Weird Nature 13 Facts Most People Don't Know About The Coconut Crab, The Biggest Arthropod  

Jen Jeffers
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Although most people don't think about crabs as bone crushing, kitten-eating, mastadons of the tropics, most people have never met this terrestrial hermit crab. About the size of a small dog, the coconut crab - otherwise known as the robber crab or palm thief - is the biggest arthropod in the world, often weighing up to nine pounds. These nightmare crabs look more like an alien from outer space than a species of Earth, and their look isn't the only crazy thing about them.

There are plenty of creepy coconut crab facts. These guys can use their four-foot long legs to scuttle quickly from place to place; burrow into dark holes in the ground; and even climb soaring coconut trees. Sometimes known to take down a small mammal, the coconut crab is a true marvel of nature and one that continues to frighten and titillate anyone nearby. But while some believe they are harmless beach combers, others have suspected them of much greater crimes. If you love crabs that are scary, look no further than the coconut crab.

Darwin Called Them "Monstrous"


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Life is good for the coconut crab. Found on tropical islands around the Indian Ocean and parts of the Pacific, these terrestrial critters can live anywhere from 30 to 60 years. Their days consists of napping in shady corners, looking for shiny object, and of course, finding coconuts to eat, which is their favorite food. They are the world's largest arthropods, a phylum of joint-legged creatures that also includes spiders, crustaceans, and other insects. Although the Japanese spider crab is technically larger, it lives underwater where it's weight is supported. 

Apparently their overall size and strength of the coconut crab is so stunning, even Charles Darwin doubted the stories of the locals while visiting the Keeling Islands off the coast of Sumatra in 1836. He believed the natives were playing a trick on him until he finally glimpsed one for himself. Although their shell color can vary, they typically range from orangish-red to purplish-blue. 

They Have A Lot Of Powerful Legs And Can Lift Up To 60 Pounds


They Have A Lot Of Powerful Le... is listed (or ranked) 2 on the list 13 Facts Most People Don't Know About The Coconut Crab, The Biggest Arthropod
Photo: Drew Avery/via Wikimedia Commons

Like all other crustaceans of its class, the body of a coconut crab is divided into different parts. The front section, called the cephalothorax, has 10 legs and an abdomen. The two front legs have powerful claws, followed by two pairs of strong walking legs with pointed tips. This combination allows them to adeptly climb vertical surfaces, including trees. The fourth pair of smaller legs have tweezer-like claws for more precise actions like mating, tending to eggs, or making a nest. As for their large front claws, they are capable of listing vegetation or rocks weighing up to 60 pounds.

They Can Eat Cats, Chickens, Birds, And Sometimes They Auto-Cannibalize


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Despite its intimidating size, the robber crab is more of an opportunist than a predator. While it has been known to eat more sizable delicacies like chickens, kittens, and carrion birds, it tends to scavenge only what has been left behind. In 2017, people caught the coconut crab attacking a live bird for the first time

The coconut crab is also one of the few creatures who self-cannibalize by eating others like themselves as well as their very own exoskeleton once it is sloughed off in the molting process. Experts believe this practice provides a great deal of calcium for creatures' astounding growth. They also believe the coconut crab has only recently, through the evolutionary process, developed the ability to crack coconuts, a practice which allows them to eat less of their own kind. 

Did They Eat Amelia Earhart?


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There is a certain mystique about the coconut crab, mostly because of its extreme size and strength. Because of this, the creature has a certain mythical lore about it. One such example is the theory it is somehow linked to the historical disappearance of Amelia Earhart, who fell off the radar while flying her plane over the Pacific Ocean in 1937. Just three years later, researchers discovered a piece of bone on an island in the area which seemed to match the location and condition of those belonging to the missing pilot. A theory soon emerged she had likely perished somewhere on this stretch of beach, possibly through an encounter with the frightening coconut crab. One hypothesis asserts she may have overwhelmed by the creatures as she lay unconscious and never able to recover.

To test this idea, researchers carried out an experiment using small pig carcasses. When they left the remains in the open, the crabs quickly picked them apart and scattered them around, similar to the way the alleged bones of Earhart were found. Although there is no way to be sure, it's entirely possible either her body or that of another stranded soul found its way into the claws of the robber crab, never to be seen again. One thing is for sure, however - coconut crabs love to feast on bones, pick them clean, and scuttle them away to their nests.