[♪ INTRO]
We owe a lot to our senses.
Whether it’s hearing, sight, smell, taste, or touch — whatever combination we have
allows us to experience the world in pretty exquisite detail.
But some animal senses are so much more acute than ours
that they’re basically superpowers.
And we’re not just talking dog whistles and eagle-eyed vision.
From animals that can taste with their whole bodies to those with incredible
super-smell, the animal kingdom gets a whole lot more extreme —
and more fascinating. Like in these five examples.
For context, biologically speaking,
a sensory system is a group of specialized cells tuned to a certain type of signal.
When they get the signal, they fire off a nerve impulse,
and that causes some kind of response.
For vision, those specialized cells are called photoreceptors.
Humans have four types of them, including three that contribute to color vision,
and each is tuned to a different range of light waves.
Our brains can decode the signals from these cells
to discern millions of wavelengths, which we then perceive as colors.
But our eyes are far from the best. Other animals can see more colors,
in lower light, or with more detail.
And when it comes to cool eye tricks, the mantis shrimp leaves everyone in the dust.
This aquatic creature has the most complex eyes of any animal.
Depending on the species,
they can have between 16 and 21 types of photoreceptors!
Most are tuned to narrow bands of wavelengths,
from deep red to far ultraviolet—including wavelengths that are invisible to us.
But that doesn’t mean they can discern more distinct colors than we can.
Researchers hypothesize that they can probably recognize far fewer —
possibly just one color per type of photoreceptor.
But they can also process color information really fast.
See, for us, color vision hinges on decoding that happens in the brain,
and this takes a little time.
But in mantis shrimp, color perception happens right in the eye.
So, they can react to the situation more quickly.
This speed is important for the mantis shrimp’s dynamic, super-competitive lifestyle,
which involves lots of flamboyant signaling, fighting, and fast-action hunting.
But speedy color vision isn’t their only trick. They can also see polarized light.
Polarized light happens when light waves all vibrate in the same plane —
like, when they’re all oriented up and down.
This is in contrast to regular light,
which is made of waves vibrating in all orientations.
To us, polarized light doesn’t really look any different from regular light.
But some animals, like mantis shrimp, can see it,
and they use it to glean important information.
Not only that, but mantis shrimp are the only animal known
to be able to perceive circular polarized light.
That’s polarized light that also spirals in a clockwise or counterclockwise direction.
They even have areas on parts of their bodies that reflect this strange light pattern!
That may help them communicate with each other or identify mates.
And newer evidence suggests that their complex visual system
may also help them learn and remember information about their surroundings.
Next, in stark contrast to mantis shrimp, the star-nosed mole is practically blind.
But vision isn’t very important for it anyhow,
since it spends most of its time in dark underground tunnels.
Plus, it has a super-sense that more than makes up for its poor eyesight.
Maybe unsurprisingly, it has to do with its nose.
Which is so distinct, it gives the star-nosed mole its name.
But their star-shaped snout isn’t so much for smelling.
In fact, its pink, fleshy appendages don’t have smell receptors at all.
Instead, they’re covered in mechanoreceptors.
Mechanoreceptors respond to physical changes.
So, when something stretches or pushes on them, they fire off a nerve signal.
When there’s a bunch of them spread across an area, like your fingertips,
they can gather information about features like shape, texture, and size.
And overall, something like your fingertip is pretty sensitive.
But this mole’s centimeter-wide star packs about five times more sensing power
than you have in your entire hand.
In fact, it may be the most sensitive touch organ in any mammal.
And it gives the star-nosed mole unmatched precision and speed. Like, officially.
The Guinness Book of World Records has named it the world’s fastest eater,
in the mammal category.
These little animals are voracious predators,
and they use their star to forage for invertebrates on their damp tunnel walls.
Their nose’s super sensitivity lets it find the tiniest prey—
ones that are too small for other predators to bother with.
But on the flip side, because their food is so small,
they have to find a lot of it. And here, too, the star delivers.
As a mole forages, it touches its star to up to 13 places per second.
And it’s so good at collecting information about things like size and texture, that it can
decide within about 25 thousandths of a second whether something is edible.
It’s also helpful that the mole’s food-finding apparatus
is optimally located right by its mouth, and this likely adds to the speed.
In a simulated tunnel experiment,
one mole found and consumed 8 pieces of food in just 1.8 seconds!
Another animal that uses super-sensitive touch to hunt is the harbor seal—
but in a very different way.
Seals are pinnipeds—a group that also includes
walruses and eared seals, like sea lions.
And these animals are known for having extraordinarily sensitive whiskers.
The base of each whisker is packed with mechanoreceptors.
And compared to other mammals like your cat,
pinnipeds have about ten times more nerve endings per whisker.
That makes them sensitive to the tiniest movements.
And sort of how like people use their fingertips, pinnipeds can pass their whiskers
over an object to quickly and accurately sense its size, shape, and texture.
Walruses, for example, use their whisker touch to find edible items on the seafloor.
But most true seals, like harbor seals, take it up a notch.
They can use their whiskers to sense and follow trails of water disturbances
that other animals or objects leave behind.
Scientists think this helps them hunt for their main food source:
fish that swim in the water column.
And their unusual whisker shape makes them uniquely well-suited to this task.
Other animals, even other pinnipeds, have smooth, cylindrical whiskers.
But true seals have flattened, wavy-looking or wiggly-looking whiskers.
A 2020 study showed that this shape reduces drag in the water
and reduces whisker vibrations as the seal swims.
Since there’s little interference from the seal’s own movements,
it’s more sensitive to the trails of other objects.
And seals can extract impressive details from these fleeting trails,
including the size and shape of the object that left it and the direction it was moving.
Even after the thing that made it has moved tens of meters away.
In other words, never play Marco Polo with a harbor seal.
Next up are catfish.
Catfish are bottom-dwellers that typically live in dark, murky places. And although
their eyesight is decent, their super-tasting ability is what helps them find food.
Compared to what we can do, it’s also a little disturbing.
So, taste relies on chemoreceptors—
sensors that are activated when they bind to certain molecules, or chemicals.
And while our taste receptors live mostly in our mouths,
some animals have them in weird places.
Like, flies and butterflies can taste with their feet,
and octopuses taste with their tentacles.
But catfish can taste with their entire bodies.
Basically, they can taste anything that touches their skin,
including water that’s recently passed over something that they might want to eat.
But instead of responding to sweet, sour, or salty tastes,
they’re highly sensitive to certain amino acids.
Amino acids are the building blocks of proteins, so they’re found in all living things.
But the key here is that these molecules are released in high concentrations
by catfish’s favorite food: aquatic invertebrates.
Now, we can taste amino acids too, but catfish can sense them
at concentrations 100,000 to one million times lower.
And because their sense of taste is spread around,
they can even tell what direction a taste is coming from and hone in on it.
The taste receptors are more concentrated in certain places, though— like the fronts
of their fins, which helps the catfish pick up on taste trails as they swim.
And they’re especially dense on the fleshy,
whisker-like things around their mouths, called barbels.
So, as catfish forage for food, they brush their barbels
along muddy stream beds—or, for marine species, the ocean floor.
And when the signal is strong enough, the taste of amino acids
can make them start snapping their jaws at the surrounding water.
But that’s not the only unusual sensing ability that sets catfish apart.
In a 2014 study, researchers found that at least one species
can sense tiny decreases in water pH, or acidity.
It’s not yet clear if this is a function of their taste buds,
but it fires up the same nerves.
Either way, pH-sensing appears to help them find tasty, little worms—
since when the worms exhale carbon dioxide,
it combines with the water nearby to make carbonic acid.
Our final animal is bears, known for their super-smell.
Smell uses chemoreceptors, kind of like taste.
But these receptors bond to molecules that move through the air, specifically.
Now, considering that dogs can sniff out things like drugs, money, and even cancer,
it’s not surprising that humans aren’t going to win
any awards in the smell department.
But bears are especially impressive.
Like other animals with keen noses,
they just have more real estate dedicated to sensing smell.
In fact, compared to us, some bear species have five times more brain space
dedicated to smell, and about 100 times more area inside their noses.
Their sense of smell is not only keen but also remarkable for its range—
a distance that’s measured in kilometers.
In fact, the range is so great that it’s really hard to measure
exactly how far it extends.
Long-distance smell is useful because most bear species roam over large areas,
and it keeps them up-to-date about what’s going on around them.
Like, it can help them track their kids, sense potential mates, and sniff out food.
And lots of bear species seem to have this gift—
as a fair number of backpackers will tell you.
Like, in Yosemite National Park, black bears can sniff out food hidden in a car—
even crumbs and food residues. And then rip the car apart to get it.
And polar bears? They can pick up scents on the wind
and track them to seal breathing holes up to three kilometers away.
Bears’ keen noses may also help them communicate with each other
through scents left behind in their footprints.
Like, male brown bears have a certain way of grinding their feet into the soil when
they really want to leave their scent behind and let females know they’re available.
And pandas can smell 120-day-old scents left behind by other bears.
Which is just, well, humbling.
So, we humans like to think we’re the best
because of our big brains and ingenuity—and those are pretty great!
But it’s also worth sitting back and just admiring how other animals
get to experience the world, too.
Because there’s a lot to smell, taste, hear, and see out there, and sometimes,
the only way we can learn about it is by watching the rest of the animal kingdom.
This episode of SciShow goes out to our patrons on Patreon!
You might not have a star-shaped snout or be able to taste things
with your entire bodies, but we still think you’re pretty incredible.
Thanks for supporting free science education on the internet—
we couldn’t do this without you.
If you’re not a patron, thank you for supporting us by watching the show!
If you want to learn more about our Patreon,
you can also go to Patreon.com/SciShow.
[♪ OUTRO]