Curious Minds David Attenborough's Natural Curiosities

The natural world is full of extraordinary animals

with amazing life histories.

Yet certain stories are more intriguing than most.

The mysteries of a butterfly's life cycle

or the strange biology of the emperor penguin.

Some of these creatures were surrounded

by myth and misunderstandings for a very long time.

And some have only recently revealed their secrets.

These are the animals that stand out from the crowd,

the curiosities I find particularly fascinating.

Orang-utans have an extraordinary ability to use tools

but the full extent of their skills remained undiscovered for centuries.

Surprisingly, crows also make tools.

How and why have these two very different animals become so inventive?

When I first saw orang-utans that had been raised in captivity using tools,

I was truly astonished.

They were extraordinarily skilful at imitating the things we do.

But at the time, such skills had never been observed

among wild orang-utans.

So, are these apes just clever mimics

or do they ever make and use tools in the wild?

We didn't know the answers to such questions until quite recently.

This dramatic sculpture by the French artist Emmanuel Fremiet,

entitled An Orang-utan Strangling A Borneo Native,

represents the image people had of this formidable giant ape.

It's pretty accurate, as Fremiet studied live orangs

at the Jardin des Plantes in Paris

and you can see why orangs are so called.

The name in Malay means "orang" - people - and "utan" - of the forest.

At first, orang-utans were feared and misunderstood.

Early explorers thought

that these long-armed, tree-living apes were degenerate human beings

and for centuries their true nature and behaviour in the wild

was largely unknown.

Orang-utans are only found in the rainforests of Indonesia -

one population in Borneo and another, slightly different one,

in the island of Sumatra to the west.

They have strong, dexterous hands and feet and a very mobile mouth

that enable them to break open and eat the fruits on which they depend.

But although they're clearly very intelligent,

the only tools they seemed to use were sticks,

which they wielded in a very simple way.

Yet in Africa, chimpanzees had been seen using tools

in a rather more complex fashion.

Back in 1871, Darwin had reported wild chimpanzees cracking open

walnut-like fruits with stones.

And in the 1960s they were even seen modifying sticks

with which they fished for termites.

It seemed strange that while wild chimps used tools in a quite complicated way,

orang-utans, apparently, did not.

Orangs, unlike chimps, are not very sociable.

Individuals are largely solitary.

The males have large individual territories

within which several females have their own home ranges.

This more solitary way of life affects

the way orangs share their knowledge and develop their skills.

The most social time of an orang-utan's life

is when it's a baby,

and in the wild, youngsters stay with their mothers

for the first six years of their lives.

During this time, they learn the skills

needed to survive in the forest alone.

They need to know how to climb, build nests

and how to solve problems such as breaking into tough food,

and their large brains certainly help them to master these tasks.

So, a young orang behaves like its mother

and copies the way she searches for food and prepares it to eat.

In captivity, they readily make tools

to reach food or to escape from their enclosures.

They're clearly very inventive

and good at developing ways to solve particular problems.

So, it was a puzzle as to why such bright and capable apes

were apparently not behaving in a similar way in the wild.

Orangs are clever and physically dexterous.

They have very strong jaws and mobile hands and feet

and in the wild they can reach and prise open most food.

It was assumed for many years

that even though they used tools in captivity,

they didn't perhaps need to do so in the wild.

It seems that, strangely, these great apes have more skills

than they normally need for their lives in the wild.

It wasn't until 1964 that orangs were studied in detail.

A Lithuanian scientist from Canada

called Birute Galdikas settled in Borneo

to live alongside these great apes.

For over 30 years, she watched both tame orangs

and wholly wild ones in the forests.

In her camp, she found that the tame ones quickly discovered

how to use tools in a relatively sophisticated way.

But in the wild, she only saw them build nests

and use sticks in a simple fashion.

That picture of the character and abilities of orangs

remained unchanged for a long time.

Then, in 1994, our understanding of orangs changed radically.

A group of Swiss scientists observed some orangs

that were behaving very differently.

They lived several hundred miles away from their Borneo cousins

in swampy rainforests on the island of Sumatra.

The orang's diet is about 90% fruit,

and this is one of their favourites.

It's a durian and it's well known -

ugh! - for its pungent smell.

As you can see, it's got a very spiky case,

but orangs are able to break it open

and reach the soft, pulpy flesh inside.

But it's when they tackle another similar spiky fruit, called neesia,

which is more difficult to open,

that scientists got their first glimpse of orangs making tools.

Neesia presents an extra challenge

because inside it contains rich, nutritious seeds

which are embedded in a mass of sharp, needle-like hairs.

To avoid touching these irritating hairs,

the swamp-living orangs slid sticks into cracks in the fruit husks.

Then they pushed them up and down

to flick out the hairs and free the seeds.

They also modified sticks

so that they fitted different-sized cracks in the fruits.

The particular fruit that grew in these wet forests

had stimulated the Sumatran orangs to make and use special tools.

Unusually for such solitary creatures,

they gathered at these rich feeding areas in a group

and, feeding close to one another, they shared their skills.

So now it was realised that orangs were not just mimics.

They were able to invent their own ways of making and using tools,

just like chimps.

We have long known that captive orangs can quickly work out

ways to solve problems

and now it was clear that wild orangs are no different.

In recent years, they've been seen using sticks to fish for termites and honey

in much the same way as individuals do in captivity.

In the flooded forests,

many insects are forced above ground to live in tree holes,

so the orangs use sticks to extract them.

It seems incredible

that tool use in wild orangs took hundreds of years to discover.

In fact, it had been happening all the time,

just hidden away from view.

These red men and women of the forest have

very dexterous hands and feet,

strong jaws and a large brain.

In the wild they have little need for complex tools,

and being solitary means that tool use is not usually shared or spread.

But even as loners, they are inventive

and can work out how to solve problems.

Here is a creature that could be one of the greatest tool users

in the animal kingdom.

Orang-utan tool use was not discovered for many years.

Next, meet the clever crow, that also makes tools.

How have crows' curious minds helped them become so inventive?

SQUAWKING

The most famous members of the crow family in Britain

are the ravens that live here in the Tower of London.

By tradition, they protect the Crown

and they are recruited and indeed dismissed from the British Army,

just like soldiers.

In 1986, one of them, called George, had to be exiled to Wales

for persistent bad behaviour

in destroying the television aerials around here.

And more recently, another one,

noticing that one of its fellows had died

and was attracting a great deal of attention,

also lay down on the ground, feigning death,

and when the Raven Master came over to see what the matter was,

he got a sharp peck.

Well, stories like those suggest

that members of the crow family have minds

rather different from other birds.

Ravens are cheeky, self-aware and socially intelligent.

They're part of the big crow family

that in Britain includes hooded and carrion crows,

jackdaws, jays, choughs and magpies.

Their brains are twice as large as other birds',

and, relative to body size, comparable to a chimpanzee's.

This extra brain capacity has helped them

become very good at solving problems.

Here is Bran the raven

and I've put a screen in front of his cage

so he can't see what's going on.

And this is Bran's stone.

He's had it since he was a chick

and he can recognise it amongst a whole pile of other pebbles.

Now, I've put a few of a similar size on this grid

and I'll put his stone just there.

And now we'll see whether he can find it.

Bran, where's your stone?

Immediately! Well done!

The only explanation of this

is that he has an extremely acute visual memory.

Indeed he has.

You could say that by putting stones on a gridded square like that

makes each one very obvious.

All right, well, let's make things a little more difficult.

This is his stone and I'll put it in this pile of stones

so that he can only see just a little tip of it.

Now, Bran, where's your stone?

Oh, come on!

HE CHUCKLES

Fantastic! Thank you very much.

And this ability to recognise a little, small detail

is used by these birds when they cache food.

In the good times, they will hide hundreds of different pieces of food

and conceal them and remember every one

and come back to it in the hard times to pick up that piece of food.

Extraordinary. You're an amazing bird, Bran.

Another species of crow, Clarke's nutcracker,

is a champion at caching food.

It collects and hides up to 33,000 seeds every season

and remembers where each one is put for up to nine months.

It can even find them under snow.

Crows also remember the kind of food that they have hidden.

Freshly buried grubs perish quickly,

so need to be recovered sooner than seeds.

The ability to think ahead and anticipate future events

can also help in other situations.

Other birds will steal buried food, if they can find it.

But some kinds of crows are able to recognise these thieves

and outwit them.

SQUAWKING

Recent research at Cambridge has revealed

that scrub jays take great care in how they hide their food.

One jay is given the choice of two locations in which to cache food -

under stones, which make a noise if they are moved,

or soil, which can be cleared away quietly.

In the cage next door, another scrub jay watches.

He's a potential thief.

When the caching jay knows that its neighbour can see,

it buries its food under stones.

If the jay next door attempts to steal that buried food,

the noisy stones will act like a burglar alarm.

But when a screen is added

so that the neighbouring jay can only hear what's happening,

the caching jay changes its plan.

This time, it decides to bury its food under soil,

which makes hardly any noise,

so its location remains unknown to the jay next door.

CAWING

For centuries, members of the crow family

have been recognised to be unusual birds.

Their noisy gatherings gave them a sinister reputation

but their intelligence was legendary.

In one of Aesop's fables,

a clever crow drops pebbles into a jug of water

to raise the level high enough so that it can drink.

This is perhaps one of the first recorded examples

of a crow using a tool.

Here, once again, is Bran the raven

and, like the crow in Aesop's fable,

he's extremely intelligent and clever at collecting food.

I'm going to set him a problem which he has seen before

and for which he produced his own solution.

I'm going to take a little bit of meat,

put it in this plastic bottle

and then, just to make it difficult for him,

I'm going to crush the bottle...

..so that it won't come out just by shaking it.

Now, then, Bran, how are you going to get that out?

HE LAUGHS

What he did was to take this bottle, put it in the water

and use the water to swill it out and collect the bit

and he did that in about ten seconds flat!

Bran, in effect, used the water as a tool.

And he's very quick to understand the potential of any object

and work out how it might help solve one of his problems.

All crows, it seems, have extraordinary memories,

acute vision and great ingenuity in devising tools.

In New Caledonia, a tropical island east of Australia,

wild crows use tools just as expertly and inventively as apes.

They fashion sticks to tease grubs out

from places they would otherwise find impossible to reach.

More recently, scientists discovered and filmed crows

that had taken their tool-making a stage further.

They were creating hooks

by carefully modifying the thick ends of twigs.

This seemed extraordinary,

but there were more surprises.

On the nearby island of Grande Terre,

the crows were making even more sophisticated implements.

These are the actual tools made by New Caledonian crows.

They're constructed from the leaves of the pandanus tree,

which have lines of sharp spikes along their margins

and the crows use them to winkle insects out of crevices.

But each population of these crows makes the tool in their own way.

This one is a broad strip.

This one, a very thin strip.

And these two, which come from the north of the island,

are used by two different populations.

One makes a two-step tool, thin at the end,

and this one makes a one-, two-, three-step tool.

In this rare footage,

the crow strips off the serrated edge of a leaf.

The series of small spines are better than just a single hook

because they can snag an insect along all its length.

Each population of the crows have their own design

which they pass on to the next generation.

So, just like us,

these New Caledonian crows have their own cultures,

their own inquisitive, curious minds,

which is pretty unusual for a bird.

Orang-utans in the wild make very simple tools.

But surprisingly, it's the smart crows that take the prize

for making the most sophisticated tools used by any animal.

Very clever.

Are we finished now?

Where's my lunch?