Biologist records rare sighting of giant crab hunting, killing bird

By Ray Downs  |  Nov. 12, 2017 at 11:08 PM
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Nov. 12 (UPI) -- A biologist studying the world's largest crabs on a small island in the Indian Ocean caught video of one of them attacking and eating a bird.

Last year, biologist Mark Laidre of Dartmouth College was in the Chagos Archipelago studying coconut crabs, the world's largest terrestrial invertebrate, which can get as big as small dogs. During one observation session, he saw one coconut crab about to kill a red-footed booby, which was a rare sighting. Crabs are known to feed on carcasses, but actually hunting down a live animal was rarely seen.

"Before leaving for Chagos, I wondered what coconut crabs would eat," Laidre wrote in a paper published this month. "I had undertaken studies of foraging in terrestrial hermit crabs for almost a decade, in Costa Rica, the Dominican Republic, and Mexico, and these revealed an omnivorous and often carnivorous diet, one of the most diverse of any crustacean."

Laidre added: "Yet only twice in all those years have I observed predation by terrestrial hermit crabs, in both cases on another invertebrate (hymenopterans that fell on the beach in their final death throes). All other carnivory involved scavenged dead carcasses."

Not only did the coconut crab kill the red-footed booby, but it climbed up a tree to hunt it down.

"The booby had been sleeping on a low-lying branch, less than a meter up the tree. The crab slowly climbed up and grabbed the booby's wing with its claw, breaking the bone and causing the booby to fall to the ground, where it was unable to fly," Laidre wrote. "The crab then approached the bird, grabbing and breaking its other wing. The booby struggled and pecked at the crab, but the crab retained its grip with both claws, kicking at the bird with its ambulatory legs."

Within 20 minutes, five more coconut crabs arrived on the scene, "likely cueing in on the blood with their neurologically acute olfactory sense," Laidre wrote. "As the booby lay paralyzed, the crabs fought, eventually tearing the bird apart over several hours, carrying it away, and consuming it."

Warning: The video below might be disturbing for some viewers

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