Crabs wave or drum their pincers as a form of communication, they tend to be aggressive towards each other; in particular the males fighting for the right to mate, or for a secure nook in a rocky coast where caves are limited. However, crabs are occasionally observed working together as families to find food.

CRAB
/krab/ a crustacean, found chiefly on seashores, with a broad carapace, stalked eyes,...