Original subtitles

In a frozen land

of long, unforgiving winters,

survival isn't easy.

But a harsh climate,

a varied landscape,

and stiff competition

have created a surprising diversity of wildlife.

Each species carves out its own space...

Waiting for one time of year

when water flows

and the day all but swallows the night.

This is Alaskan Summer.

It's late July,

mid summer on Admiralty Island

in south-eastern Alaska.

This mother brown bear is searching for food.

She gave birth to her cubs in the middle of winter,

during hibernation.

In the safety of her den,

she nursed them till spring,

without eating or drinking herself the entire winter.

And she's lost 40 percent of her body weight.

The trio emerged in April,

ready to forage.

Since then they've been eating whatever she can find:

berries...

insects from rotting logs...

=even carrion.

She needs to gain enough weight now, to be able to continue

nursing her cubs through next winter.

She's brought her cubs to her favorite fishing spot,

but instead of dinner...

she finds danger.

Another adult bear.

Cannibalistic males and competing females can kill cubs,

so Mum's not taking any chances.

Her cubs are safe...

for now.

But Admiralty Island

is full of adversaries.

1,800 bears call the island home.

At one per square mile,

it's the highest density of brown bears in North America.

18,000 years ago

the area was covered by a glacial ice sheet,

with bears roaming freely as far south as Sitka.

When the glaciers retreated

they exposed over a thousand islands:

the Alexander Archipelago.

Cut off by the rising sea level,

the bears became isolated on Admiralty Island.

Their high density today is only possible

thanks to the annual salmon run

that arrives in the summer.

But there's a problem this year.

The salmon are late.

The bears need them to fatten up before winter.

Luckily, for the mother and her cubs,

they live close to the land of the midnight sun,

which means more daylight hours for foraging in the summer.

Admiralty Island lies less than 650 miles

from the Arctic Circle.

Mid summer, that means 18 hours of sunlight a day.

On neighboring Baranof Island,

it's 10pm and the sun is just starting to dip.

Twilight descends,

but the sun never sinks far below the horizon.

It brightens the sky again by 2:30 in the morning.

The long daylight hours

are crucial to survival in the Arctic.

Until the summer sun provides a release,

the key to all life,

water, remains locked in ice.

There are some 100,000 glaciers in Alaska,

Including Mendenhall Glacier in Juneau.

It's a remnant of the Little Ice Age,

which began 3,000 years ago.

Mendenhall reaches thirteen and a half miles inland

and its runoff ends in a 200-foot deep lake.

The largest moving objects on earth,

glaciers advance under the sheer force of their own weight,

like a river of ice, flowing downhill.

Giants with long, slow lives.

They begin forming when snow doesn't completely

melt away in the summer.

Each winter's new snowfall builds on the year before.

And as the layers grow and compress, glacial ice is formed.

Like rivers of ice that ebb and flow,

glacial movement is driven by freezing, melting, and gravity.

As new layers of ice are formed, the glacier grows,

while tremendous pressure and gravity slide it downhill,

sometimes trapping rocks, sediment and plants,

which can make them look dirty.

When the front of the glacier melts, it drops trapped debris.

And when this glacial front melts faster than new ice

is formed, the glacier appears to retreat uphill.

As the daylight hours grow in summer, surface melt

seeps into the glacier through cracks, crevasses and moulins,

circular, well-like shafts that sink into the glacier,

forming rivers that travel through or under the ice.

In some cases these carve out breathtaking glacier caves.

Warm melt water and air movement open the caves.

They can reach for miles into a glacier.

Mature caves, often thousands of years old,

become spectacular tunnels with beautifully sculptured walls.

Glacial ice is different than regular ice.

The compressed crystal structure absorbs all colors,

except blue...

producing the stunning turquoise.

In the end, even the oldest of caves are only temporary.

When the summer sun in Alaska

begins to melt the snow and ice,

it unleashes life.

Once-frozen waterfalls tumble down rock faces,

rivers swell,

marshes fill,

and temporary lakes form.

The high water levels provide the perfect conditions

for migrating salmon to scale rapids

and reach their spawning grounds upstream.

But to get into the rivers,

they first have to make it past

a coastline predator,

the Stellar sea lion.

These noisy males began aggregating in May.

They bark at one another almost continually,

protecting territories they've staked out for breeding season,

letting other males know it's their dominion.

Males can grow up to 11 feet long

and weigh up to 2,500 pounds.

Even on all fours,

this adult male is an impressive 6 feet tall.

Of the seals, only walruses and elephant seals are bigger.

While these might seem like barren rocks,

these isolated islands and beaches

are important reproductive rookeries.

Stellar sea lions are polygamous

but, unlike some species of seals,

the males don't coerce females into harems.

Instead, the females move freely between

the males' territories,

which explains why the males put up

such a clamor to own the best real estate.

The adult females swim in nonchalantly

a week after the males.

Smaller than the males, they can still grow up to 9 feet long

and weigh in at up to a 1,000 pounds.

Once these noisy summer colonies are established,

they can have hundreds of individuals.

In amongst the din,

males try to woo females with a call known as wheedling.

The females pup soon after arriving,

the product of last year's mating,

and calling between mothers and pups

adds to the clamor on the rocks.

One to two weeks after giving birth, the females

will mate again,

timing the birth for next spring.

Busy defending their territories

and waiting for available females to mate with,

males often fast throughout the breeding season.

Some won't enter the water even once from mid-May

'til August, when the rookeries begin to fall apart.

While Steller sea lions don't migrate,

they will move between resting and feeding areas,

eating a variety of squid, crabs, clams and fish.

During the Alaskan summer, that means feasting

on the salmon run,

which has finally arrived.

The swollen rivers create superhighways

for millions of salmon that come to spawn.

Once they make it into fresh water,

most species of salmon stop eating.

They must run the riverine gauntlet of waterfalls,

eagles and bears,

using their fat reserves for energy

to travel upstream and spawn.

Depending on the species, salmon can spend anywhere

from only 18 months to an incredible 8 years

in the open ocean before the urge to reproduce kicks in

and they head back into the river systems to spawn.

Over 5000 salmon streams wind their way into Alaska

from the coastline.

Some up to 400 miles long.

Like migratory birds, it's thought that salmon

detect magnetic fields to navigate.

It leads them from the ocean to the coast of their natal rivers.

From there, they smell their way to the entrance

of the exact river and, eventually,

the precise spawning grounds of their own birth.

Fighting currents, avoiding predators

and charging up waterfalls, it's a one way trip

they're programmed to complete, or die trying.

For the hungry mother bear and her cubs,

the moving sushi buffet has arrived just in time.

The cubs haven't learned to fish yet,

so Mum spends up to 20 hours a day fishing for all of them.

By the peak of the salmon run,

leaves and berries will be off the menu,

and high calorie, fatty salmon

will make up most of their diet.

The female will eat up to 90 pounds of food a day,

almost doubling her weight before hibernation.

The cubs have figured out that salmon is pretty tasty,

though they'd rather not share.

While she's busy working, scouting the river

for her next fishy target, the cubs play-fight silently.

No point in attracting unwanted attention from other bears.

Eventually the cubs will start mimicking

their mother's behavior and learn how to fish.

But for now, it's nice when she brings dinner to them,

though she seems to have decided that this piece is hers.

Most bears stay close to where they were born,

and for these cubs, they couldn't have chosen

a better home, with its conveyor belt of fresh salmon.

Natives call Admiralty Island Kootznoowoo:

the Fortress of the Bears.

These coastal brown bears are larger than mainland brown bears

and even their grizzly bear cousins.

They share more DNA with the worlds' largest bear,

the polar bear, though the evolutionary relationship

isn't fully understood.

It's thought that polar bears were stranded

on Admiralty island after the last glacial retreat,

and that brown bears, swimming into the archipelago

from the mainland, mated with the polar bears,

eventually creating the island's extra large brown bears.

While bears do have home ranges, they don't defend territories,

though they may defend food or a favorite fishing spot.

Even on crowded Admiralty Island,

bears tend to be tolerant of one another,

unless they have cubs, or resources are low.

When the salmon run hits Admiralty Island,

resources are anything but scant.

This season of plenty isn't isolated to the rivers.

These humpback whales have migrated north

from Hawaii and Mexico to Alaska for the summer,

lured by high levels of phytoplankton,

krill and small fish.

They do most of their feeding here in cold northern waters

in the summer, building up their reserves of blubber

for migration and mating down south in the winter.

Along the coastline,

140 million sea birds

migrate annually to Alaska for the summertime feast,

about half of all birds in the Northern hemisphere.

Having flown into the shelter of Finger Bay on Admiralty Island,

this black oystercatcher, is keeping his eye on the tide.

When the tide runs out,

the intertidal zone becomes his buffet.

When it comes back in, he returns to his mate.

It might seem a bit barren,

but it's home for the summer.

Tide goes out,

and it's back to prying limpets off the rocks

and searching for mussel.

Till the tide comes back in again.

Not dependent on the tides,

these almost fantastically painted harlequins

are taking advantage of the Alaskan summer.

They're diving for insects, fish and marine invertebrates.

These ducks are a bit of an enigma.

They migrate east and west, rather than north and south.

And adult females, almost salmon-like,

return to their natal streams to reproduce.

Further north, off South Marble Island,

the puffins have returned.

The horned puffin and the tufted puffin are here to nest.

For a bird that weighs about as much as a can of soda,

they're well adapted to life at sea.

They normally call the open water home,

over the continental shelf and the North Pacific.

Wing flapping, fluffing the feathers

and dipping the head make for a good bath.

Their feathers are waterproof, so long as they're maintained,

and help keep out the cold.

Of course, they also help with flying.

While the birds come and go,

sea otters live here in Sitka Sound,

off Baranoff Island,

all year long.

While they may be the smallest marine mammal,

adult males can still weigh up to a 100 pounds

and grow up to 5 feet long.

They like shallow areas with lots of kelp.

Wrapped around their bodies,

it acts like an anchor,

so they can rest and sleep on the surface,

in their own water hammocks.

Though these guys don't seem particularly tired.

Otters are extremely curious

and have been listed as one of the world's smartest animals,

on par with dolphins.

Highly social, sea otters tend to rest together

in single-sex groups called rafts.

Like this one, most rafts have about 10 to 100 individuals,

though the largest raft ever seen had more than 2,000.

Unlike other marine mammals, they have no blubber.

Instead, to keep warm in cold water,

they have the densest fur of any animal on Earth,

about one million hairs per square inch.

Their thick fur also traps air and makes them buoyant,

helping them to float around their kelp kingdoms.

Because it's so critical to their survival,

they spend a lot of time cleaning and grooming their fur.

With no blubber,

they also need to eat 25 to 40% of their body weight every day,

to help them keep warm.

Their food strategy?

Diversity.

Eating about 50 species of marine animals;

including mussels, clams, crabs and urchins.

Without these sea otters to keep their populations in check,

urchins would devour the kelp forests

that provide critical habitat for other marine life.

This makes the sea otter a keystone predator,

crucial in maintaining the balance

of the shoreline ecosystem.

This sea otter seems pretty relaxed,

and he can afford to be.

Predation on sea otters is rare.

They have a bit of a secret weapon, or repellent,

scent glands so pungent,

they just don't taste good to most predators.

But they still have some natural enemies,

like sea lions, and killer whales.

Thankfully, for the Sitka Sound sea otters,

these transient killer whales are searching for prey

closer to the mainland,

in the channel off Point Adolphus.

They spend 90% of the day hunting,

eating up to 375 pounds of food a day.

They roam large areas of coastal waters,

but their movement isn't predictable.

They could pop up anywhere.

While they'll occasionally make a meal of a sea otter,

they prey mainly on larger marine mammals,

their favorite being the abundant seals and sea lions

along the coast.

The summer in Alaska provides more than just a bounty

along the coast.

When water is unleashed into the landscape,

plants make up for the lengthy winter darkness.

During the long summer days,

the land transforms into a rich, green oasis.

There are about 1,700 species of plants in Alaska,

most in the lush south-east.

They take advantage of every habitat available

and burst to life under the summer sun.

Fluffy Arctic cotton is found in acidic bogs

and is common on the tundra.

The cotton tops act like down, trapping solar radiation,

increasing the temperature of the reproductive organs

during the summer.

The fluffy seed heads have evolved

to be carried by the breeze

and they can travel great distances.

Found throughout the Arctic, Subarctic and temperate zones,

it's the most widely dispersed flowering plant

in the Northern Hemisphere.

Fireweed is like a blossoming calendar throughout the summer,

opening its flowers from the bottom up,

starting in the spring,

It's named for its ability to colonize areas quickly

after a fire.

A single plant can produce 80,000 seeds,

each with a long silky hair

that allows the plant to spread easily in the wind.

High in vitamins A and C,

Native Americans traditionally ate them in the spring.

Peat bogs, known in western Canada and Alaska as Muskeg,

cover 10% of south-eastern Alaska.

This ecosystem filters and purifies water,

and acts as a carbon sink,

storing about 30% of the world's carbon.

But these bogs also produce methane,

a powerful greenhouse gas,

and they play a complex role

in influencing the Earth's climate.

The wet, temperate summer here

makes perfect conditions for them to develop.

They form in areas where the water can't drain.

Meltwater and rain collect,

creating stagnant, acidic bodies of water

that are relatively infertile.

Water and decaying vegetation,

covered by peat moss and other plants,

are the basis of the Muskeg.

Nutrients are in short supply here,

and the round-leaved sundew is working

to tap into a less competitive source of food.

Glistening droplets that look like nectar cover the plant

and entice unsuspecting insects.

The sticky droplets trap the insects

and digest them with enzymes,

releasing their nutrients for the sundew to absorb.

Though this dragonfly is too large for this plant.

Seen as the bringer of daylight in native Alaskan folklore,

the raven is worshipped as a deity.

According to legend,

the raven showed pity for naked people he found in a clam shell

and gave them food, fire, clothing, shelter,

and rituals to protect them from dark spirits.

Like the raven in the story, these adaptable animals

are among the most intelligent of all birds.

They can recognize different individuals,

learn through observation, and even use logic.

Found throughout the state,

Alaskan ravens are the largest member of the crow family,

averaging two feet tall,

with a wingspan of almost 5 feet.

These opportunistic omnivores eat everything

from insects and fruit, to rodents and fish.

And this guy's definitely not going to pass up

some leftovers of dead salmon.

They're smart enough to find food even in the dead of winter

and are year-round residents in Alaska.

Covering most of south-eastern Alaska,

encompassing everything

from the islands of the Alexander Archipelago,

to fjords, glaciers and the peaks of the Coast Mountains,

is Tongass National Forest.

At 17 million acres,

this vast expanse of wilderness

is the largest national forest in America.

It's also home to Earth's

largest remaining temperate rainforest;

larger than Vermont, New Hampshire

and Massachusetts combined.

Even in the winter,

the area stays relatively warm

compared to the rest of Alaska, hovering just above freezing.

Drenched in fog, rain and melt water,

thousand year old trees dominate the ancient forest.

Two hundred-foot Sitka spruce and western hemlock

tower above the forest floor, creating living cathedrals.

The trees here are as tall as those in the south

but do all their growing during the short, wet, summer months.

Draped throughout the forest,

lichens absorb water and nutrients mostly from the air

rather than the soil.

They are extremely sensitive to pollution,

and only grow in pristine environments.

Down on the lush forest floor,

plants soak up the moisture of the summer.

Out in exposed, windy areas,

most plants opt for being short to keep warm,

but here in the shelter of the forest,

prickly devil's club grows up to eight feet tall.

Its berries are a favorite amongst bears and other animals,

despite it being covered in stinging hairs,

with dense spikes along the stems.

This prickly plant grows slowly, is sensitive to the environment,

and mainly does well in mature forests.

The scent of rotting flesh and skunk

sometimes wafts through the forest,

but it's not always carrion or even a skunk.

Closer to the river,

growing in clumps along the forest floor,

skunk cabbage produces striking, yellow flowers

that emit the repulsive odor.

A clever way for the plant

to attract pollinating flies and midges.

Back in the river, an American dipper bobs up and down

looking for insects and small fish.

It has no problem skipping about on the slippery rocks

in the fast flowing water.

As the only truly aquatic songbird in North America,

it comes equipped for the territory.

Strong toes grip the slippery rocks and special nasal flaps

stop water from going up its nostrils.

It even has its own, built-in goggles:

extra, clear eyelids called nictitating membranes

that allow it to see underwater.

With all this equipment it can even dive under ice

and won't need to migrate south when the winter comes.

This female kingfisher, on the other hand,

is only here for the summer.

She and her partner have established

a half-mile long fishing territory along this river.

Perching on a 'watch point' along the water

she watches for prey:

fish, crustaceans, even small mammals.

They're very territorial and when another kingfisher

enters their turf,

she immediately chases it off.

Watching the kingfisher below,

an adult bald eagle surveys the area.

It's one of over 2,000 bald eagles living in Alaska,

the largest population in the world.

This adult has migrated north for the summer to nest and fish.

Built for hunting, its eyes are almost as large as a human's

but its vision is at least four-times sharper.

Two-inch long talons,

three facing forwards and one backwards,

are sharp and perfectly curved for grabbing prey.

When its leg muscles contract,

its talons close together in a vice-like grip.

While it will hunt everything,

from waterfowl like the puffin to small mammals and rodents,

it will also scavenge on carrion.

At this time of year in Alaska, like many predators here,

its favorite food is salmon.

Bald eagles usually choose large trees

overlooking the water,

where they can easily spot prey.

They're typically solitary, but in areas with a lot of food,

like the Alexander Archipelago in summer,

they'll gather in large numbers.

Salmon migration routes are prime feeding areas.

Young bald eagles are mottled brown,

not developing the striking white head

and dark brown body of adulthood

till around age five.

Their beaks also change color,

turning from black to bright yellow around age four.

Once its adult plumage has developed though,

it's difficult to tell a bird's age.

While they typically live 15-20 years in the wild,

the oldest wild banded bald eagle

was 38 years old.

Kept warm by feathers and down,

this adult is well adapted to tolerate the cold.

Its feet are predominantly cold-resistant tendons,

and its bill, mainly keratin, like human nails and hair.

Adults won't migrate south until the water freezes over.

Though juveniles leave earlier.

How they know where to go, no one really knows.

With up to an eight-foot wing span

and weighing up to 14 pounds,

they often take advantage of thermal upwellings

during their seasonal migrations.

By the end of summer,

the last of the fireweed's blossoms open.

Like the northern groundhog of the fall,

they herald a change of the seasons.

An old Alaskan saying

claims that when the fireweed's top blossom opens,

the first snowfall is only six weeks away.

At the end of August,

there are only 14 hours of daylight,

six less than in the peak of the summer.

By September the evening temperatures dip

to 48 degrees Fahrenheit.

The vegetation changes color and leaves drop to the ground.

When winter finally does close in,

the kingfishers will head south, some as far as South America.

The dipper will stay,

able to swim beneath the ice to look for food.

The Stellar sea lions will disband from the rookeries,

and develop a thick coat of fur for the winter.

And having fattened up on krill,

the humpback whales will head south to breed and calf.

Back at her favorite fishing spot,

the mother bear and her cubs

have spent the summer fattening up.

By November they'll search for a den to hibernate

until next spring.

Across southern Alaska species have found different ways

to survive and thrive.

Colonizing every habitat

and capitalizing on every food source.

All taking advantage

of this brief, abundant and wet Alaskan summer.