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This episode is brought to you by the Music for Scientists album! Stream the album on major music services here: Check out “The Idea” music video here:

We’ve long thought that electric eels hunt individually…until we discovered a lake where one species hunt, and zap, in packs!

Hosted by: Hank Green

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This episode is brought to you by the Music for Scientists album, now available on all streaming services. [♪ INTRO].

In the late 2010s, scientists realized that what everyone had long thought of as one species of electric eel was actually three. Also, they figured out that in the biggest species, which they decided to call Volta’s electric eels, individuals grow to be over two meters long and can stun their prey with an 860-volt electric shock.

That’s over fifty times the voltage of a car battery! But… that’s not the most shocking thing about them.  Thanks to further research on this newly described species, we now know that these eels can hunt, and zap, in packs! Electric eels are basically living tasers.  They have specialized “electric organs” that contain thousands of special cells called electrocytes.  These generate and store electricity until it is time to unleash a zap.

But until recently, we didn’t know much about how these giant fish hunt, since they’re kinda hard to find. They live in remote, murky waterways in South America. Waterways that people are, understandably, like a bit hesitant to dive into.

There’s a bunch of electric eels in there.  We assumed, based on the few observations that had been made, that all electric eels hunt at night, alone, using their supercharged abilities to stun small fish. So it came as a surprise when researchers found a lake on the Iriri River in Brazil's state of Pará where more than a hundred of them appeared to be hanging out together in a big electric eel gang.  Scientists first noticed that something weird was up with the eels in this lake in 2012, and they returned in 2014 to collect more data. They found that these giant packs of eels actually hunt cooperatively.

Massive groups of eels in the lake, as many as a hundred at a time, work together to drive schools of fish into tight balls. Then, a few eels move in close to deliver a massive shock to the cornered fish, stunning them so hard that they sometimes fly right out of the water. Once the fish are stunned, the eels can all enjoy an easy and enormous meal.

I mean, yikes! There are still a lot of unanswered questions about electric eels’ cooperative hunting behavior. For one thing, it’s not clear how the eels coordinate.  Though, some other fishes use gentle pulses of electricity to talk to one another.

So, it’s possible they’re somehow communicating via low-voltage shocks! Which would be very cool. Also, the researchers haven’t been able to measure exactly how much voltage is actually delivered when the eels work together.

Of course, “a lot” is probably a safe guess! And no one knows if all this is unique to the eels living in one lake. The lake certainly has features that might encourage cooperative behavior, including a lot of available prey and a lot of room for eels.

Those factors could come together in other places, but if roving packs of hungry eels working together were a common occurrence, you’d think we’d have heard about it by now. But, maybe not. There’s a lot we don’t see happen in those murky waterways!

So the scientists who discovered this have a lot of fun field work ahead of them to sort out all the details. In the meantime, we all get to be stunned by the incredible ingenuity of these fish.  Speaking of things that have stunned me: I loved the Music for Scientists album, written and recorded by Patrick Olson. It’s an artistic tribute to everyone who has dedicated their lives to science and science-driven work, and every song is beautiful.

For example there’s the song “the current,” which isn’t/about electricity, but it is about that uniquely wonderful feeling that psychologists call “flow” and how you can lose yourself in music. I do that all the time. So, if you want to check it out, look for “Music for Scientists” on any of the major music streaming services. [♪ OUTRO].