A full-grown coconut crab can weigh up to 4 kilograms and measure nearly a metre from one claw tip to the other. Their shells are usually deep blue-purple or orange-red and they look quite extraordinary - like something from a fantasy story. Despite their name, they eat many things: fruit, seeds, nuts, and occasionally other crabs.
Their claws can apply more force than almost any other animal on Earth for their size. Scientists have measured it and found that the grip of a large coconut crab is stronger than the bite force of a lion, gram for gram. They use this strength to pull apart tough husks, pry up rocks and climb trees.
Coconut crabs are brilliant climbers. They can scale smooth palm tree trunks, going up to the fronds at the top where coconuts grow. They sometimes drop coconuts from the tree to crack them open on the ground, then climb back down to eat. They have been spotted 6 metres up in trees.
They are most active at night and spend the day resting in burrows or rock crevices. Despite being crabs, they actually breathe air - they cannot survive underwater. They begin their lives as tiny larvae in the sea, but once they grow up they live on land permanently.