The data on homosexual behaviour between animals has been pretty scant, but not because it hasn’t been happening. Though animals have been engaging in homosexual acts for millennia, scientists have been suppressing the information due to conservative social attitudes toward same-sex behaviour.
In one particularly dramatic example, researcher George Murray Levick noticed homosexual behaviour among Antarctic Adélie penguins in 1911. Since his findings were considered overly shocking for the time, they were repressed. The few copies available were translated into Greek and distributed among a small group of researchers to limit those who could understand them. Needless to say, gay animals are a bit controversial.
However, the turning point was Bruce Bagemihl’s 1999 book Biological Exuberance, which outlined so many examples, from so many different species, that the topic moved to centre stage. Since then, scientists have studied these behaviours systematically.
But already in 1995, zoologist Konrad Lorenz published a study in which he studied the behaviour of 1,500 animal species. He observed that 450 of these exhibited sexual intercourse, courtship, emotional bonds, partnership and even child-rearing behaviour between homosexual individuals. From primates to intestinal parasites.
A decade later, a study conducted by Dr. Nathan Bailey at the University of California, published in Trends in Ecology & Evolution, confirmed that examples of sexual behaviour between same-sex individuals could be found in all species of the animal kingdom.
These behaviours were different for each species, but in most cases they were an advantageous, evolutionary mechanism.
Is it a rarity?
Despite Bagemihl’s many examples, homosexual behaviour still seems to be a rarity. We have probably missed some examples, as in many species males and females look pretty much alike. But while hundreds of species have been documented doing it on isolated occasions, only a handful have made it a habitual part of their lives.
To many, that isn’t surprising. On the face of it, homosexual behaviour by animals looks like a really bad idea. Darwin’s theory of evolution by natural selection implies that genes have to get themselves passed on to the next generation, or they will die out. Any genes that make an animal more likely to engage in same-sex matings would be less likely to get passed on than genes pushing for heterosexual pairings, so homosexuality ought to quickly die out.
But that evidently isn’t what’s happening. For some animals, homosexual behaviour isn’t an occasional event – which we might put down to simple mistakes – but a regular thing.
For example, geese are monogamous animals who spend their lives with a single mate and only look for another if the first one dies. In Canada, according to some sources, up to 30% of these mates are homosexual.
The biologist Kurt Kotrschal, following on from the studies of Konrad Lorenz, has devoted many years to studying these animals. His research supports the idea that homosexuality is useful for the species. In 1963, Lorenz stated that male mates are more likely to occupy a higher level within geese colonies. This allows them to fertilise solitary females, while continuing with their same sex partners. This is one of the theories that reports the evolutionary advantage of homosexuality, but it is not the only one.
Just a phase?
Take male fruit flies. In their first 30 minutes of life, they will try to copulate with any other fly, male or female. After a while, they learn to recognise the smell of virgin females, and focus on them.
Male flour beetles use a distinctly sneaky trick. They often mount each other, and go so far as depositing sperm. If the male carrying this sperm mates with a female later, the sperm might get transferred – so the male who produced it has fertilised a female without having to court her.
In both cases, the males are using homosexual behaviour as a roundabout way to fertilise more females. So it’s clear how these behaviours could be favoured by evolution. But it’s also clear that fruit flies and flour beetles are a long way from strictly homosexual.
In the case of American bison, polecats or elephants, both males and females have been observed courting and mating with others the same sex. In the case of giraffes, 9 out of 10 couplings occur between males. Bonobos form matriarchal societies, where 60% of sexual relations occur between females. In lions, 8% of mating observed are among males, and in the case of dogs, numerous research studies affirm the existence of patterns of homosexual behaviour.
Should we look closer?
Perhaps we’ve been looking in the wrong place for examples of homosexual animals. Given that human beings are known to be homosexual, maybe we should look at our closest relatives, the apes.
Bonobos are often described as our “over-sexed” relatives. They engage in an enormous amount of sex, so much so that it’s often referred to as a “bonobo handshake“, and that includes homosexual behaviour among both males and females.
Like the macaques, they seem to enjoy it, according to Frans de Waal of Emory University in Atlanta, Georgia, US. Writing in Scientific American in 1995, he described pairs of female bonobos rubbing their genitals together, and “emitting grins and squeals that probably reflect orgasmic experiences“.
But bonobo sex also plays a deeper role: it cements social bonds. Junior bonobos may use sex to bond with more dominant group members, allowing them to climb the social ladder. Males that have had a fight sometimes perform genital-to-genital touching, known as “penis fencing”, as a way of reducing tension. More rarely, they also kiss, perform fellatio and massage each other’s genitals. Even the young comfort each other with hugs and sex.
Bonobos show that “sexual behaviour” can be about more than reproduction, says Zuk, and that includes homosexual behaviour. “There’s a whole range of behaviours that fit in well with how evolution happens that now include homosexual behaviour.” In fact, female bonobos still have sex when they are outside their reproductive period and can’t get pregnant.
Just like humans can use sex to gain all sorts of advantages, so can animals. For instance, among bottlenose dolphins, both females and males display homosexual behaviour. This helps members of the group form strong social bonds. But ultimately, all concerned will go on to have offspring with the opposite sex.
Would they get a Gay Pack?
All these species might be best described as “bisexual”. Like the Japanese macaques and the fruit flies, they switch easily between same-sex and opposite-sex behaviours. They don’t show a consistent sexual orientation. So is a Gay Pack for them?
Only two species have been observed showing a same-sex preference for life, even when partners of the opposite sex are available. One is, of course, humans. The other is domestic sheep.
In flocks of sheep, up to 8% of the males prefer other males even when fertile females are around. In 1994, neuroscientists found that these males had slightly different brains to the rest. A part of their brain called the hypothalamus, which is known to control the release of sex hormones, was smaller in the homosexual males than in the heterosexual males.
That is in line with a much-discussed study by the neuroscientist Simon LeVay. In 1991, he described a similar difference in brain structure between gay and straight men.
So the answer is yes, they would get a Gay Pack if they would have a postal address and we’d sport stuff for animals. But thankfully the other species who has demonstrated having exclusively gay minorities, humans do have a choice to get a pack with designer underwear & grooming products – get yours now!
How does it survive?
This seems quite different from all the other cases of homosexual behaviour, because it is hard to see how it could possibly benefit the males. How could this preference for other males be passed on to offspring, if the males do not reproduce?
The short answer is that it probably doesn’t benefit the homosexual males themselves, but it might benefit their relatives, who may well carry the same genes and could pass them on. For that to happen, the genes that make some males homosexual would have to have another, useful effect in other sheep.
LeVay suggests that the same gene that promotes homosexual behaviour in male sheep could also make females more fertile, or increase their desire to mate. The female siblings of homosexual sheep could even produce more offspring than average. “If these genes are having such a beneficial effect in females, they outweigh the effect in males and then the gene is going to persist,” says LeVay.