Why do some domestic sheep exhibit exclusive homosexual behavior?

Homosexual behavior is common among domestic sheep and wild species in the genus Ovis. Approximately 8% to 10% of domestic rams display an exclusive preference for mating with other males rather than females, making domestic sheep one of the few non-human species known to exhibit exclusive same-sex orientation. Observers note that this male-male sexual preference involves typical courtship acts, mounting, pelvic thrusting, and ejaculation.

What we know

• About 8% to 10% of domestic rams refuse to mate with ewes and readily mate exclusively with other rams. [2, 4]
• Around 18% to 30% of all domestic rams demonstrate at least some homosexual behavior. [2]
• Rams engaging in same-sex mounts perform standard courtship behaviors such as foreleg kicks, vocalizations, and anogenital sniffs prior to mounting. [2]
• Domestic sheep are recognized as the only known non-human animal species to exhibit exclusive homosexual orientation. [2, 4]

Still open

• The exact biological or environmental causes underlying exclusive sexual orientation in non-human animals like sheep remain open to ongoing scientific theory and discussion.

Where to go next

• what caused itWhat causes same-sex sexual behavior in animals?
• the bigger pictureHow common is same-sex behavior across other animal species?
• how we knowWhat evidence indicates that ram homosexual behavior is sexually motivated?
• how it workedHow does prenatal hormone exposure affect animal brain development?
• a case in pointWhat are examples of non-reproductive sexual activities in wildlife?
• an unexpected connectionHow do sheep compare to humans regarding exclusive same-sex orientation?Domestic sheep share with humans the rare distinction of being the only known mammalian species to exhibit exclusive same-sex sexual orientation.

Sources

• [1]Homosexual behavior in sheep (Wikidata Q123431580) · CC0 1.0
• [2]Homosexual behavior in sheep · CC BY-SA 4.0
• [3]Homosexuality · CC BY-SA 4.0
• [4]Homosexual behavior in animals · CC BY-SA 4.0
• [5]Non-reproductive sexual behavior in animals · CC BY-SA 4.0