The coast.
The frontier between land and sea.
This is the most dynamic of all the ocean habitats.
The challenge here is to survive change.
Extreme change.
Cape Douglas,
on the most westerly of the Galapagos Islands,
totally unprotected
from the massive rollers of the Pacific Ocean
and one of the roughest coastlines in the world.
The marine iguanas of the Galapagos
are the world's only seagoing lizards.
Seaweed is all they eat.
But doing so is a dangerous business.
The local crabs have become specially flattened,
minimizing the effect of the pounding waves.
And the iguanas have huge claws to grip the rocks.
This seaweed really is fast food.
There are only a few seconds in which to grab a few mouthfuls
before the next breaker comes pounding in.
Female iguanas feed only on the exposed rocks,
but the males, which are larger,
swim and dive beneath the surface to reach the weed.
They go as deep as 10 meters.
For there, beyond the destructive reach of the waves,
they find the best fronds.
Being cold-blooded, they have to return to land
after about 10 minutes or so to warm up again in the sun.
Finding food is not the only challenge
for coastal residents.
These rocky shores are hardly a safe place to lay their eggs,
and each year the marine iguanas have to journey inland
to find a more suitable one.
The females lay their eggs in burrows
and leave them there to hatch.
And to do that, they need nice, soft sand.
Down at the water's edge,
it was easy to escape danger in rocky crevices.
But up here, the females are dangerously exposed.
A Galapagos hawk.
The lizards don't give up without a struggle.
These hawks stay on the coast all year,
but they are exceptional.
The majority of the birds that frequent this frontier
spend most of their time elsewhere...
in or above the open ocean.
However, all sea birds have to come to land
in order to lay their eggs.
And after spending many lonely months
searching the ocean for food,
they have to re-establish their social relationships.
Frigate birds display and exchange nesting material.
Waved albatross dance.
The need to lay their egg on firm ground
ties the albatross to the coast,
but parental responsibilities are shared.
While one looks after the egg, the other can go off to feed.
The need to breed
brings many different animals to the coast each year
for a few weeks.
Male sea turtles spend all their lives at sea.
But the females, like birds,
must come to land to lay their eggs.
To do that,
green turtles that live and feed off the coast of Brazil
swim 1,500 miles to the tiny island of Ascension
that lies bang in the middle of the Atlantic Ocean.
Exactly how they manage to navigate with such accuracy
and find this tiny lump of rock, just 7 miles wide,
is a mystery.
But each year, up to 5,000 turtles manage to do so.
And then, close to the coast of Ascension, they mate.
Travelling to and from Ascension and nesting here
can take up to six months.
And throughout that entire time, none of them feed at all.
After mating, a female has to leave her natural element
and haul herself up onto land.
She does so at night,
laying about three or four times at around 15-day intervals.
After that, she then swims all the way back
to the seas off Brazil.
She returns to this very same island throughout her life.
Remarkably, all the world's sea turtles return year after year
to just a few traditional breeding sites.
Crab Island, in Australia, is one of them.
This tiny 2-mile-long crescent of sand,
lying a few miles off Queensland's northerly tip,
provides nesting sites for half the entire population
of one of the world's rarest sea turtles.
Flat back turtles are large... over a meter long...
but they have to be careful.
There are other giant reptiles here, too.
Salt water crocodiles.
Every night throughout the year, there are flat backs
burying their eggs all along this lonely stretch of sand.
Nine weeks later, and things are about to happen.
These eyes shining in the darkness
belong to night herons.
As if from nowhere,
hundreds of birds suddenly appear on the sand dunes.
Pelicans wait patiently.
Jabiru storks pace up and down.
Before long, they see what they've been waiting for.
Because these turtles lay their eggs throughout the year,
the hatchlings emerge night after night in a steady trickle
of beak-sized meals.
Pelicans' broad beaks
allow them to dig out the hatchlings
before the herons can spear them on the surface.
The surf may be hundreds of meters away,
and at least a third of the tiny turtles
do not survive the journey.
And it's not just the birds that take them.
Crocodiles, sharks, and hungry fish
are all waiting in the shallows.
In fact, only one in every 100 hatchlings
will survive to adulthood.
Another beach, another continent,
and a very special night.
Here in Costa Rica there is a turtle
which has found a way of reducing these dangers.
When Ridley's turtles arrive to lay their eggs,
they don't come in tens or hundreds
but in thousands.
Over the next six days,
around 400,000 females will visit this beach.
At the peak time,
5,000 are coming and going each hour.
The beach gets so crowded
that they have to clamber over one another
to find a bare patch of sand where they can dig a nest hole.
40 million eggs are laid in these few days.
So these turtles ensure that, six weeks later,
when their hatchlings emerge, it's not just a trickle.
It's a flood.
On some nights, over two million hatchlings
race down to the sea together.
With so many appearing simultaneously,
their predators are overwhelmed,
and most of the young turtles reach the sea safely.
Leaving the sea and emerging onto land
is hard enough for turtles.
It's even harder for fish.
Each year, for hundreds of miles along the Newfoundland coast,
capelin throw themselves onto the beaches.
At least a million tons of fish floundering out of the water.
A real gift for scavenging eagles and gulls.
Odd though it may seem for a fish,
these capelin, like the turtles,
have also come out of the sea to breed.
The males are trying to fertilize the eggs
that the females are depositing in the sand.
Like the Ridley's turtles,
they have synchronized their mass laying with the tide.
In a few days, it will be over.
Most of the capelin die
but only after they've left their eggs in the sand.
Other capelin populations lay their eggs in the ocean.
So why do the Newfoundland fish spawn on land?
It seems that eggs deposited in the beach
may be safer from predators
and develop faster than in colder waters out to sea.
But wherever they do so,
the huge spawning shoals provide the concentration of food
that sea birds need when they assemble to breed.
95% of the world's sea birds nest together,
mostly in large, spectacular colonies.
This is Funk Island,
40 miles off the coast of Newfoundland,
an isolated rock crammed with breeding sea birds.
This was the last breeding ground
for the flightless great auk, sadly now extinct.
Today it's still the world's largest guillemot colony.
Over a million of them share the crowded island
with 250,000 gannets.
It's not for lack of suitable sites
that causes the sea birds to breed in such densities.
Here in the North Atlantic,
there's a wide choice of empty coastline
that the birds could use.
The key factor limiting the size and location
of sea bird colonies
seems to be the availability of food
in the surrounding ocean.
There are lots of hungry mouths to feed
and a constant demand for fish.
Throughout the long summer days at colonies like Funk,
there's a continual stream
of birds heading out to the ocean to find food
and returning with full crops to feed their young.
Gannets will travel up to 200 miles from the colony
on a single foraging trip.
They're not fussy eaters
and will take everything from tiny sand eels to herring.
Puffins, on the other hand,
are very particular about what they eat.
And because they can only fly short distances,
they only nest where there's a good supply
of suitable food close by.
One such place is the Sea of Okhotsk
in far eastern Russia.
This is the island of Talan.
Throughout the long Arctic winter, it's encircled by ice.
But as spring approaches, that begins to break up,
and sea birds that have spent the winter
feeding out on the open ocean far to the south
begin to return.
Its isolated position and steep cliffs
make Talan a perfect nesting site.
The tufted puffins arrive first.
These are the Pacific cousins
of our less spectacular Atlantic species.
Horned puffins soon follow.
In all, 14 different species return to Talan each spring.
And in just a few weeks, the once-silent cliffs
come alive to the calls of 4 million breeding sea birds.
This is a multi story avian city.
Assembling in these dense colonies
after having spent a largely solitary life at sea
provides the birds with the social stimulation
that is the key to coordinating their breeding.
By nesting and laying together,
they ensure that most of their chicks
will leave the nest at exactly the same time.
Just like the turtles,
this is the way they spread the impact of predators.
The world's largest eagle.
Steller's sea eagle, a third as big again as a golden.
Throughout the summer,
the eagles hunt in Talan's crowded colonies.
Riding on the up drafts,
they patrol the top of the cliffs,
looking out for any kittiwake that ventures too far
from the rock face.
Suddenly, the huge eagle stoops with the aerial agility
of a falcon.
Coordinated panic among the kittiwakes
confuses their attacker.
But the eagle doesn't give up.
And it has got one.
Another kind of sea bird on Talan has a particularly effective way
of defending itself against predators.
But it doesn't appear until an hour before sunset.
As if from nowhere, dense swarms of sea birds
suddenly arrive offshore.
They've spent the day feeding far away,
where the sea ice has already broken up.
They are crested auklets, hardly bigger than starlings.
A million of them return to Talan each year
to nest in its fields of boulders.
For the hour before sunset, the hillsides come alive
with huge flocks of circling auklets.
They're nervous.
No one wants to be the first to land.
Auklets are very social
when they are back together at the coast.
One of the advantages of nesting in such densities
may be the chance to share information
on good feeding sites.
It also gives them the opportunity to court.
But perhaps most importantly, there is safety in numbers.
Ravens and peregrines circle above the scree slope
every evening.
By taking off together,
the auklets hope to confuse the predators.
Eventually, their persistence pays off.
The birds that face the greatest challenge
in coming to the coast to nest are surely the penguins.
Unable to fly,
they have no alternative but to brave the immense waves.
Most penguins live in the Southern Ocean,
and they have to accept being hurled about by the surf.
Whatever the weather, the penguin parents
have to come back to feed their chicks.
A southern sea lion bull.
He knows the penguins
always use the same traditional landing beach.
Having braved the thundering surf,
the penguins have to make a mad dash across open rock
to get to their nests.
Despite his massive size and a body adapted for swimming,
the bull chases the penguins
for 40 or 50 meters across the rocks.
Having caught his penguin,
the sea lion carries it out into deeper water,
where, by violently thrashing the little body,
he skins his meal.
The seas around the Falklands
are some of the roughest in the world.
In spite of that,
the Southern Ocean is home to millions
of tiny sea birds hardly bigger than swallows.
Petrels.
Being so small,
they are very vulnerable to the bad weather.
A severe storm can blow them miles off course
and keep them away from their nests for days.
But these birds have developed a very effective solution
to that problem.
They lay a rather special egg.
Most birds' eggs, left exposed for even a few hours,
will chill and never hatch.
But these eggs are different.
They can be left for several days without incubation
and remain undamaged
while the parents struggle home through the storm.
Prions have also come up with a good way
to avoid most predators.
They never come back to the coast until after dark.
These are thin-billed prions.
Their burrows honeycomb this hillside in the Falklands.
It's deserted throughout the daylight hours.
But as soon as it's dark
and difficult for airborne predators to hunt,
the prions return.
As soon as they land, they call.
The problem, of course,
is finding your burrow among all the others.
He's listening out for his mate's call.
And down he goes.
The Alaskan coast.
It's spring, and the last of the winter storms is subsiding.
The plankton in this sea is in bloom again.
And just offshore, humpback whales have returned to feed.
For these huge animals,
there's a real risk of coming into such shallow water.
And each year a good number of them pay the price.
It's an ignominious ending for an ageing whale.
But so much flesh will not go to waste.
A black bear emerges cautiously from the woods.
Visitors to the coast that don't come to breed
have usually come to scavenge.
A whole range of different animals
have learned to exploit the enormous quantity of food
that washes up every day on coastlines around the world.
But like so much at the coast,
the quantity of flotsam and jetsam is unpredictable.
Nobody can rely on it alone.
This carcass even attracted a shy pack of wolves
only too happy to anoint themselves
with the scent of rotting whale.
It was months
before the scavengers finally cleaned up all the meat
on this huge and unpredictable gift from the sea.
Whales give birth to their young at sea
and so can spend their entire lives there.
Other marine mammals,
ones that are in fact distant cousins of bears,
have to return each year to their ancestral home on land.
The high Arctic.
Here lives one of them... the walrus.
Walruses spend nearly all their lives at sea.
But each year for just a few weeks,
they have to return to the coast.
They seek out isolated beaches,
like this one on Round Island in the far northern Pacific.
Suitable sites like this, free from bears,
are so scarce that at times as many as 14,000 animals
will cram themselves onto this one beach.
When they first emerge from the sea, the walrus are white.
That's because,
being warm-blooded animals living in a very cold ocean,
they conserve heat by keeping their blood
concentrated in the core of their bodies.
On land, it's warm enough
for them to allow their outer blood vessels to dilate,
and that turns their skin from white to pink.
Now they can moult the outer layers of their skin,
rubbing themselves up against the rocks.
But more than anything else,
coming to land brings the walrus relief
from having to spend energy
maintaining their body temperature
in an icy-cold ocean.
Heat conservation, in fact, may well be the primary reason
so many sea mammals are forced to return to the land each year.
The world's coldest seas are in Antarctica.
Each spring, half the world's southern elephant seals return
to the island of South Georgia.
Elephant seals have particularly thick insulation
of blubber that keeps them warm.
For them, breeding is the only reason to leave the sea.
With temperatures down to -20 and 100-mile-an-hour winds,
it can't be comfortable out on the beach.
But heat dissipates more rapidly through water than through air.
So even in these conditions, their young,
which at first don't have a thick coat of blubber,
will be far warmer on the land.
Once the males are established on the beach,
the females soon follow.
Within just 10 days,
the empty beach fills up with 6,000 elephant seals.
Almost immediately,
the females give birth to pups sired the previous year.
Their milk is very rich,
and the pups grow astonishingly quickly.
In just three weeks, they turn from thin bags of skin
to fat balls of blubber.
As soon as they've given birth,
the females become sexually receptive again.
And it's now that the advantages of breeding
in such dense colonies become clear.
Females can make their choice from many males,
while successful males can have access to lots of females.
But to gain that access and control a harem of females,
a bull must be prepared to fight.
The larger the male, the louder the roar
and the more likely he is to win.
When males are well matched,
these bloody battles will last 20 minutes or more.
Eventually, the loser retreats into a stream,
already pink with his own blood.
These battles certainly help females select
the strongest bulls,
but they bring great dangers for the pups.
Each year, in the denser parts of the colony,
a fifth of the pups are crushed to death.
This is why it may be better to mate
at the edge of the beach, close to the sea.
Less dominant males hide in the surf.
They're waiting to try and steal
an illicit mating with females as they come and go.
This male knows that he's been spotted by the big bull
who claims all the females on this part of the beach.
Breeding in groups can bring advantages to pups
as well as to adults.
Along the coast of Patagonia,
southern sea lions breed together each year
in groups several hundred strong.
For the growing pups,
these colonies act rather like a school.
The bonds and relationships developed here on the beach
may be vital for the rest of their lives.
Sea lions are very social animals.
And as adults and young forage together,
they probably share information
about the location of good feeding sites.
Conditions here could hardly be better
for the growing youngsters.
As the tide goes out,
it leaves behind a selection of sheltered pools.
Perfect places for learning to swim.
At high tide, it's easy for the pups
to take their first, experimental dips in the surf.
A killer whale.
These young pups have never seen anything like it before.
The whales, though, are very experienced.
Each year, this same group turns up along the coast
at precisely the same time as the pups are starting to swim.
The whales need to surprise the pups,
so they've stopped calling to one another and keep silent.
Speed is everything.
The whales do not take pups that are out of the water,
but sometimes their momentum drives them right up the beach.
And then there's real danger of getting stuck.
The whale has to thrash in this frenzied way
to get off the beach.
Most of the pups are taken into deep water
while they're still alive.
And there the whales apparently play with them.
Often an adult whale is joined in the game by a youngster.
It may be learning how to grab a seal pup
before it risks a drive up the beach.
Whatever the reason, the seal pup, still alive,
is tossed back and forth for over half an hour.
Even when the pup is dead,
the whales' sport is not completely over.
We can only speculate at the real reasons
behind this extraordinary behaviour.
But for the whales, the hunting season is a short one.
Before long, the pups learn to stay well clear of the water,
and the whales become less and less successful.
After just two weeks, they move on.
The killing season is over.
That's how it often happens along the coast.
Things are always changing.
They're never the same for long in this,
the most dynamic of all the ocean's habitats.