Remarkably, lionesses appear to have evolved to do just that. Yes, they appear to be able to improve the odds that their sons will have coalition partners. Analyses of lion birth records show two significant patterns. The first is that when a female gives birth to a large litter, it will typically contain more sons than daughters. The second is that when several females in a pride give birth simultaneously, the cubs are disproportionately male. How do females synchronize the births? Remember that when a new group of lions takes over a pride, the first thing they do is kill or chase out any cubs that are around. This brings all the females back into heat. As a result, the females become pregnant at about the same time and give birth at about the same time, thus producing a large cohort. (Later in the males' tenure in the pride, births are less synchronous.) And sure enough, lionesses tend to have sons rather than daughters in the first pregnancy after a takeover. How they manage to do this is, however, unknown.
So you see, my walleyed friend, if your mother took a leaf from the lion's book, you won't raise your tail in vain.
Dear Dr. Tatiana,
Â
Maâam, I'm a field cricket, and I'm mighty annoyed. I've been singin' and singin', but there's not a gal in sight. The last one I saw went off with a creep who'd been skulkin' in the bushes, and I got left with nothin' but a few flies. Am I doin' something wrong?
Â
Hoppin' Mad in Texas
You've been a victim of the infamous “let the other guy pay for dinner, I'll go home with the girl” strategy. I'm sure everyone knows someone who gets away with this. I know I do. But the problem is most acute among species where males announce their whereabouts to any girls who might be passing by. While some males perform, others lurk. In some Caribbean ostracodsâthe shrimp that look like kidney beansâmales give off sexy bursts of light as they bob in the water just after dusk falls. How do they make light? They secrete chemicals that react with the water to produce a glowing spot. As the male swims, he leaves behind a trail of light. Different species produce light at different ratesâand leave different trails. If you were to run a net through the water column, however, you'd find a lot of males bobbing along without flashing, presumably hoping to intercept females attracted by the pulsations of signaling males.
Parasitism of this kind is obviously a tactic that, for its success, depends on the relative numbers of parasites and performers. You can't all be parasites: after all, someone has to sing for supper. In any event, given that there's a drawback to remaining silentâgirls typically prefer singers to skulkersâwhy don't all males just sing?
For a number of reasons. Among bullfrogs, for example,
skulking is a matter of necessity, not choice. Bullfrogs breed in ponds, and the biggest males sing from the territories that they holdâand defend vigorously. If they see a trespasser, they wrestle himâand if they win, they teach him a lesson by holding him under water for a few minutes. (Why don't they drown him and be rid of him? Who knows. Perhaps they don't want rotting bodies fouling the water.) Since size is always an advantage in wrestling, the little guys rarely win. So they keep a low profile, hiding in the water at the edge of a territory with only their heads sticking out, ready to surprise females on their way to the big male. But among field crickets such as yourself, the reason for silence is different. It's those flies you mentioned.
Female field crickets much prefer singers. Unfortunately, so do females of another kind: parasitic flies. These deposit their larvae on the singer's body; the larvae burrow inside and eat away the singer's flesh. Death follows within a week. Whether a cricket becomes a singer or a skulker has a strong genetic componentâsome males are naturally less inclined to sing than others. But whether skulkers fare better than singers depends on the abundance of the parasitic flies. In years when flies are abundant, skulkers do better and their genes spread. In years when flies are scarce, singers do better and their genes spread.
It's a nasty, brutish world. Fringe-lipped bats pick off calling frogs. The bats know their stuffâthey can tell the difference between species that are poisonous and those that taste nice, and between those that are too big to handle and those that are just right. Little blue herons go after calling male crickets. Mediterranean house geckos sit silently outside the burrows of male decorated cricketsâand snaffle up any females who come to hear the song. And so it goes.
Even worse, some predators don't just exploit these mating signalsâthey mimic them. Bolas spiders, for example, are
chemical chameleons. Adult females, which are sedentary and plump and have coloring reminiscent of bird droppings, have evolved an unusual hunting technique. They catch prey by swinging a kind of lasso. The lasso is made of a sticky ball attached to the end of a thread, which the spiders use one of their front legs to swing at passing insects. In some species, the spiders even whirl the lasso around their heads as if they'd stepped out of a spaghetti western. How do they bring their prey within range? When they are hunting, they give off the scent of female moths. Sure enough, male moths come flying over to investigate. Poor fellows. If they are caught, they are wrapped in silk and hung from a thread until the spider is ready to eat them. (Different species of spider give off different scentsâand attract different species of moth.)
Remarkably, both juvenile and male bolas spiders also hunt by giving off a female scentâalthough this time, by an amusing coincidence, the scent is that of female moth flies, flies that look like miniature moths. Why do males hunt like juveniles? Males typically grow little after hatching (and are thus far smaller than their mates). Males and juveniles do not use a lasso, probably because they are too small to manage it effectively. Instead, they capture prey using their four front legs.
Occasionally, though, the prey bites back. Take the digging wasp
Oxybelus exclamans.
These wasps are liable to have their nests taken over by an insect version of the cuckoo: a flesh fly that lays its eggs in the cells of a wasp nest. When the fly larvae hatch, they eat all the food that the wasp had provided for her own children. Male flesh flies loiter around wasps' nests in the hopes of meeting female flies. If they're not careful, though, these fellows will find that the wasp has captured
them
for her children to eat.
As for
your
problem, if you see another of those flies, I urge you to go straight to the doctor. You may need major surgery.
Dear Dr. Tatiana,
Â
I'm a marine iguana, and I'm appalled by the behavior of the young iguanas of today: I keep encountering groups of youths masturbating at me. It's revolting. I'm sure they didn't dare act this way in Darwin's time. How can I make them stop?
Â
Disgusted in the Galápagos
I get a lot of letters from young male marine iguanas, frustrated because the girls ignore them. But this is the first time I've heard complaints from the other side. Look at it from the guy's point of view. Here he is, a tasteful shade of red, his spiky crest a full twenty centimeters from his crown to his tailâhe's ready to go, desperate to use one or the other of his penises (yes, like many reptiles, he has two, a left and a right penis). But being young and therefore small, he doesn't have much of a chance. It isn't just that you ladies prefer to mate with older, bigger males. It's that even if he manages to mount a female, the odds are he'll be shoved aside by a bigger fellow before he climaxes. That's why young males masturbate when they see a girl go by. Wanking reduces the time they need to ejaculate during sexâand thus reduces the risk of being interrupted before their climax. So I'm afraid the behavior may be here to stay. Young wankers probably sire more children than those who abstain.
Does anyone else masturbate? Yes. In many primates, individuals of both sexes masturbate a lot. Take the sooty mangabey, a smoke-colored monkey from West Africa with a long tail and extravagant tufts of whiskers on its cheeks. Some females use their hands to stimulate themselves during sex. Male and female orangutans stimulate themselves with sex toys they've made out of leaves or twigs. One female chimpanzee who was raised in a
human household masturbated to a copy of
Playgirl,
thrilling to the photos of naked human males, especially the centerfold. Other mammals masturbate too. Male red deer do it by rubbing the tips of their antlers through the grass. The whole act takes fifteen seconds from start to spurt, and during the breeding season some stags masturbate several times a day. But does anyone else do it, like marine iguanas, out of fear of being interrupted in bed? Frankly, the matter hasn't been the subject of much research. There has been more work on a related topic: big balls.
Big balls are a more conventional way for small males to increase their odds of fertilizing eggs. The logic is simple. In species where small males have to sneak to mate, they are guaranteed to be at risk of sperm competition. As you know, sperm competition is often like a raffleâmore tickets, more chances. Therefore, small males who invest a larger proportion of their bodies in making sperm can buy more raffle ticketsâand better their chances of success whenever they mate. Meanwhile, large males, as long as they are reasonably effective at guarding females, don't need so many tickets or such big tackle.
That's why there's often no relation between the dimensions of a man and the dimensions of his privates: bigger men do not necessarily have bigger bits. Indeedâmore's the pityâit's often the opposite. The plainfin midshipman, otherwise known as the California singing fish, takes this to extremes. Males have either big brains or big balls. The brainy kind excavate cavelike nests beneath rocks in the intertidal zone. Once a male has prepared a nest, he hums to attract females. A single humming bout can last for a quarter of an hour. Thus, he has large muscles for humming and extra neurons to control the muscles. When a female arrives, she slowly lays her eggs on the ceiling of the nest; as she does this, the male quivers beside her every few minutes, a sign he is releasing sperm. When she's doneâwhich can be as long as
twenty hours after the laying of the first eggâhe throws her out of the nest so that he can guard the fertilized eggs and sing to attract more females.
The other type of maleâthe one with the big ballsâsneaks into the nest at the crucial moment. These fellows can't hum: they lack the mental and physical apparatus. The best they can do is grunt. But boy, are they well hung! As a proportion of his weight, a sneak has gonads nine times heavier than a brainy male does. His gonads are so large that his stomach bulges as if he's pregnant. No wonder he grunts.
So you brainy types out there shouldn't feel too smug. Your position is only safe if sneaks are rare. If sneaks are common, then you're at greater risk of sperm competition and should invest more in making sperm. Thus you should have larger balls. Compare two species of dung beetle,
Onthophagus binodis
and
Onthophagus taurus.
These are among a score of dung beetle species introduced to Australia from other parts of the world. You see, Australia had no native cows, and so when humans imported them, the cows produced more dung than the native dung beetles knew what to do with. As a result, large quantities of cow manure accumulated in pastures. To solve this problem, dung beetles with a talent for disposing of cow dung were invited to immigrate. Which is to say, dung beetles were captured in other parts of the world, quarantinedâI love the thought of an insect quarantineâand then released in Australia.
To return to the matter at hand,
Onthophagus binodis
and
Onthophagus taurus
have similarâand by now, familiarâbiology. Males again come in two sizes, big ones with horns, little ones without them. (In
O. binodis,
the big males have a single horn on their backs; in
O. taurus,
as the name suggests, they have two curved horns on their heads.) Males and females meet at fresh mounds of dung. Females pair up with big males, and together
the pairs dig burrows, pausing from time to time to copulate. (Copulation in dung beetles has rarely been observed, but in
O. binodis,
the male caresses the female with his first two pairs of legs, mounts her, and then goes into spasms during which he taps her back with his front legs.) A typical burrow has several passageways branching off from a central corridor. At the end of each passageway, the beetles deposit a wad of dung. The female lays a fertilized egg on the wad and then seals off the passageway with earth. Although the male will give his partner lots of help collecting dung and so on, he does not like to leave the entrance of the burrow unattended. This is a wise precaution, since the small males rush into the burrow when the big one isn't looking and copulate with the female. Sometimes, the small males are even sneakier and dig their way into burrows, erupting through one of the walls.
Sneak attacks are more likely, however, to be a problem for
O. taurus
than for
O. binodis.
In
O. binodis,
sneaks constitute only a third of the male population. Any particular big male is therefore at low risk of cuckoldry. And sure enough, in this species, a little male expends more on sperm production than a big male does, having both larger testes and a higher sperm count. By contrast, in
O. taurus,
almost two-thirds of males are sneaks. Accordingly, in this species, big males and little males are indistinguishable on the basis of balls alone.