♪♪ ATTENBOROUGH: Mexico is a land of astonishing natural riches.

It's home to a great variety of life.

And it's also home to tequila.

Made from the mighty agave plant, this beverage has a secret.

Without a special bat, there would be no tequila.

And this bat has been put in terrible danger.

But it has a defender -- bat biologist Rodrigo Medellin.

MEDELLIN: There's little bats, there's big bats, there's short-snouted, long-snouted, big eyes, little eyes, long ears, short ears, every type of bat.

ATTENBOROUGH: He has devoted 20 years to saving Mexico's tequila bats.

Every year they make an incredible journey from the far south of Mexico to the U.S. border.

This year Rodrigo is going to join them to find out if his work has been successful and if the bats and tequila have been saved.

MEDELLIN: In Mexico and in other places, because of what I do, they call me the "Bat Man."

So be it.

I am the Bat Man.

♪♪ ♪♪ ATTENBOROUGH: Rodrigo Medellin was not like other children.

While his friends kept gerbils and hamsters, Rodrigo's pets were vampire bats.

MEDELLIN: I remember when I was a kid I would keep vampire bats in the bathroom of my home, feeding them blood from cows or for me sometimes, keeping blood in the fridge so that I could feed the bats every night.

That was not easy to withstand, and still my parents let me do that.

ATTENBOROUGH: It was the beginning of a lifetime's obsession.

But there was one particular bat that seized his imagination, a bat important not only to Rodrigo, but to the world.

MEDELLIN: My first lesser long-nosed bat came into my hands when I was 15.

We knew nothing about it.

Then we found out that they were really endangered.

We were looking at roosts that were known to have many thousands of lesser long-nosed bats, and when we visited them, they only had a few hundreds or none.

That immediately told us that they were in trouble.

So this is one of my best friends.

This is a lesser long-nosed bat.

This is an amazing animal that migrates for thousands of kilometers.

It's a small but powerful flier.

Look at this amazing wing.

This is what made bats so successful in the night skies -- long-fingered hand here and a very long arm here.

You can see both vein down here and a series of muscle stretches here.

It's very much alive, so that they can control making it broader or narrower.

That makes them masters of the air.

It's getting ready to start a really exciting time, a really demanding time, a really dangerous time, too, which is migration.

ATTENBOROUGH: The migration of this tiny endangered bat is one of the greatest in the animal world.

This epic journey happens at night, so it's taken Rodrigo 20 years to work out their route.

Over his life, he has discovered many of the roosts they use on their 2,000-kilometer journey and protected them, one by one.

The entire migration is powered by nectar.

MEDELLIN: I'm gonna give it a bit of sugar water here.

This incredible tongue that they have is the perfect instrument for them to reach into deep flowers, like agave flowers.

It's incredible that an animal this big can do what these guys do.

I love them because of that.

ATTENBOROUGH: Rodrigo is about to immerse himself in the bats' world.

By tracking their entire migration, he wants to see if he's achieved what many thought impossible -- saving the tequila bats from extinction.

The stakes are high.

Their fate is tied to Mexico's most famous export.

MEDELLIN: As a Mexican, I'm proud of my country.

And part of the Mexican spirit is a beverage that is called tequila.

[ Metal scraping ] ATTENBOROUGH: These spiky plants are the source of tequila.

MEDELLIN: Tequila is a very important part of the Mexican economy, and it is owed to bats.

Bats provide pollination for the tequila plant, the agave plant.

♪♪ ATTENBOROUGH: Mexico relies on tequila.

Over a quarter of a billion liters were exported last year.

Every plant is harvested by hand, by men called jimadores... ...in a trade passed down from father to son.

The agaves are planted where they've always grown -- in the flight path of the bats.

♪♪ ♪♪ MEDELLIN: What agaves do is they grow and grow and grow, and then when the time comes, they send this amazing shoot, huge flowering stalk, up into the sky.

They invest all of their energy that they have accumulated over 15 years into one single reproductive event that basically costs them their lives.

The link that they formed has been here for millions of years.

Agaves rely on the bats to move their pollen.

Bats rely on agaves so that they can survive.

We could not have this amazing product if it wasn't for the bats.

And I can't help but think of the bats and thank the bats for the incredible service they give us.

♪♪ ATTENBOROUGH: Without the bats, there would be no tequila.

♪♪ But 20 years ago, their populations had crashed.

Hundreds of thousands of bats had died, and the future of tequila was suddenly in danger.

Rodrigo had to take action.

The tequila bats were being killed by people because of the reputation the vampires had given them.

MEDELLIN: In the 19th century, there was this author who wrote a book entitled "Dracula."

That really touched the imagination of people around the world, and that has turned bats into monsters, unfortunately.

♪♪ ATTENBOROUGH: Bats were so hated in Mexico because of their association with evil that people would hunt them down and kill them, burning them in their caves.

Their populations crashed.

MEDELLIN: To this day, people are afraid, saying that they are filthy and that they are everything bad in the world.

That is really not the case at all.

ATTENBOROUGH: Bats are actually very clean.

The same can't be said for the caves they live in.

Rodrigo's mission to save his tequila bats has taken him into their world.

MEDELLIN: It's bat guano all over.

Under that layer of bat feces is a whole layer of living insects -- beetles, beetle larvae, fly larvae, moth larvae -- they are just moving everything, everything, everything.

You look, and everything is moving.

ATTENBOROUGH: This is one of the many caves Rodrigo has protected from those who could destroy the bats inside.

But the start of this great migration isn't deep underground where you'd expect.

Our story begins in the Pacific Ocean at the uninhabited islands of Chamela.

[ Wind whistling ] [ Boat engine running ] Rodrigo has traveled here from his home in Mexico City.

He's heard reports that the bats have been gathering here, but he's never been to this cave before.

[ Insects scuttling ] To his horror, it's full of cockroaches.

He hates cockroaches.

MEDELLIN: Whoa!

So many cockroaches.

And I almost fell on them!

Eeh, ugh, oh!

ATTENBOROUGH: But he's astonished by what he finds.

MEDELLIN: This is incredible.

So many lesser long-nosed bats, all around me.

It's so good to see that their numbers are stable and big.

ATTENBOROUGH: The tequila bats have come together from all across Mexico with one thing on their minds... ♪♪ ...mating.

♪♪ ♪♪ MEDELLIN: They're mating here right now, and this is a very well-protected cave.

The ocean takes care of that.

ATTENBOROUGH: While Lucas the boatman tucks into some oysters, Rodrigo pushes deeper into the cave and the source of the bats' aphrodisiac.

MEDELLIN: Oh, yes.

Big male, which is what we expected in this cave.

It's full of males getting ready to reproduce.

Such well-tempered bat, with big testicles ready for action, loaded with sperm, and ready for the females that are gathering here in this cave, and this should have a patch on its back.

Oh, yeah, the patch is there.

Very oily.

I can feel it with my finger here.

That patch is put there by the males.

They put feces and urine and saliva there, and that is very attractive to the females.

Females are gonna come and take a whiff of that and just fall in love with this guy.

This boy is ready to mate, and it's time to let him go so that he can do his deed.

There you go, my friend.

♪♪ ATTENBOROUGH: On the roof of this cave, an extraordinary mass seduction is taking place.

Once the females find a male whose sex potion entrances them, they'll choose him as their mate, and in three months, 1,500 kilometers away, a single baby bat will be born.

It may be alluring for the females, but for Rodrigo, the smell is overpowering.

MEDELLIN: This is a really stinky cave, and there are lots and lots of bats here, lots of them everywhere!

This is certainly -- ooh!

This is certainly a challenging cave to be in, to be sure.

ATTENBOROUGH: Eventually the smell and cockroaches are too much, even for the Bat Man.

The bats will stay on this island for weeks, mating and building their strength before they continue on the next stage in their migration.

It will be perhaps 30 sunsets until then.

And each evening is a changing of the guard... ♪♪ ♪♪ ...as the birds of Mexico head home to roost.

♪♪ All across this enormous country, bats are about to reclaim the night.

Nowhere is this more spectacular than the Bat Volcano of Calakmul.

Predators are gathering.

It's called the Bat Volcano because every night it erupts.

[ Bats squeaking ] ♪♪ ♪♪ This is one of the greatest bat colonies on Earth.

Perhaps as many as 3 million bats live here.

To avoid being eaten, they form a living tornado 200 meters tall.

In this whirling mass, it's almost impossible for their predators to choose a target.

But the bats must head to their feeding grounds, and they start to peel off across the forest.

♪♪ Now the hunters can strike.

♪♪ One bat narrowly escapes.

Others aren't so lucky.

Bat falcons and brown jays also swoop in to make their kills.

♪♪ But nothing can dent the swarm.

♪♪ They're heading for the cornfields across the forest.

There, they will devour 20 tons of insect pests... ...like this hatching armyworm moth.

Each moth can produce hundreds of hungry caterpillars.

And, unprotected, the crops would be doomed.

[ Dogs barking ] Most Mexicans don't realize they owe not only their tequila, but also their corn, to bats.

MEDELLIN: Mmm.

Thanks to bats, we're eating this.

ATTENBOROUGH: Rodrigo's main weapon to defend the bats is education.

His teams work in over 30 states across Mexico, and he never misses a chance for a bit of bat PR.

[ Both speaking Spanish ] MEDELLIN: Muchas gracias.

Bueno.

♪♪ You can see it in the eyes of people when you talk to them and it makes sense.

All of a sudden, everything makes sense.

Their frame of mind changes, and they're bat friends from then on and they propagate the message.

They talk to people in the house.

They talk to people in the office, in school, etc.

And little by little, the situation goes snowballing and really, really changes the panorama for the bats.

I can turn them around in 10 minutes, in 15 minutes.

I give them the facts.

I give them the evidence.

I give them the images.

ATTENBOROUGH: Over 20 years, Rodrigo and his team have converted the people whose land the bats rely on from potential destroyers to bat defenders.

Now, three weeks later, the female bats are pregnant, and their migration is starting.

Before they spread out across Mexico, Rodrigo has a rare chance to count them.

MEDELLIN: This is an amazing thing.

I can't see anything.

So this thermal camera can tell me what's going on there.

Using this technology, we can estimate, how many bats do we have in this cave?

I'm guessing about 40,000 lesser long-nosed bats.

The spectacle is incredible.

ATTENBOROUGH: The tequila bats start moving north, crossing cities, and people oblivious to their journey above.

By day, Rodrigo is hot on their tails.

The bats travel over an ever-changing Mexico.

And always they pass over us.

The path the bats and Rodrigo must now take lies between the mountains of the Sierra Madre and the sea.

This fertile land is called the nectar corridor... ...because here, every year, billions of flowers open at night.

The bats must feed on these constantly to fuel their journey, otherwise they'll die.

And they have to time it perfectly.

MEDELLIN: Over millions of years, the bats have learned by trial and death to track where the nectar is going to show up next.

Bats are early or bats are late, plants die and bats die.

ATTENBOROUGH: What the bats miss is hoovered up quickly in the daytime in a fiesta of hummingbirds.

But both hummingbird and bat face an uncertain future.

MEDELLIN: Humans are affecting every last corner of the world in many different ways, some ways that we still don't understand.

Biological diversity is under threat from many angles, and not all of them are manageable or reversible by humans.

ATTENBOROUGH: Mexico is developing fast.

The land the bats rely on is being swallowed, and nature is being destroyed.

But because of Rodrigo, at least some is safe.

30 years ago, he was asked to assist the new government to devise laws to save the wildlife of Mexico.

Land-owners, the Mexican people, worked as partners to create a vast network of linked nature reserves, made from their private and the government's public land.

MEDELLIN: I've worked with small groups, big groups, individuals, in the government halls, everywhere.

All we need is a little bit of information, and people are gonna change about bats.

ATTENBOROUGH: Now over a quarter of Mexico is protected land.

Where other countries have lost much of their wildlife, Mexico is a rare success story.

But nature in Mexico is still threatened, and Rodrigo is still pushing to save more.

This cave is one of the safe ones, protected by local families who share the land.

Down here, Rodrigo and the bats feel safe.

MEDELLIN: The peacefulness in here is really overwhelming.

It's really nice.

The only sound around you are the bats flying around you.

This here is a bed of bat guano.

I could just lie down here and take a nap, and it would be a very nice nap.

I just absolutely love it.

ATTENBOROUGH: But even in their deepest sanctuaries, where their bodies lie undisturbed by any scavenger, they're never quite secure, for this cave is called "the cave of the serpents."

MEDELLIN: Somehow, a group of snakes have learned that they can catch their food here.

This is something I have never seen before.

These are rat snakes, but they're getting used to eating bats inside the cave as they come out.

ATTENBOROUGH: And as darkness falls outside, the bats prepare to leave.

From much deeper underground, they start to throng the narrow passages towards the surface, and the snakes start to emerge.

♪♪ MEDELLIN: Look at that!

This snake is deep into the cave where the bats are supposed to be completely safe from predators.

Not so.

[Snaps fingers] Dinner.

ATTENBOROUGH: The bat dwarfs the snake's head.

To swallow it, the snake must dislocate its jaw.

MEDELLIN: This is one more danger that bats face along their migration, and still, they're there and surviving.

♪♪ [ Thunder crashes ] ATTENBOROUGH: And just when the bat populations look safe, disaster strikes.

[ Thunder crashes ] Within weeks of each other, not one but two hurricanes hit Mexico and batter the entire Pacific coast.

This is a threat beyond even Rodrigo's control.

He loses the tequila bats.

Across the country, he sends his students to everywhere the bats have ever been found.

For three weeks, they search day and night.

This has never happened before.

♪♪ ♪♪ MEDELLIN: Okay, so that bats are not here.

Well, I don't know.

♪♪ ♪♪ ATTENBOROUGH: If many of the bats have been killed, the future for their species is bleak.

♪♪ ♪♪ MEDELLIN: The way I feel right now, the trail is getting cold.

I'm not sure if we're gonna find them.

Our only hope is to keep poking and looking in every little piece of bat habitat that we know of to see if they are there.

ATTENBOROUGH: It's a tense time for Rodrigo.

He puts out rewards for any leads.

At last, one of his students thinks they've seen a tequila bat in a cave called Las Vegas.

♪♪ They block the exits, and he heads in alone.

♪♪ ♪♪ Finally, he emerges... triumphant.

MEDELLIN: I found them.

It took weeks of searching everywhere.

It took two hurricanes to move the bats around so we could not track them, but they're here.

I got like, uh, maybe like 10, so the population is healthy.

Another dot in the migration of this species.

I'm so relieved.

I found them.

[ Sighs ] Oh, wow.

[ Water splashing ] Oh, look at this.

This is a pregnant female.

Her wings are in great shape.

Wow.

I can feel the head right here and the rump over here.

This is the baby right here.

The baby is really big.

I can't imagine the energy that this bat has spent just flying around with a fetus growing inside her.

Thank you, Mom.

You're ready to go.

[ All speaking Spanish ] ATTENBOROUGH: With proof that there are bats here in numbers, he can get legal protection for the cave.

The tequila bats have another vital place of permanent safety.

For Rodrigo, it's time to visit some old friends.

♪♪ There are over 1,200 species of bats in the world.

♪♪ Three are vampires.

♪♪ And two of these species live in this cave.

♪♪ MEDELLIN: I got you!

I thought this was a common vampire bat, but it's a hairy-legged vampire bat.

They're not common at all.

This hairy-legged vampire bat feeds almost entirely on mammal blood in this area here.

They have a really soft side, which is that they share blood.

No vampire bat can afford to go one night without feeding.

We found out that they come back from their foraging and regurgitate a little bit of the blood for the guys that didn't feed that night.

So, basically, they have a blood cooperative going in every vampire bat colony.

They are nice.

I mean, look at them.

Really nice.

[ Insects chirping ] ATTENBOROUGH: This might look like the stuff of nightmares, but the cow is oblivious to the vampires feeding on its back and sides.

Vampire teeth are so sharp that the cow doesn't feel their bite, and an anti-coagulant in their saliva keeps the blood flowing.

They don't suck, but lick up the flowing juices.

Often they will return to feed on the same animal night after night.

Regrettably, Rodrigo can't stay for dinner.

He's back on the trail of the tequila bats.

He heads north to the end of the nectar corridor and the edge of the Pinacate desert.

MEDELLIN: The Pinacate desert is one of the great deserts of North America.

It is part of the Sonoran Desert and, as such, is part of the driest desert in this continent.

It's one of the most challenging places on Earth to make a living as a human being or survive as a species.

This place has been a desert for at least 100,000 years.

ATTENBOROUGH: The bats are aiming for a cave deep in the heart of this desert, in the Badlands just south of the U.S. border.

♪♪ There are no agaves to feed off en route.

Instead, the tequila bats, nearing the end of their three-month pregnancy, must seek the flowers of the giant columnar cactuses.

MEDELLIN: These flowers accommodate almost half the bat's body into them.

It means millions of years of evolution in which the flowers have become perfect receptacles for the bat's head and snout and tongue.

And a very long tongue of the bats goes into those flowers and lick the nectar out, and they come out completely covered with pollen.

They move out, they go to another columnar cactus, and there's pollination.

ATTENBOROUGH: Because he knows the bats will come to the cactus flowers, Rodrigo has a chance to solve a puzzle that's long been on his mind.

How far can they fly in one night?

♪♪ MEDELLIN: It is a female, very lively, in very, very good health.

We're going to mark it with a blue powder.

ATTENBOROUGH: Rodrigo coats the bats he catches in harmless UV dust, which they will lick off and digest.

MEDELLIN: We keep the head out so that the powder does not affect its senses.

That should be enough.

ATTENBOROUGH: The bats will now head on to their roost, where, within a day, the glowing dust they've licked will pass through their system.

And if Rodrigo can find a glowing bat dropping there, he can prove how far they've flown, at least in theory.

No one has tried this before.

[ Insects chirping ] ♪♪ At daybreak, 50 kilometers from the cactuses, Rodrigo finally arrives at the most important cave, the end point of their long journey -- the birth cave of the tequila bats.

MEDELLIN: This cave is the largest colony that this bat has anywhere in the world.

ATTENBOROUGH: It's Rodrigo's great hope that enough bats have made it here to sustain their population.

The future of the species depends on what will take place in this ancient volcano.

MEDELLIN: We cannot get in the cave during the day.

We would create chaos in the worrying females that are taking care of their babies.

♪♪ ♪♪ ATTENBOROUGH: Rodrigo must by wait by the cave mouth.

Night falls.

♪♪ And then... ...at first a trickle, then more emerge.

At least some of the bats have made it.

It's a tremendous relief for Rodrigo.

♪♪ Now the mothers have left the cave to find food, it's safe for Rodrigo to go inside.

♪♪ They turn on their UV torches and carefully comb the cave.

[ Instruments clanging ] MEDELLIN: Ah!

Blue poop.

This is proof that these bats are really long-distance fliers doing 50-kilometer one-way trips, and then coming back every night.

This is a really good find, confirmation.

ATTENBOROUGH: To fly to the cactus where Rodrigo dusted it and back is a 100-kilometer round trip.

No one suspected the bats could fly so far.

MEDELLIN: This is a spotted skunk, and it's coming out now, I have never seen it before.

Look at the incredible pattern and the huge feathered plume advertising that it is about to spray us.

But it chooses to go off into the dark.

ATTENBOROUGH: Rodrigo moves far deeper into the maze of the volcano than he's ever been before.

MEDELLIN: Phew!

We can check on the reproductive success by gauging how many babies are hanging from the roof of the cave.

♪♪ ATTENBOROUGH: At last, far below the desert surface, the bats' secret -- their nursery.

MEDELLIN: This is a group of babies, and there's a mix in their ages.

Most of them are about a week old, and a very few one-day-old and two-day-old babies.

It's always good to see them.

ATTENBOROUGH: These are the first babies to be born of what will hopefully be hundreds of thousands.

The future of the entire species hangs in this cave.

MEDELLIN: They synchronize their births so that everything happens in the space of two weeks, three weeks, that's it.

You have twice that many bats in there.

This is -- this is huge.

Oh, yeah, this is a good spot for the camera.

ATTENBOROUGH: Rodrigo sets up remote cameras.

He can't stay when the mothers return, so he's never seen what happens here during the day when they're reunited with their pups.

MEDELLIN: This is a very young baby, one day old, two day old.

This is not a good place for the mother to leave this baby.

ATTENBOROUGH: The pup is so young, its umbilical cord is still attached.

It's yet to grow the fur and fat that will keep it warm.

MEDELLIN: These babies are tiny.

At this age, they cannot keep their temperature up.

They have to be surrounded by dozens or hundreds of other babies so that they keep the heat in place in what we call nurseries.

But this poor guy is here by himself.

If his mother doesn't come soon, his temperature is gonna drop and he's gonna be in trouble.

Death is always part of the natural history of these species, but I always worry about the fate of these little guys.

ATTENBOROUGH: Soon, the mothers will start to return from across the great desert wastes.

It's time for Rodrigo to leave.

♪♪ In the hours before dawn, the bats flood into the ancient volcano like an eruption in reverse.

♪♪ As the day passes on the desert surface, the cameras record the bats' hidden lives deep underground.

At nightfall, once the females have left again, they can retrieve the footage.

It's a long night watching through the many hours recorded.

MEDELLIN: This is a -- this has to be at around 7:00 or 8:00 p.m. Nobody has seen a nursery in the process of building up the numbers of babies that are left behind by the mothers.

MARINA: She's pregnant, yeah?

MEDELLIN: No.

This one?

MARINA: No, this one.

ATTENBOROUGH: And then... MEDELLIN: Oh, look at this!

MARINA: She's having a baby!

MEDELLIN: Having a -- She's having a baby!

MARINA: [ Squeals ] MEDELLIN: iNo es possible!

The baby's coming out!

[ Both speaking Spanish ] This is incredible.

She's licking, scratching, and again.

MARINA: Wow.

ATTENBOROUGH: The camera has captured something never seen before.

MEDELLIN: Look at the tiny forearm.

MARINA: This is the face?

MEDELLIN: Yes.

ATTENBOROUGH: First its head, then its wing emerges.

Then suddenly the baby is out and clinging to its mother.

MEDELLIN: The wings are protecting the baby so nobody can come close to the baby at all.

ATTENBOROUGH: We catch a glimpse of the newborn pup's face as its mother cleans it in her fingertips.

MEDELLIN: Look at that!

Ooh!

Baby was slipping away from the mother.

She -- the baby must be very, very slippery, and it's slipping down away from the control of the mother, so she catches it with the wing.

ATTENBOROUGH: The mother quickly positions the baby on her teat for its first feed of her milk.

MEDELLIN: That is amazing.

There's a few mothers.

There's one, two, three, four.

But this is all babies.

ATTENBOROUGH: Over the next few days, the colony swells with thousands upon thousands of new babies.

MEDELLIN: This is the flagship colony that is helping me understand what is the actual conservation status of that species.

If we multiply that one birth hundreds of thousands of times, tells me that the species has recovered.

ATTENBOROUGH: Rodrigo could never have dreamed 20 years ago that he'd be seeing such a recovery.

His tequila bats have come home to roost.

MEDELLIN: Our work as conservation professionals is not to put as many species as we can in the endangered species lists.

Our work is to work as hard as we can for long as it's needed -- as long as it's needed only -- to recover that species.

ATTENBOROUGH: Finally, Rodrigo is ready to make an extraordinary announcement.

MEDELLIN: There's places where I have to be in big meetings.

You have to address the world.

Before that happens, I picture myself in a cave, in the darkness, in the quiet, in the peace of a cave.

Everything is great then.

ATTENBOROUGH: At the Ministry of the Environment in Mexico City, journalists and ministers pack the room to hear what he has to say.

[ Applause ] MEDELLIN: [ Speaking Spanish ] [ Applause ] ATTENBOROUGH: Thanks to the work of Rodrigo, his team, and hundreds of others across this country, the lesser long-nosed bat is the first species in Mexico to be officially saved from extinction, and it will be removed from the endangered species list.

MEDELLIN: This is a clear indication that our work is actually having a good impact in the world.

ATTENBOROUGH: His method of combining research, law, and community education has meant every single bat colony has either stabilized or increased.

His techniques are now being applied with further success to save endangered species of all kinds across Latin America and the world.

Rodrigo really is the Bat Man.

MEDELLIN: This is a great day for the lesser long-nosed bat.

There's a lot of work to be done, but first, it's time to celebrate.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this "Nature" program, visit pbs.org.

♪♪ ♪♪