University of Oslo 2006: Homosexuality in more than 1500 animal species (Museum Exhibit)


“Protector of all liberties / individual liberty activist”
– Complete Skills of a Cockfighter #7, UNOFC

– Gameness til the End


– an exhibition on animal homosexuality

Against nature posterINTRODUCTION

On Thursday October 12 2006 The Natural History Museum, University of Oslo, opened the first-ever museum exhibition dedicated to gay animals.

Today we know that homosexuality is a common and widespread phenomenon in the animal world. Not only short-lived sexual relationships, but even long-lasting partnerships; partnerships that may last a lifetime.

The exhibit displays a small selection of the more than 1500 species where homosexuality has been observed. This fascinating story of the animals’ secret life is told by means of models, photos, texts and specimens. The visitor will be confronted with all sorts of creatures from tiny insects to enormous spermwhales.

How can we know that an animal is homosexual? How can homosexual behaviour be consistent with what we have learned about evolution and darwinism?

Sadly, most museums have no traditions for airing difficult, unspoken, and possibly controversial questions. Homosexuality is certainly such a question. We feel confident that a greater understanding of how extensive and common this behaviour is among animals, will help to de-mystify homosexuality among people. – At least, we hope to reject the all too well known argument that homosexual behaviour is a crime against nature.

The exhibition has received financial supported from the Norwegian Archive, Library and Museum Authority.

The exhibit will run to August 19 2007.

Homosexuality in the Animal kingdom

Pleasure ride: A male killer whale rides the dorsal fin of another male. Sex just for the pleasure of it is common in many animals. Photo: Brian Scott. Original photo obtainable from REF: picture no PIC00166.jpg

Can animals be homosexual?

The sexual urge is strong in all animals. Many species have sex outside the mating season and commonly enjoy sex without reproductive intent – rubbing their sexual organs against each other or stimulating themselves or their partners in other ways. When animals of the same gender have sex, they exhibit homosexual behaviour. We call such animals homosexuals. Some animals are consistently homosexual throughout their life.

gravenderTwo homosexual male shelducks, Tadorna tadorna, mating. While homosexuality probably occurs across the whole Animal Kingdom, the animals dominating the statistics are the larger, more conspicuous species, especially those where the male and female differ greatly, making same-sex mating easy to spot. Foto: Scanpix. Origial photo obtainable from

Which animals are homosexual?

The earliest known mention of animal homosexuality is found in a 2300 year old description of hyenas by Aristotle. Hyena clitoris and labia look like a penis and scrotum, and this made him believe all hyenas are male. Sex between the females is not uncommon, so Aristotle was right in describing them as homosexuals, only they where lesbians rather than gays! Detail of painting by Rafael.

Homosexuality has been observed in most vertebrate groups, and also among insects, spiders, crustaceans, octopi and parasitic worms. The phenomenon has been reported in more than 1500 animal species, and is well documented for 500 of them, but the real extent is probably much higher.

The frequency of homosexuality varies from species to species. In some species, homosexuality has never been reported, while in others the entire species is bisexual. In zoos around 1 in 5 pairs of king penguins are of the same sex. The record is held by orange fronted parakeets, where roughly half of all pairs in captivity are of the same sex.

Why haven’t we been told?

Homosexuality in animals has been known since Antiquity, but has only recently made it into mainstream science. The cause may be a lack of interest, distaste, fear of ridicule, or scientists fearing to lose their grants. The few scientists publishing papers on the topic, often made sure their own sexual preferences were known, directly or indirectly.

Some scientists have interpreted same-sex pairing as anything but sex. In a study of giraffes in Africa a researcher registered all cases where a male sniffed a female as “sexual interest” – while anal intercourse with ejaculation between males was registered as a form of ritualised fighting (“sparring”), despite the fact that 94% of all registered sexual activity in one area took place between males. Only recently has scientists started investigating homosexuality in animals in earnest.

Homosexuality, evolution and humans

Why doesn’t homosexuality become extinct?

Do homosexual animals have offspring? In some animal species it seems homosexuality runs in the family, and sometimes it actually pays off, in evolutionary terms. Among birds, homosexual pairs obtain eggs from “one night stands”, and raise the chicks. Homosexual penguins, swans, geese, ducks and seagulls are known to successfully raise families in this way.

tOccasionally two male flamingos raise families. They obtain eggs by one or both mating with a female. Except for that one occasion, they mate exclusively with each other. Two males can hold a much larger territory than a regular flamingo pair, thus more chicks can grow up. Photo: Eva M. Lauritzen, NHM, Oslo

Most animals – including humans – copulate far more than is necessary for reproduction. Most animals where homosexuality is observed are bisexual. Homosexual mating can pay off or be a drawback, depending on the circumstances, but most of the time it has little evolutionary effect.

Either you’re with us or against us

Many social animals have complex social systems where individuals seek out allies for help and protection. Sex is an important way of strengthening such alliances, also between animals of the same sex. In some animals the whole species is bisexual, and homosexual relationships are prerequisites for joining a pack, making strict heterosexuality a disadvantage.

Many of the species where homosexuality is registered are just such intelligent social animals with complex hierarchies, like wolves, lions, whales and primates.

bavianHamadryas baboons are typical of many animals with homosexual alliances. Large, intelligent and fierce, a male would face stiff competition without his allies, bound to each other through homosexuality. Photo: Yngve Vogt, Apollon, University of Oslo, Norway

Our closest relatives

Humans belong to the apes together with two species of chimpanzees, gorilla, orangutan, siamang and gibbons. Homosexuality is known from all groups, but there are great variations between species regarding gender, age and frequency, and even from group to group within the species. Compared to the other apes, human homosexuality is neither extremely frequent, nor particularly rare, and in our species too, the practice varies from one culture to the next.

Against nature?

The Church Council of Nablus in 1120 AD wrote the first law where homosexuality was labelled a “Crime against Nature”. In the Renaissance, such texts found their way into the laws of many countries, leading to widespread oppression of homosexuals on the basis that it is “unnatural”.

We may have opinions on a lot of things, but one thing is clear: Homosexuality is found throughout the Animal Kingdom. It is not against nature.

More to read about animal homosexuality


Bagemihl, B. 1999. Biological Exuberance: Animal Homosexuality and Natural Diversity. St. Martin’s Press. 752 pp.

de Waal, F. 1997. Bonobo: The Forgotten Ape. University of California Press, Berkeley.

de Waal, F. M. B. & R. Ren (1988): Peacemaking among Primates. Harvard University Press, Cambridge (Massachusetts).

Roughgarden, J. 2004. Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press. Berkeley CA. 474 pp

Sommer, V & P. L Vasey (2006): Homosexual Behaviour in Animals, An Evolutionary Perspective. Cambridge University Press, Cambridge.


Photos used in the exhibitions are bought from agencies/photographers worldwide. Hence, we do not – unfortunately – have the opportunity to offer high resolution copies for the press.

Below you will find a few more examples from the exhibition, with information on where to obtain licence for use.


Two male Right Whales, Eubalaena australis, engaged in “penis fencing” off the coast of Australia. Contrary to heterosexual pairs, male-male pairs of this species may stay together for months.
Original photo obtainable from Marine themes, picture no M07A03 51801.jpg from


Two young male giraffes, Giraffa camelopardalis, mating by the roadside. Scientists have often turned a blind eye to animal homosexuality. In one study area where over 95 % of all sexual activity was between males, the researcher noted it as “sparring”, a form of ritual combat.
Original picture obtainable from Lonely Planet Images, picture no BN4287_15.jpg from


Two female bonobos, Pan paniscus, rubbing their genitals together with some family attendance. The peace-loving bonobos solve most of their conflicts by “making love not war”.
Original photo obtainable from Frans Lanting Photography, picture no 001476-01.tif from

High-resolution images to be freely used in paper
and magazines to cover the exhibition.
To be credited: Per E. Aas, Natural History Museum,
University of Oslo, Norway.

National History Museum, University of Oslo













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