Same-sex sexual behavior has been documented in many animal species, including mammals, birds, and insects. These observations include courtship, genital contact, mounting, pair bonds, and parental care. They show that such behavior occurs in nature, but do not establish that animals have human-like sexual identities or exclusive lifelong orientations.
Researchers generally use the term same-sex sexual behavior (SSB), rather than assuming an animal is “gay” in the human sense. A 2023 review found published reports of SSB in 261 mammal species—about 4% of known mammal species—across 62 families and 12 orders. This is a record of documented research, not an estimate of how common the behavior is. In a 2024 survey, 77% of mammal researchers said they had observed same-sex behavior, 48% had collected data, and 19% had published findings.
11 animals with documented same-sex behavior
The examples include wild and captive observations, and they do not all mean the same thing. Depending on the species and context, researchers have documented social bonding, conflict reduction, stable partner preferences, pair bonds, or parenting.
1. Bonobos
Bonobos (Pan paniscus) regularly engage in same-sex genital contact, particularly among females. These interactions can occur during social tension and reconciliation, as part of a broader social system in which sexual behavior can help maintain relationships and reduce conflict. Bonobos also have opposite-sex sexual relationships, so these observations do not mean they are exclusively attracted to the same sex.
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2. Common bottlenose dolphins
Common bottlenose dolphins (Tursiops truncatus) engage in same-sex sociosexual interactions in male-male and female-female pairs. These interactions have been described in the context of affiliation, cooperation, and social bonding. Sexual contact can serve different functions and does not by itself establish an exclusive orientation.
3. Japanese macaques
Japanese macaques (Macaca fuscata) of both sexes have been documented engaging in same-sex sexual behavior. Female macaques have been observed mounting and stimulating one another even when males are available. Researchers have considered genital stimulation, social bonding, and competition for mates as possible contexts.
4. Rhesus macaques
Same-sex sociosexual behavior is documented in rhesus macaques (Macaca mulatta). A 2023 study of a free-ranging population found that the behavior occurred often enough to analyze statistically and reported evidence of heritable variation in the tendency to engage in it. Heritable variation does not mean there is a single “gay gene” or that behavior is fixed; other factors can also matter.
5. Chimpanzees
Chimpanzees (Pan troglodytes) have been observed touching genitals and mounting same-sex partners across age groups. These interactions can occur during play and periods of social tension. They vary by context and should not be equated with a human sexual identity.
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6. Laysan albatrosses
Female-female pairs of Laysan albatrosses (Phoebastria immutabilis) have been documented in wild colonies. In one Oahu study, 31% of 125 nests were attended by female-female pairs. These pairs sometimes shared incubation and chick-rearing. Their reproductive success was generally lower than that of male-female pairs, but pairing could be better than failing to breed when males were scarce.
7. Greater flamingos
Greater flamingos (Phoenicopterus roseus) have formed same-sex pairs, including female-female pairs, in captivity. A zoo study found these pairs performed several parental-care behaviors comparable to those of male-female pairs. These observations should not be generalized to every flamingo population.
8. African penguins
Same-sex courtship and pair bonding have been documented in captive African penguins (Spheniscus demersus). Zoo observations show that these behaviors occur in the species, but do not provide a population-wide estimate for wild penguins.
9. Domestic sheep
Domestic sheep (Ovis aries) provide one of the clearest examples of a stable same-sex partner preference in a nonhuman animal. Research has identified a minority of rams that show little interest in estrous ewes and prefer other males in partner tests. The often-cited figure of 8%–10% comes from particular studies and is not a universal rate across breeds or populations.
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10. Giraffes
Male-male sexual behavior, including mounting and genital contact, has been reported in giraffes (Giraffa spp.). The popular claim that 93% or 94% of giraffe sex is homosexual is not a reliable general statistic: it is based on limited observations and is often repeated without the original context or denominator. The defensible conclusion is that same-sex sexual behavior has been observed.
11. São Tomé fruit flies
A 2026 study reported that male São Tomé fruit flies (Drosophila santomea) spontaneously courted other males as well as females while retaining the ability to distinguish the sexes. This challenges the claim that male-male courtship in insects is always a failure of sex recognition. The finding concerns courtship behavior, not a human-like identity.
What these examples do—and do not—prove
Same-sex behavior can have different functions in different species. Researchers have documented:
- sexual stimulation and genital contact;
- courtship and copulation attempts;
- social bonding and relationship maintenance;
- conflict reduction and reconciliation;
- long-term pair bonds;
- shared incubation or chick-rearing; and
- stable partner preferences in some individuals.
There is no single explanation that fits every species or interaction. Some mounting may occur during dominance disputes, but it is inaccurate to dismiss every example as “just dominance.” Same-sex behavior has been reported in both captive and free-ranging animals, and in some cases when opposite-sex partners were available.
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It is also inaccurate to say that every animal species is known to display same-sex behavior. A 2023 review discussed reports in more than 1,500 animal species, but many species have not been studied closely enough to confirm or rule it out. The 261-mammal figure counts published records; research priorities and decisions about which behaviors to report affect what appears in the literature.
How this applies to pets
Pet owners may see dogs, cats, birds, or other companion animals mount, court, groom, cuddle, or form close relationships with same-sex individuals. A single behavior does not reveal an animal’s complete preference. Mounting can also be linked to excitement, play, stress, habit, or social interaction.
There is no reason to punish a pet for harmless same-sex social or sexual behavior. Intervene if an interaction becomes aggressive, distressing, or unsafe, just as you would with opposite-sex animals. If a sudden behavior change comes with pain, excessive licking, urinary problems, or irritability, consult a veterinarian rather than assuming it is sexual behavior.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.FAQ
Are animals really gay?
Animals clearly display same-sex sexual behavior, including courtship, genital contact, mounting, pair bonding, and parenting. Scientists generally avoid assuming this proves a human-like sexual identity or exclusive lifelong orientation.
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Is same-sex behavior in animals caused by captivity?
Not always. It has been documented in captive and free-ranging animals, and some studies report it when opposite-sex partners are available. Captivity can affect behavior in some cases, but it is not a universal explanation.
Do same-sex animal pairs raise young?
Yes. Female-female Laysan albatross pairs have shared incubation and chick-rearing, and same-sex greater flamingo pairs in captivity have shown several parental-care behaviors. Not every same-sex pair will raise young.
Should I stop my pet from mounting another animal of the same sex?
Not solely because both animals are the same sex. Stop the interaction if either animal appears frightened, aggressive, injured, or unable to disengage. Mounting can have sexual, social, playful, or stress-related causes; persistent or sudden behavior may warrant veterinary advice.
The Bottom Line
Same-sex sexual behavior is documented in animal life, from bonobo interactions and sheep partner preferences to albatross pair bonds and penguin courtship. The accurate conclusion is not that animals are “gay” in exactly the same way humans are, but that same-sex behavior occurs naturally across many species and animal social and sexual behavior is varied.
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