Animal Attraction

By David Bjerklie

FEMALES SCORNED When males are in short supply, females can become fierce competitors. Female house sparrows and great reed warblers, whose males often take two mates, may try to smash a rival's eggs. Unattached smooth newt females will steal a male's sperm packet just as he deposits it for his mate. Midwife toads are even more proactive: jealous females will tear copulating couples asunder.

LOVE CALLS It may not be Barry White, but the nonstop bellowing of a male red deer over several days is apparently quite effective at inducing reproductive readiness in females. Other species use more subtle signals to seduce their mates, including a full arsenal of sexy pheromones. A little of this chemical magic goes a long way: the merest trace of a female moth's scent will attract the attention of males from miles downwind.

SEX CHANGES Don't tell Nemo's dad, but if the female half of a pair of clown fish dies, the widower usually responds by turning into a female. In one species of marine worm, when two shes meet, the smaller becomes a he (but since males grow faster, they are likely to swap roles again). When too many male slipper limpets surround a female, the males change sex--then it's their turn to get hit on.

SHAGADELIC LOVEFEST If it feels good, do it. That seems to be the motto of the bonobos, whose same-and opposite-sex coupling seems as casual as a Hollywood air kiss and can include oral sex, French kissing and the missionary position. For these chimplike apes, sex serves as all-purpose social lubricant. Dolphins have no such excuses for their kinky behavior: they sometimes try to mate with sea turtles.

SPECIAL DELIVERY Love is war for the male paper nautilus, whose idea of sex is to heave his manhood--and his genes--like a tiny torpedo into the female. Once implanted, the male organ serves as a built-in sperm bank. Similarly, the male anglerfish burrows into the belly of its much bigger mate and becomes a permanent, parasitic testicle. The female green spoon worm inhales the tiny male, who then resides in the androecium ("little man house"), a nook in the reproductive tract from which he fertilizes eggs.

PREGNANT MALES Jokes about who wears the pants in the family are a corny stand-up staple. Tell that to the sea horse. It is the male who becomes pregnant, blows up like a balloon and delivers the young. The male Darwin frog swallows fertilized eggs and broods the young in his mouth. Ditto for the Japanese cardinal fish. In fact, males of many species--fish and fowl--are in charge of child care.

HERMAPHRODITES Changing sexes is one thing; being both sexes at once is quite another. Hermaphrodites abound in the animal kingdom: how sensible to be able to mate with whoever happens to knock on the door! Among those that can truly swing both ways are the sea slug, the earthworm and the European giant garden slug. The black hamlet fish is the rare vertebrate in which members of a mating pair can take turns being male or female.

CANNIBALS Love hurts--and in some species, it kills. For the praying mantis and the Australian redback spider, it's boy meets girl, girl eats boy. But not until boy passes along his genes to the next generation. In the marine bristle worm, however, it's boy eats girl. The male guards the fertilized eggs until they hatch, and since the female dies after mating anyway, the male sometimes has her for supper. For species that have little chance of mating again, a parent offering itself as a last meal can be a bit of insurance that the offspring will survive.

CRIMES OF PASSION Rough sex for many species can range from brutal love bites to lethal lust. Male dung flies, mountain sheep and some frogs, in their zeal to procreate, will swarm, harass and harm females, sometimes fatally. For Hawaiian monk seals, where males outnumber females 3 to 1, mating violence is so serious that biologists are worried that the species may be endangered.

TILL DEATH DO US PART And now for something truly unusual in nature: monogamy. For the black vulture, the California mouse and the chinstrap penguin, this rare state of affairs--or lack of affairs--is in the best interests of both male and female. Monogamy may not be for everyone, but staying faithful is sometimes the shrewdest reproductive strategy of all.

Source: Dr. Tatiana's Sex Advice to All Creation: The Definitive Guide to the Evolutionary Biology of Sex, by Olivia Judson