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!