Nitpick: the technical term here would be "sex", not "gender". "Gender" seems to be used as an animal's social-sexual identity, whereas "sex" is an animal's act

Nitpick: the technical term here would be "sex", not "gender". "Gender" seems to be used as an animal's social-sexual identity, whereas "sex" is an animal's actual biological reproductive sex. The word "gender" was originally linguistic, for example it was used to refer to the gender of spanish nouns. The use of "gender" to describe one's social-sexual role was popularized by the feminist movement in the 70s, who believed that social distinctions based on sex are largely arbitrary. Anyways, gender is a fairly modern term and it certainly doesn't refer to the sex of an animal. Although, for most animals I would guess that their gender and sex are the same, unless sexual camouflage is used in that species as a reproductive strategy. Humans are unique in divorcing sex (and gender) from reproduction.