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.

We all need somewhere to call home.

And deep in the rainforests of Borneo...

this sun bear is house hunting.

She needs a new place to sleep every night

because she's always roaming for food.

But when you live in a rainforest packed with creepy crawlies...

finding a cozy spot to bed down is tricky.

And if things weren't uncomfortable enough,

in this forest, it never rains, it pours.

This would dampen anyone's spirits.

Worse still, the rain awakens the nightmare neighbors.

Tiger leeches.

Hundreds of them.

Each able to eat six times its body weight in blood.

But there's one place the leeches won't go,

and that's up.

Sun bear's claws can grow twice as large as a grizzly's.

So they can shimmy up a tree in no time

to a dizzying 130 feet.

But trees are not designed for sleepy bears.

Not comfy.

Still awake.

No, enough is enough.

This clever bear knows exactly what to do.

She chooses the perfect location.

Somewhere sheltered with a handy fork in its branches to build on.

And she does something rarely seen in the animal kingdom.

She begins to weave.

Carefully tensioning each branch.

And weighing them down into position.

She's building a bear-sized bed.

And for a spot of luxury,

she tops it with fresh leaves.

Like many dwellings in nature, hers is temporary.

But it provides comfort and safety.

Just like all the best places to live.

Owning your first home is one of life's great landmarks.

And building it yourself is a labor of love.

In southern Thailand,

this male baya weaver is facing a daunting project.

He needs to craft

one of the most intricate constructions in the natural world.

Woven from around 1,000 strands of grass,

his nest must not only attract a mate and keep her eggs safe...

it must also withstand

a monsoon storm.

The right building material is essential.

And he knows just the thing.

Bulrush grass.

It's pliable and waterproof.

But working with it is challenging.

And he's tying himself in knots.

He threads the strand around a branch.

Then back through the loop.

A faultless half hitch.

One down,

999 to go.

If his nest is to survive, he'll need a solid foundation.

And there's no cutting corners when your future depends on it.

This female will only mate with the best builder.

And the other males are putting him to shame.

He must up his game.

He weaves the egg chamber,

carefully tensioning every single strand.

But a nest this light could easily be destroyed in the wind.

He needs to find a solution fast.

Pellets of clay...

will add stability.

After 11 days, he's almost finished.

Will his new build win him a mate?

A flutter of her wings...

shows her approval.

She'll lay her eggs in the next few days.

But the storm is approaching.

He reinforces the foundations,

weaving extra strips of bulrush grass around the tree's thorns.

With eggs laid, his nest faces the ultimate test.

The monsoon winds.

His future hangs in the balance.

The colony has taken a hit.

But many nests have stood firm.

Including his.

It will safely house his chicks

until they fly the nest in around two weeks' time.

Building a family home from scratch takes hard work,

and carries a lot of risk.

Sometimes it's easier to restore an old property.

A beaver couple...

in the mountains of North America.

They've taken on a major renovation project.

This mud and log lodge was abandoned and is falling to bits.

Fixing it up is a massive undertaking.

Even for one of nature's most famous builders.

The walls may be a foot thick...

but they're full of holes.

And time is not on their side.

Winter has arrived on the mountain tops...

and will soon reach their valley.

They must hunker down in their lodge for four freezing months.

They won't survive if their renovation isn't finished.

To seal the holes, they need a flexible filler.

Dredged mud and grass is perfect.

They know it will plug even the smallest nook and cranny.

And will work as insulation.

But something doesn't sound right.

Running water.

Alarming for any homeowner, especially beavers.

To survive, they need not just a lodge, but a dam.

The dam holds back a river, creating a lake.

Deep enough for beavers to swim away from predators.

If the level drops, they'll be vulnerable.

She checks out the damage...

and comes up with a plan.

First, large logs to underpin the repair.

Placing them at an angle will give the dam more support.

He adds a barrier of carefully selected stones.

Then finishes the wall with smaller logs.

Sealed with trusty dredged mud.

Job done.

But like builders the world over, they're behind schedule.

And winter is here.

Soon it will be too cold for the beavers to survive outside.

Their lodge will be their sanctuary.

But only if they can finish insulating it in time.

As the temperature plummets to minus four degrees Fahrenheit...

the only creatures outside are those adapted to these bitter extremes.

He's safe.

And so is she.

Their tireless building efforts have paid off.

Holes repaired and perfectly insulated.

The temperature in here is an incredible 30 degrees warmer.

They'll stay in their cozy winter sanctuary safe until the spring.

In such extreme locations,

a home provides vital protection from the elements.

But in other areas,

properties are all about attracting attention.

This male black palm cockatoo lives in Queensland, Australia.

He's on a tight house hunting deadline.

It's breeding season...

and his lifelong partner lays just one precious egg every two years.

And she'll only do that,

if he can find her the perfect home.

He's looking for a solid, hollow tree trunk.

Easier said than done.

Over the last decade,

intense bushfires have burnt many to the ground.

This one is spacious...

but its foundations leave a lot to be desired.

Looks promising.

Or maybe not.

With less property on the market, demand is high.

He's running out of options.

This trunk is hollow, solid and tall.

It looks perfect.

To him at least.

She needs convincing.

He starts to build a platform to support her egg.

Still not interested.

But he has a clever trick up his sleeve.

He needs a stick.

Just the right size.

Now he's ready for a special performance,

unique in the animal kingdom.

He drums.

The sound may just persuade her

this is the solid home she's been looking for.

Finally, he has her attention.

A blush of her cheek...

shows he's back in the good books.

And she has a safe, secure home to lay her egg.

If you think building a family home on land is difficult...

try the ocean.

Off the coast of Japan...

a white-spotted Japanese puffer fish.

He's a little broody

and needs to build an impressive home to attract a mate.

But on this vast, empty plain, all he has to work with is sand.

And there's the constant danger...

that his efforts will be swept away.

It's a huge task for a fish not much larger than a credit card.

He starts by sieving the sand with his pectoral fins.

Moving the finest grains to the center

to make a soft bed for eggs.

And to ensure they won't be swept away,

he creates a series of channels and peaks to slow the current.

This could take some time.

About eight days.

After moving around 2,500 times his body mass in sand...

he's almost done.

His clever design allows the water to flow in from multiple directions,

aerating the eggs, encouraging them to hatch.

His creation has caught the eye of a female.

And also

a hungry goatfish searching for food.

A potential home-wrecker.

If he can't see off the intruder,

his future will be in pieces.

Disaster averted.

A few repairs and a little zhuzh,

he has the female hook, line and sinker.

She lays her eggs, he fertilizes them.

And he'll tend them until they hatch

into a home that's out of this world.

Building a home takes precise engineering...

creativity...

and a heap of hard work.

Get it right

and you have security,

comfort and a place to call your own.

Deep in the heart of the Bornean rainforest,

the team faced an unusual challenge.

They wanted to film a sun bear building a nest in the jungle canopy.

A rarely observed behavior that requires some lateral thinking.

The main issue that we're having

is that they build those nests up high.

We have to somehow get a camera up there with them

in order to see what they're doing.

To get the best view possible,

the crew will need to work from filming platforms 100 feet up in the canopy.

And that takes precision planning.

We've got to start to try and get into the mind of a bear

and decide where we put our platform,

which is pretty tricky.

Hoisting each 80-pound platform ten stories high

is backbreaking work.

And there's an added complexity.

Sun bears make a different nest every night.

One of the trickier elements of setting a tree platform

is that once you've chosen your location, you can't move.

- Yeah. - Oh, okay.

So they've come prepared with a secret weapon.

We do have a trick up our sleeves, however,

which is the use of a 30-foot crane

that gives us a bit more scope to move about the canopy,

as the bear's deciding which tree to nest in.

The team hope that this two-pronged approach

will get them the shots they need.

But no matter how much you prepare,

animals play by their own rules.

We arrived this morning to see that she's made a postcard perfect nest

right on the end of our crane.

She'd done that last night,

that would have been perfect.

But this sun bear isn't playing ball.

Opting to tease the crew instead.

Everyone's gonna think it's so easy.

Filming wildlife is rarely straightforward.

But, eventually, it looks like the sun bear is starting to cooperate.

The team's planning may just pay off.

All they can do now is wait patiently.

There.

And, finally, they capture her elusive nest-building on camera.

We've been waiting, waiting, waiting for this to happen.

It's just so cool to see in film.

Using this jib gives you this intimacy that is lost

when you're on the end of a thousand millimeter lens.

It's a triumphant success

and gives us an insight into the secret lives of these incredible creatures.

We pretty much got everything that we set out to capture

plus a few extra little bonus pieces, which is amazing.

A real privilege.

It just goes to show

that even with the latest technology at your disposal...

it's the animals who call the shots.

Next time...

The most essential part of survival is finding food.

Knowing where to get it

and how to catch it

is a constant challenge.

Because in the animal kingdom...

there's no such thing as a free lunch.