Here's why they do this:
* Defense Mechanism: When a predator grabs the claw, the crab can quickly detach it, distracting the predator and giving itself a chance to escape. The severed claw continues to twitch, further drawing the predator's attention away from the crab.
* Regeneration: The lost claw will regrow, though it may take some time (several weeks or months) and the new claw may be smaller than the original.
* Energy Conservation: Autotomy allows the crab to conserve energy by sacrificing a limb rather than expending energy in a futile struggle against a stronger predator.
It's important to note: While fiddler crabs can lose their claws, they don't do it frequently. It's a last resort defensive tactic, not a common occurrence.