Same-sex sexual behavior has been documented in lions and hundreds of other animal species, but calling any of them “gay” misrepresents what scientists actually observe. Male lions have been photographed and filmed mounting other males, nuzzling, and engaging in courtship-like displays, and these observations are real. The disconnect is between the behavior itself and the human concept of sexual orientation, which involves a stable internal preference that shapes an entire identity. What researchers find across the animal kingdom is far more varied and context-dependent than the label “gay” can capture, and the science behind it has shifted dramatically in just the past decade.
Why Scientists Don’t Call Animals Gay
The term “gay” carries connotations rooted in human society: identity, lifestyle, long-term orientation. When a male lion mounts another male, that act is same-sex sexual behavior, but it tells us very little about whether the lion has a stable preference for males, avoids females, or experiences anything resembling human sexual orientation. Scientists studying this topic have increasingly settled on the neutral term “same-sex sexual behavior” (often abbreviated SSB) precisely because it describes the act without importing assumptions about motivation or permanence.
A glossary published in a major ecology journal put it plainly: “gay” and “lesbian” are anthropomorphic terms best reserved for humans because of their deeply rooted context in human society. Sexual orientation, the stable internal preference for same- or opposite-sex partners, is rarely applied to animals in the scientific literature, with domestic rams being one of the few exceptions.1Trends in Ecology & Evolution. Are There Gay Lions? The Science of Same-Sex Animal Behavior That distinction matters, because collapsing a one-time mounting event in a pride of lions into the same category as a lifelong human sexual identity obscures more than it reveals.
How Common Is Same-Sex Sexual Behavior in Animals
More common than most people assume, and almost certainly more common than what has been formally published. An expert survey of field researchers working with mammals found that over three-quarters of respondents had personally observed same-sex sexual behavior in their study species. But fewer than half had collected data on it, and fewer than one in five had published on it. Of the species identified in that survey as engaging in SSB, roughly four in ten had no existing published reports at all.2PubMed Central. Same-sex sexual behaviour among mammals is widely observed, yet seldomly reported: Evidence from an online expert survey
The gap between observation and publication matters. Researchers have historically treated same-sex behavior as an oddity or footnote rather than a phenomenon worth recording systematically. Anecdotal observations, which make up much of the evidence for rare behaviors in wildlife, have faced a higher bar for publication when the behavior in question is same-sex mounting. The result is a published record that almost certainly underestimates how widespread SSB actually is across mammals.
An early survey of mammals found that captive animals tended to mount same-sex partners more often than wild ones when comparative data were available, and domestic animals mounted more than wild ones as well, with some exceptions.3Mammal Review. Homosexual behaviour and female‐male mounting in mammals—a first survey That finding has sometimes been used to dismiss SSB as a captivity artifact, something that only happens when animals are bored or stressed. But decades of subsequent fieldwork in wild populations have documented SSB across primates, cetaceans, ungulates, and big cats in natural settings. Captivity may increase the frequency, but it doesn’t create the behavior from nothing.
The Social Glue Hypothesis
For years, evolutionary biologists treated same-sex behavior as a paradox. If reproduction depends on mating with the opposite sex, how could a behavior that doesn’t directly produce offspring persist across so many species? The framing assumed that exclusive different-sex behavior was the evolutionary default and that SSB represented a deviation needing explanation. A 2019 paper challenged that framing head-on, arguing that the assumption itself was the problem. If the ancestors of today’s animals mated somewhat indiscriminately, then SSB wouldn’t need a special adaptive explanation; it would simply be part of the behavioral baseline from which more selective mating later evolved.4Nature Ecology & Evolution. An alternative hypothesis for the evolution of same-sex sexual behaviour in animals
Whether or not that “ancestral baseline” model holds up, there is now strong evidence that SSB in mammals tracks closely with social living. A phylogenetic analysis across the mammalian family tree found that the evolution of same-sex sexual behavior was linked to the shift from solitary living to group living. In species that live socially, SSB appears to serve as a tool for building and maintaining bonds, forming alliances, and smoothing over conflicts after aggressive encounters. In males specifically, SSB was also linked to species where adult males kill other adult males (adulticide), suggesting it may help defuse lethal aggression.5Nature Communications. The evolution of same-sex sexual behaviour in mammals
This doesn’t mean every instance of SSB is about alliance-building. It means that, at the species level, the lineages that evolved social living are the same ones where SSB shows up most reliably. The behavior seems to have been favored by natural selection not despite its lack of direct reproductive payoff, but because of the indirect benefits it provides in a social context.
Primates and the Clearest Examples
Bonobos are probably the most famous case. Female bonobos engage in genital-genital rubbing with other females more frequently than they have sex with males, particularly in feeding contexts where competition over food might otherwise trigger conflict.6Hormones and Behavior. The cooperative sex: Sexual interactions among female bonobos are linked to increases in oxytocin, proximity and coalitions These interactions are associated with spikes in oxytocin and with increased proximity and coalition support between the females involved. In other words, the sex appears to do something concrete for the relationship between those two individuals.
Research on bonobo cortisol levels adds another layer. Genital contacts increased when access to food was restricted, and there was a measurable relationship between these contacts and stress hormone levels, supporting the idea that SSB in bonobos functions as a tension-regulation mechanism.7PubMed. The relationship between socio-sexual behavior and salivary cortisol in bonobos: tests of the tension regulation hypothesis Bonobos don’t just mount each other randomly; the behavior spikes in situations where social tension is high and appears to bring cortisol back down.
A large-scale primate analysis spanning nearly 500 species reinforced the social complexity connection. Species living in drier environments with more food scarcity and predation pressure, and species with more complex social hierarchies, were more likely to show SSB. Environmental and life-history factors influenced SSB mostly indirectly, while social complexity directly promoted it.8Nature Ecology & Evolution. Ecological and social pressures drive same-sex sexual behaviour in non-human primates The takeaway is that the more socially demanding an environment is, the more likely a primate species is to have SSB in its behavioral repertoire.
When Same-Sex Mounting Is About Rank
Not all same-sex mounting serves the same purpose, even within a single species. In golden snub-nosed monkeys, researchers found that higher-ranking males were more likely to be the mounter than the lower-ranking one, consistent with mounting being a dominance display. But this pattern broke down among juveniles, where mounting happened in playful, peaceful contexts that had nothing to do with hierarchy.9PubMed. Do same-sex mounts function as dominance assertion in male golden snub-nosed monkeys (Rhinopithecus roxellana)? The same behavior, performed by different age groups in different social contexts, appeared to serve entirely different functions.
Barbary macaques showed a similar pattern. Higher-ranking males within a mounting pair were more likely to be the mounter and to mock bite the lower-ranking male during the interaction, both signals consistent with dominance assertion.10PubMed. The functions of non-reproductive mounts among male Barbary macaques (Macaca sylvanus) This is one reason researchers resist labeling all same-sex mounting as “sexual” in the first place. In some cases, the behavior looks more like a power move than anything related to attraction or pair-bonding.
The picture that emerges is that SSB in animals is often multifunctional. It can be affiliative, dominance-related, stress-reducing, or practice for reproductive behavior, sometimes within the same species and sometimes even in the same individual depending on who the partner is and what’s happening socially. Trying to slot all of it into a single explanation is like trying to explain every human handshake with one theory.
Sex Ratios and Opportunity
Sometimes same-sex pairing is a direct response to who’s available. In feral pigeons, experimentally removing males from colonies led to stable female-female pairs that could successfully raise offspring at rates comparable to male-female pairs. When females were removed instead, males formed temporary same-sex pairs marked by mutual aggression, a much less stable arrangement.11Scientific Reports. Experimentally evoked same-sex sexual behaviour in pigeons: better to be in a female-female pair than alone The pigeon experiment was one of the first controlled demonstrations that skewing a population’s sex ratio can shift its entire social structure and cause cooperative same-sex breeding to emerge in a species that is otherwise monogamous.
Japanese macaques tell a more complicated story. When researchers experimentally created a female-biased sex ratio, females did solicit more same-sex partners and form more same-sex consortships. But the researchers noted that the females didn’t appear to be turning to other females simply because males were unavailable. Instead, they suggested that an abundance of preferred same-sex partners or a scarcity of opposite-sex competitors best explained the increase.12PubMed. Skewed sex ratios and female homosexual activity in Japanese macaques: An experimental analysis In other words, at least for these macaques, the “making do” explanation doesn’t fully hold. Some females appeared genuinely motivated to seek out same-sex interactions when the opportunity was there, not just when opposite-sex alternatives were absent.
The Rare Case of Exclusive Preference
Domestic rams stand out in the scientific literature because a consistent minority, roughly one in twelve in studied flocks, show a lasting preference for mounting other males even when receptive females are available. This isn’t situational or hierarchical; it persists across contexts and over time. Researchers have found that these male-oriented rams have a smaller nucleus in a region of the hypothalamus compared to female-oriented rams, paralleling findings about brain structure differences in other mammals.13Endocrinology. Brain Aromatase: Dyed-in-the-Wool Homosexuality
Rams are one of the only non-human animals for which “sexual orientation” is used in the scientific literature with some confidence, precisely because their preference is stable, enduring, and independent of whether opposite-sex partners are around. This makes them genuinely unusual. In most other species, same-sex behavior is flexible, context-dependent, and mixed with opposite-sex behavior. The rams are the exception that highlights the rule: for the vast majority of animals, SSB doesn’t map onto the human concept of a fixed orientation.
Same-Sex Pairing in Birds
Laysan albatrosses on Oahu, Hawaii, attracted widespread media attention when researchers documented long-term female-female pairs nesting together. These pairs fledged fewer chicks than male-female pairs, but they still successfully raised offspring, making the arrangement a better reproductive strategy than not breeding at all.14PubMed Central. Successful same-sex pairing in Laysan albatross In pairs that raised chicks across multiple years, at least one offspring was genetically related to each female, meaning both partners had mated with males at some point and both benefited reproductively from the arrangement.
The albatross case illustrates how same-sex pairing can persist for practical, demographic reasons. In the Oahu colony, females outnumber males. Albatrosses are obligate biparental caregivers: a single bird can’t incubate an egg and feed itself at the same time. Pairing with another female, even at reduced efficiency, beats the alternative of skipping breeding entirely. Follow-up research found that females in same-sex pairs that successfully raised a chick sometimes acquired a male mate the following year, while females whose same-sex pairings failed never did, suggesting that males may assess female quality and that same-sex pairing functions as a fallback for females who would otherwise be excluded from reproduction.
Dolphins and Male Alliances
Bottlenose dolphins in Shark Bay, Australia, form some of the most complex male alliance networks known outside of humans. Males cooperate in nested layers: pairs or trios work together to consort females, teams of up to fourteen males cooperate in contests with rival groups, and even larger third-order alliances associate at lower levels.15PubMed Central. Male alliance behaviour and mating access varies with habitat in a dolphin social network Within these alliances, males engage in extensive physical contact, including petting, rubbing, and genital contact with same-sex partners. These behaviors appear to cement bonds that are critical for reproductive success, since no male can monopolize access to females without cooperative allies.
Dolphin SSB is interesting because it collapses the distinction between “sexual” and “social” behavior. The physical contact between allied males looks indistinguishable from courtship in some respects, yet its function within the alliance framework is clearly social. Whether you call it sexual behavior or social bonding depends on where you draw lines that dolphins themselves clearly don’t recognize.
What Fruit Flies Reveal About the Genetics
Some of the most precise genetic work on same-sex behavior has been done in fruit flies, where researchers can manipulate individual genes and observe the results within days. The fruitless gene was initially described as both necessary and sufficient for establishing male-typical sexual behavior in Drosophila. Males with certain mutations in fruitless court other males enthusiastically.16PubMed Central. Systems behavior: of male courtship, the nervous system and beyond in Drosophila But more recent work has complicated that picture. Another gene, doublesex, also contributes to sex-specific neural circuitry, and the earlier claim that fruitless alone could account for all sexually dimorphic behavior has been refuted.17Current Opinion in Neurobiology. Fruitless, doublesex and the genetics of social behavior in Drosophila melanogaster
The fruit fly work is a useful reminder that even in an organism with a two-week generation time and a tiny brain, the genetics of sexual behavior aren’t simple. There is no single “gay gene” in flies, let alone in mammals with brains orders of magnitude more complex. What the fly research does show is that sexual behavior is wired into neural circuits shaped by multiple genes interacting with each other during development, and that tweaking those circuits can redirect behavioral preferences.
Play, Practice, and Development
Young animals frequently mount same-sex peers during play. In wild chimpanzees, individuals that spent more time in social play reached developmental milestones earlier, including first observed mating attempts, first grooming of unrelated individuals, and spatial independence from their mothers.18PubMed Central. The relationship between social play and developmental milestones in wild chimpanzees (Pan troglodytes schweinfurthii) Mounting behavior among juveniles, regardless of the sex of the partner, appears to be part of a broader developmental program through which young primates learn the motor patterns and social cues they’ll need as adults.
This developmental angle sometimes gets weaponized in public discourse: “it’s just practice, not real.” But framing play-mounting and adult SSB as mutually exclusive categories doesn’t hold up. Adult bonobos, macaques, and dolphins engage in same-sex behavior in contexts that have nothing to do with motor practice. Juvenile play-mounting and adult SSB can coexist in the same species without one invalidating the other. The developmental function of play-mounting in youngsters doesn’t tell us that all SSB across all ages is “just” practice any more than the fact that children play-fight tells us that adult boxing is only a developmental exercise.
What Lions Actually Do
Returning to the animals in the title: male lions have been observed mounting other males, head-rubbing, rolling together, and engaging in what field observers describe as courtship sequences. These behaviors occur in wild populations, not just zoos. Male lions that form coalitions, typically brothers or unrelated males who team up to take over and defend a pride, engage in extensive affiliative physical contact. Given the mammal-wide finding that SSB tracks with sociality and with species where males kill other males, lions fit the pattern neatly. Coalition partners who bond more tightly are better at defending territories and prides, and sexual behavior between males may be one mechanism through which that bond is maintained.
But no researcher has described any individual lion as having a stable same-sex orientation. The males observed mounting other males also mate with females. The behavior is part of a social toolkit, not evidence of an exclusive preference. When media outlets run headlines about “gay lions,” they’re applying a human identity category to a behavior that, in context, is better understood as one expression of a highly social predator’s bonding repertoire.
Why the Framing Matters
There’s a tension between two audiences for this research. Some people want animal SSB to validate human homosexuality: “it’s natural, look, lions do it too.” Others want to dismiss it as irrelevant to humans: “animals do all kinds of things we wouldn’t call moral.” Both framings miss what the science actually shows. Animal SSB is real, widespread, and in many cases adaptive, but it is not the same phenomenon as human sexual orientation. Human identity, human culture, and the human capacity for self-reflection make our experience of sexuality qualitatively different from what a bonobo or a ram experiences, even if some of the underlying neurobiology overlaps.
The more interesting lesson from animal SSB research may be how strongly it pushes back on the idea that there is a single “natural” sexual behavior for any species. Across hundreds of species, sexual behavior turns out to be flexible, context-dependent, and shaped by social demands at least as much as by reproductive imperatives. The question “are there gay lions?” turns out to be less about lions and more about whether our categories are adequate for describing what animals actually do. So far, the evidence says they aren’t.