Coconut crabs are related to hermit crabs, and young ones do carry small shells on their backs. But as they grow, they outgrow all available shells and their tail hardens into a thick protective plate instead. An adult coconut crab can weigh up to four kilograms and measure nearly a metre from claw to claw tip.
These crabs are impressive climbers. They use their sharp claws to grip palm trunks and can climb several metres up to reach coconuts. Once at the top, they may cut the coconut free or carry pieces down to eat on the ground. Their claws can apply a gripping force stronger than most animals of similar size.
Coconut crabs are mostly active at night, which is why many islanders rarely see them during the day. They shelter in burrows or rocky crevices and emerge after dark to forage for food. As well as coconuts, they eat fallen fruit, seeds and occasionally other small animals.
In the Marshall Islands, coconut crabs have long been part of island life. They are known to be shy creatures that will try to hide when people approach. Because they grow so slowly – a coconut crab can live for 40 years or more – communities take care to look after their populations.