There may be nothing unnatural in nature, but nature still encompasses much that seems fantastically strange--the amazingly multifarious sex lives of animals, for example. Sexus Animalis tells us everything we never dreamed we wanted to know about the reproductive systems, genital organs, and sexual practices of animals, from elephants (who masturbate with their trunks) to fruit flies (who produce spermatozoa twenty times their size). In the animal kingdom we find heterosexual, lesbian, gay, and bisexual behavior, as well as monogamy, polygamy, and polyandry, not to mention fellatio and many varieties of erections and orgasms.

Emmanuelle Pouydebat, a natural history researcher, tells us about gutter penises, double penises, detachable penises, and corkscrew-shaped penises, as well as vaginas built for storage and clitorises with thorns. (Perhaps unsurprisingly, there's more data about animal penises than animal vaginas and clitorises.) She explains how the ostrich achieves an erection, describes the courtship of pygmy chameleons, and recounts how the female short-beaked echidna chooses a partner. She reports on sexual assault among animals--there's evidence that half of female mallards are sexually assaulted--and explains how masturbation helps squirrels avoid sexually transmitted diseases. It seems that animals have been composing their own Kama Sutra throughout the ages. Striking color illustrations accompany the text.