What happens when you fall into piranha-infested waters? - Antonio Machado-Allison
You’re peering into the Amazon River
when, suddenly,
you lose your footing and fall.
Piranhas dart about in the rapidly
approaching water.
So, are you doomed?
Will your fall trigger
a fatal feeding frenzy?
To forecast your fate, let’s see
what we know about these fish.
There are more than 30 piranha species.
All live in the fresh waters
of South America
and have a single row of sharp,
interlocking teeth on each jaw.
They use their teeth in a variety of ways.
Many are omnivorous and supplement diets
of things like insects,
crustaceans, worms, and fish
with fruits, seeds,
and other plant matter.
Some, like red-bellied piranhas,
both hunt and scavenge.
And others, like wimple piranhas,
have specific dietary predilections,
almost exclusively going
after other fish’s scales.
Species like redeye piranhas
are more solitary,
while red-bellied piranhas
form shoals of 10 to 100.
Red-bellied piranhas are among
the most popularly depicted
and commonly regarded
as especially aggressive.
However, their reputation for rapacious
pack hunting is misinformed.
It’s thought that the main benefit
of their group-living
isn’t cooperative hunting
but instead protection from predators,
of which they have many.
Larger, mature red-bellied piranhas
tend to assume privileged positions
at the shoal’s center,
where it’s safest.
And scientists have observed that
red-bellied piranhas in smaller groups
breathe faster,
probably because they’re more anxious.
Interestingly, they also communicate.
By rapidly contracting specialized muscles
above their swim bladders,
they repeatedly “bark” when they’re facing
off with one another or when captured.
They make thudding noises when they’re
aggressively circling each other,
fighting, or competing for food.
And when things escalate further,
they chase each other
while snapping their jaws together.
Researchers suspect that these sounds
are just a sampling
of their overall repertoire,
which might also have
some special uses during mating.
But when do red-bellied piranhas
get aggressive with humans?
Well, when they do bite people,
it seems to mostly happen in scenarios
when they’re being handled;
when people are spilling food or
cleaning their fishing catch in the water;
or when people disturb piranhas
while the fish are mating
or guarding their eggs
during the wet season.
Starvation stress is also thought
to lead red-bellied piranhas
to increasingly bold, aggressive behavior.
And this could theoretically result
in feeding frenzies
where each fish tries to get some
of whatever finds its way into the water.
Despite this kind of behavior
being extremely rare,
rumors of it launched the piranha’s
international infamy.
And this was in no small part thanks
to former US President Theodore Roosevelt.
In 1914, he published a bestselling book
in which he called piranhas
“the most ferocious fish in the world”
and wrote that the scent of blood
could incite them
to rapidly devour an entire cow—
or human— alive.
But Roosevelt’s account is generally
considered circumstantial and misleading.
The “feeding frenzy” he witnessed is
suspected to have been the result
of people purposefully starving
red-bellied piranhas,
then giving them the opportunity
to feed on a cow carcass—
all to put on an exciting show.
But where were we?
Ah, yes.
Falling into piranha-infested waters.
So, what’s your fate?
Let’s assume these are
red-bellied piranhas.
This being the Amazon River,
they should be doing alright
for themselves and not starving.
Thankfully, you’re also not hitting
the water alongside a bunch of fish guts.
And ideally, you're not disrupting
a piranha breeding extravaganza.
You fall in, and the piranhas
most likely avoid you.
Calmly, softly swimming or wading to shore
is generally recommended
because splashing is thought
to attract piranhas.
Indeed, they’re equipped
with the dentition to do damage,
but they rarely attack humans.
They usually have better things to eat.
As you make your way onto dry land,
there is no feeding frenzy where they
skeletonize your body within minutes.
And upon exiting the water,
you're probably pleased to find
no chunks of flesh missing.
