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Same sex sexual-behavior_rdale1_senior_visual



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  • 1. 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
  • 2. Social Glue• Three species engaging most prevalently in same-sex sexual behaviors are bottlenose dolphins, bonobos, and Japanese macaques.
  • 3. Bottlenose Dolphins• Male calves engage in the highest rates of same-sex encounters• Formation of alliances, from 2-14 individuals• Formation of pair bonds
  • 4. 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
  • 5. 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
  • 6. Intersexual Conflict• Viviparous fish, dung fly, cockroaches
  • 7. Viviparous Goodeid fish• Subordinate males• Sneak copulationsShortly after losing a fight,the subordinate male alreadystarts to show the“pregnancy spot” of thefemales
  • 8. Dung Flies• Mate blocking• Female mate preference
  • 9. Cockroaches• Females mount males• Pseudofemale behavior
  • 10. Prison Effect• When there is an overwhelming majority of one gender in an environment (usually artificial)• Sexual stress• Preserves sexual function• Damselflies, koalas
  • 11. Damselflies• Switches in choice• Rate of male-male mate choice• Male–male mating behavior is common
  • 12. KoalasSolitarySame-sex sexual behavior is not normallyobserved in the wildWhen in an all female environment,engaged in same-sex sexual behaviors
  • 13. Kin Selection• Individuals can gain fitness by providing resources to siblings, thereby increasing their inclusive fitness• Birds
  • 14. Birds• Acorn Woodpeckers• Tasmanian Native Hens and Dusky Moorhens• The kin selection hypothesis is considered unlikely in many cases.
  • 15. Conclusion• Social glue• Intersexual conflict• Kin selection• Prison Effect