Nova (1974–…): Season 48, Episode 12 - Bat Superpowers - full transcript
Understanding bats, their long life spans and why they are resistant to the very diseases they carry such as Ebola and MERS, as well as other diseases like cancer.
♪♪
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.
They are by far
the most fascinating
of all animals.
They are remarkable
and extraordinary creatures.
As a biologist, it's my job
to really tell people that
we, we need the bats.
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.
♪♪
I thought bats were
scary and creepy
and a little bit
kind of unpleasant.
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.
There is a virus
that is 96% similar
to this new coronavirus in bats.
Early research suggests human
picked up the coronavirus
from animals, possibly bats.
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.
They can really get infection
without getting sick.
Bats teach us lesson,
not to suffer autoimmune
disease,
diabetes, arthritis.
SÉBASTIEN PUECHMAILLE
Whether you capture a bat
that is two years old or 15,
or 20 years old,
you don't see any difference.
For the body size of these
animals,
they are way off scale
in terms of their longevity.
Bats hold the cure.
They hold our treatment.
Science is beginning to decipher
their strange powers.
Could these much-maligned
creatures hold precious secrets
for our own health?
"Bat Superpowers."
Right now, on "NOVA."
♪♪
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.
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.
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.
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.
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.
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.
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.
As far as I know from
the research work
overseas
and my research work here,
bats with viruses
aren't getting sick.
The bats 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?
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.
♪♪
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.
♪♪
Mummified bats,
cabinets stuffed
with body parts...
The Dávalos Lab might feel
like something
out of a Frankenstein film.
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.
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?
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.
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.
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.
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.
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.
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.
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?
♪♪
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.
♪♪
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.
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?
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.
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.
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.
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.
♪♪
Matae's experiment
concentrates on
proteins involved in the
immune response,
and on one molecule in
particular: interferon alpha.
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.
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.
So we want to examine
and compare
the level of interferon
production
between human and bat cells
before any infection
actually occurs.
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.
In other words,
bats have adopted
a proactive strategy of defense.
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.
Human, for example,
our defense system
is switched off
most of the time,
until we see enemies,
and then we switch on.
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.
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.
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.
♪♪
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.
♪♪
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.
Hear?
Bang-bang-bang-bang-bang?
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.
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?
♪♪
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.
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.
♪♪
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.
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.
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.
♪♪
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.
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!
Gary goes just inside
the mouth of the cave
so he won't disturb the pups.
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.
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.
After about a month clinging
to the walls,
the young pups will attempt
their very first flight.
The slightest error
could be fatal.
It's really awesome to imagine
what it must be like
to take that first flight.
Looking down below...
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.
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.
Yesterday, they started flying
- about 7:30.
- 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.
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.
♪♪
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.
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.
Gary, the flight has started.
Are you in the air?
Jared, we're just taking
off right now.
We should be there
in 15 minutes.
Okay, roger that.
I'm gonna go ahead
and try to catch a bat.
Be sure to get a nice, young,
fluffy-looking one.
♪♪
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.
♪♪
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.
Okay, you can release!
Releasing her now.
Gary, I see the plane, I hope
the bat's coming with you.
Okay... okay...
Okay, okay... got it!
Got it, good.
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.
Can you speed up
just a little bit?
We're losing her,
we're losing her.
A little bit, a little bit.
Right on top, got it!
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.
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.
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.
♪♪
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.
They have, however, helped him
understand the physical effort
required for bats
to navigate the skies.
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.
♪♪
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.
Could this level of activity,
unrivaled by any other mammal,
somehow explain bats'
super-immunity?
♪♪
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.
♪♪
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.
Oh, my God, that's not bad!
I'm very impressed.
- Great spread!
- Yeah.
♪♪
♪♪
The experiment was performed
on four different bats,
and the result was exactly
the same for each one.
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.
♪♪
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...
One believer
is Linfa Wang, and he thinks
he's found out how.
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.
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.
For other mammals,
human included,
when the coordination goes,
you know, out the window,
and then when you over-defend,
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."
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.
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.
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.
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.
We are comparing
the inflammatory response
between human and bat cells.
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.
So, the bat have naturally
tempered NLRP3 protein,
so that the stress-related and
the viral-induced inflammation
always stay under control.
♪♪
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.
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.
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.
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.
♪♪
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 healthy living and longevity,
yeah.
♪♪
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.
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.
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.
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.
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.
As soon as they hear one,
they jump on top,
grab hold of it, and fly off.
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.
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.
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.
♪♪
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.
Sébastien Puechmaille
studies aging
at the Institute of Evolutionary
Science in Montpellier, France.
♪♪
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.
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?
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.
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.
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.
Isn't that beautiful?
Gorgeous.
Is that a baby?
We're gonna find out now
in a minute!
It looks like an adult.
- Do you want to bet?
- Yeah!
- You say a baby or an adult?
- Adult.
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?
Whether it's a drop of blood
or a small skin fragment,
the samples taken every year
are conserved carefully
in liquid nitrogen.
Do you see how
relaxed the bat is?
Yeah.
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.
♪♪
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.
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.
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.
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.
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.
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.
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.
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.
♪♪
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.
♪♪
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.
They are by far
the most fascinating
of all animals.
They are remarkable
and extraordinary creatures.
As a biologist, it's my job
to really tell people that
we, we need the bats.
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.
♪♪
I thought bats were
scary and creepy
and a little bit
kind of unpleasant.
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.
There is a virus
that is 96% similar
to this new coronavirus in bats.
Early research suggests human
picked up the coronavirus
from animals, possibly bats.
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.
They can really get infection
without getting sick.
Bats teach us lesson,
not to suffer autoimmune
disease,
diabetes, arthritis.
SÉBASTIEN PUECHMAILLE
Whether you capture a bat
that is two years old or 15,
or 20 years old,
you don't see any difference.
For the body size of these
animals,
they are way off scale
in terms of their longevity.
Bats hold the cure.
They hold our treatment.
Science is beginning to decipher
their strange powers.
Could these much-maligned
creatures hold precious secrets
for our own health?
"Bat Superpowers."
Right now, on "NOVA."
♪♪
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.
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.
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.
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.
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.
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.
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.
As far as I know from
the research work
overseas
and my research work here,
bats with viruses
aren't getting sick.
The bats 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?
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.
♪♪
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.
♪♪
Mummified bats,
cabinets stuffed
with body parts...
The Dávalos Lab might feel
like something
out of a Frankenstein film.
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.
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?
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.
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.
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.
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.
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.
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.
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?
♪♪
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.
♪♪
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.
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?
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.
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.
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.
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.
♪♪
Matae's experiment
concentrates on
proteins involved in the
immune response,
and on one molecule in
particular: interferon alpha.
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.
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.
So we want to examine
and compare
the level of interferon
production
between human and bat cells
before any infection
actually occurs.
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.
In other words,
bats have adopted
a proactive strategy of defense.
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.
Human, for example,
our defense system
is switched off
most of the time,
until we see enemies,
and then we switch on.
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.
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.
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.
♪♪
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.
♪♪
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.
Hear?
Bang-bang-bang-bang-bang?
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.
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?
♪♪
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.
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.
♪♪
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.
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.
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.
♪♪
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.
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!
Gary goes just inside
the mouth of the cave
so he won't disturb the pups.
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.
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.
After about a month clinging
to the walls,
the young pups will attempt
their very first flight.
The slightest error
could be fatal.
It's really awesome to imagine
what it must be like
to take that first flight.
Looking down below...
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.
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.
Yesterday, they started flying
- about 7:30.
- 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.
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.
♪♪
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.
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.
Gary, the flight has started.
Are you in the air?
Jared, we're just taking
off right now.
We should be there
in 15 minutes.
Okay, roger that.
I'm gonna go ahead
and try to catch a bat.
Be sure to get a nice, young,
fluffy-looking one.
♪♪
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.
♪♪
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.
Okay, you can release!
Releasing her now.
Gary, I see the plane, I hope
the bat's coming with you.
Okay... okay...
Okay, okay... got it!
Got it, good.
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.
Can you speed up
just a little bit?
We're losing her,
we're losing her.
A little bit, a little bit.
Right on top, got it!
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.
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.
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.
♪♪
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.
They have, however, helped him
understand the physical effort
required for bats
to navigate the skies.
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.
♪♪
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.
Could this level of activity,
unrivaled by any other mammal,
somehow explain bats'
super-immunity?
♪♪
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.
♪♪
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.
Oh, my God, that's not bad!
I'm very impressed.
- Great spread!
- Yeah.
♪♪
♪♪
The experiment was performed
on four different bats,
and the result was exactly
the same for each one.
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.
♪♪
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...
One believer
is Linfa Wang, and he thinks
he's found out how.
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.
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.
For other mammals,
human included,
when the coordination goes,
you know, out the window,
and then when you over-defend,
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."
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.
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.
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.
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.
We are comparing
the inflammatory response
between human and bat cells.
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.
So, the bat have naturally
tempered NLRP3 protein,
so that the stress-related and
the viral-induced inflammation
always stay under control.
♪♪
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.
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.
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.
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.
♪♪
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 healthy living and longevity,
yeah.
♪♪
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.
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.
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.
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.
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.
As soon as they hear one,
they jump on top,
grab hold of it, and fly off.
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.
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.
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.
♪♪
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.
Sébastien Puechmaille
studies aging
at the Institute of Evolutionary
Science in Montpellier, France.
♪♪
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.
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?
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.
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.
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.
Isn't that beautiful?
Gorgeous.
Is that a baby?
We're gonna find out now
in a minute!
It looks like an adult.
- Do you want to bet?
- Yeah!
- You say a baby or an adult?
- Adult.
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?
Whether it's a drop of blood
or a small skin fragment,
the samples taken every year
are conserved carefully
in liquid nitrogen.
Do you see how
relaxed the bat is?
Yeah.
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.
♪♪
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.
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.
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.
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.
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.
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.
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.
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.
♪♪
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.
♪♪