Why does the bowed fiddler crab have such a gigantic pincer?

European Fiddler Crabs | National Geographic

The Fiddler Crab: One Part Giant Claw, Two Parts Attitude

The fiddler crab has a pair of chelae of different sizes. The major chela looks like a violin, while the minor one always rubs against the major. It seems to be playing the violin, but in fact, it is clearing the mud or other things from the major chela. #AnimalAdventure For more: https://english.cctv.com/ | CCTV