The coconut crab’s pinch is the strongest in the world

Despite having been studied for more than 100 years, coconut crabs have largely remained a mystery to biologists.

In a new study, researchers have found the crustaceans have claws capable of exerting 742 pounds of force, despite typically weighing 10 pounds or less.

Coconut crabs are the largest hermit crabs on the planet, but unlike most hermit crabs, mature coconut crabs do not scavenge sea shells to protect their vulnerable backside. Instead, they rely on their massive, powerful claws and tough exoskeleton to ward off attacks from would-be predators.

Researchers behind the new study said they found out firsthand just how painful a pinch from those claws could be.

“When I was pinched, I couldn’t do anything until they unfastened their claws,” study author Shin-ichiro Oka, from the Okinawa Churashima Foundation, Japan, said in a news release. “Although it was only a few minutes, it felt like an eternal hell.”

Finding the Crab’s Crushing Strength

To reach their conclusion, researchers assessed the claw pinching drive of 29 coconut crabs on Okinawa Island, Japan. The team found pinch pressure elevated with crab body mass.

“We expected the force would be very strong, but the actual power exceeded our expectations,” Oka said. “We were surprised that their pinching force was approximately 90 times their body weight — if I was a coconut crab weighing 65 kg (143 pounds), I could crush something with about 6 tons of force!”

The crunch of a coconut crab is stronger than all other crustaceans. The crabs’ pinch is even stronger than the bite of any land predator. One big exception is the alligator, which can bite down with nearly 2,900 pounds of force.

The crabs use their claws for more than defense and hunting. They also allow the crustaceans the ability to crack through coconuts, a skill which is crucial to maintaining their tremendous size. At up to a yard across, coconut crabs are the world’s biggest land arthropods, or invertebrate animals with an exoskeleton. Despite the fact that female coconut crabs discharge their eggs into the ocean, adult crabs are land animals. Their spongy gills are even lung-like, taking up oxygen from the air.

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Image credit: Thinkstock

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