From an evolutionary and biological perspective, animals are driven to have sex in order to procreate. But there is a lot more to sexual relations between animals. Animal sex is at least as strange and varied as human sex. A male might copulate with many females. And female animals of many species can be choosy, too. Homosexuality is common. Monogamy is rare. And the animal kingdom is full of swingers. In short, with animals, sex can be wild.
Spider sex just got a little more interesting. Researchers now find that the spider equivalent of the penis isn't numb like once believed; it's filled with nerves that might help the spider ensure fertilization.
With the bill and webbed toes of a duck, tail of a beaver and body of an otter, platypuses are some of the strangest-looking animals on the planet. Their mating behaviors are just as odd, involving venom battles, tail biting and aquatic dances.
In calm waters, barnacle penises are long and slender, allowing them to reach the maximum amount of partners possible. But wave-exposed, intertidal locales favor stouter penises, which are more easily controlled under turbulent conditions.