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.

Our brothers and sisters are often the first friends we make.

And here on the tropical shores of Central America...

almost a hundred siblings are getting acquainted.

Calling from inside their eggs, hatching their first plan.

An olive ridley sea turtle, no bigger than your thumb,

faces a huge challenge to make it to the ocean.

First, he must escape his underground nest.

Alone, his chances of getting out are slim.

But working together,

the turtle hatchlings tunnel through over a foot of sand.

But they still have a long way to go

and danger awaits.

Black vultures are gathering and they're hungry.

Now, the genius of the turtle's strategy becomes clear.

Across this beach, thousands of nests have emerged.

Up to a million olive ridley hatchlings can surface in a single day.

Some of the largest gatherings of sea turtles on the planet.

By hatching together,

each turtle improves their chances of survival.

And about 80% of hatchlings make it to the ocean.

Working together, they've overcome their first great challenge in life.

It just goes to show, it's not only the fittest who survive.

It's often the friendliest.

The hot, dry forests of Costa Rica.

Summer temperatures here reach a searing 100 degrees Fahrenheit.

Life for this troop of capuchin monkeys is tough.

They make it through these difficult times with the support of friends.

But this youngster is new to the group and doesn't have any yet.

He's desperately thirsty.

At this time of year, water is scarce.

And the best drinking spot

is guarded by dominant members of the troop.

But desperate times call for desperate measures.

He tries his luck.

To get past the dominant monkeys...

and get a much-needed drink,

he must make a friend.

And capuchins do that in a way

unlike any other animal,

with an extraordinary test of trust...

that involves a sensitive nose...

and razor-sharp fingernails.

Capuchins really must pick their friends wisely.

Not quite.

Another lone capuchin.

This might be an opportunity.

He reaches for a finger

and guides it up his nostril...

very carefully.

Now, vulnerable, he's showing trust in the other capuchin.

And when they return the gesture,

it's the start of a beautiful friendship.

Together, they're ready to take on the world.

First stop...

the water hole.

It's still fiercely guarded.

The youngster's stopped in his tracks.

But this time, someone has his back.

Combining forces,

they confront the guard using a distinctive tactic.

With double the teeth and double the power...

they gain the upper hand.

For these monkeys, two heads really are better than one.

And they both finally get the drink they so desperately need.

Having even one friend can be a lifesaver.

So imagine having hundreds of thousands.

An army ant.

One of the rainforest's smallest animals

but part of one of its largest teams.

Up to a million strong,

this colony can't survive long without eating.

So, every morning,

the best hunters leave together with one mission.

To find food...

and lots of it.

They keep in constant communication through smell and touch.

And spread out into a column 20 meters wide

to flush prey out of hiding.

A bush cricket.

Too big for an ant to tackle alone,

but she doesn't have to.

She sends out an airborne chemical signal...

calling for reinforcements.

Her friends respond without delay.

Working together, army ants can take down animals

one and a half thousand times their own weight.

It's a good start,

but they need thousands of insects to keep the colony alive.

And finding food is only half the battle.

They must now carry it the ant-equivalent

of 22 miles back to the growing nest.

But in a jungle full of dead ends and detours,

that's a mammoth task.

With pinpoint precision,

these extraordinary creatures create their very own highways.

Smaller obstacles are no problem...

but to cross larger gaps,

they do something unrivaled in the natural world.

The ants link legs...

and support each other to engineer living bridges

ten times their body length.

These superstructures

allow them to carry up to 30,000 items of prey

back to feed the colony every single day.

They say a problem shared is a problem halved.

And often the most unlikely alliances turn out to be the most fruitful.

A three-toed sloth.

The slowest mammal on Earth.

And a prime target for the world's most powerful bird of prey.

The harpy eagle.

Capable of flying at up to 50 miles per hour.

And sloths are on their menu.

They can't run...

but a special relationship might just help them hide.

Sloth moths.

Up to 120 of them live exclusively amongst a sloth's coat.

They may not seem like good friendship material...

but almost all sloths have moths as housemates.

And they're welcome guests.

Scientists don't know exactly why,

but the more moths living on a sloth,

the more algae found in its fur.

It's thought moths provide nutrients that help the algae flourish.

And algae turns their coat forest green.

Helping these laid-back leaf-eaters hide

in plain sight.

When life gets tough,

you need friends that have your back.

But even the strongest friendships are open to betrayal.

South Africa's Kalahari Desert.

Here, meerkats feed on grubs and bugs hidden underground

for up to eight hours a day.

But with their heads buried in the sand,

they're blind to danger.

To keep safe...

they rely on friends in high places.

A fork-tailed drongo.

From her vantage point, she can spot danger a mile off.

A tawny eagle.

A meerkat's worst nightmare.

The drongo sounds the alarm.

A meerkat call confirms the danger.

Some friends you simply can't live without...

but she's not as selfless as it seems.

There's something in it for her.

A juicy grub...

abandoned by the meerkats.

Once she's finished...

she lets them know

it's safe to go back to foraging.

A scorpion.

A meerkat's favorite meal.

And so irresistible to a drongo,

she'll test their friendship to get it.

She makes another alarm call.

This time, it's a trick.

There's no sign of danger,

and the meerkats aren't so easily fooled.

So she tries something even sneakier.

A call they can't ignore.

A faultless imitation of a meerkat's own alarm.

Now the drongo gets exactly what she wants.

Sometimes she's selfish.

But meerkats are smart

and they know they're better off with her around.

No friend is perfect...

but there are times in life when you simply can't afford to be picky.

The Peruvian jungle...

at night.

Here, danger lurks around every corner.

Especially when you're just the size of a grape.

Like this reticulated humming frog.

The perfect meal...

for a banded cat-eyed snake.

Armed with excellent night vision,

and an incredible sense of smell...

he can run, but he can't hide.

If ever he needed a friend, it's now.

A tarantula...

armed and dangerous.

But not to reticulated humming frogs.

She provides them protection.

Capable of attacking snakes,

tarantulas are the jungle's most unlikely heroes.

This is an extraordinary friendship

that few people have ever witnessed.

And like all the best relationships, there's something in it for both of them.

This tarantula also has a problem...

parasites she can't reach.

They could be irritating to her,

but these frogs dine out on them.

It's a pairing so successful

that frogs and tarantulas are found living together

in jungles across the world.

When life gets difficult,

there's nothing better than having someone to lean on.

With friendship comes great rewards...

security...

support...

even lifesaving protection.

It's no wonder, with friends by our side,

we live longer, healthier and happier.

To film army ants building bridges,

the team headed to Costa Rica.

Welcome to the jungle.

In the dense rainforest,

finding the ants is only possible with a highly trained eye.

The challenging part is that they're rare

and so you often have to travel long distances

through the forest to find them.

After several hours of searching, Sean strikes gold.

We've hit pay dirt.

There they are. We've found it.

Now, filming can begin.

The bridge is the thing that we wanna get more than anything else.

It's the best example of teamwork, probably, that we can see.

But it's immediately clear it will be a challenge.

They are fast, they're small, and it's just really hard

to get the equipment close up to them.

And it's not just their speed that's a problem.

Soldier ant! It won't...

It's like having a hot needle stabbed into your skin.

I've got ants all over me.

Well, they're all over the camera.

They've bitten us, stung us, and we're out of here.

We're fleeing.

To have any chance of filming the ants' bridge-building,

they'll need to rethink their strategy.

We're having to come up with some ingenious methods

of stopping them climbing up your Wellies.

So Mark has got gaffer tape wrapped around his boots.

It's an amazing, simple solution.

It's just really slippery.

Today, I haven't been bothered at all.

And that's not the team's only stroke of genius.

Every time an ant gets on a lens or a lead or a light,

we brush the ant off with our ethical ant-remover.

But as quickly as they solve two problems, a bigger one emerges.

Well, I just did my morning check and...

it's a little frustrating 'cause the ants are gone.

So, we have more work ahead of us.

We're gonna have to keep tracking the ants.

There's only one more day of filming to go...

and the team has no idea where the colony has gone.

Feeling a bit worried. A bit pressured.

Just as they're giving up hope...

There it is.

This is definitely where they're building,

and hopefully they'll build us some beautiful bridges.

The team's luck has changed.

Just below their feet, construction has begun.

So, we're throwing everything at it, and seeing if we can get some good shots.

Yeah. Learning from the ants.

Working together as a team

to try and make the most of this one opportunity that we've got.

But these master builders don't stop at one bridge.

Oh, wow. That's beautiful.

You can see all their legs silhouetted against the forest.

How they're all interlinked. It's incredible.

I think this is one of the greatest events in all of biology.

It all came down to the wire on the last day,

but we did it.

Next time...

Finding a partner is a labor of love.

One mistake can leave you lonely.

But if you show off your best side

and make a good impression,

you might just meet your perfect match.