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  • The five senses tell us everything we need to know about our surroundings.

  • With smell, taste, touch, sight, and hearing, we're able to understand the makeup of everything around us.

  • But, for some animals, there's a sixth sense, and it's practically invisible.

  • No, it's not the force or whatever mystical power you're thinking of.

  • It's an uncanny ability to sense disturbances in electric currents.

  • This is called electroreception.

  • So in all living organisms there's a natural voltage created by the difference in the concentration

  • of ions within the body, compared to the outside environment.

  • This is something that plants and animals need to maintain homeostasis.

  • Any muscular movement can create a small electrical current, which includes your muscle movements

  • and mine.

  • It's actually what's being picked up from a heartbeat to make this.

  • Now there are two ways that animals use electro reception.

  • They either use their own electric currents to sense how those currents bounce back to

  • interpret their surroundings, or they pick up the electric currents already being produced

  • by other animals to locate prey.

  • Electroreception is most common in some amphibians and fish,

  • because salt water is a fantastic conductor of electricity, especially compared to air.

  • But bees have also been found to use electric fields to assess pollen in flowers.

  • And some mammals have the sixth sense too,

  • notably the platypus, echidna, and the Guiana dolphin.

  • But sharks are truly some of the best at using electroreception because they're so sensitive.

  • In addition to their strong muscles, aerodynamic shape and specialized fins, this sixth sense

  • helps sharks to be the talented hunters they are famous for.

  • Great white sharks are so sensitive, they can detect 1,000,000th

  • of a volt in a milliliter of seawater, and maybe even less than that.

  • According to a study by the University of Birmingham, this is like connecting a double

  • A battery to a pole dipped off the coast of New York, with a pole off the coast of Florida.

  • Theoretically, a shark swimming between those two points could actually tell when a battery

  • is switched on or off, which is wild.

  • That's a sensitivity better than most state-of-the-art equipment used by electrical engineers.

  • So how do they do it?

  • It's all due to a specialized sensory organ in sharks and rays called the ampullae of

  • Lorenzini named after Italian physician Stephano Lorenzini who discovered it back in

  • 1678.

  • If you look underneath the shark's head you'll see an array of practically symmetrical dots.

  • These are pores connecting jelly-filled tubes to bulb-like structures in the shark's head

  • called ampullae.

  • So picture fish swimming through the ocean, naturally giving off electric currents, because

  • we all do that of course.

  • As the shark swims through the water, these electric fields travel

  • into the pores under its head through the tubes to the ampullae.

  • These tiny hairs read the signals and use a network of nerves to send a message to the

  • brain.

  • This gives the shark exact dimensions and location of the fish, helping the shark catch

  • and eat it.

  • It's fascinating because if you think about it, there's so much electrical noise going

  • on in the ocean all at once.

  • Besides all the animal and plant life, the salinity, temperature, water movement and acidity, all

  • produce a voltage that a shark can pick up.

  • So to be able to distinguish prey amid all the noise is beyond impressive.

  • In practice, a shark will use all of its senses to hunt.

  • From far away a shark would smell and hear its prey.

  • Vision and taste would kick in upon closer range.

  • But during the final phase of an attack,

  • electroreception precisely locates the prey and tells the shark how to orient

  • its jaws.

  • This is why when I dove with tiger sharks in the Bahamas, they only turned away from

  • me once they were in extremely close range.

  • I had actually just gently kind of put my hand on their, you know the tip of their nose

  • or their muzzle.

  • And just redirect them, so they weren't about to just bump their face into mine.

  • It was unreal during those dives I was just sitting at the bottom of the sandbar just

  • redirecting sharks.

  • It was like a little traffic conductor.

  • Just, just moving sharks out of the way, and it was pure magic.

  • Beyond hunting prey,

  • scientists believe that sharks also use electroreception to sense potential predators,

  • and find mates.

  • Research is also being done on how electric currents could repel sharks from fishing hooks.

  • This could help protect sharks against dangerous fishing techniques that kill sharks as bycatch

  • when fishermen go after other fish.

  • This research could also help find a way to repel sharks from swimmers and surfers.

  • Of course over the years, sharks have gotten a bad reputation that they really don't deserve.

  • Sharks are incredibly intelligent and beautiful animals.

  • Each year there are only about 140 shark attacks on humans, and many of those are provoked

  • by spear fishers or humans interacting with sharks in their natural habitat in an inappropriate

  • way.

  • Compare that to the nearly 100 million sharks killed by humans, each year.

  • I think people are so fearful of sharks for a couple reasons anytime you have a big mega

  • predator, there's a fear associated with that.

  • I also think there's a fear, that's secondary to media, and a lot of this comes from the

  • movie Jaws, which is a phenomenal movie, but it created a lot of fear for people of sharks.

  • And then of course, anytime there's a shark attack the whole world hears about it.

  • I mean they look fierce, they are fierce, their teeth are different, they're made of cartilage

  • and all their adaptations are so fascinating to me and they really are some of the most beautiful

  • animals on the planet.

  • Thanks for watching Seeker's new series Tusks to Tails, I'm Evan Antin and I hope you enjoyed

  • this video.

  • If there's an animal you want us to cover, leave us a comment.

  • See you next time!

The five senses tell us everything we need to know about our surroundings.

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B2 shark prey electric sixth sense sense electrical

How Sharks Use Electricity To Sense Prey

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    林宜悉 posted on 2020/12/22
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