Most people would do everything possible to avoid getting zapped by an electric eel. But lately, Kenneth Catania, a biologist at Vanderbilt University, has been willingly tempting one of these creatures to strike him.
Catania is not crazy, nor is he filming some newfangled reality TV show. In fact, he’s been offering up his own arm to the eels in the name of solving a math equation.
You see, last year Catania showed that eels can leap from the water to deliver their strike to a would-be predator. In that experiment, he relied on a fake human hand to endure the electrical attacks. But Catania wanted to measure the actual power of an eel’s zap, and a prosthetic wouldn’t do. To quantify a real eel-to-human electrical circuit, he’d need to measure the resistance of real human skin.
“Maybe I painted myself into a corner here, because I always tell my students to collect data rather than just making theoretical measurements,” says Catania, whose new study was published today in the journal Current Biology.
“After using an arm prop in the last paper, it just seemed kind of like destiny.”
“A Very Efficient Deterrent”
So, what does it feel like to get shocked by an electric eel?
Catania likens the experience to accidentally backing into an electric fence on a farm. “And it has a similar function,” he says, “in the sense that the shock is a very efficient deterrent.”
Electric eels have three special organs capable of creating rapid-fire waves of electricity—up to 150 to 200 pulses per second. The animals use these charges to sense the world around them, locate and stun prey, or send a would-be predator packing.
In order to quantify this mystical force, Catania created a tank that allowed a small electric eel to rear out of the water and strike his arm while his hand grasped an electricity-measuring handle. In this way, he was able to record data on exactly how much energy flowed out of the eel and through his arm.
Ironically, Catania had to perform the experiment upwards of 10 times, he says, because he kept forgetting to plug in a wire or flip on the camera. In the end, though, his persistence paid off.
For the relatively small, 15-inch electric eel used in the study, Catania found that the electrical current flowing through his arm peaked at 40 to 50 milliamps (mA). That’s quite a jolt: Other studies have shown that humans can sense and reflexively recoil from charges as low as 5 to 10 mA.
Fortunately, Catania doesn’t need to be shocked by a larger eel to estimate its strike. Using math, he figures the biggest, baddest eels out there can deliver a peak electric current of up to 250 mA—or roughly 8.5 times the wallop delivered by a TASER.
What’s more, Catania found that the leap itself matters. The higher the eel rears out of the water, the more electric current passes through the victim instead of back down into the water.
Amused and Impressed
This is why she says she was incredibly amused but also impressed to see Catania “sacrificing his own body” in an attempt to answer “fundamental questions about electric eel behavior that have really gone unanswered until now.”
“I think the electric eel brings out a child-like fascination in everyone,” says Traeger. “I find myself excited to see what Catania will come out with next.”