Coconut crabs and their colossal claws

Our planet is home to diverse life forms—some that we swoon over and some that freak us out. Coconut crabs, with their legs spanning a metre wide and extremely powerful claws, are of the latter kind. Unlike most crabs that spend their lives crawling the seafloor or a river bed, these crabs, although born in the sea, are terrestrial and live all of their adult life on land. They roam the coastal forests on tropical islands in the Indian and Pacific oceans, including parts of the Andaman and Nicobar Islands, nesting inside rock crevices. The coconut crab is the biggest land-dwelling arthropod—a family of invertebrates that includes insects, spiders and crustaceans.

A fully grown adult coconut crab weighs about four kilograms. Its prowess as a robber is largely thanks to its incredible claws, which can pinch with force thrice as heavy as a human bite, and can lift objects as heavy as 30 kilograms! As the name suggests, these crabs devour coconuts—climbing the tall tree with their gripping claws and cracking the green coconut shell for the creamy flesh inside.

But their love for food does not stop with coconuts: they gobble up nuts, fleshy fruits and seeds, and feast on small mammals like rats and large sea birds. They are fierce cannibals too—eating up their own kind. Hence, the crustacean is also called ‘robber crabs’ or ‘palm thief’. Some speculate that these crabs may be behind the disappearance of Amelia Erhart, the first female aviator to fly across the Atlantic Ocean, who mysteriously disappeared without a trace from one of the Pacific islands.

In recent years, development along the coasts of islands where coconut crabs live is destroying their habitats. The spread of agriculture plays a part in this damage. People also hunt crabs in the thousands and consume them as a local delicacy and exotic food. As a result, large crabs are becoming rare or going locally extinct on some islands. If these threats continue, their long life of about 60 years may not help them survive in the future.

- Spoorthy Raman