Biological Exuberance: Animal Homosexuality and Natural Diversity

than begins, with mating: the eggs develop within the female’s body and are then laid or discharged when ready to be fertilized (i.e., fertilization typically takes place outside the female’s body).¹⁰³ In addition to these delays and reordering of reproductive events, breeding can also, of course, be interrupted or terminated at any of these stages—this will be discussed in the next section, when we look at naturally occurring forms of birth control.

Another common misconception about animal heterosexuality is that only females experience periodic hormonal fluctuations in their reproductive biology. In fact, many male animals also have sexual cycles, entailing considerable periods in which they are sexually inactive and living separate from females. Occasionally, male and female sexual cycles are poorly synchronized or not optimal for breeding, as sometimes happens in Ostriches and Lovebirds. Male cycles are found in a wide range of animals, including primates, deer, seals, and numerous bird species, and usually entail a yearly, rather than a monthly, periodicity. In some instances, dramatic physical and physiological changes are involved. Male Wattled Starlings, for example, undergo regular periods of “balding” (feather loss) and wattle development, and males of many other bird species develop dramatic nuptial plumages associated with breeding. Male Squirrel Monkeys become “fatted” during the peak of their sexual cycle, while male Elephants experience “musth,” involving a whole host of changes such as glandular secretions, increased aggression, and rumbling vocalizations.

The significance of male sexual cycles has often been lost or overlooked under sexist biological theories, which tend to emphasize aspects of animal biology that confirm the unflagging “virility” of male animals, to the exclusion of those things that underscore the similarities between male and female sexuality. In fact, reproductive traits that are usually thought to be exclusively male or female can be found in members of the opposite sex in at least some species. Male pregnancy occurs in sea horses, for example, while lactation—milk production from fully functional mammary glands—was recently discovered in male Dayak fruit bats.¹⁰⁴ Females, for their part, can carry sperm within their bodies and “inseminate” themselves (as discussed above) or may possess elongated, phalluslike clitorides that can undergo erections (this is found in numerous mammals, including Spotted Hyenas, moles, and Squirrel Monkeys, as well as several flightless birds).¹⁰⁵ Some animals (e.g., Seals, Bears, Squirrels) even have a clitoral bone, homologous to the male’s baculum or penis bone in these species; in female Walruses, this bone may be over an inch long. Female pipefish and Japanese sea ravens (a kind of fish) even have extendable genital organs used to penetrate or retrieve sperm from their male partners.¹⁰⁶

When males and females do manage to get together, a formidable set of obstacles often stands in the way of achieving sexual contact and, ultimately, reproduction. Refusal or indifference by either the male or female partner is widespread and routine in the animal kingdom, and heterosexual matings are often “incomplete” in the sense that they do not involve erection, genital contact, ejaculation, and/or insemination. In one study of Chaffinch heterosexual copulations, for example, every “complete” and “incomplete” mating attempt was logged: out of 144 attempts, only 75 (52 percent) involved mounting with full genital contact (and therefore could potentially have led to fertilization). Of the remaining “unsuccessful” attempts, 76 percent entailed no mounting at all because one or both partners fled before copulation could take place, 9 percent involved the male mounting without attempting to make genital contact, in 8 percent mounting was terminated when the female refused to continue (in some cases after being pecked by the male), in 5 percent of the mounts the male slipped off the female’s back, while in 1 percent of the cases the male mounted in a reversed head-to-tail position and therefore did not make genital contact. In African jacanas, only about one in four sexual solicitations by the female result in the male actually mounting her.¹⁰⁷ In some species, completion of the sexual act is prevented because of interference from other animals, who actively harass males and females while they are copulating. This is typical of many primates, but has also been reported in some birds such as King Penguins, Kittiwakes, and Sage Grouse.¹⁰⁸

In a number of animals, it appears that male and female anatomy are not ideally suited to heterosexual interactions. The female Elephant’s vaginal opening, for example, is much farther forward on her belly than in other mammals. Although the male’s penis has a special shape and muscles that allow it to reach the female’s genitals, he still often experiences considerable difficulty in achieving penetration and may end up ejaculating on her anus or otherwise outside her body. Moreover, it is not true that male and female genitals always fit together like a “lock and key”: in many species the structural “compatibility” of the sex organs is less than perfect. In addition, the female’s internal reproductive tract in most animals is—in the words of several zoologists—a tortuous, obstacle- ridden pathway that is “remarkably hostile to sperm.” Its structure, chemical composition, and immune response to semen are actually designed to prevent most sperm from ever achieving fertilization, in part to protect the female from possible infection (sperm are, after all, “foreign” bodies) and in part to allow her to control paternity. ¹⁰⁹ Males and females may be anatomically incompatible in other respects as well. Biologists studying Musk-oxen have observed that the male’s build—a deep chest with short legs, and most of his considerable weight concentrated in the front half of his body—is decidedly ill-suited to mounting and clasping the female, and studies have shown that males are able to successfully mount females less than a third of the time.¹¹⁰ In many other species of hoofed mammals and seals where there is a significant size difference between the sexes, females often fall or are crushed under the weight of the male during copulation and may suffer serious (even lethal) injuries.

Sometimes outright hostility erupts between males and females, including chasing and harassment, as well as actual aggression, violence, and injury (inflicted by males on females and, less commonly, by females on males). Attacks can be as brutal as they are commonplace. Female Savanna (Olive) Baboons, for instance, are liable to be attacked almost daily by males without provocation, and each female is severely wounded about once a year; injuries are sometimes fatal. Sexual coercion (i.e., punishment or intimidation by males of “uncooperative” females) as well as outright rape also occur in a wide variety of animals, occasionally involving “gangs” of males that attack and forcibly mate with females.¹¹¹ Heterosexual rape is especially prevalent among birds such as ducks and gulls, but also occurs in mammals such as primates (e.g., Orang-utans, Rhesus Macaques), hoofed mammals (e.g., Bighorn Sheep), and marine mammals (Right Whales, and numerous seal species). In birds that form pair-bonds, rape usually involves mating attempts on females other than the male’s partner, but forced copulation within the pair-bond is not unknown, occurring, for example, in Silver Gulls, Lesser Scaup Ducks, and several other duck species.

Throughout the animal kingdom, heterosexual mating can be a dangerous and even lethal undertaking for females. Male Sea Otters often bite females on the nose during aquatic copulations, sometimes resulting in drowning or fatal infections; swarms of a dozen or more woodfrogs often try to mate with the same female, occasionally killing her in the process; female sharks of several species are routinely and severely bitten on the back during heterosexual courtship; while male mink may puncture the base of the female’s skull and brain with their teeth during mating. ¹¹² These are just a few examples of how heterosexual mating is often a destructive, rather than a procreative, act.

Animal Family Values: Birth Control, Day Care, Divorce, and Infidelity

Although two young are born [in Pronghorn antelope], four to six embryos are implanted in the uterus, where they fight to the death, so to speak, for the limited space … . Long projections grow out of the embryonic sheath which puncture other embryos, causing their death. All but two embryos are reabsorbed by the mother’s body.

—VALERIUS GEIST, “Pronghorns”¹¹³

When most people think about animal families, they imagine a mother deer lovingly tending her fawns, or a father bear diligently protecting mother and babies. The realities of animal heterosexuality are a far cry from this romanticized view. More often than not, a mother deer viciously drives her yearlings away from the family group (when she hasn’t aborted her fetuses, that is) while father bear rarely has anything to do with his family—and when he does, it is often to kill and eat them. This section examines some of the stark realities of animal “family life,” beginning with a look at the many mechanisms that animals use to avoid having families altogether, by limiting reproduction and eliminating offspring.

In addition to infrequent copulation or mating during times when fertilization cannot occur, several other forms of “birth control”—i.e., ways of preventing pregnancy—occur in animals.¹¹⁴ In fact, more than 20 different strategies have been identified whereby females are able to limit, control, or prevent insemination. The