Giant Spider Crab Aggregation

Between May - July ever year hundreds of thousands of Giant Spider crabs congregate on the sandy shallows off Melbourne Australia. Their legs are over 70cm long with a body measuring nearly 17cm wide. They seek shelter to moult and ,in some cases, mate. They shed their shells in order to grow a new bigger one. Once one crab starts to moult it sets off a chain reaction and the rest of the orange-clad army moult almost simultaneously.

By aggregating and moulting together, the less chance they have of getting eaten, a simple case of safety in numbers.

Via