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00:00To be continued...
00:30To be continued...
01:00To be continued...
01:29The message is quite explicit and precise.
01:33It's saying, follow me.
01:34And it's just flown off, so why don't we do just that and see what happens?
01:38The bird, here in Kenya, is a honey guide, and my companion has summoned it with a special call.
01:46Man and bird have a mutual understanding which began in prehistory and which still today enables them to speak to one another.
01:58The bird flies ahead, alights on a conspicuous perch, and then waits for us to catch up.
02:07We don't know how far it'll take us.
02:12It may be a mile or so.
02:13Now the bird has stopped its chatter, and for the first time is perching low down.
02:25A buzzing is coming from the rocks within a few yards of it.
02:27Well, there's certainly some bees coming out of there, so with any luck there's some honey inside,
02:36and if we can get it out, then we'll be able to complete our share of the bargain with that bird.
02:41African bees have got very effective stings, so it's sensible to stupefy them a bit with smoke before you attempt to steal their honey.
02:57The bird sits quietly by, waiting for us to do the part of the job that it can't manage.
03:11It's delicious.
03:19If the bird hadn't shown us where this bee's nest was, I'd have never got this sweet reward.
03:27But then, if we hadn't broken open the bee's nest, the bird would never have been able to get at the honey.
03:33So this is the result of a message sent by a bird to a man.
03:38And since it is a partnership, it's only fair that the bird should get a reward.
03:44So it's the custom in these parts not to take all the honey, but to leave some of it for the bird.
03:54So two different species solve the trial of talking to strangers.
03:59You have to get your message through, and not only to friends, but to enemies.
04:08As the wild dogs start hunting, the gazelles don't simply run away.
04:27They make these extraordinary leaps.
04:30They stop.
04:30This action is a message, which says, in effect,
04:44my jumps show that I am strong and could probably outrun you.
04:49Someone else would be an easier catch.
04:51As the dogs rush across the plain, they choose which gazelle to go for on the basis of this information.
05:07These messages are truthful, for the frequency of a gazelle's leaps do indicate its strength.
05:36And the dogs hardly ever select those that stot with vigour.
05:52Interestingly, the gazelles rarely stot when pursued by a cheetah,
05:56for the cheetah selects its prey before the chase begins and catches it with a sprint.
06:01There's no time for messages.
06:02But with dogs, it's different.
06:09Dogs are not sprinters.
06:11They're long-distance runners, and they catch their victims by tiring them out.
06:15A gazelle's message is inevitably honest.
06:23A weak individual can't counterfeit strength.
06:26But animals don't always tell the truth to one another.
06:29This bird, for example, tells downright lies.
06:32It's a ringed plover, and it makes its nest on the shingle of European beaches.
06:41Its eggs are perfectly camouflaged.
06:44The bird itself, when sitting on them, is much more obvious than they would be.
06:48So when danger threatens, the logical course is clear.
06:59A possible predator, like me, is unlikely to find the eggs, and much more likely to follow the bird.
07:05And the bird has a way of persuading me to do so.
07:08It's saying, in effect, I'm injured, I've got a broken wing.
07:15If you're looking for an easy meal, why not pick me up?
07:18But, of course, it's not true.
07:33It's just a device to lure me away from its eggs.
07:38Suddenly, its broken wing gets better.
07:42And since I'm now so far away from its nest that I'm no longer likely to blunder into its eggs,
07:47back it goes.
07:48Whether honest or dishonest, communication often demands a great deal from the sender.
07:59A skylark sings for hours high in the sky to proclaim the ownership of the territory beneath.
08:04This not only uses up energy, but also risks the attention of one of their main predators, the merlin.
08:11Amazingly, even while they're being chased, many larks continue to sing.
08:24The meaning of this song is the same as the stot of the gazelles.
08:33And the evidence for that, in 80% of these encounters, merlins either ignore or quickly stop chasing birds that continue to sing.
08:57The ones they pursue are nearly always the silent ones.
09:01The skylark's song, like that of most birds that live on the grasslands, is high-pitched and very complex.
09:20Because 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.
09:30Here in Israel, for example, there's an animal that spends its entire life underground.
09:37Mole hills like these are normally the only sign one has of its presence.
09:42It's totally blind, it can hardly smell, and has a very poor sense of hearing.
09:46And yet individuals, 40 or 50 yards apart, can communicate with one another through the solid earth.
09:55This is a geophone.
09:58Basically, it's just a device which turns vibrations in the ground into sound which I can hear and record on this.
10:05And with it, maybe I can have an underground conversation.
10:09That's my message.
10:17And there's a reply.
10:22The animal's not hearing sound, it's just responding to vibrations in the ground.
10:30I'm talking to a mole rat.
10:34This hairy mole rat, very different from the naked mole rat of Africa, sends messages by beating the roof of the tunnel with its head,
10:42and receives them by pressing its jaw against the tunnel wall and feeling the vibration.
10:48They burrow continuously, and their tunnels extend for hundreds of yards, winding circuitously and often crossing above and below those of others as they search for roots and tubers.
10:59But outside the breeding season, they're very antisocial, and they do all they can to avoid meeting a rival coming the other way.
11:16So they constantly send signals saying where they are, and listen out for messages from others.
11:22They exchange challenges. Who will give way?
11:38If they're both so confident of themselves that they ignore these warnings, and the two tunnels actually meet, then there is always a fight.
12:07Unless one retires and surrenders its tunnel, this can only end in the death of one of them.
12:24Soil is not the only medium that can be used to carry messages.
12:28By shaking their bodies, lacewings send vibrations down stems and leaves.
12:37Special equipment converts these into sounds which we can hear, and different species use characteristic frequencies and rhythms.
12:45Lacewings are tiny, and their quiverings travel just a couple of inches, so they're only detectable at close quarters.
13:10But they reassure males and females that they're suitable mates.
13:19Even the surface of ponds carry messages.
13:22A male water strider creates ripples with its front legs.
13:26This lily pad is his territory, and his rippled message will travel up to a yard.
13:35A stranger.
13:47It, too, creates ripples, which means that it's a rival, for females don't communicate in this way.
13:53To send messages further still, you have to make vibrations in the air, sound.
14:00This palm cockatoo deliberately breaks off branches to use as drumsticks, and beats out his claims for this nest hole.
14:11And he backs up his messages with ear-splitting calls.
14:24The sound travels best when the air is cool and still, at dawn.
14:38And the songs that penetrate farthest through the foliage of the forest are not complex like the skylarks, but simple.
14:45The bellbird's call can be heard three miles away.
15:00The aptly named Screaming Pihar produces a call almost as ear-splitting.
15:19With a call like that, you don't need bright feathers to impress a mate.
15:23And the Pihar is not only drabbly dressed, but sends its piercing messages from inconspicuous perches in the undergrowth.
15:32Up to eight males will sit in a small patch of forest, trying to out-scream one another in a competition to attract a passing female.
15:44When male and female birds do eventually pair in the forest, they may need to keep in touch with one another.
15:50And some do that by singing duets.
15:56The African ground hornbill.
16:08Duetting like this is obviously useful in Lidic vegetation,
16:11but the birds may do it wherever they are, so strengthening the bond between them.
16:15Cores in the forest also serve to keep animals apart.
16:28This is Madagascar.
16:30The Indri, the largest of lemurs, they live in families, a male, a female with her baby, and often a half-grown youngster.
16:57The female is the lead singer.
17:04The group's message proclaims its ownership of a territory and of the food it contains.
17:15Neighbours, when they hear it, defiantly respond with their own claims, so soon the forest is ringing with the calls of many groups.
17:27The chorus is a marvellous one, but each call in structure is simple.
17:49The Malaysian forest, at dawn, awakes to a much more complex song.
18:04These calls are a well-structured and intricate duet.
18:07They're made by the black gibbon, the Siaman.
18:10The male starts, his voice amplified by a resonating throat pouch.
18:29The female joins in.
18:38The male screams.
18:40The female barks again.
18:42And for the finale, the whole family crashes about in the branches.
18:48Singing together like this serves to bind a pair in a partnership that lasts a lifetime.
19:00But it's primarily a way of declaring ownership and ensures that gibbon families are well spread out,
19:06each knowing the whereabouts and identity of its neighbours, and so avoiding unnecessary territorial squabbles.
19:17Other calls that cleverly establish who is who and who is where can be heard on the banks of the Tana River in Kenya.
19:25A mangabi.
19:32Unlike the Indri and the Siamang, these monkeys don't defend a permanent territory.
19:39Instead, they're constantly searching for an unpredictable food supply.
19:48Having found it, they lay claim to it with a two-part call.
19:52The first section, a hoop, means simply listen.
20:01The second part, a kind of gobble, is a statement of who they are.
20:06On hearing it, the males take up listening positions.
20:11The gobble part of the call is slightly different for each group,
20:15so the males know exactly who is around.
20:22There are two ways of responding to this threat.
20:27If food is short, everyone rushes out to defend it with a display of aggressive yawns.
20:35But if there's plenty for everyone, they just ignore it.
20:38The most complex of all monkey communications so far analysed, however,
20:47can be heard on the shores of Lake Naivasha in Kenya's Rift Valley.
20:51At dawn, vervet monkeys come down from the trees to search for food on the ground.
21:07Down here, of course, they're much more vulnerable than they were up in the trees.
21:23But there's always a sentinel on watch.
21:25The sentinel gives a call which means snake.
21:39The meaning is very precise, and is only made when a snake appears.
21:53It could be called a word, and when other vervets hear it,
21:56they know exactly what the danger is.
22:03Calls with such specific meanings are very rare in the animal world,
22:07but vervets have developed several of them.
22:11Apart from man, no other animal in the wild has been shown
22:15to use so many different word-like alarm calls.
22:28A call that means danger from the air.
22:31And the vervets run into the denser branches where the eagle won't pursue them
22:36for fear of damaging its wings.
22:45From the safety of the thorny branches, the vervets scream furiously.
22:50And one is even brave enough to launch a lightning attack.
22:53Monkeys are not the only ones to be fearful of the eagle.
23:02So are small birds, such as the superb starling.
23:05Vervets understand the starling's vocabulary.
23:16The bird shrieks a warning, shh, danger on the ground.
23:22And the monkeys repeat it using their own term, and everyone runs for it.
23:26So vervets, with such a wide vocabulary of alarm calls, show that sound can carry a great deal of vital information.
23:42A function that becomes even more important at night.
23:45With the coming of darkness, everybody seems to be using sound.
23:54And that can be a problem.
23:59In a Panama swamp, 50 different species of frog are starting to sing.
24:03In this tumult, it's very difficult to make yourself heard.
24:11But males of this species, starting on their serenades, carefully time their calls to fit in between those of their neighbours.
24:18To 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.
24:38Males of this species, however, deliberately jam one another.
24:56The female pays most attention to the second half of the call.
24:59So 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 neighbours.
25:17A male, frustrated in this way, will resort to violence.
25:22But the intruder goes on calling, even as they wrestle.
25:29So every evening, there is a continuous battle for the supremacy of the airwaves.
25:47Sound is not the only way of communicating at night.
26:01When the sun goes down here on the tidal rivers of Malaysia, the trees on the banks become alive with animals communicating with light.
26:09At first, there are just a few twinkles in the branches, but about three quarters of an hour after sunset, the show begins.
26:22These are fireflies.
26:24These are fireflies.
26:27Thousands and thousands of tiny bee shadows.
26:29When the sun will of course shine the earth in the candle's and calm that
26:51These are fireflies, thousands and thousands of tiny beetles, only about five millimetres long,
26:57each sending a message in Morse code with a lantern in its abaddon.
27:02All those that are flashing are males, and their message, of course, is directed to the females,
27:08and it's a very simple one, come hither, mate with me.
27:12And this particular species, as well as one or two others here in Southeast Asia,
27:17reinforce that message and make sure it's sent the farthest possible distance
27:22by all flashing in perfect time together, in perfect synchrony.
27:27And the result is that even after I've drifted many yards downriver,
27:31looking back, I can still see their tree outline or pulsing light.
27:47This display continues throughout the hours of darkness every night of the year,
27:55and extends for miles along the river.
27:58The combined light of all these tiny beetles is so bright
28:02that fishermen out at sea can use them as navigating beacons
28:06to guide them back to their home rivers.
28:09Only in Southeast Asia do fireflies coordinate their flashings in this spectacular way.
28:16Elsewhere in the world, fireflies operate independently,
28:20each beaming its own individual invitation to mate.
28:27Take a walk in the woodlands of the eastern United States at dusk in summer,
28:32and you can find fireflies all around you.
28:35And what's more, with these you can actually communicate,
28:39if you have a small torch like this.
28:42To communicate with the males, which are flying around about a foot above the ground,
28:49I have to accurately imitate the call of a female.
28:53In the species that's flashing now, the female observes the flash of the male,
28:58and then waits two seconds and produces a half-second flash of her own, like this.
29:04Let's see if I can do it.
29:10Ah, there's one.
29:15Flash, two, from me.
29:20One, two, flash.
29:22He's coming.
29:24Flash from him.
29:25One, two, flash from me.
29:27And here he comes.
29:28Here he comes.
29:29Here he comes.
29:31There we are.
29:32He's settled on my finger.
29:38Got him.
29:40There he is.
29:46Well, I'm afraid I'm a disappointment too.
29:48Communication with light is not restricted to the land.
29:56It's even more widely used in the sea.
30:02This bay in Bermuda, on a few nights each month,
30:05puts on a particularly dramatic light show.
30:08About an hour after sunset, strange lights appear in the water.
30:24They're produced by female fire worms.
30:27As each one spirals on the surface,
30:29she releases two substances from different glands,
30:32which, as they combine, generate this chemical light.
30:38Each is a sexual summons.
30:50The males, who have big eyes,
30:51respond by swimming swiftly towards them,
30:54emitting a chain of brief flashes.
31:08As a male arrives,
31:10she releases another cloud of light,
31:13and with it her eggs,
31:14which he then fertilizes.
31:19After ten minutes,
31:20the bay is thick with rising females.
31:28This mating fiesta can only occur on nights
31:31when the moon rises after it's already dark.
31:33Once it's high in the sky,
31:35its light on the water would overwhelm that of the worms.
31:38The males would no longer be able
31:40to discern their luminous invitations.
31:43After twenty minutes,
31:44the females sink back to the depths.
31:46The show is over.
31:48If you want to find the greatest number and variety of animals that communicate with light,
31:55you have to go to the darkest place on earth.
32:00Somewhere far beyond the reach of the sun's rays,
32:02where human beings hardly ever go,
32:03to the depths of the ocean.
32:05This is the Johnson Sea Link.
32:06At the front,
32:07it has an array of remotely controlled television cameras,
32:09and the cameras,
32:10and the cameras,
32:11and the cameras,
32:12and the cameras,
32:13and the cameras,
32:14and the cameras.
32:15If you want to find the greatest number and variety of animals
32:16that communicate with light,
32:17you have to go to the darkest place on earth.
32:18Somewhere far beyond the reach of the sun's rays,
32:20where human beings hardly ever go,
32:21to the depths of the ocean.
32:23This is the Johnson Sea Link.
32:26At the front,
32:27it has an array of remotely controlled television cameras and searchlights.
32:31I'm sitting beside the pilot,
32:33in the transparent bubble in the middle,
32:35and the whole craft is massively strengthened
32:38to withstand the huge pressures of the depths.
32:45As we go down,
32:46it gets darker and darker.
32:49The water is thick,
32:52with small floating organisms.
33:01At 600 feet,
33:02the water outside is 20 times atmospheric pressure.
33:07The temperature is within a few degrees of freezing,
33:10and we are far beyond the reach of the sunshine.
33:13So you might think,
33:14in such a hostile environment,
33:16there would be very few animals living.
33:18But watch this.
33:23The chorus of lights,
33:24is being made by hundreds of small deep sea creatures,
33:28which are flashing in response to my light.
33:37And now,
33:38if I turn on the lights of the submersible,
33:41we may catch a glimpse of one of these strange deep sea creatures,
33:45as it drifts by.
33:48The pilot has remote controls for the camera outside the sub,
33:51to search for them in the blackness.
33:58This is a comb jelly as big as a football.
34:01It's been nicknamed Big Red,
34:03but it has yet to be given a proper name.
34:06It's new to science.
34:10Another new, undescribed comb jelly.
34:12Although specimens have been brought to the surface,
34:14it's only been seen alive through the windows of deep sea craft like this.
34:19It uses a pair of long, retractable tentacles to catch fish.
34:30A jellyfish solo misses two feet across,
34:33which, in spite of the changes of pressure,
34:35sometimes swims quite close to the surface.
34:38Kiyomiya, another comb jelly,
34:47one that is surrounded by gauzy skirts.
34:56But for the most sensational spectacle,
34:58you have to turn the lights of the submarine off.
35:01A jellyfish,
35:07outlined by its own pulsing illuminations.
35:20A squid,
35:21its lights moving as its body throbs.
35:24Displays like this may serve for defence,
35:26or to send messages.
35:27No one knows.
35:34And most spectacular of all,
35:36another jellyfish,
35:37with its own amazing rhythmic flashing system.
35:53The Golden Gate Bridge, San Francisco.
35:55In one of the smaller bays that rim this superb harbour,
35:58the wealthier citizens have taken to living on boats.
36:04A few years ago,
36:05when the campaign to clear up San Francisco Bay
36:08was just beginning to have an effect,
36:10the people who lived here on these houseboats in Sausalito
36:14found that the quietness of their lifestyle
36:16was being interrupted by a strange and very irritating noise.
36:20What's more, it was inescapable.
36:23They could hear it, out here, over the water.
36:26But inside, it was even louder.
36:29Every night, throughout the summer, at around nine o'clock,
36:33this strange noise would reverberate through the houseboat,
36:37as it's doing now.
36:39And often, it went on all night, preventing people from sleeping.
36:42There were various theories about its cause.
36:46Some people suggested that it was the local sewage company
36:50secretly pumping effluent into the bay at night.
36:54Others tried to sue the electricity company,
36:57which had recently laid a cable across the bay.
37:00But finally, a marine biologist suggested that it came from an animal.
37:04And we can prove that he was right by playing back the sound
37:10through an underwater speaker.
37:21A toadfish, normally a shy, skulking creature.
37:24And not just one, several.
37:35They're all females, and they seem to find the sound irresistible.
37:44Sound travels far more easily through water than through air,
37:48and females are attracted to the speaker from considerable distances.
37:51And this is the fish that created the sound in the first place,
38:00the male toadfish.
38:02He does it by vibrating his swim bladder.
38:12He's guarding an old abalone shell within which he has young.
38:21The babies are of different sizes.
38:24There are several broods here.
38:26A succession of females have laid their eggs in his nest,
38:29each attracted, one after the other, by his song.
38:36And it's not only his song that brings them.
38:39He has spots along his flanks.
38:42Each one is a light,
38:43and he treats his females to a full show of sons and lumières.
38:54The undersea world is full of sound.
38:57Over 200 species of fish create simple sound messages
39:01that travel easily through the water.
39:02The sea lions, which evolved on land but spend so much of their time at sea,
39:17have developed ears that enable them to hear all these sounds
39:20much more clearly than we can.
39:21They haven't got special ways of making underwater sounds themselves,
39:37but on occasion they bark as they do on land.
39:41Tusked whales, narwhals, the unicorns of the sea.
39:47They joust on the surface.
39:49Underwater they produce a tumult of sound.
39:51The sea lions, the sea lions, the sea lions, the sea lions.
39:55They are the sea lions, the sea lions, the sea lions, the sea lions.
39:56Tusked whales, narwhals, the unicorns of the sea.
39:59Tusked whales, narwhals, the unicorns of the sea.
40:03They joust on the surface.
40:07Underwater they produce a tumult of sound.
40:10The female narwhal has no tusk, but like the male, she does have a huge bulge on her forehead.
40:35From this comes a stream of high-pitched clicks.
40:38These, by a form of echolocation, enable an narwhal to detect obstacles out of sight ahead
40:45and also, grouped together in pulses, may serve to identify individuals.
40:55But they also make a great variety of other sounds,
40:58groaning and squealing and blowing bubbles through their blowholes.
41:03Sound travels so well through water
41:05that the big whales, which can make immensely loud calls,
41:09can probably communicate over several hundred miles.
41:12But narwhals are by no means the most loquacious animals in the sea.
41:21These creatures can't communicate with sound, for they're totally deaf.
41:26But they nonetheless can send and receive such complex messages
41:30that they could be considered to be carrying on a conversation.
41:34And they do it entirely visually.
41:36They're squid.
41:38The variety and subtlety of their colour changes are so great
41:41that it's hardly possible for us to keep up with their conversational exchanges.
41:50They produce these changes of colour and pattern with tiny sacks of pigment,
41:54which can expand from an almost invisible speck to a large blotch and back again in the fraction of a second.
42:13And they're all under the control of a highly complex nervous system.
42:16It's not only colour changes that they use in their visual conversations,
42:26the position of the body also has significance.
42:29Researchers have so far discovered 35 different postures,
42:33which act, as it were, as adverbs,
42:35qualifying the intensity of the message sent by the colour change.
42:38This male reef squid appears to be saying nothing seen from this side.
42:46Its flank is a blank.
42:48But his other side is vivid with swift colour changes.
42:52He's chatting up the female beside him.
42:55Rival males passing by would never know what he's up to.
43:04The male at the back has developed a striped pattern.
43:06That's an invitation to mate.
43:09The female goes white.
43:11That's a refusal.
43:14And when another male tries to edge in,
43:17they exchange a whole series of swift messages.
43:20That is the beginning of an argument.
43:36The reef squid system of communication is certainly very complex,
43:53and we don't fully understand it.
43:55But there are other animals in these waters off the Bahamas
43:59that have a system that is even more complicated still.
44:02They're mammals, like ourselves.
44:05They seem positively to enjoy our company,
44:09and most ships have them riding on their bow waves
44:12at some time or other, apparently just for the fun of it.
44:15They're dolphins.
44:16This crystal clear patch of the ocean is the home of a group of 60 or so spotted dolphins.
44:29The sea is not very Office of the sea for the sea.
44:32It's a few weeks to miss their wings.
44:33Keep a bit of a sense of its nature to the sea.
44:35Friends have a great fun place.
44:36And the ocean is not very much to do with the sea.
44:39We are around the sea.
44:41It's a great place for the sea,
44:43and the sea is the most to the sea.
44:45It's a great way to embrace an air.
44:46We do about the sea,
44:49and the sea is to the sea.
44:51The sea lives are only a month.
44:53It's a great day for the sea.
44:54The sea is to the sea.
44:55The sea is on the sea.
44:56even though our ears are not well adapted to hearing underwater swimming
45:00with them I could catch something of their near continuous conversations
45:05they're full of curiosity they play with odd things they find such as twigs and
45:10swimming among them leaves you in no doubt that they are highly intelligent
45:26like narwhals and other whales they use ultrasonic clicks and they have a huge range of whistles
45:36over 30 different sounds have been identified each with a different meaning
45:41every dolphin has its own particular name whistle
45:53one will attract the attention of another by whistling this call sign just as we will shout
46:01to someone using his name
46:02baby dolphins have name whistles that are derived from their mothers inherited in fact rather like
46:14human surnames this baby is accompanied by a young female who's looking after it but now its mother
46:22returns and the baby whistles to her excitedly
46:32when they are close to one another they may rub fins just as we might shake hands
46:39most remarkable of all perhaps they combine both sound and visual signals in their communications
46:48they will often take up a particular position hanging vertically in the water or lying still on the bottom
46:54each posture gives each sound a different meaning so enormously increasing their vocabulary
47:01they enjoy mimicking as though agreeing with one another they will even mimic you as you spin or hang in the water
47:09so these animals can communicate in four different ways with sounds which we can hear with ultra sounds which we can't with body
47:14so these animals can communicate in four different ways with sounds which we can hear with ultra sounds which we can't with body postures which change the meaning of anyone's sounds and with touch
47:44the result is an amazingly complex web of communication unexcelled by any other animal except ourselves
47:51except ourselves but how marvelous it would be if we could become a part of that
47:57the
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