A Mighty Grip

You wouldn’t want to make a coconut crab angry. At up to 1 meter (3 feet) long, coconut crabs are the largest land crabs on Earth. Their huge front claws can lift as much as 28 kilograms (62 pounds)—and they pack a powerful pinch.

Coconut crabs live on islands throughout the Pacific Ocean. They use their massive front claws to defend against predators and crack open the hard shells of coconuts, one of their favorite foods.

But just how strong is the colossal crab’s pinch? Scientists in Japan wanted to find out. To do that, they set up a scientific strength test.

You wouldn’t want to make a coconut crab angry. These crabs are the largest land crabs on Earth. They reach up to 1 meter (3 feet) long. The animals have huge front claws. They can lift as much as 28 kilograms (62 pounds). And they pack a powerful pinch.

Coconut crabs live on islands in the Pacific Ocean. They use their huge front claws to keep away animals trying to eat them. The claws also allow crabs to crack open hard coconut shells. Coconut is one of their favorite foods.

But just how strong is the giant crab’s pinch? Scientists in Japan wanted to find out. So they set up a scientific strength test.

Biologist Shin-ichiro Oka had observed wild coconut crabs near his lab in Okinawa, Japan. “We could see the crabs’ amazing power,” says Oka. “But no one had scientifically measured the force of their grip.” 

Based on his observations, Oka came up with a research question. He wondered: How much force, or strength, can a crab’s claw apply with one pinch?

To answer his question, Oka first needed to collect data—facts and measurements to inform his thinking. To do that, he and his team studied 29 wild coconut crabs. 

The scientists measured each animal’s weight and length. Then they let each crab clamp down on a steel rod with a sensor inside. The sensor measures the strength of the claw’s squeeze. 

To draw fair conclusions, the scientists needed consistent data. They made sure to test the front-left claw of each crab. 

Shin-ichiro Oka is a biologist. He’d watched wild coconut crabs near his lab in Okinawa, Japan.

“We could see the crabs’ amazing power,” says Oka. “But no one had scientifically measured the force of their grip.”

Oka came up with a research question based on what he observed. How much force can a crab’s claw pinch with? Force is a measure of strength.

Oka first needed to collect data. These measurements would help him answer his question. He and his team studied 29 wild coconut crabs to do that.

The scientists measured each animal’s weight and length. Then they let each
crab clamp down on a steel rod. It had a sensor inside. The sensor measured the strength of the claw’s squeeze.

The scientists needed to make sure their results were reliable. So they tested the front-left claw of each crab.

Once they’d tested each coconut crab, the scientists analyzed the data they’d collected. They noticed a pattern: The heavier a crab was, the more powerfully it pinched. Oka calculated that the biggest coconut crabs can clamp down with almost as much force as a lion’s jaws! That’s 10 times the grip force of the average adult human.  

“We expected that the force would be very impressive,” says Oka. “But the actual power exceeded our expectation.” 

The results surprised Oka for another reason: Compared to its body size, a coconut crab’s claw muscles are relatively small. Oka next wants to find out exactly what gives the crab its superhero strength. 

Unfortunately for Oka, he knows the power of the crabs’ grip firsthand. He was pinched twice during the study! “Needless to say, it was incredibly painful,” he says.

The scientists studied the data they’d collected. They noticed that heavier crabs had a stronger pinch. The biggest coconut crabs could clamp down with almost as much force as a lion’s jaws! That’s 10 times the force of an adult human’s grip.  

“We expected that the force would be very impressive,” says Oka. “But the actual power exceeded our expectation.” 

The results surprised Oka for another reason. That’s because a coconut crab’s claw muscles are small compared with its body size. Oka next wants to find out exactly what gives the crab its superhero strength. 

Oka knows the power of the crabs’ grip firsthand. He was pinched twice during the study! “Needless to say, it was incredibly painful,” he says.