Life in the Trees Life on Earth

If you spend your life clambering about in trees,

two of the most useful things to have

are a pair of hands, with which to grip the branches,

and a pair of eyes, which face forward

and both can focus on the same thing

so that you can accurately judge the distance of, say,

the next branch on which you want to jump or swing.

There are about 200 different kinds of animals in the world

that have those two characteristics.

We group them together and call them primates,

and they include monkeys, apes, man...

..and those creatures over there,

that I'm watching in this tree in Madagascar.

At first sight, this animal doesn't look much like a monkey.

That bushy, ringed tail is more like a cat's.

And the long snout, with moist, bare skin around the nostrils,

gives it a rather dog-like look.

But its hands give away its true character.

No dog or cat has a grasp like this.

This creature is a true primate and one of the most primitive ones.

It's a lemur.

Lemurs are descended from shrew-like mammals

that scampered along the ground at the end of the age of the dinosaurs.

And this lemur, the ring-tail,

is as much at home on the ground as it is in the trees.

They still retain old habits more suited for ground-dwelling,

like scent-marking.

The males have horny spurs on their wrists, surrounded by glands.

And they click these against saplings,

so impregnating the scratch with musk.

The female smears musk from a gland beneath her tail.

Males find this especially attractive.

Having checked, he marks over the same spots himself.

Frequent marking enables a troop

to leave a scent record of its movements,

and so establish rights of way on the forest floor.

An angry male spreads scent onto his tail

by drawing it over his wrist and chest glands,

for perfume is also used in the battle for dominance.

He will then thrash it in the air

so that the scent is wafted towards his opponent, to intimidate him.

The lower male recharges his tail.

Grasping hands, so valuable to the adult

for holding on to branches, are also useful to the young.

Baby squirrels and tree shrews, with straightforward paws,

have to be deposited in nests of some kind

and are often abandoned while the parents gather food.

But lemurs have a different technique.

The little ones can close their fists on their parents' fur

and so accompany them wherever they go.

Lemurs were in their heyday about 40 to 50 million years ago.

Their fossils have been found in not only Africa, but Europe.

And about that time,

Madagascar became separated from the east coast of Africa.

There were lemurs living there, too, of course,

but because they were now living on an island,

they were protected from competition

with other, more intelligent, more efficient creatures

that were to develop elsewhere in the world later.

And so Madagascar became what it is now, a paradise for lemurs.

As well as the ring-tail, there are over 20 different kinds of lemurs,

each one adapted to a particular kind of life in the trees.

Down here in the south of the island, in this extraordinary spiny forest,

there is one that specialises in jumping.

It's called a sifaka.

And you could hardly fine a better demonstrator

of those two invaluable primate talents,

the ability to judge the distance of a jump

and to grasp a hold when you land.

The disproportionately long hind legs

that enable them to jump between trees so well

make walking on all fours impossible.

Another accomplished leaper

lives in the forests of north-east Madagascar,

but there it's more often heard than seen.

HAUNTING CALLS ECHO

The indri, the largest of the lemurs.

And it's no accident that it has a well-developed voice.

MOURNFUL CALLS CONTINUE

The thick canopy, in which the indri lives,

has turned it into a chorister.

Perhaps scent is too easily dispersed up here.

It's certainly difficult to see far.

So, safe from attack by predators,

it's much easier and more effective to use sound

to carry messages through the forest, to claim a territory

and register your whereabouts with your neighbours.

And few creatures do so more deafeningly than a family of indris.

IT WAILS LOUDLY

Other lemurs also use their voices to keep in touch with the troop.

These are brown lemurs.

IT GRUNTS

They often travel with the ring-tails,

which supplement their elaborate system of scent signals

with a repertoire of calls,

especially when the troop is on the move.

LEMURS GRUNT AND CALL

Out in the open, where they're more at risk,

the ring-tails keep together

and raise their vividly-marked tails like flags,

so that the members of the troop

can also maintain visual contact with one another.

This troop is going down to the river to drink.

LEMURS CHATTER AND CALL

As darkness approaches,

the forest rings to the sound of the lemur groups,

spacing themselves out as they settle down in the trees to sleep.

A VARIETY OF LEMURS CALL

Many lemurs are nocturnal, and when darkness falls

a completely new cast of them appears.

This is the smallest of all, little bigger than a mouse,

and CALLED a mouse lemur.

It eats insects as well as seeds and fruit

and enthusiastically marks its own section of a tree

by urinating on its hands

and planting smelly hand-prints all along the branches.

The rarest lemur, the aye-aye.

It may be on the verge of extinction.

A few still survive, but no-one knows how many.

It's the oddest of the lot,

gnawing into wood to expose beetle grubs.

It also has a taste for egg yolk, which it gets

by using its extraordinary long, bony middle finger as a probe.

In all, there are some 20 different species of lemur

still surviving in Madagascar.

Elsewhere in the world, however, the lemurs died out.

It seems they couldn't face the competition

from more advanced primates that were to develop later -

the monkeys.

That competition only came during the day

because, with one exception, all monkeys sleep at night.

And so the lemurs were able to survive by being nocturnal.

In Africa, there are the bushbabies,

which are very similar to the mouse lemurs of Madagascar.

There's also the potto.

And here, in the forests of the Far East, in Malaysia,

there's the loris.

Once again, it has those primate hallmarks -

the forward-facing eyes and the grasping hands.

This is a young one. It had a firm grip right from birth,

and it uses it, as nearly all lemur babies do,

to cling to its mother's fur.

The loris still uses scent to mark its territory,

and it has the typical moist nose of a lemur,

with which to read the marks in the trees.

Only one primitive primate has no such nose,

and it, too, lives in these oriental forests. The tarsier.

For it, the dominant sense is not smell, but sight.

Its huge eyes and snub nose, without a surround of moist skin,

are signs of things to come,

for these are the characteristics of the more advanced primates

that displaced the lemurs and their relations from most of the world -

the monkeys.

The most primitive of the true monkeys still surviving

live in the jungles of South America.

Marmosets move about not at night, but during the day.

At first glance, they don't look like monkeys,

but scurry around the treetops more like squirrels.

They use visual signals a great deal.

Each species carries its own badges of identification -

moustaches, bonnets and plumes,

or, like these common marmosets, long, white ear tufts.

Although they eat fruit and insects, most of their food consists of gum,

which they tap by gnawing notches in bark.

Their gum trees are important features of their territories

and must be protected at all costs.

And the marmosets do this by marking them with scented urine.

Each territory is occupied

by an adult male and female together their young,

some of which may be nearly full-grown.

They all travel together

and defend the boundaries against neighbouring families.

Sometimes shrieking will scare off trespassers.

HIGH-PITCHED SQUEAKS

And, if that fails, they back up their threat

with a truly spectacular genital display.

To marmosets, this is the ultimate threat,

and the trespassing family nearly always withdraws.

So, through the evolution of a language of signals,

damaging fights are more often than not avoided.

Like lemur babies,

young marmosets have got a firm and determined grasp,

and they cling to their parents right from birth.

Often it's the male who carries them,

but again, like the lemurs,

the youngsters tend to move around a good deal, from one adult to another,

and even onto the backs of their older brothers and sisters.

And a particularly patient and long-suffering one

will accumulate a heavy load.

The grasping hands, so good at clinging to fur and branches,

are also excellent combs.

The nimble fingers are used for picking parasites

and loose skin from the fur of others.

Marmosets are the smallest of the monkeys

and, in many ways, they represent a link

between lemurs and other monkeys like these.

The squirrel monkey, also a South American,

is a typical member of the monkey family.

Active during the day,

relying more on its eyes and ears than its nose

for finding its way about and for communicating with its fellows.

Lively, gymnastic and totally at home in the trees.

There are about 70 different species of monkey in South America alone.

None of them is better adapted to life in the trees

than these howlers.

They sleep in the treetops

with a confident disregard for height and the risk of falling,

and they usually wait for the sun to get well up

before they bother to stir.

THEY GRUNT

Then they begin to demonstrate why they get their name.

HOARSE HOWLING

THE HOWLING GETS LOUDER

The howlers and that most tree-loving of lemurs, the indri,

have both discovered that the most efficient way

to lay claim to a large area of the treetops is to sing.

The howlers have taken the technique to extremes -

Their chorus is said to be the loudest noise made by any mammal.

With a favourable wind, you can hear them five kilometres away.

These are the biggest and heaviest monkeys in South America,

20 times the weight of a marmoset.

There seems to be a tendency among primates,

as in most mammals, to become larger and larger.

This may be because when males dispute over females,

the biggest one, from sheer strength,

is likely to win and so will father bigger babies.

But an increase in size, when you live in trees, has one drawback -

it becomes increasingly difficult to reach the outer branches

to gather fruit and leaves or to move from one tree to another.

The howlers have a way of reducing the problem,

an additional climbing aid of marvellous effectiveness,

a grasping tail.

They need to be very agile, for they are total vegetarians,

and the best fruit and leaves

are always at the farthest end of the branches.

Like all monkeys, their sense of smell is relatively dull.

So, to tell whether a fruit is ripe or not,

they have to hold it very close to the nose and give it a good sniff.

Some, though, are less fussy than others.

A howler selects fruit not only by smell, like a lemur,

but by its colour.

That is something that no lemur can do.

Most of them are virtually colour-blind.

But all the monkeys scampering about in the sunshine

have very good colour vision indeed.

And that has allowed them to use colour in their body language.

In fact, monkeys are the most vividly colourful of all mammals.

The monkeys' exploitation of colour is a worldwide characteristic.

But, from other points of view, there are considerable differences

between those species that live in South America

and those that live in the rest of the world.

Here in Africa,

the monkeys also developed into a multitude of different kinds.

But, for some reason that we don't really understand,

many species came down from the trees

and were almost as happy on the ground as they were in the branches.

Like, for example, these vervets.

This readiness to leave the trees may be something to do with the fact

that, for some reason, no African monkeys

have managed to develop that South American innovation,

the grasping tail.

So they never became so extremely adapted to a tree-living life,

or so thoroughly at home there. At any rate, the mere fact

that there are monkeys foraging over this grassland

is enough to tell you that this is an African scene.

There are lots of grasslands in South America,

but there are no monkeys wandering over them, like these.

There's even one kind of African monkey

that instead of always seeking safety in trees when danger threatens,

on occasion does just the reverse.

BABOONS CHATTER AND HOWL

These are baboons.

The physical talents that their ancestors developed in the trees

are still very useful on the ground.

The young baboon still clings to its mother's fur,

and as it gets older, rides on her back like a jockey.

Their grasping hands can pick up, pull up and dig up most things.

And baboons have developed a taste for a wide variety of food.

Not only the standard and typical monkey diet of fruit and leaves,

but roots and insects, and red meat,

in the form of lizards and small rodents,

and even other monkeys, if they can catch them.

Male baboons have grown big and powerful

in order to defend themselves and their troop.

But down on the ground there is also danger.

The big males keep order with visual signals.

BABOONS CALL AND GRUNT

The eyebrow flash is usually quite sufficient as a threat.

Though, every now and then,

it has to be backed up with a more obvious show of strength.

BABOONS SHRIEK AND CHATTER

Several other species of monkey, as well as the baboon,

have become very efficient at living on the ground.

One has even left Africa and emigrated to Europe.

The Rock of Gibraltar has been the home of troops of macaque monkeys

for about 2,000 years.

It's true that, in recent times, the British army

has imported fresh stock from North Africa when numbers got low,

and it seems likely that the very first ones here

were brought over from Africa as pets by Roman soldiers.

It says a lot for these monkeys that they've managed to survive.

Indeed, the macaque is one of the most resourceful

and adaptable of all monkeys.

In one form or another, it lives all over Asia,

from Afghanistan and India to Ceylon and Java,

and even as far north as Japan.

Up here, in the Japanese Alps, winters can be very severe indeed,

and the Japanese macaque has developed

a particularly dense and warm fur.

None of them hibernate, so they need to gather food every day.

And, at times like this, they have no alternative

but to burrow through the snow in search of it.

One population, however, has discovered

a most remarkable way of keeping themselves warm.

These are volcanic springs.

The monkeys moved into this area for the first time only a few years ago.

And one group of them quickly discovered you could get some relief

from blizzards and the worst of the cold

by sitting all day in a hot bath.

Unfortunately, though, there's no food to be found here,

so they have to come out sometimes,

and then it must be horribly chilly.

Macaques live in many parts of Japan.

And one population of them has become famous all over the world

for their inventiveness.

These live on a tiny offshore island called Koshima.

They're an isolated troop,

and they've made some remarkable changes in their behaviour.

For a long time people used to think that

the way in which creatures like these feed is largely instinctive.

But then, in 1952, scientists came to this island,

and in order to entice the monkeys out into the open

so that they could observe them more closely,

they started offering them...

THE MACAQUE SHRIEKS

..sweet potatoes.

Sweet potatoes, like that.

After about a year, a young female called Imo

began to take her roots down to a pool

and wash off the sand and mud before eating them.

Within a few weeks, friends and family, including her mother,

were copying her.

The habit spread and, ten years later,

almost all the monkeys on the island habitually wash their sweet potatoes.

Then a new variation arose.

Instead of using fresh water,

the monkeys took the roots down to the sea and washed them there,

even when they were clean already.

Perhaps they simply liked salt on their potatoes.

Only the very old didn't adopt the new customs.

The young were quick to learn.

And the fact that babies travelled on their mothers' back,

meant that they saw exactly what she was doing at all times,

an unexpected benefit of having grasping hands.

Then the scientists changed the diet to unhusked rice.

They wanted to keep the monkeys in one place

so that they could observe them

and they reckoned it would take them a long time

to pick out the rice from the sand,

but they'd reckoned without Imo.

She grabbed handfuls of rice and sand together

and threw the whole lot into the water.

The sand sank, the rice floated, and she quickly skimmed it off.

And, once again, the habit spread.

This ability and, indeed, readiness

to copy and learn from your contemporaries and your elders

results in the community having shared skills, shared knowledge,

shared ways of doing things, having, in fact, a shared culture.

The word, of course, is normally used for human societies,

but there's no reason, in principle,

why it shouldn't be applied to monkeys as well.

And what this troop of monkeys have done is to develop a simple culture.

Walking on your hind legs

is still very much a gymnastic trick for these creatures.

Monkeys are essentially four-footed animals.

There is one group of the primates that is, by and large, two-legged.

And, to see how they arose,

we have to go back to the tropical rainforests of the Old World.

Here, in the treetops of the jungles of the Far East,

monkeys developed that specialised in eating leaves and blossoms,

just like the howlers of South America.

The silver leaf monkey is one of them.

It's particularly unusual in that it's one of the few primates

whose young are totally different in colour from their parents.

This is just about the biggest totally tree-living monkey in Asia,

and it's still a considerable gymnast.

But some primates here have grown even bigger.

These heavyweights didn't solve their climbing problems

with a grasping tail.

Instead of running along the top of branches,

they took to swinging beneath them by their arms,

and they lost their tails altogether.

These are the apes.

The big ape of Borneo is the orang-utan.

Its toes have just as powerful a grip as its fingers.

In fact, you might, with justice, call it four-handed.

They're too big to jump about

and seldom let go with more than two limbs at a time.

They move across space by using their weight

and making a tree or vine sway in the direction that they want to go.

The males sometimes grow so enormous

that the thinner branches won't hold them at all.

They have to get from one tree to another

by descending and shambling across the ground.

Increase in size may have been the stimulus

to develop a swinging way of getting around.

But, having developed it, one ape, the gibbon,

exploited the new technique to its limit

by becoming smaller again.

The gibbon's arms are greatly lengthened and so are its fingers,

so that its hands have become hooks

that can be quickly latched onto a branch and off again.

With such limbs,

the gibbons have become the most exuberant and daring of acrobats

to be found anywhere.

THE GIBBONS WHOOP AND CRY

Such spectacular performances do, however, have risks.

Untested branches can break,

and, in fact, a third of all gibbon skeletons that have been examined

show signs of fractures.

There's one ape, however, that spends nearly all its time on the ground.

It lives here, 10,000 feet up,

on the flanks of the volcanoes of Central Africa

on the borders of Rwanda and Zaire.

It's the biggest of all the apes, the shyest, one of the rarest

and, until recently, one of the least-known.

The gorilla.

The group of gorillas that lives here

has been studied by scientists for several years

and has become sufficiently accustomed to human beings

to allow you to approach quite close.

But you have to behave properly,

and you mustn't conceal yourself too well.

If you appeared close to them and took them by surprise,

then they would almost certainly charge.

DEEP GRUNTING

There's a lookout sitting on that tree, and he's already seen me.

THE GORILLA GRUNTS

WHISPERING: There is more meaning and mutual understanding

in exchanging a glance with a gorilla...

..than any other animal I know.

We're so similar.

Their sight, their hearing, their sense of smell

are so similar to ours

that we see the world in the same way as they do.

They live in the same sort of social groups,

largely permanent family relationships.

They walk around on the ground as we do, though they're...

HOLLOW THUDS

..immensely more powerful than we are.

And so, if there were a possibility of...

..escaping the human condition and living imaginatively...

HE GROWLS SOFTLY

..in another creature's world...

..it must be with the gorilla.

And yet, as I sit here, surrounded by this...

trusting gorilla family...

They're gentle...placid creatures.

The boss of the group is that silverback male.

The rest are adult females with their young sons and daughters.

And this is how they spend most of their time,

lounging on the ground, grooming one another.

The male is an enormously powerful creature,

but he only uses his strength...

when he is actually protecting his own family

from a marauding male from another group.

And it's very, very rare

that there is any violence within the group.

So it seems really very unfair

that man should have chosen the gorilla

to symbolise all that is aggressive and violent

when that's the one thing the gorilla is not, and that we are.

That grasping, manipulative hand has now become something more,

an instrument with which to explore and investigate.

The fingers can delicately revolve a small object

and investigate it from every angle.

They can feel not only its shape, but its texture,

for the fingers, since they're no longer required

to be put flat on the ground in support of the body,

have sensitive pads at the end,

covered with tiny ridges of skin to enhance the sense of touch.

Every gorilla, in fact,

has its own unique fingerprints, just as we have.

The gorilla family spends its day gently grazing,

and there's plenty of time for play.

Half-grown blackback males regularly have wrestling matches.

Sometimes they even allow others to join in.

Though they may play games,

you don't forget that these are the rulers of the forest,

and the great silverback is king of the whole group.

He's so enormously strong that he need fear nothing

except a man armed with a spear or a gun.

No enemies and an unlimited supply of food

that can be gathered by stretching out an arm,

the gorilla has no need to remain particularly agile

in either body or mind.

APES MAKE ALARM CALLS

There is one other ape living in these forests.

Whereas a gorilla lives on, perhaps,

a couple of dozen different kinds of plants,

this ape eats the leaves of over 200.

And it not only eats leaves, it eats bark, blossoms, fruit,

and, as well as that, termites and ants and honey,

birds' eggs, birds, and even the flesh of small mammals.

And in order to do that,

you need a very nimble mind, an inquisitive disposition,

and that is exactly what these chimpanzees have got.

Chimps spend a considerable amount of time on the ground,

but they've not become so adapted to it as the gorilla.

The gorilla's foot has lost much of its grasp.

A chimp's is still almost as dexterous as its hand.

They're still small enough to go up into the trees

to gather fruit and leaves,

and they also spend the night up there, where it's safer.

Every evening, they make a bed for themselves -

a springy platform constructed by bending over the ends of branches.

They live in large groups, sometimes up to 50 strong.

And they need to recognise one another as individuals.

Lemurs do this by making distinctive scent marks.

Chimps, with less sensitive noses, do it by sight.

So, like us, they have very different and immediately recognisable faces.

The most abiding relationships within the group

are between mother and young.

A baby will remain clinging to its mother, or close by her,

for at least five years.

So the wisdom and experience of the community, its culture,

is passed on this way from one generation to another.

The skills of motherhood, for example,

are learned by a daughter watching her mother handling a new baby.

So if a young female chimp is taken into captivity

and deprived of that experience,

she will not know how to suckle her own babe and has to be shown.

Friendships are made and relationships sustained

throughout the group by grooming.

What started as a simple act of toilet

has now become the most potent form of social bonding within the group.

Every individual seems to enjoy it enormously.

An adult returning to the group after having strayed away for some days

is greeted with an ecstatic bout of grooming by friends.

Grooming like this has been a crucial influence

in the development of chimp behaviour.

It starts when the newly-born babe is cleaned by its mother.

For several years, the warm body of the mother

represents comfort and security.

And, as he becomes more independent, he runs back to her for that comfort

when things go wrong or he's frightened.

He still gets a similar pleasure when he's full-grown

with these long sessions of grooming,

that may go on for a couple of hours at a time.

A junior group member of the group will present himself for grooming

as an act of submission.

A dominant individual will accept it as a tribute.

Their agile fingers have allowed chimps

to make one further and highly important development.

This youngster is collecting one of his favourite foods, tree termites,

winkling them out of a hole with a stick

that he's specially cut and trimmed for the purpose.

It's a simple tool.

So chimpanzees live rich and varied lives.

They're members of a complex social group

with all the excitements that involves.

THEY CRY OUT

They have the most extensive vocabulary of sounds of any animal,

apart from man.

They make tools, and they have an unquenchable curiosity,

testing everything to find out how it moves, how it bends,

what it feels like, above all, what it tastes like.

This ability, indeed willingness,

to experiment with different kinds of foods

means that chimpanzees can not only live in forests like these,

but can venture out into more open country, into savannahs.

And once there, they can find not only leaves, but meat.

That move into open country was first made about 15 million years ago

by another primate, one of the very early ones.

It found, when it got there, that the very talents

that it had developed in the forest for moving around in the trees

were very useful out on the plains.

The stereoscopic eyes, which enabled it to see game in the far distance,

the manipulative hands,

which enabled it to use not just tools, but weapons.

In fact, it became a hunter,

and that early primate was man's ancestor.

Chimps are rather conservative cousins,

removed by about 15 million years.

Nonetheless, we both share many characteristics

in our bodies and behaviour,

that are the common inheritance from the ancient creatures

that once spent all their lives in the trees.

Subtitles by Red Bee Media Ltd