Coconut Crab Claws Have The World’s Strongest Pinch Among Crustaceans

Coconut crabs’ claws already look fearsome enough as it is, but appearance merely tells part of the story. According to a new study, these claws may actually be the most powerful in the entire animal kingdom.

The Christian Science Monitor describes coconut crabs as native to the Indian and Pacific Oceans, and capable of growing to lengths up to three feet and weighing close to nine pounds. They are the largest terrestrial crabs in existence, and while they usually feed themselves with hard-shelled coconuts and other forms of vegetation, they may even feed on kittens and other small animals.

Just how strong are coconut crab claws? As the Christian Science Monitor pointed out, it’s already quite an awesome feat to open up a coconut without the help of any tools. And with that in mind, researchers sought to test the strength of coconut crab claws and see how much force they exert when pinching.

As it turns out, they have the world’s strongest pinch among crustaceans, exerting up to 3,300 newtons, or over 4.5 times more forceful than most humans can grip. According to a separate report from Reuters, that translates to up to 742 pounds, or 336.5 kilograms of force and makes coconut crabs more powerful than most land-predators. Crocodiles are still far more forceful, as their bites exert about 16,460 newtons, but coconut crab claws are much closer in force to the bites of lions, tigers, and hyenas, who only exert about 4,450 newtons when snapping their jaws shut.

In an email to the CSMonitor, lead author Shin-ichiro Oka of Japan’s Okinawa Churashima Foundation described how surprising it was to discover coconut crabs can be so powerful.

“We expected the force would be very strong. But the actual powers exceeded our expectation. And we were also surprised that their pinching force was approximately 90 times of their body weight.”

Putting it into context, Oka added that if his grip was as powerful as that of a coconut crab’s claws, he’d be able to crush objects with six tons of force, given his weight of about 145 pounds.

The Reuters report further quoted Oka, who said that the claws are used for both accessing otherwise difficult-to-reach food sources and beating other predators to that food and also for self-defense purposes. They may also fight each other for prey and use their claws accordingly to ward off other crabs. Coconut crabs’ claws are believed to have evolved over time, as the animals had transitioned into a terrestrial existence.

#coconutcrabs are the largest #arthropod in the world. They can #live for 60 years & feed on fruits & nuts. #crabs pic.twitter.com/qKLtvtnEKB

— WildAware (@Malin_WildAware) June 25, 2015

“Their mighty claws also allow them to be active predators by facilitating effective hunting and feeding on other terrestrial organisms with hard exteriors, thereby aiding in the maintenance of their large body size,” wrote the researchers in their paper, which was published Wednesday in PLOS ONE.

“In particular, the ability of these crabs to open coconuts demonstrates the impressive force of their claws.”

While evolution may have shaped coconut crab claws into what they are today, the question of how they had become so forceful and powerful when pinching is one that may be more interesting to ponder. Western University (Canada) biologist Graeme Taylor, who was not involved in the study, told the CSMonitor that it may be due to their unusually long sarcomeres, or muscular features that allow skeletal muscles to contract.

“One of the things that crabs have is a very large concentration of muscle fibers that have a unique property, being exceptionally long sarcomeres.”

Coconut crabs aren’t just known for their claws and how forcefully they can pinch, but also for being very strong in general. Reuters noted that these crustaceans are capable of lifting items weighing up to 66 pounds (30 kilograms), while a report from the Daily Mail mentioned in February that they can live for as long as 60 years.

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