Claw size most often determined which crayfish won — if the claws of one crayfish were significantly larger than another's, the other would simply turn and run. "Like most animals, the size of their weapons seemed to determine everything in these crayfish," Wilson said. Pincers reached up to a third of the length of each combatant's body.

However, larger claws were not always the strongest pincers, suggesting these weapons are most often used for intimidation rather than combat. "When the claws of each crayfish are roughly the same size, then whoever's stronger prevails," Wilson said. The team's results are detailed in the August issue of the journal American Naturalist.