How Hard Does a Mantis Shrimp Punch? Speed and Force

How fast is a mantis shrimp punch?

The peacock mantis shrimp is a smasher, a type of mantis shrimp with heavy, club-shaped raptorial appendages folded under its head. In high-speed video recordings, its clubs moved at about 14–23 m/s (50–83 km/h, 31–51 mph), starting from a standstill. The whole strike is over in a few thousandths of a second, faster than a human eye can follow.

The acceleration is the most extreme figure. A club that reaches more than 100,000 meters per second squared goes from rest to top speed almost instantly, which is why the strike is often compared to a bullet leaving a gun. The comparison only works for acceleration, though: a bullet ends up traveling more than ten times faster.

How does a mantis shrimp punch so fast?

No muscle can contract fast enough to produce this strike directly. Instead, the mantis shrimp uses a spring-and-latch system, a type of power amplification also found in some jumping insects.

First, large muscles in the appendage slowly contract while a small latch holds the club in its folded position. The muscle force compresses a springy, saddle-shaped structure in the limb, storing elastic energy, much like drawing back a bow. When the latch is released, the stored energy is let go all at once and the club snaps forward.

Because the strike is so fast, it cannot be steered once it has started. The mantis shrimp has to aim before it lets go, using its excellent eyes to judge distance precisely.

The double hit: cavitation bubbles

The club moves so fast through the water that the pressure just in front of it drops sharply. This causes cavitation: small bubbles of water vapor form between the club and the target. A fraction of a second later the bubbles collapse, releasing a sharp burst of energy.

In lab experiments, the impact of the club itself produced forces of up to about 1,500 N, and the collapsing bubbles added a second force peak of up to about 500 N. So the prey is hit twice by every strike: once by the club and once by the bubbles. Even if the club only just misses, the collapsing bubbles can still damage or stun small prey.

Cavitation is usually a problem for engineers, because it wears away ship propellers and pumps. The mantis shrimp turns it into a weapon. A distant relative, the snapping shrimp, uses the same physics in a different way, snapping its claw to create a collapsing bubble that makes one of the loudest sounds in the sea, as described in loudest animals.

Why doesn’t the club break?

Hitting hard shells thousands of times would shatter most materials, so the club’s structure has been studied closely by materials scientists. It is built in layers.

The outer hitting surface is a dense layer of hydroxyapatite, a calcium phosphate mineral also found in bone and tooth enamel. Behind it, fibers of chitin, the tough material of crustacean shells, are stacked in layers that are each slightly rotated, forming a spiral pattern. When a tiny crack forms, it is forced to twist along this spiral instead of running straight through, which absorbs energy and keeps the club in one piece.

Damage still builds up over time, but the mantis shrimp gets a fresh club surface every time it molts, shedding its old outer skeleton and growing a new one. Engineers have used the design as inspiration for tough, lightweight composite materials.

What do mantis shrimp punch?

Peacock mantis shrimp use their clubs mainly to break into hard-shelled prey: sea snails, crabs and bivalves such as scallops. They hit the same shell again and again until it cracks, then pull out the soft body with their smaller limbs.

They also use their clubs against each other. In fights over burrows, rivals often strike each other’s broad, armored tail plate, called the telson. The telson is the most heavily protected part of the body and absorbs the blows, so these contests let mantis shrimp test each other’s strength without serious injury most of the time.

Myths and facts

“Mantis shrimp have the strongest punch in the animal kingdom.” The strike is extraordinary for an animal only a few centimeters long, and it is among the fastest limb strikes ever measured. But ranking “strongest punches” across animals of very different sizes is not really possible. Some ants snap their jaws even faster, so the mantis shrimp is best described as one of the fastest strikers, not the single champion. For other speed records, see fastest animals.

“A mantis shrimp punches like a .22 bullet.” Only in acceleration. The club tops out at about 23 m/s, while a bullet travels hundreds of meters per second and carries far more energy.

“Mantis shrimp can break aquarium glass.” There are real reports of large smashers cracking aquarium glass, but they are uncommon. Ordinary thick glass is not routinely broken.

Can a mantis shrimp hurt a person?

Yes, if handled. Mantis shrimp are not aggressive toward people and have no venom, but a large one striking a finger can cause a painful injury. Fishers and divers in some regions call them “thumb splitters”. Underwater, the safe and respectful approach is to watch them from a short distance and never put your hands near a burrow.

For the other remarkable feature of these animals, their eyes, see Can mantis shrimp see more colors than humans?.