It was crabnapping for a just cause. But the crustaceans that found themselves suddenly plucked from their burrows, stuffed into opaque sacks, and carried off through the forest couldn't know that. When the scientists freed their captives, they waited to see whether the crabs would find their way home or be stranded forever. They'd be watching—from space.
The best way to find out exactly where and how far an animal travels is to tag it with a GPS tracker. But if you're interested in invertebrates, most of your subjects are too small or squishable to carry around such a device. Enter (scuttling in from stage left) the robber crab, Birgus latro. Also called the coconut crab because of its predilection for cracking open coconuts, the species is the largest arthropod on land. Legs included, it can grow to nearly a meter across.
Robber crabs live on islands in the Indian ...
