01x04 - Freshwater

[bunniefuu]

SQUAWKING

A reed-bed in Somerset,

and dragonflies glint
in the early morning sun.

They won't take to the air
until their wings are dry.

Others have spent the night
in large communal roosts...

..and, as the day warms,
they slowly climb up the reeds.

Until finally...

..they're ready.

All dragonflies begin their lives
as larvae in freshwater

before emerging as adults
for their summer in the sun.

Their flying agility
is second to none.

Or almost none.

A hobby.

These small birds of prey
spend the winter in Africa

and time their arrival in Britain

to take advantage of this
mass emergence of dragonflies.

But things don't always
go their way.

The dragonflies can dodge
with a flick of their wings...

..so the hobbies turn their
attention to the female dragonflies,

who are busy laying their eggs
on the water's surface.

The hobbies come in low and fast.

Got her!

This summer spectacle
is totally dependent on one thing.

Freshwater.

Here in Britain and Ireland,

we have some of the loveliest
rivers and lakes in the world.

From the lochs of Scotland
to the waterfalls of Wales.

From the great Shannon River
in Ireland

to small intimate chalk streams
like this one in Wiltshire.

But today, less than half
of our rivers and lakes

are in good health for nature.

In this episode, we will reveal the
crucial role that freshwater plays

in supporting wildlife of all kinds.

Freshwater is the lifeblood
of the natural world.

We have over 150,000 miles of rivers
in the British Isles.

They flow through every landscape,
connecting all our wildlife.

The water's journey starts
at the top of the mountains.

Rivers shape the landscape.

They feed and water a multitude
of different habitats.

And, finally, they enter the sea.

And here in northern Scotland,

ghostly shadows have gathered
where they do so.

Atlantic salmon.

After four years at sea,
they've returned to the very river

where they were hatched.

It's spring, and they will spend
the next six-months

battling their way up-river
to their breeding ground.

But their great numbers
have attracted attention.

Bottlenose dolphins.

A pod has gathered at the mouth
of the River Ness.

The tide is rising,
and this is when the fish

will try to enter the river itself.

The salmon may be over a metre long
and difficult to swallow...

..but these intelligent hunters
still find time

to play with their food.

Those salmon that get past them
swim through a hazy mix of waters...

..and at last reach the fresh.

From this point on,
they are freshwater fish.

Their bodies change, inside and out.

Their sea-fresh silvery sheen
dulls to a darker hue

that camouflages them
against the riverbed.

But the river is low.

Until there's rain,
they can go no further.

They may be stuck here for months.

As they will no longer eat,
conserving energy is key.

Rain - at last.

The river rises, so the fish can
start moving further upstream.

The rapids of the lowlands
are passed without much effort.

But things soon start
to get more difficult.

The salmon push on ever higher,

before reaching the most demanding
test on their journey.

These falls are three metres high...

..and right at the fish's limits.

They gather beneath
the thundering water.

Some make practice leaps...

..assessing the best angles
of attack.

Finally, the time is right...

..and now the real leaping begins.

They use the white water to
slingshot their bodies into the air.

No other fish can clear waterfalls
as high as this one.

Some crash into the rocks,

the thud of their
muscular bodies audible

even above the roar of the water.

Every year, fewer and fewer get
to this point in the river.

Returning salmon numbers
have fallen by 70%

in just 25 years.

But those that have got here
push on with astonishing vigour.

By late autumn, the survivors
finally arrive

at their traditional
spawning grounds.

It's time, at last, to breed.

The females get straight to work,
digging their redds -

shallow depressions in the gravel.

This is where they will lay
their eggs.

The males, in full spawning colours

and with newly-developed
hooked jaws, wait close by.

A female releases thousands
of eggs...

..and one of the males
fertilises them as they emerge.

It's the culmination of a journey

against the flow and the odds.

The eggs will develop in the gravel
throughout the winter

and soon become tiny fry.

Their heartbeats visible
through their translucent skin.

The salmon's return will sustain
the whole river ecosystem

through the long winter months.

But they need cold, clear,
free-flowing water to thrive,

and due to climate change,
pollution and dams,

all are in short supply.

Atlantic salmon were once common
across Britain and Ireland,

but are now increasingly restricted
to these remote northern rivers.

At the current rate of decline,
they may disappear

from all our rivers
in as little as 20 years' time.

The grandchildren of these fish
may be the last

to make this astonishing journey.

The rivers, having left the
mountains, widen and slacken.

In places, they enter lakes
such as this loch in Perthshire.

But here something else
may slow them.

Beavers.

400 years ago, they were hunted
to extinction for their fur,

but now they've been
reintroduced to Scotland

and it hasn't taken them long
to get established.

Signs of their industry
are easy to see.

They are best known, perhaps,
for their skill in building dams,

and this family spends a lot of time
making sure that theirs

is in good shape.

The dam has created a huge wetland.

It's a beaver-built paradise...

..that provides plenty
of living space

and unlimited access to food.

At this time of year, branches on
the move can only mean one thing.

Newborn beaver kits.

The kits will stay with their family
for the first few years,

before setting out to find
territories of their own.

There are over 250 beaver
territories in Scotland,

and they're now being reintroduced
into England and Wales.

By slowing the river,
the beavers create a rich habitat

for a whole range of other species.

Right to the top of the food chain.

Ospreys.

Still, clean water attracts
all kinds of wildlife.

On a heathland in Dorset,

spiders' webs cover the bushes
surrounding a pond.

And one specialist species lives
at the very edge of the water.

A female raft spider.

She's the size of your palm
and a deadly assassin.

She uses the surface of the water
as her web...

..and senses the presence of prey
from its vibrations.

A good start,
but it's mating season,

and she'll need much more food
if she's going to breed.

A pond-skater could be a good snack.

But it's not easily caught.

Such a small meal
is barely worth the effort...

..but she can also hunt
under the surface.

There are much bigger meals
to be had down here.

The larva of a diving-beetle.

Itself a ferocious predator.

But it has to come to the surface
to breathe

through a tube in its rear.

And that brings it within
striking range of the spider.

At last, a real meal.

Now she has the energy needed
to find a mate.

She lays down a thread of silk

laced with perfume...

..before returning
to her favourite spot.

And it's not long before another
raft spider picks up the trail.

A male.

He has a pair of large
boxing glove-like organs

called pedipalps
in which he stores his sperm.

And this is what
he's been looking for -

a thread of silk that leads
straight to her.

Once close, he taps
the water's surface

to signal that he's about
to approach.

He's no bigger than her last meal.

A wrong move now
and he could become dessert.

She seems receptive.

It's now or never.

Carefully does it.

They mate in a tangle of legs

and he uses one of his palps
to transfer his sperm

into a sac in her body,
where she will keep it

until she's ready to use it.

The male then beats a
hasty retreat...

..before she makes a meal of him,
too.

As rivers reach the middle stages
of their journey,

they increase in both size
and power.

And it is their force over millennia
that has shaped our landscape.

In limestone country,

the freshwater carves
its way underground.

Britain and Ireland contain
thousands of miles of caves,

including these in County Cavan.

The dripping water builds
stalactites and stalagmites,

like these teeth coming together
in a rocky grimace.

Over centuries, it can create
all kinds of pillars and curtains.

Yet, even here, there is life.

CLICKING

Daubenton's bats roost in caves
during the day.

And, as night falls,
they head out to feed.

Ghostly shapes appear
over a starlit river.

The bats navigate by sending out
echolocation calls

which we can watch in operation if
we slow down both sound and picture.

It's soon clear why Daubenton's bats

are also called water bats.

They patrol the river, searching
for tiny movements on the surface

of the slow-moving water.

They use the echoes
from their calls...

CLICKING

..to lock on to their prey.

And then skim it from the surface.

Weighing about 8g,
these little bats can nearly double

their body weight
in a single night's hunting.

And on this autumn night,

the males in particular need
all the energy they can get.

A Daubenton's bat circles
in a woodland glade.

And it's soon joined by others
emerging from a cave

at the base of a tree.

Amongst their navigational clicks,
there's a different sound.

CHIRPING

They are calling to one another.

CHIRPING

As their numbers increase,
so do their calls.

Soon, other species arrive,
including Natterer's

and brown long-eared bats.

There can be up to ten species
at any one time,

whirling around
in this pitch-black arena.

This is a display ground

where male bats compete
to impress the females.

Some of these bats have travelled
over 40 miles to be here.

CHIRPING

Around midnight, the bats disappear
back into the caves below,

where they will soon settle down
to hibernate.

Spring brings the end of hibernation
for another animal.

CROAKING

A common toad.

This is a female.

Common toads need freshwater
in which to lay their eggs,

so she must find a pond...

..and that can involve a journey
of several miles

which is full of obstacles
and dangers.

She's not the only one
on the move tonight.

Male toads are also about.

They're in search of females,

and when this male finds one,
he locks on tight.

But his rivals have the same idea...

..and then it's a wet-legged
wrestling match

to stay in prime position.

The competition is seen off
and the bonus is a free ride.

But the biggest challenge
lies ahead.

Roads now cross many of the toads'
traditional migration routes

and tens of thousands
are k*lled every year.

CROAKING

Made it.

With toad numbers down by two-thirds

in the past 30 years,

we ought to be careful
on warm, wet nights in March.

At dawn, the female
and her hitchhiker

reach the end of their journey.

The very pond in which she hatched
as a tadpole.

They get straight down to business

and the female produces thousands
of eggs in long links of spawn.

The male, if he holds on tight,
will fertilise them all.

A few months later
and summer is here.

These tiny toadlets are now
ready for their next stage.

They must head for dry land.

They will spend most of
their adult lives in the woods

from which their mother emerged.

But to get there,
they must cross a k*lling zone...

..haunted by giant leeches.

Some are 15cm long.

And they have an appetite
for baby toads.

They hunt using a keen sense
of smell and five pairs of eyes.

The toadlets must keep going
if they want to reach the woods.

If they're not quick enough,
their fate is grim.

Consumed whole.

SQUEAKING

The leeches can grab
with either end of their body

and three sets of teeth.

Once caught, a toadlet
has no escape.

But for every one that is taken,

hundreds make it to the safety
of the woods.

For most of these toadlets, it's
a horror story with a happy end.

In the British Isles, we have
one of the world's rarest

and most beautiful
freshwater habitats.

Chalk streams.

Only around 200 exist in the world

and over three-quarters of those
flow here in England.

A reliable flow of cool,
mineral-rich water

bubbles up through the chalk below

and supports a rich
freshwater community.

SQUAWKING

On the riverbed, something stirs.

This young insect has spent
the last two years

buried in the gravel.

With strong front legs, feathery
gills and a stream-lined body,

it's excellently adapted
to life underwater.

But it's late May, and everything
is about to change.

Even breaking through the surface
is a challenge

when you're just 2cm long.

Finally, as its wings unfurl,

the little creature starts
a new life as an adult -

a male mayfly.

He now has just a few
short days to live,

so he quickly prepares
for his first flight.

And the sooner the better.

The fish below are the first to
notice this springtime bonanza.

And it's not long before those
above water also get their eye in.

He needs to get airborne.

But it's out of the frying pan

and into the fire.

At least the mayfly have
the advantage of great numbers.

In just a week, more than
a million will emerge

from this stretch of river alone.

And the first thing the male does
is head for the river bank.

Unique among insects, mayfly
undergo a second adult moult

before they're fully mature.

His whole life has been building
to this moment.

And finally, he's ready.

He flies high above the river

and joins the mating dance.

Rising and falling
with the other males,

he spreads out his tail,
showing off his aerial prowess.

It's all for the benefit
of the females,

who are now emerging
from the water below.

Soon, the river bank is alive
with mating pairs.

Each male will continue to dance
until he dies of exhaustion.

A small hole in the river bank -

home to one of the most secretive
of the river's residents.

A shrew.

This one, a female,

is pretty small -
about the size of your thumb.

Being small means
she loses heat quickly

and must eat almost constantly.

Three hours without food
could be fatal...

..so when supplies on the bank
get low,

she must find food elsewhere.

She's a water shrew.

She's somewhat reluctant at first.

Underwater, she will lose heat
even faster.

But needs must,
so when she does take the plunge,

she works at great speed.

In real time, it's impossible
to see what's going on.

But slowing things down reveals
how marvellously adapted she is

to the underwater world.

Stiff hairs on her feet
act like flippers

and others on her tail
turn it into a rudder.

She swims with her eyes closed...

..fanning out her whiskers
to help her sense her prey.

And, most remarkably,

she can detect smells down here.

She lets out tiny bubbles of air

to pick up scent particles
in the water.

It's known as bubble sniffing.

But using this technique means
she quickly runs out of air.

This time, everything comes
together.

A dragonfly larva is a huge meal

but hard to subdue.

It's time to use her final weapon.

Water shrews are the only mammal
in Britain with venomous saliva.

All wildlife is dependent,
to some extent, on freshwater.

But here in England,
every single river is polluted.

Run-off from farming
and dumping of human waste

causes algae to bloom.

This reduces oxygen,
chokes the plants,

and degrades the rivers
on which our wildlife depends.

GRUNTING

As rivers approach the end
of their journeys, they slow,

and beds of reeds
are able to take root.

Here in Suffolk, it's late winter.

Red deer.

This huge area is a little-known
winter refuge

for Britain's largest land mammal.

The paths the deer create
make gaps in the reeds.

And on the open water,

great crested grebes.

It may be early in the year,

but their mating dance
is already well under way.

As a prologue,
the birds shake their heads,

showing off their plumage
and preening

to make sure their feathers
are in tiptop condition.

Costumes ready,
act one reaffirms any bonds

that were made in previous years.

Single birds call for a partner...

..before adopting a posture
known as the cat display.

It's an invitation...

..for a duet.

It seems to have been accepted.

The pair are falling into step.

But they are interrupted by a rival.

SQUAWKING

Another male is looking
for a partner

and starts a sharp-beaked argument.

But all's well that ends well.

The rival is seen off

and the pair begin the final act
of their duet -

the weed dance.

These complex displays
create a bond between the pair

which will keep the two together
as they raise their young.

A few weeks later,
and the first chick appears,

shortly followed by the second.

Both parents care for the chicks,
taking turns to babysit

while the other finds food.

CHIRPING

They even take feathers
from their own backs

and feed them to the chicks

to protect tiny tummies
from sharp fish bones.

This extraordinary caring behaviour

depends on the firm bonds that
were made back in the spring.

Grebes that dance together
stay together.

We have lost huge areas
of reedbeds over the years,

drained for agriculture.

But recent conservation efforts have
shown that they can be restored

remarkably quickly.

The journey of freshwater ends
when rivers reach the sea.

Here they may create vast mudflats.

Together, they constitute
over 2,000 square miles

of our coastline.

From above, they look lifeless.

But they are full of opportunities.

It's low tide, and there
is plenty of space to forage.

Every winter, millions of
migratory birds from all over

the northern hemisphere arrive
in our estuaries to refuel.

But the tide has turned
and the sea starts rushing in.

The restaurant is closing

and the birds are driven
from the mud.

The most common birds here - knot,
take to the air en masse.

Watching from above, a peregrine.

It may be the fastest animal
on the planet,

but it won't be rushed.

It surveys the flock from on high...

..and then tucks in its wings

and dives at speeds of up to 200mph.

The knot bunch tightly together.

There's safety in the middle
of the flock.

It's difficult for the peregrine to
select an individual bird...

..so it changes its tactics.

Coming in low, it's easier to
pick out an individual knot.

Using the hard-packed mud
as a weapon,

it drives its victim
into the ground.

The knot is left
with a damaged wing.

But the peregrine will be back.

Every winter, peregrines come to
the coasts of the British Isles

to take advantage
of this seasonal bounty.

The flock is reduced by one...

..but when you are 100,000 strong,

that is a small price to pay.

With the tide now at its highest,

the birds settle down to rest.

The position of the British Isles
on the planet

makes our estuaries
globally important.

SQUAWKING

They provide vital refuelling
stations for migratory birds

from different parts of the globe.

On its journey from the mountains
to the sea,

freshwater has fed and refreshed
the natural world.

It's the lifeblood of
our Wild Isles.

One of the greatest spectacles

in the British Isles

is the migration of Atlantic Salmon.

Despite their numbers
being in freefall,

the freshwater team were
determined to find new ways

to film these astonishing fish.

Their story begins near Inverness
in north-east Scotland.

Every summer, a pod of bottlenose
dolphins gather just offshore,

drawn here by the salmon.

They come along a very
narrow channel that runs

just off the beach here.

The dolphins have clocked that

and they can basically just sit
off the point in this deep channel

and wait for the fish to come
and just pick them off.

The dolphins only hunt
for about an hour,

so the crew get into position early.

But they're not the only ones.

Crowds of people soon join
to see the action.

This is one of the best places
in the world

to see this behaviour
so close to shore.

The next stage for the salmon
is to swim up into the freshwater.

Here, they're nervous
and extremely wary of people,

so it's almost impossible to film
using standard techniques.

But the crew have a trick
up their sleeves.

An underwater drone.

This is another, "What could
possibly go wrong?" moment.

HE LAUGHS

Taff has been experimenting with
this technology for over five years

and thinks it's the only way to
really enter the salmon's world.

Even now, it doesn't always
go to plan.

Oh!

Ah, no, one of the screws has gone.

There is no way
I'm going to find the screw.

Oh, oh, oh! What?!

Oh, you beauty.

With the sub back up and running,

the team begin to record
the salmon's underwater world.

A glimpse into this
extraordinary migration

that few people have seen.

One of the most beautiful things
I've ever seen.

Absolutely mesmerising.

The next and greatest challenge
for the salmon

is ascending
the three-metre waterfall.

Filming the salmon leaping here is
the team's biggest challenge, too.

For the first shot,
the camera needs to be positioned

directly above the falls.

That means getting more than
100kg of kit into position

four metres above the roaring water.

The fish still aren't jumping
at the moment,

but that's fine cos they're
waiting for the water to drop.

Hopefully, in the next few hours,
they'll start to jump

and once they do start, there should
be repeated attempts of this.

The new camera position pays off.

The team film the salmon leaping
head-on for the first time.

But there's one angle that Taff
has been dreaming about for years.

We're going to try the dream shot -

the fish actually leaving
the water from below.

OK, so this is it.
The moment of truth

OK. Yeah, yeah, I'm ready.

Yeah.

Away she goes.

Below the falls, the water flow
is at its highest...

..putting the sub and Taff's skills
under serious pressure.

You know, probably nobody's
watched this behaviour,

but they nervously go and look
at it, and then they go around

and they do a little test
and then they come back

and then they go for it.
Absolutely amazing.

All these years filming salmon,
it's the first time I've seen this.

This was the first time salmon had
been filmed leaping from underwater.

Finally, just a few salmon make it
to the top of the river.

The place in the river where they
themselves hatched as young salmon.

When breeding, they are
at their most sensitive,

and getting these intimate moments
needs some serious dedication.

I'll film every day other than
Christmas Day and Boxing Day

and I would film on Christmas Day
if my wife would let me,

but she does not let me do that.

I've been doing this
for about five years,

so we know when and where
the fish are going to spawn now.

So, that's the key thing -
is knowing where they are.

With spawning complete,
the salmon's journey is done.

But for the crew, there's
one final part of the story.

And they've waited three years
for the perfect conditions.

Not a very elegant slide,

but this is a really cool slide.

An otter slide.

A clear indication there's
one nearby.

Otters are usually very elusive
during the day.

These cold conditions
gave Raymond his chance.

I can see the otter
further downriver.

It's just come out onto the
ice shelf on the side there.

It's only staying for, like,
three or four seconds,

then it's back in the water.

It's hard work, this.

At the very end of their journey,
the salmon not only provide

a much-needed meal for this otter,

their dying bodies will provide
essential nutrients,

enriching the upper reaches
of our rivers.

Salmon once swam in rivers
throughout the British Isles

in huge numbers,
but in the last 25 years

the number returning from
the sea has dropped by 70%.

In England and Wales,
the situation is critical,

with over 90% of salmon river
populations at risk of collapse.

Having filmed them in all these
different places

and all these different
environments,

it's really brought home that,
you know,

we really are messing with them
every step of the way.

Our man-made barriers
block their migration routes.

Sewage from towns and cities

and agricultural run-off from farms
pollute our rivers,

making the salmon more
susceptible to disease.

On top of all this,
climate change presents them

with even greater challenges.

They need cold, clean water.
That's what they need.

And a lot of areas,
they're not getting that.

Anything over 23 degrees,
they stop feeding,

and anything over 30,
they die within minutes.

We need to look at trying to
manage those water temperatures.

And if we can bring
that habitat back -

in effect, rewild those bits
of rivers to put them

to how they should historically have
been, it's going to have

a knock-on benefit for all the
species that use the ecosystem.

Salmon are resilient animals.

If we can improve the quality
of our freshwater,

remove barriers to its flow

and better manage the challenges
at sea...

..salmon could once more
become abundant

across the British Isles.

Next time - our ocean.

A hidden world...

..full of colour...

..and surprise.

The Open University has
produced a free poster

exploring our wild isles and their
diverse habitats and species.

Order your copy by calling
0300 303 0265

and follow the links
through the Open University.

If you'd like to play your part
in restoring our wild isles

and learn more about
what you can do to help,

just search Wild Isles
on the BBC website.

The Open University has produced
an interactive map

exploring our wild isles

and their diverse habitats
and species.

and follow the links to
The Open University

to find out more.

If you would like to play your part
in restoring our wild isles,

and learn more about what you can
do to help,

just search Wild Isles
on the BBC website.