The Myth of Monogamy: Fidelity and Infidelity in Animals and People (11 page)

The pattern persists: Genetic paternity correlates with acting paternally. But not always. Especially among some socially monogamous species, males do not consistently reduce their paternal solicitude following behavioral evidence of their mates' infidelity. Maybe they just don't "understand" what has happened, or perhaps their paternal inclinations are so hard wired that they simply don't have enough flexibility to adjust. In any event, it is interesting that the strongest evidence for precise adjustments by males to the EPCs of females comes from cooperatively breeding species such as the dunnock, where several males might be associated with one female. Here, males care for offspring in proportion to their likelihood of being the father; if several males have copulated with one female, each male will provide food, for example, proportional to his degree of sexual access. (More copulating, more food-bringing.) In another cooperatively breeding bird species, the acorn woodpecker, when dominant males are experimen-

undermining the myth: males 49

tally removed from the group, they respond by infanticide, destroying eggs laid while they were out of the reproductive picture. The likelihood is that in such species, males are often exposed to variations in the probability of being fathers; hence, they have the behavioral repertoire to detect such probabilities and to behave accordingly. Perhaps in cases of ostensible monogamy, females are normally so adroit at hiding their EPCs that males have not evolved a response.

There are other interesting avenues connecting EPCs and parental behavior. We have already looked at the peculiar trade-off between mate-guarding and gallivanting, with one precluding the other. Males also appear to be influenced by another balance point: between gallivanting (going in search of EPCs) and staying home to help take care of the kids. As with gallivanting versus mate-guarding, males can't have it both ways; if they are off trying to spread their seed, they cannot very well also be home tending the fruits of that seed.

In many colonially nesting bird species (e.g., terns, herons, social gulls), there is comparatively little EPC activity, perhaps because the females breed synchronously; that is, they are all likely to breed at about the same time. As a result, a male who gallivants runs the risk that his own female will cuckold him. By contrast, most songbirds appear to engage in EPCs if they can. Although they breed seasonally, they are not truly synchronous, so a male can inseminate "his" female, guard her against other males while she is fertile, and then proceed to seek other females who may be just entering their fertile period. Also, many males seem to use a "switching" strategy: After their eggs have hatched, they abandon gallivanting and become doting fathers ... because at this point the genetic payoff exceeds that from seeking EPCs.

For example, male indigo buntings seek EPCs while their mates are incubating--at a time when there is relatively little that the males can do to aid their offspring. Paternal behavior competes with trying to get EPCs: In most species of birds, males provide quite a bit of parental care during chick-rearing, much less during nest-building or incubation. It may be no coincidence that in these early stages of the breeding cycle, males have the prospect of achieving one or more EPCs; hence, they are more likely to gallivant. By the chick-rearing stage, most fertile females have already been inseminated, so the best thing a male can do is help rear the offspring he has (presumably) fathered.

On the other hand, more effort is probably required to rear hungry, fast-growing chicks than to build a nest or sit on the eggs. So male birds may put more effort into chick-rearing simply because, at this point, females are less able to succeed as single parents.

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THE MYTH OF MONOGAMY

The decision for many males comes down to this: Seek EPCs or be a stay-at-home parent. It is a trade-off between two kinds of striving: mating effort (trying to obtain as many copulations as possible) versus parental effort (trying to enhance the success of those copulations already achieved). Males typically do whichever offers a better return. For example, if there are fertile females nearby, EPCs--mating effort--may be favored; if there are lots of predators, parental effort; if there are lots of other gallivanters, mate-guarding combined perhaps with parental effort; if your offspring have especially high metabolic needs, parental effort; if your mate has likely copulated with other males, less parental effort and more mating effort (with that same female or others); and so forth.

Earlier, we encountered hoary marmots, caught in the dilemma of whether to mate-guard or gallivant in search of EPCs. Sometimes these animals live rather isolated lives, the basic unit consisting of one adult male, one or two adult females, and their offspring, with no one else nearby. In other situations, hoary marmots occupy bustling colonies, such that although a male is likely to mate with one or two nearby females, there are also many additional females--and males--in the immediate vicinity. It turns out that isolated males are rather good fathers, highly attentive to their young, whereas those occupying busy colonies spend their time wandering about in search of EPCs or mate-guarding, defending their females from other males in search of EPCs. Their offspring get short shrift.

We have long known that there is considerable variation in the extent of male parental care; generally, those species more inclined to monogamy are more likely to be good fathers. Recently, it has become clear that there is also quite a range of paternal behavior within most species as well. Attractive males usually provide less parental care, so that females end up doing relatively more mothering when they are paired with "hunks." This tendency is captured in the seemingly dry title of this scientific article: "Paternal Contribution to Offspring Condition Is Predicted by Size of Male Secondary Sexual Characteristic." The greater the male's secondary sex characteristics, the less his contribution. It is as though desirable males know they are desirable, and so they are likely to shop that desirability around; by the same token, those "lucky" females who get to mate with such studs find themselves less lucky when they are stuck with most of the household chores.

Imagine, for example, a type of bird in which males with bright red spots are especially successful in seducing females. Now imagine a male whose spots are particularly bright and red: Because he is so sexy, his efforts at EPCs are likely to bear fruit, and so .he spends most of his time gallivanting about, leaving his mate to pitch in with the kids to make up for the deficit.

undermining the myth: males 51

Don't expend too much pity on Mrs. Stud, however: First of all, it was her choice to mate with the lazy, conceited jerk, and second, in all likelihood she will profit genetically from the transaction, since her sons will probably inherit their father's dashing good looks--as well as his lousy paternal habits--and also, therefore, his attractiveness to a new generation of eager females. As a result, the hardworking female will likely have more grandchildren via her male offspring.

Incidentally, long-tailed male barn swallows fly less efficiently than their short-tailed counterparts, so the fact that such males are more inclined to be dead-beat dads may be due at least in part to the fact that it is more difficult for them to perform the normal activities of barn swallow parenting--specifically, catching insects on the wing and bringing them back to their brood.

By contrast, comparatively unattractive males are more inclined to be good fathers. It appears that they make the best of their bad situation by behaving as paternally as they can, even though some of the offspring thus aided are not their own. Among purple martins, for example, young males--especially prone to being cuckolded by their mates and also unable to recoup much by way of obtaining their own EPCs--behave as paternally as do older males, despite the fact that their payoff is lower (since many of their nestlings will have been fathered by those older males). They simply have nothing better to do.

Females don't always share the male enthusiasm for EPCs. And so, we come to rape. Some biologists prefer the more genteel phrase "forced copulation." But anyone who sees the phenomenon among animals is unlikely to have much doubt what is going on. Normally, sex among animals involves an extensive sequence of courtship interactions that are clearly consensual, in which the two participants bow, nod, sing, burble, prance, twist their bodies, arch their backs, curve their necks, exchange ritual food items, do a nifty little dance, clatter their beaks, bills, or muzzles together, wave their arms or wings, flap their ears or flare their nostrils, prance and strut, preen and groom each other, bill and coo in romantic synchrony, and, all in all, make music together, which, even when not beautiful, is at least mutual. In short, they
go
through a rather elaborately choreographed and predictable pattern that eventually results in their becoming sexual partners. If one would-be lover misses a cue, or otherwise behaves inappropriately, the courtship may be broken off. Assuming all goes well, however, the mated pair eventually copulates, and although their coupling may not always meet the human definition of

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THE MYTH OF MONOGAMY

"romantic," it is at least likely to be well synchronized, smoothly accomplished, mutually arrived at and agreed to--a pattern of consent that is further underlined if the partners remain together in some kind of social bond (such as we identify with monogamy).

By contrast, it is very different thing when one or more males descend upon a female, whether mated or not, and immediately force a copulation, which generally includes ejaculation, without a "by your leave." The female typically struggles vigorously and may sometimes escape; her mate, if present, generally tries to drive away the attackers. No subsequent social relationship is established between the violators and the victim, who is not uncommonly injured in the sexual attack. Sometimes fertilization results. If this isn't rape, what is?

David and others have documented a violent and brutal pattern of forced copulation among mallard ducks, for example. The act occurs most commonly when the drake is some distance away, and it unfolds much like a gang rape among human beings. A small flock of males swoops down upon a hapless female; the victim struggles vigorously, trying to escape. Neither she nor her attackers engage in any of the shared niceties that characterize typical courtship between a pair of mated mallards. And no subsequent social relationship is established. Although females thus attacked are sometimes drowned in the process, raped mallards often survive and bear their victimizers' offspring.

Behavior of this sort has been described extensively among animals as diverse as fruit flies, mole crabs, scorpionflies, crickets, desert pupfish, guppies, blueheaded wrasse, bank swallows, snow geese, lesser scaup and green-winged teal (duck species), African bee-eaters, laughing gulls, tree shrews, elephant seals, right whales, bighorn sheep, and feral dogs. This list will undoubtedly grow as the number of long-term behavioral studies on animals increases. To some extent, it is also a matter of taking a clear-eyed look at phenomena that have already been well "known" (that is, described) but not correctly interpreted. For example, it has long been known that up to a dozen or so male house sparrows will often congregate around a female. These agitated gatherings of males used to be called "communal displays" before their true nature was recognized. They are multi-male EPC attempts. Since in nearly all cases the female resists, they could also be called "gang rapes."

In any event, there is simply no question that Susan Brownmiller, author of the best-selling book
Against Our Will,
was flat-out wrong when she asserted that rape is unique to human beings. It is not.

Rape also appears to be common among primates, having been reported in rhesus monkeys, talapoin monkeys, vervet monkeys, stumptail macaque

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monkeys, Japanese macaques, spider monkeys, gray langurs, gorillas, chimpanzees, and orangutans.

In a sense, such cases are fair game for this book, since they represent departures from monogamy. When female ducks are raped, this might seem yet another type of EPC; after all, they are indeed extra-pair copulations and can result in mixed paternity. The threat of rape may even motivate a substantial proportion of animal mate-guarding, just as its reproductive consequences may well include a reduction in the mated males' inclination to behave paternally toward any offspring conceived as a result. But for our purposes, it is more interesting to focus on those situations in which those individuals going outside of monogamy are doing so "of their own free will."

This is a difficult and slippery slope, however, for several reasons. First, free will among animals (not to mention people!) is a much-contested topic. Scientists generally steer clear of it, preferring to deal with what animals actually
do,
instead of whether or not they have any choice in the matter. Second, although being a rape victim seems an extreme case of being deprived of one's autonomy, an argument can be made that all the decisions an animal--or a person, for that matter--makes are done under duress: If a male songbird goes in search of EPCs "because" he carries a genetic tendency to behave this way (because his father did, which earlier contributed to his being conceived), is he really acting of his own free will? And if a female blackbird copulates with a neighboring male in order to gain access to his food supply, or a female barn swallow does the same in order to gain access to a particular male's genes, isn't she also the victim of a kind of coercion? Nonetheless, there is a common-sense distinction to be made between coercion orchestrated by the conflicting will of another individual (rape, social subordination, etc.) and coercion that results from the pressure of circumstance (e.g., shortage of suitable food or genes).