Male fiddler crabs (Uca lactea) do epic battle with their massive claws, grappling with their opponents and sometimes tossing them into the air. But crabs whose fighting limbs have been torn off regrow hollow claws: fakes that look like the original solid pincers, but don’t hold up nearly as well in an actual fight. And new research shows they’ve developed a few cheap tactics to compensate. These hollow-clawed crustaceans tend to pick on smaller crabs, possibly in an effort to intimidate their rivals into backing down before a fight becomes too violent—and their hollow claws are exposed for the fragile weapons they are. In 138 crab battles, those with a hollow-clawed male were only about 1/8 as likely to progress to the “fling” stage—the most violent kind of fight—as those between two crabs with their original claws, according to a paper published yesterday in Behavioral Ecology and Sociobiology. But males with solid claws are wise to the cheaters’ tricks. In many of the observed fights, these males didn’t back down even against crabs with substantially larger weapons—and when those goliaths were wielding hollow claws, they ended up retreating almost half the time.