Samoan Coconut Crab (Ūū).

Photo of a Samoan land crab (ūū).

Our best known land crab is the large and edible coconut crab (Birgus latro), which weighs 4-7 pounds and has a leg span up to about 30 inches. It has developed a special lung-like organ of spongy tissue that enables it to breath air. This crab leads a fully terrestrial existence except when it comes time to lay its eggs in the ocean. The eggs hatch into larvae that drift in the ocean for about a month before migrating shoreward. The youngest coconut crabs use a snail shell for protection during this early period but then abandon this practice for the remainder of their long life (up to 40 years).

They are nocturnal scavengers that eat coconuts, fruit, dead animals, and other organic material. There is some uncertainty about the crab’s ability to husk and eat coconuts; some observers believe that the crabs are able to do so only if a coconut was damaged when it fell from the tree.

Coconut crabs are easily caught, so few are found in areas where people live. Another liability for these crabs must be trying to cross our island roads, both when small coconut crabs migrate inland from the sea, and again when large mature female crabs crawl back to sea to release their eggs. During new moon nights in summer months, squashed crab road-kills are evidence of an untimely end to their journey.