The Mating Game (2021): Season 1, Episode 4 - Freshwater: Timing is Everything - full transcript

Fresh water.
Some animals can't breed without it.

But correctly predicting its arrival
can be the difference between success...

and disaster.

A giant African bullfrog.

He's the size of a dinner plate
and he weighs half a kilo.

He's been buried
for the last six months.

Now, he needs to find a mate.

And he doesn't have long.

The newly-arrived rains
have created pools

that trigger this year's
mating jamboree.

He's not the first to the party.
And what is more,



it will be all over within
the next 24 hours.

This pool is already crowded with males,
like a downtown bar on a Friday night.

The females will soon arrive,
ready to lay their eggs,

so this is where a male needs to be.

But the battle-scarred faces
are a warning.

This pond is not for the faint-hearted.

The males occupy the centre of the pond
and fight to hold a place there.

Their calls will attract females,

but they will have to get to the centre
if they're to meet the strongest males.

So, if a male is going to mate,
that's where he needs to be.

Which for a latecomer
means running the gauntlet.

As any prize fighter knows...

dodging the hits is all part
of winning the bout.

And by doing what frogs do best,



he reaches the centre unscathed.

But his victory may not last long.

New contenders are arriving.

And this is one of those
they've all been waiting for...

a female.

She wants to get to the centre, too.

After all, that's where she will meet
the strongest males.

Swimming there underwater
is her best chance of reaching them.

If a male is to mate,
he must stay in the centre

and he won't be able
to do that without a fight.

These battles are no-holds-barred
and can even be fatal

The late-comer accepts defeat.

Not everyone can win in the mating game.

So, it's his rival who holds
the centre of the pond

and gets the females.

The pool will soon dry up.

So for this year, at least,

he's missed his chance.

Patagonia...

On the high plateau
the spring thaw reveals a land of lakes.

The water here comes not from rains,
but from melting snow and ice.

One of the rarest birds in the world
travels long distances

to get here and breed.

A hooded grebe.

One of just 700 that still survive.

This is a female,
so she's extremely important

if this species is to survive.

She doesn't fight to claim a mate.

She dances.

The most experienced males
are the best dancers

because they've done all this before.

So her challenge is to mate
with one of them.

To do that she will have
to prove that she, too, can dance.

Just getting noticed would be a start.

Couples are pairing off all around,
but her calls go unanswered.

Two is company...

and as perhaps she should have known,
three is a crowd.

A solitary male
must be a better possibility.

But he's not keen, either.

The lakes will freeze again before long.

So, an invitation to dance
is a very welcome sign.

But a rival for his affections

brings it to a swift end.

And just as she was getting started.

It's not going well.

And if she can't have him,

perhaps finding a gift for him
will help.

If she can find a partner,
they will nest among the milf oil plants

when its flowers appear
on the water surface.

Presenting strands of it
Is part of the courtship ritual.

She just needs to find someone
to give it to.

His bending over backwards is perhaps
a sign that he is not interested.

But who is this?

Could he be the dance partner
that she's been looking for?

The timing of her moves is crucial.

His precision shows
that he's danced this routine before

and, more importantly,
that he has already been a parent.

It's looking good.

Finally, having completed
the performance, she seals their bond

with a strand of milf oil

a symbol of their commitment
to the work ahead,

and one of hope for the survival
of this most endangered of birds.

Many species migrate to lakes
at a specific time in order to breed.

And for some,
doing so comes at great cost.

This female sockeye salmon
started from far out

in the Pacific Ocean.

And then continued up
one of Alaska's great rivers

for a further 160 miles
in order to reach Iliamna Lake.

Her arrival coincides
with that of others.

Lots of them.

Every summer, over three
and a half million sockeye come here.

It's the largest
salmon run in the world.

When they enter freshwater,
they stop feeding.

So, the bodies of the females
now have room for developing eggs.

But their energy is dwindling,
and they have yet to reach

the spawning grounds
that lie upstream beyond the lake.

But now, they face
more immediate threats.

While they try desperately
to evade the grizzly bears

that attack them from the lake shore...

...another threat comes from deep water.

Iliamna Lake is home
to freshwater seals.

Despite these onslaughts,
great numbers of the migrants survive

and swim on upstream, undeterred.

There are far more salmon
than the predators can eat.

At last, they reach the shallow streams.

So far on their journey,
there has been safety in numbers.

But now, at the spawning ground,
it's every fish for itself.

A female starts digging a nest

and quickly attracts
the attention of a male.

Quivering his fins
ls a male's version of a pickup line.

She has a mate for now,

but with more fish continuing to arrive,
room for nests is running out.

Rival females try to steal her mate,
her nest or both.

But she quickly sees them off.

Nests now cover the stream bed.

She releases her eggs,

he fertilises them,

and their work is done.

But she doesn't start
on a return journey.

This was always a one-way trip.

None of the salmon, male or female,
has eaten since leaving the ocean.

And now, their exhausted bodies
begin to collapse.

Pacific salmon only breed
once in their lives.

And having done so,

they die.

They seemed inexhaustible while being
driven by the urge to reproduce.

These have won the mating game,

but it cost them their lives to do so.

Salmon from the Pacific
migrate in their search

to find a safe place to lay their eggs.

But when suitable sites for nests
are particularly rare,

competition can get intense.

These are the Appalachian Mountains
in the eastern United States.

Here, in just a very few rivers,

live monsters
with a truly ancient ancestry.

Some call them "snot otters”,

others "mud devils".

Their most common name,
however, is hell bender.

But common, they are not.

Hellbenders are very rare indeed.

This male is very well camouflaged,
and he rarely moves.

So, in practice, he's almost invisible.

Hellbenders are
a kind of giant salamander.

He may grow up to 60 centimetres long.

They're usually very shy.

But during the few weeks each year
when summer turns to autumn

and the river starts
to flow more strongly,

the hellbenders start to move around.

He's looking for somewhere to nest.

A rock, but not just any rock.

This particular slab, he knows well.

He's chosen it before.

Such rare, heavier stones
don't get easily washed away.

The space underneath it,

ls well-hidden and the current
flowing swiftly through it

will bring the oxygen needed
for developing eggs.

The females are already on the move,
battling their way upstream towards him.

He just needs to hold on to his den
until they get there.

But every year,
other males arrive to challenge him.

They come at him from all sides.

They're even lining up
to try and take over his den.

But as he fights, the strong current
carries him away from the den

and another rival sees a chance.

Back in the nick of time.

Exhausting.

But this is the time
when he has to secure a mate.

With temperatures dropping,
the turbulent winter water

becomes rich in oxygen
needed by developing eggs.

These days, increasing erosion
of the land

is blocking hell bender dens
with sediment.

So now this one, more than ever,
is worth fighting for.

He's been forced out of his home.

But after all he's been through,
he's not about to concede.

His rival gives up.

He is still the boss.

And now, at last a welcome visitor.

He greets her with what is known
to hell bender watchers,

as a "courtship kiss".

Her belly is full of eggs
and she slips in beside him.

Then strangely, after days of brawling,

rival males are also allowed to enter.

Perhaps, he's now
too exhausted to fight,

or has some strategy
we don't know about.

Other females then visit the den
and add their eggs

to the communal clutch
which he will protect.

He has become a babysitter
for the whole hell bender community.

In the freshwater world,

it's often the males
who look after the young.

But even when these duties
are left to one parent,

the mating game may still demand
carefully-timed coordination.

In South America,
water levels across the Amazon Basin

rise and fall with the seasonal rains.

If this male Splash Tetra
Is going to mate successfully,

he needs the water level to rise.

It's low at the moment,

but every drop of rain
brings it closer to his requirements.

As the rain begins to ease,

he tries to find out
if he's high enough yet.

A few well-aimed splashes
help him to estimate the distance.

He's looking for a place where a female
can lay her eggs away from predators.

But to assess the situation properly,
he does something truly extraordinary.

The water he splashes on to the leaf

momentarily delays
his fall back into the river.

Now, he turns his attention
to a female...

because what comes next
needs the two of them.

If they're to mate successfully,
they must hit the leaf simultaneously.

After she's laid her eggs,

he spreads his jaw and fins

to help him cling on
Just long enough to fertilize them.

This extraordinary way of laying

keeps their eggs safe
from underwater predators.

But for him,
it creates one final challenge.

Out of the water, the eggs
are in danger of drying out.

Problem solved.

With the female gone,

he alone takes the responsibility
for ensuring their eggs will stay wet,

until they hatch in a few days' time.

The Splash Tetra pair
had to synchronize their moves.

But in other cases, the mating game

requires thousands of individuals
to work in harmony.

In the great Rift Valley of East Africa,
fractures in the earth's crust

have been filled with fresh water

over millions of years
by the annual rains.

But in many of these lakes,
the water doesn't stay fresh for long.

Scalding volcanic waters
from deep below ground

carry up salts dissolved from the rocks.

Not much is able to live in these
caustic lakes,

but one kind of bird flocks to them.

Lesser flamingos gather here in millions
to feed on the microscopic algae,

that develop
in these super salty waters.

A male flamingo must be well-fed
before he can mate.

And the algae and other microorganisms
that flourish in these briny waters

are the only things
that lesser flamingos eat.

But these organisms also contain toxins.

The birds do not digest
these substances,

but store them in their plumage,
out of harm's way,

and it's these that turns them pink.

The more well-fed he is,
the rosier he becomes

and the more attractive he is
to his potential mate.

As the water gets deeper,

the flamingos have to find new ways
to collect their food.

He's getting pinker with every mouthful.

There is a female out there for him,
but he can only find her

when she and all his friends
in the flock are pink enough

to begin their courtship dance.

Each morning, the birds gather
around the hot springs to drink

and show off their newly pink feathers.

It's a chance to see
who is ready for dancing.

With his plumage in proper order,

he's keen to get the party started
and show off to a female.

After weeks of feeding,
with the whole flock in full colour,

it seems that everyone
is finally in the mood.

Dance fever spreads
throughout the flock.

And at last, the performance begins.

Both males and females are dancing.

Groups merge
and coordinate their courtship.

Laying their eggs
at exactly the same time

maximises their chicks'
chance of survival.

And dancing together ensures that
they're all in sync with one another.

If two birds find
what they're looking for,

they leave the dancing group.

Exactly how a partner is chosen,
we don't fully understand.

But it seems that some flamingos
try to select a partner

with the same shade of pink
as themselves.

Though, how they judge that
is still a mystery.

Lesser flamingos may have
to wait many years

before the water conditions are right
to enable them to mate.

But there are lakes
where securing a mate

can be a year-round preoccupation.

Lake Tanganyika in East Africa
ls enormous,

deep and warm,

and it's been this way
for millions of years.

Long-term stability
allows long-term mating strategies.

This pile of shells, for example,
Is constantly getting bigger.

It's likely to be several decades old.

It's certainly older
than the current ruler...

a male callipterus fish.

He is an underwater architect

and busy collecting empty snail shells
to add to his castle.

His pile is home to over 20 females
who lay their eggs inside the shells.

He does his best to ensure
that they only mate with him.

And doing so is a full-time job.

There are eels here...

that would happily make a meal
of a shell-full of eggs.

But not if the king can prevent it.

He stole this castle of shells
from a previous owner.

And if he lets his guard down,
someone will certainly take it from him.

Gangs of marauding bachelors
are a constant nuisance.

And while the king of the shell-castle
is busy proving how tough he is,

he's being watched by a sneak.

He belongs to the same species,
but he's a dwarf.

He won't go any bigger
and he's ready to mate.

He just needs to get
near enough to a female.

He is only 1/50th
of the weight of the king,

and if he can reach a shell
with a female inside,

he's small enough to slip inside
and mate with her.

Busted!

Back to square one.

Every now and then, the king has
to tackle someone his own size.

A serious contender
is attempting to overthrow him.

Could this be a chance for the dwarf?

He's close!

Once inside with the female,
he can fertilise her eggs

without the king ever knowing
that he's been there.

He might not be the biggest fish,

but he's definitely got one
of the cheekiest strategies in the lake.

These shenanigans continue
month after month,

thanks to the lake's
extremely stable environment.

But some environments in Southern Africa
are far from stable.

The grassy plains in Zambia
change radically every year.

They flood.

Many are home to lechwe,
one of the most aquatic of antelopes.

With hooves that splay out wide
and extra strong hind legs,

this female is able to travel
across even deep swamps.

But their watery world is now shrinking.

It hasn't rained in months.

Before long, the swamp meadows
on which the lechwe depend, will be dry.

They turn into dusty plains

with just a few small,
muddy water holes.

This is the best time
for a female to find a mate.

In a few months' time,
when her young are born,

things will be easier.

So, it's at this point that she starts
to think about getting a partner.

Most of the time,

male and female lechwe
live quite separate lives.

She is now at her most fertile,

and she starts to leave the safety
of the female herd.

Alone, she's more vulnerable.

And the long, dry grass
away from the swamp

can only too easily conceal a lion.

She mustn't stay away
from the other females for long.

To survive here,
you must be fit and strong.

And those are exactly
the characteristics

she values in a mate.

The best place to find a male
with such qualities

is even further away from the water.

Out here on the dry plains,

the males are already
competing for females.

Stabbing the ground
with his horns is a male's way

of demonstrating his strength.

His next move is more direct.

She remains unconvinced,

but this performance has caught
the attention of a rival male.

She's here to mate
with the strongest male,

and these battles will help her decide
which one that is.

But they better get a move on.

There are plenty of other males
that she could choose.

Having seen off his rival,
he resumes his overtures to her.

Perhaps because they're vulnerable
when they get together,

their union is very brief.

Afterwards, he tries to remain close,
but she has other ideas.

Her instinct is to seek safety
in numbers.

She's got what she came for
and she heads back to the female herd.

She started her pregnancy
at just the right time

to give her offspring, when it arrives,
the best start in life.

In Brazil, this wetland, the Pantanal
also dries out every year.

And this is the time when,
like the lechwe, caiman breed.

But if he is to survive
long enough to mate,

this male will have to find
water of some kind.

The pool he came from has now dried up.

If he doesn't find a new one,
he will die.

The land is littered with the remains
of those who didn't reach water in time.

But he is heading for one place
where he knows

that water will remain
throughout the dry season.

He's made It.

And he's not the only one
to have done so.

So have thousands of others.

And it's not only water that's here.

There are females as well.

Late afternoon is a time to bask.

And although the dwindling pool
ls now very crowded,

they tolerate each other...

for the time being.

But by first light,
the mood has changed.

Surviving the drought
ls no longer a male's top priority.

If babies are to hatch out
when the high-water returns

and life is easier,
he needs to mate soon.

And if he's to do that he must claim
a patch of this water as his own.

Because there isn't room for everyone.

All around, males begin to assert
their dominance.

A newcomer must stand his ground
if he wants to remain a contender,

but he must also know when to back down.

And there is usually someone smaller
for him to pick on.

By mid-morning, an uneasy calm descends.

The newcomer has secured a patch.

But he still has to convince a female
that he's worth mating with.

And he has a plan.

It starts with a grunt.

The next part of his courtship song,
we can't hear,

but we can see It.

It ls not the muscular movements
of his body that make the water dance,

but the low frequency of his call.

This song contest may be inaudible
to us, but not to female caiman.

It attracts them from far and wide.

Despite his rival's best efforts,

it is the newcomer
who seems to be getting it right...

because he's got company.

The water is so murky
that actual mating is rarely visible.

But every now and then,

two caiman appear a little more
interested in one another,

and something is clearly going on
below the surface.

Timing is crucial...

As it is for all animals
that come to breed in those variable

and only too unpredictable
of the earth's environments...

its fresh waters.

In order to tell the story
of the breeding migration of red salmon,

The Mating Game team
had to choose the best location.

After months of research,

assistant producer,
Olly Scholey struck gold.

So the reason we've come on this shoot

really stems back to me just sitting
on Instagram on a Sunday evening

and just scrolling through pictures

and I saw this one photo of Iliamna Lake
that Jason had taken,

and was just completely sold
on coming here to film red salmon.

There's gin clear water and you can
Just immediately see in that picture

that there's a really fascinating
spawning dynamic going on here.

Jason Ching is a local salmon biologist

and world-renowned
wildlife photographer.

He has taken the crew to the exact
location where he took his picture.

Cinematographer, David Reichert

is hoping to film the details
of the salmon courtship as never before.

Filming underwater, one of
the big struggles is the visibility.

Being able to see a nice, sharp image.

So when I saw the picture from here,
that was really exciting for me

to be able to work in that kind of water

is, you know you're going to be
bringing home really beautiful stuff.

The crew
also want to capture the spectacle

of this huge salmon run from the air.

And this aerial perspective shows them
something completely unexpected.

Zoom in, zoom in.
Just keep it down.

Yeah, you've got control.

Hang on, hold up,
there's a seal, bottom left.

Okay, I'm moving forward.

Freshwater seals,
an incredibly rare animal,

were predating upon the salmon as they
kind of, bunched up in this river mouth.

He's...

7his seal behaviour
has never been filmed before,

and the crew now have to overcome
the far harder challenge,

of documenting it from underwater.

He's way down on that bottom right.

Freshwater seals are extremely shy.

So in order to do this,
the crew need to use remote cameras.

Hopefully, these are
going to capture that seal behaviour.

Seal attacking the salmon,

and that will go with the incredible
drone shots that we've already got.

Stop! Yes, perfect.

Looks good, mate. Horizon's good.

So if they come in,
if they come in and feed here,

we're going to get some pictures.

Here he comes, here he comes.

He's just sniffing around right now.

So we've just started getting some
little bits of the seals coming in,

but we're not quite in the right place.

We haven't been
in quite the right place,

but now, we've positioned it
right where we think

that this seal is going to stop and wait

and then jump up and grab a fish.

Fingers crossed it works.

Coming in.

Okay, he's getting in a good place
for this one.

After days of catching mere glimpses...

Now, that's a good shot.

...the crew finally have
their cameras in the perfect position.

Go, go, go, go, go. Yeah!

-So close!
-He missed.

There he is. See him coming in there.

He might be the charger.

Got him. Man, on both cameras!

It's a great success,

but it was only going to be
a matter of time

before the crew meet
the salmon's other predators.

There's a bear.

-Get ready with the cameras.
-Okay.

It's dangerous to surprise a grizzly,

so Olly lets the bear know
that the crew are close.

Hey, bear!

Hey, bear.

-I'm watching this bear.
-Yeah.

Hey, bear. Hey, bear.

That's close enough.

Hey, bear. Hey, bear. Stay back.

Obviously, hindsight is a lovely thing,

we re probably a bit too close
to the river and to all the fish.

I think we need to move back a little
bit and stay a bit further away.

This is his river, not our river,
so we'll let him catch his lunch.

I mean, it could be amazing,
as we've got this really clear water,

we could get some really unique shots
of bears walking through salmon

and be actually able
to see the whole bear.

The slight downside to that is
either the bear treads on the camera

or grabs it or does anything to it.

Basically, the plan is to put
quite an expensive camera

underneath the feet
of a charging bear, so...

David positions
the remote cameras in deeper water

in the hope of capturing
an extremely rare perspective

of a hunting grizzly bear.

-Still coming.
-Yeah. Maybe get out.

Okay, got him. Nice.

Yes. Okay, we've got him.

It works, and they
capture a salmon's eye view

of one of the biggest challenges
they face on their breeding migration.

Although, the plan for getting
the camera close to the bear works,

maybe a little bit too well.

We have to look at one upside down now,

because the bear's completely rolled it.

Is it intact?

Miraculously, the camera survives,

and it's now time for David to finish
telling the salmon"s story

by trying to film them spawning.

So we have found
Just a magical part of the world.

Just the amount of activity here,
it's just epic, what is happening.

What has really surprised me about
spending so much time with the salmon,

is really how intricate
this behaviour is.

There's so much going on with these fish

as they compete to be really,
the mating pair.

Yeah, fish, like, fish sex is...

You know, I feel,
like, a little awkward...

watching that for hours,

but they don't seem to care,
so I guess it's cool.

With some luck and some ingenuity,

the team capture almost every challenge
that the red salmon must overcome

in order to win the mating game.