Robot crab reveals how male crabs compete to attract female mates

A study conducted by researchers at the University of Exeter’s Centre for Research in Animal Behaviour (CRAB) used a robotic crab named Wavy Dave to investigate how male fiddler crabs compete for female mates. Male fiddler crabs attract females by waving their one oversized claw outside their burrows, a key sexual signal. The robotic crab, equipped with a 3D-printed body and waving claw, was placed near real male crabs in southern Portugal to observe their reactions to a mechanical rival. The study found that male crabs increased their claw-waving duration and were less likely to retreat when the robot waved, especially when it had a smaller claw, indicating that males adjust their signaling behavior dynamically in response to competition. The research also revealed that male crabs were less likely to challenge rivals with larger claws, likely due to fear of losing or injury. Some males even physically attacked the robotic crab, with one crab pulling off Wavy Dave’s claw and ending the trial. These behaviors suggest