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Coconut Crabs Exert More Force When Pinching than Most Other Animals

Stephanie Wolek
24th November, 2016

A team of scientists recently measured the claw strength of the coconut crab. They found that the crabs were the strongest crustaceans on the planet. The findings are in a paper that was just published in the journal PLOS ONE. Coconut crabs (Birgus latro) are the largest terrestrial arthropods in the world, a group that includes insects, arachnids, and crustaceans. As their name suggests, coconut crabs use their use claws to break open coconuts, a favorite source of food. They are opportunistic, however, and will also feed on other fruits, seeds, decaying carcasses, smaller crabs, and basically anything else they can find. Coconut crabs are a type of hermit crab and juveniles must find discarded shells to live in. Once the crabs reach adulthood, their exoskeleton hardens so much that they no longer have to rely on external homes for protection. Coconut crabs are distributed throughout the Indian and Pacific Oceans, generally living in coastal areas. Scientists have long known that coconut crabs exert a ton of force compared to their mass when pinching with their claws but formal data had yet to be collected. Researchers associated with the Okinawa Churashima Foundation in Japan collaborated to study the pinching force of coconut crabs. The team collected 29 wild coconut crabs from Okinawa Island. The researchers tested the force exerted when the crabs pinched their claws. They found that as body mass went up, pinching force increased significantly. The largest crabs could potentially reach a force of 3,300 N (newtons). This was not only a stronger force than all other crustaceans but also stronger than the bites from most predatory animals. The only terrestrial animal that can beat the coconut crab’s force is the alligator. The team’s findings quantify the immense power of a coconut crab’s pinchers. Coconut crabs have the highest pinching force of any crustacean and in fact exert more force than most other terrestrial predators. The authors point out that the ability to break open coconuts and similar food sources may have given coconut crabs an edge during evolution. REFERENCE Oka S, Tomita T, Miyamoto K. A Mighty Claw: Pinching Force of the Coconut Crab, the Largest Terrestrial Crustacean. PLOS ONE (2016).