So Won't You Be My Neighbor

December 1, 2011

Eva Gusnowski

The fiddler crab doesn’t wear a cardigan, but he wants to be your neighbor. That is, if you happen to be another male fiddler crab with certain “qualifying” features.


Male fiddler crabs will defend the lair of a neighboring male crab against intruders. “How lovely” you might say, “they are friends!” But in reality, not so much. Male crabs only defend their neighbor’s homes if the neighbor has a smaller claw than they do. This may sound odd, but it serves a very selective purpose.

The female fiddler crab likes her men to have a good solid wave: high in expression, vigorous, and with a large claw to be exact. This has been shown to be true using robotic claws with varying states of waving. But don’t worry, no Inspector Gadgets were harmed in these experiments.


What the researchers also found was that males were chosen relative to their neighbors. Female crabs seemed to prefer males with a large claw when they were able to compare this male to a neighbor with a comparatively small claw. The ability to compare claw sizes and waves is thought to allow the females to realistically choose the “best” mate out of the bunch…the best mate having, of course, the largest claw.


So all in all, the male fiddler crab doesn’t have an altruistic attitude towards his neighbors. He keeps you around because his claw is bigger than your claw. He doesn’t want to be your friend, and he doesn’t want to play puppets or trains with you.

It’s a wonderful day in the neighborhood.



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