Do we do it like they do on the discovery channel? Homosexuality in animals

A Tale of Two Penguins

I heard a story a few years ago that really caught my attention. I was told that there were two male penguins in the Central Park Zoo, New York, who were reportedly living as a homosexual couple. I was sceptical as to how much truth was in this claim, so I did some research. It turns out that there was more to this story than I had first allowed myself to believe. The chinstrap penguins, named Roy and Silo, apparently displayed all the behaviours a male-female pair would and appeared to be faithfully devoted to one another. A 2004 New York Times article claimed:


“They exhibit what in penguin parlance is called ”ecstatic behavior”…, they entwine their necks, they vocalize to each other, they have sex… When offered female companionship, they have adamantly refused it. And the females aren’t interested in them, either”


Roy and Silo even attempted to incubate an egg-shaped rock together, taking it in turns to sit on the rock to keep it warm… But alas, being a rock, hatching never occurred. However, keepers at the zoo gave the pair an egg that was abandoned by its mother and without incubation would not have survived. Roy and Silo successfully incubated the egg, which contained a female chick that was later named Tango. They raised Tango until she was old enough to look after herself, just as a male-female pair would have done.

This is an interesting story for many reasons. It is interesting that two male penguins showed such intimate behaviours towards each other. It is interesting that the pair apparently tried to incubate a rock believing it to be an egg. It is interesting that they managed to successfully incubate and hatch an egg that did not contain any of their own genetic material. And most interesting of all was the human reaction to Roy and Silo’s story.

 Roy & Silo


The penguins made headlines all over the world, and inspired a children’s book entitled “And Tango Makes Three” which has won several awards (although not without controversy). Gay rights activists were overjoyed that homosexuality could be viewed as “natural” and that the couple made a good, caring parental unit. Right-wing religious groups reminded people that although a particular behaviour exists in the animal kingdom, it does not mean that we can use this to justify such behaviour as a model for human morality.           

Brace yourselves for the sad part of the story. (Don’t say I didn’t warn you). Shortly after the above-mentioned New York Times article was published, Roy and Silo’s love story appeared to come to an end. According to reports from the zoo, Silo directed his sexual interests towards a female named Scrappy, leaving Roy alone, apparently disinterested in any other mates. Some spectators even described Roy as “heartbroken”. Gay rights activists were, rather absurdly, angry with this turn of events. The religious groups were delighted that Silo had apparently “come to his senses” and that the world could move on.

As touching and eye-opening as this story is, is it just that: A story? We love to remind people in science that tales or anecdotes like this are not data: But is there more to the Roy and Silo story than an odd couple of seemingly gay (or at least bisexual) penguins? I would argue that there is: Roy and Silo are not as unusual as we might think.


How Gay an Animal?

Homosexual behaviour (by which I mean two members of the same sex engaging in sexual behaviour) has been observed in about 1500 animal species; from fish to birds, from small rodents to large mammals, and in primates including our own species. Clearly, homosexual behaviour is far from rare in the animal world.


Homosexual behaviour has been particularly well documented in about 450 species. This includes several bird species such as geese, albatross and flamingos (if there had to be a bird species that engaged in homosexual behaviour, it had to be the flamingo!). Species as diverse as dolphins, bison, giraffes and several species of primates have been found to routinely display homosexual behaviour.



Male giraffes



It’s Not All About the Kids


We now know that homosexual behaviour is common and widespread amongst animals. But why is this? If reason d’être for an individual being on earth is to pass on their genes by having babies, why would natural selection favour a behaviour that encourages an individual to mate with members of their own sex, rather than of the opposite sex? You don’t have to be an evolutionary biologist to work out that being homosexual probably reduces your chance of your ability to have a baby.

There are a few problems with this view. Firstly, in most of the animals in which homosexual behaviour has been observed, they are rarely exclusive: Meaning males may mate with other males, and females with other females, when there is a lack of members of the opposite sex around. Indeed, bonobos – a species of ape that are very closely related to humans – seem to have sexual contact with anything and anyone, regardless of age, sex or even species. It is believed that for the bonobo, sexual contact is just like saying “hello”. Some animals are just simple opportunists.


Female bonobos


Researchers suggest that different species probably have different reasons for displaying homosexual behaviour. For example, it is thought that male dolphin calves engage in homosexual behaviour with each other as a sort of bonding ritual, to form alliances. The young males will mount their same-sex peers, and play with their genitals with their fins. It’s worth noting that female dolphins do this with other females too, but not as frequently as the males. Same-sex behaviour such as this may also serve as practice for when the time comes to mate with a member of the opposite sex for real!

In fact, several theories as to what other functions (homosexual) sex may serve have been suggested. I shall briefly explain just s few of the popular theories below to give you an idea of how diverse they can be:

Dominance expression: I am dominant over you, so I will mount you, and this shall communicate our social status to each other and the rest of the group. This is often used to explain same-sex behaviour in primates.

Controlling population size: homosexual behaviour is reportedly more common when there is a strain on resource availability such as food, in which case it would be beneficial to the group to produce fewer babies.

–    Reconciliation: Have sex and make up. Same-sex interactions can help repair friendships after conflict.

–    Social Bonding: In some species, homosexual activity could just be their version of a handshake or playing rough-and-tumble, as in the above example with young male dolphins.

–    Practice for heterosexual activity: Homosexual behaviours may just be learning opportunities for immature individuals to learn about the birds and the bees (or, as we have seen, the birds, the bees, the mammals, the primates, the fish….) through a form of play.

The main point to draw from this article is that yes, making babies and passing on your genes is a huge part of having sex, for individuals of all species. However, it’s not all about reproduction, it would seem. Sexual behaviour, whether between members of the same sex or opposite sex, must play some role other than baby-making, at least some of the time.


Calling all Researchers!


What is really disappointing about this whole topic is the lack of scientific research on it. But even more disappointing are the reasons behind the lack of research. Paul Vasey, who has studied homosexual behaviour in female Japanese macaque monkeys, notes that

“…researchers are apprehensive about homophobic reactions…Some fear being correctly, or mistakenly, labelled as gay or lesbian. Others


imagine that their careers will be negatively impacted if their names become associated with this sort of subject matter.”


I find this very sad for the future of science. Homosexual behaviours in animals is poorly understood and overly anthropomorphised (meaning that we place humanise the behaviour of other species).

We need to study sexuality in other animals because it is deeply interesting in terms of evolution and animal behaviour, not because we want to try to justify or explain human homosexuality. After all, many animals (for example, ducks!) also engage in necrophilia (having sex with dead bodies), but we don’t discuss that in relation to human behaviour.

The Take-Home Message


Fact: Many animals display homosexual behaviour. This is rarely exclusive, and this suggests that sex probably serves a purpose other than making babies. Future research must focus on this phenomenon in its own right to find out what this purpose could be, and researchers should not have to worry about the backlash they will receive for studying a topic that is, unfortunately, still very much taboo in our culture.






Sommer V. And Vasey P. L. (2006) Homosexual Behaviour in Animals: An evolutionary perspective. Cambridge University Press: Cambridge.

Mooallem, J. 2010. Can animals be gay? New York Times, March 29. (accessed March 24th, 2011)


Image Sources


Roy & Silo: Retrieved 24th March 2011, from

Male Giraffes: Retrieved 24th March 2011, from

Female Bonobos: Retrieved 24th March 2011, from

Deer: Retrieved 24th March 2011, from

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3 thoughts on “Do we do it like they do on the discovery channel? Homosexuality in animals

  1. […] the inspiration for the popular children’s book And Tango Makes Three. However, according to this article, Roy and Silo aren’t the only animals that have displayed homosexual behavior. Homosexual […]

  2. Aviella Yona says:

    Thanks for bringing attention to an oft-ignored topic. I am curious as to what it says about humans (well, more accurately, many Western cultures) that we strive to separate our species from the behaviors of the rest of the animal kingdom by condemning acts such as homosexuality and exclusivity. Anyway, nice article!

  3. Pani Bufetowa says:

    One other theory I came across (can’t remember where/when, so no link – sorry) was that homosexual animals can and do contribute to the raising of young; it makes the most sense in social animals, of course. The same can be said for animals (usually females) who are too old to reproduce (for example matriarch elephants).

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