Rainbow world

Nature is queer in tooth and claw.

Written by       Illustrated by Giselle Clarkson

Giselle Clarkson

Until recently, despite humans’ intense interest in them, humpback whales have maintained a remarkable degree of privacy around their sex lives. But in January 2022, two humpbacks went for it while circling around a boat off the coast of Maui, in Hawaii. Afterwards, looking at photographs of the event, scientists realised both whales were male.

“The sea itself seems to be a queer place,” writes the Guardian’s Philip Hoare, “where gender is at best a slippery notion.” Many kinds of fish, including clownfish and snapper, change from male to female, or vice versa, partway through their lives. So do slipper limpets. Marine Persian carpet flatworms are hermaphrodites—meaning they have both male and female parts—and they mate by fencing with their penises, each trying to stab and inseminate the other while avoiding becoming pregnant themselves.

And it’s not just the ocean that’s way gayer than we thought. So far, researchers have identified same-sex behaviour—from performing courting songs to mounting each other to all kinds of X-rated gymnastics—in more than 1500 species, including primates, sea stars, snakes, toads, crickets, red-billed gulls (see feature, page 32) and even nematode worms. And just as creatures reproduce in a wide variety of ways, animal sexuality encompasses a full rainbow of different arrangements.

Pūkeko, for instance, are pansexual—in the North Island, at least. There, pūkeko live in big, noisy communes where “everybody’s kind of mating with everyone”, says Kristal Cain, a bird researcher at the University of Auckland. “Females are mounting females, males are mounting males, and females are mounting or mating with all of the males in the group, not just the dominant ones.” (In the South Island, by contrast, there are fewer birds and they tend to link up in male-female pairs.)

In a few species, some individual animals display a clear preference for either homosexuality or heterosexuality. Around eight per cent of male bighorn sheep mate only with other males—they have no interest at all in getting together with ewes. Nearly a third of lifelong Laysan albatross pairs on Oahu in Hawaii are female same-sex couples. They mate with males (while those males’ partners’ backs are turned) but nest, court, and raise chicks together. A quarter of black swan pairs are male-male—and their chicks are more likely to successfully fledge compared with heterosexual black swan couples. And in groups of bonobos and Japanese macaques, females often hook up with each other.

It’s only recently that scientists have dared to even mention the same-sex behaviour they’ve observed among the animals they study. Even now, it’s widely assumed to be something of a paradox, at odds with Darwinian theory and in need of explanation. In a world where the point of existence is procreation, isn’t queerness an evolutionary dead end?

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“People ask me, are dolphins monogamous? And I say, ‘Well, yeah—with other males.’”

Since 1988 Janet Mann, a biology and psychology professor at Georgetown University in Washington, DC, has been observing bottlenose dolphins in Western Australia’s Shark Bay. Her team has tracked close to 2000 individuals from birth to death. From the start, it was clear that male-male bonds form early in life. That very first year, she found that a pair of just-weaned males called Cookie and Smokey were always together. “They would just take off from their mums and play or pet or mount each other,” she says. “Cut to 36 years later and they’re still together.”

There have been ups and downs along the way. When Cookie and Smokey were about seven they fell out for a couple of years, after Smokey got attacked by a tiger shark—Mann speculates that perhaps Cookie wasn’t supportive enough in his hour of need. But eventually they made up, and are now a tightly bonded alliance—two males that swim together, woo females together, form temporary meta-alliances with other male alliances, and have sex together.

A lot of sex.

In 2006, Mann tried to quantify the homosexual behaviour she was observing. Her study showed that male calves engage in “sex play”, mainly with each other, an average of 2.4 times per hour. That’s “nearly 40 times that for wild female bonobos”, she wrote, “a species already characterised as hypersexual”.

Bottlenose male calves have more same-sex interactions than opposite-sex interactions. (A recent paper found this is also true for male rhesus macaques.) All this horny enthusiasm lasts mainly while the dolphins are young and solidifying their bonds; the frequency of sex falls off between older male pairs or trios.

As adults, these stable, intimate alliances actually seem to help male bottlenose dolphins to pass on more of their genes. By working together, Cookie and Smokey are able to keep rivals away from a female in oestrus and ensure only they can mate with her.

Of course, they’re also competing against each other to father any offspring. If you thought your love life was complicated, “Shark Bay dolphin males are cooperating and competing at multiple levels in a fluid, three-dimensional environment”, Mann writes.

Why might same-sex sex be so important for these dolphins? Partly, that awkward, slippery environment. “Sex in the water is difficult,” says Mann, and requires “exquisite timing”—so perhaps dolphins need lots of practice? But she also thinks it might be something to do with trust.

For social animals, sex is one way of developing and strengthening relationships—not only helping male dolphins to breed, but also survive, as they shelter each other from stress, predators, or harassment from other dolphins. Over the years, Mann’s studies have demonstrated a “widowhood effect”: if one member of an alliance dies, the other is much less likely to survive.

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So dolphins are pretty queer. And those 1500 other species where homosexual behaviour has been reported? That’s almost certainly an underestimate, says evolutionary biologist Ambika Kamath.

“There’s a long history of biologists pretending that same-sex sexual behaviour is pretty much anything other than sex.”

One scientist apparently described gay sex between ostriches as “a nuisance” that “goes on and on”. In the 1970s, a bighorn-sheep researcher wrote: “I still cringe at the memory of seeing old D-ram mount S-ram repeatedly … to conceive of those magnificent beasts as ‘queers’—oh, God!” And in the same decade, the scientist who reported that female Japanese macaques were pairing up and having sex was accused of doctoring photographs and making up data.

Half a century earlier, the stigma had been even more severe.

George Murray Levick was a doctor on Robert Falcon Scott’s tragic 1910-1913 Antarctic expedition. Stuck at Cape Adare throughout the polar summer, Levick made a careful study of the vast Adélie penguin rookery there. But the sexual behaviour he saw shocked him, so much so that he later pasted over those sections of his field notes—as though he was applying a fig leaf to his notebook, or creating a Cosmopolitan-style sealed section.

Fortunately, the coded words Levick scrawled over the top were “hardly James Bond-level” subterfuge, says Lloyd Spencer Davis from the University of Otago, author of a book about Levick and his penguins. “He used schoolboy code—he just transposed Greek letters for Roman letters.” When Levick’s notes turned up nearly 100 years after he’d written them, Davis was easily able to decode them.

The salacious penguin activities Levick had observed included sexual coercion, males having sex with dead females, and, yes, reciprocal mounting among males. “It just wasn’t the done thing for a gentleman in that era to be talking about such things,” says Davis.

But it was nothing Davis hadn’t seen during his own years of studying Adélies in Antarctica. Because it’s light 24 hours a day during the summer, his team could surveil the penguins around the clock: real-life reality TV.

He watched these famously monogamous birds cheat on each other—“it only takes a minute: these are not heroic love makers”and steal nest stones (which are a form of penguin currency, as they stop icy meltwater touching the eggs). He even saw females allow a low-status male to mate with them in exchange for nest stones. The one thing he never observed—even with the 24-hour spotlight of the midnight sun—was female same-sex behaviour. Male Adélie penguins are not necessarily gay, he says—they rarely raise chicks together, as some captive penguins famously have, and he hasn’t followed individuals to see if they choose to mate only with other males. What’s certain, he says, is that they are extremely indiscriminate when it comes to sex.

In the 1990s, to investigate sperm competition, Davis and a colleague had a dead penguin taxidermied into a female’s “receptive position”, and used that to collect males’ sperm. The males were so obliviously enthusiastic that the next year the scientists just grabbed a fluffy penguin soft toy from the gift shop at the International Antarctic Centre in Christchurch on their way south. “It had no resemblance to a real penguin at all. But we laid it on the ground, and honestly, the males were just lining up.”

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The past few decades have seen a “positive feedback loop” between science and society, says Cain. As the stigma around homosexuality has faded, it’s become more acceptable to publish accounts of animal same-sex behaviour. At the same time, queer scientists have brought new perspectives to biology and started asking different questions. By now, the sheer gay exuberance of the animal world is undeniable.

“It undermines a lot of the political rhetoric around, ‘It’s not natural,’” says Cain. Still, she and other scientists caution against making any assumptions about humans based on what dolphins or macaques or albatrosses or penguins might get up to between the ice sheets.

“What animals do—what’s perceived to be ‘natural’—seems to carry a strange moral potency… as either a validation or a denunciation of our own behaviour, depending on how you happen to feel about homosexuality and about nature,” Jon Mooallem wrote in the New York Times in 2010.

But really, “we shouldn’t use animals as a model for what we should do and not do”, says Cain. “Animals do all kinds of stuff.” In other words, as the American biologist Marlene Zuk writes, “People need to be able to make decisions about their lives without worrying about keeping up with the bonobos.”

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Gay animals may not necessarily say anything about us, but what do they tell us about evolution?

Since Darwin, it’s been taken for granted that the animals that raise the most babies are the most evolutionarily successful: they pass on more of their genes, and then those genes become more common in the population, shaping how that species looks and behaves. In this context, says Ambika Kamath, it seems like “same-sex sexual behaviour shouldn’t evolve”—it must be costly to an individual’s chances of passing on its genes, and therefore must always offer other advantages that outweigh the costs.

But there are a lot of assumptions built into this idea, says Kamath. Firstly, that animals can’t be bisexual—as so many of them in fact seem to be. And secondly, that sex between different sexes always leads to babies. “It’s only against the bar of perfectly efficient heterosexual sex that same-sex sexual behaviour is somehow lacking or paradoxical. But is that actually true in nature?”

Field studies suggest it is not—or at least, not always. The Canadian anthropologist Paul Vasey has studied the really rather lesbian Japanese macaques for decades, carefully testing possible evolutionary explanations for the females’ frequent same-sex couplings. Were they expressing dominance over each other? Were they making up after fighting? Or were they trying to attract the interest of neighbouring males?

None of these theories stood up, and Vasey concluded that there was no grand big-picture evolutionary benefit: the snow monkeys were simply doing it for pleasure. And it turns out same-sex sex might not be costly to procreation, either. A separate study of rhesus macaques—a related species—found males that frequently mounted other males had just as many offspring as those who focused their sexual attention on females.

In some cases, then, perhaps queerness is basically neutral as far as evolution is concerned—it’s not getting selected for or selected against. “If it’s not costly, then we don’t really need to be that worried about explaining its evolution,” says Kamath. “It simply exists.”

And perhaps it always has. Another traditional idea is that early animals must have all been heterosexual, with same-sex behaviour evolving later. But Kamath and a group of researchers recently published a provocative paper arguing that “the ancestral state is one in which everybody’s having sex with everybody”. Just like the pūkeko.

So, what led some species to become predominantly heterosexual while others engage in much more same-sex behaviour? “Both of those questions become equally interesting,” says Kamath.

We can only answer them, however, once we know much more about how prevalent gayness is among different species—something that will require many more hours in the field, and no doubt yield more surprises.

“Animals really don’t fit in these really narrow boxes that we try to put them in,” says Cain. “Humans don’t either! There’s a lot of variability, and what we call sex is super multi-dimensional. Trying to make everything really simple never works in biology.”

Human sexuality is a wild and wonderful rainbow. The animal world? It’s even wilder.

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