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00:00The End
00:30Oh, my God.
01:00Although all those creatures are so very different,
01:15they are, in fact, closely related to one another.
01:18They are all mammals.
01:20But how have they become so varied?
01:23And what is the ancestral form, the basic theme,
01:26on which they're all variations?
01:28Well, you can find a pretty close approximation to that theme
01:31in the jungles of Southeast Asia.
01:35It's properly called a tupia,
01:38and it's certainly a mammal with a hairy coat and warm blood.
01:42But what kind?
01:43It looks very like a squirrel.
01:45A close look at its anatomy reveals resemblances to a rabbit.
01:49But it doesn't gnaw nuts and it doesn't nibble grass.
01:52It catches insects.
01:56Its teeth are small, numerous and spiky like a shrew's.
02:00Indeed, its popular name is tree shrew.
02:03But its large brain and those grasping hands
02:05have suggested to some that it's related to monkeys.
02:08It seems, in fact, to contain hints of many different mammals.
02:12One thing, though, is clear.
02:15It's very like the earliest of mammals
02:18that were living when the dinosaurs dominated the Earth
02:21a hundred million years ago.
02:23The basic pattern on which there's been such a multitude of variations.
02:28And some of those variations are so extreme
02:31that it's difficult to believe that there's any connection
02:33between them and the basic theme,
02:36were it not for the evidence of fossils
02:38and the anatomy of the living animals.
02:43The tree shrew's continuous activity and swift reactions
02:47are typical of a mammal,
02:49a consequence of its ability to generate heat within its body
02:52so that its chemistry works fast
02:54and provides it with abundant energy.
02:57This talent probably developed a very long time ago indeed,
03:01at a time when the dinosaurs dominated the Earth.
03:04For fossils of a creature remarkably similar to the living tree shrew,
03:07have been found in rocks that are 200 million years old.
03:14Its numerous spiky teeth suggest that it ate insects
03:18and the shape of its limbs that it was a swift runner.
03:21In fact, its lifestyle was not unlike a tree shrew.
03:25And creatures like it survived alongside the dinosaurs
03:28throughout their reign,
03:30probably scampering about at night
03:32when the colder-blooded dinosaurs became torpid in the cold.
03:35Then, 65 million years ago,
03:39the dinosaurs disappeared.
03:42The forests and swamps of the world
03:44were suddenly empty of large creatures.
03:47Primitive birds flapped through the sky,
03:50but on the ground there were few creatures
03:52other than insects and other invertebrates
03:54and those small, warm-blooded, primitive mammals that fed on them.
03:58And here and there, in odd corners of the world,
04:01their descendants still survive little changed.
04:04The tree shrew of Malaysia is one,
04:06and here, in the streams of the Pyrenees,
04:09lives another, little-known and very engaging one.
04:12It's called a desmon.
04:22Like most of these primitive mammals,
04:25the desmon has a stupendous appetite.
04:28It eats about two-thirds of its own body weight every day
04:31and seems never to stop the hunt for more.
04:33It's nose does most of the searching.
04:55It scents the faintest changes
04:57in the taste of the water with its nostrils
04:59and feels its way around with all those whiskers.
05:18Its feet are a combination of web and claw
05:21for both swimming and clambering.
05:29Its eyes are tiny, minute beads
05:36hidden in its long fur.
05:42When at last it does find something good,
05:45it doesn't give up easily.
05:46Its snorkel nose allows it to snatch a breath
06:09with the minimum of interruption in the struggle.
06:11It's fun to talk to us soon.
06:24PIANO PLAYS
06:54It's hard-fought-for worm will now keep it going for another hour or so.
07:14Another of these primitive survivals lives along the streams of North America.
07:19It's not only an energetic swimmer, but a burrower as well.
07:27It's possible the swimming way of life and the body design to go with it
07:31led to a similar activity, not in water, but underground.
07:35Water paddles have become spades.
07:37This is the star-nosed mole.
07:46The odd fleshy flower on its nose is another highly sensitive smelling device
07:54and it may have yet another way of investigating its surroundings.
07:59Many of these little insect eaters, such as shrews,
08:02make squeaks so high-pitched that we can't hear them
08:05and the echo they produce help the animals to find their way around.
08:09Moles, like desmonds and shrews, have formidable appetites
08:23and have to eat every few hours.
08:26Their tunnels are not simply passageways, but traps.
08:29Worms and insects burrowing through the soil drop into them
08:33and the mole collects whatever turns up.
08:38If its appetite is momentarily sated,
08:41then it paralyzes a surplus worm with sharp bites
08:44and stores it away in a special larder
08:47before setting off again on its never-ending patrols.
08:51Variations on the theme of the small insect eater
09:07began to appear soon after the dinosaurs vanished.
09:10Creatures developed that specialised in feeding
09:12on one particular kind of insect, ants and termites.
09:17This is another digger, the aardvark, from Africa.
09:19And this is its South American equivalent, the giant anteater.
09:35The essential equipment for a diet of ants and termites, it seems,
09:39is an elongated snout for poking inside the nests
09:43and a long, sticky tongue for collecting the insects.
09:46And the giant anteater has the most extreme version of both that exists.
09:56Termites are easily crushed,
09:58so the anteater has no need of teeth and has lost them all.
10:02Termites' nests, however, can be as hard as cement
10:04and strong claws and muscular legs are needed to tear them open.
10:14The anteater is very fussy about its food.
10:17In spite of its name, it seldom eats ants.
10:20Termites, like these, are a much more usual meal.
10:23And even then, it prefers some termites to others.
10:26There are a dozen or so species of mammal around the world
10:42that have specialised in living on ants and termites.
10:45As a lifestyle, it doesn't seem to require
10:48a particularly quick intelligence or vivacious disposition.
10:51And all these anteaters are relatively slow-moving creatures.
10:56Because of that, and their total lack of teeth,
10:59they might seem to be easy meat for a hunter.
11:02But the giant anteater's front legs are so strong
11:05that its hug is lethal and few creatures interfere with it.
11:08The termite-eating specialist of Africa, the pangolin,
11:18is much smaller and not nearly such a powerful digger.
11:21It's developed a flexible armour of scales
11:23and can curl itself up into a ball
11:25so that it's virtually impregnable.
11:27Its muscular tail also acts as a counterbalance
11:30so that the creature can trundle along
11:32with most of its weight on its back legs
11:34and its front legs at the ready
11:36for digging into termite mounds like this one.
11:51It's so confident of its defences
11:54that it takes little notice of any other creature around
11:57unless they actually molest it.
12:00Smallest of all, the pygmy, silky-furred anteater of South America.
12:05It really does seem to be defenceless
12:07and certainly can't move fast enough
12:09to escape even the clumsiest hunter.
12:12But it keeps out of the way up in the branches,
12:14living almost entirely on tree ants.
12:18This one has a baby on its back
12:20and it may be either male or female
12:22for both parents take a share in carrying the load.
12:25ORCHESTRA PLAYS
12:29ORCHESTRA PLAYS
13:07There's yet another kind of specialist anteater in South America,
13:11intermediate between the giant and the pygmy, the tamandua.
13:27It feeds mostly at night.
13:29Its thick, bristly fur is supposed to protect the tamandua
13:33from the bites of the infuriated ants swarming from their shattered nest.
13:38But when you watch the animal feeding,
13:40you can't help wondering just how effective that protection really is.
13:45Ants and termites are certainly among the most numerous of insects,
13:49particularly in the tropics.
13:50And the tamandua and its relatives around the world
13:53have little difficulty in finding more than enough to eat.
13:55There are insects not only in water and in the soil and all other plants,
14:03but in the air, and particularly at night.
14:07And it's difficult to realise just how many there are
14:09until you put up a mercury vapour lamp in the tropics.
14:13And here, within a few minutes, we've got all sorts of creatures.
14:17Small moths, crickets, huge beetles, mantises, big moths,
14:21insects of all kinds.
14:25The insects first took to the air about 300 million years ago.
14:30And they had it themselves for about 100 million years,
14:34at least until the arrival of the reptiles.
14:36Whether there were any night-flying insect-hunting reptiles,
14:40we don't know, but it seems unlikely
14:42because reptiles being cold-blooded are usually active during the day.
14:46And then, about 150 million years ago, the birds developed.
14:52But there's no reason to suppose
14:53that there were any more night-flying birds in the past
14:57than there are today, and that's precious few.
15:00So this great feast of insects
15:03awaited any creature that could master the tricky technique
15:07of flying at night.
15:10And one group of the mammals did.
15:12The bats.
15:13The majority of them are hunters of flying insects
15:42such as moths, mosquitoes, or even beetles,
15:46caught on the wing and eaten at the roost
15:48as the bats hang upside down.
16:05Bats began to fly a very long time ago.
16:08These fossil bones of what is undoubtedly a bat
16:13are about 50 million years old.
16:15The bat skeleton is very similar to the tree shrews.
16:20Seen here from above, and now side on.
16:23But how did this flying variation arise?
16:27It may be that the early insect-eaters
16:29sought their food up in the branches of trees,
16:32as indeed some kinds of tree shrews do today.
16:35And as they leapt about,
16:37trying to snatch flying insects from the air,
16:40some may have developed flaps of skin
16:42between their arms and the sides of their body
16:45so that they could glide,
16:46as the living flying squirrels can today.
16:49They then supported those flaps with their fingers
16:52and strengthened the arm muscles
16:54until eventually they were able to flap
16:56their newly developed wings
16:58and fly in search of their insect prey,
17:01and so became bats.
17:05But living on insects has one great disadvantage.
17:14In many parts of the world,
17:16insects disappear almost totally during the winter.
17:19What does an insect-eater do then?
17:22It hibernates in any sheltered place it can find
17:25where there's a chance of the temperature
17:27remaining a few degrees or so higher than elsewhere,
17:30as it is inside this old Canadian mine.
17:44These tiny lumps, as cold as stone,
17:47are living bats.
17:48They fed voraciously during the summer,
17:51building up reserves of fat,
17:52but now a profound change has taken place in their bodies.
17:56Their heat has seeped away
17:58and their body processes have slowed down
18:00to almost, but not quite, a complete halt.
18:04They must keep their body chemistry ticking over
18:06just enough to generate sufficient heat
18:09to prevent them from freezing solid.
18:11For that, they can't survive.
18:15Not all of them are successful.
18:18Sometimes an individual cannot stave off the chill,
18:20falls and is entombed in the ice.
18:31You might think that they huddle together to keep warm,
18:34but careful measurements have shown
18:36that those hanging in groups
18:37get just as cold as those hanging by themselves.
18:40It may be that grouping protects them
18:42from another hazard,
18:43the loss of moisture during breathing,
18:45and that does seem to be less
18:47for those in clusters.
18:48Other creatures also take refuge in the mine,
18:53the very ones which in summer
18:55are food for the bats, moths.
18:58Both hunters and hunted shelter together
19:00from that overwhelming killer, cold.
19:05In other parts of the world,
19:07as here in New Mexico,
19:09bats solve the problem of lack of insect food
19:12by migrating.
19:13From this cave,
19:15they will fly south
19:16some 1,000 kilometers for the winter.
19:19They have to,
19:20to find enough food,
19:22for their populations
19:23are measured in millions
19:24and tons of insects are needed.
19:26Caves like these contain the densest populations
19:48of mammals to be found anywhere on Earth.
19:51How is it that all those bats
19:56flying at such a speed
19:57can find their way around in the dark?
20:01The answer is echolocation.
20:03Although I can only hear just the faintest twitter,
20:07in fact, each bat is emitting
20:10a more or less continuous stream
20:11of high-frequency sound
20:13beyond the range of my ears.
20:15But I can translate those
20:17into sounds that I can hear
20:18using a machine like this,
20:21a bat detector.
20:22Listen.
20:23Listen.
20:23The system is based on those high-pitched ultrasounds
20:44like those produced today by shrews
20:46and which the early insect eaters
20:48may have used as well.
20:50The bats have developed that ability
20:52into a highly sophisticated technique
20:54called sonar.
20:56Every bat sends out a stream of short squeaks,
20:59which can be as many as 20 or 30 a second
21:01or even more.
21:03From the echoes,
21:04it can gauge its distance from an object,
21:06whether it's a cave wall
21:07or an insect in the air.
21:12The horseshoe bat
21:13produces such ultrasounds from its nostrils,
21:16and that construction around the nose
21:18serves as a megaphone,
21:20focusing the sound into a beam.
21:22The easiest way to study these signals
21:25is to pick them up with a special microphone
21:27and relay them to an oscilloscope
21:30so that they can be analysed in a visual form.
21:36The oscilloscope tells us that the bat is producing sounds,
21:40though they are beyond the range of our hearing.
21:42But with the right equipment,
21:48we can translate those ultrasounds
21:50into sounds that we can hear.
22:00And with the oscilloscope as well,
22:02we can both see and hear
22:04the variations that the bat can make.
22:06Another way to analyse the bat's signals
22:23is to slow them down
22:24using a special tape recorder.
22:27These are the horseshoe bat's ultrasounds
22:29slowed down 32 times.
22:31This is a different species,
22:39also slowed down,
22:41and it's emitting the ultrasounds
22:43through its mouth.
22:44With these echolocating signals
22:46bouncing back off the prey,
22:49bats can home in very accurately,
22:51raising the rate of output as they approach.
22:53Both sound and action
23:00are slowed down 16 times.
23:06The bait, a mealworm,
23:08is located precisely by sonar,
23:10and the bat, a pipistrelle,
23:12catches it first with its wing membrane,
23:15then flicks it across to its tail membrane,
23:19which is then brought up to its head
23:20so that the mealworm is passed to the mouth.
23:24The tail membrane is still over the head.
23:29Now it's pulled back
23:30and the bat continues to eat its prey in flight.
23:35Since bats evolved to take advantage
23:37of the rich insect larder,
23:39the insects themselves
23:40have developed their own countermeasures.
23:43Watch.
23:43The lacewing's escape technique
23:51is to close its wings
23:52and fall out of the path of the bat.
23:54Lacewings have tiny ears on their wings,
24:16and so in this conflict between predator and prey,
24:19the insect has tuned in
24:21to be able to hear the bat coming
24:23and therefore take avoiding action.
24:25Some moths, including tiger moths,
24:33have an even more elaborate defence.
24:35Not only can they hear bats coming
24:37and then dive or spiral away,
24:39but as a last resort,
24:41they can emit their own sounds.
24:42First, we will see and hear the sound
24:45of the threatening bat.
24:48And then the reaction of the moth.
24:54The moth has either jammed the bat's signals
24:58or sent some kind of warning
25:00which puts the bat off.
25:01Anyway, the moth nearly always escapes.
25:10And we may assume
25:11that the battle of techniques
25:12will continue to evolve
25:14as bats further develop
25:15their sonar equipment.
25:17The apparatus often dominates
25:19the faces of bats.
25:21Huge ears for detecting the echoes
25:23and on the nose,
25:24leaves, flanges and spears
25:26for directing the sound
25:28so that they look as grotesque
25:30as any gargoyle produced
25:31by the medieval imagination.
25:42Some bats tackle insects much bigger
25:44than mosquitoes or lacewings.
25:46This one is quite prepared
25:47to alight on the forest floor
25:49and grapple with a giant cockroach.
25:56The insect-eating teeth
26:03inherited from the shoe-like ancestor
26:05are essential here
26:06to break up the tough chitin
26:08of the insect's body.
26:09When it hangs up,
26:36the wings form a kind of tent
26:38preventing bits of the prey
26:39from dropping out.
26:41This is a top view.
26:48And an even tougher adversary
26:50for the pallid bat,
26:52a scorpion.
26:53The poisonous sting
26:54is to be carefully avoided.
27:03And some bats are real carnivores.
27:08This huge silk cotton tree
27:14contains a small colony of them.
27:22They're hanging at the very top
27:24of the hollow interior,
27:26sharing the tree
27:26with other species of bats.
27:29This is strange
27:30because this carnivorous species
27:32feeds on other bats,
27:34but here it leaves
27:35its neighbours in peace.
27:36They also feed on birds,
27:45which they catch on their roosts
27:47at night.
27:49This is vampyrum spectrum,
27:52but it doesn't actually suck blood.
27:54This is not the true vampire.
27:57This is.
27:58Its teeth and mouth
27:59are very specialised
28:01for feeding on blood.
28:04Vampires may have originally
28:05fed on insects
28:06that cluster around
28:07grazing animals
28:08and chased them
28:09on or near the ground.
28:17By shaving away the skin
28:19with razor teeth
28:20and having a saliva
28:21that prevents oozing blood clotting,
28:23the vampire shows
28:25the vampire shows
28:25how extremely specialised
28:26a mammal can become
28:27and it probably all started
28:29with insects.
28:34And the originally insect-eating bat
28:36evolved in yet another direction
28:38in Arizona and Mexico.
28:40This is the land of big plants
28:44like cactus,
28:46yuckers
28:46and agaves.
28:48The agave flowers,
28:49branching from a mast
28:50some six metres high,
28:52attract hummingbirds
28:53that feed on the nectar.
28:56And insects too.
28:59It was probably these
29:00that attracted bats
29:01in the first place.
29:03Nectar feeding
29:03came later.
29:18The bats,
29:19in small parties,
29:21move from plant to plant,
29:23dipping and sipping
29:24at the energy-rich nectar.
29:27Often they get covered in pollen
29:29and in this way
29:30they ferry it
29:30from plant to plant,
29:32so bringing about
29:33cross-fertilisation.
29:34So both bat and plant
29:36have evolved together
29:37to become unlikely partners.
29:39As in other bats,
29:41this feeding specialisation
29:42involves adaptation.
29:45Long noses
29:45and long tongues
29:46enable them to reach
29:47deep into the flowers.
29:59When flying,
30:01seen here in slow motion,
30:02they emit a weak sonar,
30:05so they've been called
30:05whispering bats.
30:26Carrying pollen
30:27and dripping nectar,
30:29this bat will fly on to another agave
30:31where cross-fertilisation
30:33will occur.
30:42And when the bat
30:43has helped that to happen,
30:45the fruit will appear.
30:47And fruit too
30:48has become a food for bats.
30:50This one,
30:52lapping at a banana
30:53with its tongue,
30:54was the same kind
30:55as the one biting
30:55into a cockroach
30:56with its teeth,
30:58for some bats
30:58have developed broad tastes.
31:06Some, however,
31:07are exclusively fruit eaters,
31:09and they include
31:10the biggest of all.
31:11These hardly ever live in caves,
31:13but instead hang themselves
31:15up in great roosts
31:16and trees
31:16called camps.
31:17their wings are immense,
31:28up to two metres across.
31:30And just as birds
31:31have to groom their feathers
31:32with the greatest of care
31:34to keep themselves airworthy,
31:35so bats spend a lot of time
31:38meticulously cleaning
31:39the elastic membrane
31:40of skin
31:41on which they depend.
31:42fruit bats are often called
31:57flying foxes,
31:58and indeed their faces
31:59do look rather foxy.
32:01The fact that they have
32:02large eyes
32:03and none of those
32:04immense ears
32:05or grotesque ornaments
32:06on their noses
32:07is significant.
32:08They have no sonar
32:10and rely instead on vision
32:11to find their way around.
32:13In fact,
32:14they are so different
32:15from insect-eating bats
32:16that they may well
32:17be descended
32:18from a quite different branch
32:19of the primitive mammals.
32:33They're very powerful flyers
32:35and regularly go off
32:36on journeys of 50 kilometres
32:38just to find a tree in fruit.
32:41These are in slow motion.
32:42to sister with de graduated
32:45in toad
32:46and toad
33:03and toad
33:04The structure of a bat's wing is very different from that of a bird's.
33:28The bird's, in effect, is formed from just one finger fringed with feathers,
33:33all the other fingers have been effectively lost.
33:37But the bat's ancestors didn't have feathers with long, stiff quills,
33:41and they created a broad wing by a different method,
33:44by retaining all their fingers and greatly elongating them to support the wing membrane.
33:50Their feet also help, for the membrane goes right down to the ankle.
33:56Only the thumb remains free,
33:58and that the bat needs for its toilet and to hook onto branches as it clambers about.
34:09When, over 50 million years ago, the first mammals flew,
34:13they opened up great possibilities for their descendants.
34:16They had the night sky virtually to themselves,
34:19and they developed into a multitude of different forms to take full advantage of it.
34:24Today, there are nearly a thousand different species of them flying through the skies of the world.
34:30Many of them have remained insect feeders like their earthbound ancestors.
34:36But fruit, nectar, blood, birds, and even other bats,
34:42is by no means the complete list of the diets that they've discovered for themselves.
34:46And one of them has actually become a fisherman.
34:52It lives in Central America.
34:55Its closest relatives are all insect feeders,
34:58and it too will take a beetle like this one, though in a unique way.
35:03It caught that beetle by using its hind legs as grapnors,
35:09and it goes after fish in the same way.
35:12Watch.
35:18It hooked the fish, but not well enough.
35:29So back it comes.
35:33Like other bats, it immediately transfers its capture into its mouth,
35:47and only eats it when it gets back to its roost,
35:50stuffing some of it into cheek pouches.
35:53The membrane doesn't go right down to the ankle like most bats,
36:02so it's kept clear of the water,
36:04and the claws are as sharp as needles.
36:07But how does it know where to trawl?
36:09The answer's ultrasounds again.
36:11It's able to detect the ripple of a fish at the surface,
36:24and home in on it with deadly accuracy.
36:27It's a very rare and very recently acquired talent.
36:28The first really accomplished fisherman amongst the mammals
36:42appeared very early on in the history of the group.
36:45When the great ocean-going reptiles, the ichthyosaurs and the plesiosaurs,
36:46disappeared at the end of the age of the dinosaurs,
36:47the mammals were very quick indeed to fill the space that was left in the economy of the sea.
36:51At first, doubtless, the creature lived part of the time in the water and part of the time on land,
37:13rather as the hippopotamus does today.
37:16But very soon, within a few million years, truly specialised mammalian swimmers appeared.
37:23And some of them grew to be bigger even than the biggest of the dinosaurs, the whales.
37:28And here in the blue waters of the Pacific, off the Hawaiian Islands,
37:33every year humpback whales assemble to give birth and to court.
37:38And if you have a lot of patience and even more luck, you may be able to swim among them.
37:46I was lucky enough to dive with a group of whale experts who knew just how to get close to these magnificent creatures.
38:07And there, in the distance, a 40-ton mother and her baby.
38:26The changes that have taken place during the descent of these vast creatures from the little furry ancestors are obviously immense.
38:40But they're all adaptations to a seagoing life.
38:43The forelegs have become flippers and the back legs lost.
38:47But what about their huge increase in size?
38:50Well, the larger you are, the lower the ratio between your volume and your surface area,
38:55and the easier it is to retain heat.
38:57Dinosaurs also had problems about getting chilled and solved it in a similar way, by getting big.
39:04Their size, however, was limited by the strength of bone.
39:08Above a certain weight, leg bones would simply break.
39:11But whales are less hampered.
39:13Their bodies are not supported by legs, but by the water.
39:17So they have grown into the biggest animals that the world has seen.
39:21Some of them four times bigger than the largest known dinosaur.
39:25earth poser.
39:27Their population rign of civilization is not supported by the body.
39:30They have grown into the colony...
39:31Ontem approximately in their lives,
39:33a day in
42:29It also has a well-developed system for storing oxygen in the muscles.
42:35Some can swim for up to 40 minutes without drawing breath, if they want.
42:49Humpbacks are one of the group of whales
42:51that feed on shoals of shrimp-like creatures, krill.
42:55Sometimes they concentrate the krill
42:57with a ring of bubbles from the blowhole,
42:59and the mouthful is filtered through plates of whale bone
43:02hanging down from the upper jaw.
43:05In this way, they parallel the anteaters.
43:08Both creatures have modified their jaws and lost their teeth
43:11in order to collect swarms of tiny invertebrates.
43:17Another group of whales tackle much bigger prey.
43:20These whales have kept their teeth
43:22and become among the fiercest creatures in the sea.
43:25These are killer whales, and they're hunting seals.
43:35That dot is the head of a seal, desperately searching for safety.
43:40But it has no chance.
43:42That most dramatic and elusive creature, the narwhal, is another of the toothed whales,
44:01and one of its teeth has grown enormous.
44:03Only the males have this impressive tusk,
44:12but no-one yet has discovered just what it's for.
44:15The most familiar toothed whales of all are the dolphins and porpoises.
44:25They're not only the friendliest, but also the smallest,
44:28and they were among the first whales to be kept in tanks.
44:31And as a result, we've been able to watch the moment
44:34that must be among the trickiest of a sea mammal's life,
44:37the moment of birth.
44:39This is the mother-to-be.
44:41Her belly is swollen and birth is imminent.
44:44The baby's tail is just showing.
44:48Now it's half out.
44:50And there is the puff of red blood as the umbilical cord breaks
44:57and the youngster swims free.
44:59Here is that remarkable moment again.
45:09The baby can swim immediately,
45:10but the mother helps it up to the surface to take its first breath of air.
45:14Now it swims alongside her, gliding just as fast as she does,
45:19seemingly without any difficulty.
45:21Soon, as it swims,
45:23it will suckle at that other mammalian device,
45:26the nipple on its mother's underside,
45:28to take its first meal of milk.
45:30The dolphins' gymnastic skills,
45:31their ability to copy from one another,
45:32and their apparent eagerness to learn new tricks from their trainers,
45:33have made them the most accomplished and popular performers in Ocean Area.
45:35But how intelligent are they?
45:36the dolphins'
45:38The dolphins' gymnastic skills,
45:51their ability to copy from one another,
45:52and their apparent eagerness to learn new tricks from their trainers,
45:55have made them the most accomplished and popular performers in Ocean Area.
45:58But how intelligent are they?
46:08Speculations about dolphin intelligence have been stimulated in particular by these calls.
46:14Some people have even suggested that dolphins have a true language
46:18and that if only we were clever enough, we would not only be able to understand dolphins
46:22but might be able to speak it and convey quite complex messages to dolphins.
46:27Well, it's perfectly true that dolphins not only make sounds when they have their heads above water
46:33but do so almost continuously below water.
46:36And we can listen to them do it with an underwater microphone.
46:47Over 20 different kinds of calls have been identified.
46:50Some serve to keep a school together when they're travelling at top speed.
46:54And they can swim at 20 miles an hour and they go on long migrations.
46:58Some sounds are warning cries.
47:00Some call signs that enable one animal to be recognised at a distance by another.
47:06Complex though these calls are, no one has yet demonstrated that dolphins ever put calls together
47:12to form the equivalent of a two-word sentence.
47:16And that can be regarded as the beginning of a true language.
47:22But those aren't the only sounds that they make.
47:24They also use sound for echolocation in rather the same way that bats do.
47:30That's to say, they emit a series of very high-pitched clicks and squeaks.
47:35And by sensing the echoes, they can detect the presence of objects in the water around them.
47:41The frequencies they use are around 200,000 vibrations per second,
47:46which is about the same as that used by bats and way, way above the range of the human ear.
47:52But by once again using the bat detector, this time connected to the underwater microphone,
47:59we can translate those clicks into sounds that we can hear.
48:04Normally, of course, the dolphins use their eyesight in conjunction with their echolocation.
48:09But just to show how accurate that echolocation can be, we're going to blindfold the dolphins.
48:15The dolphin has been trained to retrieve this hoop.
48:26And what's more, it can find it in the water and distinguish it from these two shapes blindfold.
48:33Watch.
48:45And just to show that that's no fluke, let's try it again.
48:56The waters around Hawaii are also filled with strange sounds, but these we know far less about.
49:10A moment ago we made this recording with an underwater microphone here in the Pacific near Hawaii.
49:21Just listen to this.
49:40This is the sound of a humpback whale that's lying in the water about a hundred feet below us in the sea.
49:52There are many extraordinary things about its song.
49:56To start with, they're so long.
49:58They may last anything from a quarter of an hour to half an hour.
50:02And although the various themes within the song may be repeated a varying number of times,
50:08the actual themes themselves and the order in which they appear in the song is unbearable.
50:14And even more remarkable, all the singing whales within this area sing the same song.
50:25At the end of the breeding season they disperse and next year they will come back.
50:29But next year they will have a slightly different song which contains themes that have never been heard before.
50:36And all of them will be singing the same song.
50:40And that song can be heard echoing throughout these waters for miles and miles and miles.
50:47It seems extraordinary that a creature like this could have given rise to whales as well as to moles and bats and anteaters.
51:01But those swimming, burrowing, flying specialists appeared within a few million years of the disappearance of the dinosaurs.
51:08And the only mammals around from which they could have sprung were these small furry insect eaters.
51:15And so this tiny theme has proved to be one of the most fruitful in the animal kingdom.
51:21And there are still some variations that we haven't looked at yet.
51:24The vegetarians, the leaf and grass eaters and the carnivores that developed to prey on them.
51:29They will have to have a program of their own.
51:32They will have to have a program of their own.
52:02They will have to have a program of their own.
52:32They will have to have a program of their own.
52:39They will have to have a program of their own.
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