Bisexuality in the Animal Kingdom

Bisexuality in the Animal Kingdom: What Science Knows — and Why It Debunks the Idea That This Is "Unnatural" Behavior

What bisexual behavior in animals actually means

Sexual behavior vs. sexual orientation

In humans, we distinguish between orientation (who we're attracted to) and behavior (what we actually do). In animals, scientists mostly talk about observed behavior — we can't ask an animal who it "prefers." That's why the scientific literature tends to use the term "same-sex sexual behaviour" rather than "homosexuality" or "bisexuality" in the human sense.

How common is it in nature

According to a large-scale review published in *Nature Ecology & Evolution*, same-sex sexual behavior has been documented in roughly 1,500 animal species — from insects to birds to whales. That's not a marginal curiosity; it's a widespread biological phenomenon.

The bonobo — the planet's most bisexual primate

If any animal deserves the title "ambassador of bisexuality," it's the bonobo (*Pan paniscus*), our close relative from the Congolese rainforest. According to research described in *Scientific American*, around 75% of all bonobo sexual activity is non-reproductive — it serves to ease tension, reconcile after conflict, or simply build social bonds. Sex between females, between males, and between males and females is a routine part of everyday group life.

Sexual contact appears in bonobos as early as their first year of life and functions as a kind of social glue — something like a handshake, just considerably more intimate. Scientists cite it as one of the clearest examples of how sex in nature doesn't only serve reproduction.

Why bisexual behavior makes evolutionary sense

For a long time, the assumption was that behavior which doesn't directly lead to reproduction must be an evolutionary disadvantage — why would nature "waste" energy on something that produces no offspring? More recent research challenges that view.

Social bonds and survival

A large-scale analysis of hundreds of primate species, published in *Nature Ecology & Evolution*, suggests that same-sex sexual behavior helps strengthen social bonds and may be linked to higher survival rates — particularly in species living in large, complex groups with rich social structures.

Reducing aggression within the group

In bonobos, sexual contact has a demonstrable role in conflict management. Instead of resolving disputes by biting, they "settle it" a different way. According to *Scientific American*, bonobos have taken the art of sexual reconciliation to an evolutionary peak among great apes.

An advantage in demanding environments

According to a study published in *Nature Ecology & Evolution*, same-sex behavior tends to appear in species that live long lives, have pronounced group structures, and face predator pressure or resource scarcity — in such conditions, strengthening bonds through sexual behavior may increase the survival chances of the whole group.

More examples of bisexual behavior in the animal kingdom

• Dolphins: In bottlenose dolphins (and related species), young males often form temporary sexual partnerships with each other, which research suggests helps them build lifelong alliances — they go on to mate with females as well.

• Macaques: A study published in *Nature Ecology & Evolution* on rhesus macaques found that male-male sexual behavior is partly heritable but also strongly influenced by social environment — making it a routine part of the species' repertoire rather than a rare deviation.

• Birds and insects: Bisexual and exclusively same-sex behavior has also been observed in numerous bird and insect species, showing the phenomenon isn't limited to big-brained mammals.

Bisexuality in nature — what we can take from it

Science isn't here to dictate who people should love — but it's worth knowing that nature simply doesn't play along with single-box labeling. Bisexual behavior is widespread in animals, well documented, and in many cases clearly beneficial for survival and group cohesion. In other words: variety isn't a bug in the system — it's a feature of it.

And if you'd like a reminder of that variety at home — pencils in hand, no need to prove anything to anyone — coloring books turn out to be a surprisingly good way to engage with the topic with a bit of humor. **FILL ME IN – Gay Coloring Book** by DickObraz takes sexuality with a wink, no pathos and no lecturing — very much in the spirit of what nature itself shows us: that diversity is the normal state of things.

FAQ

Is bisexuality rare in animals?

No. According to a review study in *Nature Ecology & Evolution*, same-sex sexual behavior has been documented in roughly 1,500 species, from insects to whales. In some species, like bonobos, it's a completely routine part of everyday behavior.

Does same-sex sexual behavior in animals mean the same thing as human sexual orientation?

Not quite. Scientists observe behavior in animals, not an internally experienced orientation that could be compared one-to-one with human experience. That's why the scientific literature prefers the term "same-sex sexual behavior."

Why do bonobos behave bisexually so often?

According to research published in *Scientific American*, sexual contact mainly serves them as a tool to reduce tension, reconcile after conflict, and strengthen social bonds — functioning primarily as a social mechanism, not just a reproductive one.

Does bisexual behavior in animals offer an evolutionary advantage?

More recent studies suggest yes — it helps build and maintain social bonds, which can increase the survival chances of both the individual and the group, especially in demanding environments or complex social structures.

Sources used

1. Nature Ecology & Evolution – Drivers of same-sex sexual behaviour (2025): https://www.nature.com/articles/s41559-025-02940-z

2. Nature Ecology & Evolution – Ecological and social pressures drive same-sex sexual behaviour in non-human primates (2025): https://www.nature.com/articles/s41559-025-02945-8

3. Nature Ecology & Evolution – Same-sex sociosexual behaviour is widespread and heritable in male rhesus macaques: https://www.nature.com/articles/s41559-023-02111-y

4. Scientific American – Bisexuality Can Benefit Animals: https://www.scientificamerican.com/article/bisexuality-can-benefit-animals1/

5. Scientific American – Bonobo Sex and Society: https://www.scientificamerican.com/article/bonobo-sex-and-society-2006-06/

6. Smithsonian Magazine – Biologists Reveal How Same-Sex Sexual Behavior May Have Given Some Primates an Evolutionary Advantage: https://www.smithsonianmag.com/smart-news/biologists-reveal-how-same-sex-sexual-behavior-may-have-given-some-primates-an-evolutionary-advantage-180988000/

7. National Geographic – Homosexual Activity Among Animals Stirs Debate: https://www.nationalgeographic.com/science/article/homosexual-animals-debate

Factual accuracy note: All biological claims in this article are drawn directly from the sources listed above. No health or therapeutic claims about humans were made. This is a direct English translation of the original Czech article (`article-1-bisexualita-zvirata`); no facts were added or altered in translation.