New research shows how external genitals arose from very different starting places for reptiles and mammals.
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.
Koalas may be cute and cuddly, sleeping 18 to 22 hours a day, but they can become vicious when it's time to get down to business. Here's a look at how the marsupials mate.
We humans use the euphemism for sex that “we like to get a leg over” but the first jawed vertebrates – the placoderms – they liked to get a leg in.
Jellyfish mating involves courtship dances, swamps of reproductive material and buds, or tiny clonal outgrowths.
Despite some human-like characteristics, elephants' mating behaviors are very different from our own.
Females with penislike genitals and males with vaginalike organs are cases of a new extreme reversal of sex roles researchers have discovered in little-known cave insects.
The reason why pandas are going extinct is nothing to do with their cycles. It is because so much of their natural environment has been destroyed.
From small and subtle to large and in charge, sex in the animal kingdom is just as varied as the beasts themselves.
Bat sex involves unique behaviors not seen in other mammals, including swarming, honking and oral sex.
Peafowl sex is a sight to behold, involving brilliant train displays, rattles and hoot dashes. Once the peacock and peahen have mated, they go their separate ways.