Animals flout established rules when it comes to the game of love and sex. In fact, the animal kingdom is full of swingers.
Bonobos are highly promiscuous, engaging in sexual interactions more frequently than any other primate, and in just about every combination from heterosexual to homosexual unions. Mothers even mate with their mature sons (Everyone: Eeeeewww!). Bonobo societies "make love, not war," and their frequent sex is thought to strengthen social bonds and resolve conflict. This idea could explain why bonobo societies are relatively peaceful and their relatives, chimpanzees, which practice sex strictly for reproduction, are prone to violence.
Females of a tropical shorebird called a bronze-winged jacana have such gender-bending qualities that early ornithologists confused them for males. They are 60 percent larger than males, lay several egg clutches as if spewing sperm and leave the incubating of eggs and raising of young to a harem of males. Jacana girls will even invade another female's territory and kill a set of chicks, turning a devoted father into a bachelor that's available for courting. This unconventional behavior doesn't deter males, which vie for female attention by squawking at the top of their lungs.
Spotted hyena clans are socially matriarchal, with females dominating large groups of both males and females. The mating strategy is polygamous, however, with a male mating with many females. The female sports a penis-like clitoris, which contains the birthing canal and protrudes seven inches from her body. This awkward anatomy makes sex tricky since a male must crouch in a particular position so his penis can penetrate the clitoris. The pseudo penis also means females decide which males get access.
The wild relatives of chickens, red jungle fowl are promiscuous lovers. Since the jungle fowl stay close to home throughout their lives, sex can up the chances of mating with close relatives and delivering inbred offspring. Resisting incest can be difficult for the female fowl, which is dwarfed by the aggressive, sex-crazed males. To avoid the ill effects of brotherly love, the females store the male's sperm, and only after copulating does she somehow choose which sperm fertilizes her eggs.
Male walruses grab the attention of ice-lying females with loud vocalizations, including underwater bell-like sounds, clicks and pulses, as well as teeth-clacking and whistles above the surface. In this polygynous society, males defend a large harem of females that join him underwater for copulation. To keep up with so much water romping, the bulky bulls are equipped with a penis bone called a baculum, which extends up to 30 inches — the longest of any living mammal.
Sniffing butts isn't just for the dogs. Male lions can detect whether a female in his pride is in heat by smelling her reproductive organs. A lion pride consists of three to 30 individuals — many lionesses and a few males that have mating rights to the group. Females typically enter estrus at the same time, and over this four-day period they mate several times an hour. If the lioness fails to conceive, she will re-enter estrus about two weeks later and begin the mating cycle again.
To win a harem of females, males of the African blue-headed lizard joust each other with sideways blows of their tails. The winners not only take home cooing mates, they also get a coat of dazzling colors, while the losers turn a dull gray.
Sex in dolphin societies is as fluid as their aquatic undulations. The dolphins are promiscuous and mate for both reproduction and playful pleasure. Courtship involves the male posturing with his back arched and often nuzzling or even stroking a potential mate. If successful, the couple sidles up together belly to belly, and the male inserts his penis. The mating is swift, lasting under a minute, but is repeated several times with short breaks in between.
During mating season, male hanging flies take gift-giving to a new level. They offer females the corpse of a dead insect. If the female accepts the gift, the couple's genitalia link up and the female maneuvers until she is hanging upside down. During copulation, the female chows on her snack while the male supports her by holding her legs. But males providing insufficient gifts get flung off by the female before insemination is complete.
During a two-week breeding season, brown antechinus, mouse-like marsupials, begin a mating frenzy. In this promiscuous society, females mate with several partners, each copulation lasting from 5 to 14 hours, before producing offspring. Turns out, by sleeping around, the female increases the chances of her eggs being fertilized by a healthy father and in turn producing fit offspring. After such exhausting sex, before the babies are born, the male antechinus drop dead.