The Best American Science and Nature Writing 2011 (41 page)

Zaun, a biologist with the U.S. Fish and Wildlife Service, was studying a Laysan colony on Kauai forty years after Fisher's publication. She realized that certain nests there seemed to wind up with two eggs in them year after year; the distribution of the supernormal clutches wasn't random, as it would presumably be if it were caused exclusively by egg dumping. On a hunch, Zaun pulled feathers from a sample of the breeding pairs associated with two-egg nests and sent them to Lindsay Young, asking her to draw DNA from the feathers and genetically determine the sexes of those birds in her lab. When the results showed that every bird was female, Young figured she'd messed up. So she did it again—and got the same result. Then she genetically sexed every bird at Kaena Point. "Where it wasn't totally clear, or I worried that maybe I mixed up the sample, I actually went back into the field and took new blood samples to do it again," Young told me. In the end she genetically sexed the birds in her lab four times, just to be sure. She found that 39 of the 125 nests at Kaena Point since 2004 belonged to female-female pairs, including more than 20 nests in which she'd never noticed a supernormal clutch. It seemed that certain females were somehow findi ng opportunities to quickly copulate with males but incubating their eggs—and doing everything else an albatross does while at the colony—with other females.

Young gave a talk about these findings at an international meeting of Pacific-seabird researchers. "There was a lot of murmuring in the room," she remembers. "Then, afterward, people were coming up to me and saying: 'We see supernormal clutches all the time. We assumed it was a male and a female.' And I'd say: 'Yeah? Well, you might want to look into that.'" Recently, journals have asked her to confidentially peer-review new papers about other species, describing similar discoveries. "I can't say which species," she explains, "but my guess is, in the next year, we're going to see a lot more examples of this."

It may seem surprising that scientists sometimes don't know the true sexes of the animals they spend their careers studying—that they can be tripped up in some
Tootsie-like
farce for so long. But it's easy to underestimate the pandemonium that they're struggling to interpret in the wild. Often biologists are forced to assign sexes to animals by watching what they do when they mate. When one albatross or boar or cricket rears up and mounts a second, it would seem to be advertising the genders of both. Unless, of course, that's not the situation at all.

"There is still an overall presumption of heterosexuality," the biologist Bruce Bagemihl told me. "Individuals, populations, or species are considered to be entirely heterosexual until proven otherwise." While this may sound like a reasonable starting point, Bagemihl calls it a "heterosexist bias" and has shown it to be a significant roadblock to understanding the diversity of what animals actually do. In 1999 Bagemihl published
Biological Exuberance,
a book that pulled together a colossal amount of previous piecemeal research and showed how biologists' biases had marginalized animal homosexuality for the last 150 years—sometimes innocently enough, sometimes in an eruption of anthropomorphic disgust. Courtship behaviors between two animals of the same sex were persistently described in the literature as "mock" or "pseudo" courtship—or just "practice." Homosexual sex between ostriches was interpreted by one scientist as "a nuisance" that "goes on and on." One man, studying Mazarine Blue butterflies in Morocco in 1987, regretted having to report "the lurid details of declining moral standards and of horrific sexual offenses" which are "all too often packed" into national newspapers. And a bighorn-sheep biologist confessed in his memoir, "I still cringe at the memory of seeing old D-ram mount S-ram repeatedly." To think, he wrote, "of those magnificent beasts as 'queers'—oh, God!" "What Bagemihl's book really did," the Canadian primatologist and evolutionary psychologist Paul Vasey says, "is raise people's awareness around the fact that this occurs in quote-unquote nature—in animals. And that it can be studied in a serious, scholarly way." But studying it seriously means resolving a conundrum. At the heart of evolutionary biology, since Darwin, has been the idea that any genetic traits and behaviors that outfit an animal with an advantage—that help the animal make lots of offspring—will remain in a species, while ones that don't will vanish. In short, evolution gradually optimizes every animal toward a single goal: passing on its genes. The Yale ornithologist Richard Prum told me: "Our field is a lot like economics: we have a core of theory, like free-market theory, where we have the invisible hand of the market creating order—all commodities attain exactly the price they're worth. Homosexuality is a tough case, because it appears to violate that central tenet, that all of sexual behavior is about reproduction. The question is, why would anyone invest in sexual behavior that isn't reproductive?"—much less a behavior that looks to be starkly counterproductive. Moreover, if animals carrying the genes associated with it are less likely to reproduce, how has that behavior managed to stick around?

Given this big umbrella of theory, the very existence of homosexual behavior in animals can feel a little like impenetrable nonsense, something a researcher could spend years banging his or her head against the wall deliberating. The difficulty of that challenge, more than any implicit or explicit homophobia, may be why past biologists skirted the subject.

 

In the last decade, however, Paul Vasey and others have begun developing new hypotheses based on actual, prolonged observation of different animals, deciphering the ways given homosexual behaviors may have evolved and the evolutionary role they might play within the context of individual species. Different ideas are emerging about how these behaviors could fit within that traditional Darwinian framework, including seeing them as conferring reproductive advantages in roundabout ways. Male dung flies, for example, appear to mount other males to tire them out, knocking them out of competition for available females. Researchers speculate that young male bottlenose dolphins mount one another simply to establish trust and form bonds—but those bonds actually turn out to be critical to reproduction, since when males mature, they work in groups to cooperatively gain access to females.

These ideas generally aim to explain only particular behaviors in a particular species. So far, the only real conclusion this relatively small body of literature seems to point to, collectively, is a kind of deflating meta-conclusion: a single explanation of homosexual behavior in animals may not be possible, because thinking of "homosexual behavior in animals" as a single scientific subject might not make much sense. "Biologists want to build these unified theories to explain everything they see," Vasey told me. So do journalists, he added—all people, really. "But none of this lends itself to a linear story. My take on it is that homosexual behavior is not a uniform phenomenon. Having one unifying body of theory that explains why it's happening in all these different species might be a chimera."

The point of heterosexual sex, Vasey said, no matter what kind of animal is doing it, is primarily reproduction. But that shouldn't trick us into thinking that homosexual behavior has some equivalent organizing purpose—that the two are tidy opposites. "All this homosexual behavior isn't tied together by that sort of primary function," Vasey said. Even what the same-sex animals are doing varies tremendously from species to species. But we're quick to conceive of that great range of activities in the way it most handily tracks to our anthropomorphic point of view: put crassly, all those different animals just seem to be doing gay sex stuff with one another. As the biologist Marlene Zuk explains, we are hard-wired to read all animal behavior as "some version of the way people do things" and animals as "blurred, imperfect copies of humans."

When I visited Zuk at her lab at the University of California at Riverside last December, an online video clip of an octopus carrying a coconut shell around the seafloor, and periodically hiding under it, was starting to go viral. For a few days, people everywhere were flipping out about how intelligent and wily this octopus was. Not Zuk, though. "Oh, spare me," she said. To us, Zuk explained, that octopus's behavior reads as proof that "octopuses are at one with humans" because it just happens to look like something we do—how a toddler plays peekaboo under a blanket, say, or a bandit ducks into an alleyway dumpster to avoid the cops. But the octopus doesn't know that. Nor is it doing something so uncommon in the animal world. Zuk explained that caddis-fly larvae collect rocks and loom them together into intricate shelters. "But for some reason we don't think that's cool," she said, "because the caddis-fly larvae don't have big eyes like us."

Something similar may be happening with what we perceive to be homosexual sex in an array of animal species: we may be grouping together a big grab bag of behaviors based on only a superficial similarity. Within the logic of each species, or group of species, many of these behaviors appear to have their own causes and consequences—their own evolutionary meanings, so to speak. The Stanford biologist Joan Roughgarden told me to think of all these animals as "multitasking" with their private parts.

It's also possible that some homosexual behaviors don't provide a conventional evolutionary advantage; but neither do they upend everything we know about biology. For the last fifteen years, for example, Paul Vasey has been studying Japanese macaques, a species of two-and-a-half-foot-tall, pink-faced monkey. He has looked almost exclusively at why female macaques mount one another during the mating season. Vasey now says he is on to the answer: "It isn't functional," he told me; the behavior has no discernible purpose, adaptationally speaking. Instead, it's a byproduct of a behavior that does, and the supposedly streamlining force of evolution just never flushed that byproduct from the gene pool. Female macaques regularly mount males too, Vasey explained, probably to focus their attention and reinforce their bond as mates. The females are physically capable of mounting any gender of macaque. They've just never developed an instinct to limit themselves to one. "Evolution doesn't create perfect adaptations," Vasey said. As Zuk put it, "There's a lot of slop in the system—which," she was sure to add, "is not the same as saying homosexuality is a mistake."

 

About two dozen birds were knocking around when Lindsay Young and I arrived at Kaena Point one afternoon. Young dished about a few of them—"Her mate didn't show up last year"; "God, this one's annoying"—as they waddled by. Laysan albatrosses are not nearly as graceful on land as they are in the air; even they seem surprised by the size of their feet. (Later that week, at a nearby resort, I would recognize their gait while watching an out-of-shape snorkeler toddle back to his beach towel in rented flippers.) "I'm just writing down who's here," Young said, reading the numbers on the birds' leg bands and marking them on her clipboard. After trying and failing to get a clear view of one bird's leg with binoculars, she finally just walked to within a few feet of the animal and leaned over to look.

This is the luxury of studying Laysan albatrosses. Having evolved with no natural predators, the birds have no fight-or-flight instinct—you can basically go right up to one and grab it. In fact, Young did just this a short while later, slinking up to a male on all fours, sweeping it in by its flank, and, in one expert motion, straitjacketing the wings under one arm and clamping the beak shut in her other hand. Then she walked over and handed the thing to me; she needed to take an expensive tracking device off the bird's ankle. "Sorry, but it's like watching a thousand-dollar bill fly around," she said. She took some pliers from her backpack to twist off the anklet and, as I stood bear-hugging the albatross, she added: "They have a nice smell. It's a little musty."

Young and Marlene Zuk are now applying for a ten-year National Science Foundation grant to continue studying the female albatross pairs. One of the first questions they want to answer is how these birds are winding up with fertilized eggs. Typically, albatrosses fend off birds who aren't their mates. So Young has been trying to determine if males who arrive back at the colony before their own partners do are forcing themselves on these females or whether these females are somehow "soliciting" the males for sex. She was staking out Kaena Point on a daily basis, trying to watch these illicit copulations unfold for herself. This was Young's third year; so far, she'd managed to see it happen only twice.

Young and I ambled around for half an hour, maybe more. Then she pointed and, in a monotone, said, "So, that's a female-female pair." We crouched and watched the two birds, numbers 169 and 983. They sat under a spindly, native Hawaiian naio bush. They made
baa
sounds at each other. After a while, Young and I got up.

Another hour passed. (Usually, Young brings along a camping chair.) Occasionally, albatrosses danced in groups of two or three, raising their necks, groaning like vibrating cell phones, clacking their beaks or stomping. But most of the time, they didn't do much at all. "I've spent a lot of my career watching animals not have sex," Zuk later told me.

Homosexual activity is often observed in animal populations with a shortage of one sex—in the wild but more frequently at zoos. Some biologists anthropomorphically call this "the prisoner effect." That's basically the situation at Kaena Point: there are fewer male albatrosses than females (although not every male albatross has a mate). Because it takes two albatrosses to incubate an egg, switching on and off at the nest, a female that can't find a male (or maybe, Young says, who can't find "a good enough male") has no chance of producing a chick and passing on her genes. Quickly mating with an otherwise committed male, then pairing with another single female to incubate the egg, is a way to raise those odds.

Still, pairing off with another female creates its own problems: nearly every female lays an egg in November whether she has managed to get it fertilized or not, and the small, craterlike nests that albatross pairs build in the dirt can accommodate only one egg and one bird. So Young was also trying to figure out how a female-female pair decides which of its two eggs to incubate and which to chuck out of the nest—if the birds are deciding at all and not just knocking one egg out accidentally. From a strict Darwinian perspective, Young told me, "it doesn't pay for one bird to incubate the other's egg unless her partner is going to let her egg be incubated the following year." But presumably, neither female bird knows whether an egg is hers or the other bird's, much less whether it's fertilized or not. A Laysan albatross just knows to sit on whatever's under it. "They'll incubate anything—I have a photo of one incubating a volleyball," Young said.