[ambient music fades in]
[David Attenborough] Laysan.
A remote island in the Pacific Ocean.
[poignant music playing]
Home to this Laysan albatross chick.
He's ready to make his maiden flight to the open ocean.
But there can be no room for error.
[cheeping softly]
-[music becomes tense] -[urgently] Tiger sharks.
They've traveled a thousand kilometers to get here,
arriving just in time for the fledging season.
Leaving will be the most dangerous journey of his life.
[music intensifies]
But it's his neighbors, black-footed albatross chicks,
that go first.
[music intensifies]
A splash landing.
Just what the sharks are waiting for.
[music abates]
[music intensifies]
[music becomes dramatic]
Now, it's his turn.
With the summer winds picking up,
conditions are finally right for him to spread his wings
and fly.
[music intensifies]
He's airborne for the first time in his life.
But when the breeze suddenly drops…
[music abates]
…so too does the chick.
[tense music playing]
Without wind,
he's helpless.
[music intensifies]
[squawks]
A very lucky escape.
[screeches]
[music intensifies]
[music becomes rousing]
He's off!
He may not touch land again for five years
as he travels hundreds of thousands of kilometers
across the ocean searching for food.
[music climaxes]
[music fades out]
[theme tune playing]
[theme tune fades out]
Our planet is solar-powered.
[rousing music playing]
The sun's rays take eight minutes to reach us.
But due to the Earth's tilt, they don't strike its surface evenly.
This solar energy arrives in varying amounts
at different times of the year, depending on where it strikes.
And in the Northern Hemisphere,
the huge increase that comes with summer
triggers countless journeys.
[music fades out]
[chorus of twittering birds]
In early July,
the flower meadows of Europe receive more sunlight
than at any other time of the year.
And that makes it a very busy time for honeybees.
[whimsical guitar music playing]
Few animals work harder to exploit the summer's riches.
To make just half a kilo of honey,
a colony of bees must fly 90,000 kilometers
and visit over a million flowers.
And we have taken advantage of their labors for thousands of years.
[music fades out]
[loud thrumming]
In this domestic hive in Germany,
60,000 bees are working together as one superorganism.
[hypnotic electronic music playing]
And with the larger queen laying an egg every 30 seconds,
it's a colony that is now bursting at the seams.
There could be another 40,000 bees developing in this hive.
And there just isn't enough room for them all.
The superorganism has to split.
[music intensifies]
[music abates]
[music becomes dramatic]
Those in the leaving party gather at the entrance.
[music becomes rousing]
And when they reach a critical mass, they begin to swarm.
[music intensifies]
They must find a new home.
But the first stop is just a staging post close to the hive.
In a few minutes, 30,000 bees gather around the queen,
who is now shielded by the swarm.
[music gradually fades out]
Out in the open, they're vulnerable to the elements.
So the race is on to find somewhere else to live.
Scouts set off looking for a suitable home.
[ethereal music playing]
A tree hole that is just the right size, height, and angle to the sun.
This one looks possible.
But… too shady.
Too small.
Already taken.
Now, what about this one?
[music abates]
[optimistically] It looks promising.
Yes, this will do nicely.
So it's back to the staging post
to convince the rest of the colony.
[lively whimsical music playing]
And she does that by dancing.
[music becomes quirky]
The angle of her waggle dance relative to the sun
tells them in which direction the hole can be found,
while the duration lets them know how far away it is.
And the better the spot, the more intense her performance.
Others return to advertise their finds.
But their moves just don't cut it compared to hers.
[music intensifies]
Interest grows around her.
And more bees set out to inspect the new hole.
It's house hunting by committee.
It seems they agree,
and they return to spread the news to the rest of the swarm.
[music fades out]
To do so, the scouts must touch every bee in turn.
[lively music playing]
And, incredibly, in just half an hour,
all 30,000 of them are ready to leave.
[music becomes rousing]
Upon arrival, each bee fans a pheromone across the forest,
helping others to find the new nest site.
More and more arrive at the new location.
All joining in to spread the chemical message.
Within a few hours, the entire swarm has made the move.
Bees are only able to move like this
when the sun's energy provides them with enough food
to rebuild their colony from scratch.
So for the next few weeks,
they will need to be as busy as,
well, a bee!
[music climaxes]
[music fades out]
In July, the further north you go,
the more daylight there is.
[whimsical music fades in]
And, for just a brief period,
this increase in solar power
turns the Arctic tundra into a rich grassland,
attracting more than a million snow geese.
[music becomes rousing]
They've traveled the length of North America,
a distance of 5,000 kilometers,
and they've come here to breed.
Arctic summers are short,
so the geese start laying straightaway.
The female sits tight on the nest.
While the male keeps an eye out for enemies.
[music fades out]
[quacks]
[tense music playing]
And he doesn't have long to wait.
[quacking]
Arctic foxes live here the year-round,
and they eagerly await the return of the geese.
[shrieking]
[music intensifies]
The fox's survival depends on a steady supply of eggs.
-[shrieks] -[squawking]
[music intensifies]
[geese shrieking]
But snow geese only lay one clutch a year.
[goose squawks]
And they defend it with their lives.
Nonetheless, a single fox may steal over a thousand eggs in a season.
[music intensifies]
[music abruptly fades out]
Despite these losses…
[soft peeping]
…plenty of eggs do hatch.
[peeping]
It may be the height of summer, but it's still the Arctic.
So the goslings stay with Mother to keep warm.
But there's only so much room under one wing.
[duckling screeches]
Still, it's better to keep out of the way
when the tundra's larger residents pass through.
Caribou themselves pose little risk.
But they do bring problems.
[somber music playing]
Grizzly bears follow them in the hope of an easy meal.
[growls]
And their presence causes a stir within the colony.
[music becomes suspenseful]
[sniffing]
[growls]
[honks]
Any chick in its path is hoovered up.
[honking]
[music fades out]
[chicks peeping]
With things getting dangerous,
it's time for these chicks to start their life on the move.
[whimsical music playing]
The family heads for the safety of the water.
[music becomes rousing]
In just eight weeks, when the sun's power starts to wane here,
the goslings will make their first flight south,
all the way to the Gulf of Mexico.
[music fades out]
Not all animals migrate as the seasons change.
Lions control the same territory year in, year out.
So this pride in East Africa's Serengeti relies on prey coming to them.
[snorting]
Right now, it's the height of the dry season,
and the long grass plains where these lions live
are relatively empty.
[growls softly]
But things are about to change.
[rousing music fades in]
Heading towards them are hundreds of thousands of wildebeest.
Together, they make up the biggest terrestrial migration on Earth.
The herd eats its way through nearly 5,000 tons of grass a day,
which means they have to keep on the move.
Something the lions have been counting on.
[music fades out]
[wildebeest grunting]
The long dry grass is of little nutritional value,
but the herd must pass through it.
[distant thrum of hooves]
And the lions know that.
[unsettling music plays, fades out]
The grass provides a very effective cloak of invisibility.
[insects buzzing]
[wildebeest grunting softly]
To prevent her scent being detected,
the lioness approaches from downwind.
[unsettling music playing]
[in hushed tone] Stalking.
And stopping.
[wildebeest grunting, snorting]
Every movement
considered.
One careless step could reveal her presence.
[snorting]
[snuffling]
[unsettling music playing]
[in hushed tone] Any disturbance in the grass
could be a potential threat for the herd.
[chirping]
That's just a guinea fowl.
A false alarm.
[menacing music fades in and out]
Or… perhaps not.
[menacing music playing]
She's almost perfectly placed.
Just 20 meters from her target.
[wildebeest grunting nearby]
[lion sniffs]
[music intensifies]
[music becomes dramatic]
[music intensifies]
[wildebeest shrieks]
[music fades out]
[wildebeest groans]
After months with little to eat, this is a vital meal.
The pride will need to make the most of the migration
while it's passing through.
Soon, the herds will have left the lions' territory,
moving north in their never-ending search for fresh grazing.
[ambient music playing]
In August, the Northern Hemisphere is at its warmest.
And on Canada's Vancouver Island,
there's one animal whose life cycle depends on these higher temperatures.
[ethereal music playing]
As day breaks over Cedar Lake,
something is stirring in its depths.
[music becomes hypnotic]
Tadpoles here spend their nights hiding in deep, cool water.
Now, with the sun up, they set off across the lake.
[music intensifies]
Initially, in hundreds.
Then thousands.
All are heading for the sunlit shallows.
Here, the water is five degrees warmer than in the lake's depths,
and that will speed their transformation into toads.
[music intensifies]
But when night falls,
they head back to the safety of the deep.
[music abates]
Until the next morning.
[music reprises]
Every day they repeat the journey.
Sun.
[music intensifies]
Swim.
Feed.
Repeat.
[music abates]
[music reprises]
[music intensifies]
It seems perfect.
Except others take advantage of their daily routine.
[music becomes ambient]
Dragonfly larvae.
They are ambush predators
with extendable jaws.
[unsettling music playing]
And they have voracious appetites.
Blind leeches patrol the muddy bottom.
[music becomes hypnotic]
Once they catch something…
they suck out its blood.
[leech sucking]
[music abates]
[music becomes dramatic]
Throughout the summer,
the tadpoles continue their daily commute.
[music intensifies]
[music fades out]
Until, after a few weeks…
[ambient music playing]
…they start to look like tiny toads.
By harnessing the sun's energy, they've grown quickly.
Now, they stop their daily routines
and prepare for their journey into the forest.
[unsettling music playing]
Here too,
predators await.
[music becomes suspenseful]
Garter snakes specialize in eating amphibians.
Though they rarely have as much choice as this.
[music fades out]
Eventually, the sheer numbers of young toads overwhelm the snakes.
[music becomes rousing]
The survivors spread out into the forest
where they'll spend the next four years.
Until it's time for them to head back to the lake to breed.
[music climaxes]
[music fades out]
By midsummer, there is little snow left in America's Pacific Northwest.
Meltwater fills the rivers,
ready to carry travelers who make what is perhaps
the most extraordinary and demanding journey
tackled by any animal.
[hypnotic music playing]
Sockeye salmon.
And they're heading upriver to breed.
After three years feeding in the Bering Sea,
they find their way across hundreds of kilometers of ocean,
guided by the Earth's magnetic field
and their astounding ability to recognize the taste of the river
in which they hatched.
They are one of the few fish in the world that can move from saltwater into fresh.
And over the next month,
they will travel 200 kilometers upstream,
past Lake Iliamna, to their spawning pools just beyond.
It's the last journey these salmon will ever make.
As they enter the river, they stop eating…
putting all their efforts into battling the current.
Swift rapids and high waterfalls do not stop them.
[music becomes rousing]
[music abates]
Four weeks into their journey,
their bodies begin to change.
Flashes of red appear in their flanks.
These are their breeding colors.
And the redder the fish, the fitter they are.
[optimistic music playing]
A few more weeks, and they're barely recognizable.
The jaws of the males have become hooked beaks,
which they will use to fight for a mate.
But their spawning pools are still nearly 100 kilometers away.
And just upriver,
there are predators ready to intercept them.
[somber music playing]
[music becomes dramatic]
Bears depend on the annual salmon run
to fatten up for the winter ahead.
And right now, they're very, very hungry.
[music intensifies]
During the migration,
an adult bear can eat 40 salmon a day.
The salmon are quick and agile.
[music abates]
But, as the water gets shallower…
the advantage swings in favor of the bears.
[music fades out]
Several kilometers upstream,
the fish finally reach Lake Iliamna.
[poignant music playing]
One of the last pristine waterways in America.
Their spawning pools lie just upstream.
But, for now, the sockeye linger
while the females' eggs complete their development.
[in hushed tone] But their troubles are not yet over.
[apprehensive music playing]
These waters are the home of the only freshwater seals in America.
The salmon haven't eaten in eight weeks,
but they can still outswim these predators.
[music abates]
The seals switch strategy
and start to hide in plain sight.
[ominous music playing]
In a rarely seen behavior,
they wait for the salmon to come to them.
Surprisingly, they ignore the males right in front of them.
And go for the females,
who are laden with calorie-rich eggs.
[music fades out]
[optimistic music playing]
But for every salmon that's taken,
thousands get through.
Battered and bruised from their long journey,
they have, at last, reached their spawning pools.
Once here, males and females pair up
and, together, fight for the best nest sites.
Finally, they mate.
It's the only time they will ever do so.
[music becomes spiritual]
They've given everything to complete this epic migration.
Their lives are over.
The nutrients from their decaying bodies fertilize the water.
A sacrifice that ensures the next generation
will have the very best start in life.
[music fades out]
August in the High Arctic.
After three months of continuous daylight,
little is left of the sea ice.
[chirruping]
[poignant music playing]
And that makes life very hard for this ice bear
and her eight-month-old cubs.
Three months ago, they were hunting blubber-rich seals out on the ice.
Now they're forced to swim continuously for days on end
in search of whatever food they can find.
Polar bears use five times more energy when swimming than walking.
And that is beginning to take its toll on her smallest cub.
[cub barking]
[music becomes ethereal]
He's finding it hard to keep up.
But his mother is too hungry to wait for long.
She can smell food somewhere on this island.
[gulls squawking]
And the dive-bombing gulls are a sign that she's close.
[gull squawking]
For the largest land carnivore on Earth,
these chicks are not much of a meal.
Though they would be a much-needed boost for the cubs…
if they can get down to it before it's gone.
The weaker cub is not very sure-footed.
[grunts softly]
[gulls squawking]
By the time he's caught up, it's too late.
[snorting]
[bear growls]
With food so scarce,
there is no time for rest.
[shrieks]
The climb back up should be easy.
[sniffing]
Certainly, his sibling seems to take it in his stride.
But after that long swim the weaker cub has little energy left.
[shrieks softly]
Unable to follow, he panics
and heads in the wrong direction.
[soft thud]
A slip here would mean a 15-meter fall onto the rocks below.
[cub shrieks]
[sniffing]
[cub shrieks]
His mother takes no notice of his problems,
so desperate is she for another meal.
[cub shrieks]
His survival depends on staying close to his mother.
[shrieking softly]
If he can't keep up, she will be forced to abandon him.
[soft thud]
[shrieking softly]
-[mother sniffing] -[cub shrieking]
[mother growls]
-[cub crying] -[mother growls]
He's made it.
Only to find that he must still keep going.
[poignant music playing]
It's a journey this young cub may not survive.
With summer sea ice melting earlier than we've ever known,
polar bears are having to spend more of their year swimming.
For animals used to traveling across ice,
these changes may well prove to be too great.
[music fades out]
[ambient music playing]
Six thousand kilometers south of the Arctic,
the summer sun is also heating the shallow waters of the Persian Gulf,
making the sea here the hottest on the planet.
And that attracts the ocean's biggest fish.
The whale shark.
After a journey of thousands of kilometers,
it's arrived in time for one of the best feeding events of its year…
and is heading to a particular spot.
The waters of the Al Shaheen Oil Fields.
The platforms act as reefs,
providing a home for hundreds of species.
No vessels are allowed within half a kilometer of each rig,
so creating marine sanctuaries where fish can spawn in safety.
Tuna are among them.
They can only breed when the water is 25 degrees Celsius or more.
So, in summer, when the gulf is at its hottest,
they gather together and release hundreds of millions of eggs.
The water's surface becomes thick with spawn.
[music becomes optimistic]
And that is what the whale shark has crossed oceans for.
Taking in water through its meter-wide mouth,
it collects the eggs.
More sharks arrive to join the feast.
But this is the hottest sea on Earth.
And after feeding for a few hours each morning,
the whale sharks will have to return to the cooler depths.
At the height of the spawning season,
there may be over 100 per square kilometer.
It's one of the largest gatherings of whale sharks on the planet.
And all the more remarkable that it was only recorded for the first time in 2010.
[music fades out]
Back in the Serengeti,
a million wildebeest and zebra are still on the move,
following the sun and rain in search of fresh grazing.
[rousing music playing]
And in amongst the throng…
[zebra grunting]
…new life.
This zebra foal and his family travel amongst the wildebeest for safety.
He is just four weeks old,
and keeping pace with the herd is a daily struggle.
Yet his biggest hurdle lies just ahead.
[suspenseful music playing]
The Mara River.
Its fast-flowing waters
claim the lives of 6,000 animals a year.
Crossing it will be a major trial for a foal that has never swum before.
[grunting]
The herd nears the river's edge.
None wants to be the first to cross.
But as numbers increase,
pressure mounts on those at the front.
[music becomes dramatic]
Once one commits,
the floodgates open.
But the foal and his family wait.
[grunting]
Many wildebeest drown in the crush.
[music intensifies]
[music abates]
Still, the zebra hold back.
[unsettling music playing]
And with good reason.
Five-meter-long Nile crocodiles.
Amongst the biggest in Africa.
These giant reptiles may not have eaten since this time last year.
With so many targets from which to choose,
they can afford to take their time.
[wildebeest groaning]
Soon, perhaps,
the crocodiles will have taken their fill.
[music fades out]
[somber music playing]
-No such luck. -[music becomes dramatic]
[nickers]
The zebra can wait no longer.
They must stay with the herd.
So, the young foal must now swim for his life.
[foal whimpering]
[music intensifies]
[music rapidly trails off]
[theme tune playing]
[music fades out]