Trond Amundsen

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ScienceShot: Turning the Tables on the Mating Game

Courtship in many animals plays out like an episode of The Bachelorette: Competing males woo, and picky females choose. But like a reality show plot twist, a shortage of males can spur females to compete for mates. That's what researchers have observed in the mating behavior of the two-spotted goby (Gobiusculus flavescens) in kelp forests along the Scandinavian coastline. The fish live for only 1 year, but they can mate multiple times during their breeding season from April to July. Mating-ready males become scarce over this time period, possibly from predation or from defending clutches of already fertilized eggs. As male densities dwindled, the fish completely reversed their conventional mating roles, the researchers report in the current issue of The American Naturalist. By July, once-choosy females switched to actively enticing males by flashing their bright orange bellies, swelling with ripe eggs ready to be fertilized (shown above). Unlike earlier in the season, multiple females often vied against each other for a single male's attention, and males became much more likely to break off a courtship than females. This first analysis of mating behavior in a species with shifting courtship roles demonstrates that males can turn picky, and females faced with poor partner options might buck convention and lower their standards.

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