Could Piranhas Really Eat a Cow in Under a Minute?

Piranhas are very efficient eaters, but their frothing feeding frenzy seen in horror movies is mostly based on a myth started by Theodore Roosevelt. Learn more in this episode of BrainStuff, based on this article: https://animals.howstuffworks.com/animal-facts/piranha-eat-cows.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff. Lorn
voleban here. When Theodore Roosevelt went on a hunting expedition
in Brazil in nineteen thirteen, he got his money's worth.
Standing on the bank of the Amazon River, he watched
piranhas attack a cow with shocking ferocity. It was a

(00:25):
scene out of a horror film of water boiling with
frenzied piranhas and blood, and after about a minute or two,
a skeleton floating to the suddenly calm surface. Roosevelt was
appropriately shocked and talked about it in his nineteen fourteen
book Through the Brazilian Wilderness. He wrote, they are the

(00:46):
most ferocious fish in the world. They will snap a
finger off a hand incautiously trailed in the water. They
mutilate swimmers. In every river town in Paraguay there are
men who have been thus mutilated. They will rend and
devour alive any wounded man or beast, for blood in
the water excites them to madness. Thus the American legend

(01:08):
of the piranha had begun. Hollywood picked it up from
there with the nineteen seventy eight horror flick Piranha, directed
by cult film Officionado Jo Dante, notably right after the
smash hit Jaws came out in nineteen seventy five, When
flesh eating piranhas are accidentally released into a summer resorts rivers,
the guests become their next meal. It was followed by

(01:32):
nineteen eighty one's Piranha two The Spawning, which was James
Cameron's directorial debut, and then a comedic remake of the
original in twenty ten Pirana three D, followed by its
sequel in twenty twelve, Pirana three Double D. All of this,
although purposefully silly, cemented the idea of the piranha as

(01:53):
a threat in our minds. But is this fish's vicious
reputation desert let's find out. First off, we're not talking
about gargantuan monsters here. Piranhas top out at about two
feet long that's sixty centimeters, and most are only about
eight inches or twenty centimeters and weigh just a few pounds.

(02:18):
The most aggressive of the roughly twenty species found in
the Amazon River, the red bellied piranha, is on the
small end of the spectrum and usually weighs about three
pounds or a little less than one and a half kilos. However,
in the case of piranhas, it's not the size that counts.
It's the bite. A piranha's teeth they're only about a

(02:39):
quarter inch long around four millimeters, but they're very finely serrated,
and the whole jaw mechanism is designed for chomping efficiency.
The teeth are spaced in an interlocking pattern, so when
a piranha jaw snaps shut, the top teeth and bottom
teeth interlace like dozens of pairs of scissors, and their

(03:01):
jaws are strong they can bite right through the bone
of say a human tow. Furthermore, piranhas don't chew. When
they bite down, the chunk of flesh they take out
of their prey goes right into their bellies. They just
keep snapping their jaws shut and filling themselves up. Also,

(03:21):
paranas are very efficient team eaters. A school and a
feeding frenzy will rotate continuously, so as each piranha takes
a bite, it moves out of the way so that
the fish behind it can get a bite, and so on.
They take turns at such speed that you get that
boiling water effect. If a large enough school was aggressive

(03:42):
enough It's entirely possible for piranha's too strip an animal
as big as a cow in just a few minutes,
if not under sixty seconds. But the key thing to
know about Roosevelt and his story is that although he
explored the Brazilian Amazon as an avid hunter, he wasn't
exactly the average tourist. He was a former US president

(04:06):
traveling with dozens of journalists, and his guides wanted him
to be very pleased with his trip. Feeding frenzies are
not an everyday occurrence. Roosevelt's guides in Brazil had set
up the scene for their famous guest. They set nets
to close off a small part of the river and
tossed hundreds of piranhas into it, trapping them at a

(04:27):
larger density than their usual school of twenty plus. By
the time they threw that poor cow into the water,
the poor piranhas were stressed and starving, So eating an
entire cow in a minute or two is not the norm.
But what and how do piranhas usually eat. Attacking a live,

(04:49):
land based animal isn't out of the question for piranhas.
They have been known to attack sick or old animals
that come to drink from the river. When a cow
lowers its head, they'll clamp off to its face. If
the cow is too weak to fight back, the piranhas
will drag it into the water and beat it. But
live mammals are not the mainstay of their diet. Mostly

(05:10):
in that category they're scavengers. The skeletons of people and
other land based animals found in the Amazon apparently eaten
by piranhas weren't attacked alive. They were already dead when
the piranhas got to them. As with other fish, land
based mammals are by no means a big part of
the purana's diet. They eat other fish, mostly including sometimes

(05:33):
other puranas, along with insects, worms, and shrimp. They will
ambush prey by lurking and then dashing out, but puranas
aren't even strictly carnivores. They'll eat pretty much anything they
can get, including fruits and other plants, especially when they're young.
The truth is that, contrary to legend, most piranhas don't

(05:55):
really attack anything. Most of the species and the Amazon
survive in entirely by taking small bites out of the
fins and scales of other fish as they pass by.
The fish swim away only slightly disturbed, and their fins
and scales grow back. Humans can also get in necked
deep enough to need stitches, and sadly, that is happening

(06:16):
more often in recent years, as dams and human habitation
having encroached on piranha's native territory in the fresh water
ponds and creeks of South America. To come full circle
of life, piranhas themselves have few predators, aside from humans
who sometimes catch them as food or kill them as
a pest. Even though puranhas are small, they're seldom eaten

(06:39):
by larger fish that tend to gulp their prey that
razor sharp bite would really hurt going down. But during
the dry season, piranhas are eaten regularly by herons and
cayman lizards. When water levels are low and the fish
end up trapped in increasingly small ponds but no food,
Unable to defend themselves, the herons and cayman's come in

(07:01):
and finish them off. Because of that lack of predators,
many countries of outlawed the import or possession of piranhas,
even as aquarium pets, the risk they might be released
into local waters and cause a serious threat to the
ecological balance there is too great. But still as hazardous
as piranhas can be in large and hungry numbers, you

(07:25):
probably don't need to be as worried about them as
Theodore Roosevelt or the B movies tell you. Today's episode
is based on the article can piranhas really strip a
cow to the bone in under a minute? On how
stuffworks dot com, written by Julia Layton. Brain Stuff is
production by Heart Radio in partnership with how stuffworks dot

(07:46):
Com and is produced by Tyler Klang. Four more podcasts
my heart Radio, visit the iHeartRadio app, Apple Podcasts, or
wherever you listen to your favorite shows.