Males Are Brutes, Biologists Say New Studies Examine Sex Harassment Among Bugs, Mammals
Birds do it, senators do it, even fuzzy little bees do it: They engage in the ancient art of sexual harassment.
Stress it on the first syllable or stress it on the next, but harassment probably is as old as the partition of sex cells into sperm and eggs.
Indeed, the more carefully biologists survey the field, the more often they spy examples of males hounding females (and, on occasion, the reverse) to listen up, settle down and mate, mate, mate.
Two papers on the subject of sexual harassment and coercion appeared recently in the journal Animal Behaviour, one an in-depth study of sexual harassment in a species of solitary bee, the second a sweeping overview of harassment among a broad variety of animals.
The take-home message is that males often will do whatever they can to seize the resource they covet most: female sexuality. As for their methods, we’re not talking champagne and soft jazz.
A male may follow a female around, biting or slapping or screeching at her until she relents, as often happens among chimpanzees. Or he may skip the warm-up and simply rape her, as young male orangutans do nearly every time they encounter a female. Among sea otters, a male may grab a female’s snout with his teeth or claws and drown her while attempting to mate.
“It’s all very squalid and depressing, but there we are,” said Dr. Geoff A. Parker of the University of Liverpool in England. Parker and a colleague, Dr. Timothy H. Clutton-Brock of the University of Cambridge, wrote one of the two Animal Behaviour papers.
Researchers long have known that male and female animals struggle endlessly with a fundamental paradox: They need each other to reproduce, yet they have very different notions of how that need should be filled.
Females usually - though not always - do most of the child care, investing in each of their young the nutritionally taxing contents of an egg or the even more expensive milk of the breast; with that high investment comes a female’s desire to mate with the male of her choice and ignore the rest. Afterwards, she’s got work to do, turning her attention to the demands of maternity.
In contrast, males often have nothing to do with their young beyond tossing in half a genome - and the more semi-genomes they can get into the pool, the better. Unlike the big, nutritious egg, their sperm cells usually are abundant and comparatively cheap to manufacture.
Males also must move quickly to beat out competing males, which means, in many cases, imposing themselves on a female without giving her a chance to pick and choose.
Not every act of male aggression hurts the female, and sometimes a female appreciates a rousing display of male savagery, seeing it as evidence of strong genes or the ability to guard the territory against intruders. But when the costs to the female of male pushiness outweigh the benefits, then biologists call it sexual harassment.
“Among humans, anything you don’t like can be called harassment,” said Dr. Graham N. Stone, an entomologist at Oxford University in England and author of the second report.
“Biologists don’t define it that way. You must be able to identify an unequivocal cost of the male activity to female fitness, and that isn’t always easy to do.”
In one of the first attempts to measure the precise cost of harassment, Stone focused on the solitary bee, Anthophora plumipes, a long-tongued, fast-flying insect common in Britain that, unlike the more familiar honeybee, lives, forages and breeds on its own, rather than as part of a social hive.
With Anthophora, Stone sees a clear case of male harassment. When a female is fertile and eager to mate, she makes her desires obvious, synchronizing her flying times to encounter males and freely allowing a male (or two or three) to copulate with her.
But males do not restrict themselves to her schedule. They constantly are on the prowl for females, and they will fly toward anything that is black, the color of their beloved: other black bees, blackbirds, black cats. “One of them tried to copulate with somebody’s black shoe,” said Stone.
And when a male finds a true Anthophora female rummaging for nectar through a bush of comfrey, he will pounce on her, often knocking her to the ground.
The male cannot hurt the female or force her to copulate - she is considerably bigger than he is, and when she does not want sex, she tucks her genitals underneath her and shakes him off her back.
Yet, even though the male usually strikes out, it is worth it from his perspective to keep trying. Once in a while, he may meet a willing female, and he has nothing better to do with his time or energy anyway.
Not so for the female, which is where the calculation of the cost of harassment comes in. Beyond mating, she must locate a nest site, build cells within the nest for the eggs and provision the cells with nectar and pollen. Her adult life span is brief - six to eight weeks - and she must work quickly.
Thus, constant male harassment can cut significantly into her ability to feed her offspring. Stone has observed that when male patrolling of a comfrey bush is at its maximum, a female may be pounced on once every three seconds.
He also has observed that females take steps to avoid male harassment. They may try chasing away males or, more likely, they may choose to avoid foraging in the outer flowers of a comfrey bush and instead move toward the interior and sample the flowers there, where the males do not bother going.
Here is where the cost comes in.
Measuring the nectar content of inner and outer flowers, Stone determined that the outermost ones had the highest volume and concentration of sucrose. More significant, he clocked the amount of time required to forage from the outer and the inner flowers and found that it took 9.1 seconds to push aside the leaves and visit the interior blooms compared with just five seconds for the external flowers.
In sum, the requirements of avoiding pesky males meant that the females spent twice as long seeking nectar than they would have otherwise.
But lest it begin to sound as if females are pathetic and helpless victims, the authors describe a number of female counter-strategies. Like Anthophora bees, many female animals simply avoid males and will leave an area when a male comes sauntering along, as many species of cats are known to do.
Some females take a feminist approach, forming coalitions with other females. This strategy is most elaborate among the bonobo, or pygmy chimpanzee, in which females cement their social bonds with frequent genital-to-genital rubbing and jointly keep immigrant males from intruding on their group. In at least two cases, coalitions of female bonobos have killed offending males.
Among damselflies and African swallowtail butterflies, there are two different female “morphs,” one looking like the traditional female, the second having a more malelike appearance.
Studies have shown that females with the masculine disguise are much less likely to suffer constant male harassment, although these so-called “andromorphs” can attract a sex partner when they want him by releasing alluring pheromones.
But perhaps no other female has mastered mimicry as well as the spotted hyena. Both females and males have masculine-looking genitalia. In this species, male aggression against females is exceedingly rare, and the female hyena may be said, in a Freudian sort of way, to have had the last laugh.