It's a ram's world on St Kilda. Human farmers abandoned this group of small islands 160 kilometres off the coast of Scotland in 1930. Emancipated from their two-legged oppressors, the sheep have given free reign to free love. During their two-day period of receptivity, females have been known to mate with seven different males. Males can copulate up to 13 times a day.
Rams fight ferociously for females.
Most male skeletons have fractured neck vertebrae, sustained while butting other males. Not surprisingly, larger males with bigger horns mate more frequently. But rampant promiscuity is also a recipe for a more subtle contest. If a female mates with more than one male in a short period of time, the different sperm compete to fertilize her eggs. Three-quarters of Soay sheep twins have different fathers.