Why sea slugs put up with penis spines and syringe-like appendages.
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.
Even if devoured by their mate, a spider's genitals break off and keep pumping to up the dead spider's odds of being a daddy.
From transvestite birds to zombie caterpillars and our own set of animal superheroes, it's been a wacky ride.