Original subtitles

Experience a world beyond imagination

where fish can fly...

lizards walk on water,

apes master tools

and frogs disappear in plain sight.

Animals do the smartest things...

through every stage of their lives.

From leaving home...

to raising a family.

From finding food...

to making friends.

They find ingenious ways to survive

against all odds.

Welcome to The Secret Lives of Animals.

On an island off the coast of Australia...

this fur seal is just a few days old.

He still relies on his mother for milk.

To keep him well-fed, she must go fishing.

Leaving him alone for the first time.

At this age, he should stay in the safety of his hilltop home...

and wait for her to come back.

But curiosity gets the better of him.

This is the first major milestone in his life.

And the early steps are the most difficult.

Going it alone, he's lost and vulnerable.

Without help, even the smallest mistake could lead to disaster.

He tumbles 100 feet towards the ocean edge.

And his situation quickly turns from bad to worse.

He's too young to tackle the rough seas alone.

And his fur won't be waterproof for another two months.

So every second he's in the ocean, he gets colder and weaker.

And his chances of survival are reduced.

He's at the mercy of Mother Nature.

Saved by the sea.

But he's exhausted, hungry, and still too young to feed himself.

Out of the hundreds of seals here,

only one can save him.

His mum.

But to him, all adults look the same.

And worse still,

they're ferociously protective of their own young.

A lone pup could easily be killed.

He must do something extraordinary to survive.

He remembers his mother's unique call.

Which he learned within the first four hours of his life.

That's faster than any other mammal.

Even humans.

So he can pinpoint the sound of his mum

among the hundreds of others

and make it to safety.

Leaving home is full of unexpected challenges.

One wrong move could be your last.

But if you have the right skills

and make smart choices,

it could be the start of life's great adventure.

Leaving home for the first time is a daunting prospect.

And in the jungles of Costa Rica,

this young basilisk lizard would stay here forever if he could.

He has a waterside view...

a sunny aspect...

and all the food he could wish for.

But it's so desirable...

this large male wants to move in,

and he's not the sharing type.

When it comes to a basilisk showdown,

bigger is better.

He stands no chance in a fight.

And forced to the edge of his territory...

he must leave the only home he's ever known.

But trapped by the river,

he'll need a miracle to escape.

He can walk on water.

His rear feet are almost half the size of his leg.

And he uses them to stop himself sinking.

Slapping them hard against the water to create an air pocket.

Then he lifts his foot out of the bubble before it bursts.

An extraordinary means of escape.

No wonder he's also known as the Jesus Christ lizard.

Working out how to leave home is just the start of the battle.

The next great challenge is deciding where to go.

Because that could shape the rest of your life.

High in the mountain streams of Trinidad...

this killifish was born into a crowded world.

There's not enough food for the whole family.

And tensions are rising.

To thrive, she must leave.

The best place for her to go is far upstream.

A fresh pool away from her home.

But blocking her path are boulders, ravines and waterfalls.

Surely an impossible journey for a fish the size of your finger.

Most killifish stay at home

and try to survive amidst the competition.

But she's one of just 10% that have an urge to explore.

She launches herself...

onto dry land.

It seems suicidal.

Out here, her gills can't work.

Most fish would pass out within minutes.

And she still has a long way to go to reach her new home.

So, she shifts her weight onto her tail

and leaps into the air...

flying an incredible eight times her own body length.

She can't afford to jump aimlessly.

So she looks for the telltale shimmer of water.

Then re-orientates her body

and backflips in the right direction.

But she's still a fish out of water.

To buy her time,

the blood in her tail runs so close to the surface of the skin...

it absorbs oxygen from the air...

and she can breathe through her tail.

In fact, she can survive for up to 15 hours out of water...

and travels 6,000 times her own body length

until she reaches...

her new home.

Perfect.

There's plenty of food here.

And she has it all to herself.

For some, the hardest part of leaving home is the journey to get there.

For others, it's finding your way once you arrive.

In an ancient English woodland

beneath the roots of an old maple...

this young wood mouse

is ready to leave her burrow to make her own way in life.

She travels up to one mile a night...

searching for the right spot to dig her own home.

This grassy field will do nicely.

But out here...

she's dangerously exposed.

A lucky escape...

this time.

And she has another problem.

She's just an inch off the ground,

and this field looks the same in every direction.

Getting lost could prove fatal.

Despite having a brain the size of a pea,

she does something very clever indeed.

She collects objects

and makes her very own signposts.

Something no other mammal, apart from us, is known to do.

While foraging, she keeps check on her marker.

The further she travels, the more signposts she creates.

Until her network of waypoints expands across the field.

Allowing her to roam this featureless landscape

without getting lost.

It's satnav for wood mice.

And when she needs a swift escape...

she knows just where to go.

Safe.

For some, leaving home is about starting a quieter life in solitude.

But for others,

home is where the herd is.

And when male African elephants reach adolescence,

their world turns upside down.

Staying with the herd is bad for the gene pool, so they're forced out.

This young elephant is alone and vulnerable.

To stand the best chance of survival...

he needs a new herd.

Using the most sensitive nose in the world,

he finds hope from three miles away.

A small herd of males.

With plenty of food.

And the safety of each other.

They could be his lifeline.

The trouble is...

they're on an island in the mighty Zambezi river,

which, right now, is in full flood.

Over half a million gallons of water

surge past these banks every single second.

Others have tried to cross with fatal consequences.

And if the river doesn't get you, what comes next will.

Three hundred feet high and a mile wide,

the largest waterfall on the planet...

Victoria Falls.

Young and bullish...

he tries to take the shortest route.

Straight to the island.

The current here is dangerously strong.

And he's quickly out of his depth.

Even for a five-ton elephant, this river is too powerful.

He's forced closer to the waterfall.

In desperation, he turns back.

He's lucky to survive.

He won't make this mistake again.

Like all his kind, he has one of the greatest minds in the animal kingdom.

He just needs to use it.

He heads upriver away from the island of bulls.

He's looking for somewhere the current will carry him to the island.

Remarkably, he seems to test the water.

It's just too strong here.

Could this be the right spot?

He's gambling with his life.

Off his feet, the river takes hold.

Success.

He's overcome one of the world's most dangerous rivers in peak flow.

And there's a welcome party waiting for him.

He's become part of an elite group of elephants

who've worked out how to cross this river.

And now he has access to the best food in the area,

a new herd and a new home.

Leaving home is a rite of passage.

It takes great skill to know when to leave,

where to go,

and how to find your way when you get there.

Get it right, and you're well on your way to adulthood.

To capture an extraordinary elephant

making one of the most perilous river crossings in the world...

the team needed to be in the right place at precisely the right time.

Which would be impossible without the expert knowledge

of wildlife cinematographer Tom Varley.

I first moved to Victoria Falls when I was ten years old.

I'm almost 50 now.

Over time, you build up a relationship with the elephants

and they get to recognize the sound of your voice.

They recognize the sound of your boat.

So it entitles you to be able to get close to them.

It's the end of the wet season.

And the river is dangerously swollen.

Most elephants avoid these treacherous waters,

but over the years, Tom has identified an elite group of males

who have learned how to make the crossing.

Fifteen years ago, there were no elephants swimming across to the island

when the water was really, really high.

Now, you have got a group of 15 to 20 bulls that have learned to do it.

But this year,

even these bulls are struggling to forge the Zambezi in full flood.

They might be a bit worried about this level of current.

The river is quite high

and it keeps coming up every day.

The rising water is making the elephants unpredictable.

Any mistakes could be fatal for both them...

and the crew.

The worst time to navigate the Zambezi would be now.

If you have a problem, you've got literally a couple of minutes

before you go over Victoria Falls itself.

It's an early start.

The team set about tracking down a bull brave enough to make the crossing.

Luckily, last night's chill has given Tom an idea.

Elephants do get cold.

Sometimes we find them up against the termite mounds

because they're the warmest parts of the islands.

There's no elephant here now.

But to Tom's expert eye, it's clear that a bull is nearby.

See where he's put his... the side of his body up against here.

So he would have leaned up against the termite mound to sleep.

And before long, he finds more signs.

There is fresh tracks of one leaving here

in the last sort of, like, three, four hours.

The search continues from the river.

Okay, we've got him.

He's directly where Sam is pointing, over.

This bull has already started to cross, but he seems hesitant.

He sort of tried to get into the current, changed his mind,

turned back, and went to the bushes.

To the crew's dismay,

the male disappears.

It's up to Tom to find him.

Jackpot.

Just looking to see if there's any warmth on the inside.

He's really, really, close. So, the hunt is on.

They need to be ready.

The bull could take the plunge at any moment.

He is swimming for Palm Island.

Say that again. Repeat, repeat.

- He's swimming to Palm Island. - He's swimming for Palm Island.

Okay, going now.

Yeah, drone's ready. He's coming.

Stay where you are. He's gonna swim.

Okay, copy that.

Okay. He's behind the tree now for me.

Shall we go down past him and shoot upstream? Over.

- Yes. He's coming. - Yes, go quickly. Over.

This is the moment they have been hoping for.

It's a huge relief.

Nice one.

He actually did it.

I mean, to see something that big to take on a river this big...

I mean, yeah, it's definitely battle of the giants.

Tom's got such incredible knowledge of this place.

He knows the ways that the elephants are gonna move through the landscape.

And today, thankfully, we managed to get the shots,

and it's because Tom knew where to bring us.

We could never have done it without him.

Next time...

the ever-changing challenge

that is raising a family.

It takes unwavering devotion...

a touch of magic,

and the help of friends and family

to give your child a head start in life.