Zoobiquity

  Visual stimulation has an interesting effect on females, too. Male courtship displays are the iconic stock images of nature documentaries, from mighty rams butting heads to gentle bowerbirds presenting their paramours with nests intricately inlaid with flowers, shells, stones, and berries. The reason for all this visual excitement is to entice a female into copulation—by communicating not just sexual readiness but superior genetic fitness. However, these displays might also have an invisible effect that extends beyond the act of copulation and actually improves survival of any offspring.

  Researchers in Morocco were desperately trying to improve the reproduction rates of an endangered bird called the houbara bustard. These natives of northern Africa have been hunted into near oblivion for their supposedly aphrodisiac meat. After the artificial breeding program had produced disappointing hatch rates, investigators realized that some of the females they were inseminating by hand had never actually seen a mature male bustard. So they decided to try an experiment. Instead of simply placing a sample of sperm into the females, they first gave them a look at a sexy male bustard—one who was strutting around in the characteristic houbara pre-mating ritual, with his white head and neck feathers puffed out like a rock star wearing a boa. Females who had been primed with this sight—no matter whose sperm they were eventually fertilized with—were more likely to lay viable eggs. Their chicks were more likely to hatch and were stronger when they did. The reason: primed with the sexy sight, the females added more testosterone to their eggs. This made them grow faster and stronger. It spurred the chicks to create more testosterone on their own, giving them a hormonal head start in life. Of course, this was not a conscious choice the mother birds made; rather, it was a physiological response to a visual cue. Similarly, pig breeders have found that sows who were “courted” by boars before artificial insemination—or even just exposed to boar odor—had higher conception rates.

  In the animal world, females are not just passive vessels receiving sperm but active participants who can influence the outcome of their breedings through sperm selection and egg enhancement. This is a new area of study that could have important implications for improving animal breeding programs around the world. And it could also help women struggling with infertility. Assisted reproduction has come a long way in the past decade, but although the male specimen-collection rooms of fertility clinics are well stocked with racy magazines, women are not regularly advised to be “visually motivated” during monthly egg development. Maybe surfing YouTube for clips of a drenched and brooding Colin Firth, riding crop in hand, would have an enhancing effect on egg recruitment and growth, whether a woman is going through in vitro fertilization (IVF) or trying naturally for conception.

  Yet another brain-based erection enhancer enters male brains through the ears. Canoodling horses nicker and whinny; in-the-mood boars “chant.” The biologist Bruce Bagemihl notes that “female Kob antelope whistle, male Gorillas pant, female Roufous Rat Kangaroos growl, male Blackbuck antelopes bark, female Koalas bellow, male Ocellated Antbirds carol, female Squirrel Monkeys purr and male Lions moan and hum.” Any one of those sounds, produced for a willing recipient, could trigger a neural cascade that would result in or enhance an erection. One fascinating study revealed that female Barbary macaques timed their “loud and distinctive” copulatory utterances to coincide with—or perhaps influence the likelihood of—their mate’s ejaculation. Bulls have been found to get erections when played a recording of the sounds of a cow in estrus.

  But the brain’s ability to translate sensory inputs into an erection has a deflating flip side. Sometimes, instead of encouraging an erection, the brain squelches it.

  A mating animal is vulnerable. It’s necessarily distracted from its environment. It’s momentarily disconnected from other important survival activities, like food gathering and territory defense. A psychogenic component to erection means that if a male’s brain detects danger, threat, competition, or diminishing returns, it can terminate the erection.

  But this physiology sets the stage for the number one reason human males visit doctors with sexual complaints: erectile dysfunction, or ED.f That’s when erections consistently don’t achieve the hardness required for penetration or last as long as they once did. Although not life-threatening, as medical problems go, ED can profoundly affect quality of life and the social well-being of men and their partners. Worldwide, one in ten men suffers from ED, thirty million of them in the United States alone. Preoccupation with penile stiffness sustains a multibillion-dollar industry that peddles drugs, devices, dietary aids … and not a small amount of snake oil.

  According to Arthur L. Burnett, an expert in neurourology at Johns Hopkins University, our understanding of erectile dysfunction has done “an about-face” in the past four decades. Doctors used to think ED developed out of inevitable yet vague factors like aging and hormonal imbalances—or that it was entirely psychological. In the heyday of psychoanalysis, a man’s inability to achieve a firm erection was presumed to be a consequence of his unresolved internal conflicts.

  Today, Burnett told me, ED is seen as a “truly physical problem.” Because human erections are utterly dependent on blood flow, conditions like diabetes, hypertension, clogged arteries, vein disorders, and weak pulses—anything that impedes the proper surging of blood around the body—can induce or exacerbate ED. So can having one’s nerves severed during prostate surgery.

  Men are no longer told that ED is all in their heads or that they’ve got an emotional problem. On the other hand, although most ED is physical in origin, psychogenic ED—when a man feels willing but his medically capable penis won’t cooperate—does indeed exist. And it can trigger confusion and distress for patients and couples.

  As we’ve seen, animal penises also stiffen and soften in response to environmental and other triggers. It may be that what we call psychogenic ED in humans has roots in protective physiology that is shared by aroused males of many species.

  Ring-tailed lemurs, the wide-eyed primates immortalized by the voice of comedian Sacha Baron Cohen in the animated film Madagascar, typically mate just once a year. During that discrete window every autumn, the females are fertile for a single, fleeting eight- to twenty-four-hour stretch, and the males’ testosterone levels rise. This “wild Halloween party,” in the words of Andrea Katz, curator of the Duke Lemur Center, creates a high-stakes frenzy of competition among the males and provocative teasing from the females. As Lisa Gould, an anthropologist at the University of Victoria and an expert on ring-tailed lemur behavior, told me, male-male competition is so frenetic during breeding season that she has seen males jump on other mating males and push them off females. Sometimes males become seriously injured during male-male combat over the chance to mount a female. One encounter she witnessed was especially interesting. A lower-ranked male was desperately trying to complete a copulation amid the fray of mating animals.

  “He was incredibly nervous and kept looking around. He kept jumping on and off and looking around behind him. I don’t think he ever completed his mating,” she said. Gould explained that, in lemurs at least, these so-called failed copulations are probably the result of social stress and competition. The neurological input of vigilance or fear could affect copulation success. Gould also pointed out that each male is different. The lemur she observed nervously looking around while he tried to copulate was clearly very concerned about his surroundings and social challengers. Another male might thrive on that kind of competition. No two animals are exactly alike, and individual animals will show ranges of tolerance to various types of stressors.

  What biologists call failed copulations physicians might call a lost erection or erectile dysfunction. And physiologically, they’re similar. Fear and anxiety interfere with an erection’s critical first step: relaxation. Remember, to build an erection the penis must first relax. If the brain senses danger, the surge of adrenaline and other hormones will terminate the relaxation sequence and squelch the nascent erection.g Any anima
l capable of having an erection can, and will, sometimes lose it.

  And that’s a good thing, because coitus interruptus can be a lifesaver. Imagine the fate of an animal who continued to mate despite looming danger. Sometimes the greatest threats come not from outside predators but from school-, flock-, and herdmates. And in male animals, we see that social intimidation can inhibit erections. The mere presence of a dominant ram shuts down sexual activity in subordinate male sheep, for example. Among deer and other ungulates living in hierarchical groups, often only the top-ranking males can mate. The control of mating by dominant males has been seen in birds, reptiles, and mammals. The celibate subordinate males, deprived of sex, may lose the ability to get an erection. This form of animal erectile dysfunction, or “psychological castration,” may be temporary and reversible, but it also may last a lifetime.

  But modern human sexual encounters are not typically interrupted by predators leaping from the bushes or sexual competitors grabbing mates away. So I asked the UCLA urologist and impotence expert Jacob Rajfer whether psychological stress could interfere with male erections. “Yes,” he told me simply. “Some men under stress have difficulty with their erections.” When I asked him to specify what kinds of stress, he just laughed. Getting older, problems on the job, or relationship troubles can strain the modern male. Wary dread can come in the form of a looming deadline, a lawsuit, or crushing credit card debt. Stress extinguishes erections—whether human or animal—through activation of the sympathetic nervous system. Failed copulations across species are connected through ancient neural feedback loops that protect mating males. This illustrates the remarkable power of the brain over the penis. While losing an erection in this way can be frustrating and perhaps embarrassing for a patient, the connection itself isn’t pathological. And it’s certainly not unique to individual men. To keep animals from getting eaten or beaten up in the act, threats should trip the circuit breaker of sexual activity.

  During millions of years of matings in a dangerous world, some males have evolved the ability to ejaculate as quickly as possible. Males that could speedily transfer sperm before a jealous competitor or hungry predator pounced would live to mate another day, and their sperm would stand a better chance of fertilizing. Moreover, speedy ejaculation might also have given a reproductive advantage to males attempting to inseminate many females in a short time frame.

  But, like the coitus interruptus of erectile dysfunction, coitus accelerando has been pathologized. We human doctors call it premature ejaculation (PE). According to Arthur Burnett, the Johns Hopkins urologist, ejaculation problems are actually more common than erection issues, although fewer men seek medical attention for them. For other animals, however, it’s not necessarily a problem. In fact, it may be an advantage.

  In a 1984 paper, Lawrence Hong, a sociologist at California State University, Los Angeles, suggested that “an expeditious partner who mounts quickly, ejaculates immediately, and dismounts forthwith might be best for the female.”

  Indeed, many animals do transfer sperm promptly.h Human males take, on average, three to six minutes to go from vaginal penetration to ejaculation. Our closest genetic relatives, chimps and bonobos, do it in about thirty seconds. Stallions typically ejaculate after only six to eight thrusts. Some birds that lack penises transfer sperm in just a fraction of a second, by touching their genital openings to the females’, a process that has been described as a “cloacal kiss.” Small marine iguanas native to the Galápagos Islands have developed the ultimate in early seminal emissions: they can ejaculate prior to copulation. Ordinarily, marine iguanas need almost three minutes to ejaculate inside a female. This benefits larger, higher-ranking iguanas with the right and brawn to push a smaller male off a female. So smaller iguanas masturbate and cleverly store their semen in a special pouch. In the first few seconds after penetration, the sneaky little iguana slips the semen into his partner’s genital opening, called a cloaca. By the time the larger iguana pushes him off, his swimmers may well be on their way to fertilizing the female’s eggs.

  There may be another benefit to speedy mating. Time-limited contact, particularly between moist mucus membranes, reduces the risk of transmitting pathological microorganisms. For many animals, parasitic infection poses a deadly threat. In these populations, fast copulation might be advantageous. (For more on animals’ STDs, see Chapter 10, “The Koala and the Clap.”)

  Jacob Rajfer, the UCLA urologist, pointed out to me that PE affects a remarkably consistent 30 to 33 percent of men of all ages—from their early twenties through eighties. The incidence of ED, on the other hand, tends to increase with age. To Rajfer, this means PE is what doctors call a “normal variant”—and likely highly heritable. He summed PE up in a sentence: “I don’t consider it pathological.”

  Whether the thrusting that precedes ejaculation lasts three hours or three seconds, the delivery of the payload to the female fulfills the reproductive function. PE as pathology is a new wrinkle in the long evolutionary success story called premature ejaculation. And this knowledge should console early climaxers. Because while it’s sometimes embarrassing or perhaps unsatisfying today, instant ejaculation—and the neurocircuitry underlying it—has given hundreds of millions of ancestral ejaculators a head start in what biologists call the “sperm competition.”

  In my first year of med school, the highlight of the spring semester was Movie Night. Carrying tubs of popcorn, sodas, and giant bags of candy—some of us wearing pajamas and slippers—my classmates and I packed into the university auditorium and settled in. The lights dimmed, we sat back, and for the next four hours, we watched tape after tape after tape after tape … of the hardest-core pornography our professors had been able to procure.

  The thinking was that, as future doctors, we needed to be familiar with the tremendous range of behaviors the human body, mind, and libido can get up to. We had to be able to conceal our shock (or arousal?) when a patient confessed some kinky predilection. We required background knowledge to be able to reassure concerned patients when they were normal. We needed to know what was normal and what even the sex industry considered out-of-the-box. And frankly, for many of us book-smart science nerds, we just needed to have our eyes opened.

  Veterinarians require no such seminar. As hilariously—and exhaustively—cataloged by writers like Mary Roach, Marlene Zuk, Tim Birkhead, Olivia Judson, and Sarah Blaffer Hrdy, the sex lives of animals make for reading that is almost comically pornographic.

  These writers are documenting a massive shift in what biologists know—or are willing to admit they’ve observed—about the sex lives of other animals. If you’ve ever watched, mortified, as your dog mounted a dinner guest’s leg, you may have given some thought to animal masturbation. But until recently—even with much evidence to the contrary—genteel biologists held that animals don’t masturbate. Their fig leaf was the argument that masturbation is not procreative; ergo, animals would have no evolutionary urge to pursue it. In fact, however, both sexes of many species are inventive self-pleasurers in the wild. Orangutans self-stimulate using dildos they make out of wood and bark. Deer find their antlers autoerotic. Birds masturbate by mounting and rubbing against clumps of mud and grass. Daddy longlegs spin two threads of silk upon which to rub and stimulate their genitals. Male elephants and horses rub their erections against their bellies. Lions, vampire bats, walruses, and baboons use paws, feet, flippers, and tails to stimulate their own genitals. Livestock farmers and large-animal veterinarians have long noticed masturbation in bulls, rams, boars, and billy goats, and have even calculated what time of day it is most likely to occur (5 a.m. appears to be a favorite hour for many bulls).

  Mutual masturbation has been documented in many species. Bats and hedgehogs include oral sex as a common component of their sexual encounters. Blowhole sex in dolphins has been observed by marine biologists. Bighorn sheep and bison have frequent (homosexual) anal sex. Spinner dolphins, herons, and swallows engage in group sex. And bonobos … well, those well-
publicized lascivious close human relatives seem to do it all.

  Male-male and female-female mounting has long been observed in livestock (in fact, watching for females to mount each other is an old rancher’s trick for discerning when cows are in estrus and ready to breed). But until the last decade, animal homosexual behavior was explained away, pathologized, or entirely ignored by academia and even by popular naturalists. That changed around the end of the 1990s, with the publication of several books, including Bruce Bagemihl’s Biological Exuberance, Marlene Zuk’s Sexual Selections, and Joan Roughgarden’s Evolution’s Rainbow, which brim with examples of the hundreds of species that show homosexual, bisexual, and transgendered tendencies and behaviors. Bagemihl includes a many-hundred-page “Wondrous Bestiary” that catalogs sightings and descriptions of these behaviors in wild primates, marine mammals, hoofed mammals, carnivores, marsupials, rodents, and bats, as well as a huge range of birds and even butterflies, beetles, and frogs. Roughgarden details genital licking and anal sex in bighorn sheep; penis fencing in bonobos; lesbian mounting in Japanese macaques; and the all-male orgies of giraffes, orcas, manatees, and gray whales … among many other combinations, species, and activities. Marlene Zuk and Nathan W. Bailey have studied female same-sex parenting behavior in Laysan albatrosses and reported on the genetics of fruit fly homosexual behavior.

  Clearly it’s time to put to rest the idea that homosexuality is somehow unnatural, particularly if your definition of “unnatural” is something not found in nature. Indeed, as Bagemihl notes, “The capacity for behavioral plasticity—including homosexuality—may strengthen the ability of a species to respond ‘creatively’ to a highly changeable and ‘unpredictable’ world.”

  It should be noted that same-sex sexual behavior is not necessarily the same as same-sex preference or orientation, both of which are harder to prove and less well documented in the wild than individual same-sex activities. Nevertheless, many human and nonhuman animals alike regularly engage in same-sex behaviors including oral sex, anal sex, group sex, and mutual masturbation.