Nikumaroro Island, KiribatiThe coconut crabs on the island of Nikumaroro are longer than a reporter’s notebook, wider than an archaeologist’s trowel, and roughly the same size as an explorer’s hiking boot. As the largest land invertebrate on the planet, coconut crabs can measure up to three feet across and clock in at over nine pounds. In short, they are too big.

Members of the National Geographic-sponsored expedition currently searching the island for traces of Amelia Earhart know to keep a wary eye out for the enormous crustaceans—their claws exert more force than most animals' bite.

During the day, when the scientists do most of their work on the Pacific atoll, the crabs are easily avoided. Those that emerge from their burrows into