National Geographic: The Body Changers Page #3

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so tiny we can't see them.

But ants feel the beat through twigs

and stems and come running.

A strange rendezvous of

two very different creatures

is about to take place.

The caterpillar has, in effect,

shouted to the ants,

"Come and get it!"

It's not a ploy.

The caterpillar doles out sugary

droplets which the ants lap up.

For the price of a few servings

of food,

the caterpillar is surrounded by

friendly ants.

Not a bad thing to have

the neighborhood

toughs at your beck and call

when you have a soft body

and a nasty array of predators.

This remarkable relationship will last

for most of the caterpillar's life.

The caterpillar now transforms

into a new stage.

Tentacles have appeared,

strange chemical transmitters,

that seem to rile up the ants.

The caterpillar needs the ants

to be ferocious:
danger is near.

Another kind of ant lives nearby,

a predatory species.

An enemy ant has grabbed

the caterpillar.

The friendly ants rally

in a desperate tug-of-war.

Not all battles can be won.

But without the aid of bodyguard ants,

not as many caterpillars would live

to become butterflies.

About ten days after hatching,

the caterpillar descends the tree.

It's hard to believe this creature

will soon shed its wormy form,

sprout wings and head for the heavens.

But that is the miracle

of a caterpillar.

Down in the enclave of the ant nest,

the caterpillar is reborn as a pupa.

Hunkered inside what looks like

a sarcophagus,

the pupa is a creature in the midst

of a total makeover.

Nerves are being rewired.

Old organs are dissolving;

new ones are being built.

The ants tend this defenseless animal

even though it will no longer

feed them.

After ten days,

one of the most radical redesigns

in all of nature is complete.

The pupa has become an adult,

a butterfly.

This creature's long relationship

with ants is now over.

The butterfly struggles to emerge.

It must move quickly.

In fact, if the butterfly isn't

out of the nest in minutes,

it will be devoured by the same ants

that protected it for almost

its entire life.

As larvae, these creatures were

basically enormous digestive tracts

hauled around on caterpillar treads.

As adults, they are flying machines

dedicated to sex.

If we couldn't witness a caterpillar

turn into a butterfly,

we'd never believe

they were the same animal.

It's as astounding as a Cuisin art

transforming into a 747.

Some animals undergo one

major transformation in their lives.

Others change fashions

every year with the seasons.

Dogs may wear heavy coats in winter.

But lengthening days will cause

the fine underhairs to drop out.

Soon, this dog will be cooler

in his new spring wardrobe.

Some animals change

not only their coat but their color.

The arctic fox wears white

for stealthy winter hunting.

By summer, the coat is less than

half as thick.

Arctic birds like the ptarmigan

also change color.

In summer, they're as mottled as

the terrain.

By winter, the ptarmigan is a bird

of a different color.

Other prey species

like the arctic hare

must track the seasons

with their wardrobe.

Understatement is de rigueur.

If some animals change

for the seasons on the outside,

others are transforming

on the inside.

All over North America,

redwing blackbirds prepare for spring

with remarkable changes.

Males arrive from winter havens

to squabble for territories.

No one gets a home

without singing for it.

But this male is out of practice.

He hasn't sung much at all

for half a year.

But he's been quietly transforming.

It's now opening day

of a new season of song.

The transformation was

all in his head, literally.

The blackbird is a brain changer.

Over the past months, one tiny area

in his brain devoted to song

has more than doubled in volume.

With his new swelled head,

this male now woos females with song.

When a female becomes all a-flutter,

the serenade has succeeded.

The happy new couple flies off

to the shrubbery.

It's time for a little

two-in-the-bush.

The burgeoning brain of the male may

have kept the sexes in tune this season.

Transformation promoted communication

which helped launch the next generation.

Late in the summer, blackbirds glean

the fields for the last easy morsels.

Males will transform once again.

The brain's song area dwindles,

along with sweet serenades for sex.

Birds are in good company when

it comes to changing for reproduction.

For most of its life,

a flowering plant makes stems and

leaves, a single pattern repeated.

But when the right conditions arrive,

of temperature, daylight, or rainfall,

a plant will suddenly transform,

producing a brilliant package of

sex and advertising.

As one poet put it,

"The flower is a leaf mad with love."

Deer browse among blossoms,

eating tender leaves and grasses.

A once flowering feast is

transformed into a pile of dung.

In the leftovers of a deer's meal,

two organisms will each

struggle to survive.

A fungus begins to grow threads

invisible to the human eye.

The fungus is transforming

for reproduction.

It shoots up stalks as tall as

an eyelash is long.

Each stem lifts ripening spores

above the deer's ground zero.

Meanwhile, tiny larvae are growing.

The deer was infected

with a roundworm.

To survive, these wriggling parasites

must leave their dump

of a neighborhood to reach a new deer.

So the worm climbs a fungus stalk.

Just below a black beret

packed with spores,

water pressure builds.

When the cap bursts, spores can be

shot up to eight feet away.

And worms will fly.

One of the parasites

lands several feet away.

A passing deer eats it,

an inadvertent diet of worms.

The roundworm has found a host,

and millions of scattered spores

await their fate.

Wintertime.

And the living's hard

in the far north.

At least for a relative of

the deer... caribou.

The landscape is littered

with body parts.

Antlers.

Up to 20 pounds of bone,

grown every year and discarded.

Males start to grow antlers

every spring,

a transformation

from bald to bedecked.

Antlers are living tissue crisscrossed

with blood vessels and nerve endings.

The sensitive fuzzy skin

is called velvet.

Each caribou has a signature pattern

which can grow back year after year.

It would be no less wondrous

if we were to sprout a fresh arm,

the same arm, every year.

When antlers stop growing

late in the summer,

another transformation takes place.

The tender velvet dies and is scraped

away until it hangs in tatters.

Each male is now crowned with

spikes of unfeeling bone.

Fighting is one reason for

the male caribou's transformation.

And this helps solve the mystery of

why antlers shed their velvet:

You can't fight a battle if your sword

can bleed

and is sensitive to the touch.

Some creatures grow head weaponry

every year.

Others, only a single time.

Altogether, male caribou

have plenty of company

when it comes to transformations

for battle.

If some animals transform

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