus, Ptilonorhynchus and Chlarnydera bowerbirds confirming close relationship among the genera. Origins and functions of bower building and the validity of the genus Scenopoeetes are discussed.
Auto-sexual behaviour (masturbation) is the most common sexual activity of humans, but surprisingly little is known about how it evolved and why it occurs. For centuries, masturbation has been considered taboo or regarded as an unnatural and even pathologic behaviour (Laqueur 2004). During the last decade however, it has been revealed that masturbation is a common part of the sexual repertoire in non-human primate populations as well. Masturbation is more prevalent in species that exhibit a polygynandrous (multi-male, multi-female) breeding system but it also occurs in harems and in solitary taxa. This suggests that masturbation is an ancestral, phyologenetically widespread trait within the order of primates and further implies that it is a facet of our own hominid ancestor's sexual repertoire (Thomsen et al. 2003). In around 80 species from all major radiations of the living anthropoid primates, males were observed to exhibit masturbatory behaviours that slightly differ in some peculiarities. In several species of New World monkeys, Old World monkeys, lesser apes and great apes, males are reported to masturbate frequently using their hands, feet or mouth to stimulate their genitals until ejaculation occurs. In prosimians, one of the most evolutionarily ancient primate taxon, masturbation is known in mouse lemurs and galagos. In females, masturbation is described in 50 primate species (Jones 2005). Females exhibit more sophisticated kinds of masturbatory behaviours than males. Besides the whole ano-genital region they include stimulation of the breast region using various substrates. Females of species that are known for the use of tools use "tool-like" objects to masturbate. Orang-utans prepare sticks of adequate size, bonobos use pieces of lianas and capuchin monkeys use plant parts for vaginal stimulation. However, it is more difficult to rate the level of arousal in females. Vocalisation, distinctive facial expressions or excitement visibly occur in some taxa (macaques, cebids, guenons), but usually female orgasm (if any) seems concealed.
The adaptive function of male masturbation is still poorly understood, despite its high prevalence in humans and other animals. In non-human primates, male masturbation is most frequent among anthropoid monkeys and apes living in multimale-multifemale groups with a promiscuous mating system. In these species, male masturbation may be a non-functional by-product of high sexual arousal or be adaptive by providing advantages in terms of sperm competition or by decreasing the risk of sexually transmitted infections. We investigated the possible functional significance of male masturbation using behavioral data collected on 21 free-ranging male rhesus macaques (Macaca mulatta) at the peak of the mating season. We found some evidence that masturbation is linked to low mating opportunities: regardless of rank, males were most likely to be observed masturbating on days in which they were not observed mating, and lower-ranking males mated less and tended to masturbate more frequently than higher-ranking males. These results echo the findings obtained for two other species of macaques, but contrast those obtained in red colobus monkeys (Procolobus badius) and Cape ground squirrels (Xerus inauris). Interestingly, however, male masturbation events ended with ejaculation in only 15% of the observed masturbation time, suggesting that new hypotheses are needed to explain masturbation in this species. More studies are needed to establish whether male masturbation is adaptive and whether it serves similar or different functions in different sexually promiscuous species.
The current investigation examined the relationship between masturbation and body image among 96 women seeking services at a local family planning clinic in a mid-southern U.S. city. Participants completed a questionnaire that assessed body image and masturbatory practices. Ethnic differences were found with European American women reporting greater masturbation frequencies and higher rates of body dissatisfaction than African American women. Among European American women, there was a positive relationship between women's sexual self-pleasuring and positive body image. For African American participants, body image was not related to masturbation practice or frequency.
Introduction:
Women describe at least two types of orgasms: clitoral and vaginal. However, the differences, if any, are a matter of controversy. In order to clarify the functional anatomy of this sexual pleasure, most frequently achieved through clitoral stimulation, we used sonography with the aim of visualizing the movements of the clitorourethrovaginal (CUV) complex both during external, direct stimulation of the clitoris and during vaginal stimulation.
Method:
The ultrasounds were performed in three healthy volunteers with the General Electric® Voluson® sonography system (General Electric Healthcare, Vélizy, France), using a 12-MHz flat probe and a vaginal probe. We used functional sonography of the stimulated clitoris either during manual self-stimulation of the external clitoris or during vaginal penetration with a wet tampon.
Main outcome measures:
Functional and anatomic description, based on bidimensional ultrasounds, of the clitoris and CUV complex, as well as color Doppler signal indicating speed of venous blood flow, during arousal obtained by external or internal stimulation.
Results:
The sagittal scans obtained during external stimulation and vaginal penetration demonstrated that the root of the clitoris is not involved with external clitoral stimulation. In contrast, during vaginal stimulation, because of the movements and displacements, the whole CUV complex and the clitoral roots in particular are involved, showing functional differences depending on the type of stimulation. The color signal indicating flow speed in the veins mirrored the anatomical changes.
Conclusions:
Despite a common assumption that there is only one type of female orgasm, we may infer, on the basis of our findings, that the different reported perceptions from these two types of stimulation can be explained by the different parts of the clitoris (external and internal) and CUV complex that are involved.
The behavior of a breeding colony of captive vampire bats, Desmodus rotundus, was observed for several years in Trinidad. Daily consumption of defibrinatcd blood averaged from 10 ml to 25 ml per bat. Drinking water was essential. Ectoparasites quickly disappeared from freshly caught bats. Red pelage changed to brownish and grayish within 8 months. A brownish bat dropped into vampire urine turned red in about 24 hours. Bats spent much time in mutual cleaning and preening. Desmodus is promiscuous. Male mounted female dorsally and held female's forearms with thumbs. Courtship and aberrant behavior are described.
Scent-urination is documented and described for the males of several bovid and cervid species. Evidence is given indicating that the fluid released is in all cases urine, and not semen as is commonly assumed, although there is a possibility that both are involved owing to the apparent "hybrid" nature of the act. The significance of scent-urination has not been determined by experimentation, but behavioral observations suggest that in male-male interactions the urine indicates both age dominance and physical condition. Physical condition is indicated by metabolic by-products excreted via the urine and age dominance by the strong odor. The odor is probably the primary male-male function of the behavior, although the metabolites are the cue by which subdominants determine the dominants' decline in condition. The possibility that the behavior functions primarily in male-female interactions cannot be entirely ruled out. In fact, the behavior may have evolved to hasten and synchronize the onset of estrous to coincide with the male's peak condition. The odor of males seems to increase with age, and this odor serves to mask the metabolities in order to increase the dominants' tenure of breeding status. Dominants are selected to be better able to mask their decline as indicated by the excreted metabolites, and subdominants are selected to better perceive the decline in spite of the deception.
1.1. Redirected copulation is described in the Fischer's Lovebird, Agapornis fischei; Wood Thrush, Hylocichla mustelina; and the American Redstart, Setophaga ruticilla.2.2. Redirected copulation occurs when the male is thwarted sexually because the female (providing the initial stimulation) becomes unavailable for some reason during the normal course of a precopulatory sequence.3.3. The substitute object resembles a soliciting female in that both are non fear-provoking protuberances in the male's immediate surroundings.4.4. In one case, that of the Redstart, the substitute object apparently came, through learning, to have releasing (as well as directing stimuli) of its own.5.5. Apparently redirection rather than displacement may be performed if the immediate surroundings provide an adequate substitute for the suddenly unavailable usual object or situation.6.6. Redirection is considered to be a special type of reaction to “subnormal” stimuli, although the activity is initiated by “normal” stimuli.
Przewalski's horses (Equus przewalskii) are believed to be extinct in the wild; the current known population of 797 animals exists wholly in zoos. The Species Survival Commission of the International Union for Conservation of Nature and Natural Resources is proposing to reintroduce this endangered species into its former Mongogian habitat within the next decade. Knowledge of the behavior of harem-forming equids in general and of Przewalski's horses in particular, is of great importance to the captive propagation and eventual reintroduction of this species.Horses are rarely solitary by nature. Solitary captive animals are prone to pacing. Juvenile male feral horses (Equus caballus) form bachelor herds upon dispersal from their natal band. Zoos can set up bachelor herds as a way of managing surplus males. The older, more dominant feral horse bachelors are the first to acquire mares. Bachelors do not generally obtain females until they are 4 or 5 years of age. The first females acquired are usually 1- and 2-year-old fillies dispersing from their natal band.Because of the age differential, the stallions are generally dominant to their mares. Behavioral impotence may result if captive stallions are given a harem at too young an age, especially if the harem contains older, more dominant, females. Typical harem sizes in the wild are 3–5 mares. Captive stallions with too large a harem may become either apathetic or aggressive toward their mares.Wild horses spend 60–70% of their time foraging. Captive animals may quickly consume their limited amounts of food and develop vices out of boredom. Provision of hay ad libitum reduces the amount of pacing seen in captive animals, and virtually eliminates coprophagy.
Intra-vaginal and intra-uterine pressure changes during human coitus were monitored by the use of a pressure-sensitive radiopill.
Pressure was found to be negative in the vagina during intromission and male orgasm but became positive during female orgasm. In the uterus, the pressure changes were minimal during male orgasm but increased markedly during female orgasm to a positive pressure of 40 cm H2O, followed by a sharp fall after orgasm to a negative pressure of 26 cm H2O.
The reliability of these results is discussed in relation to their possible significance in the pattern of sperm transport, and it is suggested that the final negative pressure following female orgasm may effect an `insuck' of the cervical mucus with its entrapped spermatozoa.
When animals compete for copulations, large body size often implies high mating success. Small males may, however, compensate for their competitive disadvantage by special adaptive traits. This is the case in marine iguanas, iguanid reptiles of the Galapagos archipelago. In marine iguanas, females copulate only once per season. During copulations, males needed 2.8-3.1 min to initiate ejaculation. Large territorial males copulated long enough (more than 3.1 min) to achieve ejaculations in 95% of copulations, even when disturbed. Small males were separated from females by rival males in 29% of copulations before the start of ejaculation. Small males nevertheless fertilized females using prepared viable ejaculate, which was kept in readiness in hemipenis pouches and transferred into the female cloaca at intromission. This tactic increased the mating success of small males by 41%. This tactic demonstrates the adaptive significance of a trait which is functionally equivalent to non-ejaculatory `masturbation', and appears to be unique for vertebrates. However, similar phenomena have occasionally been observed, but mostly lacked functional explanation. An `ejaculation-in-advance' could occur in many taxa in which there is size-dominance hierarchy and sexual interference, but this remains to be determined.
Social behavior of the aoudad was studied in a free-ranging population during the rutting season. A total of 22 sexual and aggressive behavioral patterns was recorded among members of the various sex-age classes. The largest males (Class III) appropriated estrus females and courted them. Such females were defended by the dominant male in a group. Intensive combat among rival males, though rare, ensued when a dominant was challenged. Sparring and clashing were the predominant patterns used in such fights. Once a dominant established superiority over other members of the group he effectively chased away other males from an estrus female by horn-threatening or rushing at them. Class III males engaged in most sexual encounters with the females and possibly sired a large number of them. In the absence of Class III males in a group Class II rams actively participated in courtship. During courtship, the dominant ram maintained close contact with an estrus female and found little time to feed. Prior to mounting the male displayed ritualized patterns at the female by twisting and crouching at her repeatedly. Such behavior apparently seemed to concentrate the female’s attention to the male and led to copulation. The majority of behavioral patterns displayed by aoudads are common among sheep and goats with the exception of the crouch and stand not recorded among other members of the Caprini tribe. In aggressive behavior the aoudad seems to display forms which are similar to primitive sheep species such as neck-fighting, the tendency to wrestle the opponent down and clashing while on all four feet. Based on its behavioral characteristics the aoudad seems to occupy an intermediate position between the two main Caprini genera.
Social behavior of male Pacific walruses. Odobenus rosmarus (L.), summering (i.e. outside the breeding season) on an Alaskan hauling ground is described. Social interaction on land is mostly agonistic. Visual presentation of tusks and striking with tusks feature prominently in most agonistic interactions: vocal communication occurs in a minority of them. Agonistic interactions are analyzed in R- and Q-approaches with MIN1SSA, a fully non-metric multidimensional scaling procedure programmed in the Guttman-Lingoes series. Large body size and long tusks characterize dominant walruses. Dominants are most frequently aggressive and threatening, and least frequently exhibit submissive, defensive, protective, and avoidance behavior. Subordinate walruses show the opposite trend. Walruses are bullies; individuals strongly disadvantaged in body size or tusk length, or both, receive numerous strikes and visual threats. Walruses tend to initiate agonistic interactions with smaller individuals. Walrus tusks are importa...
Sexual pleasure is an innate component of human sexuality. Although disdained throughout history by religious groups and variably explained by theories, philosophers, and societies, sexual pleasure permeates human experience. Traditional evolutionists explain this preoccupation via the development of sexual mating strategies and the human desire to propagate one's genes; however, here I will argue that the saturation of sexual pleasure suggests that sexual activity is no longer pursued solely to ensure reproductive success. Rather, humans engage in sexual behavior to achieve sexual pleasure—a proposition supported by widespread non-procreative sex in mammals, divergent cultural norms, and humans' evolved capacity to experience heightened sexual pleasure. I will address the nature and evolution of sexual pleasure with a cross-cultural findings culled from ethology, anthropology, primatology, and evolutionary theories.
Sex is a fundamental pleasure, and crucial to the survival of our species. Though not many people would disagree with the proposition that sexual behaviour depends on the brain, the neuroscientific study of human sex is still relatively taboo and much remains to be discovered. On the contrary, excellent experimental animal models (mostly rat) are available that have uncovered major behavioural, neurochemical, and neuroanatomical characteristics of sexual behaviour. Restructuring sexual behaviour into broader terms reflecting behavioural states (wanting, liking, and inhibition) facilitates species comparison, revealing many similarities between animal and human sexual pleasure cycles, some of which can serve as potential avenues of new human sex research. In particular, behavioural and brain evidence clearly shows that motivational and consummatory phases are fundamentally distinct, and that genitally-induced sexual reward is a major factor in sexual learning mechanisms.
The behaviour of red deer stags following antler casting, antler breakage, antler amputation and antler stunting was studied to establish the ways in which antlers normally function. It was found that after the loss of antlers, either naturally or artificially, individuals became less effective in competition with other stags, resulting in loss of social rank in the bachelor group and failure to secure hinds in the rut.
The observations indicate that antlers normally function as a weapon and guard in conflict between stags and allow animals to lock their heads together for fighting. Of equal importance is the visual effect of the antlers denoting status of the individual, allowing for domination without physical force. While the stags are living in the bachelor herds the antlers appear to be the principal status symbol. During the rutting season, additional display symbols and characteristics come into use, and it is the significance of these in intimidation which allows stags without antlers (hummels) to be successful in the rut. There is slight evidence to support the idea that the antlers function in attracting hinds.
Guy's Hermit Phaethornis guy , a large forest hummingbird, was studied for 2 ¹ / 2 years in the Northern Range of Trinidad. Regular observations made at a lek of 16 males showed that leks are occupied from November until the beginning of July, and that individual birds retain their lek territories from year to year and use the same perches.
The usual song is a monosyllabic note regularly repeated, but the quality of the note varied between different leks and between different parts of a lek, and a few males had a disyllabic song. Young males join the lek between April and June and learn the song of their immediate neighbours. Their plumage, when they first join, is similar to a female's, with distinct pale super‐ and subciliary stripes. The acquisition of the dark head of the adult male probably takes four years.
Before they land on their lek perches, males perform an elaborate aerial display in which the red gape is flashed open and a loud tock is uttered. When males visit each other they rapidly change places on the lek perch, the airborne bird performing the tock‐display over the perched bird. A similar tock‐displaying with changing of place occurs when females visit males; twice these were seen to culminate in mounting. Periodically all males at the lek ‘false‐mate’ with a leaf or other piece of vegetation near their lek perches, after tock‐displaying above it. Young males false‐mate much more frequently than older males.
The breeding season lasts for eight months, the peak of breeding coinciding closely with the period when the two most important sources of nectar ( Heliconia bihai and Pachystachys coccinea ) are available. Males occasionally visit nests, and possibly assist in defending them. Undefended nests are quickly dismantled by other birds in search of nest‐material. Of 19 nests found before the clutch was complete, five (26%) were successful. The incubation period is 17–18 days, and the fledging period 21–23 days.
Details are given of the characteristics of the ovaries and testes of young and adult dolphins, Tursiops truncatus, all of which had been caught off Florida or Mississippi. Most had been in captivity for periods varying from a few days to ten years. Birth takes place most commonly during February to May and September to November. Length of neonates is between 98 and 126 cm. The state of activity of the gonads suggests that sexual maturity is reached in females at a length of over 220 cm and probably in their fifth year. Males do not become sexually active until about 260 cm in length and at an estimated age of at least ten years. Plasma testosterone levels are highest in a captive fertile male during April and May and October and November. The corpus luteum persists throughout the 12-month gestation period and also appears to persist as a corpus albicans for the dolphin's life span. The left ovary is usually larger than the right and twice as many corpora are found in the left as in the right ovary. No evidence of regular, cyclic ovulation is detected and it is concluded that ovulation is induced in Tursiops.
and Summary
1. The social structure of Cape mountain zebras consists of breeding herds and bachelor groups. The breeding herds, which comprise 1 stallion, 1–5 mares and their offspring, remain stable over many years. When the stallion is displaced by another the mares usually remain together, although some herds split up. A dominance hierarchy exists, but leadership is not confined to the dominant member. Foals leave their maternal herds at a mean age of 21.9 months. The herd stallion tries to prevent foals from leaving the herd.
2. Bachelor groups are not as rigidly structured as breeding herds but core groups could be identified through a Principal Components Analysis. Family ties may be important in the establishment of core groups. Bachelors succeed in becoming herd stallions when ca. 5 years old.
3. The recipient of a threat moving away seems to be an adequate response. Submissive behaviour was only recorded in bachelors. Fighting is rare, with biting as an important element. Compared to plains zebras, sounds made in communication are limited. Social grooming mainly occurs between mare and foal. Grooming intention movements may be an appeasement gesture.
4. An oestrus mare assumes a characteristic posture. Flehmen occurs. Urine and faeces of oestrus mares are often marked by the stallion. This cannot be explained functionally and is not restricted to eliminations of oestrus mares. Penis erection and jerking by resting stallions could serve as a warning signal, but may be masturbatory.
5. The herd stallion actively herds members of his herd and reduces intraherd antagonism by means of threats. He usually leads when the herd goes to drink and brings up the rear when the herd moves away from danger.
6. Play was rarely recorded.
7. A challenge ritual is performed when herd stallions meet. When challenged by a herd stallion, a bachelor is submissive.
8. Foals initially remain close to their mothers and have to learn the correct orientation when suckling. A single adoption was recorded.
9. Individuals apparently recognise each other after long periods.
10. Cape mountain zebras react to alarm signals of antelopes.
11. The greater part of the day is devoted to grazing. A significantly greater percentage of the day is spent resting in winter than in summer. Cape mountain zebras mainly stand while resting, but resting in sternal or lateral recumbency also occurs. Defaecation and urination occurs throughout the day with no definite peaks.
12. Grooming consists of localized muscle contractions, shaking, striking one part of the body against another or against the ground, rubbing, dust‐bathing, scratching and nibbling.
13. In cold weather, Cape mountain zebras seek shelter in wooded kloofs.
Zusammenfassung
Bergzebras bilden Familien und Junggesellengruppen. Familien bestehen aus einem Hengst, 1–5 Stuten und deren Nachwuchs. Harems bleiben jahrelang unverändert. Wird der Hengst verdrängt, so bleiben die Stuten meist zusammen. Es besteht eine Rangordnung, doch führt nicht nur das dominante Tier. Fohlen verlassen die Familie mit durchschnittlich 21,9 Monaten. Der Familienhengst versucht, die Fohlen am Weggehen zu hindern.
Junggesellengruppen sind nicht so fest strukturiert wie die Familien, doch lassen sich Kerngruppen durch Hauptkomponentenanalyse identifizieren. Familienbeziehungen können für das Entstehen soldier Kerngruppen wichtig sein. Junggesellen können im Alter von ungefähr 5 Jahren Familienhengste werden.
Flucht ist offenbar die ausreichende Reaktion auf Drohung. Unterwürfiges Verhalten wurde nur bei Junggesellen beobachtet. Kämpfe sieht man selten. Bergzebras haben weniger Kommunikationslaute als Steppenzebras. Soziale Hautpflege findet meist zwischen Stute und Fohlen statt. PflegeIntentionsbewegungen können zur Streitschlichtung benutzt werden.
Rossige Stuten nehmen eine charakteristische Stellung ein. Flehmen kommt vor. Harn und Kot rossiger Stuten werden oft vom Hengst markiert. Erektion des Penis mit Zuckungen beim ruhenden Hengst kann entweder als Warnsignal oder als Masturbation gedeutet werden.
Der Hengst herdet die Mitglieder seiner Familie und bremst innerfamiliäre Aggression durch Drohen. Gewöhnlich führt er die Familie zur Tränke und verläßt als Letzter die Gefahrenzone.
Spielen wurde selten beobachtet.
Wenn Familienhengste sich treffen, findet ein Herausforderungs‐Ritual statt. Junggesellen reagieren unterwürfig, wenn sie so herausgefordert werden.
Fohlen bleiben anfangs nahe bei der Mutter. Sie müssen die richtige Orientierung beim Säugen erlernen. Eine Adoption wurde registriert.
Individuen scheinen sich nach langer Zeit wiederzuerkennen.
Bergzebras reagieren auf die Alarmsignale von Antilopen.
Der größte Teil des Tages wird zum Grasen gebraucht. Im Winter gibt es signifikant längere Ruheperioden als im Sommer. Bergzebras ruhen meist stehend. Exkremente werden den ganzen Tag über ausgeschieden. Zur Körperpflege gehören örtliche Muskelkontraktionen, Schütteln, Schlagen eines Körperteils gegen einen anderen oder gegen den Boden, Reiben, Staubbaden, Kratzen und Knabbern.
Bei kaltem Wetter suchen Bergzebras in bewaldeten Schluchten Schutz.
I . Intrasexual seiection may have played a large part in insects in the evolution of copulation with internal fertilization from indirect spermatophore-transferring acts.
2. ‘Sperm competition’ may be defined as the competition within a single female between the sperm from two or more males over the fertilization of the ova.
3. There is considerable evidence from sperm-marking experiments that sperm competition is very common in insects as a result of multiple matings. Insects so far examined show that sperm from all inseminations can be used (to a varying extent) in the fertilization of subsequent offspring, but mating does not always result in successful insemination. In most cases (so far examined), the last male to mate tends to predominate in fertilizing the offspring.
4.Insects are preadapted to sustaining a very high level of sperm competition, compared with several other animal groups. The main preadaptations may be sum- marized as follows: (a)Females often mate several times within the duration of effec- tiveness of a given ejaculate. There may be several reasons for this. Though most usually females are unreceptive for some time after mating, some species appear ‘promiscuous’. Unreceptive females are also sometimes raped. Male persistence is sometimes prolonged, so that full female receptivity is advantageous. It is advan- tageous for a female to become receptive again when fertility first begins to decline; this is not when all the first ejaculate is used up. (b) Female insects typically possess specialized sperm storage organs in which sperm can be maintained in a viable condi- tion for a very long time, often until the death of the female. (c) Extremely efficient utilization of stored sperm at the time of fertilization appears to be an insect charac- teristic. In Drosophila the number of stored sperm virtually equals the possible number of fertilizations. Overlapping of effective ejaculates is therefore high. Second insemina- tions almost invariably reduce the fertility which would have been experienced by the first male to mate.
5. It is argued that this preadaptation to a very high level of sperm competition has led to intense intrasexual selective pressures on the male. In response to these pressures, two main lines of sexually selected adaptation are predicted: (a) towards mechanisms by which a male inseminates a female in such a way as to achieve pre- cedence over previously stored sperm and (b) accentuated by the above adaptation, mechanisms will evolve by which a male which mates with a given female will reduce the occurrence or success of subsequent inseminations with that female. These two forms of adaptation are diametrically opposed ; a high selective advantage would be gained by a male which superseded previous sperm and prevented any subsequent successful inseminations.
6. Several adaptations in male insects can be interpreted in the light of the above predictions, though many of these may also have other adaptive values through natural selection. The adaptation which evolves is not necessarily that which yields the maxi- mum possible egg gain to a given male (i.e. total sperm precedence), but that which results in the highest fertilization rate.
7. Sperm precedence is achieved in Drosophila by sperm displacement, where sperm from a second male predominate over previously stored sperm by directly displacing them from the sperm stores. Sperm displacement may occur in many insects.
8. Several behavioural and physiological adaptations of male insects may help to reduce the effectiveness, or occurrence of second inseminations of the same female by other males. These include : ( a ) Mating plugs (sphragis, spermat0phragmata)-male accessory gland secretions, usually transferred after insemination, which coagulate and form plugs within the female genital tract. Plugs may often serve to ‘guard’ the female until unreceptivity is initiated. In many insects, agents in the seminal fluid or male accessory gland secretions induce unreceptivity in the female. (b)Prolonged copu- lation-sometimes copulation takes much longer than seems necessary merely to transfer the sperm. This may have the same functions as that of a mating plug, but renders the male unfree to search for further females. (c) Passive phases (amplexus, tandem behaviour)-stages of the male’s reproductive behaviour during which he remains mounted on or otherwise attached to the female but without true genital contact between the two sexes. Postcopulatory passive phases sometimes serve to guard the female during oviposition where high densities of searching males are pre- valent. The postcopulatory passive phase of Scatophaga has an extremely high intra- sexual selective advantage which exceeds any apparent natural selective advantage by two orders of magnitude. (d)Non-contact guarding phases-reproductive behaviour phases during which the male remains close but not in contact with the female, guard- ing her from other males. Postcopulatory non-contact guarding phases appear to have the same selective advantage as postcopulatory passive phases.
9. Mechanisms to avoid ‘take-over ’ during copulation, passive, and non-contact guarding phases also serve to reduce sperm competition. These include increased efficiency of grasping apparatus, specialized rejection reactions which serve to dispel or ‘trick’ the recognition mechanism of the attacker, and emigrations from the site of highest probability of ‘take-over ’. There is quantitative evidence in Scatophaga that the emigration threshold of copulating males is determined by this form of intrasexual selective pressure.
10.Precopulatory passive phases may serve mainly to keep the sexes together until the female becomes receptive, but share several features in common with postcopula- tory passive phases. Territoriality of male insects may have arisen primarily through sexual selection as a mechanism by which a male guards an area into which a female is most likely to enter.