No matter how much we may love wildlife, the natural world is undeniably violent.
The sharp teeth and claws of carnivores are made to tear through flesh.
Venomous fangs unleash deadly, paralyzing toxins.
But when we think of dangerous projectiles, we probably think of human conflict.
Humans are the only animals in the world with the ability to throw an object and kill a
target.
Projectile use by organisms other than humans is rare - however, it is not unheard of.
Because battle for survival is indeed a battle, nature is endlessly inventive, and some species
have evolved their own version of ballistics.
Beetles can let out a barrage of toxic chemicals, certain fish can shoot prey out of the air
with 100% accuracy, and even mushrooms can send their spores flying at speeds unrivaled
in the natural world.
There are in fact hundreds of creatures who have projectiles in their arsenal, whether
it’s for hunting, self-defense, and even procreation.
And these organisms have been sources of wonder, fascination, and confusion for scientists
for centuries.
Earth is home to more than 400,000 species of beetle, and they can be eaten by just about
everything–frogs, toads, shrews, birds, and even other insects, like ants.
Having so many predators means beetles have evolved some incredible defense mechanisms.
Charles Darwin experienced this firsthand in 1846 when he was hunting on the forest
floor for different beetle species.
Having found two beetles already, he happened to see a third crawling under a piece of bark,
but his hands were already full.
“I could not bear to give up either of my Carabid beetles, and to lose Panagaeus was
out of the question, so that in despair I gently seized one of the Carabi between my
teeth, when to my unspeakable disgust and pain the little inconsiderate beast squirted
his acid down my throat.”
Chemical defenses like the one Darwin experienced first-hand are key to more than 500 species
collectively known as “bombardier beetles.”
These beetles rely on benzoquinones, toxic chemicals that are also used by millipedes,
daddy long legs, and many other insects.
But bombardier beetles do something completely unique: they trigger a chemical reaction within
their bodies that superheats the fluid and causes it to explode out.
Some species are even able to aim their spray nozzle in nearly every direction, including
over their own backs.
They manage this sensational act thanks to their unique physiology.
The beetles have two internal chambers with volatile chemicals in them, surrounded by
a flexible membrane and connected by a valve.
One of those chambers contains hydrogen peroxide and hydroquinone, while the other contains
peroxidases and other enzymes.
When the beetle feels threatened, it initiates the mixture of those liquids, triggering an
intense exothermic chemical reaction.
The boiling hot spray is ejected in rapid pulses up to 20 times before the chemicals
are completely depleted.
And all this happens without the beetle sustaining any damage from the toxic chemicals, or the
explosive reaction.
And the chemical eruptions are extremely good at protecting the beetles from predators.
One group of researchers looked at how the Pheropsophus jessoensis bombardier beetle
fared against toads.
They allowed the beetles to be swallowed, then could hear an explosion from inside the
stomach of the toads.
One species of toad vomited up 34 percent of the beetles, and another species vomited
back up 57 percent.
Whether the beetles were in the toads’ stomachs for only 12 minutes or up to 107 minutes,
they all survived the experience–and stayed alive for at least two weeks.
It’s rare that any insect can survive being in stomach acid for very long, but these beetles
managed it
Another group looked at how bombardier beetles fared against Japanese quail.
As it turned out, most of the quail rejected consuming the beetles, even if they weren’t
sprayed.
However, other birds, like jays, do ingest the bombardier beetles, but only after causing
them to eject their spray into the ground or into the birds’ plumage.
Jays seem to be too smart to get sprayed directly.
But given how many beetle species have evolved to be bombardiers, it’s clear that they
are getting some serious benefits from their explosive abilities.
But in the animal kingdom, not all projectiles are chemical, and not all shoot so indiscriminately.
Some animals are in fact so accurate with their shots, they rival human sharpshooters.
Using explosive energy to scare off predators is one thing, but actually shooting down prey
might sound like something else entirely–a skill that only humans have mastered.
But as it turns out, we’re not the only ones to hunt prey with projectiles.
In fact, it’s not even something unique to mammals.
All along the watery mangrove forests of the Indo-Pacific are schools of archerfish, who
have abilities that would give the best human sharpshooter a run for their money.
With an average size of 12 to 18 centimeters, and up to 40cm in the very largest species,
these archerfish combine good eyesight, a unique mouth shape, and incredible brains
to shoot jets of water at prey as far as three meters above them.
In lab settings, they can achieve a 100 percent accuracy in hitting their targets.
They’re so good at manipulating water as a weapon that they’re actually considered
to be tool users.
The mechanics of their water darts are relatively straightforward.
Archerfish have special grooves in their mouth and tongue that help focus the water.
They contract their gill covers to force water through that channel, and the jet can be 10
times their body length.
Because the force is greater at the rear, the front of the water stream becomes a blob
that forcefully dislodges prey from spiders to small lizards. [6]
As the prey falls towards the water, the archerfish are able to make a rapid calculation of where
their prey will be and and then shoot forward using a technique called a “C-start”--their
bodies curve inward, and straightening propels them forward.
These physical abilities are impressive enough, but for scientists, the most incredible part
of the archerfish is their brains.
First, consider all the challenges they face in simply locating prey above water.
In mangrove forests where most of these fish live, the water might be murky, or have ripples
on its surface from the wind.
Tree roots, branches, and leaves might obscure their view of prey, even when it clings to
the underside of leaves.
But sometimes they’ll shoot at prey on top of leaves, based solely on its silhouette.
And all of that is before calculating where the prey actually is.
Light experiences refraction as it passes from air to water, meaning the archerfish
can’t aim straight at the prey as they perceive it - they have to calibrate their shot with
this refraction in mind.
And they explore anything novel as potential food.
As one group of field researchers wrote, “the fish readily shot at cameras, spherical pieces
of bread, parts of equipment, objects printed on paper or the noses and eyes of experimenters.”
But the fish quickly learn to identify prey based on the reward they get from insects
falling into the water to be gobbled up.
But how exactly do these fish tell the difference between a fluttering leaf and an insect stretching
its wings?
Scientists aren’t entirely sure, but in laboratory experiments comparing the visual
abilities of archerfish against humans, the two species performed equally well.
Somehow, these fish are able to distinguish many different targets from their background
and shoot to bring them down.
And their brainy abilities don’t end there.
The fish can distinguish between smaller and larger numbers, even when that difference
is relatively small, like 3 vs 4.
Researchers also set up a test in which the fish were trained to respond to images of
specific human faces, and then tested by shooting water at the required face.
The researchers found the fish had an accuracy of up to 89 percent, even though they don’t
have the brain structure we normally associate with that ability.
They even rely on social learning to hone their shooting skills, becoming better at
aiming over time and with more experience.
In fact, they’re so good at social learning that in labs, the fish are able to become
very good at a new task just by watching another fish perform it, without doing any practicing
of their own.
Despite their incredible sharpshooting, archerfish still mostly eat aquatic prey–though they
sometimes use their water jets to dislodge crustaceans or small fish buried in the underwater
sediment.
Depending on their location, aerial prey might make up 25 percent of their diet.
Given this relatively small percentage, why did they evolve the ability to hunt with water
in the first place?
Scientists still aren’t sure, but hypothesize that it has to do with the fluctuating conditions
of mangrove forests.
It’s also possible that aerial prey provides nutritional components that they don’t get
from their aquatic diet.
It’s an ongoing question, but archerfish do prove that social skills, tool use, pattern
recognition and counting don’t belong to primates alone.
But in fact, projectile use doesn’t even belong solely to the world of animals.
Organisms that can’t even move themselves are capable of some of the fastest projectiles
that evolution has ever crafted.
We’ve already seen that organisms as different as insects and fish have found ways to incorporate
ballistics into their survival strategies.
But perhaps one of the most surprising examples of natural explosions are in fungi.
They may not be mobile like other life forms, but they still manage to generate some of
the fastest motions in the natural world–all so that their spores can spread as far as
possible.
Two genera of fungus in particular have mastered the art of high-speed motion despite holding
perfectly still.
And those are the Sphaerobolus and Pilobolus fungi, more commonly known as artillery fungus
and dung cannon fungus.
Both types of fungus grow on a variety of surfaces, from wood chips to leaf litter to
animal dung.
And both have relatively small fruiting bodies that grow toward light.
The main difference comes in their two strategies for ejecting spores as far as possible.
For both types of fungi, distance is crucial.
Because they can’t move on their own, they need a way of getting their spores beyond
the surfaces that they’ve already colonized.
This is especially important for the Pilobolus fungi, which needs to get past the “zone
of repugnance”--the dung it often colonizes.
That’s because part of its life cycle occurs in the guts of animals, so it needs to spread
its spores across grasses that an herbivore will munch on.
In order to move as far as possible, Pilobolus relies on fluid pressure.
As the stalk carrying the spore grows, fluid begins to swell below the spore.
The pressure builds, forming a bubble behind the spore, until finally it bursts, ejecting
the spore at incredibly high speeds–up to 210 m/s, which is nearly as fast as a bullet.
The Sphaerobolus fungi uses a different strategy to scatter its tiny spores.
In the spring and autumn, when temperatures are less than 25 degrees C, tiny buds start
pushing up toward the light.
The spherical fruiting body is tiny, with a diameter of just 2 millimeters, but at the
center it holds as many as ten million spores.
All around the spores are layers woven like a jacket, which slowly peel open as the spore
gets ready to burst free.
But instead of erupting like Pilobolus, the artillery fungus spores are ejected by a cup
that suddenly pops upward, like a tiny trampoline.
And what triggers this eversion is osmotic pressure, created by the conversion of glycogen
to sugars.
The spores can travel up to 6 meters in distance, and emit a tiny popping sound when they explode
out.
While the Sphaerobolus has an impressive spore-flinging capacity, it’s become something of a nuisance
for homeowners.
The brown and black spores stick to vinyl siding, windows, and cars and can be challenging
to remove.
But ultimately the fungi are harmless, and an incredible example of nature’s ingenuity.
It’s easy to assume that humans hold a monopoly on inventiveness, especially when it comes
to things like weapons.
But as should be clear, the natural world finds plenty of ways to upend our expectations.
Our cleverness has helped us develop plenty of strategies for manipulating our environment–but
sometimes, evolution can help organisms pull off some of the same tricks.
To truly understand just how incredible some of these feats of ballistics are in the animal
kingdom, I took a quick course on Brilliant.org to wrap my head around the mathematics behind
accurate target shooting.
When researching this video, my mind was so blown by the archerfish’s 100% accuracy,
that I wanted to know more about how this could be possible.
The Classical Mechanics course on Brilliant has a section about Projectile Motion, so
I dug right in.
The course was challenging, but Brilliant doesn’t penalize you or impede your progress
- instead they give you an in depth explanation to guide you to the right one, so you can
learn from your mistakes.
Its easy to learn in this low pressure environment, and most importantly its easy to learn by
doing.
After I finished, I was even more impressed by the archerfish, who does what they do without
the help of the internet or courses like the ones on Brilliant.
My favorite part of Brilliant is the interactivity.
Seemingly daunting courses like computer science are broken down into fun and engaging lessons,
with animations and interactive challenges making it all so much more understandable.
It is so hard to absorb information from text books and college lectures sometimes - with
Brilliant, it is fun and almost feels like a game.
And their courses are for everyone, whether you are looking to brush up, or to dive deep
in math, science or computer science.
To get started for free, visit to brilliant.org/realscience or click on the link in the description, and
the first 200 people will get 20% off Brilliant's annual premium subscription.
And if you’re looking for something else to watch right now, you can watch our previous
video about the insane biology of humans, or watch real engineerings latest video about
the incredible engineering of the F35B.