Like tiny acorns turning into giant oaks, the coconut crab – the world’s largest land-living arthropod – has a humble start to life.
It begins as microscopic larvae, drifting through the tropical Indian and Pacific Oceans in vast swarms of plankton for several weeks, before sinking to the seafloor. There, it finds a temporary shell to wear, before heading towards dry land (Christmas Island in the Indian Ocean is a favourite haunt).
The crabs reach sexual maturity after five years, but it takes 40 to 60 years for them to reach their maximum size, weighing more than four kilograms and measuring a gargantuan one metre across.
To survive its terrestrial life, the coconut crab has evolved a lung-like organ which allows it to pull oxygen directly from the air. It’s an adept climber, and its claws are highly muscled, allowing it to crack open the coconuts on which it occasionally feeds. It’s even able to wiggle its antennae like an insect in order to track windborne smells. In fact, the adult coconut crab is so well adapted for life on land that it can drown if trapped underwater.
Rotting fruits are a favourite food source for the coconut crab, but it also consumes carrion and can even take on large prey, including rats and turtle hatchlings. Terrifyingly, larger individuals have been witnessed raiding bins.