Original subtitles

The Florida coast is host to one of the biggest gatherings

of animals in the United States.

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Mullet in the millions.

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Heading south past Miami Beach,

toward a very special national park.

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A journey that is fraught with danger.

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The mullet have ten miles to go

before they reach Biscayne National Park.

But first they need to run a gauntlet of predators.

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Biscayne National Park.

Right on the doorstep of Miami.

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These inviting waters are home

to Florida's most iconic animal...

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The manatee.

They're here thanks to one of the most important habitats

on the planet.

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Seagrass meadows.

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The rain forests of the sea.

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They provide oxygen and lock in carbon with their roots,

helping to protect our natural world.

♪ ♪

(squeak)

For a manatee mom and her calf,

it takes somewhere special to provide everything they need.

(squeak)

Warm, shallow, sheltered water,

and seagrass; lots of it.

(squeak)

Mom needs to eat around 66 pounds a day.

Luckily, almost half of this park is seagrass.

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(squeak)

Once full, she can relax and feed her calf.

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The family will spend the summer

hunting for the best grazing.

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Their travels take them past the park's islands,

its tropical mangrove forests...

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...and further north past Miami.

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But it won't be easy.

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Finding good grazing in Florida's waters

is becoming difficult for manatee moms.

In polluted water, algal blooms smother the seagrass meadows,

preventing sunlight from reaching them,

and cause the grass to die.

Florida has lost 50% of its seagrass beds since the 1950s.

As a result, manatees are declining, too.

But along a coastline

struggling to preserve this precious habitat,

Biscayne's seagrass meadows are a vital oasis.

Manatees are not alone in depending on the seagrass.

It's also home to one of the park's smallest inhabitants.

♪ ♪

The dwarf seahorse.

Just one inch tall.

And a surprisingly bad swimmer.

To keep from being swept away,

they use their tails to hold on.

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They feed by sucking in passing food.

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So quick, that if you blink, you'll miss it.

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But it's their love life that causes a stir.

In the seahorse world, males have babies.

His partner merely drops her eggs

into his kangaroo-like pouch, leaving him to do the rest.

11 days later,

birth starts.

♪ ♪

Once out, the little ones are on their own.

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Some are reluctant to leave the safety of Dad's pouch,

even during birth.

Their instinct to hang on is strong.

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Dad gives birth to up to 16 young at a time.

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By fish standards,

seahorses have a fairly high survival rate.

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But the future of these tiny critters is heavily reliant

on the health of the seagrass beds.

Luckily this youngster's new home is within

the protected waters of Biscayne National Park.

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95% of it is underwater.

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The park's seagrass beds and resident seahorses

are kept safe from the wild Atlantic Ocean...

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...by the third largest coral reef in the world.

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The Florida Reef rises up out of deep water,

creating a protective wall 360 miles long.

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Shielding six million people from waves and storm surges.

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The true unsung hero of Biscayne National Park.

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The coral barrier reef marks the park's Atlantic edge.

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On its western boundary lies an unlikely sanctuary

for one of the park's largest predators.

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Meet the American crocodile.

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Weighing in at 400 pounds

and 10 feet long.

Classic ambush hunters,

nothing is off the menu for this crocodile.

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Unlike her more fearsome Australian and African cousins,

she's no man-eater.

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Hers is a story of hope and survival.

By the early '70s there were less than 300

American crocodiles left in Florida.

Now there are thousands.

Thanks to an unlikely savior.

In the 1970s, Turkey Point's nuclear power station was built

next door to what would become Biscayne National Park.

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It's now home to nearly a quarter

of the American crocodile population.

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Their fierce reputation does them a disservice.

Croc moms are surprisingly caring.

Eleven weeks ago,

she buried around 30 eggs in this shallow nest.

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She's checking on her brood with increasing regularity.

Listening for the sound of chirping within the eggs.

(chirping)

Hatching has started.

(chirping)

The sound of their siblings chirping from inside the eggs

spurs the hatchlings to stage a mass breakout.

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The hatchlings are nearly a foot long.

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Equipped with sharp teeth and ready to go.

(chirping)

But this great escape isn't so easy for everyone.

Breaking out of the tough shells is hard work.

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He'd better hurry.

Mom is waiting to carry them to the water.

Without her help and protective presence, he'll be vulnerable.

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Best not get left behind.

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Even if your sibling walks all over you.

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For hatchlings struggling to escape,

Mom will step in to help.

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For this little guy, there's no need to shout for Mom.

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Freedom.

(chirping)

The American crocodile's future here at Turkey Point

is looking bright.

With the addition of these newborns,

numbers are on the rise.

Between the park and the power station,

the crocodiles have over 170,000 acres

of protected area to roam.

More than enough space for this clutch of growing youngsters.

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Every corner of Biscayne National Park

provides shelter and a home.

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The salt water-loving mangrove forests are no different.

(distant squawking)

Rising from the sand,

they're one of Biscayne's most valuable resources.

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These tangled trees absorb the power from storm surges...

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...protecting the coastline and millions of people

from destructive waves and erosion.

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Alongside the seagrass,

mangrove forests are a powerful tool

in the fight against climate change.

They can store five times more carbon

than tropical forests like the Amazon.

The role they play here is priceless.

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Above water, birds roost in the branches.

(birds calling)

Underneath, mangroves hide a secret world,

with easy pickings...

for those in the know.

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The tightly packed roots of the mangroves

are a perfect location

for a fish nursery.

A safe and sheltered home to grow up in

before leaving for the reef beyond.

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But every neighborhood has its troubles.

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A juvenile lemon shark cruises Biscayne National Park,

here to learn one thing: how to hunt.

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The fish have the size advantage

in this deadly game of hide-and-seek.

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The lemon shark needs to be patient.

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Luckily, he's got the time.

He will hunt in the safety of the mangroves

until he's seven or eight years old,

before moving out to live and hunt

along Florida's sandy coastal shallows.

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Fish aren't the only ones to use Biscayne National Park

as a nursery.

Under cover of darkness...

(thunder)

...and undeterred by an encroaching lightning storm,

an old traveler returns to the beaches around Biscayne.

(thunder)

A female loggerhead turtle.

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She's traveled thousands of miles

to lay her eggs on the beach where she hatched.

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Once in position, she digs a deep enough hole

to fit in over 100 eggs.

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Over 40% of the world's loggerhead nests

are in Florida.

During the summer months, nearly 100,000 nests

will be dug by returning turtles.

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Eggs laid and buried, her role as mom is done.

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It's exhausting work

when you're not designed for a life on land.

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(thunder)

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From here on, her offspring are on their own.

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Mom returns to her life as an ocean wanderer.

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It will be at least two years before she's back to lay again.

But it will be over 20 years

before her daughters are mature enough to return.

(waves crashing)

Although dominated by water,

the park isn't only about marine life.

There are 4,000 acres of offshore island keys.

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Running through the heart of Biscayne National Park

sits the largest, Elliott Key.

This tropical island is home to a fragment of hammock forest,

an ecosystem that once stretched

all the way through the Florida Keys.

Dense, damp and tangled,

this is now one of the rarest habitats in North America.

For millennia, Elliott Key was used as a seasonal settlement

by the Tequesta people, and then by fishermen.

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In the 1960s, developers started plowing a highway

through the island.

Public backlash and the establishment of Biscayne

as a national monument in 1968 halted the work.

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Today, the overgrown highway is delivering

some very special cargo.

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This is the Schaus' swallowtail butterfly.

Their undulating flight is perfectly evolved

to navigate the tangled, ancient trees.

They can even fly backward,

handy when avoiding avian predators.

It's a sight which nearly disappeared.

When a survey was done in 2012,

only four were found in the wild.

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Thanks to the work of

the Florida Museum of Natural History,

these butterflies can again be seen flying free.

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1,650 captive-bred swallowtails have been released.

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Today another 53 will join them.

Some are pair bonded and ready to help add

to the wild population of Elliott Key.

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Over the next three weeks,

they will mate, lay eggs, and die,

establishing the next generation.

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Maybe soon this dancing butterfly

will not need their human matchmakers.

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(waves lapping)

Back at the beach, under the cover of darkness,

the loggerhead hatchlings have left the nest,

following their mom's route down the beach and out to sea.

All except one.

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She's alone and vulnerable.

She goes for it,

following in the flipper prints of her siblings.

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But there's something lurking in the darkness.

A ghost crab.

Hatchlings can be easy prey.

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Especially when she's on her back.

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By luck or instinct,

flicking sand in her attacker's eye

turns out to be...

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...the perfect defensive move.

(flies buzzing)

Free at last, she needs to get a move on.

(waves lapping)

With dawn comes a much higher risk of predation

from passing birds and raccoons.

She's running out of time.

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She's made it.

And just in time.

She now faces an epic journey.

With Biscayne National Park far behind,

she's heading out to the Sargasso Sea

in the mid-Atlantic.

There she will feed amongst the vast rafts of floating seaweed

until big enough to navigate the oceans on her own.

As the hatchlings head out to sea,

they may spot a curious sight.

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Perched on sandbanks a mile offshore

sits a collection of wooden houses called Stiltsville.

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Built during the Prohibition Era,

it was used as an offshore speakeasy

for drinking and gambling.

At its peak, Stiltsville consisted of 27 houses.

A community promoted as being "dedicated to sunlight,

salt water, and the well-being of the human spirit."

Today, things are quieter

in the national park,

and a different kind of wildlife stops by.

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Cormorants, much like the humans before them,

use Stiltsville as a handy hangout

for drying off and preening between fishing trips.

(squawking)

Biscayne National Park is

a place on the very edge.

Its isolated, battered islands

have a unique timeless quality,

despite its proximity to a bustling modern metropolis.

It provides peace and sanctuary

to visitors as well as the wildlife.

At the peak of summer,

temperatures climb toward 90 degrees.

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The sun at its height

is also at its most powerful.

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Visitors need to remember their sunscreen.

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Underwater even the locals are not immune

to the sun's strong rays.

To protect from the bleaching power of the sun,

the park's coral community have developed

their own extraordinary type of sunscreen.

Living inside the corals' cells

are microscopic algae called zooxanthellae.

Fueled by the sun, the algae photosynthesize,

giving the coral reef its color.

Despite being sun-loving, the algae can be easily damaged

by too much ultraviolet light.

Their strategy: to make their own sunscreen.

They produce a protein which absorbs the light

and re-emits it in other colors.

Only visible to human eyes

under a special blue light.

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The results are cosmic.

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The fluorescent pigments absorb

the sun's damaging wavelengths of light

and emit them as colorful light,

protecting the algae.

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It's so much more than a beautiful spectacle.

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In areas where the reef is shallow,

with no escape from the midsummer sun...

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...this is a lifesaving strategy,

revealing the remarkable resilience

of these tiny superheroes

of the reef.

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(wind whistling)

The hot summer sun on the warm water

can also trigger a reaction above the water.

(rumbling)

Mile-high cumulonimbus clouds bubble up above the warm ocean,

creating a thunderstorm,

heavy with rain,

heading for Biscayne National Park.

(rumbling)

(rainfall)

The arrival of the rain and the rising tide

threatens a community of thousands.

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The storm may have passed, but water levels continue to rise

around a nest of fire ants.

This aggressive, invasive species has few predators,

but the rising water

will easily drown the ants in their nest.

Time to evacuate.

♪ ♪

The ants have an ingenious solution.

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Following chemical signals and an unspoken plan,

the entire colony starts banding together,

forming a living raft.

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No one is left behind.

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The large queen, along with her precious larvae and pupae,

are kept safe and dry in the middle.

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The rest of the ants continually rotate position.

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And when underwater,

air pockets allow them to breathe.

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They can remain like this for weeks.

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But as soon as the raft hits anything above the water,

the colony will de-raft,

and construction of a new nest begins.

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Biscayne's visitors change with the seasons.

Some prefer the heat,

others the cool of winter.

The wildlife is no different.

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Early fall, and the mullet are running.

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Millions of the banana-sized fish have arrived

to travel south along the coast of Florida...

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...catching unwary swimmers by surprise.

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Normally found in the rivers and estuaries

of the Carolinas, Florida and Georgia,

the mullet are now traveling south...

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...past the white sands and the high-rises of Miami Beach,

toward Biscayne National Park.

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Their aim: to spawn in the warm waters off southern Florida.

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But a gathering of this size does not go unnoticed.

Predators are lured in by the possibility of a feast.

Sharks and tarpon patrol the edges,

waiting for the perfect moment.

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♪ ♪

The mullet have nowhere to go but up.

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Tarpon attack from the side, the sharks from below.

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Birds pick off fish trapped against the surface.

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But even with this many hunters,

the fish have the odds stacked in their favor.

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There are 10,000 fish per hunter.

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There's safety in numbers.

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For most, anyway.

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Their huge numbers serve another purpose.

When the time comes to spawn,

it works best if everyone goes together.

A mass spawning, creating and sending the next generation

of mullet out into the blue.

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Biscayne National Park stands at the very forefront

of our battle with a changing climate.

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Fighting for it is an army of passionate,

dedicated scientists and volunteers...

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...working to ensure the future of the park and its wildlife.

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In doing so, Biscayne will continue to protect

both the human and animal inhabitants

of Southeast Florida.

A reminder that America's national parks

are there for all of us.

♪ ♪