premise: The terrestrial coconut crab is the world largest living land arthropod. The coconut crab is a true crab, weighing up to 4kg, with a leg span of more than 3 feet. The coconut crab is a typical example of island gigantism, increasing in size due to the lack of predators on islands home to coconut crabs.
hypothesis: Attacks from predators have led to the increased size of the coconut crab.