Caught on Camera: Tree-Climbing South Seas Crab Kills, Eats Bird

SAN FRANCISCO (CBS SF) -- Not very much has been learned about coconut crabs since Charles Darwin first described how these fearfully powerful crustaceans can crack open the fruit of the palm tree for which they're named.

Coconut crabs are the largest land-living arthropods in the world and an adult can measure three feet across with legs extended and weigh up to nine pounds. They live underground and climb trees. They have a keen sense of smell but will drown if submerged underwater for long.

In addition to coconuts (which aren't a major part of their diet), these omnivorous creatures are known to eat carrion. There's even speculation that they may account for the never-found body and bones of famed American aviatrix Amelia Earhart.

There have been stories that coconut crabs hunt and eat birds but scientists had not verified those rumors.

Then, on a 2016 expedition to islands in the Indian Ocean, Mark Laidre, a Dartmouth researcher and National Geographic explorer, observed and photographed a coconut crab stalk and kill an adult red-footed booby, pulling it down off a low-lying tree branch, snapping its wing and then stabbing and crushing the helpless bird while other crabs -- drawn by the smell of blood -- gathered to share in and compete for the pickings.

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