Seabirds apparently have a surprising new predator to worry about. A researcher who worked on the Chagos Islands in the Indian Ocean in 2016 says he witnessed a large coconut crab attack a sleeping seabird, which then became dinner. Mark Laidre of Dartmouth College says he first spotted a crab climbing a tree to a low branch where a red-footed booby, which normally weighs about 2 pounds, was napping in its nest. The crab broke the bird's wing, causing it to fall to the ground, then continued attacking it, breaking its other wing, reports New Scientist. At that point, other crabs arrived for dinner, says Laidre, who filmed part of the scene he described as "pretty gruesome."
It was the first time this hunting of a large, vertebrate animal had been observed among coconut crabs, which are the world's largest land-dwelling invertebrates, reaching up to 3 feet wide and weighing up to 9 pounds. The behavior might not seem surprising given the crabs' size—they're often the largest species in the coral atolls they call home, per the Guardian—but Newsweek explains they were previously thought only to be scavengers with a particular taste for, as their name suggests, coconuts. Though it's possible the seabird was a one-time meal, Laidre—who says he's discovered that birds and coconut crabs rarely inhabit the same islands—suspects the crabs play a more dominant role in their ecosystem than previously known.