Coconut Crab

Birgus latro — the coconut crab — is the LARGEST LAND-LIVING ARTHROPOD on Earth and one of the most extraordinary terrestrial crustaceans alive today. The species is widespread across tropical Indo-Pacific islands — Christmas Island (Australia), Cocos Islands, the Seychelles, Mauritius, Zanzibar, Madagascar, the Philippines, Indonesia, Papua New Guinea, the Solomons, French Polynesia, the Cook Islands, and many other Pacific atolls. Adults reach 4 kg body weight (roughly the size of a small house cat), with leg spans exceeding 1 METER. The species is a TERRESTRIAL HERMIT CRAB DESCENDANT — coconut crabs evolved from hermit-crab ancestors and the juveniles still carry shells like typical hermit crabs, but adults LOSE THE NEED FOR PROTECTIVE SHELLS as they grow larger and instead develop a thick HARDENED ABDOMINAL CARAPACE that provides intrinsic protection. The species' chela (front claws) develop EXCEPTIONAL GRIP STRENGTH as adults — measurements of large adults show grip strengths of UP TO 3,300 NEWTONS (over 740 pounds-force) — the strongest pinch strength of any animal except some sharks and crocodiles, and far exceeding human bite strength (~1,300 N) and human grip strength (~600 N). The chela are powerful enough to crack OPEN COCONUTS — the species' most famous behavior. Coconut crabs CLIMB COCONUT PALMS (using the strong walking legs to grip the palm trunk) to harvest unripe coconuts directly from the tree, drop them to the ground, and then descend to consume them. To open the harvested coconuts, the crab either: (1) HAMMERS THE COCONUT REPEATEDLY AGAINST ROCKS until the husk cracks (a behavior that requires hours of methodical work), or (2) GRADUALLY PEELS AWAY THE HUSK using the chela over 8-10 hours of methodical work, exposing the inner coconut for consumption. Adults are nocturnal, terrestrial omnivores feeding on coconuts (the most cited food source), other tropical fruits, plant material, smaller arthropods, and carrion (including documented predation on small birds, rats, and other small vertebrates). The species is famously cited as a possible perpetrator of the disappearance of pilot Amelia Earhart in 1937 — coconut crabs on Nikumaroro Island (where Earhart's plane is suspected to have crashed) may have scavenged her remains, complicating archaeological searches for evidence. Females must return to the OCEAN to release eggs (the larvae are marine and develop through several planktonic stages before settling on land as juveniles) — making the species a flagship example of an animal lineage that has transitioned from marine to terrestrial life while retaining a mandatory marine larval phase. The species is harmless to humans unless deliberately handled (a defensive pinch from a large coconut crab can cause serious finger injury) and is one of the most-photographed and most-Googled crustaceans in tropical natural history.