Animal sexuality
Encyclopedia
Animal sexual behaviour takes many different forms, even within the same species
. Among animal
s other than humans, researchers have observed monogamy
, promiscuity
, sex between species, sexual arousal from objects or places, sex apparently via duress or coercion
, copulation with dead animals
, homosexual
, heterosexual
and bisexual
sexual behaviour, situational sexual behaviour and a range of other practices. Related studies have noted diversity in sex
ed bodies and gender
ed behaviour, such as intersex
and transgender
animals.
The study of animal sexuality (and primate sexuality especially) is a rapidly developing field. It used to be believed that only humans and a handful of other species performed sexual acts other than for procreation, and that animals' sexuality was instinctive and a simple response to the "right" stimulation (sight, scent). Current understanding is that many species that were formerly believed monogamous have now been proven to be promiscuous or opportunistic in nature; a wide range of species appear both to masturbate and to use objects as tool
s to help them do so; in many species animals try to give and get sexual stimulation with others where procreation is not the aim; and homosexual behaviour has now been observed among 1,500 species and in 500 of those it is well documented.
and behavioural ecology, the term mating system
is used to describe the ways in which animal
societies are structured in relation to sexual behaviour. The mating system specifies which males mate with which females, and under what circumstances.
The following are some of the mating systems generally recognised in humans and other animals:
This includes previous examples such as swan
s. Sometimes these extra-pair sexual activities lead to offspring. Genetic tests frequently show that some of the offspring raised by a monogamous pair come from the female mating with an extra-pair male partner.
These discoveries have led biologists to adopt new ways of talking about monogamy:
Social monogamy is relatively rare in the animal kingdom. The actual incidence of social monogamy varies greatly across different branches of the evolutionary tree. Over 90 percent of avian species are socially monogamous.
This stands in contrast to mammals. Only 3 percent of mammalian species are socially monogamous, although up to 15 percent of primate species are socially monogamous. Social monogamy has also been observed in reptiles, fish, and insects.
Sexual monogamy is also rare among animals. Many socially monogamous species engage in extra-pair copulations, making them sexually non-monogamous. For example, while over 90% of birds are socially monogamous, "on average, 30 percent or more of the baby birds in any nest [are] sired by someone other than the resident male."
Patricia Adair Gowaty
has estimated that, out of 180 different species of socially monogamous songbirds, only 10% are sexually monogamous.
The incidence of genetic monogamy, determined by DNA fingerprinting, varies widely across species. For a few rare species, the incidence of genetic monogamy is 100 percent, with all offspring genetically related to the socially monogamous pair. But genetic monogamy is strikingly low in other species. Barash and Lipton note:
Such low levels of genetic monogamy have surprised biologists and zoologists, forcing them to rethink the role of social monogamy in evolution. They can no longer assume social monogamy determines how genes are distributed in a species. The lower the rates of genetic monogamy among socially monogamous pairs, the less of a role social monogamy plays in determining how genes are distributed among offspring. See also Evolution of monogamy
.
-like structures, only one of a few males in a group of females will mate. Technically, polygyny
in sociobiology and zoology is defined as a system in which a male has a relationships with more than one female, but the females are predominantly bonded to a single male. Should the active male be driven out, killed, or otherwise removed from the group, in a number of species the new male will ensure that breeding resources are not wasted on another male's young. The new male may achieve this in many different ways, including:
s. These species live in social groups consisting of several males and several females. Each female copulates with many males, and vice versa. In bonobos, the amount of promiscuity is particularly striking because bonobos use sex to alleviate social conflict as well as to reproduce.
). These are often associated with changes to herd or group structure, and behavioural changes, including territorialism amongst individuals. These may be annual (e.g. wolves), biannual (e.g. dogs) or more frequently (e.g. horses). During these periods, females of most species are more mentally and physically receptive to sexual advances, a period scientifically described as estrous but commonly described as being "in season" or "in heat", but outside them animals still engage in sexual behaviours, and such acts as do occur are not necessarily harmful. Certain other animals (opportunistic breeders
) breed dependent upon other conditions in their environment aside from time of year.
, with researchers either failing to observe or mis-categorizing and mis-describing sexual behaviour which does not meet their preconceptions. (See: Observer bias.) More current research provides views such as that of the Natural History Museum at the University of Oslo
, which in 2006 held an exhibition on animal sexuality:
An example of overlooking behaviour relates to descriptions of giraffe
mating:
Science cannot conclusively say at present what animals do or do not find "pleasurable", a question considered in more depth under Emotion in animals
. The urban myth website Snopes.com considers this particular view in depth. Its conclusions are broadly that the statement is true, but only using a very specific definition of "sex for pleasure", in which sexual acts tied to a reproductive cycle or for which an alternative explanation can be asserted, are ignored, as is all sexual activity that does not involve penetration. Animals put themselves at risk to engage in sex, and as a result, most species have evolved sexual signals (usually scent and behaviour) to indicate the presence of receptive periods. During these, sex is sought, and outside these it is usually not sought (or is sought but not permitted). Snopes comments that this is not in fact a reflection of whether sex is pleasurable or not, but rather a reflection of whether individuals have sex at arbitrary times. They conclude:
A 2006 Danish
Animal Ethics Council report which examined current knowledge of animal sexuality in the context of legal queries concerning sexual acts by humans, has the following comments, primarily related to domestically common animals:
For example, Petplace.com comments in its guide on assessing potential breeding stock purchases: "Masturbation is a normal behavior in all stallions that does not reduce semen production or performance in the breeding shed" Likewise a review from the University of Pennsylvania School of Veterinary Medicine
says:
Castration does not prevent masturbation, as it is observed in gelding
s. Masturbation is common in both mares and stallions, before and after puberty.
Sexologist Havelock Ellis
in his 1927 "Studies in the Psychology of Sex" identified bulls, goats, sheep, camels and elephants as species known to practice autoeroticism, adding of some other species:
In his 1999 book, Biological exuberance, Bruce Bagemihl
PhD documents (p. 71, 209–210) that:
and that:
Petter Bøckman of the Natural History Museum at the University of Oslo commented (in respect of a 2006 exhibition on homosexuality in the animal kingdom
) that:
and oral sex
. Although easily confused by lay-people, this is a separate and sexually oriented behaviour, distinct from non-sexual grooming
or the investigation of scents.
Auto-fellatio or oral sex in animals is documented in goat
s, primate
s, hyaena
s, bat
s and sheep (see section Masturbation for details).
and Robin Fox
conducted a study on how Depo-Provera contraceptives lead to decreased male attractiveness to females and eventually to male homosexuality. Janet E. Smith
summarizes the findings as follows:
The presence of same-sex sexual behaviour was not scientifically observed on a large scale until recent times. Homosexual behaviour does occur in the animal
kingdom outside humans, especially in social species, particularly in marine birds and mammals, monkeys, and the great apes
. Homosexual behaviour has been observed among 1,500 species, and in 500 of those it is well documented.
Georgetown University
professor Janet Mann has specifically theorised that homosexual behaviour, at least in dolphin
s, is an evolutionary advantage that minimizes intraspecies aggression, especially among males.
In the wild, where observation is harder, genetic studies have shown a "large number" of inter-species hybrids, and other investigations describe productive and non-productive inter-species mating as a "natural occurrence". Recent genetic evidence strongly suggesting this has occurred even within the history of the human
species, and that early humans often had sexual activity with other primate species, is considered below.
Hybrid offspring can result from two organisms of distinct but closely related parent species, although the resulting offspring is not always fertile
.
Due to the difficulties of observation, interspecies sex of this kind between two top-level predators, occurring in the wild, was only conclusively documented with the finding of a grizzly-polar bear hybrid
in April 2006. Again, as with lions and tigers, the two species would normally not share enough common territory to provide adequate opportunity for much cross-species sexual activity.
Animal sexual advances on, and attempted interactions with, humans and other species, have been documented by ethologists
such as Kohler
, Gerald Durrell
and Desmond Morris
, as well as authoritative researchers such as Birute Galdikas
who studied orangutan
s in Borneo
. Philosopher and animal welfare
activist Peter Singer
reports:
species, the females, even when in a committed relationship, will exchange sexual favours with strange males for the pebble
s they need to build their nest
s. Prostitution was also observed among chimpanzees, who trade food for sex.
Thus Gabriel, a chimpanzee at the Southwest National Primate Research Center, is said to have a shoe fetish (or possibly a leather fetish) according to caretaker Bert Barrera, and it is reported that:
The sexualization of objects or locations is also well recognized in the breeding world. So for example, stallion
s may often 'drop' (become sexually aroused
) upon visiting a location where they have been allowed to have sex before, or upon seeing a stimulus previously associated with sexual activity such as an artificial vagina
.
In this case however, the primary structure is Pavlovian conditioning, and the fetishistic association is due to a conditioned response (or association) formed with a distinctive 'reward'. Human fetishism can also be traced back to similar or near-identical conditioning: likewise based upon the Pavlovian association between an erotic sensation or anticipation, and objects which become mentally associated with that activity.
(reported in Current Biology
and online here ), showed that male monkeys will give up privileges (in this case, juice, which is highly valued), to be allowed to see a female monkey's hindquarters.
Deaner and his team reported that monkeys would take a juice cut to look at powerful males' faces or the perineum of a female, but to persuade the monkeys to stare at subordinate males, the researchers had to bribe them with larger drinks. "Virtually all [male] monkeys will give up juice to see female hindquarters ... they really value the images."
The researchers stress that in monkey society, such behaviours have great social utility and we should therefore not simply reach the conclusion that "monkeys enjoy pornographic pictures". There is no evidence at this point that viewable pictures or movies of sexual activity are valued for their sexual enjoyment, although as noted above (Masturbation), there are reports that watching sex in real life may have such an effect. The subject of animals and sexual imagery is not yet well researched.
Problems with encouraging panda
s to mate in captivity have been very common. However, showing young male pandas "panda pornography" is widely credited with a recent population boom among pandas in zoos.
), sex in a forceful or apparently coercive context has also been documented in a variety of species. A notable example is bottlenose dolphin
s, where at times, a pod of bachelor males
will 'corner' a female '...although what happens once the males have herded in a female, and whether she goes for one or all of them, is not yet known: the researchers have yet to witness a dolphin copulation.'
The behaviour is also common in some arachnid
s (spiders), notably those whose females eat the males during sex if not tricked with food and/or tied down with threads, and in some herbivorous
herd species or species where males and females are very different in size, where the male dominates sexually by sheer force and size.
Some species of birds appear to combine sexual intercourse with apparent violent assault; these include duck
s, geese, and white-fronted bee-eater
s. According to Emlen and Wrege (1986) forced copulations occur in this socially nesting species, and females must avoid the unwelcome attention of males as they emerge from their nest burrows or they are forced to the ground and mated with. Apparently, such attacks are made preferentially on females who are laying and who may thus mother their offspring as a result.
In 2007, research suggested that in the Acilius genus of water beetle
s (also known as "diving beetles"), an "evolutionary arms race
" between the genders means that there is no courtship system for these beetles. "It's a system of rape. But the females don't take things quietly. They evolve counter-weapons." Cited mating behaviours include males suffocating females underwater till exhausted, and allowing only occasional access to the surface to breathe for up to six hours (to prevent them breeding with other males), and females which have a variety of body shapings (to prevent males from gaining a grip). Foreplay is "limited to the female desperately trying to dislodge the male by swimming frantically around."
Charles Siebert reports in his New York Times article Elephant Crackup? that:
will impregnate newborns of their own species. It is not clear if this is forceful or not. Similarly, the male stoat
(Mustela erminea) will mate with infant females of their species. This apparently is a natural part of their reproductive biology – there is a delayed gestation period, so these females give birth the following year when they are fully grown.
A male spotted hyena which attempted to mate with a female which succeeded in driving it off, eventually turned to its ten-month-old cub, repeatedly mounting it and ejaculating on it. The cub sometimes ignored this and sometimes struggled 'slightly as if in play'. The mother did not intervene.
Infants and children in Bonobo
societies are often involved in sexual behaviour.
s, insect
s and amphipods, is a phenomenon in which a female organism kills and consumes the male before, during, or after copulation. Although it does confer some known advantages to reproduction, whether or not the male is complicit has not been scientifically determined.
in animals is where a living animal engages in a sexual act with a dead animal. In one of the most well-known examples, Kees Moeliker of the Rotterdam Natural History Museum
, Netherlands
observed sexual activities outside his office between a live duck
and a dead one. Two male mallards which Moeliker believed were engaged in rape flight, a common motif in duck sexual behaviour, collided with his window. "When one died the other one just went for it and didn't get any negative feedback—well, didn't get any feedback," according to Moeliker, who described the event as "homosexual necrophilia." The case was reported scientifically in Deinsea 8-2001, along with photos., and earned Moeliker an Ig Nobel Prize
in biology, awarded for research that cannot or should not be reproduced.
Additionally, male cane toad
s have been documented (in Cane Toads: An Unnatural History
) engaging in copulation with dead toads and inanimate objects.
, which has a matriarchal society, is a fully bisexual species — both males and females engage in sexual behaviour with the same and the opposite sex, with females being particularly noted for engaging in sexual behaviour with each other and at up to 75% of sexual activity being nonreproductive. Primatologist Frans de Waal believes that Bonobos use sexual activity to resolve conflict between individuals. Sexual activity occurs between almost all ages and sexes of Bonobo societies.
In early February 2004 the New York Times reported that a male pair of chinstrap penguin
s named Roy and Silo
in the Central Park Zoo
in New York City
were partnered and had successfully hatched a female chick from an egg.
Other penguins in New York have also been reported to be forming same-sex pairs.
Zoos in Japan
and Germany
have also documented male penguin couples. The couples have been shown to build nests together and use a stone to replace an egg in the nest. Researchers at Rikkyo University
in Tokyo
, found twenty such pairs at sixteen major aquariums and zoos in Japan. Bremerhaven Zoo in Germany attempted to break up the male couples by importing female penguins from Sweden
and separating the male couples; they were unsuccessful. The zoo director stated the relationships were too strong between the couples.
Recently, a mated pair of swan
s in Boston were found to both be female. They too had attempted to raise eggs together.
Studies have shown that ten to fifteen percent of female western gulls in some populations in the wild prefer other females.
As many as 19% of Mallard pairs in a given population have been observed to consist of male-male homosexuals.
females have the ability to reproduce through parthenogenesis
and as such males are rare and sexual breeding non-standard. Females engage in sexual behaviour to stimulate ovulation
, with their behaviour following their hormonal cycles; during low levels of estrogen, these (female) lizards engage in "masculine" sexual roles. Those animals with currently high estrogen levels assume "feminine" sexual roles.
Lizards that perform the courtship ritual have greater fecundity than those kept in isolation due to an increase in hormones triggered by the sexual behaviours. So, even though asexual whiptail lizards populations lack males, sexual stimuli still increase reproductive success.
From an evolutionary standpoint these females are passing their full genetic code to all of their offspring rather than the 50% of genes that would be passed in sexual reproduction. Certain species of gecko
also reproduce by parthenogenesis.
is a mating behaviour engaged in by certain species of flatworm
, such as Pseudobiceros bedfordi
. Species which engage in the practice are hermaphroditic, possessing both eggs and sperm-producing testes.
The species "fence" using two-headed dagger-like penises which are pointed, and white in color. One organism inseminates the other. The sperm is absorbed through pores in the skin, causing fertilization.
) states that homosexuality in male sheep (found in eight percent of rams) is associated with a region in the rams' brains which the authors call the "ovine Sexually Dimorphic Nucleus" (oSDN) which is half the size of the corresponding region in other male sheep.
However, some view this study to be flawed in that the determination of homosexuality within the sheep, (sample population of twenty-seven for the study), was to have animals who were unable to mount female ewes placed in a cage with two stanchioned males and two unstanchioned females (that is, the males could not move or struggle while the females could). Given the aggressive nature of the sheep copulation, the uneven treatment of males and females, many see this as simply evidence that the sheep in question were unable to be aggressive enough to mount females. Some say that the results were situational sexuality, unlike the bonds seen in human homosexuality.
The scientists found that, "The oSDN in rams that preferred females was significantly larger and contained more neurons than in male-oriented rams and ewes. In addition, the oSDN of the female-oriented rams expressed higher levels of aromatase
, a substance that converts testosterone
to estradiol
, an estrogen
hormone
believed to facilitate typical male sexual behaviours. Aromatase
expression was no different between male-oriented rams and ewes."
"The dense cluster of neurons that comprise the oSDN express cytochrome P450 aromatase. Aromatase mRNA levels in the oSDN were significantly greater in female-oriented rams than in ewes, whereas male-oriented rams exhibited intermediate levels of expression." These results suggest that "...naturally occurring variations in sexual partner preferences may be related to differences in brain anatomy and its capacity for estrogen synthesis." As noted previously, given the potential unagressiveness of the male population in question, the differing aromatase levels may also have been evidence of aggression levels, not sexuality. The results of this study have not been confirmed by others.
has a unique urinary-genital system, closely resembling the penis of the male, called a pseudo-penis
. The family structure is matriarchal and dominance relationships with strong sexual elements are routinely observed between related females.
They are notable for using visible sexual arousal as a sign of submission and not dominance, in males as well as females (females have a sizable erectile clitoris
), to the extent that biologist Robert Sapolsky
speculates that in order to facilitate this, their sympathetic
and parasympathetic nervous systems may be partially reversed in respect to their reproductive organs.
males have been observed working in pairs to follow and/or restrict the movement of a female for weeks at a time, waiting for her to become sexually receptive. The same pairs have also been observed engaging in intense sexual play with each other.
Janet Mann, a professor of biology and psychology at Georgetown University, argues that the common same-sex behaviour among male dolphin calves is about bond formation and benefits the species evolutionarily. They cite studies that have shown the dolphins later in life are bisexual and the male bonds forged from homosexuality work for protection as well as locating females with which to reproduce.
In 1991 an English man was prosecuted for allegedly having sexual contact with a dolphin. The man was found not guilty after it was revealed at trial that the dolphin was known to tow bathers through the water by hooking its large penis around them.
s, long upheld as monogamous and mating for life, are identified as "promiscuous, flighty, and more than a little bit gay" according to research published in 2007.
Scientists at 15 aquarium
s studied 90 seahorses of 3 species
. Of 3168 sexual encounters, 37% were same sex acts. Flirting was common (up to 25 potential partners a day of both genders); only one species (the British Spiny Seahorse) included faithful representatives, and for these 5 of 17 were faithful, 12 were not. Bisexuality was widespread and considered "both a great surprise and a shock", with big-bellied seahorses of both genders not showing partner preference. 1986 contacts were male-female, 836 were female-female and 346 were male-male.
s often lead their social groups jointly with one or more of their brothers. To ensure loyalty, the male co-leaders will "strengthen the bonds" by often having sex with each other.
There is also anecdotal evidence of limited bisexual behaviour in some stallions, although there is (as of 2008) no conclusive scientific confirmation. The anecdotal evidence claims this is most likely to occur in a single isolated group, with no access to mares.
s adopted an egg that had been abandoned by its biological parents. After the egg hatched, the two penguins raised, protected, cared for, and fed the chick in the same manner that heterosexual penguins raise their own biological offspring.
tends to confirm that in some cases, interspecies sexual activity may have been responsible for the evolution of entire new species. Analysis of human and animal gene
s in 2006 provides strong evidence that after human
s had diverged from other ape
s, interspecies mating nonetheless occurred regularly enough to change certain genes in the new gene pool
:
The research suggests that:
The Washington Post comments, "If this theory proves correct, it will mean modern people are descended from something akin to chimp-human hybrids."
With increasing published evidence of different types of sexual behaviour between animals, arguments for heterosexual monogamy in human society have moved towards characterizing these behaviours as resulting from differences between humans and animals, and in particular on ambiguity in motivation and subjective experience in animals, which is difficult to study. Arguments identifying human and animal behaviour are characterized as anthropomorphism
, and in some cases an opposite observer bias is attributed to researchers. Supporters of alternate sexuality embrace the new research as confirmation of the naturalness of alternate sexual behaviour and evidence of its long-term feasibility and utility.
In both cases, any argument that claims that something is good or right because it is natural, or that something is bad or wrong because it is unnatural or artificial is known as the appeal to nature
fallacy.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. Among animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s other than humans, researchers have observed monogamy
Monogamy
Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...
, promiscuity
Promiscuity
In humans, promiscuity refers to less discriminating casual sex with many sexual partners. The term carries a moral or religious judgement and is viewed in the context of the mainstream social ideal for sexual activity to take place within exclusive committed relationships...
, sex between species, sexual arousal from objects or places, sex apparently via duress or coercion
Rape
Rape is a type of sexual assault usually involving sexual intercourse, which is initiated by one or more persons against another person without that person's consent. The act may be carried out by physical force, coercion, abuse of authority or with a person who is incapable of valid consent. The...
, copulation with dead animals
Necrophilia
Necrophilia, also called thanatophilia or necrolagnia, is the sexual attraction to corpses,It is classified as a paraphilia by the Diagnostic and Statistical Manual of the American Psychiatric Association. The word is artificially derived from the ancient Greek words: νεκρός and φιλία...
, homosexual
Homosexuality
Homosexuality is romantic or sexual attraction or behavior between members of the same sex or gender. As a sexual orientation, homosexuality refers to "an enduring pattern of or disposition to experience sexual, affectional, or romantic attractions" primarily or exclusively to people of the same...
, heterosexual
Heterosexuality
Heterosexuality is romantic or sexual attraction or behavior between members of the opposite sex or gender. As a sexual orientation, heterosexuality refers to "an enduring pattern of or disposition to experience sexual, affectional, physical or romantic attractions to persons of the opposite sex";...
and bisexual
Bisexuality
Bisexuality is sexual behavior or an orientation involving physical or romantic attraction to both males and females, especially with regard to men and women. It is one of the three main classifications of sexual orientation, along with a heterosexual and a homosexual orientation, all a part of the...
sexual behaviour, situational sexual behaviour and a range of other practices. Related studies have noted diversity in sex
Sex
In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...
ed bodies and gender
Gender
Gender is a range of characteristics used to distinguish between males and females, particularly in the cases of men and women and the masculine and feminine attributes assigned to them. Depending on the context, the discriminating characteristics vary from sex to social role to gender identity...
ed behaviour, such as intersex
Intersex
Intersex, in humans and other animals, is the presence of intermediate or atypical combinations of physical features that usually distinguish female from male...
and transgender
Transgender
Transgender is a general term applied to a variety of individuals, behaviors, and groups involving tendencies to vary from culturally conventional gender roles....
animals.
The study of animal sexuality (and primate sexuality especially) is a rapidly developing field. It used to be believed that only humans and a handful of other species performed sexual acts other than for procreation, and that animals' sexuality was instinctive and a simple response to the "right" stimulation (sight, scent). Current understanding is that many species that were formerly believed monogamous have now been proven to be promiscuous or opportunistic in nature; a wide range of species appear both to masturbate and to use objects as tool
Tool
A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...
s to help them do so; in many species animals try to give and get sexual stimulation with others where procreation is not the aim; and homosexual behaviour has now been observed among 1,500 species and in 500 of those it is well documented.
Mating systems
In sociobiologySociobiology
Sociobiology is a field of scientific study which is based on the assumption that social behavior has resulted from evolution and attempts to explain and examine social behavior within that context. Often considered a branch of biology and sociology, it also draws from ethology, anthropology,...
and behavioural ecology, the term mating system
Mating system
A mating system is a way in which a group is structured in relation to sexual behaviour. The precise meaning depends upon the context. With respect to higher animals, it specifies which males mate with which females, under which circumstances; recognised animal mating systems include monogamy,...
is used to describe the ways in which animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
societies are structured in relation to sexual behaviour. The mating system specifies which males mate with which females, and under what circumstances.
The following are some of the mating systems generally recognised in humans and other animals:
- MonogamyMonogamyMonogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...
: One male and one female have an exclusive mating relationship. - PolygamyPolygamyPolygamy is a marriage which includes more than two partners...
: A single individual concurrently carries a relationship/mates with one or more of the opposite sex. Three types are recognized:- PolygynyPolygynyPolygyny is a form of marriage in which a man has two or more wives at the same time. In countries where the practice is illegal, the man is referred to as a bigamist or a polygamist...
(the most common polygamous mating system in vertebrates so far studied): One male has an exclusive relationship with two or more females. - PolyandryPolyandryPolyandry refers to a form of marriage in which a woman has two or more husbands at the same time. The form of polyandry in which a woman is married to two or more brothers is known as "fraternal polyandry", and it is believed by many anthropologists to be the most frequently encountered...
: One female has an exclusive relationship with two or more males. - PolygynandryPolygynandryPolygynandry occurs when two or more males have an exclusive relationship with two or more females. The numbers of males and females need not be equal, and in vertebrate species studied so far, the number of males is usually lower.-In Bonobos:...
: Two or more individuals have an exclusive relationship with two or more individuals from the opposite sex; the numbers of males and females need not be equal, and in vertebrate species studied so far, there are usually fewer males.
- Polygyny
- PromiscuityPromiscuityIn humans, promiscuity refers to less discriminating casual sex with many sexual partners. The term carries a moral or religious judgement and is viewed in the context of the mainstream social ideal for sexual activity to take place within exclusive committed relationships...
: Any male and female will mate within the social group.
Monogamy
Zoologists and biologists now have solid evidence that monogamous pairs of animals are not always sexually exclusive. Many animals that form pairs to mate and raise offspring regularly engage in sexual activities with extra-pair partners.This includes previous examples such as swan
Swan
Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae...
s. Sometimes these extra-pair sexual activities lead to offspring. Genetic tests frequently show that some of the offspring raised by a monogamous pair come from the female mating with an extra-pair male partner.
These discoveries have led biologists to adopt new ways of talking about monogamy:
Social monogamy
Whatever makes a pair of animals socially monogamous does not necessarily make them sexually or genetically monogamous. Social monogamy, sexual monogamy, and genetic monogamy can occur in different combinations.Social monogamy is relatively rare in the animal kingdom. The actual incidence of social monogamy varies greatly across different branches of the evolutionary tree. Over 90 percent of avian species are socially monogamous.
This stands in contrast to mammals. Only 3 percent of mammalian species are socially monogamous, although up to 15 percent of primate species are socially monogamous. Social monogamy has also been observed in reptiles, fish, and insects.
Sexual monogamy is also rare among animals. Many socially monogamous species engage in extra-pair copulations, making them sexually non-monogamous. For example, while over 90% of birds are socially monogamous, "on average, 30 percent or more of the baby birds in any nest [are] sired by someone other than the resident male."
Patricia Adair Gowaty
Patricia Adair Gowaty
Patricia Adair Gowaty is an American evolutionary biologist. She received her B.A. in biology at Tulane University and her PhD in zoology at Clemson University in 1980. She is currently a Distinguished Professor at the University of California, Los Angeles....
has estimated that, out of 180 different species of socially monogamous songbirds, only 10% are sexually monogamous.
The incidence of genetic monogamy, determined by DNA fingerprinting, varies widely across species. For a few rare species, the incidence of genetic monogamy is 100 percent, with all offspring genetically related to the socially monogamous pair. But genetic monogamy is strikingly low in other species. Barash and Lipton note:
Such low levels of genetic monogamy have surprised biologists and zoologists, forcing them to rethink the role of social monogamy in evolution. They can no longer assume social monogamy determines how genes are distributed in a species. The lower the rates of genetic monogamy among socially monogamous pairs, the less of a role social monogamy plays in determining how genes are distributed among offspring. See also Evolution of monogamy
Evolution of Monogamy
Monogamous pairing in animals refers to the natural history of mating systems in which species pair bond to raise offspring. This is associated, usually implicitly, with sexual monogamy.- Animals :...
.
Polygamy
Polygamy is defined as a mating structure in which a single individual of one gender has exclusive access to several individuals of the opposite gender. It takes two main forms – polygyny and polyandry. As polygyny is the most common form of polygamy among vertebrates (including humans, to some extent), it has been studied far more extensively than polyandry.Polygyny
In some species, notably those with haremHarem
Harem refers to the sphere of women in what is usually a polygynous household and their enclosed quarters which are forbidden to men...
-like structures, only one of a few males in a group of females will mate. Technically, polygyny
Polygyny
Polygyny is a form of marriage in which a man has two or more wives at the same time. In countries where the practice is illegal, the man is referred to as a bigamist or a polygamist...
in sociobiology and zoology is defined as a system in which a male has a relationships with more than one female, but the females are predominantly bonded to a single male. Should the active male be driven out, killed, or otherwise removed from the group, in a number of species the new male will ensure that breeding resources are not wasted on another male's young. The new male may achieve this in many different ways, including:
- Competitive infanticideInfanticide (zoology)In animals, infanticide involves the killing of young offspring by a mature animal of its own species, and is studied in zoology, specifically in the field of ethology. Ovicide is the analogous destruction of eggs. Although human infanticide has been widely studied, the practice has been observed...
- in lionLionThe lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...
s, hippopotamuses, and some monkeyMonkeyA monkey is a primate, either an Old World monkey or a New World monkey. There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys...
s, the new male will kill the offspring of the previous alpha male to cause their mothers to become receptive to his sexual advances since they are no longer nursingLactationLactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...
.- HarassmentHarassmentHarassment covers a wide range of behaviors of an offensive nature. It is commonly understood as behaviour intended to disturb or upset, and it is characteristically repetitive. In the legal sense, it is intentional behaviour which is found threatening or disturbing...
to miscarriageMiscarriageMiscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving independently, generally defined in humans at prior to 20 weeks of gestation...
- Harassment
- amongst wild horseHorseThe horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s and baboonBaboonBaboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. There are five species, which are some of the largest non-hominoid members of the primate order; only the mandrill and the drill are larger...
s, the male will "systematically harass" pregnant females until they miscarry.- PheromonePheromoneA pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
based spontaneous abortion
- Pheromone
- in some rodentRodentRodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s such as miceMouseA mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
, a new male with a different scent will cause females who are pregnant to spontaneously fail to implant recently fertilized eggs. This does not require contact; it is mediated by scent alone. It is known as the Bruce-Parkes effectBruce effectThe Bruce effect, or pregnancy block, refers to the tendency for female rodents to terminate their pregnancies following exposure to the scent of an unfamiliar male. The effect has primarily been studied in laboratory mice , but is also observed in deer-mice, meadow voles, and collared lemmings...
.
Promiscuity
Two examples of systems in primates are promiscuous mating chimpanzees and bonoboBonobo
The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...
s. These species live in social groups consisting of several males and several females. Each female copulates with many males, and vice versa. In bonobos, the amount of promiscuity is particularly striking because bonobos use sex to alleviate social conflict as well as to reproduce.
Seasonality
Many animal species have specific mating (or breeding) seasons (seasonal breedingSeasonal breeder
Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the births at a time optimal for the survival of the young in terms of factors such as temperature, food and water. Related sexual interest and behaviors are expressed...
). These are often associated with changes to herd or group structure, and behavioural changes, including territorialism amongst individuals. These may be annual (e.g. wolves), biannual (e.g. dogs) or more frequently (e.g. horses). During these periods, females of most species are more mentally and physically receptive to sexual advances, a period scientifically described as estrous but commonly described as being "in season" or "in heat", but outside them animals still engage in sexual behaviours, and such acts as do occur are not necessarily harmful. Certain other animals (opportunistic breeders
Opportunistic breeders
Flexible or opportunistic breeders mate whenever the conditions of their environment become favorable. Their ability and motivation to mate are primarily independent of day-length and instead rely on cues from short-term changes in local conditions like rainfall, food abundance and temperature...
) breed dependent upon other conditions in their environment aside from time of year.
Interpretation bias
The field of study of sexuality in non-human species has been a long standing tabooTaboo
A taboo is a strong social prohibition relating to any area of human activity or social custom that is sacred and or forbidden based on moral judgment, religious beliefs and or scientific consensus. Breaking the taboo is usually considered objectionable or abhorrent by society...
, with researchers either failing to observe or mis-categorizing and mis-describing sexual behaviour which does not meet their preconceptions. (See: Observer bias.) More current research provides views such as that of the Natural History Museum at the University of Oslo
Natural History Museum at the University of Oslo
The Natural History Museum at the University of Oslo is Norway's oldest and largest museum of natural history, situated in Oslo.It traces its roots to the University Botanical Garden, which was founded near Tøyen Manor in 1814...
, which in 2006 held an exhibition on animal sexuality:
An example of overlooking behaviour relates to descriptions of giraffe
Giraffe
The giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...
mating:
Sex for pleasure
It is a common myth that animals do not (as a rule) have sex for pleasure, or alternatively that humans, pigs (and perhaps dolphins and one or two species of primate) are the only species which do. This is sometimes formulated "animals mate only for reproduction".Science cannot conclusively say at present what animals do or do not find "pleasurable", a question considered in more depth under Emotion in animals
Emotion in animals
There is no scientific consensus on emotion in animals, that is, what emotions certain species of animals, including humans, feel. The debate concerns primarily mammals and birds, although emotions have also been postulated for other vertebrates and even for some invertebrates.Animal lovers,...
. The urban myth website Snopes.com considers this particular view in depth. Its conclusions are broadly that the statement is true, but only using a very specific definition of "sex for pleasure", in which sexual acts tied to a reproductive cycle or for which an alternative explanation can be asserted, are ignored, as is all sexual activity that does not involve penetration. Animals put themselves at risk to engage in sex, and as a result, most species have evolved sexual signals (usually scent and behaviour) to indicate the presence of receptive periods. During these, sex is sought, and outside these it is usually not sought (or is sought but not permitted). Snopes comments that this is not in fact a reflection of whether sex is pleasurable or not, but rather a reflection of whether individuals have sex at arbitrary times. They conclude:
- "Of course, we have to make many seemingly artificial distinctions to arrive at our conclusion. Animals other than humans have no awareness that their sexual activities are connected with reproduction: They engage in sex because they're biologically driven to do so, and if the fulfillment of their urges produces a physical sensation we might appropriately call 'pleasure,' it isn't the least bit affected by the possibility (or impossibility) of producing offspring. We are also discounting cases in which animals do engage in sex even though reproduction is an impossibility because we claim there are other 'purposes' (of which the animals themselves are unaware) at play. (For example, the females of some species of birds will invite males to mate with them even after they have laid their eggs, but we ascribe a purpose to this behaviour: this is a biological "trick" to fool males into caring for hatchlings they didn't father.) We also employ subjective terms such as 'willingly' and 'regularly' in claiming that bonobos and dolphins are the only other animals who "willingly (and regularly) engage in sex with each other" ... and even then it may be the case that these species have some other 'purpose' for doing so that we haven't yet discovered..."
A 2006 Danish
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
Animal Ethics Council report which examined current knowledge of animal sexuality in the context of legal queries concerning sexual acts by humans, has the following comments, primarily related to domestically common animals:
Autoeroticism or masturbation
It appears that many animals, both male and female, masturbate, both when partners are available and otherwise.For example, Petplace.com comments in its guide on assessing potential breeding stock purchases: "Masturbation is a normal behavior in all stallions that does not reduce semen production or performance in the breeding shed" Likewise a review from the University of Pennsylvania School of Veterinary Medicine
University of Pennsylvania School of Veterinary Medicine
The University of Pennsylvania School of Veterinary Medicine was founded in 1884. It has two campuses; the main campus is located in Philadelphia, and a second campus is located in Kennett Square, Pennsylvania. At the Philadelphia campus, first, second, and third year veterinary students attend...
says:
Castration does not prevent masturbation, as it is observed in gelding
Gelding
A gelding is a castrated horse or other equine such as a donkey or a mule. Castration, and the elimination of hormonally driven behavior associated with a stallion, allows a male horse to be calmer and better-behaved, making the animal quieter, gentler and potentially more suitable as an everyday...
s. Masturbation is common in both mares and stallions, before and after puberty.
Sexologist Havelock Ellis
Havelock Ellis
Henry Havelock Ellis, known as Havelock Ellis , was a British physician and psychologist, writer, and social reformer who studied human sexuality. He was co-author of the first medical textbook in English on homosexuality in 1897, and also published works on a variety of sexual practices and...
in his 1927 "Studies in the Psychology of Sex" identified bulls, goats, sheep, camels and elephants as species known to practice autoeroticism, adding of some other species:
In his 1999 book, Biological exuberance, Bruce Bagemihl
Bruce Bagemihl
Bruce Bagemihl is a Canadian biologist, linguist, and author of the book Biological Exuberance: Animal Homosexuality and Natural Diversity.-Life and career:He served on the faculty of University of British Columbia, and he earned a Ph.D...
PhD documents (p. 71, 209–210) that:
and that:
Petter Bøckman of the Natural History Museum at the University of Oslo commented (in respect of a 2006 exhibition on homosexuality in the animal kingdom
Against Nature?
Against Nature? is an exhibition on homosexuality in animals made by the Natural History Museum, University of Oslo, Norway. The exhibition focuses on occurrence and function of homosexuality in animals, and is the first of its kind....
) that:
Oral sex
Animals of several species are documented as engaging in both autofellatioAutofellatio
Autofellatio is the act of oral stimulation of one's own penis as a form of masturbation. It is physically possible for men who have sufficient flexibility, penis size or a combination of the two to perform autofellatio...
and oral sex
Oral sex
Oral sex is sexual activity involving the stimulation of the genitalia of a sex partner by the use of the mouth, tongue, teeth or throat. Cunnilingus refers to oral sex performed on females while fellatio refer to oral sex performed on males. Anilingus refers to oral stimulation of a person's anus...
. Although easily confused by lay-people, this is a separate and sexually oriented behaviour, distinct from non-sexual grooming
Social grooming
In social animals, including humans, social grooming or allogrooming is an activity in which individuals in a group clean or maintain one another's body or appearance. It is a major social activity, and a means by which animals who live in proximity can bond and reinforce social structures, family...
or the investigation of scents.
Auto-fellatio or oral sex in animals is documented in goat
Goat
The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...
s, primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
s, hyaena
Hyaena
For the Siouxsie and the Banshees album, see Hyæna.For the group of animals commonly known as "hyaena", see Hyena.Hyaena is a genus comprising two of the living species of hyenas: the striped hyena from western Asia and northern Africa and the brown hyena from southern Africa...
s, bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s and sheep (see section Masturbation for details).
Contraceptive Sex
Among monkeys, Lionel TigerLionel Tiger
Lionel Tiger is a Canadian-born, American-based anthropologist. He is the Charles Darwin Professor of Anthropology at Rutgers University and co-Research Director of the Harry Frank Guggenheim Foundation. He is a graduate of McGill University, and the London School of Economics at the University of...
and Robin Fox
Robin Fox
Robin Fox is an Anglo-American anthropologist who has written on the topics of marriage, human and primate kinship systems, and evolutionary anthropology and sociology. He was born in Yorkshire. He founded the department of anthropology at Rutgers University in 1967 and remained a professor there...
conducted a study on how Depo-Provera contraceptives lead to decreased male attractiveness to females and eventually to male homosexuality. Janet E. Smith
Janet E. Smith
Janet E. Smith is a professor of moral theology and the Fr. Michael J. McGivney Chair of Life Issues at the Sacred Heart Major Seminary in Detroit, Michigan. She previously taught at the University of Notre Dame, and the University of Dallas...
summarizes the findings as follows:
[The] study in the early 70s [...] involved a tribe of monkeys. The alpha monkey of this tribe, named Austin, chose three female monkeys to be his exclusive sexual partners. Austin had a grand time with these three female monkeys. Then the researchers injected Austin's three females with the contraceptive Depo-Provera. Austin stopped having sex with them and chose other female monkeys to be his sexual partners. Then they contracepted all of the females in the tribe. The males stopped having sex with the females and started behaving in a turbulent and confused manner.
Homosexual behaviour
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
kingdom outside humans, especially in social species, particularly in marine birds and mammals, monkeys, and the great apes
Hominidae
The Hominidae or include them .), as the term is used here, form a taxonomic family, including four extant genera: chimpanzees , gorillas , humans , and orangutans ....
. Homosexual behaviour has been observed among 1,500 species, and in 500 of those it is well documented.
Georgetown University
Georgetown University
Georgetown University is a private, Jesuit, research university whose main campus is in the Georgetown neighborhood of Washington, D.C. Founded in 1789, it is the oldest Catholic university in the United States...
professor Janet Mann has specifically theorised that homosexual behaviour, at least in dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s, is an evolutionary advantage that minimizes intraspecies aggression, especially among males.
- Male penguinPenguinPenguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...
couples have been documented to mate for life, build nests together, and to use a stone as a surrogate egg in nesting and brooding. In 2004, the Central Park ZooCentral Park ZooThe Central Park Zoo is a small zoo located in Central Park in New York City. It is part of an integrated system of four zoos and the New York Aquarium managed by the Wildlife Conservation Society , and is accredited by the Association of Zoos and Aquariums .The zoo began in the 1860s as a...
in the United StatesUnited StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
replaced one male couple's stone with a fertilized egg, which the couple then raised as their own offspring. GermanGermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
and JapanJapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese zooZooA zoological garden, zoological park, menagerie, or zoo is a facility in which animals are confined within enclosures, displayed to the public, and in which they may also be bred....
s have also reported homosexual behaviour among their penguins. This phenomenon has also been reported at Kelly Tarlton's Aquarium in AucklandAucklandThe Auckland metropolitan area , in the North Island of New Zealand, is the largest and most populous urban area in the country with residents, percent of the country's population. Auckland also has the largest Polynesian population of any city in the world...
, New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. "Humans have created the myth that sexuality can be justified only by reproduction, which by definition limits it to hetero sex," says Michael Bronski, author of The Pleasure Principle: Culture, Backlash, and the Struggle for Gay Freedom. "But here is an animal society that uses homosexuality to improve its social life." - Mounting of one female by another is common among cattleCattleCattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
. (See also, FreemartinFreemartinA freemartin or free-martin is an infertile female mammal which has masculinized behavior and non-functioning ovaries. Genetically and externally the animal is female, but it is sterilized in the womb by hormones from a male twin, becoming an infertile partial intersex...
. Freemartins occur because of clearly causal hormonal factors at work during gestation.) - BonoboBonoboThe bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...
s in zoos. After studying the primates for his book Bonobo: The Forgotten Ape, primatologist Frans de WaalFrans de WaalFransiscus Bernardus Maria de Waal, PhD , is a Dutch primatologist and ethologist. He is the Charles Howard Candler professor of Primate Behavior in the Emory University psychology department in Atlanta, Georgia, and director of the Living Links Center at the Yerkes National Primate Research...
, a professor of psychology at Emory University in Atlanta, says that such expressions of intimacy are consistent with the homosexual behaviour of what he terms "the erotic champions of the world." "Same-sex, opposite-sex — bonobos just love sex play," de Waal said in an interview. "They have so much sex, it gets boring." - Homosexual behaviour in male sheep (found in 6–10% of rams) is associated with variations in cerebral mass distribution and chemical activity. A study reported in EndocrinologyEndocrinology (journal)Endocrinology is a biomedical scientific journal published by The Endocrine Society. It is the Society's oldest journal and was first published in 1917. Dealing with the science of endocrinology among its topics are growth factors, steroids, the thyroid, and physiology...
concluded that biological and physiological factors are in effect. These findings are similar to human findings reported by Simon LeVaySimon LeVaySimon LeVay is a British-American neuroscientist. He is known for his studies about brain structures and sexual orientation.-Personal life:LeVay was born on August 28, 1943 in Oxford, England...
.
Approximately eight percent of [male] rams exhibit sexual preferences [that is, even when given a choice] for male partners (male-oriented rams) in contrast to most rams, which prefer female partners (female-oriented rams). We identified a cell group within the medial preoptic area/anterior hypothalamus of age-matched adult sheep that was significantly larger in adult rams than in ewes...
- Male bighorn sheep are divisible into two kinds: the typical males among whom homosexual behaviour, including intercourse, is common and "effeminate sheep", or "behavioural transvestites", which are not known to engage in homosexual behaviour.
Cross species sex
While it is commonly believed that animal sexuality is instinctive and thus somewhat mechanistic, research regularly records that many animals are sexual opportunists, partaking in sexual relations with individuals of visibly distinct species. This is more visible in domesticated species and animals in captivity, as domestication commonly selects for increased breeding rate (and so an accelerated breeding cycle has commonly arisen in domesticated species over the centuries), and also because these species are more easily observed by humans. Nevertheless, animals have been observed in the wild to attempt sexual activity with other species or indeed inanimate objects.In the wild, where observation is harder, genetic studies have shown a "large number" of inter-species hybrids, and other investigations describe productive and non-productive inter-species mating as a "natural occurrence". Recent genetic evidence strongly suggesting this has occurred even within the history of the human
Human
Humans are the only living species in the Homo genus...
species, and that early humans often had sexual activity with other primate species, is considered below.
Hybrid offspring can result from two organisms of distinct but closely related parent species, although the resulting offspring is not always fertile
Fertile
The term fertile describes a condition whereby organisms are able to produce physically healthy offspring.Fertile may also refer to:...
.
Due to the difficulties of observation, interspecies sex of this kind between two top-level predators, occurring in the wild, was only conclusively documented with the finding of a grizzly-polar bear hybrid
Grizzly-polar bear hybrid
A grizzly–polar bear hybrid is a rare ursid hybrid that has occurred both in captivity and in the wild. In 2006, the occurrence of this hybrid in nature was confirmed by testing the DNA for a strange-looking bear that had been shot near Sachs Harbour, Northwest Territories on Banks Island in the...
in April 2006. Again, as with lions and tigers, the two species would normally not share enough common territory to provide adequate opportunity for much cross-species sexual activity.
Animal sexual advances on, and attempted interactions with, humans and other species, have been documented by ethologists
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....
such as Kohler
Kohler
Kohler is a family name of German origin. The name was first found in Saxony. It means, "Charcoal burner" so the first "Kohlers" were most likely of that occupation.-People:*Alan Kohler, Australian journalist*Herbert Kohler, Jr., businessman...
, Gerald Durrell
Gerald Durrell
Gerald "Gerry" Malcolm Durrell, OBE was a naturalist, zookeeper, conservationist, author and television presenter...
and Desmond Morris
Desmond Morris
Desmond John Morris, born 24 January 1928 in Purton, north Wiltshire, is a British zoologist and ethologist, as well as a popular anthropologist. He is also known as a painter, television presenter and popular author.-Life:...
, as well as authoritative researchers such as Birute Galdikas
Birute Galdikas
Birutė Marija Filomena Galdikas, OC , is a primatologist, conservationist, ethologist, and author of several books relating to the endangered orangutan, particularly the Bornean orangutan. Well known in the field of modern primatology, Galdikas is recognized as a leading authority on orangutans...
who studied orangutan
Orangutan
Orangutans are the only exclusively Asian genus of extant great ape. The largest living arboreal animals, they have proportionally longer arms than the other, more terrestrial, great apes. They are among the most intelligent primates and use a variety of sophisticated tools, also making sleeping...
s in Borneo
Borneo
Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....
. Philosopher and animal welfare
Animal welfare
Animal welfare is the physical and psychological well-being of animals.The term animal welfare can also mean human concern for animal welfare or a position in a debate on animal ethics and animal rights...
activist Peter Singer
Peter Singer
Peter Albert David Singer is an Australian philosopher who is the Ira W. DeCamp Professor of Bioethics at Princeton University and Laureate Professor at the Centre for Applied Philosophy and Public Ethics at the University of Melbourne...
reports:
Prostitution
In some penguinPenguin
Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...
species, the females, even when in a committed relationship, will exchange sexual favours with strange males for the pebble
Pebble
A pebble is a clast of rock with a particle size of 4 to 64 millimetres based on the Krumbein phi scale of sedimentology. Pebbles are generally considered to be larger than granules and smaller than cobbles . A rock made predominantly of pebbles is termed a conglomerate...
s they need to build their nest
Nest
A nest is a place of refuge to hold an animal's eggs or provide a place to live or raise offspring. They are usually made of some organic material such as twigs, grass, and leaves; or may simply be a depression in the ground, or a hole in a tree, rock or building...
s. Prostitution was also observed among chimpanzees, who trade food for sex.
Sexual fetishes
Although not often reported, animals, or primates at the least, are able to sexualize inanimate objects similar to the way human beings sexualize the objects of their sexual fetishes. Not only will an animal that has a habitual object for masturbation sometimes appear to sexualize that object, primates have generalized further to sexualize kinds of objects for which no instinctual or prior sexual connection exists.Thus Gabriel, a chimpanzee at the Southwest National Primate Research Center, is said to have a shoe fetish (or possibly a leather fetish) according to caretaker Bert Barrera, and it is reported that:
The sexualization of objects or locations is also well recognized in the breeding world. So for example, stallion
Stallion (horse)
A stallion is a male horse that has not been gelded .Stallions will follow the conformation and phenotype of their breed, but within that standard, the presence of hormones such as testosterone may give stallions a thicker, "cresty" neck, as well as a somewhat more muscular physique as compared to...
s may often 'drop' (become sexually aroused
Sexual arousal
Sexual arousal, or sexual excitement, is the arousal of sexual desire, during or in anticipation of sexual activity. Things that precipitate human sexual arousal are called erotic stimuli, or colloquially known as turn-ons. There are many potential stimuli, both physical or mental, which can cause...
) upon visiting a location where they have been allowed to have sex before, or upon seeing a stimulus previously associated with sexual activity such as an artificial vagina
Artificial vagina
An artificial vagina is a device designed to imitate the female sex organ. To achieve this, it will generally be made of a soft material, lubricated, and sometimes heated...
.
In this case however, the primary structure is Pavlovian conditioning, and the fetishistic association is due to a conditioned response (or association) formed with a distinctive 'reward'. Human fetishism can also be traced back to similar or near-identical conditioning: likewise based upon the Pavlovian association between an erotic sensation or anticipation, and objects which become mentally associated with that activity.
Sexual imagery viewing
A study by Platt, Khera and Deaner at Duke UniversityDuke University
Duke University is a private research university located in Durham, North Carolina, United States. Founded by Methodists and Quakers in the present day town of Trinity in 1838, the school moved to Durham in 1892. In 1924, tobacco industrialist James B...
(reported in Current Biology
Current Biology
Current Biology is a scientific journal that covers all areas of biology, especially molecular biology, cell biology, genetics, neurobiology, ecology and evolutionary biology. The journal is published twice a month and includes peer-reviewed research articles, various types of review articles, as...
and online here ), showed that male monkeys will give up privileges (in this case, juice, which is highly valued), to be allowed to see a female monkey's hindquarters.
Deaner and his team reported that monkeys would take a juice cut to look at powerful males' faces or the perineum of a female, but to persuade the monkeys to stare at subordinate males, the researchers had to bribe them with larger drinks. "Virtually all [male] monkeys will give up juice to see female hindquarters ... they really value the images."
The researchers stress that in monkey society, such behaviours have great social utility and we should therefore not simply reach the conclusion that "monkeys enjoy pornographic pictures". There is no evidence at this point that viewable pictures or movies of sexual activity are valued for their sexual enjoyment, although as noted above (Masturbation), there are reports that watching sex in real life may have such an effect. The subject of animals and sexual imagery is not yet well researched.
Problems with encouraging panda
Panda
Panda or Panda bear most often refers to:*Giant panda, an animal in the Bear familyPanda may also refer to:*Red panda, the only living member in the Ailuridae family-In biology:* Species related to the Giant panda...
s to mate in captivity have been very common. However, showing young male pandas "panda pornography" is widely credited with a recent population boom among pandas in zoos.
Coercive sex
Controversial interpretations and implications aside (see Sociobiological theories of rapeSociobiological theories of rape
Sociobiological theories of rape are theories that explore to what degree, if any, evolutionary adaptations influence the psychology of rapists. Such theories are highly controversial, as traditional theories typically do not consider rape to be a behavioral adaptation. Some object to such theories...
), sex in a forceful or apparently coercive context has also been documented in a variety of species. A notable example is bottlenose dolphin
Bottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
s, where at times, a pod of bachelor males
Bachelor herd
A bachelor herd is a gathering of juvenile male animals who are still sexually immature, or of 'harem'-forming animals who have been thrown out of their parent groups but not yet formed a new family group....
will 'corner' a female '...although what happens once the males have herded in a female, and whether she goes for one or all of them, is not yet known: the researchers have yet to witness a dolphin copulation.'
The behaviour is also common in some arachnid
Arachnid
Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...
s (spiders), notably those whose females eat the males during sex if not tricked with food and/or tied down with threads, and in some herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
herd species or species where males and females are very different in size, where the male dominates sexually by sheer force and size.
Duck
Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...
s, geese, and white-fronted bee-eater
White-fronted Bee-eater
The White-fronted Bee-eater, Merops bullockoides, is a species of bee-eater widely distributed in sub-equatorial Africa.They have a distinctive white forehead, a square tail and a bright red patch on their throat...
s. According to Emlen and Wrege (1986) forced copulations occur in this socially nesting species, and females must avoid the unwelcome attention of males as they emerge from their nest burrows or they are forced to the ground and mated with. Apparently, such attacks are made preferentially on females who are laying and who may thus mother their offspring as a result.
In 2007, research suggested that in the Acilius genus of water beetle
Water beetle
A water beetle is a beetle adapted to living in water. Water beetles rise to the water surface and take atmospheric air into their tracheal systems. There are approximately 2000 species of water beetles. The rest marine species tend to live in the intertidal zone...
s (also known as "diving beetles"), an "evolutionary arms race
Evolutionary arms race
In evolutionary biology, an evolutionary arms race is an evolutionary struggle between competing sets of co-evolving genes that develop adaptations and counter-adaptations against each other, resembling an arms race, which are also examples of positive feedback...
" between the genders means that there is no courtship system for these beetles. "It's a system of rape. But the females don't take things quietly. They evolve counter-weapons." Cited mating behaviours include males suffocating females underwater till exhausted, and allowing only occasional access to the surface to breathe for up to six hours (to prevent them breeding with other males), and females which have a variety of body shapings (to prevent males from gaining a grip). Foreplay is "limited to the female desperately trying to dislodge the male by swimming frantically around."
Charles Siebert reports in his New York Times article Elephant Crackup? that:
Sex between adults and juveniles
It has also been recorded that certain species of moleMole (animal)
Moles are small cylindrical mammals adapted to a subterranean lifestyle. They have velvety fur; tiny or invisible ears and eyes; and short, powerful limbs with large paws oriented for digging. The term is especially and most properly used for the true moles, those of the Talpidae family in the...
will impregnate newborns of their own species. It is not clear if this is forceful or not. Similarly, the male stoat
Stoat
The stoat , also known as the ermine or short-tailed weasel, is a species of Mustelid native to Eurasia and North America, distinguished from the least weasel by its larger size and longer tail with a prominent black tip...
(Mustela erminea) will mate with infant females of their species. This apparently is a natural part of their reproductive biology – there is a delayed gestation period, so these females give birth the following year when they are fully grown.
A male spotted hyena which attempted to mate with a female which succeeded in driving it off, eventually turned to its ten-month-old cub, repeatedly mounting it and ejaculating on it. The cub sometimes ignored this and sometimes struggled 'slightly as if in play'. The mother did not intervene.
Infants and children in Bonobo
Bonobo
The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...
societies are often involved in sexual behaviour.
Sexual cannibalism
Sexual cannibalism, which has been documented in arachnidArachnid
Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...
s, insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s and amphipods, is a phenomenon in which a female organism kills and consumes the male before, during, or after copulation. Although it does confer some known advantages to reproduction, whether or not the male is complicit has not been scientifically determined.
Necrophilia
NecrophiliaNecrophilia
Necrophilia, also called thanatophilia or necrolagnia, is the sexual attraction to corpses,It is classified as a paraphilia by the Diagnostic and Statistical Manual of the American Psychiatric Association. The word is artificially derived from the ancient Greek words: νεκρός and φιλία...
in animals is where a living animal engages in a sexual act with a dead animal. In one of the most well-known examples, Kees Moeliker of the Rotterdam Natural History Museum
Natuurhistorisch Museum Rotterdam
The ' is a natural history museum at Museumpark in Rotterdam, The Netherlands.The museum is located in the Villa Dijkzigt, dating from 1852 and extended in 1995 with a modern glazed pavilion which was designed by the Dutch architect Erick van Egeraat. Villa Dijkzigt was originally built by J. F...
, Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
observed sexual activities outside his office between a live duck
Duck
Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...
and a dead one. Two male mallards which Moeliker believed were engaged in rape flight, a common motif in duck sexual behaviour, collided with his window. "When one died the other one just went for it and didn't get any negative feedback—well, didn't get any feedback," according to Moeliker, who described the event as "homosexual necrophilia." The case was reported scientifically in Deinsea 8-2001, along with photos., and earned Moeliker an Ig Nobel Prize
Ig Nobel Prize
The Ig Nobel Prizes are an American parody of the Nobel Prizes and are given each year in early October for ten unusual or trivial achievements in scientific research. The stated aim of the prizes is to "first make people laugh, and then make them think"...
in biology, awarded for research that cannot or should not be reproduced.
Additionally, male cane toad
Cane Toad
The Cane Toad , also known as the Giant Neotropical Toad or Marine Toad, is a large, terrestrial true toad which is native to Central and South America, but has been introduced to various islands throughout Oceania and the Caribbean...
s have been documented (in Cane Toads: An Unnatural History
Cane Toads: An Unnatural History
Cane Toads: An Unnatural History is a 47-minute documentary film about the introduction of Cane Toads to Australia. Cane Toads were introduced to Australia with the aim of controlling a sugar cane pest, but they over-multiplied and became a serious problem in the Australian ecosystem...
) engaging in copulation with dead toads and inanimate objects.
Bonobos
The BonoboBonobo
The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...
, which has a matriarchal society, is a fully bisexual species — both males and females engage in sexual behaviour with the same and the opposite sex, with females being particularly noted for engaging in sexual behaviour with each other and at up to 75% of sexual activity being nonreproductive. Primatologist Frans de Waal believes that Bonobos use sexual activity to resolve conflict between individuals. Sexual activity occurs between almost all ages and sexes of Bonobo societies.
Birds
Some black swans of Australia form sexually active male-male mated pairs and steal nests, or form temporary threesomes with females to obtain eggs, driving away the female after she lays the eggs. More of their cygnets survive to adulthood than those of different-sex pairs possibly due to their superior ability to defend large portions of land.In early February 2004 the New York Times reported that a male pair of chinstrap penguin
Chinstrap Penguin
The Chinstrap Penguin is a species of penguin which is found in the South Sandwich Islands, Antarctica, the South Orkneys, South Shetland, South Georgia, Bouvet Island and Balleny...
s named Roy and Silo
Roy and Silo
Roy and Silo are Chinstrap Penguins who were a male-male pair in New York City's Central Park Zoo.Roy and Silo met at the zoo and they began their relationship in 2004. The pair were observed trying to hatch a rock as if it were an egg. They also attempted to steal eggs from other penguin couples...
in the Central Park Zoo
Central Park Zoo
The Central Park Zoo is a small zoo located in Central Park in New York City. It is part of an integrated system of four zoos and the New York Aquarium managed by the Wildlife Conservation Society , and is accredited by the Association of Zoos and Aquariums .The zoo began in the 1860s as a...
in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
were partnered and had successfully hatched a female chick from an egg.
Other penguins in New York have also been reported to be forming same-sex pairs.
Zoos in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
have also documented male penguin couples. The couples have been shown to build nests together and use a stone to replace an egg in the nest. Researchers at Rikkyo University
Rikkyo University
, also known as Saint Paul's University, is a private university, based on Christian precepts, in Ikebukuro, Tokyo. There is a suburban campus in Niiza in nearby Saitama.It is known for its liberal climate symbolized by the motto -History:...
in Tokyo
Tokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...
, found twenty such pairs at sixteen major aquariums and zoos in Japan. Bremerhaven Zoo in Germany attempted to break up the male couples by importing female penguins from Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
and separating the male couples; they were unsuccessful. The zoo director stated the relationships were too strong between the couples.
Recently, a mated pair of swan
Swan
Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae...
s in Boston were found to both be female. They too had attempted to raise eggs together.
Studies have shown that ten to fifteen percent of female western gulls in some populations in the wild prefer other females.
As many as 19% of Mallard pairs in a given population have been observed to consist of male-male homosexuals.
Lizards
Whip-tailed lizardCnemidophorus
Cnemidophorus is a genus of lizards which belong to the family of Teiidae, which are commonly referred to as whiptail lizards or racerunners. Note that the nomenclature for this genus has recently been re-examined by T. W. Reeder et al. in 2002...
females have the ability to reproduce through parthenogenesis
Parthenogenesis
Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...
and as such males are rare and sexual breeding non-standard. Females engage in sexual behaviour to stimulate ovulation
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...
, with their behaviour following their hormonal cycles; during low levels of estrogen, these (female) lizards engage in "masculine" sexual roles. Those animals with currently high estrogen levels assume "feminine" sexual roles.
Lizards that perform the courtship ritual have greater fecundity than those kept in isolation due to an increase in hormones triggered by the sexual behaviours. So, even though asexual whiptail lizards populations lack males, sexual stimuli still increase reproductive success.
From an evolutionary standpoint these females are passing their full genetic code to all of their offspring rather than the 50% of genes that would be passed in sexual reproduction. Certain species of gecko
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....
also reproduce by parthenogenesis.
Flatworm
Penis fencingPenis fencing
Penis fencing is a mating behavior engaged in by certain species of flatworm, such as Pseudobiceros hancockanus. Species which engage in the practice are hermaphroditic; each individual has both egg-producing ovaries and sperm-producing testes....
is a mating behaviour engaged in by certain species of flatworm
Flatworm
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...
, such as Pseudobiceros bedfordi
Pseudobiceros bedfordi
Pseudobiceros bedfordi, is a species of flatworm in the family Pseudocerotidae....
. Species which engage in the practice are hermaphroditic, possessing both eggs and sperm-producing testes.
The species "fence" using two-headed dagger-like penises which are pointed, and white in color. One organism inseminates the other. The sperm is absorbed through pores in the skin, causing fertilization.
Sheep
An October 2003, study by Dr. Charles E. Roselli et al. (Oregon Health & Science UniversityOregon Health & Science University
Oregon Health & Science University is a public university in Oregon with a main campus, including two hospitals, in Portland and a smaller campus in Hillsboro...
) states that homosexuality in male sheep (found in eight percent of rams) is associated with a region in the rams' brains which the authors call the "ovine Sexually Dimorphic Nucleus" (oSDN) which is half the size of the corresponding region in other male sheep.
However, some view this study to be flawed in that the determination of homosexuality within the sheep, (sample population of twenty-seven for the study), was to have animals who were unable to mount female ewes placed in a cage with two stanchioned males and two unstanchioned females (that is, the males could not move or struggle while the females could). Given the aggressive nature of the sheep copulation, the uneven treatment of males and females, many see this as simply evidence that the sheep in question were unable to be aggressive enough to mount females. Some say that the results were situational sexuality, unlike the bonds seen in human homosexuality.
The scientists found that, "The oSDN in rams that preferred females was significantly larger and contained more neurons than in male-oriented rams and ewes. In addition, the oSDN of the female-oriented rams expressed higher levels of aromatase
Aromatase
Aromatase is an enzyme responsible for a key step in the biosynthesis of estrogens. It is a member of the cytochrome P450 superfamily , which are monooxygenases that catalyze many reactions involved in steroidogenesis. In particular, aromatase is responsible for the aromatization of androgens into...
, a substance that converts testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...
to estradiol
Estradiol
Estradiol is a sex hormone. Estradiol is abbreviated E2 as it has 2 hydroxyl groups in its molecular structure. Estrone has 1 and estriol has 3 . Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect...
, an estrogen
Estrogen
Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...
hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
believed to facilitate typical male sexual behaviours. Aromatase
Aromatase
Aromatase is an enzyme responsible for a key step in the biosynthesis of estrogens. It is a member of the cytochrome P450 superfamily , which are monooxygenases that catalyze many reactions involved in steroidogenesis. In particular, aromatase is responsible for the aromatization of androgens into...
expression was no different between male-oriented rams and ewes."
"The dense cluster of neurons that comprise the oSDN express cytochrome P450 aromatase. Aromatase mRNA levels in the oSDN were significantly greater in female-oriented rams than in ewes, whereas male-oriented rams exhibited intermediate levels of expression." These results suggest that "...naturally occurring variations in sexual partner preferences may be related to differences in brain anatomy and its capacity for estrogen synthesis." As noted previously, given the potential unagressiveness of the male population in question, the differing aromatase levels may also have been evidence of aggression levels, not sexuality. The results of this study have not been confirmed by others.
Spotted Hyena
The female Spotted HyenaSpotted Hyena
The spotted hyena also known as laughing hyena, is a carnivorous mammal of the family Hyaenidae, of which it is the largest extant member. Though the species' prehistoric range included Eurasia extending from Atlantic Europe to China, it now only occurs in all of Africa south of the Sahara save...
has a unique urinary-genital system, closely resembling the penis of the male, called a pseudo-penis
Pseudo-penis
A pseudo-penis is a term used of any structure found on an animal that while superficially appearing to be a penis, is derived from a different developmental path.-Mammals:...
. The family structure is matriarchal and dominance relationships with strong sexual elements are routinely observed between related females.
They are notable for using visible sexual arousal as a sign of submission and not dominance, in males as well as females (females have a sizable erectile clitoris
Clitoris
The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...
), to the extent that biologist Robert Sapolsky
Robert Sapolsky
Robert Maurice Sapolsky is an American scientist and author. He is currently Professor of Biological Sciences, and Professor of Neurology and Neurological Sciences and, by courtesy, Neurosurgery, at Stanford University. In addition, he is a Research Associate at the National Museums of...
speculates that in order to facilitate this, their sympathetic
Sympathetic nervous system
The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...
and parasympathetic nervous systems may be partially reversed in respect to their reproductive organs.
Bottlenose Dolphins
Bottlenose DolphinBottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
males have been observed working in pairs to follow and/or restrict the movement of a female for weeks at a time, waiting for her to become sexually receptive. The same pairs have also been observed engaging in intense sexual play with each other.
Janet Mann, a professor of biology and psychology at Georgetown University, argues that the common same-sex behaviour among male dolphin calves is about bond formation and benefits the species evolutionarily. They cite studies that have shown the dolphins later in life are bisexual and the male bonds forged from homosexuality work for protection as well as locating females with which to reproduce.
In 1991 an English man was prosecuted for allegedly having sexual contact with a dolphin. The man was found not guilty after it was revealed at trial that the dolphin was known to tow bathers through the water by hooking its large penis around them.
Seahorses
SeahorseSeahorse
Seahorses compose the fish genus Hippocampus within the family Syngnathidae, in order Syngnathiformes. Syngnathidae also includes the pipefishes. "Hippocampus" comes from the Ancient Greek hippos meaning "horse" and kampos meaning “sea monster”.There are nearly 50 species of seahorse...
s, long upheld as monogamous and mating for life, are identified as "promiscuous, flighty, and more than a little bit gay" according to research published in 2007.
Scientists at 15 aquarium
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
s studied 90 seahorses of 3 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. Of 3168 sexual encounters, 37% were same sex acts. Flirting was common (up to 25 potential partners a day of both genders); only one species (the British Spiny Seahorse) included faithful representatives, and for these 5 of 17 were faithful, 12 were not. Bisexuality was widespread and considered "both a great surprise and a shock", with big-bellied seahorses of both genders not showing partner preference. 1986 contacts were male-female, 836 were female-female and 346 were male-male.
Lions
Male lionLion
The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...
s often lead their social groups jointly with one or more of their brothers. To ensure loyalty, the male co-leaders will "strengthen the bonds" by often having sex with each other.
Horses
Anecdotal evidence suggest that some horses have environment or appearance preferences when selecting mates.There is also anecdotal evidence of limited bisexual behaviour in some stallions, although there is (as of 2008) no conclusive scientific confirmation. The anecdotal evidence claims this is most likely to occur in a single isolated group, with no access to mares.
Humboldt penguins
In 2009 at a zoo in Bremerhaven, Germany, two male adult humboldt penguinHumboldt Penguin
The Humboldt Penguin is a South American penguin, that breeds in coastal Peru and Chile. Its nearest relatives are the African Penguin, the Magellanic Penguin and the Galápagos Penguin...
s adopted an egg that had been abandoned by its biological parents. After the egg hatched, the two penguins raised, protected, cared for, and fed the chick in the same manner that heterosexual penguins raise their own biological offspring.
Other evidence of interspecies sexual activity
Looking back in history, current research into human evolutionHuman evolution
Human evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...
tends to confirm that in some cases, interspecies sexual activity may have been responsible for the evolution of entire new species. Analysis of human and animal gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s in 2006 provides strong evidence that after human
Human
Humans are the only living species in the Homo genus...
s had diverged from other ape
Ape
Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...
s, interspecies mating nonetheless occurred regularly enough to change certain genes in the new gene pool
Gene pool
In population genetics, a gene pool is the complete set of unique alleles in a species or population.- Description :A large gene pool indicates extensive genetic diversity, which is associated with robust populations that can survive bouts of intense selection...
:
The research suggests that:
The Washington Post comments, "If this theory proves correct, it will mean modern people are descended from something akin to chimp-human hybrids."
Role in discussion of human sexuality
Information about animal sexuality frequently arises as a persuasive device in arguments regarding human sexuality. Originally, the lack of documented animal sexual behaviour deviant from heterosexual sexual monogamy was used to argue that the dominant heterosexual monogamy of most modern human societies is more natural and acceptable. Likewise, the lack of documented sex between animals for the purpose of pleasure was used to promote the moral standard of reserving sex primarily for procreation. Proponents of alternate sexuality attribute this early lack of documented evidence to an observer bias in researchers, who, they argue, tended to interpret sexual behaviour inconsistent with their values as other behaviour.With increasing published evidence of different types of sexual behaviour between animals, arguments for heterosexual monogamy in human society have moved towards characterizing these behaviours as resulting from differences between humans and animals, and in particular on ambiguity in motivation and subjective experience in animals, which is difficult to study. Arguments identifying human and animal behaviour are characterized as anthropomorphism
Anthropomorphism
Anthropomorphism is any attribution of human characteristics to animals, non-living things, phenomena, material states, objects or abstract concepts, such as organizations, governments, spirits or deities. The term was coined in the mid 1700s...
, and in some cases an opposite observer bias is attributed to researchers. Supporters of alternate sexuality embrace the new research as confirmation of the naturalness of alternate sexual behaviour and evidence of its long-term feasibility and utility.
In both cases, any argument that claims that something is good or right because it is natural, or that something is bad or wrong because it is unnatural or artificial is known as the appeal to nature
Appeal to nature
An appeal to nature is a type of argument that depends on an understanding of nature as a source of intelligibility for its claims, and which relies on that understanding for its outcome...
fallacy.
See also
- Against Nature?Against Nature?Against Nature? is an exhibition on homosexuality in animals made by the Natural History Museum, University of Oslo, Norway. The exhibition focuses on occurrence and function of homosexuality in animals, and is the first of its kind....
An exhibition on animal homosexuality taking place in the Natural History Museum at the University of OsloNatural History Museum at the University of OsloThe Natural History Museum at the University of Oslo is Norway's oldest and largest museum of natural history, situated in Oslo.It traces its roots to the University Botanical Garden, which was founded near Tøyen Manor in 1814...
. - Animal behaviourAnimal behaviourAnimal behaviour is the subject of:* The field of Ethology* Animal Behaviour, a scientific journal...
- Biology and sexual orientationBiology and sexual orientationBiology and sexual orientation is the subject of research into the role of biology in the development of human sexual orientation. No simple, single cause for sexual orientation has been conclusively demonstrated, but research suggests that it is by a combination of genetic, hormonal, and...
- Choice and sexual orientation
- Cuckoldry in fish
- EthologyEthologyEthology is the scientific study of animal behavior, and a sub-topic of zoology....
- FreemartinFreemartinA freemartin or free-martin is an infertile female mammal which has masculinized behavior and non-functioning ovaries. Genetically and externally the animal is female, but it is sterilized in the womb by hormones from a male twin, becoming an infertile partial intersex...
(a female bovine with a masculinized brain which acts sexually as a male) - Green PornoGreen PornoGreen Porno is a series of short films on animal sexual behaviour. The series, which began in 2008 and currently airs on The Sundance Channel, is conceived, written, and directed by its star, Isabella Rossellini....
, a series of short films about animal mating, enacted by humans, airing on the Sundance Channel - List of animals displaying homosexual behaviour
- Pair bonding
- r/K selection theoryR/K selection theoryIn ecology, r/K selection theory relates to the selection of combinations of traits in an organism that trade off between quantity or quality of offspring...
- ZoologyZoologyZoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...
- ZoophiliaZoophiliaZoophilia, from the Greek ζῷον and φιλία is the practice of sex between humans and non-human animals , or a preference or fixation on such practice...
External links
- Gay flamingos celebrate fifth anniversary with their children
- Gay penguins resist split attempts
- biologists' view
- National Geographic
- Organization for Animal Dignity – Sexual "Perversions" in Animals: Masturbation, Homosexuality and Zoosexuality in Animals
- San Francisco ZooSan Francisco ZooThe San Francisco Zoo, housing more than 260 animal species, is a zoo located in the southwestern corner of San Francisco, California, between Lake Merced and the Pacific Ocean along the Great Highway...
has run a "sex tour" covering animal sexuality, on Valentine's DayValentine's DaySaint Valentine's Day, commonly shortened to Valentine's Day, is an annual commemoration held on February 14 celebrating love and affection between intimate companions. The day is named after one or more early Christian martyrs named Saint Valentine, and was established by Pope Gelasius I in 496... - A wild, and gay, kingdom World Science
- Is it relevant to look at the animal kingdom to determine if human same-sex behaviour is "natural"?