Analyze This: Electric eels’ zaps are more powerful than a TASER | Science News for Students

Analyze This: Electric eels’ zaps are more powerful than a TASER

A scientist measured the strength of the eel’s attack by letting himself get zapped
Jan 24, 2018 — 6:30 am EST
eel zap
The electric eel that zapped biologist Kenneth Catania was small, but the shock it delivered is similar to one supplied by an electric fence.
K. Catania/Current Biology 2017

Electric eels have captured the attention of scientists — and the public — for centuries. These aquatic animals can deliver a jolt of electricity to track and tucker out their prey. They also can use that shock as a defense mechanism. When an eel feels threatened, it leaps out of the water and zaps a perceived predator. Now a scientist has deliberately subjected himself to such an attack. His goal: to get a better picture of the fish’s shocking prowess.

Kenneth Catania is a biologist at Vanderbilt University in Nashville, Tenn. He wanted to know how strong of a shock an electric eel could deliver. So he stuck his arm in a tank and let a small eel zap him. At its strongest, the fish delivered a 40- to 50-milliampere current into his arm. It takes only 5 to 10 milliamperes of electricity for humans to lose control of their muscles and let go of the object that is shocking them. So it’s no wonder Catania involuntarily pulled his arm away with each electrical jolt this eel delivered. He presented his findings September 14 in Current Biology.

His test subject was just 40 centimeters (16 inches) long. Based on his tests with this fish, Catania has now estimated how much electricity someone might receive from a run in with an eel 1.8 meters (5 feet 10 inches) long. That’s the average length of an adult one of these eels living in the Amazon of South America. A human could receive a zap of 0.25 ampere, or 63 watts, he now calculates. That’s some 8.5 times more than a police-issued TASER gun. Enough to make a heart beat uncontrollably, this could kill a human.

eel current graph
The current an electric eel sent into the arm of a researcher got stronger as the animal reached out of the water to attack.
K. Catania/Current Biology 2017

Data Dive: 

  1. Roughly how many milliseconds worth of data are displayed on the x-axis in this graph?
  2. According to the graph, what is the approximate electric current measured at 125 milliseconds into the recording? Be sure to use appropriate units in your response. 
  3. How many milliamperes are in one ampere? How many centiamperes are in one ampere? Convert your answer from question 2 to amperes, centiamperes and kiloamperes (write your answer in scientific notation). 
  4. If you had to change the units used on the y-axis to either centiamperes or kiloamperes, which would you choose and why?
  5. Critique the graph. What would you do differently? What information do you feel could be added to the graph to make it more useful or easier to understand?

Analyze This! explores science through data, graphs, visualizations and more. Have a comment or a suggestion for a future post? Send an email to

Power Words

(for more about Power Words, click here)

ampere     A rate of electrical current equal to one coulomb per second. A milliampere is a thousandth of an ampere.

aquatic     An adjective that refers to water.

axis     (in mathematics) An axis is a line to the side or bottom of a graph; it is labeled to explain the graph’s meaning and the units of measurement.

biology     The study of living things. The scientists who study them are known as biologists.

current     A fluid — such as of water or air — that moves in a recognizable direction. (in electricity) The flow of electricity or the amount of electricity moving through some point over a particular period of time.

defense     (in biology) A natural protective action taken or chemical response that occurs when a species confront predators or agents that might harm it. (adj. defensive)

eel     A fish with a snake-like body and no scales. Many migrate from freshwater to salt water when it’s time to spawn.

electric current     A flow of electric charge — electricity — usually from the movement of negatively charged particles, called electrons.

electricity     A flow of charge, usually from the movement of negatively charged particles, called electrons.

mechanism     The steps or process by which something happens or “works.” It may be the spring that pops something from one hole into another. It could be the squeezing of the heart muscle that pumps blood throughout the body. It could be the friction (with the road and air) that slows down the speed of a coasting car. Researchers often look for the mechanism behind actions and reactions to understand how something functions.

millisecond     A thousandth of a second.

predator    (adjective: predatory) A creature that preys on other animals for most or all of its food.

prey     (n.) Animal species eaten by others. (v.) To attack and eat another species.

TASER     A brand-name of version of a “conducted electrical weapon” used by police, the military, prisons, security guards and others. It sends out electrodes that deliver a stunning discharge of electricity into a person to incapacitate them. Such devices are popularly referred to as stun guns.

watt     A measure of the rate of energy use, flux (or flow) or production. It is equivalent to one joule per second. It describes the rate of energy converted from one form to another — or moved — per unit of time. For instance, a kilowatt is 1,000 watts, and household energy use is typically measured and quantified in terms of kilowatt-hours, or the number of kilowatts used per hour.

Further Reading

Journal: K.C. Catania. Power Transfer to a Human during an Electric Eel’s Shocking Leap. Current Biology. Published online September 14, 2017. doi: 10.1016/j.cub.2017.08.034.

Source Story (Science News): A researcher reveals the shocking truth about electric eels