KENNETH CATANIA: Most of the things
that I have found of studying these eels have been things
that have just sort of fallen out of watching the behavior.
And the most recent one certainly
falls in that category.
As I approach the electric eels, the bigger ones
would periodically turn around, make a very rapid approach
to the net, and then sort of leap up
the handle towards my hand, while giving off
high voltage volleys.
I was recording the high voltage output
through electrodes that went into a speaker.
It was quite shocking to experience.
In the midst of sort of thinking about what all this meant,
I came across a really amazing figure showing an experience
by Alexander von Humboldt in 1800.
ERIC KUHL: "We were conducted by the Indians
to a stream rich in the time of drought
from the basin of muddy water.
To catch the [INAUDIBLE] with nets is very difficult.
The Indians therefore taught us that they
would fish with horses.
The extraordinary noise caused by the horse's hooves
makes the fish issue from the mud
and excites them to the attack.
A contest between the animals of so different an organization
presents a very striking spectacle.
The Indians prevent the horses from running away.
The eel, being 5 foot long and pressing itself
against the belly of the horses, makes
a discharge along the whole extent of its electric organ.
The horses are probably not killed, but only stunned.
They are drowned from the impossibility of rising
amidst the prolonged struggle."
KENNETH CATANIA: This was a total spectacle.
And when I first heard about that story,
I was very skeptical.
Why would eels go on the offensive,
and could they possibly attack horses?
I have a broad interest in brain evolution and different animal
sensory systems, and often really intrigued
by the outliers, sort of mysterious animals.
So the electric eels are really interesting in that they
are not related to other freshwater eels.
They're really an electric fish.
And I kind of like to say the electric eel went down
the weapons of mass destruction pathway from that origin.
LUKE GEOSKIN: Most of the eel's body
contains electric organs with the head giving off
a positive charge and the tail negative when zapping a fish.
KENNETH CATANIA: They're essentially
a series of batteries lined up one after another, in series,
the way you might put a whole bunch of batteries
in a long, powerful flashlight.
And those add together to give 600 volts, ultimately,
for a large electric eel.
LUKE GEOSKIN: In the few years that Catania's
been studying eels, he's looked at how they stun their prey.
KENNETH CATANIA: The eel can remotely
activate the prey's muscles through the nerves
to temporarily paralyze it.
And that is the same as a Taser.
LUKE GEOSKIN: And eels can control
the intensity of their shocks.
So what would make an eel emerge from the water,
as recounted by Humboldt and now seen by Catania?
To find out, Catania used some unconventional props.
KENNETH CATANIA: So what I did was
to take what I thought was a good stand in predator,
a crocodile head, and I drilled holes in it
and put LEDs that could be lit up by the electric eel
as it ascended out of the water.
And I wanted to take it a step further
and get people to imagine what it might be like if this
actually happened to them.
So I took some sort of Halloween zombie arms
and put LEDs into these as well.
Normally, the eel is in the water
and a lot of this electric current spreads.
And what was interesting is the voltage
increased as the eel rose up out of the water.
By placing its positive end against the potential threat
and rising up out of the water, that makes a new current path
to complete the circuit through the threat.
LUKE GEOSKIN: This isn't a hunting behavior though.
The eels were not looking at the horses or Catania's zombie
arms as prey.
KENNETH CATANIA: In the Amazon, there's a rainy season.
And then there's a dry season where a lot of fish,
including electric eels, get caught in these residual pools.
And actually that's exactly what was the case when Humboldt went
to collect the electric eels.
Those eels were trapped in a drying pool from a stream.
They can't retreat.
And so they need another option to defend themselves.
It's a situation, I think, where the best defense
is a good offense.