If you've ever witnessed an overly aggressive guy get bounced from a bar, you probably found yourself internally judging him. But new research published in the journal Animal Behaviour suggests that the opposite may be true for spiders: the more aggressive a male jumping spider is, the sexier his female counterparts find him.
Researchers from the National University of Singapore quantified female spiders' preferences for aggressive males. They first placed males in a small chamber containing a mirror and observed how combative they were toward their own reflection. Once males had demonstrated either their contempt for or passivity towards their own reflections, they were paired with another male for a series of bouts. Using the results from the mirror test and combat trials, the researchers assigned each individual male spider an aggression predictability score. Finally, a pair of one highly aggressive male and one more passive male were placed in a chamber with a single female spider. Female preference was determined based on the amount of time she spent ogling each of her potential suitors.
The researchers found that aggressive males are both more likely to defeat a rival in a combat trial, and to draw a higher amount of attention from females than their more pacifist competitors. They concluded that, not only is this evidence for sexual selection, but that the combination of strong competitiveness and female favor reinforce each other to push the most aggressive spiders to the top of the pile.