Author: Yao-Hua Law / Source: Science News for Students
The death of a land-dwelling hermit crab always draws a crowd. Researchers working in Costa Rica now know why. They found that curious crabs are drawn to the smell of flesh torn from one of their own.
Hermit crabs live inside shells — homes that they carry around wherever they go. None of the roughly 850 known species of hermit crabs can grow their own shells. Instead, the crabs occupy shells originally left behind by dead snails. A hermit crab grows to the size of its shell. To grow beyond that size, the creature must track down a larger shell and move in. So as its home begins to feel crowded, a hermit crab has to somehow find an empty shell. It could be one vacated by a larger crab. Or it could be a shell left behind by a crab that recently died.
Mark Laidre is a biologist at Dartmouth College in Hanover, N.H. Leah Valdes was a student at the college. These two set up an experiment on a beach in Costa Rica. They set out 20 plastic tubes, each holding bits of hermit-crab flesh. Within five minutes, almost 50 hermit crabs (Coenobita compressus) swarmed each sample. “It’s almost like they were celebrating a funeral,” Laidre says.
In fact, the reality is more gruesome. That scent of flesh signaled that a fellow land hermit crab had been eaten. That also signaled there should be an empty shell for the taking, Laidre explains. The swarming crabs, he notes, “are all in an incredible frenzy…
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