The mantis shrimp, like the honey badger, is internet royalty. They’re the stuff of breathless blog posts and flamboyant memery, practically built for the Impact font. There aren’t many marine invertebrates which get this much love. But you know what? Like the honey badger, the mantis shrimp deserves every bit of attention it gets. It is a rocking-socking monster of a shrimp, and if I’m merely adding to the chorus of folks who’ve talked about this thing, that’s fine.
So, the mantis shrimp. You might be used to thinking of shrimp mostly in their frozen, curled up supermarket form, but there’s a whole crustacean world to explore. Shrimp inhabit a wide variety of ecological niches and offer up a bewildering array of behaviors. There is, for instance, a eusocial (think ants and bees), sponge-dwelling shrimp that lives in the Caribbean. The pistol shrimp, which uses a special claw to create and ‘snap’ bubbles so loud that they stun nearby prey, is a particularly fascinating example. And then there is the mantis shrimp, one of the most vicious little predators around.
Humans tend to drool over ‘charismatic megafauna.’ We like big things with relatively complex behaviors, especially the ones that sit at the very top of the food chain — killer whales, great white sharks, those sorts of critters. But there’s far more action going on in the lower trophic levels, and in many ways the action there can be more interesting. It’s certainly just as cutthroat.
Although they’re pretty small — around 4”, although some can hit a foot or more — mantis shrimp punch well above their weight. They’re mostly ambush predators, living in burrows which they dig out of sand or rock. If a shrimp being able to dig into rock (mantis shrimp are really good at this) surprises you, wait, because there are plenty more surprises coming.
That an ambush predator has very good vision is hardly shocking. Being able to see one’s prey is general helpful for catching it. But mantis shrimp don’t just have great vision. Their eyes the most complex ever to evolve. With sixteen types photoreceptors, they can see an absurd variety of colors, reaching well into the ultraviolet. For reference, humans have three. Having a mantis shrimp’s eyes would be like being able to see octarine.
They can also detect polarized light, which both helps them with contrast detection and local navigation, important for when they’ve chased down their prey and need to get back to safety. Oh, and their individual eyes are segmented into three main regions and thus are capable of depth perception individually through cross-referencing the information from each region.
While they’re extremely cool and extremely interesting — the polarization techniques they use rival the best we can do with cutting-edge science — the eyes aren’t the coolest part of the mantis shrimp’s arsenal. They are, in fact, not even close. That title belongs to their ridiculous claws.
One of the really neat things about invertebrates is the internal energy storage mechanisms evolution has bequeathed them with. By using structures like ratchets and gears to store and release energy, the world’s smallest creatures can deploy explosive force when they need to. This, for instance, is how grasshoppers can jump so high. It is also how mantis shrimps can produce the fastest punch on the entire planet.
Not all mantis shrimps are punchers. Broadly speaking, you can split them into two groups, ‘spearers’ and ‘smashers.’ The spearers jab, impaling fish on their long, barbed claws, and the smashers ... well, I think you probably get the idea. Smashers feed on hard-shelled crustaceans like crabs, and as a result their claws look more like big ol’ clubs:
These clubs are built to smash through armor, and through armor they smash. For a long time the mechanics of the punch were almost entirely unknown, but with the advent of underwater-capable high-speed cameras, the marvels of the mantis shrimp were revealed. The reason nobody could see the punch, as it turns out, is that it takes three milliseconds to carry out. Blink and you’d miss it. Blink and you’d miss dozens.
The accelerations involved here are mind-boggling, on the order of 100,000 meters per second, which is more than 10,000 times the force of Earth’s gravity. Back when I was not doing random blogging for a living, I studied the structural integrity of biological materials, so it’s with some tiny authority that I say I have absolutely no goddamn clue how the mantis shrimp does this without its little arms exploding.
But its arms do not explode. That cannot be said for whatever it’s punching. The world record for human punch speed belongs to Keith Liddell, who managed to record a 45 mile per hour blow in 2013. The mantis shrimp beats this easily, regularly hitting 50 mph or more. And it’s doing this underwater!
Water, of course, has far more resistance than air, but the mantis shrimp’s little clubs move through it like it’s not there. That is in fact sort of true: the speed of the punch moves the water out of the way, creating a series of cavitation bubbles which then collapse, adding to the force of the punch, and enabling a mantis shrimp to kill their prey even if they miss.
The interaction between shrimp club and water isn’t limited to bubble creation. When the bubbles collapse, they generate heat. Ludicrous amounts of heat. Local temperatures can rise to the order of several thousand degrees, creating an effect called sonoluminescence, which I believe is Latin for ‘the water is punched so hard it glows’.
To summarise, a mantis shrimp’s punch is:
- Faster than humanly possible, even underwater
- So fast it creates a cavitation shockwave which impacts its victims even without the punch connecting.
- So fast it causes water to heat up and glow.
So, yeah, a mantis shrimp is basically a 4” Dragon Ball Z character.
Unsurprisingly, they’re difficult to keep in aquariums, because they brutally murder anything that comes near them and are also so ornery and territorial that they’ll punch their own reflections in an attempt to make them go away. And since they can punch hard enough to pulp crab armor, that’s bad news for aquarium glass (and any inhabitants of the aquarium who’d contrived to escape their tankmate’s wrath).
Add it all up and you have a ferocious tiny predator with a murderous, physics-bending set of claws that also hates the company of man. They are, in other words, extremely neat critters. As long as you’re not within punching distance.