Original subtitles

NARRATOR It's one of the most profound mysteries in the natural world.

An amazing transcontinental odyssey.

The migration each year

of millions of monarch butterflies

from Canada, across America, to Mexico.

CHIP TAYLOR: You've got a butterfly that's originating in Toronto,

or it's originating in Detroit, Michigan

it's coming down

maybe even Winnipeg, and it's moving south,

and somehow, it finds its way to Mexico.

Could you do that?

NARRATOR: Starting from a tiny caterpillar,

blossoming into a beautiful butterfly,

these delicate creatures will fly thousands of miles

in a feat of endurance and navigation

unlike anything else in nature.

LINCOLN BROWER: They've never taken a long flight in their lives,

and they're on their way to an area

that they've never seen before.

Somehow they're recognizing landmarks, or following streams, I

or following the sun.

They're following something.

NARRATOR: They're on their way to a remote area

high in the Mexican mountains,

and they get there every year at exactly the same time.

BILL CALVERT: Butterflies have dazzled humans for millennia.

It's a beautiful little creature,

and on top of that, it migrates 2,000 miles.

And this just staggers the mind.

BROWER: I think the monarch butterfly

is one of the most magnificent animals in the world.

And it's unique in terms of the entire animal kingdom.

There's nothing like it.

NARRATOR: Next on NOVi.

The Incredible Journey of the Butterflies.

Captioning sponsored by EXXONMOBIL, DAVID H. KOCH,

the HOWARD HUGHES MEDICAL INSTITUTE,

the CORPORATION FOR PUBLIC BROADCASTING

and VIEWERS LIKE YOU.

Major funding for NOVA is provided by the following:

ExxonMobil... taking on

the world's toughest energy challenges.

And by:

And...

And by the Corporation for Public Broadcasting,

and by contributions to your PBS station from:

NARRATOR: On a late August morning

just north of Lake Huron in Canada,

a miracle of nature is about to unfoldo.

This tiny caterpillar is destined

to become a monarch butterlly.

In one of the most amazing transformations

in the animal world,

the caterpillar will outgrow and shed its skin four times.

The fifth time,

the caterpillar disappears.

It's transformed into a chrysalis,

a delicate case within which

a completely new being takes form.

After about ten days in the chrysalis,

the new creature is complete.

All traces of the caterpillar are gone.

And in its place is a butterfly

with four delicate wings.

But the newly developed monarch butterfly

must wait a few hours for its wings to harden.

And then, finally, it can fly.

This particular generation of monarch butterflies is special.

Every year,

about 100 million of them begin an astonishing migration.

Coming from Southern Canada

and the Northeastern United States,

each butterfly,

starting on its own,

flies about 2,000 miles,

arriving two months later in Mexico.

Their trip is part of a carefully-timed cycle

that began three generations back

when a group of monarchs

left Mexico at the end of the winter.

They flew as far north as the Gulf states,

mated and died.

The second generation flew to the Northern United States.

[There, they, too] mated and died, I

living only about a month.

Their offspring-the third generation...

Icompleted the last leg of the journey to Canada

also surviving only abouta month. .

But the fourth generation will live almost nine months.

And they'll fly all the way back to Mexico

in one epic trip.

It's an amazing natural cycle that,

so far, eludes explanation.

IThe mystery starts at the very beginnin

of the trip, because no one knows

exactly what triggers

the exodus from Canada.

LINCOLN BROWER: Well, when the monarchs leave Canada,

they have a 2,000-mile trek ahead of them, at least.

They're freshly hatched butterflies,

they've never taken a long flight in their lives,

and they're on their way to an area

that they've never seen before.

Somehow, they're recognizing landmarks,

or following streams,

or following the sun,

or following something.

We just don't know exactly how they do I.

It's really an incredible journey.

NARRATOR: A monarch's wingspan is just under four inches.

And they weigh less than one-fifth of an ounce. .

So how they survive their marathon migration

is another mystery.

They only fly when conditions are perfect.

lf it's too cold, they get sluggisjj

and can't flap their wings.

If it's too hot,

they stop flying so they don't get overheated.

They must also stop often for nectar and water.

But every time they land,

there can be enemies lurking.

Bad weather is also the monarch's enemy.

A rainstorm can be deadly.

If it survives enemy attacks and bad weather,

a monarch that started in Canada

has to fly at least jlesajpy j

to get to Mexico.

The physical effort this requires is remarkable

for a creature so smalli with such fragile wings.

DAVID GIBO: Butterflies are the worst possible

body form for trying to makel a long-distance migration.I.

They're simply a bad design.

Every time they flap their wings, they're using

energy at least 20 times the rate

than when they're not flapping it.

So they're just burning their fuel up at a great rate,

much like, say, a helicopter might.

And so, they have to compensate

for their inadequacies by soaring.

Soaring is gliding

in rising air, much like I'm doing right now. I.

The sun heats the ground,

the ground heats the air above it.

As the air heats,

it expands and becomes lighter,

and begins to rise.

And pretty soon, you have a column of rising air.

That's a thermal.

Under good conditions, you can maintain

the altitudeyou'reat, or even can gain altitude.

A more helpful maneuver is to circle in it.

And you see hawks doing this

and vultures doing this all the time.

Circling the thermal, ying within it... I

and this seems like a wonderlul free ride, and it is.

Soaring's the key to them getting to Mexico.

NARRATOR On the shores of the Great Lakes,

just days into their journey,

the monarchs face their first geographic hurdle.

Miles of open water

and constantly shifting winds.

As the monarchs are migrating out of Canada,

they hit the Great Lakes, which are a barrier.

They can't see across them.

NARRATOR: With no land in sight,

monarchs use their finely tuned

sense of the direction of the wind to carry the

across the water.

If wind from the south, a headwind,

threatens to blow them off course

they stop and wait.

When they sense that the wind has shifted in their favor,

they fly on.

The ultimate destination of their incredible journey

is a tiny area about 60 square miles,

and 10,000 feet high in the mountains of Mexico.

IThe local people, I called the Mazahua,

have lived here for hundreds of years.

They believe monarchs epresent the spirits I

of their ancestors.

And the arrival I of the butterflies

each year, begins a celebration

called the Day of the Dead.

ALICIA GARCIA: It's a very beautiful time

when the butterflies arrive.

The butterflies would come down, surround us.

Coming down to give the final touch

to the tradition of the Day of the Dead.

For those who live here, it's our belief,

from when I was a child, I we would say they

“the souls of our departed loved ones.”

Every year I make an altar.

We put these things here

because when our ancestors were alive,

this is what they liked.

That's why one waits for their arrival:

To give them this offering.

HOMERO ARIDJIS: The legends of the people

that live near the ocean and the mountains,

are important to them.

For us, there is a sense of the space.

The freedom to fly,

to fly with imagination,

to fly just like a butterfly.

NARRATOR Homero Aridjis is one of Mexico's best-loved writers.

He grew up in these hills

and has fought to preserve them for monarchs.

Every year, Lincoln Brower comes here

to continue his study of the monarch migration.

When you were a young boy, Homero

you used to go up to see the butterflies? I.

Yes. Every year, we came

with the schoolchildren.

And for us,

it was one of the most fantastic spectacles of the year.

To go to the plain of the Mule

to see the butterflies.

Butterflies also came to town.

They were across the street.

They flew through the town?

Exactly.

They were looking for water.

Sometimes they was in your house.

But there were millions of butterflies.

And for us,

it was a spontaneous miracle

to see butterflies here, in the Cerro del Campanario.

But we didn't know that they were coming from Canada,

across the United States.

And the Canadians and Americans didn't know

that they were coming to these places.

NARRATOR: It was not until 1975

that scientists discovered the full extent

of the North American migration,

when butterflies that had been tagged in Canada

were found spending the winter here.

These monarchs return each year

to 12 specific sitesi in these mountains.

This is their only destination in the world.

It's a perfect environment for the butterflies

because of the unique climate.

BROWER: We're talking constantly

about this micro-climactic envelope.

About 3,100 meters,

usually on southwest-facing slopes.

If you imagine the forest as a blanket

that protects the butterflies by keeping the heat in,

and also think of it

as an umbrella that keeps the rain out,

and the tree is like a hot water bottle.

It's radiating heat out through the bodies of the butterflies.

So, when the temperature drops down really low,

you'll see millions of monarchs

just festooning these beautiful trunk clusters.

If you think about it,

the bigger the tree, the more heat it holds.

So this is an argument

for maintaining the forest in its native state.

To let the trees get as big as they can,

and the butterflies will be protectedi

during those cold periods.

NARRATOR: Monarchs live in other parts of the world, in warm climates.

But only Canadian and North American monarchs

migrate such an incredible distance

to avoid the certain death of a cold winter.

And exactly how they navigate

from Canada to Mexico is another unsolved mystery.

Scientists only have a few clues.

One theory is that the butterilies navigate

by following a specific angle of the sun

in relation to the earth.

Another theory proposes

that the earth's magnetic field

may provide a subtle 9fljji9j gir.

And recently, biologists discovered specific cells

in the butterfly's brain

that regulate their internal clock

and help keep them on course.

At the University of Kansas,

Chip Taylor studies the forces at work

in the monarch migration.

TAYLOR: You've got a butterfly that's originating in Toronto,

or it's originating in Point Pelee, j

or it's originating I in Detroit, Michigan,

it's coming down

it's maybe even Winnipeg, and its moving south,

and somehow it finds its way to Mexico.

Could you do that?

And so now you need to tell

whether or not it's a male or a female,

and so, this picture...

NARRATOR: In 1992, Taylor started a project called Monarch Watch.

Are there any over here? No.

So you know that one's a girl.

So let's check out iyour butterfly. I.

NARRATOR: School children and teachers tag butterflies

from all over the Northeastern United States.

The tags don't hurt the butterflies,

and don't affect their ability to fly.

Oh, there he goes.

NARRATOR: But when tagged butterflies are recovered

at various stops along the way to Mexico,

tracing back the information on the tags

helps reveal their flight path,

and their traveling speed.

Let her go.

NARRATOR: And one of Taylor's tagging experiments

had a surprising outcome.

TAYLOR: We ran some experiments a few years ago.

So we took butterflies,

and we transferred themi Jngton, D.C.,

and initially, when we released them

in Washington, D.C., they behaved as if

they were still in Kansas.

NARRATOR: The butterflies who'd been moved to Washington started out flying

in the same direction they would have taken to Mexico

from their original home in Kansas,

almost directly south.

But starting from Washington,

that flight path would never get them to Mexico.

Amazingly, after a few days,

the displaced monarchs somehow reoriented themselves

and changed course to a strong southwest heading.

That meant that even starting from an unfamiliar location, j

they still ended up in the right place in Mexico.

TAYLOR: Now this is really exciting stuff,

because what this says is that somehow

this butterfly is acquiring celestial information,

perhaps magnetic information,

and it's integrating those

and remodeling the physiology of the system

to have a different vector,

to have a different direction from where it came from. I.

Now that's pretty cool.

NARRATOR: By late September,

aboutamonth I into the migration

the monarchs are gathering into huge flocks.

By this time,

they've traveled more than halfway across America...

over the industrial belt...

through small Midwestern towns...

across the Great Plains...

and finally, approaching the Southwest.

No one knows how many monarchs die along the way.

But if they make it to Mexico, there's another threat.

Their destination in the Mexican mountains...

the forests that will keep them alive over the winter...

is in danger.

It's, like, you see alli these trees, Lincoln?

Yeah.

Before, there were hundreds of thousands,

land now, you can count them.

And then, they're all...

You see very tall and very wide.

NARRATOR: In 1986, the Mexican government protected some sections

of these mountains as official sanctuaries

for the butterflies for the winter months.

But that meant some parts

of the forest local people had depended on for income...

through legal logging operations...

were suddenly off-limits.

The result was an unexpected new threat to the monarchs...

illegal logging.

BALTAZAR GUTIERREZ: We all have needs,

but those that cannot meet their needs...

they are the ones doing the clandestine logging.

WOMAN: They come at 2:00 or 3:00 in the morning.

They go down in the night

to sell the wood.

NARRATOR: Mexican police patrol the forest,

but have not been able to stop illegal logging.

The World Wildlife Fund pays villagers

to try to stop the destruction,

but they are no match for the dangerous forces at work.

EDUARDO SALINAS: Logging is clandestine and involves dangerous people.

So you cannot go around telling the world about it.

Sometimes you find yourself alone,

and even with the police, you can be left alone.

They will follow you to kill you.

It's not that easy.

MAN: Who would allow their children to die of hunger?

We know that it's important to preserve the forest

for the butterflies.

But because of our need, we have not been able to do it.

BROWER: We're talking about hundreds of hectares of forest

being leveled and then burned.

I have been told that the reason they burn them

after they log them is, I “to destroy the evidence

that they cut them,”

which sort of eludes my thinking, completely.

Even this small-scale logging operation is destroying

the capacity of the monarchs to use those sites.

There are so few trees left,

and even if they did sit on the ones that were left, j

they'd freeze to death.

NARRATOR: With the sanctuaries shrinking,

an unusually cold winter in Mexico can be a disaster

for the butterflies.

During one storm, 80 percent of them died

in a single sanctuary.

If a harsh winter is followed by more bad weather

in the spring, then no one knows

how many butterflies will be able to breed new generations

for future migrations.

BROWER: If the numbers are reduced

to the point where the migration starts to unravel,

we don't know what the critical low number is,

but I'm worried that we might just get close to it.

NARRATOR: It's the middle of October.

The butterflies are almost to the Mexican border.

They started the migration scattered across

thousands of miles of the Northeastern U.S. and Canada.

But at this point, they're flying together in a huge flock,

only 50 miles wide, I for the final leg south.

I just saw the shadow of it.

NARRATOR: For over 30 years,

Texas zoologist Bill Calvert has conducted

extensive field studies of the migration.

But this year, he's worried...

the butterflies are late.

Well, this is perlect...

except for one thing:

No butterflies here.

An endangered phenomena would not be the same

as an endangered species.

In the case of an endangered species, of course,

we're worried about all the members disappearing.

In the case of an endangered phenomena, we're worried I

that the migration would be reduced to such a state

that it would be unnoticeable,

or maybe even the migration itself would disappear.

I mean, the predictions are that this is going to be

the lowest population ever.

NARRATOR: So far, he's only seen a single monarch.

Well, it's in pretty good shape.

It's got a couple pieces missing out of a wing over here,

but otherwise, it's in pretty good shape.

There he goes, off to Mexico.

NARRATOR: At the end of the day, Calvert decides

to take one more look in a secluded corner of the woods.

CALVERT: Let's see what we've got in there.

Oh, wow.

Look at them up there.

My God!

It's just fantastic!

Whoa, there are hundreds of thousands

passing us right now.

Butterflies have dazzled humans for millennia.

It's a beautiful little creature,

and on top of that, it migrates 2,000 miles,

and this just staggers the mind.

NARRATOR: The butterflies have been traveling

for six weeks from Canada.

But they still face the most treacherous part of the journey.

They must fly over hundreds of miles of scorching desert

and navigate the towering Sierra Madre Mountains.

CALVE RT: Something has to focus them.

I think the Sierra Madre mountains serve that purpose.

The mountains stick up' pretty high.

The butterflies encounter them,

and they turn and they follow the mountains,

and they can follow the mountains for 900 miles.

NARRATOR: Late October, in Mexico.

The butterflies are expected soon...

and the Mazahua people prepare to welcome them.

MAN: It's a privilege that God has sent us this insect.

We take advantage of the months that the butterflies are here

to earn our living.

Because the truth is

that we have a community that is quite poor.

In this season, we earn enough to make a living.

It's not a lot of money, but you can rely on it.

NARRATOR: As they wait for the butterflies,

the Mazahua pray for their safe arrival, I

along with the spirits of their loved ones. I.

It's now the first week in November.

NARRATOR: After two months and thousands of miles of flight,

the butterflies have finally reached safety.

Millions of them arrive over the next few days,

and the people rejoice.

Now, with their long journey finally behind them,

the monarchs rest.

They huddle together in huge clusters,

and cling to the trees for warmth.

They'll leave the trees occasionally

to feed on nectar and water.

But they return I to these clusters

and stay here for almost five months.

When spring arrives,

the butterflies bloom again.

They open their wings to the sun,

warming up for flight.

Most of these monarchs will travel back to Texas.

There they will stop to mate.

Each female will lay 3OO

to 400 fertilized eggs.

After the eggs are laid,

the parents will die.

When the new generation hatches,

it will keep flying north, mating along the wayj.

A third generation will do the same. I.

And almost a full year since the migration began,

that special fourth generation of monarchs

will be born in Canada.

And the miraculous migration will begin again.

BROWER: I'm frequently asked, well, “What difference would it make

if we lost the monarch migration?”.

And I say, “What difference would it make

“if we lost the Mona Lisa,

“or if we lost Mozart's music?

It's part of our culture.”

I think the monarch butterfly is

one of the most magnificent animals in the world.

It will absolutely floor anybody the first time they see it,

as it did me the first time I saw it.

It's one of the wonderful planetary cycles on this earth.

And it's unique in terms of the entire animal kingdom.

There's nothing like it.

It's really an incredible journey.

On NOVA'S “The Incredible Journey of the Butterflies” Web site,

watch any part of this program go behind the scenes and more.

Find it on pbs.org.

Major funding for NOVA is provided by the following:

ExxonMobil... taking on

the world's toughest energy challenges.

And by:

And...

And by the Corporation for Public Broadcasting

and by contributions to your PBS station from:

Captioned by Media Access Group at WGBH access.wgbh.org