(upbeat music) (bird calls)
(tiger growls)
(insects chirp)
(wind whistles)
Anyone fascinated by the natural world
has probably wondered why some animals
have such strange-looking sense organs.
(insects chirp)
(elephant rumbles)
The elephant with its
huge ears, (elephant trumpets)
the antennae of a butterfly,
which up-close look like feathers,
the snake with its (snake hisses)
split tongue.
And what about less obvious enhancements,
like the sensory cells on a crocodile's skin?
Surely these evolutionary traits aren't just for decoration.
(suspenseful music)
In fact, the size, shape, and location
of these animal sense organs is all for a purpose
and just like us, animals rely on their senses
to communicate with each other, find their way around,
stay safe, (wolf howls)
and most importantly, to find food.
When you see how superior some animal senses are
compared to those of humans,
you might wonder how we ever managed
to stay on top of the food chain.
"Animal Super Senses."
You won't believe what's possible.
(gentle music)
(dramatic music)
(birds calls) Welcome to
"Animal Super Senses,"
the show that plugs you in
to how animals experience the world,
often with sharper and more-evolved senses
than the one species who likes to think of itself
as the top of the food chain.
(dramatic music)
That would be us, of course.
(dramatic music continues)
While all life began in the oceans,
(water rushes) (whale splashes)
human beings now rely on technology
to navigate the seven seas.
Left to our own devices,
(dramatic music)
we're like the proverbial fish out of water,
only the other way around.
Once underwater, with light diminished,
our vision becomes blurred.
Our hearing becomes muffled and distorted,
and our sense of smell is rendered completely useless.
(upbeat music)
Now compare that, for example, to that renowned predator,
the great white shark.
(suspenseful music)
This elegant killing machine is perfectly attuned
to every sight, sound, scent,
chemical and electrical signal
of its marine environment.
(suspenseful music)
We'll pay a slightly nervous visit to the great white
a little later in the episode.
(suspenseful music)
But first, listening carefully?
Because the sense of hearing enters a whole nother dimension
when applied to
creatures of the deep. (whale sings)
Hearing is critical for animals
such as the sperm or humpback whale.
(whale sings)
(whale splashes)
For one thing, light fractures and weakens underwater,
so vision becomes a less important tool for survival.
(whales sing) (water ripples)
Sound, however, travels further in the water
than in the air.
So for whales, it's critically important
as a way of communicating,
most famously as in the song of the humpback whale.
(whales sing) (water ripples)
Humpback whales are members of the cetacean family
which includes whales, dolphins, and porpoises,
all of which have well-developed senses of hearing.
(dolphin clicks)
(upbeat music)
(water rushes and ripples)
In the case of this humpback whale,
its outer ears have very small opening
that closes once under water.
Instead it picks up on waterborne vibrations
through bones in its head,
good vibrations that ultimately reach
its middle and inner ears.
(upbeat music)
(electronic beeping)
(sonar beeps)
Fascinatingly, the ancestors of the whale
actually walked on land.
Pakicetidae or Pakistani whales
lived on the shores of the Indian sub-continent
and began to diversify,
making for the water some 53 million years ago,
give or take.
More about them and their ancestors later in the show.
(water ripples) (whales sing)
Meanwhile, to be a little bit more specific
about what hearing is,
(whales sing)
it's the ability to sense sonic vibrations, sound,
and what is known as vibrational stimuli.
They pretty much amount to the same thing underwater.
The scene now is the Coral Triangle.
This is the area of tropical marine waters
around Malaysia, the Philippines, Indonesia, and East Timor,
a tropical paradise in many regards
sometimes known as the Amazon of the seas,
(gentle music)
(waves whoosh)
(water ripples)
(gentle music)
but one that the World Wildlife Foundation
is keeping a close eye on
to ensure human activity
doesn't spoil this particular paradise too.
(gentle music)
Among the countless species
that call the Coral Triangle home,
you'll find plenty of cephalopods.
Plenty of what?
Cephalopods, like cuttlefish and this octopus,
are invertebrate, spineless mollusks
with generally large heads and symmetrical bodies.
(gentle music)
For over a century, there's been a debate
as to whether these creatures are capable of hearing.
(gentle music)
But the consensus seems now to be that they can,
either by something called the statocyst organ,
a fluid-filled sac lined with sensory hairs
that also helps them to maintain balance,
or they can hear via lateral lines
similar to that found in fish,
visible lines on the fish's body
comprised of sense organs
which detect pressures and vibrations.
(gentle music)
(water ripples)
Now, of course, there are more fish
than you can shake a million fish sticks at
in the Coral Triangle.
And chances are, they'd hear you
when you shook those sticks at them
because as any goldfish owner can tell you,
at any kind of threatening sound
a fish will curl into a tight C shape
and head in the opposite direction.
(water ripples)
So whether in a goldfish bowl or the Coral Triangle,
we know that fish can hear,
but believe it or not,
scientists are somewhat divided as to how.
(water ripples)
Here are the two main theories.
The bodies of fish have about the same density as water,
which means that sound passes through their bodies.
But fish have bones in their inner ear
which are called otoliths.
These bones are denser
than both the water and the fish's body.
This means these bones move at a slower pace
than the rest of the fish's body
and also the speed of the sound waves.
(water ripples)
The upshot of this is that the difference in speed
between the otolith bones and the rest of the fish's body
ruffles the hairy sensor cells located in its inner ear.
This differential movement
is interrupted by the brain as sound.
(percussive music)
Then there are the lateral lines we mentioned before.
These are essentially a set of tubes
located just under the fish's,
or in this case, the shark's body.
Water enters these tubes through the pores of the skin.
The tubes are lined with hair cells
which are connected in turn to sensory nerves.
(percussive music ends)
When anything gets close to a shark,
the water running through the lateral lines
moves to and fro.
(eerie music)
(dramatic chord)
This stimulates the sensory cells,
which alerts the animal to whatever prey or predators
may be in the vicinity.
(dramatic music)
(water splashes)
(dramatic music)
(water ripples)
When we talk about animal super senses,
perhaps no animal fits the bill more than the shark.
In the popular imagination,
we imagine them like this blacktip shark
moving stealthily through the water
and then seizing their prey without mercy,
relentless and unstoppable.
(dramatic music)
And that's about the size of it.
(dramatic music)
Their senses are also supremely well adjusted
to make them effective underwater predators.
For one thing, they have
a particularly acute sense of smell.
Unlike for example, human beings,
sharks have separate and distinct openings
for breathing and for smelling.
The gills on the side of their heads
are for breathing only
and serve to capture oxygen in the water.
(dramatic music)
(water ripples)
Meanwhile, two nostrils to the front of their heads
pull water into a nasal chamber,
specifically dedicated to detecting smells.
Perhaps one reason a shark's nose works so well
is because it doesn't have to do anything else.
Breathing is accomplished with their gills.
And a shark's sense of smell
is not in any way connected to its mouth.
(dramatic music)
But a shark's sensory arsenal doesn't end there.
Sharks come with a unique sense organ as standard equipment,
something called the of ampullae of Lorenzini.
They were first described back in the 17th century
by one Stefano Lorenzini.
They consist of small clusters
of electrically sensitive receptor cells
found just under the skin.
These are connected to the water
by pores on the shark's snout and head.
(dramatic music)
What the ampullae of Lorenzini do for the shark
is to outfit it with electro-reception.
In a nutshell, electro-reception means
the shark can sense the bioelectric fields
generated by other animals
and use it to locate them.
(dramatic music)
And hey, you'd expect the ultimate predator
to know where its next meal is coming from, right?
(dramatic music)
Blacktip sharks like these
share the waters of the Coral Triangle
with a cetacean known for its hearty appetite,
the sperm whale.
(whale breathes)
(gentle music)
And also with the sperm whale's distant cousin,
the dolphin, a marine mammal
who's no slouch in the appetite department either.
They may be enthusiastic eaters,
but they don't exactly enjoy their food
in any way we might understand.
(water ripples)
You see, just about all vertebrates
enjoy five primary tastes:
sweet, salty, sour, bitter, and umami,
except, that is, for cetaceans such as dolphins and whales.
(gentle music)
(water ripples)
(whale splashes)
New research has revealed,
at some point in their evolutionary journey,
they lost the ability to perceive anything but salt.
(gentle music)
Scientists believe this took place
between 53 million years ago,
at the point when whale ancestors, pakicetidae,
took to the seas,
and 36 million years ago,
when they split into two groups,
toothed and baleen whales.
(whale breathes)
Then again, if you swallow your food instead of chewing it,
perhaps not having a sense of taste isn't such a great loss.
(gentle music)
(water ripples)
(whale splashes)
(birds call)
What about underwater vision?
All you need to do is hold your head underwater
for a few seconds,
and you'll see that our eyes are not adapted
for vision underwater.
No, they've evolved for viewing in air.
Everything is a blur underwater, right?
That's because light rays bend
when they travel from one medium to another,
from air to water.
Water refracts light at roughly the same degree
as the cornea of the human eye,
which effectively eliminates our ability to focus.
(water ripples)
(gentle music)
Fish eyes are more spherical in shape,
allowing them to focus under the waves.
In many cases, they're also sensitive
to a larger range of the color spectrum,
including ultraviolet light.
As light passes through deeper and deeper waters,
more color is absorbed and diluted.
(gentle music)
The water filters out the color red at first,
then yellow, then green, and then violet.
The color blue is the last to go.
And yet as recent studies show,
ultraviolet light penetrates far deeper into the water
than used to be thought.
(water ripples)
Could this be the reason why
so many fish are so very colorful,
that while their colors might, to the human eye,
be muted by the ocean depths,
to a fish with ultraviolet sight,
these creatures still stand out as bright and beautiful.
(upbeat music)
The answer appears to be yes, in some cases.
Many coral reef fish, for example, are brightly hued,
coming in a dazzling array of colors.
(gentle music)
The harlequin tuskfish, mandarin fish,
coral trout, regal angelfish, and stoplight parrotfish
all spring to mind.
(gentle music)
Scientists believe that
some fish use their brightly colored skins
to attract a mate,
but as with so much in nature,
it's more complicated than that,
(gentle music)
for color is also employed by some fish
as a warning system, a warning to back off and stay away.
Lionfish, for example,
are thought to utilize their brightly colored bodies
to communicate to other animals
that it's best to stay away from them
and more specially, their highly venomous spines.
(water ripples)
Then again, there are instances
when fish like to blend in with their surroundings.
Literally it's called cryptic coloring
and it enables some species of fish
to camouflage themselves.
(suspenseful music)
(water ripples)
A predator like the great white shark
might seem like the last customer
who would need to hide itself away.
(suspenseful music)
But the great white, along with many other open sea fish,
uses counter shading to camouflage itself
on a regular basis.
(suspenseful music)
(water ripples)
But one of the strangest and most effective
underwater senses is known as echolocation.
(dramatic music)
This is very much what it sounds like, in a way,
being able to locate something because of its echo.
(water ripples)
It's also known as sonar,
which humans have studied and replicated,
for example, for use in submarines in naval warfare.
This is a system for detecting objects underwater
by emitting a sound pulse,
(dolphin clicks and squeaks)
and then being able to detect and measure it upon its return
to find out where something is, its size, and so on.
(upbeat music)
Call it seeing with sound,
because in effect that's what it is.
(sonar beeps)
Dolphins use echolocation all the time.
(upbeat music)
Like all toothed whales,
dolphins have specialized fat located in their jaws
which conveys sound waves from the ocean to their ears.
(dolphin clicks)
(upbeat music)
They use echolocation to crater feed,
meaning to find prey underneath the sand,
because unlike other senses,
echolocation can penetrate or see through solid matter.
(dolphins squeak and click)
It's a primary sense for dolphins
and other species of toothed whales.
That's right, a dolphin is also a type of whale,
a type of toothed whale to be precise.
(dolphin clicks)
Other varieties of toothed whales
include sperm whales, killer whales, and beaked whales.
All of these creatures use sonar or echolocation
to guide them through the oceans,
to communicate, and to detect prey.
(water rushes)
As you'll recall, the distant,
50-million-years-plus distant,
ancestors of whales were actually land dwelling-mammals,
who probably saw things quite well in the open air.
Echolocation helped them adapt to life underwater.
(water rushes)
(gentle music)
Navigating the open ocean
with its shifty currents and expansive water,
for most animals is no easy feat.
But sea turtles have to face up to the challenge.
There are seven species of sea turtles
found in the oceans all around the world.
They spend their first few years
floating in the open sea
where they feast on jellyfish and other creatures.
(gentle music)
But at some point they need to find their way
to the beach to breed.
(water ripples)
And it's not just any beach.
They return to the one they were born on.
(waves whoosh)
How they actually do this is still being debated,
but it's thought they may use
the earth's magnetic field as a cue
and perhaps their sense of smell plays a role as well.
(water rushes)
On this stretch of South American shoreline,
an olive ridley turtle clambers slowly up the beach.
This female adult is about to lay a clutch of eggs.
(upbeat music)
(birds call)
(eggs plop)
Over 100 eggs can be deposited in a nest at any one time.
(flippers scrape sand)
(upbeat music)
(eggs plop)
Once the eggs are buried,
the adult returns to the water.
(birds call)
After incubating for over 45 days,
hatchlings emerge to begin a perilous journey.
(birds call)
They race to the water's edge,
but vultures with a taste for turtle are patrolling.
(turtle chirps)
(birds mutter)
And even when they reach the sea, it's still not safe.
(birds call)
Few hatchlings make it to the feeding grounds
in the open ocean.
It could be why the olive ridleys
have a remarkable nesting strategy.
(water ripples)
In a spectacular mass nesting get together
known as an arribada,
thousands of females come ashore simultaneously to lay eggs.
(waves whoosh)
How the females know the time is right is unknown.
They may release a scent that cues the start,
but with no conclusive answer,
the arribada continues to be one of nature's great secrets.
(dramatic music)
On "Animal Super Senses,"
we've taken you from the surface
to the depths of the seven seas
to seek out the treasures below,
from the tiny colorful fish of the coral reef
to the mighty sperm whale.
We've explored how these creatures
hear the vast beauty of the ocean world.
It could make you wonder why our ancestors
ever came out of the water in the first place.
Just be sure we'll come to our senses again,
next time on "Animal Super Senses."
(dramatic music)
(water ripples)
(dolphin splashes)
(waves whoosh)
(dramatic music)