The coast.
Nature's most demanding hunting ground.
So hazardous that few predators stay here all year.
This frontier between sea and land is continuously changing.
Opportunities never last long.
To hunt at the coast, you have to be in the right place
at just the right time.
On the east coast of America, in the tidal creeks of South Carolina,
a team of hunters is about to leave the safety of their natural habitat.
This group of bottlenose dolphins has perfected
a unique hunting strategy.
It relies on teamwork, intelligence and timing.
But beaching themselves like this is also difficult and dangerous.
Hunting is only possible for three hours around low tide,
when the mud banks are exposed.
Razor-sharp oysters cover much of the shore.
Beaching here could be lethal.
The hunters need to find a stretch of shoreline
with just the right slope.
Too level and the dolphins risk stranding.
Too steep and they can't force their prey from the water.
Working as a team, the dolphins surround the fish,
driving them towards the shore.
Attacking in perfect synchrony, the dolphins create a bow wave.
It carries their prey onto the muddy banks.
Other fish-eaters profit from their daring.
Herons and gulls follow every hunt.
To get to the fish first,
the dolphins drive themselves high up the bank.
But if they go too far, they risk stranding.
To prevent fish escaping between them,
the dolphins all beach themselves on the same side.
Always the right.
But this has a cost -
each time they grab a fish, they also take in a mouthful of mud.
The grit gradually wears down their teeth...
..but on one side only.
In time, these teeth get so worn down that older dolphins can no
longer hunt like this and must find other ways to catch fish.
Within a few hours, the banks will vanish once again
beneath the muddy water.
The ebb and flow of the tide dominates the lives of all
who try to hunt on the coast.
Northern Australia has the highest tides in the tropics,
which expose vast areas of shoreline.
And here lives a truly extraordinary species of octopus.
Octopuses are marine animals - they live and breathe underwater.
At low tide, most octopuses would be imprisoned in their rocky pools.
But this is no ordinary octopus.
It's the only one specially adapted to walk on land.
It pulls itself along,
using the hundreds of tiny suckers that line its arms.
Hunting for crabs, it walks from pool to pool.
Apart from a rather startled fish...
..this one is empty.
So the octopus moves on.
A rock pool may seem like a safe refuge.
But the octopus' suckers enable it to move
just as stealthily in water as out of it.
Nowhere is safe when this octopus is around.
Everything living here must march to the rhythm of the coast.
Regiments of soldier crabs, several thousand strong,
march and counter-march across these Australian beaches.
They sift out microscopic food.
But they can only feed for a few hours while the sand remains damp.
And it's not just the tide they're racing against.
Hunting birds follow in their wake.
But the army is undeterred.
They swarm in such huge numbers
that their predators make little impact upon them.
But safety in numbers isn't the only defence on these flats.
Another crab here has a different strategy.
The sand bubbler crab - no bigger than a pea.
They also sift out tiny food particles
and then leave the sand as pellets in their wake.
Sand bubblers are wary and never venture far from their burrows.
The crabs position their sand balls very carefully
to ensure there is a clear path back to safety.
As soon as the coast is clear, they're off again,
racing to feed before the sand dries out.
The industry of thousands transforms the whole beach...
..until the tide returns once more.
Few hunters make the coast their permanent home -
most only visit to take advantage of short-lived opportunities.
On the coast of Thailand,
a most unlikely visitor waits for the tide to ebb.
Long-tailed macaques feed mostly on fruit and leaves in the forest.
But these have learnt to supplement their vegetarian diet with seafood.
As the tide begins to fall, the macaques make their way
down to the shore - a beach-side restaurant is about to open.
There's plenty of food here, if you know how to get at it.
The macaques have learnt to use heavy rocks as tools
to break open the sea snails.
It takes a great deal of skill to master this technique,
but not everyone has got the hang of it.
You have to be ingenious to make a living at the coast.
As the tide falls still further, it reveals the next course.
To feed on this dish,
they need a stone tool with a very particular shape.
They're after rock oysters.
To crack the shells open, they must strike the oyster
in just the right place with their chosen tool.
The lowest tide reveals a course that is particularly delicious...
..but also very hard to collect.
Crabs have good eyesight and can move fast.
So catching them requires a special trick.
Before pouncing, the macaques wait for a wave to obscure their attack.
Macaques learn their skills by watching their parents.
But some techniques do take time to perfect.
And time and tide waits for no macaque.
The returning water closes the beach restaurant for another day.
It's not just tides that rule the lives
of those that live on the coast.
The shores of Chile are battered
by some of the wildest and coldest seas.
This coastline is home to a remarkable little hunter...
..the South American marine otter.
The world's smallest sea mammal.
This rare and elusive otter is half the size of its European cousin.
They live along the Pacific coast of South America,
right down to Cape Horn at the very tip of the continent.
Surprisingly, the pounding breakers
aren't a problem for the little otters...
..but the cold water is.
A continuous frigid current sweeps up from Antarctica.
A small body loses heat faster than a large one, and so these tiny
otters can only hunt in the chilly water for 20 minutes at a time.
But their small size enables them to reach the fish and crabs
that hide amongst the boulders.
To stay warm, marine otters have to eat a quarter of their body weight
in seafood every single day.
And things are particularly hard for this female
because her cubs aren't yet old enough to hunt for themselves.
Before each fishing trip she rolls in seaweed,
trapping air in her fur,
so insulating herself from the chill of the seas.
The cold isn't her only challenge.
Being so small, these otters can only hold their breath
for about a minute, making every dive a race against time.
This otter lives on a calorific knife-edge,
often only getting enough from one hunting trip to fuel the next.
Success - a meal for the youngsters.
These otters spend their entire lives at the coast,
so they must accept its day-to-day challenges.
But coasts pulse to much more than just the daily rhythms.
On the shores of Alaska,
a spectacular annual event is about to take place.
Each July, predators gather for the biggest feast of the year...
but it will only last a few weeks.
Brown bears come down from the hills.
Wolves appear out of the woods.
And seals assemble in the ocean.
The coast is the only place where hunters from the sea
meet those from land and air.
Bears have a sense of smell 2,000 times better than ours
and can even detect prey out at sea.
They know the salmon are coming.
BARKING
They also know the best fishing spots...
..and are prepared to fight for them.
GROWLING
After years feeding out in the Pacific,
the salmon are returning to spawn.
But before they head upriver,
they must pause and modify their bodies to function in fresh water.
The young and overeager try to catch the salmon
while they're still in the surf.
Those with experience are more patient.
After six months of starvation in a winter den,
all this food is just too tempting for the youngster.
Wise old bears wait for the salmon to move into the river,
where they know the fishing will be easier.
The incoming tide signals a change.
The experienced bears now take up their prized fishing spots
at the mouth of the river.
The salmon are finally here.
As the fish are funnelled into shallower water,
a seal gets its chance.
The wolves will have to wait.
Bears dominate the river-mouth.
These bears rely on the salmon run
for nearly 90% of their year's food.
Most of the salmon make it upstream past the bears,
but now they must run the gauntlet of wolves.
The salmon will sustain the wolves through the rest of the summer.
The sheer abundance of this seasonal bounty
has made these bears the largest in North America.
Estuaries are the meeting place of rivers and sea,
and they're vital staging points for migrating birds.
In Europe, each autumn, they're visited by millions of waders.
The birds are returning from their breeding grounds in the Arctic
to overwinter in Africa, and are stopping off to refuel.
Knot can only feed when the mudflats are exposed.
At high tide, they're forced onshore
where they must wait for the tide to turn and reopen the larder.
A peregrine falcon.
BIRDS SQUAWK
Young peregrines come to these estuaries in autumn...
to hunt waders.
Peregrines are the world's fastest aerial hunters,
but this is a very challenging environment for a young falcon.
It's one predator faced with thousands of prey.
Flashing black and white,
the swirling mass of wings dazzles the falcon's sensitive eyesight.
An individual target may be a better option.
A peregrine's plumage is not properly waterproof,
so he can't afford to get his feathers wet.
He must flush his prey into the air.
But as soon as he gets close,
the waders ditch into the sea where he can't follow.
Success depends on keeping his prey away from the water.
Now it's a dogfight at close quarters.
Peregrines only stay around estuaries
for the few months the waders are there.
As soon as their prey leaves, they will head back inland.
Some animals come to the coast, not to feed
but to have their young.
SEA LION CALLS
Patagonian sea lions.
These are just a few months old.
Sea lions can't give birth at sea,
they must come to land to have their pups.
Each summer, thousands cluster in colonies
along Argentina's Valdes Peninsula.
The mothers regularly return to sea to hunt...
..but their young stay on the beach
for they have not yet learnt to swim.
Orca. Killer whales.
They come at exactly the same time each year to hunt the pups.
It's a narrow window of opportunity
and the odds are stacked against the hunters.
Just like the dolphins,
orca take great risks in leaving their natural habitat.
With every attack, there's a real danger of being stranded.
Orca can only hunt for a few hours each day,
because at low tide a rocky reef blocks their access to the beach.
So until the tide is high, the pups are safe.
Early in the season the orca have one big advantage...
..the pups are naive and don't yet recognise the whales as a threat.
But the young sea lions will learn quickly.
Silently, the killer whales move into position.
Less than half the attacks are successful
and with each attempt, the pups grow wiser.
The orca's advantage is slipping away.
For the next few weeks,
hunter and hunted are locked in a desperate race.
The orca to seize pups,
and the sea lions to learn how to evade their attacks.
These young sea lions have triumphed.
They've learnt to recognise the danger and evade the killers.
For the orca,
the window of opportunity has closed for another season.
Newfoundland, Canada.
A unique seasonal event is about to transform this place.
It is the greatest coastal breeding spectacle on the planet,
but it will only last a week or two.
Capelin.
Billions of them.
In early summer, these tiny fish mass just offshore.
The great shoals inevitably attract predators.
Humpback whales.
They've travelled over 3,000 miles
from their breeding grounds in the Caribbean.
Nowhere else in the world
do humpback whales gather to feed in greater numbers.
But no sooner have the whales arrived
than the capelin do something apparently suicidal.
They deliberately cast themselves ashore,
and, once out of water, they lay their eggs.
They're one of only two species of fish
that leave the ocean to spawn like this.
A fish out of water is an easy meal.
But capelin go to these extreme lengths
to give their offspring the best chance of survival.
For many, it's the ultimate sacrifice.
Cod.
Great numbers of them move in from deeper water
to plunder this brief bounty.
Their impact on the vast shoals is small
but as they hunt, the cod drive capelin off the seabed
and up into the range of the waiting humpbacks.
The whales herd the fish against the cliffs.
Then they unleash a secret weapon.
ERRATIC WHALE SOUNDS
These bizarre calls panic the capelin,
driving the fish ever closer together,
making them a more concentrated target.
ERRATIC WHALE SOUNDS CONTINUE
This bonanza will disperse within days,
so the humpbacks have to make the most of it while they can.
Hunters at the coast are always in a race against time.
The Hunt team came to Chile to film the world's smallest sea mammal...
..the South American marine otter.
The thing about these otters
is no-one really knows anything about them.
No-one's actually studied them for any length of time at all.
So Mark is going to have to work out
the otters' movements and habits for himself.
These otters have never been filmed before,
but Mark has a lot of experience with British otters
so it should be straightforward.
Filming them underwater, however, is a daunting prospect -
no-one has ever tried to dive with them.
It's not going to be easy. Maybe one shot a day, two shots a day
would be a successful trip.
But the underwater team has a plan.
Now, what we've got are these camouflaged wet suits,
camouflage tape on the camera,
just to try and help us to blend in a little bit more.
And so does Mark.
Well, you probably can't actually see me now, of course,
covered in camo.
But going to work, definitely going to work.
Much better than Pearson's camo wet suit palaver!
Grown men dressed like that, it's ridiculous.
We can't just get into the water and see them
because they move too quickly.
So I've got this little comms unit inside of my mask
and I can listen to it underwater.
Joaquin can talk to me from the search.
Oh, there's one.
- JOAQUIN: - He's going west under rock one.
I repeat, west under rock one.
He's on the surface, swimming really fast to three.
A combination of eyes on the surface...
He's coming back to two.
..and camouflage below brings early results.
Filming otters underwater is turning out to be easier than Doug expected.
That was cool.
I wasn't sure we were going to see one of these guys underwater
but, yeah, very encouraging.
Success for the underwater team
means the pressure is now on Mark.
I've been here six-and-a-half hours
and I've got one shot.
Not very good shot of it on a rock over there.
It's not going to work.
It's not going to work like that.
I think the only way that we're going to get any more
is to find out a way of getting consistently close to them.
I think the only way of doing that is at a den
where there's cubs and they're coming back to it consistently.
Surprisingly, the most likely den site is in a busy harbour.
So we are just by the den of the otters
and we are going to put the hide on location
to hopefully get some shots of the otter up close.
It's just a very weird mixture of, like, trying to hide from the animal
when in fact it just sees people all the time.
Doesn't quite add up.
Right, well, you can just leave me in here now. I'm quite happy.
Just send me down empanadas every few hours.
See if you can have a word with the otters,
tell them that dinner's up.
I've been sat here now for three hours, looking at a rock.
After a week of surveillance...
Where's it gone, where is it, where is it, where is it?
..Mark is no closer to figuring out any pattern
in the otters' behaviour.
Oh, don't do that.
He's had only fleeting glimpses of the adults and no cubs.
The weird thing is, I've filmed otters in Scotland
and so I've been equating those otters with these otters.
The more you find out about these otters,
you realise that they're just not similar at all.
All your tactics that you thought would work with otters
are just straight out the window,
so it's like starting again.
News of another otter family nearby raises Mark's hopes.
(It's going to happen.)
The day starts out with promise.
- ON RADIO: - 'I've just seen one of the cubs in the den.
'Just for... It was about half a second.'
That's great news. Over.
But the sun brings out unwelcome visitors.
Ah, yeah, there's been one around. About three hours ago,
but a few people have turned up on the beach
and we haven't seen it since.
The topside shoot is proving to be much more difficult
than anyone could have imagined.
This is rather depressing
because it's the only place that we have been able to actually see cubs.
The big worry, really, is that the cubs are being moved
from den to den.
If they are being moved from den to den,
then staking the dens out is almost impossible.
Such are the challenges of trying to film an animal
about which we know so little.
With all their options exhausted,
Mark and Ignacio dismantle their hide in the harbour.
Wow! Wow!
Oh, my... What the...?
The hide that was supposed to be for Mark has been used by the otters.
Look at his face!
I can't believe it.
They've been using the hide as a larder for their food.
I've never felt so utterly defeated
by an animal that I've tried to film.
After two months, I still have no idea about these animals.
Really no idea.
I thought that was an otter, then!
I just went to see in another cove this early morning,
and I just found two little cubs playing in the water with one adult.
What?
We've finally got within 100 metres of a mother and cubs.
Through sheer persistence,
Mark finally gets his chance to film an otter family.
You know, they don't feel like mammals,
they're almost like little eels,
you know, the way they disappear underneath the boulders.
I think we've genuinely revealed something new about them -
how they hunt.
You know, they go through these rocks
and that's why they're so small.
What makes the otters successful hunters on this coast
is also what makes them so hard to film...
..they're small, fast and have an affinity for nooks and crannies.
And Mark?
He's finally learnt the secret
to filming the world's smallest marine mammal.
Keep the faith.
Yeah, keep the faith.
Next time, in the final episode,
we examine the health of our planet's top predators.
We meet the pioneers on the front-line,
searching for bold solutions.
Can people make room for the world's most celebrated hunters?
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