Same-sex Sexual Behavior in Animals• Adaptive Hypotheses: – Social glue – Intersexual Conflict – Kin Selection – Practice for Reproduction – Overdominance• Non-Adaptive Hypotheses: – Prison Effect – Mistaken Identity
Social Glue• Three species engaging most prevalently in same-sex sexual behaviors are bottlenose dolphins, bonobos, and Japanese macaques.
Bottlenose Dolphins• Male calves engage in the highest rates of same-sex encounters• Formation of alliances, from 2-14 individuals• Formation of pair bonds
Bonobos• 40-50% of sexual encounters in bonobos are same-sex encounters.• Most of these are in females, which are dominant to males.• Bonobos are very peaceful• Pair bonds are often formed
Japanese Macaques• Same-sex sexual activity accounts for 30% of all sexual behavior.• Often, after female-female mating, the dominant female would attack the subordinate female• Females mated irrespective of ranking; mating for alliances was unlikely• This behavior is thought to be sexual in macaques