Twice a day the tide comes in and the beach becomes the domain of the navy - fleets of blue swimming crabs. With legs like paddles they are equipped with underwater breathing apparatus and they can hide in the mud using periscope eyes to spy out oncoming enemies. But when the sea retreats, so must they. The shoreline is held by Fiddler crabs, plucky little gladiators with weapons half their body size. They are the most recent invaders from the sea and although they can survive on land, they still need water to breathe. Their solution is burrows that double as wells, allowing them the vital water they need.
Further inland the hermit crabs have taken up arms. Their secret is stolen shells that give them a portable source of water. But a good shell is hard to find, causing much infighting within the battalion. Crabs must get past attack from aerial predators. Bring on the soldier crabs. Their vast battalions stage repeated infantry invasions. Their army issue breathing apparatus is adapted for land. The crabs also have elite forces. Ghost crabs slip silently under the sand, poised to launch a terrifying ambush if prey wanders past. They are the fastest crabs of all and can reach an amazing three metres a second. Yet even these fierce warriors are must breed at sea. It's time to send in the special forces. The Marsupial crab has formed an elite corps, independent from the supply lines to the sea. It can survive deep in the Australian desert, thanks to one amazing physiological adaptation - its young are reared in a pouch. Could this be the future of crabs? And where will the next invasion occur?
