07/22/2016

The Shocking Behavior of Leaping Eels

5:01 minutes

Scientists have long known that electric eels can send out short pulses of electricity to sense their environment and also to paralyze their prey. But one researcher has recently discovered that eels can also use powerful electric pulses to attack or defend themselves while leaping out of the water.

Neurobiologist Ken Catania has been studying eels for several years. In fact, he keeps at least two tanks of eels in his lab for observation. One day, while he was moving one of his larger eels — a three-foot eel — from one tank to another, the eel turned around and started aggressively swimming toward him and trying to leap up at him out of the water.

This was behavior Catania hadn’t ever seen before, so he decided to study it further. He gathered a series of props — a fake crocodile head, a fake human arm — and rigged the props with LEDs that would light up when the eels attacked.

Video producer Emily Driscoll visited Catania’s lab to learn more, and filmed video of Catania’s eels attacking various props.

“It’s very dramatic footage,” Driscoll says, “because the lights are going off and also the slow motion — you can really see how it climbs up. … One thing I was afraid about — I got to use the special Science Friday GoPro camera and we weren’t sure if that would survive 600 volts of electricity.”

As Catania studied the phenomenon of attacking electric eels further, he uncovered some interesting historical precedent.

In 1800, there is an account from German naturalist Alexander von Humboldt, who set out for an Amazonian lake to collect electric eels for his experiments, aided by a team of horses. As the animals entered the lake, Humboldt wrote the eels leapt up the legs of the horses to shock them. There were some 30 horses in the lake, and Humboldt said several of them were killed, likely after being stunned and then drowning. Humboldt wrote his account in 1807, and even then people didn’t believe it.

Now, Catania is able to prove the account was at least possibly true (and there’s video to illustrate it.)

—Elizabeth Shockman (originally published on PRI.org)

Segment Guests

Emily Driscoll

Emily Driscoll is a science documentary producer in New York, New York. Her production company is BonSci Films.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Electric eels, as their name suggests, are known for giving out powerful shocks. A six-foot eel can put out 600 volts. That’s about five times the amount of electricity coming from your wall socket at home. Wow.

But these eels are more than just a taser with a tail. The amount of volts an eels puts out is based on its surroundings. Emily Driscoll visited the lab of a researcher who is trying to figure out these shocking behaviors. And it’s the subject of our latest video. Emily Driscoll is a science documentary producer based here in New York. Always good to see you, Emily.

EMILY DRISCOLL: Great to be here.

IRA FLATOW: Eels use these shocks when they’re hunting for food or are against a predator, but there’s a certain behavior that this researcher is looking into. Tell us about that.

EMILY DRISCOLL: Yes, Ken Catania at Vanderbilt– he’s been studying eels for a couple of years now. And he’s looking at their behavior and how they use electricity. And eels– they can send out short pulses of electricity to sense their environment and see what prey is there. They can launch high volleys of electricity to paralyze their prey and eat them.

But Ken Catania– he found this new behavior on accident. He was moving one of his larger eels– a three-foot eel– from one tank to another. And he was using a net with a handle. And as he put the handle in the water, the eel turned around and started aggressively going towards him and trying to leap up the net and his handle.

IRA FLATOW: Out of the water?

EMILY DRISCOLL: Out of the water. So he made a note, hm, I need to study this.

IRA FLATOW: I’ll bet.

EMILY DRISCOLL: Because he had never seen that kind of behavior before.

IRA FLATOW: And so is there precedent for that?

EMILY DRISCOLL: There actually is–

IRA FLATOW: Eels leaping out of the water?

EMILY DRISCOLL: There actually is. Alexander Von Humboldt, in 1800– he is a very famous German naturalist explorer and scientist and he went on expeditions around the world. And he went to the Amazon because he wanted to collect some electric eels and he hadn’t had success collecting them before. So he got some local fishermen to help him and they said that they would fish with horses.

So they rounded up about 30 horses and they went into a muddy pool and all of this– horses in activity, again, kicking up all this mud– it scared the eels. And the eels acted out very aggressively and ended up coming up– and there was a five-foot eel there. The eel rose up, pressed its head against the belly of the horse, and shocked it.

IRA FLATOW: Oh. Wow. Scared the horse? Did it kill the horse?

EMILY DRISCOLL: This was a really major spectacle going on between these 30 horses and all these eels. And it ended up killing a couple of horses– probably stunning them and then they drowned. But it was just it was an incredible spectacle and then the eels were exhausted. So he was able to collect the eels. But even then– Humboldt wrote about this in 1807– and even 1807, people didn’t believe the account.

IRA FLATOW: Right. So he– the scientist you’re working with– found that account– he found the record of that.

EMILY DRISCOLL: Exactly. And he found– he decided to test this and he used some unique props to do it.

[FLATOW LAUGHS]

IRA FLATOW: Tell us what they were.

EMILY DRISCOLL: Well, yeah. It was kind of interesting to be in his lab and see all of his scientific equipment. He wanted to put something that would be a predator. So he used a crocodile head.

IRA FLATOW: A real crocodile head?

EMILY DRISCOLL: It was a fake crocodile head, but something that would be a stand in for a predator. And then he put it in the water and he filmed it. And he also put LEDs on the crocodiles.

And they would light up when there’s electricity given off by the eel. And he recorded it and he saw how the eel rose up and pressed itself against the crocodile. And it’s very dramatic footage because of the LED lights going off and also the slow motion. You can really see how the eel climbs up.

IRA FLATOW: Now, we have audio of what these shocks sounded like through your speakers. So let’s hear a little bit of that.

[CREAKING AND KNOCKING]

Wow. Were you scared at all when you were filming?

EMILY DRISCOLL: Well, one thing I was afraid about– I got to use the special Science Friday GoPro camera. And we weren’t sure how that would– if that would survive 600 volts of electricity. So we put that in the tank with the eel, and it actually was just fine– fantastic. And we really got some exciting footage showing how the eels eat because everything happens so quickly, you can barely see it. So you’re right in the tank with the eel. And we also filmed it in slow motion.

IRA FLATOW: And the camera survived OK.

EMILY DRISCOLL: It did.

IRA FLATOW: Wow. Wow. As always, Emily, an excellent, excellent video. This is a fun one to look at. And I’m sure it wasn’t that fun when Emily was worried about getting shocked there.

Emily Driscoll, a science documentary producer based here in New York. Thanks for joining us. And you can see her video– it’s a great one, as I say– at sciencefriday.com/eels.

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Meet the Producer

About Alexa Lim

Alexa Lim is a producer for Science Friday. Her favorite stories involve space, sound, and strange animal discoveries.

  • Gene Cost

    Interesting segment…..enjoyed!

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