Scientists have observed homosexuality in over 450 species of the animal world since Antiquity. Once little known to the general public and considered an anomaly, even an aberration, by researchers, it was saddled with prejudices derived from prevailing ideologies. Fleur Daugey sweeps away preconceived notions by showing that many behaviors observed in heterosexual animal couples are also engaged in by animals of the same sex, with their own specificities and refinements.