Science Blast: Giant Bird-Eating Crab!

Giant crab eats birds. You’re next!

Humongous land crab dines on remote-island seabirds

 Their attacks may influence where certain birds can survive in one Indian Ocean archipelago SARAH ZIELINSKI DEC 12, 2017 — 6:45 AM EST
 coconut crab
Coconut crabs, the world’s largest invertebrate found on land, have been caught attacking seabirds on remote islands in the Indian Ocean. JANOS/ISTOCKPHOTO

A biologist working on remote islands in the Indian Ocean has witnessed something new. He spotted a coconut crab, the world’s largest land invertebrate, killing and eating a seabird known as a red-footed booby. It’s the first time that such attacks have been reported.

Mark Laidre is a biologist at Dartmouth College in Hanover, N.H. He witnessed the attack in March 2016. He was on a two-month field expedition to study the crabs in the Chagos Archipelago.

Laidre is an expert on hermit crabs. But he had been “dying to study” their humongous cousins, which can have a leg span wider than a meter (three feet) and can weigh more than four kilograms (nine pounds). Little is known about the crabs, he notes. A study earlier this year looked at the force that a coconut crab’s claw can exert in the lab. But, he says, “there’s still not a single paper on how they open a coconut.”

So he trekked to a remote spot in the Indian Ocean. (He wanted to study the crabs in a place where few people were around to interfere with their natural behaviors.) Laidre had heard tales of coconut crabs killing rats. He later witnessed the crabs munching on the islands’ rodents. “Clearly,” he says, “it’s in their repertoire to eat something big.” And when he took inventory of the crabs’ burrows, he found one held the carcass of an almost full-grown red-footed booby. “At the time,” he recalls, “I had assumed it was something that had died … and the crab had dragged in there.”

Then, in the middle of one night, he saw a crab attack a sleeping bird. The crab scaled a tree and then dragged the bird off of a branch and onto the ground. There, it broke the bird’s bones. Laidre managed to catch part of the event on film. “I didn’t have the heart to videotape five coconut crabs tearing apart the bird later,” he says. “It was a little bit overwhelming. I had trouble sleeping that night.”

Read more…