Coconut crab’s pinch is as strong as a lion’s bite

28 Nov 2016

Coconut crab. All images: Kristina Vackova/Shutterstock

Coconut crabs are infamous, large (up to 18in long), tree-crawling, land-dwelling crustaceans. Researchers are now adding to their status as fearsome creatures, finding that their pincers are mightily strong.

“The pinching force of the largest coconut crab is almost equal to the bite force of adult lions.”

That’s a nice, terrifying quote attributed to marine biologist Shin-ichiro Oka, leader of recent research investigating just how strong the coconut crab’s grab really is.

Coconut crabs

Studying dozens of crabs with force-measuring sticks, Oka and colleagues saw the largest, strongest specimen tested exerting up to an amazing 336.5kg of force.

Though the might is surprising, the need for strong claws is understandable.

Oka’s paper, published in PLOS One, notes the necessity for a strong pinch when sourcing the variety of foodstuffs that coconut crabs ingest during their lifetime.

The crabs often fight aggressively with each other and other animals for food and resources, with the “mighty claws” acting as useful weapons to deter predators and competitors.

Coconut crab

Fruit, fallen tree pith and carrion are all on the menu, but as its name suggests, the ability of these crabs to open coconuts demonstrates the impressive strength of their claws.

“The force is remarkably strong,” said Oka to Reuters. “They can generate about 90 times their body weight,” allowing them to “crush something with about six tonnes of force”.

Coconut crabs are related to hermit crabs, though their reliance on a shell disappears in later life. By then, a bumpy, calcified body offers enough protection.

Independence from shells removes restrictions on body size, and has possibly led to the development of new functions associated with their large claws.

Oka’s research concludes that coconut crabs have the ability to exert the greatest force among almost all terrestrial animals – though alligators are stronger.

“I was pinched two times,” said Oka. “When I was pinched, I couldn’t do anything until it unfastened its claw. Although it was only a few minutes, I felt eternal hell.”

Gordon Hunt was a journalist with Silicon Republic