When it comes to homosexuality, for many people the recurring idea is that it’s something unnatural. But what does unnatural really mean? The definition of the term is something that goes against natural or human laws, especially in relation to morality.

Homosexuality is something that has always been  exclusively associated with human beings, their psyche and their behaviour. A male is born with a predisposition to mate with a female, since the aim is the reproduction of the species. This is something determined by nature. But is it really like this?

In the animal kingdom there are many examples of homosexuality that completely dismantle the theories that associate these practices with a purely cognitive trait of human beings. In fact, in some species, homosexuality represents an evolutionary advantage.

Scientific studies and references

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. For example, in the case of dolphins, males use sex to bond  with other males and form alliances. In other species, such as fruit flies and insects in general, homosexuality occurs because of their inability to differentiate between sexes.

Giraffe Ithala KZN South Africa by Luca Galuzzi | [CC BY-SA 2.5]
Giraffe Ithala KZN South Africa by Luca Galuzzi | [CC BY-SA 2.5]

Gay geese and evolutionary theory

Geese are monogamous animals. They 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.

These studies explore the idea of homosexual behaviour as an evolutionary response to environmental changes. The environment is what determines these changes, driving species to change their sexual and affective behaviours.

Pair of Canadian Geese (Branta canadensis) on the shore. By Ger Bosma Photos | Shutterstock.com
Pair of Canadian Geese (Branta canadensis) on the shore. By Ger Bosma Photos | Shutterstock.com

Other animals with homosexual behaviour

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.

As for birds, all species that form parental relationships do so, to a greater or lesser extent, with members of the same sex. As many as a quarter of black swans are homosexual. Penguins have even struck up same-sex relationships in zoos in different parts of the world. Studies have shown that up to 85% of lesbian pairs are found in populations of western seagulls. And they’re not the only ones. Pigeons, vultures, ibis, lizards, sheep, macaques, hyenas, flies, dragonflies and countless other animal species are challenging the notion that homosexuality is “unnatural”.

Male Lions. By Laurence Barnes
Male Lions. By Laurence Barnes

The social taboo against science

It is interesting to note how the strong rejection of homosexuality by most societies throughout history has disadvantaged the emergence of a very different reality. A reality in which relationships between individuals of the same sex occur in all species and are part of their evolutionary development.

Thierry Lodé, a biologist specialising in animal sexuality, explains how the scientific community, influenced by the Judeo-Christian heritage, has for a long time viewed homosexual practices in animals as a pathology or disturbance.

In most cases, studies on this subject were avoided for fear of rejection by the scientific community and the wider social context marked by machismo and homophobia. Even today, it remains a taboo subject in many parts of the world where homosexuality is forbidden or even punishable by death.

Two wild adult African Penguins (Spheniscus demersus). By Andrew M. Allport | Shutterstock.com
Two wild adult African Penguins (Spheniscus demersus). By Andrew M. Allport | Shutterstock.com

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I'm a photographer, designer and future zoologist. I write about wildlife and do the artwork for Zoo Portraits and other creative projects.


  1. Many animals also “naturally” eat their young and kill their mates after mating. Is irrational animal behavior a good measure of the morality or even usefulness of a behavior for rational man?

    • This is a debate about homosexuality as something abnormal and as an individual choice, not as something natural that cannot be chosen. It’s not about ethics, it’s about origins.

      • I think the main thing I want to know and many leave out is that a lot of these scenarios are environmental. In short is it the norm or is it behaviour due to circumstances different from the norm. I have in the past seen instances where they stated these behaviours were a result of unfavourable conditions. However I want to see all of this information on both sides. I am only seeing one side and the fact that I can’t find the other info I know exists is a bit concerning.

    • Eleanor, cute and all, but love between two people isn’t “irrational” and even if you feel that it is, you cannot say that love between two consenting adults of the same sex is in the same moral category as cannibalizing your offspring or killing your mates. How absurd. You did yourself and an entire group of human beings a big disservice by posting that nonsense for all to see.

      • Eleanor is obviously living on another planet. I hope her remarks are dismissed , and treated as nonsense , just as you observed, Sandra. 👍

        • I’m sorry but why do hate gays so much??? they’re just tryna live their lives??? why do you care??? oh no the universe doesn’t contend to all my needs let’s go hurt people??? wake up, idiot, you can control some things in life, but this is not one of them. nature put gay people on this earth, so how can gays be against nature???

      • You should check out the statistics on the murder of pregnant women. Of the percentage that die during pregnancy, 20% are murdered by their partner. 30 % of all murdered women are also killed by their partner. There are also hundreds of cases where a parent kills their children. Can you honestly say that animal are different than humans???

        Sadly, you are delusional to think that humans are not animals. That is a scientific FACT.

        10 Mothers Who Killed Their Kids Brutally

        At least one third of all female homicide victims in the U.S. are killed by male intimate partners — husbands and ex-husbands, boyfriends and estranged lovers.



  2. I didn’t get what kind of behaviors was meant. For example a male lion putting his head on same sex’ shoulder, means he is homosexual?
    I am a physician and of course understand the difference of transexual people. But they are not the only people who are homosexual, and I seriously don’t get it. (By the way it doesn’t mean we have the right to victimize or judge anybody any way. It’s just a thought )

    • HomoSEXual, meaning quite literally, “same position of sex”, I’m reminded of, when in the subway, when the japanese rest their head on the shoulder of a stranger after a long day, they just want to rest. In Western culture, resting your head on someone’s shoulder is seen as something much more intimate. I wouldn’t consider the head resting to definitely mean intimate, but it could indicate a close relationship.

    • I mean in the article is cites studies that examined that animals had ” exhibited sexual intercourse, courtship, emotional bonds, partnership and even child-rearing behaviour between homosexual individuals,” so I’d imagine that that’s the general criteria they’re basing this on.

      • They never state the conditions that lead to it. Was the environment normal?? Also the fact that they were willing to class giraffes locking necks as homosexual is very telling. I am also unable to locate information I had gotten in the past talking about how homosexuality in animals sometimes has environmental reasons…I wonder why??

  3. If the males still have sex with females then they are not gay… this is not good evidence of gayness being natural as all of those examples the animals still mate for reproduction.. and only use homosexual acts for either self pleasure or an advantage. They don’t do it for love.

  4. This article shows an outstanding look at the reality of the relationships of animals. Thank you.

  5. I am appalled by your lack of knowledge and find you claim to be a physical hard to belief.

    Homosexual behavior is animals is not simply putting a head on the shoulder of another male. It has been well documented that it included all sexual behavior including penetrations and ejaculation.

  6. Same sex animals are capable of showing affection to each other without being classified as Homosexual. Humans have friends, animals develop friendships bonds too. Why do these friendships have to be categorized as homosexuality?
    Animals being affectionate to their own Family is not an example of homosexuality.
    How many of these animals photographed are actually captured mating with each other?????????❓
    They look like animals at Play to me❗️

    • The pictures are only to be attached to the text. It is about you reading the text and the references that appear in it of scientific studies that expose these theories. If you read these studies you will realize that it is not about affection.

  7. I think you’re article is fantastic, and right on. Someone looking at pictures and missing the article content just sees pictures and misses the point. The article is creating the substance, not the photos. The photos are a bonus, that’s it.

  8. I read an article once, said only dolphins have sex just for pleasure. Do really have homosexual intercourse because they had to have sex like human homosexuals do or just for getting advantages for evolution or increasing their sperm counts to get more chance to impregnate other female animals? Also this article generally bases on male animal homosexuality, how does female animal homosexuality work at all?

  9. If you actually go to the literature, you find that *across the board*, mammals are roughly 5%, give or take, homosexual. That is, homosexual males *prefer* sex with other males, homosexual females *prefer* sex with other females. I think the same percentage holds in birds also, though I’m not so sure. BTW, humans are mammals, Christianity, Islam, etc., notwithstanding. At this point, it’s **boring** and trivial to ask *whether* animals, including us, are, in about 5% (give or take) of cases, homosexual. Boring, yes. It’s been answered, answered, answered. Over and over.
    The *interesting* question is: why is this percentage so constant (yes, give or take, but still…), and what could give rise to it, since most animals are not *explicitly* self-conscious (with some 6 or so exceptions). Since they are not explicitly self-conscious, they do not make “I” statements nor have that kind of self-referring thoughts. Thus, they cannot *choose* in the sense that the 6 or so *explicitly* self-conscious animals (e.g., humans, apes, dolphins, elephants, crows, parrots…) can. And so their homosexuality must be due to external causes, since they don’t choose it (which of course, since we’re animals much like the rest, implies that we mostly don’t either). Ok, *what* external causes make things universal and constant like that (5%, roughly)? Well, duh, we’re stuck with genetics here, aren’t we. And so that leads to the next question, which is, since Darwinian principles (survival of fittest, etc.) hold universally, what about homosexual behavior, drives, etc., makes homosexuals fitter (in some, i.e., 5% or so, of cases) than heterosexuals? And no, I’m not going into this here, there are literally **thousands**, yes, of pages written about this. Go look, people. The web is free, mostly, and just at your fingertips. The 25-word or less answer is that no one’s sure; there are 2 or 3 decent competing theories. *Go look*. The web is right there in front of you.


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