The Shocking Truth About Electric Animals

An elephantnose fish swims in the Congo River. Photograph by Reinhard Dirscherl, Alamy

Some animals are just plain shocking in that they’ve evolved the ability to detect naturally occurring electric fields, while others can produce their own electricity.

freshwater species of the weekIn a study published today in the journal Science, researchers have worked out how six different groups of electric fish evolved organs capable of generating electricity. All muscle cells have electrical potential, but in these six groups of fish, certain muscle cells evolved over millions of years into cells called electrocytes, which generate much higher voltages than ordinary muscle cells do. This enabled these electric fish, all native to the muddy Amazon River, to employ their active electric sense much like bats use echolocation: to detect obstacles and other animals in the dark.

Electric fish can electrically ‘illuminate’ their environs to detect objects that differ in their electric properties from the surrounding water,” says Gerhard von der Emde, a neuroethologist at the University of Bonn. They also produce electric signals to communicate with one another while attracting mates and marking their territory.

But fish aren’t the only electric animals on the block. Several other species detect or generate electricity for a variety of purposes.

1. Electric Eel

Despite its name and serpentine appearance, the electric eel is not an eel at all, but rather a type of electric fish. Like other electric fish, they’re nearly always producing low-voltage pulses to sense their environment. But they are more infamous for their ability to generate extremely high-voltage shocks to stun or kill prey and defend themselves.

Electric eels can grow to over eight feet (2.4 meters) long and weigh nearly 50 pounds (22.7 kilograms). An eel this size can emit a burst of over 600 volts, five times the voltage of a standard U.S. wall socket.

Human deaths from electric eel shocks are rare, but have occurred. Repeated shocks can cause respiratory and heart failure, and people have drowned after being stunned by electric eels.

2. Elephantnose Fish

First of all, that’s not its nose—it’s actually an elongated chin. The scientific term for this specialized organ is the Schnauzenorgan, and it’s covered in sensors attuned to detecting electric fields.

The elephantnose fish belongs to a group of electric fish native to Africa. Due to its poor eyesight, it must find food and navigate its surroundings by generating an electrical field through its tail. It then senses any changes to that field with its Schnauzenorgan.

The organ is so sensitive that the elephantnose fish can tell the difference between living and dead bugs buried up to 0.8 inches (two centimeters) in the seafloor. They can also use the Schnauzenorgan to determine distances and distinguish between materials, shapes, and sizes of objects.

Elephantnose fish also have an enormous brain relative to their body size, and von der Emde says the fish are very intelligent, easily learning new tasks and capable of understanding abstract concepts. “When ‘bored,’ they play with objects such as stones, air bubbles, or tubes that we put in their tanks,” he says.

Picture of a platypus
A platypus says hello. Photograph by Joel Sartore, National Geographic Creative

3. Platypus

The mystery of how platypuses catch their prey in murky water at night, with their eyes, ears, and nostrils closed, puzzled scientists for years. Then researchers discovered that, unlike any other land mammal, platypuses use the electrical impulses emitted by their prey to home in on a meal.

A platypus’ bill is covered in nearly 40,000 electricity sensors—or electroreceptors—arranged in a series of stripes, which helps them localize prey. All animals produce electric fields due to the activity of their nerves and muscles. So when the platypus digs in the bottom of streams with its bill, its electroreceptors detect these tiny currents, allowing it to tell living prey from inanimate objects.

4. Sharks

All sharks and rays can detect electric fields, thanks to the hundreds to thousands of tiny pores, filled with an electrically conductive jelly, that pepper their head.

Sharks primarily use their electric sense to find food. “Sharks can use other senses, like olfaction, to home in on prey and then do the final localization directed by their electric fields,” says David Bodznick, a biologist at Wesleyan University in Middletown, Connecticut. “It works well when prey is buried in the sand or at nighttime or in murky water.”

Hammerhead sharks use their heads like giant detectors, sweeping them over the seafloor to sense the electrical impulses of buried fish. “It may be that the big, broad head of the hammerhead allows it to more accurately triangulate the position of prey,” says Stephen Kajiura, a biologist at Florida Atlantic University in Boca Raton.

Sharks’ electrosense appears to be the most sensitive in the animal kingdom, capable of detecting voltage gradients as small as one billionth of a volt. It’s so sensitive, in fact, that scientists have trouble measuring it with even the most sophisticated instruments.

5. Electric Rays

Some rays, in addition to being able to detect electrical fields, can produce electricity. There are 69 species of electric rays—found in all the world’s oceans—and they range in size from three feet (0.9 meters) across to about the size of a dinner plate. The voltage they produce varies with their size, with smaller rays generating less than ten volts and larger ones capable of producing up to 220 volts.

Some species, like the Pacific electric ray, use their electricity to stun prey. But not all of them employ electricity when hunting. While studying the lesser electric ray, Kajiura found that even given multiple opportunities, these rays never used their electric organ to stun their prey. “When they were threatened by a predator, that’s when they zapped, and they zapped like crazy,” he says. Rays may also use their electric sense to detect predators, find mates, and communicate with one another.

6. Oriental Hornet

The Oriental hornet is a truly solar-powered animal: Its exoskeleton is capable of transforming solar energy into electricity.

Unlike most hornets that avoid activity during the hottest part of the day, Oriental hornets are out in force when the sun is most intense. The brown-and-yellow-striped insects do this to harvest the sun’s energy.

The brown stripes trap sunlight, while the yellow stripes convert the sunlight into electricity.

What do Oriental hornets do with this homegrown electricity? Experts aren’t sure, but some research finds the electricity could help the insects create enzymes that aid in their metabolism. It could also help keep the hornets comfortable even at high temperatures; they can stay cool by converting heat energy into electricity, which they can then store and convert back into heat when it cools down.

Alternatively, the electricity might give their wing muscles an energy boost. Shining ultraviolet light on anesthetized hornets made them wake up faster and immediately fly away, as if it recharged their batteries.

Follow Mary Bates on Twitter and Facebook.

Mary Bates is a freelance science writer living in Boston. She has a PhD in psychology from Brown University where she studied bat echolocation. You can visit her website at www.marybateswriter.com and follow her on Twitter at @mebwriter.
  • Andrew Allison

    “An eel this size can emit a burst of over 600 volts, five times the power of a standard U.S. wall socket.” Good Grief! Doesn’t anybody on the NGS editorial staff know the difference between voltage and power? The typical electrostatic shock results from much higher voltage but only has the power to shock.

    • Thanks for your comment. You’re absolutely right; the text has been changed to say “voltage” instead of “power.”

  • Derrick

    Hi Mary, there’s a discrepancy between the account by this article here (http://news.nationalgeographic.com/news/2010/12/101221-solar-power-hornet-science-animals/?rptregcta=reg_free_np&rptregcampaign=20131016_rw_membership_r2p_intl_sm_w#) and yours. Does the brown pigment of the Oriental Hornet trap light? Or does the yellow pigment does that instead?

  • Darwin

    Interesting read! However, I have to second the previous comment about voltage vs power. It sticks out like a sore thumb and ruins your credibility with anybody who understands even the first thing about electricity.

  • Sour Dough

    I’m an aquarist and am very familiar with the Elephantnose fish. They are fascinating fish, though not very social with other species. We had to put a bunch of young tiger oscars in with one once because we didn’t have their tank ready yet. Oscars are a bit “curious”, and they started hanging around the elephantnose more and more, and they bothered the elephantnose enough that it hit them with its defensive electric shock and all of the oscars immediately raced to the corners of the tank. Someone noticed this and started laughing, not believing what they saw. After about 5 minutes, the oscars forgot what happened and started slowly swimming around and getting closer to the elephantnose again. After about 5 minutes they were again all around the elephantnose fish, as oscars aren’t very “bright”, and the elephantnose again let them have it and the oscars swam screaming for the corners of the tank again. this time we all saw it and couldn’t stop laughing. This wasn’t healthy at all for the elephantnose because of the stress it puts on them, and we hastened our work getting the oscar’s new tank ready. The elephantnose let them have it two or three more times before we could get the out of there, and it’s something I never have forgotten about “dipolar fish”.

    I noticed that this article left out Black Ghost Knifefish? They are another in a family of dipolar electric fish that use electricity to locate food and for communication: http://en.wikipedia.org/wiki/Black_ghost_knifefish

    • Thank you for your comment! Unfortunately, I didn’t have enough space to get into the intelligence of elephantnose fish (Dr. von der Emde commented on this, as well). There are many electric animals that I didn’t mention. Knifefish are a type of electric fish like the ones analyzed for the recent paper on electric organ develpoment that I discuss in the introduction. They do use electricity for electrolocation and communication.

  • Ima Ryma

    The oriental hornet is
    The first animal to be found
    To mind its solar power biz,
    Energizing its body round.
    When the sun is at most intense,
    The oriental hornets do
    Orient their in force presense,
    Using yellow and brown stripes to
    Make homegrown electricity.
    Why bugs are getting such a charge
    Has given humans cause to talk
    Why some non humans, by and large,
    Keep giving humans such a shock.

    The oriental hornets’ nest
    Has science all abuzz impressed.

  • Douglas

    A standard (US) wall socket can produce 15 amps of current at 120 volts (a power of 1,800 watts) for an indefinite period of time. An electric eel, in contrast, can produce a brief burst of just 1 ampere of current at 600 volts (a power of 600 watts) lasting no more than 2 milliseconds per burst.
    This is an impressive and unusual capability, and it is certainly sufficient to deliver a nasty shock that will stun prey and drive away predators. To say, however, that such a shock has “five times the power of a standard U.S. wall socket” is simply incorrect. The eel’s maximum output is only one-third the power, and one-fifteenth the current, of a standard US wall outlet. And unlike a wall outlet, the very short duration of the eel’s current burst means that it is very unlikely to produce fibrillation or burns in an adult human, even when repeated. This is one reason why human deaths from electric eel shock are so rare, and why, when they do occur, the cause of death is typically drowning, rather than heart, brain or respiratory failure.

  • Jade

    National Geographic is one of the most credible magazines. This article about electric animals was magnificent. The facts in the article seemed very credible and I even shared some facts with my friends. Electric animals are very interesting because they possess so much power in those little bodies. The article stated “A platypus’ bill is covered in nearly 40,000 electricity sensors” this is very shocking because I didn’t think there was anything special about platypuses.

    People don’t always take an interest in stuff like this because to them it’s probably weird and boring but everybody is entitled to their own opinion. This article is very well put together and I would enjoy learning some more about these types of animals or similar types of animals. If someone could incorporate saving aquatic animals and the interesting facts about them into one article that would be incredible. You could be informed about aquatic animals and persuaded to save them at the same time. Aquatic animals play a big part in our life because they provide jobs, the ability to research other species besides ourselves, etc.

  • Eunice Mhlungu

    We have several electric fish in Africa. A cat fish very common in the Zambezi river as well as the ‘bottle nose and bulldog similar to the elephantnose pictured above. These fish can give you a nasty shock. The fish are very fatty and maybe part of the reason that they can electrocute their prey.

  • OmAr Wollongong

    Voltage doesn’t kill you . It’s the amp that will

  • Demitri

    “Some animals are just plain shocking in that they’ve evolved the ability…” – I love the way Bates opens this article! Mary, in order to work for Nat Geo are you expected to state the word “evolution” somewhere, somehow, in every article you write or video you produce? One website search says word evolution/evolved appears on your nature website like 30,000 times!!! Glory! Does this vestige of Victorianism really need to be defended to the extent of brainwashing your readership? Please NG, give us some room to think, examine, and draw our own conclusions about how this wonderful and sophisticated world of ours came about.

    • Name

      Their opinion. They didn’t force you to read it. If you wanna believe the Earth is a few thousand years old, so be it. But don’t act like a child.

  • Demitri

    “Your comment is awaiting moderation”

    i.e. Your comment is awaiting censorship

    So long, freedom of speech! 🙂

    • Name

      I.e your comment WAS awaiting security checks.

      So much for that rebuttal. Get roasted.

  • Drew

    It’s amazing how so many people find Nat Geo so credible. If you take the time to research their articles you will find them to be very flawed. For example, the author says, “all native to the muddy Amazon River. ” 10 minutes in your local library will prove that these types of fish aren’t native only to that river in South America or even to that continent alone!! If your are going to write for a recognized nature magazine your facts should be accurate. And if you are looking for a reliable source of information, avoid Nat Geo!!

  • gourish

    how much volt can aquarium fish withstand

  • lu

    what about a jelly fish

  • Grace king

    Yes what about jellyfish?

  • Olabanjialadejana

    Its real. I got shocked by it today.

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