Original subtitles

(HE MAKES BIRD-LIKE CALL)

(BIRD RESP0NDS)

This bird is communicating directly with me.

What's more, the call is one it only uses when it's signalling to human beings,

and its message is quite explicit and precise.

It's saying, ''Follow me.'' It's just flown off, so why don't we do just that and see what happens?

The bird, here in Kenya, is a honey guide,

and my companion has summoned it with a special call.

Man and bird have a mutual understanding

which began in prehistory and which still today enables them to speak to one another.

The bird flies ahead, alights on a conspicuous perch and then waits for us to catch up.

We don't know how far it'll take us. It may be a mile or so.

Now the bird has stopped its chatter and for the first time is perching low down.

A buzzing is coming from the rocks within a few yards of it.

There are certainly some bees coming out,

so with any luck there's some honey inside, and if we can get it out,

then we will be able to complete our share of the bargain with that bird.

African bees have got very effective stings,

so it's sensible to stupefy them a bit with smoke before you attempt to steal their honey.

The bird sits quietly by,

waiting for us to do the part of the job that it can't manage.

Mmm!

It's delicious!

If the bird hadn't shown us where this bees' nest was,

I'd have never got this sweet reward.

But if we hadn't broken open the bees' nest, the bird would never have got at the honey.

So this is the result of a message sent by a bird to a man.

Since it is a partnership, it's only fair that the bird should get a reward.

So it's the custom in these parts not to take all the honey,

but to leave some of it for the bird.

So two different species solve the trial of talking to strangers.

You have to get your message through, and not only to friends but to enemies.

As the wild dogs start hunting, the gazelles don't simply run away.

They make these extraordinary leaps. They stot.

This action is a message which says, in effect,

''My jumps show that I am strong and could probably outrun you.

''Someone else would be an easier catch.''

As the dogs rush across the plain, they choose which gazelle to go for

on the basis of this information.

These messages are truthful,

for the frequency of a gazelle's leaps do indicate its strength.

And the dogs hardly ever select those that stot with vigour.

Interestingly, the gazelles rarely stot when pursued by a cheetah,

for the cheetah selects its prey before the chase begins and catches it with a sprint.

There's no time for messages.

But with dogs, it's different.

Dogs are not sprinters, they're long-distance runners,

and they catch their victims by tiring them out.

A gazelle's message is inevitably honest.

A weak individual can't counterfeit strength.

But animals don't always tell the truth.

This bird, for example, tells downright lies.

It's a ringed plover, and it makes its nest on the shingle of European beaches.

Its eggs are perfectly camouflaged.

The bird itself, when sitting on them, is much more obvious than they would be.

So when danger threatens, the logical course is clear.

A possible predator like me is unlikely to find the eggs

and much more likely to follow the bird, and the bird has a way of persuading me to do so.

(C0NSTANT CHIRPING)

It's saying, in effect, ''I'm injured. I've got a broken wing.

''If you're looking for an easy meal, why not pick me up?''

But, of course, it's not true.

It's just a device to lure me away from its eggs.

Suddenly, its broken wing gets better.

Since I'm now so far away from its nest that I'm no longer likely to blunder into its eggs,

back it goes.

Whether honest or dishonest, communication often demands a great deal from the sender.

A skylark sings for hours, high in the sky,

to proclaim ownership of the territory beneath.

This not only uses up energy,

but also risks the attention of one of their main predators - the merlin.

Amazingly, even while they're being chased, many larks continue to sing.

(SINGING)

The meaning of this song is the same as the stot of the gazelles.

''I'm fit. You won't catch me. Chase a weaker bird.''

And the evidence for that - in 80% of these encounters,

merlins either ignore or quickly stop chasing birds that continue to sing.

The ones they pursue are nearly always the silent ones.

The skylark's song, like that of most birds that live on grasslands,

is high-pitched and very complex

because that kind of song travels well over open country.

And obviously the way an animal communicates must be governed to a considerable degree

by the sort of place in which it lives.

Here in Israel, for example,

there's an animal that spends its entire life underground.

Molehills like these are normally the only sign one has of its presence.

It's totally blind, it can hardly smell, and it has very poor hearing,

and yet individuals 40 or 50 yards apart

can communicate with one another through the solid earth.

This is a geophone.

Basically, it's just a device which turns vibrations in the ground into sound

which I can hear and record on this.

With it, maybe I can have an underground conversation.

That's my message.

- (THUDDING) - And there's a reply.

The animal's not hearing sound, it's just responding to vibrations in the ground.

I'm talking to a mole rat.

This hairy mole rat, very different from the naked mole rat of Africa,

sends messages by beating the roof of the tunnel with its head

and receives them by pressing its jaw against the tunnel wall to feel the vibration.

They burrow continuously, and their tunnels extend for hundreds of yards,

winding circuitously and often crossing those of others,

as they search for roots and tubers.

But outside the breeding season they're very antisocial

and they do all they can to avoid meeting a rival coming the other way.

So they constantly send signals saying where they are

and listen out for messages from others.

They exchange challenges.

Who will give way?

If they're both so confident of themselves that they ignore these warnings

and the two tunnels actually meet, then there is always a fight.

Unless one retires and surrenders its tunnel, this can only end in the death of one of them.

Soil is not the only medium that can be used to carry messages.

By shaking their bodies, lacewings send vibrations down stems and leaves.

Special equipment converts these into sounds which we can hear

and different species use characteristic frequencies and rhythms.

(L0W VIBRATI0N)

(PR0L0NGED VIBRATI0N)

(RHYTHMIC VIBRATI0N)

Lacewings are tiny and their quiverings travel just a couple of inches,

so they're only detectable at close quarters,

but they reassure males and females that they are suitable mates.

Even the surfaces of ponds carry messages.

A male water strider creates ripples with its front legs.

This lily pad is his territory and his rippled message will travel up to a yard.

A stranger. It, too, creates ripples, which means that it's a rival,

for females don't communicate in this way.

To send messages further still, you have to make vibrations in the air. Sound.

This palm cockatoo deliberately breaks off branches to use as drumsticks

and beats out his claims for this nest hole.

And he backs up his messages with ear-splitting calls.

(SQUAWKS)

Sound travels best when the air is cool and still,

at dawn.

The songs that penetrate farthest through the foliage of the forest are not complex,

like the skylark's, but simple.

(SQUAWKS)

The bell bird's call can be heard three miles away.

(SQUAWKS)

(''W0LF WHISTLE'' CALL)

The aptly named screaming piha produces a call almost as ear-splitting.

With a call like that, you don't need bright feathers to impress a mate,

and the piha is not only drably dressed,

but sends its piercing messages from inconspicuous perches in the undergrowth.

Up to eight males will sit in a small patch of forest trying to outscream one another

in a competition to attract a passing female.

When male and female birds do eventually pair in the forest,

they may need to keep in touch with one another and some do that by singing duets.

(H00TING CALLS)

The African round hornbill.

Duetting like this is obviously useful in thick vegetation,

but the birds may do it wherever they are, so strengthening the bond between them.

Calls in the forest also serve to keep animals apart.

This is Madagascar.

(L0UD WH00PING CALL)

The indri, the largest of lemurs.

They live in families - a male, a female with her baby

and, often, a half-grown youngster.

The female is the lead singer.

The group's message proclaims its ownership of a territory and of the food it contains.

Neighbours, when they hear it, defiantly respond with their own claims,

so soon the forest is ringing with the calls of many groups.

(INCREASING DIN 0F CALLS)

The chorus is a marvellous one, but each call, in structure, is simple.

The Malaysian forest at dawn awakes to a much more complex song.

(DISTANT WH00PING)

These calls are a well-structured and intricate duet.

They're made by the black gibbon, the siamang.

The male starts, his voice amplified by a resonating throat pouch.

The female joins in.

The male screams

and the female barks again.

And, for the finale, the whole family crashes about in the branches.

Singing together like this serves to bind a pair in a partnership that lasts a lifetime,

but it's primarily a way of declaring ownership

and ensures that gibbon families are well spread out,

each knowing the whereabouts and identity of its neighbours

and so avoiding unnecessary territorial squabbles.

0ther calls that cleverly establish who is who and who is where

can be heard on the banks of the Tana river in Kenya.

A mangabey.

Unlike the indri and the siamang, these monkeys don't defend a permanent territory.

Instead, they are constantly searching for an unpredictable food supply.

Having found it, they lay claim to it with a two-part call.

The first section, a whoop, means simply, ''Listen.''

The second part, a kind of gobble, is a statement of who they are.

0n hearing it, the males take up listening positions.

The gobble part of the call is slightly different for each group,

so the males know exactly who is around.

There are two ways of responding to this threat.

If food is short, everyone rushes out to defend it

with a display of aggressive yawns.

But if there's plenty for everyone, they just ignore it.

The most complex of all monkey communications so far analysed, however,

can be heard on the shores of Lake Naivasha in Kenya's Rift Valley.

At dawn, vervet monkeys come down from the trees to search for food on the ground.

Down here, of course, they're much more vulnerable than in the trees,

but there's always a sentinel on watch.

The sentinel gives a call which means, ''Snake!''

(CLICKING N0ISE)

The meaning is very precise and is only made when a snake appears.

It could be called a word, and when other vervets hear it,

they know exactly what the danger is.

Calls with such specific meanings are very rare in the animal world,

but vervets have developed several of them.

Apart from man, no other animal in the wild

has been shown to use so many different word-like alarm calls.

A call that means, ''Danger from the air!''

The vervets run into the denser branches where the eagle won't go

for fear of damaging its wings.

From the safety of the thorny branches, the vervets scream furiously.

And one is even brave enough to launch a lightning attack.

Monkeys are not the only ones to fear eagles - so do small birds, such as the superb starling.

Vervets understand the starling's vocabulary.

The bird shrieks a warning, ''Danger on the ground!''

The monkeys repeat it using their own term, and everyone runs for it.

So vervets, with such a wide vocabulary of alarm calls,

show that sound can carry a great deal of vital information,

a function that becomes even more important at night.

With the coming of darkness, everybody seems to be using sound,

and that can be a problem.

In a Panama swamp, fifteen different species of frog are starting to sing.

In this tumult, it's very difficult to make yourself heard,

but males of this species, starting on their serenades, carefully time their calls

to fit in between those of their neighbours.

(''CRICK-CRICK'' S0UND )

To our ears, the calls may sound continuous,

but a female frog is able to select the male with the loudest call and will mate with him.

Males of this species, however, deliberately jam one another.

The female pays most attention to the second half of the call,

so if a rival starts up nearby, a male deliberately re-times his call

so that the first part exactly jams the second crucial part of his neighbour's.

(0VERLAPPING CALLS)

A male, frustrated in this way, will resort to violence,

but the intruder goes on calling, even as they wrestle.

So, every evening, there is a continuous battle for the supremacy of the airwaves.

Sound is not the only way of communicating at night.

When the sun goes down on the tidal rivers of Malaysia,

the trees on the banks become alive with animals communicating with light.

At first, there are just a few twinkles in the branches,

but about three quarters of an hour after sunset, the show begins.

These are fireflies, thousands and thousands of tiny beetles only about 5mm long,

each sending a message in Morse code with a lantern in its abdomen.

All those that are flashing are males,

and their message is directed to the females, and it's a simple one:

''Come hither, mate with me.''

This particular species, as well as one or two others here in South-East Asia,

reinforce that message and send it the farthest possible distance

by all flashing in perfect time together, in perfect synchrony.

The result is that, even after I've drifted many yards downriver,

looking back I can still see their tree outlined with pulsing light.

This display continues throughout the hours of darkness every night of the year

and extends for miles along the river.

The combined light of all these tiny beetles is so bright

that fishermen out at sea can use them as navigating beacons

to guide them back to their home rivers.

0nly in South-East Asia do fireflies coordinate their flashings in this spectacular way.

Elsewhere in the world, fireflies operate independently,

each beaming its own individual invitation to mate.

Walk in the woodlands of the eastern United States at dusk in summer,

and you can find fireflies all around you.

What's more, with these you can actually communicate,

if you have a small torch like this.

To communicate with the males, which are flying a foot above the ground,

I have to accurately imitate the call of a female.

In the species that's flashing now,

the female observes the flash of the male and then waits two seconds

and produces a half-second flash of her own like this.

Let's see if I can do it.

Ah! There's one!

Flash, two...for me.

0ne, two, flash. He's coming.

Flash from him, one, two, flash from me.

Here he comes. Here he comes!

There we are. He's settled on my finger.

Got him!

There he is.

Well, I'm afraid I'm a disappointment to you.

Communication with light is not restricted to the land.

It's even more widely used in the sea.

This bay in Bermuda, on a few nights each month,

puts on a particularly dramatic light show.

About an hour after sunset, strange lights appear in the water.

They're produced by female fireworms.

As each one spirals on the surface,

she releases two substances from different glands, which, as they combine,

generate this chemical light.

Each is a sexual summons.

The males, who have big eyes, respond by swimming swiftly towards them

emitting a chain of brief flashes.

As a male arrives, she releases another cloud of light

and, with it, her eggs, which he then fertilises.

After 10 minutes, the bay is thick with rising females.

This mating fiesta can only occur on nights when the moon rises

after it's already dark.

0nce it's high in the sky, its light on the water would overwhelm that of the worms.

The males would no longer be able to discern their luminous invitations.

After 20 minutes, the females sink back to the depths. The show is over.

If you want to find the greatest number and variety of animals

that communicate with light, you have to go to the darkest place on Earth,

somewhere far beyond the reach of the sun's rays,

where human beings hardly ever go - to the depths of the ocean.

This is the Johnson Sealink.

At the front is an array of remotely controlled television cameras and searchlights.

I'm sitting beside the pilot in the bubble in the middle,

and the whole craft is massively strengthened

to withstand the huge pressures of the depths.

As we go down, it gets darker and darker.

The water is thick with small floating organisms.

At 600 feet, the water outside is 20 times atmospheric pressure,

the temperature is within a few degrees of freezing

and we are far beyond the reach of the sunshine.

You might think in such a hostile environment

there would be very few animals living, but watch this.

The chorus of lights is being made by hundreds of small deep-sea creatures

which are flashing in response to my light.

And now, if I turn on the lights of the submersible,

we may catch a glimpse of one of these strange deep-sea creatures as it drifts by.

The pilot has remote controls for the camera outside the sub

to search for them in the blackness.

This is a comb jelly as big as a football.

It's been nicknamed ''Big Red'', but it has yet to be given a proper name.

It's new to science.

Another new, undescribed comb jelly.

Although specimens have been brought up,

it's only been seen alive through the windows of deep-sea craft like this.

It uses a pair of long retractable tentacles to catch fish.

A jellyfish, Solmissus, two feet across,

which, in spite of the changes of pressure, sometimes swims quite close to the surface.

Kiyohimea, another comb jelly,

one that is surrounded by gauzy skirts.

But for the most sensational spectacle, you have to turn the lights of the submarine off.

A jellyfish outlined by its own pulsing illuminations.

A squid, its lights moving as its body throbs.

Displays like this may serve for defence or to send messages.

No one knows.

And most spectacular of all,

another jellyfish with its own amazing rhythmic flashing system.

The Golden Gate Bridge, San Francisco.

In one of the smaller bays that rim this superb harbour,

the wealthier citizens have taken to living on boats.

A few years ago,

when the campaign to clear up San Francisco Bay was just beginning to have an effect,

the people who lived here on these houseboats in Sausalito found

that the quietness of their lifestyle was being interrupted

by a strange and very irritating noise.

What's more, it was inescapable. They could hear it out here over the water,

but inside it was even louder.

Every night, throughout the summer, at around nine o'clock,

this strange noise would reverberate through the houseboat as it's doing now.

0ften it went on all night, preventing people from sleeping.

There were various theories about its cause.

Some people suggested that it was the local sewage company

secretly pumping effluent into the bay at night.

0thers tried to sue the electricity company, which had recently laid a cable across the bay.

But, finally, a marine biologist suggested that it came from an animal.

And we can prove that he was right by playing back the sound

through an underwater speaker.

(EERIE HUM)

A toadfish. Normally a shy, skulking creature.

And not just one. Several.

They're all females and they seem to find the sound irresistible.

Sound travels far more easily through water than through air

and females are attracted to the speaker from considerable distances.

This is the fish that created the sound in the first place - the male toadfish.

He does it by vibrating his swim bladder.

(C0NTINU0US HUM)

He's guarding an old abalone shell within which he has young.

The babies are of different sizes. There are several broods here.

A succession of females have laid their eggs in his nest, each attracted,

one after the other, by his song.

And it's not only his song that brings them.

He has spots along his flanks.

Each one is a light

and he treats his females to a full show of ''son et lumi�re''.

The undersea world is full of sound.

0ver 200 species of fish create simple sound messages

that travel easily through the water.

Sea lions, which evolved on land but spend so much of their time at sea,

have developed ears that enable them to hear all these sounds much more clearly than we can.

They haven't got special ways of making underwater sounds themselves,

but, on occasion, they bark as they do on land.

(BARKING)

Tusked whales - narwhals, the unicorns of the sea.

They joust on the surface.

Underwater, they produce a tumult of sound.

(BLEEPS AND CRIES)

The female narwhal has no tusk, but, like the male,

she does have a huge bulge on her forehead.

From this comes a stream of high-pitched clicks.

These, by a form of echo location,

enable a narwhal to detect obstacles out of sight ahead

and also, grouped together in pulses, may serve to identify individuals.

But they also make a great variety of other sounds - groaning and squealing

and blowing bubbles through their blowholes.

Sound travels so well through water that the big whales, which can make immensely loud calls,

can probably communicate over several hundred miles.

But narwhals are by no means the most loquacious animals in the sea.

These creatures can't communicate with sound for they are totally deaf,

but they can send and receive such complex messages

that they could be considered to be carrying on a conversation.

And they do it entirely visually. They are squid.

The variety and subtlety of their colour changes are so great

that it's hardly possible for us to keep up with their conversational exchanges.

They produce these changes of colour and pattern with tiny sacs of pigment

which can expand from an almost invisible speck

to a large blotch and back again in a fraction of a second.

They're all under the control of a highly complex nervous system.

It's not only colour changes they use in their visual conversations -

the position of the body also has significance.

Researchers have so far discovered 35 different postures

which act, as it were, as adverbs,

qualifying the intensity of the message sent by the colour change.

This male reef squid appears to be saying nothing, seen from this side.

Its flank is a blank. But his other side is vivid with swift colour changes.

He's chatting up the female beside him.

Rival males passing by would never know what he's up to.

The male at the back has developed a striped pattern.

That's an invitation to mate.

The female goes white - that's a refusal.

When another male tries to edge in, they exchange a whole series of swift messages.

That is the beginning of an argument.

The reef squids' system of communication is certainly complex

and we don't fully understand it.

But there are other animals in these waters off the Bahamas

that have a system that is even more complicated still.

They're mammals like ourselves,

they seem positively to enjoy our company,

and most ships have them riding on their bow waves

apparently just for the fun of it.

They're dolphins.

This crystal-clear patch of the ocean

is the home of a group of 60 or so spotted dolphins.

Even though our ears are not well adapted to hearing underwater,

swimming with them I could catch something of their near-continuous conversations.

They're full of curiosity. They play with odd things they find, such as twigs.

Swimming among them leaves you in no doubt that they are highly intelligent.

(CLICKING)

Like narwhals and other whales, they use ultrasonic clicks.

And they have a huge range of whistles.

0ver 30 sounds have been identified, each with a different meaning.

Every dolphin has its own particular name whistle.

0ne will attract the attention of another by whistling this call sign

just as we will shout to someone using his name.

Baby dolphins have name whistles that are derived from their mother's -

inherited, in fact, rather like human surnames.

This baby is accompanied by a young female who is looking after it,

but now its mother returns and the baby whistles to her excitedly.

When they are close to one another, they may rub fins,

just as we might shake hands.

Most remarkable of all, perhaps,

they combine both sound and visual signals in their communications.

They will often take up a particular position,

hanging vertically in the water or lying still on the bottom.

Each posture gives each sound a different meaning,

so enormously increasing their vocabulary.

They enjoy mimicking, as though agreeing with one another.

They will even mimic you, as you spin or hang in the water.

So these animals can communicate in four different ways -

with sounds which we can hear,

with ultrasounds which we can't,

with body postures which change the meaning of any one sound, and with touch.

The result is an amazingly complex web of communication,

unexcelled by any other animal except ourselves.

But how marvellous it would be if we could become a part of that.