Soay ram on the island of Hirta, St Kilda. Image by Arpat Ozgul As the old adage goes, too much of a good thing... is an even better thing. At least, that's what a lot of animals seem to think---males often evolve elaborate ornaments to impress females, the crazier the better. But in some cases the theory doesn't hold up---for instance, in the Scottish Soay sheep. Males with bigger horns are more able to woo the lady sheep and fend off competitors. But why, then, are there still small-horned males around? Researchers finally think they know the answer to this head-scratcher, and may thus have a clue to how such sexual selection works in other animals too.
For the last two decades, researchers have been studying a population of 1,750 Soay sheep (Ovis aries) on an island off the coast of Scotland. Each year they tracked three things: reproductive success ...
