All language subtitles for NOVA.S48E12.Bat.Superpowers.1080p.x265-ZMNT_track3_[eng]

♪ ♪

♪ ♪

NARRATOR:
60 miles west of Bangkok
is the Khao Chong Phran cave,

famous throughout all of Asia.

♪ ♪

For centuries,
a sanctuary for the faithful...

and now, the curious.

Scientists... who come to learn

from the most unusual
of creatures...

♪ ♪

As the sun sets, three million
bats begin to stir,

preparing for one of
nature's greatest spectacles.

Rocketing to the skies in a
blizzard of flapping wings,

they will pass the night
gorging on insects.

This epic nocturnal excursion
is a feast for the eyes.

But for science, bats are much
more: a biological treasure.

EMMA TEELING:
They are by far

the most fascinating
of all animals.

(squeaking)

SHARON SWARTZ:
They are remarkable
and extraordinary creatures.

JARED HOLMES:
As a biologist, it's my job
to really tell people that

we, we need the bats.

NARRATOR:
There are more than 1,400

different species of bats,
playing crucial roles

in ecosystems
all over the world.

But for many people, bats
are the stuff of nightmares.

Bats have been demonized
in the society.

♪ ♪

KENNY BREUER:
I thought bats were
scary and creepy

and a little bit
kind of unpleasant.

(screams)

NARRATOR:
Already vilified in pop culture,

recent news reports

have been giving bats
an especially dangerous rep.

The ancestor of the virus
in humans had to be a bat virus.

(translated):
There is a virus
that is 96% similar

to this new coronavirus in bats.

REPORTER:
Early research suggests human
picked up the coronavirus

from animals, possibly bats.

NARRATOR:
Though we still don't know the
exact source of the virus

that started the COVID pandemic,
bats are a prime suspect.

But rather than fear these
flying creatures,

biologists are hailing them
as potential saviors.

MATAE AHN:
They can really get infection
without getting sick.

LINFA WANG:
Bats teach us lesson,

not to suffer autoimmune
disease,

diabetes, arthritis.

SÉBASTIEN PUECHMAILLE
(translated):
Whether you capture a bat

that is two years old or 15,

or 20 years old,

you don't see any difference.

GARY MCCRACKEN:
For the body size of these
animals,

they are way off scale
in terms of their longevity.

TEELING:
Bats hold the cure.

They hold our treatment.

NARRATOR:
Science is beginning to decipher
their strange powers.

Could these much-maligned
creatures hold precious secrets

for our own health?

(bats squeaking)

"Bat Superpowers."

Right now, on "NOVA."

♪ ♪

♪ ♪

NARRATOR:
Many experts believe that the
coronavirus

that tore through the
world's population in 2020

came from a bat.

Virologist Supaporn
Wacharapluesadee

is world-renowned
for her ability

to track viruses in the wild.

Today, her team has come to test
the giant colony

at Khao Chong Phran.

WACHARAPLUESADEE (translated):
There are bats in the caves,
and we put this on

to be safe while we work.

It doesn't mean that there
are deadly viruses in there,

but we need to protect ourselves

to do our work safely.

NARRATOR:
Once fully suited up,
the scientists descend

deep into the cave.

Under the gaze of the Buddha
statues, the team installs

a net in the large chamber

that local monks share
year-round

with its native residents.

WACHARAPLUESADEE (translated):
We have been doing research work
here for more than ten years.

Now, for safety reasons,
we have come back to test

if there is coronavirus,

which could be dangerous
for the people in the area.

NARRATOR:
A second team waits at the exit

of the cave to catch bats flying
outside.

Tonight, about 70 bats will miss
their nighttime excursion.

♪ ♪

Instead, they will spend
a few hours in a makeshift lab

set up at the base of the hill.

Each bat is given
a careful medical checkup.

Trying to limit stress to the
animal,

scientists take multiple samples
from the skin,

the mouth,
and even the intestines...

all organs that are susceptible
to containing viruses,

known or unknown.

WACHARAPLUESADEE (translated):
We have discovered hundreds of
viruses in bats.

Actually, there are more
than 60 viruses in bats

that could eventually
be transmitted to human beings.

NARRATOR:
In addition to being

a key transmitter
of the deadly rabies virus,

bats are suspected sources

for numerous viral outbreaks
around the world:

the 1967 Marburg virus
in Europe;

two waves of Ebola in Africa;

the Hendra virus in Australia;

the Nipah virus in Malaysia.

Then a series of coronavirus
outbreaks:

SARS, that started in China;

MERS in the Arabian Peninsula;

and now the COVID-19 pandemic

that engulfed the planet
in just a few months.

For some scientists,

it is a trend that
will no doubt continue

as human beings encroach

more and more on the
bat's natural habitat.

Supaporn is hoping to discover

why viruses circulate
so well within bat colonies

and how they might transmit them

to other animal species

that in turn
could pass them on to humans.

But above all, she wants
to know why this animal,

infected by
so many dangerous viruses,

seems totally impervious
to their effects.

WACHARAPLUESADEE (translated):
As far as I know from
the research work

overseas
and my research work here,

bats with viruses
aren't getting sick.

The bat aren't getting sick
while the viruses still

live within them.

♪ ♪

Because of the whole world
is so desperately trying

to deal with, with COVID-19
and its horrible effects,

bats have come
into the limelight,

and they've
come into the limelight

as potential reservoirs
for many, many viruses.

And the question is, why?

Why can they...

Are bats really special?

Is there something unique
about bats' biology,

their physiology, the genetics,

that allows them
to tolerate these viruses?

What's the reason?

NARRATOR:
Will studying bats allow us

to avoid the next deadly
virus outbreak?

Could their disease-defying
biology

help us to live longer
and in better health?

Laboratories around the world
are mobilizing

to find the answers.

Because just how this stealthy,
nocturnal animal functions

remains largely a mystery.

♪ ♪

New Yorkers may not realize that
one of the most unique

biological banks in the world
is just next door:

a huge collection of bat organs
and tissues, stored at

Stony Brook University.

A veritable treasure trove for
scientists like Liliana Dávalos.

♪ ♪

DÁVALOS:
It's a piece of brain
from Belize.

This is, um,

liver, liver sample,
and it's from Colombia.

This is from our last
expedition.

Our collection has

everything from the

top of the head, the brain,
the nose, the eyes,

and every organ in the body.

♪ ♪

NARRATOR:
Mummified bats,

cabinets stuffed
with body parts...

the Dávalos Lab might feel
like something

out of a Frankenstein film.

(electricity buzzing,
machine roaring)

Not to worry...
It's not what you think.

And Liliana,
rather than being frightened

or repelled by bats, is in
fact one of their biggest fans.

DÁVALOS:
What have we got here?

Oh, this is so amazing.

This is a horseshoe bat.

This collection happened
in 1934,

December 27.

Somebody was out there,

in Chengdu, in China,
catching bats.

This is the horseshoe down here,
you see it?

NARRATOR:
The horseshoe bat is widespread
throughout Asia

and suspected to be
at the origin of SARS-CoV-2,

the virus that causes COVID-19.

With this specimen,

Liliana will be able to study
just how bats become infected.

Since COVID
is a respiratory disease,

the team concentrates their
efforts

on the animal's respiratory
tract,

especially its nose
and nasal cavities.

♪ ♪

Could it be that the inside
of this strange-looking nose

contains the key to how
bat viruses also infect humans?

Thanks to Laurel Yohe,

a researcher at nearby
Yale University,

the team has access
to a 3D scanner.

It's the first time ever this
technique will be used

to study the inside of a bat.

(typing)

(scanner beeping)
YOHE:
Here are the teeth.

You can see the neurons
in the teeth.

As we move through,
here is the tongue.

Here is the nasal cavity.

NARRATOR:
The horseshoe bat's nose is
of particular interest

to Liliana and her spouse
and research partner,

Angelique Corthals.

An expert in human biology,

Angelique studied
the respiratory tracts

of COVID victims
at the height of the pandemic.

The bat is very similar
to humans,

because you can see actually
the same structure of the nose.

CORTHALS:
Bats that are known to harbor

the closest relative to
SARS-CoV-2

have a nasal cavity

that is to,

that is actually closely
resembling that of human,

which is very likely

part of the reason
why we can be infected

so quickly with SARS-CoV-2,
because all of a sudden,

it's not completely strange
territory for coronavirus

to enter the nasal cavity of a
human.

NARRATOR:
But once it has arrived in
the nose of a bat or a human,

how does the virus
infect the rest of the body?

Liliana and Angelique
focus their research

on the cells
that line the nasal cavity.

CORTHALS:
You see those hollow points
in this layer?

Those are not holes,
they are cells...

they are called
the goblet cells,

which are mucus-producing cells.

They are the first barrier

against pathogens,
against allergens,

against any kind
of foreign bodies

that enters through the nose.

NARRATOR:
Mucus produced by goblet cells

usually traps viruses before
they can enter the body.

But when it comes to COVID-19,
goblet cells have a weakness:

they are covered by a receptor
that the coronavirus recognizes.

Like a key entering a lock, the
virus attaches to the receptor,

opens a passage,

and injects
its genetic material.

The cell then starts
manufacturing the virus

by the hundreds, starting a
chain reaction that can spread

throughout the whole organism.

The coronavirus can enter both
bats

and humans in the same way,

through these goblet cells.

So how come humans can become
so sick,

while bats don't?

♪ ♪

DÁVALOS:
Our scientific understanding
so far

is that the viral loads are
fairly low,

meaning that these infections
are circulating,

but they do not have the same
consequences

in the bats that they have
in people.

We don't understand yet
fully why.

♪ ♪

NARRATOR:
Somehow, the virus is able
to enter bats' noses

the same way it does in humans,
but the similarities end there.

In bats, the virus is present,
but at a consistently low level.

The question is:
how are bats keeping the virus

under control
once it has entered?

That's what scientists in
Singapore

are trying to find out at the
Duke-N.U.S. Medical School,

where the bats' immune system
has come under the microscope.

Professor Linfa Wang,
known to colleagues as "Batman,"

thinks he has found the
secret to bats' super-immunity.

WANG:
My students, when they first

work in my lab, they got it
wrong.

They say bats has
a more efficient

immune system to clear
the virus.

I say. "No, bats have
a more efficient immune system

not to develop disease."

They are more efficient, really,

to control the virus.

Otherwise, they will not be
good reservoir, right?

NARRATOR:
Matae Ahn wrote his thesis
under

Linfa Wang's direction.

When he joined the team in 2014,

the lab did not yet have a
living bat colony to work with.

AHN:
In the past, we had to

fly over to Australia
to get all sample

for our studies, and now,

we have a local bat colony,
right here.

And this allows us
to get the fresh sample easily

and study bats really closely.

NARRATOR:
The cave nectar bat
has a fox-like head

and lives principally
in Southeast Asia.

In the wild, these bats are
carriers of many viruses,

but don't get sick.

But in the lab, conditions are
strictly controlled

and the animals
remain uncontaminated.

AHN:
We are using
the fresh bat samples

to analyze their contents
in details,

starting from genes, mRNA,

protein, cells, to even tissues.

And all of these component
can be

used and utilized to study bats

and their immune system.

♪ ♪

NARRATOR:
Matae's experiment
concentrates on

proteins involved in the
immune response,

and on one molecule in
particular: interferon alpha.

AHN:
To be simple, interferon alpha

is a key molecule that alerts
the body to the intruder.

It tells the surrounding cells
that an infection is occurring.

NARRATOR:
When a cell detects a virus,

it unleashes a barrage
of interferon molecules

which spread through the body,

spurring immune cells
into action.

Which, in turn,
wipe out the intruding pathogens

and get rid of the cells
already infected.

AHN:
So we want to examine
and compare

the level of interferon
production

between human and bat cells

before any infection
actually occurs.

(whirring)

(device beeps)
So look, look at this curve.

This curve is a human sample,
it's flat.

It means that interferon alpha

is almost undetectable.

In contrast, in our bat sample,

we have a lot of
interferon alpha detected,

even though there is no
infection occurring right there.

NARRATOR:
In other words,
bats have adopted

a proactive strategy of defense.

(whirring)

Thanks to interferon being
permanently present,

when a virus penetrates
the bat's body,

their immune system
is already active.

But in humans, that reaction
is much slower.

While our body's immune system
is ramping up

to produce interferon,
the virus can be spreading.

The risk of getting sick is
therefore much greater in us

than in bats, where the virus
remains under tighter control.

WANG:
Human, for example,
our defense system

is switched off
most of the time,

until we see enemies,
and then we switch on.

NARRATOR:
Unlike us, the bats' defenses
are always on high alert.

Their immune system can prevent
damaging infection

while letting some virus
hang around.

That's good news for the bat,

but it might be really bad news
for humans.

WANG:
One theory is that

if the virus live
inside a bat body,

you know, you already
have elevated defense systems.

So when they jump to a different
host, like human,

and that's, it's, like, you
know, free playground for them

and they just go and rampage
in us.

So very efficient.

NARRATOR:
A virus that battles
for survival

inside a bat's
super-immune system

becomes a formidable enemy.

When it jumps to a less defended
species, like a human,

it's much more dangerous.

But why did bats develop

such a highly functioning
immune system?

Why did nature bestow bats
with this superpower

while our own defense system
has proven so weak

in the face
of multiple epidemics?

♪ ♪

It's a question that zoologist
and geneticist Emma Teeling

has spent decades researching.

Nearby her lab at
University College Dublin,

Emma takes advantage of the last

few days of fall to visit
a local colony

before the bats start
their winter hibernation.

♪ ♪

TEELING:
Some people don't actually
like them,

and the question is why?

As primates, we primarily

get the information from our
environment

through our eyes.

At night,
we're a bit frightened...

we can't really see them.

People think, "Oh, they're
gonna get

caught in your hair"...
They, they don't.

What they do is, they're flying,

feeding on insects
that are trying to bite you.

♪ ♪

(animal clicking)

There you go, there's a bat.

More than likely, it's a,
it's a...

Oh, hello, you beauty.

More than likely, this
is a soprano pipistrelle.

Because you can hear, its
peak frequency

is about 45 kilohertz.

Do you see that little bat
fly across?

This bat detector is picking up
the sound

that's been emitted from
the bat's mouth.

And what's happening is, the bat
emits its call

and it listens to the echoes,

and it uses this to be able
to orient in complete darkness.

I have a head torch on right
now.

Right now, this is dusk...
You can't see anything,

but the bats have woken up
and they are flying around,

feeding on the insects,

and are more than likely flying
up and down

this small stream here.

(bird squawks, bats clicking)

Hear?

Bang-bang-bang-bang-bang?

(bats clicking)

NARRATOR:
Aided by their
unique capabilities,

bats thrive on every continent
except Antarctica.

It's a story of
extraordinary adaptation,

the secrets of which
are inscribed

in their DNA.

A wing flap away is
Emma's center of operations,

a laboratory of mammalian
molecular evolution.

Equipped with the latest tech,

it's affectionately called
the Batlab.

Here, Emma co-pilots

one of the largest studies
of bats in the world.

The project Bat1K

connects over a hundred
scientists around the globe

in a joint effort

to sequence the genomes
of the approximately

1,400 bat species.

TEELING:
We wanted to sequence

the entire DNA code that's
in every single cell

of a particular species,

but we wanted to do it to
the quality of the genomes

that we have for humans or mice,
so that we could now use this

to investigate the likes of,
what have bats evolved

to allow them live
with coronaviruses and not die?

♪ ♪

NARRATOR:
Bat1K's approach is to compare
the billions of letters

that make up bats' genetic code
with the DNA of other mammals.

In theory, finding out
what is different

will lead researchers
to those parts of the bat genome

responsible
for its robust health.

TEELING:
Darwinian selection...
did natural selection act

on a particular part
of the genome in bats

that make it very different

at the same region in bats
and everything else?

And this may indicate
that this is the region

that's driving
their unique adaptations.

♪ ♪

NARRATOR:
Bat1K has already fully decoded
the genomes of six bat species:

the velvety free-tailed bat,

the greater horseshoe bat,

the Egyptian fruit bat,

the pale spear-nosed bat,

the greater mouse-eared bat,

and Kuhl's pipistrelle.

A meticulous comparison
of their DNA

with that of land-based mammals

revealed something totally
unexpected.

When the bat's ancestor
developed wings

and evolved the ability to fly...
At least 55 million years ago...

the genes controlling their
immune system also evolved,

mutating significantly.

It's as if their evolution
as flyers

somehow provoked or required

a similar evolution
in their immune system.

TEELING:
They can fly.

They're able to tolerate
all their,

these, these unique viruses...
Is there a connection?

What's the connection?

And this is something I've been
working on for a very long time.

I have written research grants.

I've gotten slammed,

I've gotten abuse
left, right, and center.

It's caused such scientific
controversy, and it still does.

So the idea is, evolving...

Could evolving a new form of
locomotion

drive an immunological
and a genetic response?

A physiological response?

So I'm going to argue that yes.

NARRATOR:
For Emma Teeling,
bats' extraordinary resistance

to viruses seems
to have evolved hand-in-hand

with their other superpower:

their supreme prowess
in the air.

But how could flight protect
this tiny mammal from sickness?

What is the link
between the two?

As the only mammals known
to have evolved true flight,

bats' flying technique
is totally unique

in the animal kingdom.

Every year at the Frio Cave,

about 70 miles west
of San Antonio, Texas,

newborn bat pups
will take to the skies

for the very first time.

♪ ♪

(chuckling)

Millions of female Mexican
free-tailed bats migrate here

in the spring, and it's the
perfect opportunity

for biologist Gary McCracken

to observe the animals
in action.

MCCRACKEN:
This is the time of year when
mothers are beginning

to give birth to their pups.

We can't go very deep into the
cave

with everybody,
lights or cameras,

because it's just too disruptive
at this time of year

for, for the bats, so we're
respectful for that, yeah.

There you go!

NARRATOR:
Gary goes just inside
the mouth of the cave

so he won't disturb the pups.

MCCRACKEN:
I well remember the first time

that I went into a
Mexican free-tailed bat cave.

I thought I was on the surface
of the moon.

I mean, really,
the dust covering the rocks,

you, you walk
and your footprints stay there,

and then they get
reworked by the beetles.

The atmosphere is heavy

with simple compounds
of carbon and nitrogen,

methane and ammonia.

I mean, it really does seem
like you're on another planet.

(bats squeaking)

When I first saw the babies,

the dense concentrations of
babies, it was just amazing.

Soon, you've got
4,000 to 5,000 babies

in an area of about
a square meter...

4,000 to 5,000 babies.

NARRATOR:
After about a month clinging
to the walls,

the young pups will attempt
their very first flight.

The slightest error
could be fatal.

MCCRACKEN:
It's really awesome to imagine

what it must be like
to take that first flight.

Looking down below...
(chuckling)

Thinking about, what happens
if I don't make it?

And, and if you don't make it,
you're not going to get back.

You're going to,
you're going to,

you're going to land
in the guano

and, and be eaten
by dermestid beetles.

And, you know,
the amazing thing is that

it seems that the vast majority
of them do make it work.

NARRATOR:
Once mature,
the Mexican free-tailed bat

develops into an extraordinarily
powerful

flying machine, and it's their
outstanding performance

in the air that Gary
has come here to measure.

Helping him is local biologist
Jared Holmes.

HOLMES:
Yesterday, they started flying

about 7:30.
MCCRACKEN:
Uh-huh, yeah.

So we'll be ready
by 7:30, for sure.

Okay.
Yeah, we'll have
the plane ready to go.

So I'll tell you
when we're taking off,

and you get the bat ready

and stick the radio on it.
Oh, all right!

These bats weigh
a half an ounce, 12 grams.

They are too small, too light
with current technology

to carry GPS trackers.

But they can carry
these little radios

that are basically location
locators.

HOLMES:
And we're still looking
for a female bat

of, of average size...
Average size.

Not too pregnant.

Gotcha.
And, uh,
and obviously, good health.

A nice plump one.
Yup, yeah.

Yeah, just a nice bat.
Okay.

♪ ♪

NARRATOR:
The next day, on the tarmac
at Garner Field airport,

not far from Frio Cave,

Gary adjusts the settings
of his radio telemetry receiver.

This device will use
radio signals to follow the bat

that Jared is about to capture
and equip

with the transmitter.

(plane door shuts)

MCCRACKEN:
With the airplane,

it is possible to triangulate
the location of the bat.

And by carefully listening to
the signal from the transmitter,

we're able to pinpoint the
location with some precision.

(radio chirps)
HOLMES:
Gary, the flight has started.

Are you in the air?

MCCRACKEN (over radio):
Jared, we're just taking
off right now.

We should be there
in 15 minutes.

HOLMES (over radio):
Okay, roger that.

I'm gonna go ahead
and try to catch a bat.

MCCRACKEN (over radio):
Be sure to get a nice, young,
fluffy-looking one.

(radio chirps)

♪ ♪

HOLMES (over radio):
I got a couple in the net, one
looks good.

I'm gonna go ahead and tag it,
gonna get it released.

Good deal.

This is working really well
right now.

(laughs)

♪ ♪

MCCRACKEN (over radio):
Okay, Jared, we're coming in,
we're approaching the zone,

we're approaching the zone.

I've got the signal.

We're right overhead.

(over radio):
Okay, you can release!

(radio chirps)
HOLMES:
Releasing her now.

HOLMES (over radio):
Gary, I see the plane, I hope
the bat's coming with you.

(radio chirps)

MCCRACKEN:
Okay... okay...

Okay, okay... got it!
Got it, good.

NARRATOR:
When the bat flies
just underneath the plane,

the radio signal gets stronger
and the pursuit begins.

As soon as the bat veers off,
the signal weakens,

allowing Gary to guide the pilot
to stay on the bat's course.

(device beeping at low pitch)
Can you speed up
just a little bit?

We're losing her,
we're losing her.

A little bit, a little bit.

(device beeping at high pitch)
Right on top, got it!

NARRATOR:
The plane is able to follow
the bat for three hours

as it circles the area,
hunting flying insects.

Now she's heading back north,

heading back in the direction
of the cave.

I think she, our bat went home.

This is so cool... wow.

NARRATOR:
When radio telemetry was used

a few years ago,
it allowed scientists to track

the Mexican free-tailed bat
for the first time

in mid-flight
with jaw-dropping results.

MCCRACKEN:
We knew the bats
were flying long distances.

We knew that this particular
type of bat

can fly really, really fast.

But we, we didn't expect to see
this, this sort of performance.

We think we've seen a bat going
100 miles an hour.

♪ ♪

NARRATOR:
After studying the data,

initial field observations
were confirmed:

the Mexican free-tailed bat
got up to speeds

of about 100 miles per hour,

the fastest horizontal
flight of any animal

ever recorded.

But even if bats have proved
to be the fastest flyers,

how would that help them
to resist diseases?

♪ ♪

Back on terra firma,
scientists at Brown University

are studying
the possible connections

between bat flight
and bat health.

Kenny Breuer
is an aeronautical engineer,

and for the past 15 years,

he has been creating
mechanical wings

that imitate the bat's anatomy.

His prototypes have improved,

but nothing comes close
to the real thing.

(mechanical whirring)

They have, however, helped him
understand the physical effort

required for bats
to navigate the skies.

BREUER:
Flying is an expensive operation

in terms of energy...
It takes a lot of energy

to get into the air
and to propel yourself.

And you have to not only
generate your own thrust,

but you have to overcome

the drag that is, that is
experienced

by your body and by your wings.

♪ ♪

NARRATOR:
Scientists estimate
that the physical effort

expended by a bat in flight
is about three times more than

a terrestrial mammal
of the same size

running at full speed.

The heartbeat
of certain flying bats can reach

1,066 beats per minute.

(heart beating rapidly)

Could this level of activity,
unrivaled by any other mammal,

somehow explain bats'
super-immunity?

♪ ♪

SWARTZ:
A few measurements

have suggested that
body temperature in bats

might be unusually high.

This has led some scientists
to suggest

that bats' body temperatures
might be so high,

that it's as if they
continually operate

at fever-like temperatures

during their nightly flights.

♪ ♪

NARRATOR:
Fever is well-known as
a means of fighting infection.

High temperatures slow down
the replication of the virus

and boost the foot soldiers
of the immune system

to devour intruders.

A feverish body is a hostile
environment for a virus.

So could the extreme energy
spent

during nightly hunting forays

cause a spike in
body temperature

that would protect bats
from viruses?

To know for sure,

scientists must collect data in
perfectly controlled conditions.

This is where
the Egyptian fruit bat comes in.

With its two-foot wingspan,

it is a remarkable
flying machine.

Equipped with expertly
placed mini-thermometers,

the animal takes flight
under the team's watchful eye.

ANDREA RUMMEL:
Oh, my God, that's not bad!

I'm very impressed.

- Great spread!
RUMMEL: Yeah.

♪ ♪

♪ ♪

NARRATOR:
The experiment was performed
on four different bats,

and the result was exactly
the same for each one.

RUMMEL:
We got these temperature traces

for three muscles
along the bat wing.

So the red is a muscle
that's in the core,

the pectoralis muscle, which
is really important for flight.

And then we have the biceps
and the muscle

in the forearm of the bat.

So closest to the core,

and then the blue curve
is furthest from the core.

And as time proceeds,

the red and the green muscle
stay pretty close

to the high body temperature
that it started with.

But as we move through time,
the blue muscle,

the forearm muscle that's
further away from the core,

gets really cold and stays cold.

As they're flying,
they're flapping their wings.

And so heat is going to be
wicked away

from, from the bat wings,

just by virtue
of their movement.

And so bats are really effective
at dumping heat,

even if they're generating
a lot,

and their body temperatures
stay fairly normal.

♪ ♪

NARRATOR:
In other words,
the naked wings of bats

act as an ultra-efficient
cooling system

that keeps their temperatures
from rising.

♪ ♪

There's no fever-like
temperatures

that could explain their
super-immunity.

But some researchers
are still convinced that flight

must have somehow helped
shape their immune system.

♪ ♪

♪ ♪

It sounds, like,
very promising...

NARRATOR:
One believer

is Linfa Wang, and he thinks
he's found out how.

(indistinct chatter)

WANG:
Especially in the
very ancient bats,

when they just acquired
flight capability,

the number-one challenge
they have to deal with

is this high metabolism.

NARRATOR:
The high metabolism required
for flight

should lead to inflammation:

when animals' muscles work
really hard,

the intense physical activity
creates toxic by-products,

and these usually trigger
inflammation.

Inflammation intrigues Linfa,
because it is also caused

by viral infections,
and in humans,

too much inflammation can have
devastating effects.

WANG:
For other mammals,
human included,

when the coordination goes,
you know, out a window,

and then when you over-defense,

that actually cause
the pathology.

You know, now you get disease.

So we have a cliché
in our field to say,

"Very few virus kills us,
we kill ourself."

NARRATOR:
This is what happened in some of
the most severe

cases of COVID-19,
when patients' immune systems

raged out of control

with so-called cytokine storms.

Cytokines, like interferons,

are molecules manufactured
by the body

to regulate an immune response
in case of an attack.

Sometimes, the system goes
berserk

and produces too many cytokines.

The resulting inflammation
doesn't just hurt the virus,

but everything in its path,
including organs like the lungs,

heart, and even the brain.
(EKG flatlining)

But bats don't seem
to experience these symptoms.

So, have bats figured out a way

to control the inflammation
associated with

both high metabolism
and infection?

To find out,

Wang's team is mixing
bat immune cells

with toxic molecules

that, in humans,
would trigger inflammation.

AHN:
So actually, we have isolated
bat immune cells

and treated them
with the toxic substances

that are produced by the body

when the metabolism is high.

NARRATOR:
In most animals,

like humans,
these toxins trigger

the production of a protein
called NLRP3,

which in turn ramps up

the immune response
and inflammation.

This microscope reveals
the presence of the protein

in the form of a red dot.

AHN:
We are comparing
the inflammatory response

between human and bat cells.

NARRATOR:
In the human cells, the red dot
shows that the protein

is being produced, meaning
the immune response has begun.

But over on the bat side,

there are no red dots, meaning
no protein

and no immune response.

Their cells seem to have
tolerated the attack

of the added toxins

without any immune reaction.

AHN:
So, the bat have naturally
tempered NLRP3 protein,

so that the stress-related and
the viral-induced inflammation

always stay under control.

♪ ♪

NARRATOR:
To become successful flyers,

bats had to tamp down
their response to the toxins

produced during flight
and prevent inflammation.

Linfa Wang thinks this
same anti-inflammatory chemistry

is what's preventing bats
from over-reacting to viruses.

WANG:
Bats are very good
virus reservoirs.

You know, we believe is that
their adaptation to flight.

So that created
a very different immune system.

Of course, that was evolved
not to host virus, per se.

That's evolved
adaptation to flight.

So their ability to host virus

is almost like a by-product,
in my view.

NARRATOR:
For the team in Singapore, this
unique adaptation isn't just

an evolutionary curiosity...
It could pave the way

to revolutionary new therapies
for all sorts of

human diseases
that involve inflammation.

AHN:
In COVID-19 infections

and many age-related
chronic diseases,

such as Alzheimer's or stroke,
coronary artery disease,

diabetes... in all these
diseases,

inflammation is over-activated.

That cause a lot of problem.

♪ ♪

WANG:
I'm really excited, from a
basic scientist's point of view,

is that we are studying
a very important mammal

as a model for living, you know,

a health, you know... I mean,

to health living and longevity,
yeah.

♪ ♪

NARRATOR:
This is the paradox of the bat.

Held responsible for a pandemic,

could the bat also be the source

of potential new cures?

Not just to fight disease,

but also old age?

Could the bat, maligned
and misunderstood as it is,

also teach us the secret
to growing old healthier?

♪ ♪

♪ ♪

This is Beganne,
a village in Brittany, France,

whose bell tower is a well-known
refuge for bats.

Every summer, dozens of female
greater mouse-eared bats

roost in its rafters,
giving birth to their pups...

a species whose exceptional,
long lifespans

fascinate scientists like
Eric Petit.

But he must wait for nightfall

to spot the newborns
and their mothers.

PETIT (translated):
With the greater mouse-eared
bat, you have to be patient.

They don't come out very early,

so we've often got to wait
a long time.

(speaking French)

(translated):
We're in front of the exit.

In this colony,
there's about 90 adults.

We're hearing something
over there.

I think they're just behind
the drainpipe.

NARRATOR:
They're difficult to see,

discreetly slipping out
from behind the drainpipe.

But a thermal camera reveals
the frenzied

nocturnal ballet taking
place around the church.

In the surrounding underbrush,

this nocturnal acrobat shows
the full range of its agility.

PETIT (translated):
The greater mouse-eared bat is
known for hunting

between 12 and 24 inches
from the ground.

They listen for beetles
making noise

walking through the underbrush.

(speaking French)

(translated):
As soon as they hear one,
they jump on top,

grab hold of it, and fly off.

NARRATOR:
But it's not their agile flight
or unusual hunting methods

that have caught the attention
of scientists the world over.

It's their amazing longevity,

which seems to defy the laws
of nature.

PETIT (translated):
There is a general rule
in biology.

Smaller animals don't
live very long,

while larger animals
live much longer.

Mice live for a couple of years,

while elephants can live
dozens of years.

NARRATOR:
The oldest greater
mouse-eared bat

ever recorded was 37 years old.

But the record for longest life

is actually held by a cousin of
the greater mouse-eared bat.

The Brandt's bat weighs
less than a quarter of an ounce,

yet researchers captured
a specimen that was at least

41 years old...
A lifespan ten times longer

than theoretically expected.

♪ ♪

PUECHMAILLE (translated):
What's really fascinating
with bats

is that if you capture
an individual

that is two years old, or one
that is 15 or 20 years old,

you can't see any difference
between the two.

With humans, dogs,
and most other species,

you would see an individual

that has aged.

NARRATOR:
Sébastien Puechmaille
studies aging

at the Institute of Evolutionary
Science in Montpellier, France.

♪ ♪

(Puechmaille speaking French)

(translated):
When we study aging, one of the
first things we look at

is the central part of the cell,
which is shown here,

the nucleus.

Inside the nucleus, you see
these kinds of small Xs.

These are the chromosomes.

I've zoomed in on the most
important part

of the chromosome here,
its extremities,

which we see in red.

These are what we call
telomeres.

So this telomere
is a long fragment

that is in charge of protecting
the chromosome's extremity.

On young cells,
the telomere is very long,

and over time, as the cell ages,
the telomere gets shorter.

At some point,
it will get so short

that it will directly affect
the integrity of the chromosome

and the health of the cell.

NARRATOR:
Scientists think that
the shortening of telomeres

over time is one of the
key triggers of cell death,

influencing the aging process
and the lifespan

of all mammalian species.

So what's the deal with bats?

(bell tolling)

For the past ten years,
the bat colony at the church

in Beganne has been at the heart
of a study

to figure out the secret
to bats' long lives.

Every summer,
Sébastien Puechmaille

meets up with Emma Teeling
and her team

to collect samples
that allow them

to follow individual bats
and their aging process.

An implant gun is used to insert
a magnetic

identification chip the size
of a grain of rice

under the skin between
the shoulder blades.

Dozens of juveniles had been
tagged this summer.

(translated):
When we say "tag,"

it means inserting these
tiny microchips,

like we do with dogs
and cats at the vet.

This allows us to recognize

the same individuals
year after year

and to follow their aging.

NARRATOR:
The oldest tagged individuals
are now ten years old.

These are our sample numbers,
so what we take back to UCD.

Right.
So we know who's
who, and there she is.

TEELING:
Isn't that beautiful?

WOMAN:
Gorgeous.

Is that a baby?

TEELING:
We're gonna find out now
in a minute!

PUECHMAILLE:
It looks like an adult.

TEELING:
Do you want to bet?
WOMAN: Yeah!

TEELING:
You say a baby or an adult?
PUECHMAILLE: Adult.

TEELING:
Okay, can we, will we check
to see by shining?

It's an adult!

Now we are going to take
the blood.

Quite dark, isn't it?

NARRATOR:
Whether it's a drop of blood

or a small skin fragment,
the samples taken every year

are conserved carefully
in liquid nitrogen.

TEELING:
Do you see how
relaxed the bat is?

WOMAN:
Yeah.

TEELING:
It doesn't hurt them at all.

As long as they're
in capable hands,

with people who know how
to hold them properly

and correctly.

So there it is!

Secret of everlasting youth.

♪ ♪

NARRATOR:
Some of the precious samples
taken in Beganne are stored

in Sébastien's basement
laboratory in Montpellier.

To see if the greater
mouse-eared bat's longevity

could be linked to the length
of its telomeres,

scientists
have compared them with those

of the common bent-winged bat,

a species of bat that usually
dies before it reaches 20.

(translate):
What you see with the
common bent-winged bat,

which has a short lifespan,

that the telomeres shorten
with age.

You see that very clear
progression.

On the other hand,
the greater mouse-eared bat

shows absolutely no shortening
of the telomeres.

On the contrary,
you can see clearly

that they remain constant
as the individual ages.

So an individual bat which
is ten years old

or one year old,

the telomeres will be exactly
the same length.

TEELING:
What we found was extraordinary.

In the longest-lived genera
of bats, the myotis bats,

their telomeres do not
shorten with age.

And this was very unique.

We didn't really see this
in any other mammal.

Telomeres shorten in us,
in badgers, in sea lions.

So this was extraordinary.

NARRATOR:
Emma and Sébastien believe

that the greater mouse-eared
bat's

extraordinarily long life

is linked to the resilience
of its telomeres.

But how does
this genetic material

withstand the passage of time?

To find out, scientists compared
the genes

of the greater mouse-eared bat
with other mammals

and uncovered some key
differences.

TEELING:
We found two or three genes

that we think are evolving in
a different way in bats,

that we think are the genes
that allow this thing

called alternative telomere
lengthening happen in bats.

So bats are able to use
a different mechanism

to maintain their telomeres
with age.

NARRATOR:
Are these genes the key to the
bats' long and healthy lives?

And could they one day protect

against the effects of aging
in humans, as well?

Scientists aren't about
to turn this discovery

into an elixir of youth,
but researchers like Emma

are optimistic for the future.

Their adventure with bats
has just begun.

(crow cawing)

Echolocation that allows
them to see in total darkness.

Flight speed that is unrivaled
by any other animal.

They are impervious
to most viruses,

insensitive to aging,

and the masters of a marvelously
controlled immune system.

Not bad for an animal so long
despised.

TEELING:
Looking at bats,
one of the most vilified

and terrifying, potentially,
of all mammals.

If we look at them in a slightly
different light,

we will be able to find ways
to improve human existence.

♪ ♪

NARRATOR:
The product of millions
of years of adaptation,

bats are now emerging
from the shadows

as extraordinary creatures

that could potentially
light a path

for longer, and healthier,
human lives.

♪ ♪

♪ ♪

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♪ ♪