Hermit crabs are the renters of the crustacean world, making their homes in discarded shells of other sea creatures. But with high demand for shell real estate, hermit crabs often forcibly evict other crabs to seize a better-fitting shell.
During these battles, attackers repeatedly “rap” their shells against defenders, and those who rap most vigorously are more likely to win. But, just as the outcome of a boxing match depends not only on how many punches a boxer lands, but also on the skillful placement of these blows — researchers wondered if skill helps crabs win shell skirmishes.
To prompt conflicts between crab pairs, scientists from the University of Plymouth gave one crab (the attacker) an ill-fitting shell, whereas the other (the defender) received a perfect fitting one. that attackers who rapped on a particular area of the defender’s shell — the “sweet spot” — were more likely to win fights than those who rapped elsewhere.
To be evicted from their homes, losing crabs first have to release muscles that grasp onto their shells. The sweet spot suggests that attackers must accurately strike a specific anchor point to dislodge their opponent’s grasp, and victorious crabs may skillfully target this spot.
High-volume attacker rapping may also lead defenders to flee their shells. The team found that the number of raps was linked with proportion of raps to the sweet spot. This could mean that rapping in the sweet spot allows attackers to perform more raps (perhaps due to a better grasp of their opponent) or that accurate crabs also rap the most vigorously.
In the animal kingdom, winners of battles over mates, food, and territory are often the biggest, strongest, and most . But as — and hermit crabs — show us, there’s more to winning fights than brute strength. Skill is important because it allows fighters to strike with greater accuracy and conserve energy. Spatial skills may give hermit crabs a competitive edge in shell real estate wars, and similar abilities could help other animals win conflicts too.