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Any one fascinated by the natural world
has probably wondered why some animals
have such strange looking sense organs.
The elephant with its huge ears,
the antennae of a butterfly,
which up close look like feathers,
the snake when its 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.
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,
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.
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Welcome to Animal Super Senses,
the show that enables you to see it, hear it, taste it,
smell it, and feel it like animals do.
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Animals use sight, smell, taste, touch,
hearing, and other special senses, to negotiate their way
through a sometimes cruel and unforgiving world.
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On this episode, we travel from the desert to the forest,
Australia to Borneo and back,
to learn how species as diverse as bat-eared foxes,
the bilby, deer, kangaroo rats, cicadas,
proboscis monkeys, and other creatures,
never miss an auditory trick.
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In these huge expanses of shrubland, grazed and fought over
by some of the most recognizable wildlife on the planet,
we find this particularly curious critter.
The bat-eared fox makes its home in areas
with short grass and low scrub,
feeding on mostly insects and invertebrates.
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To get a hold of creatures that small,
it helps to be able to hear them,
so the large ears of the bat-eared fox
aren't just for decoration.
They're filled with blood vessels
which help cool the animal down during the day,
just as well, because it gets hot out here on the savanna.
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But their ears are also an effective sound gatherer,
funneling sound to the inner ear.
What's more, these swiveling ears can turn 180 degrees
to help locate their tiny prey,
as well as the animals that prey on them.
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Bat-eared foxes have to be especially alert
to the sounds of the slender mongoose, brown hyena,
and black-backed jackals,
all of which can kill and eat bat-eared foxes
at regular intervals.
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Good hearing in general is a huge advantage
for animals who would rather avoid being eaten.
The desert offers lean pickings for omnivores,
with sparse vegetation, meaning fewer places to hide.
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The bilby seems to spend most of its time
avoiding being eaten.
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A marsupial, in fact, the largest known member
of the bandicoot family,
the bilby is truly a nocturnal animal.
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They usually don't come out of the ground
until long after dusk
and head back an hour or two before sunrise.
If it's a full moon or there's heavy wind or rain,
bilbies will stay cooped up in their burrows all night.
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When they do get out amongst it,
they rely on their hearing to survive.
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Notice their large, mostly hairless ears,
which allows sound to past unheeded to the inner ear
and also helps to amplify sound.
In fact, it's not unlike the effect
of cupping your hands behind your ears.
But of course, there's a lot more
to animal's super sense of hearing
than having outsized ears.
Take banner-tailed rats, for example.
Their hearing is so keen that they can hear
wind ruffling the feathers of an owl
flying through the forest at night.
Yet, unlike the bat-eared foxes we saw earlier,
the ears of the banner-tailed rat, aren't particularly large
in proportion to the rest of their body.
It's the large feet and hind legs
that stand out on this animal.
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No, with the banner-tailed rat,
all the precise audio engineering work
goes on inside the creatures ears.
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Banner-tailed rats have a huge eardrum
beating away inside that medium-sized ear
and a larger than usual middle ear chamber to boot.
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Large bony structures surrounding
the banner-tailed rat's inner ear
enhance their extremely sensitive hearing.
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Size is no guarantee
when it comes to animal sensory strength.
Some of the smallest animals have the largest powers
of hearing and auditory communication.
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Though their habitat is different,
deer are another animal who rely on their sense of hearing
to stay out of the way of trouble.
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You'll note that they too have large pinnae ears
which move independently.
This directional hearing
means they can zone in on where a sound is coming,
and it is believed from how far away,
meaning how fast they'd better run to get away from it.
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This, in large measure, is why it is so hard
to sneak up on a deer in the woods.
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And as all those deer hunters out there
could possibly attest, deers instinctively distinguished
between the sounds it hears every day in the forest
and unfamiliar noises such as the opening of a car door
or human footsteps.
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In some respects, hearing is the most important
of deer senses, for though their sense of smell is acute,
an ill wind can always blow outdoors
in an unhelpful direction,
whereas they can rely better on their ears to guide them.
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Deers also hear things at a higher frequency than humans,
though we can pick up on things
lower in the spectrum than they can.
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Rodents, such as the lowly rat and humble mouse,
come with the gift of ultrasonic hearing
as standard equipment.
That means they can hear in a frequency
above the human ear's audibility limit.
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The hearing range most often means
the range of sound waves and vibrations
which can be heard by humans and other animals.
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The easiest way might be to imagine a piano keyboard.
Humans typically hear notes in the middle of the keyboard.
Others very high or very low are inaudible to us.
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At the lower end of the scale,
rats and mice and other rodents
don't just make the squeaky noises
we humans are able to pick up on.
Oh no, they are able to communicate
in a whole rich world of sound and auditory cues
but outside of our range of hearing.
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Imagine what it might be like if we could hear it.
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Larger animals that are able to hear things
in the infrasonic range tend to have large heads,
as in larger than human,
and have fair-sized ears set wide apart.
There's perhaps no better example than the elephant.
Of course, elephant ears are notable
for a variety of reasons.
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For one thing, they can move their ears back and forth
which helps cool them down.
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They contain a network of blood vessels
which help to regulate the elephant's temperature,
circulating blood through its ears.
Elephants can hear things at 20 frequencies lower
on the hearing range than we can,
in the range known as infrasound.
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That low rumbling sound you sometimes hear elephants make,
that's the thin edge of the wedge.
Other elephants can pick up on such rumblings
and others we cannot detect, as far as six kilometers away.
These long distance conversations are useful
in letting male elephants know when females are around
and if they're in heat.
Mating season and this rumble of the jungle
is no joke for elephants.
It's only for a few days out of every two to four years
that females are ready to mate,
and that's when they send out this mating call.
It's the call that no bull elephant wants to miss.
As well as those gigantic flapping ears,
elephants can detect sounds
through their trunks and their feet.
Both come with receptors
that pick up on those low frequency vibrations
in the infrasound spectrum.
When you see an elephant with their trunk on the ground
and their feet carefully positioned,
it means they're having a good old listen.
They could be tuning into the subsonic rumblings
made by other elephants
or listening out for thunderstorms and the approach of rain.
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In the dry season on the African plain,
this is a huge advantage, as they can move towards the rain
and towards water, which is vital for survival.
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The large ears of bat-eared foxes and elephants
give them their ability to amplify sound.
But there's one rather singular animal
who uses another part of its body to amplify sound.
Because it's important to hear what's going on,
communicating your message can be a matter
of life and death.
To make our case in point,
we travel to the world's third largest island,
one whose very name has become a synonym
for the wild side of nature,
Borneo, home of the proboscis monkey.
This primate, found exclusively in the wilds of Borneo,
has many unusual characteristics.
One of the largest and most distinctive of all primates,
they have partially web feet and make fine swimmers.
And it's the male of the species
who develops the largest nose.
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But it's protruding nose is also an aid
in spreading the alarm when danger is near.
When feeling threatened,
the male proboscis monkey's nose swells up,
and this swelling means his nose acts as a sound chamber.
The monkey's call of anguish or alarm
echoes off those chamber walls.
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Its cries traveled further, hopefully reaching females
and warning them of impending danger.
Most often crocodiles or clouded leopards,
or sometimes, sad to say, humans.
The proboscis monkey is on the endangered species list.
From a nose that works as an amplifier,
to an up close examination of creatures in the insect world
whose sense of hearing originates in some odd places.
Cicadas and grasshoppers carry their ears on their abdomens.
While crickets and katydids hear through holes
in their hind legs.
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Their reason for being there?
Well, sound detection generally works better
when the detectors, the ears, are set far apart.
Crickets, and katydids certainly need
their sensitive auditory system.
As most of us know from experience, the leaf-like insect
has a proclivity for making a lot of noise,
especially on warm summer nights.
It's critical for survival to discriminate
between the sounds of a receptive mates singing right back,
and the sound of a bat
whose calls may be in the same frequency.
Striking a bum note in this case
could be a matter of life and death.
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Especially when you consider the animal
which crickets and cicadas have most reason to fear,
the bat, and its super sense of echolocation.
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Bats, of the kind the cricket and cicada
need to listen out for,
rely on echolocation, which in simple terms,
is like seeing through sound.
It's an interesting fact that bat species
use echolocation all the time.
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Bats are generally nocturnal
and catch their prey while in mid-flight.
Echolocation enables them to decode
thousands of sound signals.
These sound signals bounce back from a tree's leaves,
branches and trunk, to build a sound picture
of their surroundings.
Echolocation helps bats to find their preferred food types,
insects such as crickets and cicadas.
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But the really neat thing about echolocation
is that it also enables bats not just to hear a sound
but to really make a noise.
Bats generate ultrasound waves through their larynx
and emit sounds through their open mouth or nose.
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Fascinating in recent research
has shown that, quite conclusively,
bat males sing in ultrasound to attract females.
What the research seems to prove
is that female bats are more attracted to those male bats
whose mating calls are more elaborate.
Even stranger and more revealing
is the fact that both male and female bats sing in secret,
at a frequency perhaps few,
if any, creatures of their environment can hear.
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It's almost as Bram Stoker put in Dracula,
"The children of the night.
What sweet music they make."
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The forest at night.
Aside from the sound of a bird tweeting,
wind blowing, or the crackling of twigs,
seems to us a pretty quiet place
but with the right kind of ears,
it is a cacophony of sounds.
Somewhere in the midst of that primeval dark,
an owl flies, almost noiselessly, through the night air.
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Silent, but violent, the barn owl as depicted here,
is reckoned by some as the most widespread
bird species on earth.
Sharp eyesight and the fact that they fly
almost silently through the air,
have a lot to do with their prolific success has predators.
But maybe the real stealth weapon in the owl's arsenal
is they're super sense of subsonic hearing.
You won't hear an owl coming,
unless they issue their signature call,
but they will most certainly hear you.
Owl ears are also asymmetrical,
which is to say, the left ear is not level with the right.
As with all smart evolutionary design,
there's a good reason for this.
Asymmetrical ears give them the direction of sound,
the difference in time it takes
for a sound to reach the right or left ear.
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Put it this way: owls can hear a rodent
moving under several feet of snow from 50 feet away.
When you think of it that way,
the poor little critters just don't stand a chance.
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On Animals Super Senses, we see it, hear it, taste it,
smell it, and feel it like animals do.
The senses are the star of the show
and this episode has been no exception.
The sense of hearing has taken us on a memorable journey,
but these incredible powers of perception
will fight again another day,
so join us next time on Animal Super Senses.
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