A brilliant and important exercise in exposing the limitations of received opinion, this book presents to the lay reader and specialist alike an exhaustively argued case that animals have multiple shades of sexual orientation.

The book is broken into two sections, the second containing species "portraits" detailing recorded homosexual/transgendered behaviors. The main portion of the book sets out to reveal and, indeed, revel in the documented evidence to date that some 450 species engage in both sustained and occasional "gay," "lesbian" and transgendered pairing, parenting and play. Animals (both heterosexual and homosexual) also rape and divorce, commit "child" abuse and infidelity and can be lifelong celibates.

Human claims to uniqueness in this arena are shown to be increasingly difficult to maintain. The overall effect is to detonate the myth that animals are solely driven by heterosexual reproductive urges, as Bagemihl, a biologist, amasses evidence with case study after case study of species ranging from whiptail lizards to bottlenose dolphins, flamingoes, vampire bats and giraffes.

But his book offers more than a zoological laundry list. Biologists who have long classified these behaviors as taking place only in "abnormal" conditions or as "pseudo-copulation," "mistakes," "practicing" and domineering sexual bullying are frequently shown to be willfully ignoring behavior that does not reflect their own worldview or accepted scientific thought.

What might so easily have turned into a tub-thumping activist tract hitched to the need for acceptance of homosexuality among humans is instead elevated to a hugely inclusive, celebratory biological interpretation of the world. Bagemihl convincingly overturns previous inviolable "truths" that scarcity and functionality are the prime agents of biological change, and advances instead the idea that abundance and extravagance ("biological exuberance") are just as crucial to the mosaic of life. Numerous illustrations by John Megahan.