0:00:28 > 0:00:29Antarctica.
0:00:29 > 0:00:33The earth's coldest continent,
0:00:33 > 0:00:36the one that is most hostile to life.
0:00:43 > 0:00:46Here, 800 miles from the South Pole,
0:00:46 > 0:00:49it's 40 degrees below zero.
0:00:53 > 0:00:56Of all the millions of species of animals on Earth,
0:00:56 > 0:01:00only one can live here permanently.
0:01:09 > 0:01:11A Weddell seal.
0:01:15 > 0:01:20She can survive because she can dive below the ice.
0:01:24 > 0:01:27Here she is protected from the storms above,
0:01:27 > 0:01:29and here too, she can find food.
0:01:49 > 0:01:54But she is a mammal, and she has to breathe air,
0:01:54 > 0:01:58so she has to keep a lifeline open to the world above the ice.
0:02:00 > 0:02:02Not only for her,
0:02:02 > 0:02:05but now for her newborn pup.
0:02:05 > 0:02:06SEAL GRUNTS
0:02:06 > 0:02:07PUP CRIES
0:02:09 > 0:02:12He's less than a week old, and still very vulnerable.
0:02:24 > 0:02:28A blizzard blows in, and with it, storm-force winds.
0:02:28 > 0:02:30It could last for a week.
0:02:40 > 0:02:45Being mammals, seals can generate heat within their bodies.
0:02:45 > 0:02:49And their fur, with a thick layer of fat beneath it,
0:02:49 > 0:02:51prevents most of that heat from escaping,
0:02:51 > 0:02:54even in cold conditions like this.
0:02:59 > 0:03:03What is more, she is able to feed her youngster
0:03:03 > 0:03:07with that mammalian speciality, milk.
0:03:07 > 0:03:11And while she does so, she shields him from the worst of the blizzard.
0:03:37 > 0:03:41She has worked hard throughout the winter to prevent her breathing hole
0:03:41 > 0:03:43in the ice from freezing over.
0:03:54 > 0:03:56That requires constant attention -
0:03:56 > 0:03:59filing back the edges of the hole with her teeth.
0:04:07 > 0:04:11Her pup needs to join her under the ice as soon as he can swim properly.
0:04:15 > 0:04:18She encourages him to take his first plunge, but,
0:04:18 > 0:04:21hardly surprisingly, he is not keen.
0:04:43 > 0:04:48Now, guided by his mother, he has to learn how to hunt underwater,
0:04:48 > 0:04:52and to find his way back through the maze to his hole in the ice.
0:05:08 > 0:05:14A warm body, fur, milk and maternal care are essential
0:05:14 > 0:05:18for the Weddell seal's survival in this freezing environment.
0:05:20 > 0:05:24And those qualities have helped the mammals
0:05:24 > 0:05:27to colonise the entire globe.
0:05:36 > 0:05:38Equatorial East Africa.
0:05:40 > 0:05:44It's hard to image a place more different from Antarctica.
0:05:46 > 0:05:51To survive here, mammals need additional talents.
0:05:53 > 0:05:57This tree shelters the territory of a tiny mammal
0:05:57 > 0:06:01that spends its whole life in frenzied activity.
0:06:03 > 0:06:06It used to be called an elephant shrew,
0:06:06 > 0:06:09but now it's called by its African name of sengi.
0:06:16 > 0:06:20This is a female rufous sengi.
0:06:22 > 0:06:26And, like all sengis, she's so active, she's permanently hungry.
0:06:29 > 0:06:31To get all the food she needs,
0:06:31 > 0:06:34she has to be both industrious and ingenious.
0:06:41 > 0:06:44She has made an intricate network of trails
0:06:44 > 0:06:49that enable her to hunt her insect prey very efficiently.
0:06:50 > 0:06:54But these pathways have another important function
0:06:54 > 0:06:56when she meets her enemies.
0:07:28 > 0:07:32Having a map of these trails in her head can mean the difference
0:07:32 > 0:07:33between life...
0:07:36 > 0:07:37..and death.
0:07:42 > 0:07:45Like most mammals, and unlike reptiles,
0:07:45 > 0:07:48her legs are directly beneath her body.
0:07:49 > 0:07:53That makes her less stable, but much faster and more agile.
0:08:12 > 0:08:17Not only has she outrun this reptile, she's outwitted him.
0:08:23 > 0:08:24And just as well,
0:08:24 > 0:08:28for she is a mother and has a youngster to care for.
0:08:37 > 0:08:41The sengi relies on speed and cunning for its success.
0:08:41 > 0:08:44Other mammals have very different techniques.
0:08:49 > 0:08:53ANIMALS CALL OUT
0:08:53 > 0:08:54Here in Madagascar,
0:08:54 > 0:08:59one of the most bizarre of all mammals is on the prowl.
0:09:07 > 0:09:10The aye-aye, like the sengi, lives on insects.
0:09:11 > 0:09:15But the ones that she seeks, she can't see,
0:09:15 > 0:09:18for they're buried deep inside branches.
0:09:18 > 0:09:20They're beetle grubs.
0:09:23 > 0:09:27To find them, she has a special talent.
0:09:27 > 0:09:31She taps her fingers on the wood up to eight times a second,
0:09:31 > 0:09:33and listens for the tiny change in resonance
0:09:33 > 0:09:37that indicates a hollow spot within.
0:09:37 > 0:09:41Her hearing is so acute, she can identify the precise position
0:09:41 > 0:09:45in which to gnaw a hole in order to reach the grub.
0:09:47 > 0:09:51And she has a grotesquely long middle finger
0:09:51 > 0:09:52with which to skewer it.
0:10:04 > 0:10:10It takes a young aye-aye four years to perfect this technique.
0:10:10 > 0:10:12But once it has done so,
0:10:12 > 0:10:15it can collect prey that no other mammal can reach.
0:10:35 > 0:10:37The Arctic tundra.
0:10:37 > 0:10:40Food is hard to find here too.
0:10:40 > 0:10:43Indeed, this land is so barren that few large animals can live here.
0:10:47 > 0:10:50Yet one mammal has found a way to do so.
0:11:02 > 0:11:03It's late spring,
0:11:03 > 0:11:07and as the mounting strength of the sun warms the land,
0:11:07 > 0:11:10eight million reindeer move north.
0:11:22 > 0:11:24But the vegetation is so meagre
0:11:24 > 0:11:26that the only way the herds can get enough
0:11:26 > 0:11:29is to keep constantly on the move.
0:11:36 > 0:11:38Newborn calves soon discover
0:11:38 > 0:11:42that they will have to spend every day walking in search of food.
0:11:45 > 0:11:47They have extraordinary endurance.
0:11:47 > 0:11:50Some of these animals, before they die,
0:11:50 > 0:11:52will have trekked for a distance
0:11:52 > 0:11:55equivalent to three times around the earth.
0:11:59 > 0:12:02Grazing is now at its best.
0:12:02 > 0:12:06But this also the time when the reindeer' worst enemy appears...
0:12:07 > 0:12:09BUZZING
0:12:09 > 0:12:10Biting flies.
0:12:13 > 0:12:15The flies not only drive them to distraction,
0:12:15 > 0:12:19but they can drain a pint of blood each day.
0:12:29 > 0:12:33But the reindeer have a defensive strategy.
0:12:39 > 0:12:43Each individual tries to push its way into the centre of a group
0:12:43 > 0:12:44where there are fewer flies.
0:13:01 > 0:13:03With all this pushing and jostling,
0:13:03 > 0:13:06mothers need to keep their calves close.
0:13:13 > 0:13:16Sometimes the flies become so bad
0:13:16 > 0:13:18the reindeer can stand them no longer
0:13:18 > 0:13:22and they bolt to higher ground where the flies can't follow.
0:14:18 > 0:14:21But the price of escape can be high.
0:14:24 > 0:14:27In the rush, one mother has lost her calf.
0:14:29 > 0:14:31REINDEER CALLS OUT
0:14:51 > 0:14:54Others have already found it.
0:14:55 > 0:14:57BIRDS CALL OUT
0:15:09 > 0:15:11The herd has long since moved on,
0:15:11 > 0:15:14but her maternal instinct is so strong
0:15:14 > 0:15:18she'll stay to search for her missing calf for days.
0:15:21 > 0:15:25The reindeer are free from flies for now,
0:15:25 > 0:15:29but with no food on these high slopes,
0:15:29 > 0:15:32they will eventually be forced to descend to find new pastures
0:15:32 > 0:15:36and face the biting swarms once more.
0:15:39 > 0:15:44No animal makes a longer migration across the lands of the earth
0:15:44 > 0:15:45than these mammals.
0:15:53 > 0:15:57Other mammals have found a more economic way
0:15:57 > 0:16:01of travelling huge distances and at greater speed.
0:16:01 > 0:16:03They go by air.
0:16:08 > 0:16:10BIRDS CHIRP
0:16:32 > 0:16:34Giant straw-coloured fruit bats
0:16:34 > 0:16:37inhabit the great forests of the Congo.
0:16:42 > 0:16:45Their wings are nearly a metre across.
0:16:51 > 0:16:53In late October every year,
0:16:53 > 0:16:56they set off on a long journey across the forest canopy.
0:17:02 > 0:17:04Flocks of hundreds become thousands.
0:17:12 > 0:17:16And tens of thousands become hundreds of thousands.
0:17:20 > 0:17:22They are fast and powerful fliers
0:17:22 > 0:17:26and can travel a thousand miles in just a few nights.
0:17:26 > 0:17:28THUNDER RUMBLES
0:17:34 > 0:17:38How they know where and when to travel is a mystery,
0:17:38 > 0:17:44but they all end up in one place - Kasanka, a remote swamp in Zambia.
0:17:52 > 0:17:55There are ten million of them here.
0:18:09 > 0:18:12They crowd together in just one small patch of forest,
0:18:12 > 0:18:16no bigger than two or three football pitches.
0:18:16 > 0:18:19And here they take up residence for a few weeks.
0:18:19 > 0:18:22It's the largest fruit bat roost on Earth.
0:18:36 > 0:18:41After their long journey, they need to rest and relax.
0:18:50 > 0:18:54The roost is so crowded that complete strangers rub shoulders,
0:18:54 > 0:18:56and even snuggle up together.
0:19:00 > 0:19:02As evening approaches,
0:19:02 > 0:19:05they prepare to reap the reward for their long journey.
0:19:19 > 0:19:22They've come from all over Central Africa to this one place,
0:19:22 > 0:19:24because here,
0:19:24 > 0:19:25at this time of the year,
0:19:25 > 0:19:29there is an extraordinary glut of mangoes and other fruit.
0:19:31 > 0:19:35Streaming out from the roost, they set off to collect it.
0:20:06 > 0:20:11Each bat guzzles at least two kilos' worth of fruit every night.
0:20:15 > 0:20:17In just a few weeks, this mega-roost
0:20:17 > 0:20:21will devour more than a billion separate fruits.
0:20:23 > 0:20:27It's only the power of flight that allows these mammals
0:20:27 > 0:20:32to travel so far and so fast that they can reap such a brief harvest.
0:20:34 > 0:20:39After six weeks, the trees have been stripped of their fruit.
0:20:39 > 0:20:44Then, once again, the immense aerial armada takes to the air,
0:20:44 > 0:20:48each bat returning to its own particular patch
0:20:48 > 0:20:50of the vast Congo forests.
0:21:30 > 0:21:32The land mammals of Africa
0:21:32 > 0:21:35also travel together in stupendous numbers.
0:21:38 > 0:21:41The herds that graze the East African plains
0:21:41 > 0:21:44are not nearly the size they were a century ago,
0:21:44 > 0:21:46but they are still immense.
0:21:49 > 0:21:53Grazing together is a good defence.
0:21:53 > 0:21:54There's safety in numbers.
0:21:55 > 0:21:59But hunting together also brings advantages.
0:21:59 > 0:22:01LION SNARLS
0:22:06 > 0:22:11This hyena, however, is searching for food on her own.
0:22:13 > 0:22:16She needs to be careful.
0:22:22 > 0:22:24But she smells food.
0:22:25 > 0:22:28And she takes risks.
0:22:34 > 0:22:36HYENA YOWLS
0:22:50 > 0:22:52HYENA SHRIEKS
0:23:33 > 0:23:37Bruised and bloodied, she is lucky to have survived her mistake.
0:23:42 > 0:23:44But she's not totally defeated -
0:23:44 > 0:23:47she belongs to a clan.
0:23:47 > 0:23:50A call to arms rings out through the night.
0:23:50 > 0:23:54HYENA CALLS OUT
0:23:59 > 0:24:01Reinforcements assemble.
0:24:07 > 0:24:09Every adult in the clan responds.
0:24:17 > 0:24:22If a clan attack together, they have a chance of challenging the lions.
0:24:22 > 0:24:24HYENAS CALL OUT
0:24:30 > 0:24:32LION SNARLS
0:24:38 > 0:24:42It's a clan against a pride, each at full strength.
0:24:45 > 0:24:49And the clan outnumbers the pride.
0:25:25 > 0:25:27The combined power of the hyenas
0:25:27 > 0:25:30eventually forces the lions to retreat.
0:25:32 > 0:25:34Attacking as a coherent team
0:25:34 > 0:25:38requires a high degree of social cooperation,
0:25:38 > 0:25:42and that is another of the mammals' specialities.
0:25:53 > 0:25:56Social bonds between mammals begin
0:25:56 > 0:25:59when mothers feed their young on milk.
0:26:00 > 0:26:04And few look after their young with greater care
0:26:04 > 0:26:07than the mammal which dominates this landscape.
0:26:11 > 0:26:15A female polar bear is trying to find food for her cubs.
0:26:17 > 0:26:18But this is a particularly
0:26:18 > 0:26:20difficult time of the year.
0:26:22 > 0:26:27The sea ice on which she hunts is melting beneath her feet.
0:26:27 > 0:26:30She must look for food on land.
0:27:05 > 0:27:10They're all safely ashore, but they could still face months of hunger.
0:27:10 > 0:27:16Finding food is not so easy on this cold and barren coast.
0:27:16 > 0:27:20The search may be a long one.
0:27:26 > 0:27:30Polar bears have an extraordinarily sensitive sense of smell.
0:27:30 > 0:27:35And she has caught a faint whiff of something promising.
0:27:47 > 0:27:51It's the immense carcass of a bowhead whale.
0:27:54 > 0:27:59A whale carcass could provide more than any one family could eat.
0:28:01 > 0:28:04But they're not the first here to find it...
0:28:04 > 0:28:07by any means.
0:28:12 > 0:28:15The smell has brought in bears from miles away.
0:28:15 > 0:28:17ROARING
0:28:20 > 0:28:23Bear families seldom get on with one another.
0:28:33 > 0:28:37She's taking a risk bringing her cubs here.
0:28:41 > 0:28:45Male bears can, and do, kill and eat small cubs.
0:28:50 > 0:28:51ROARING
0:28:51 > 0:28:53Another family challenges her.
0:29:01 > 0:29:07She must decide whether to compete for food, or run away and go hungry.
0:29:16 > 0:29:20She keeps her cubs close to her and stands her ground.
0:29:33 > 0:29:38Their mother's courage has won the cubs a meal.
0:30:04 > 0:30:07Living as a family may bring rewards,
0:30:07 > 0:30:12but it can also create problems, for siblings can also become rivals.
0:30:15 > 0:30:19A coati - a South American relative of the racoon.
0:30:24 > 0:30:28These babies were born in a nest high in a tree,
0:30:28 > 0:30:31and are about to come down to the ground for the first time.
0:30:37 > 0:30:40Some more reluctantly than others.
0:30:59 > 0:31:04Once on the ground, the mother coati rounds her babies up
0:31:04 > 0:31:07and takes them away to join a single large group.
0:31:11 > 0:31:16Together, these families form a gang up to 40 strong.
0:31:22 > 0:31:25Once again, numbers bring safety.
0:31:25 > 0:31:28The first to spot danger will warn everyone.
0:31:42 > 0:31:44But keeping order isn't easy,
0:31:44 > 0:31:47and when they find food, it's a free-for-all.
0:32:05 > 0:32:07Meerkats in the Kalahari Desert
0:32:07 > 0:32:11also live in large groups, but they are rather more organised.
0:32:34 > 0:32:37Each family band is controlled by a queen,
0:32:37 > 0:32:40who is nearly always the only female to breed.
0:32:43 > 0:32:47She has been kept very busy suckling her five pups,
0:32:47 > 0:32:51and it's high time they became more independent.
0:32:53 > 0:32:59Today is the new brood's first trip to get breakfast for themselves.
0:33:09 > 0:33:13It takes weeks for youngsters to learn how to find food.
0:33:17 > 0:33:19MEERKAT SQUEAKS
0:33:19 > 0:33:21This one is trying to catch ants,
0:33:21 > 0:33:26but hasn't quite grasped the necessary technique.
0:33:31 > 0:33:36But this youngster has persuaded an adult to show him what to do.
0:33:37 > 0:33:41The tutor is not his parent, just an enthusiastic instructor,
0:33:41 > 0:33:46and one who will adapt his lessons to the ability of his student.
0:33:48 > 0:33:50This new one is a beginner,
0:33:50 > 0:33:55so he starts with something easy - how to dig for insect larvae.
0:34:08 > 0:34:12Other meals, like this one, are much trickier.
0:34:12 > 0:34:16So the tutor disables the scorpion's sting
0:34:16 > 0:34:18before he lets the youngster tackle it.
0:34:36 > 0:34:39The family also cooperates in defence.
0:34:40 > 0:34:46Every member does a tour of guard duty, keeping an eye out for danger.
0:34:46 > 0:34:48So, while one watches,
0:34:48 > 0:34:51everyone else can rest.
0:34:57 > 0:35:02And, on warm days, one can easily nod off.
0:35:30 > 0:35:33The secret of meerkats' success
0:35:33 > 0:35:36is that everyone takes a turn in communal duties.
0:35:56 > 0:36:00But many mammals do more than just share their workload.
0:36:00 > 0:36:07Some can share their knowledge, and do so across several generations.
0:36:08 > 0:36:12Elephant survival depends on profiting
0:36:12 > 0:36:15from the experience of many lifetimes.
0:36:18 > 0:36:21This baby elephant was born last night,
0:36:21 > 0:36:25and the whole herd seems to welcome this new addition.
0:36:28 > 0:36:31But the mother is young and inexperienced.
0:36:31 > 0:36:33This is her first baby.
0:36:53 > 0:36:56If she is to produce milk, a mother must drink.
0:36:56 > 0:36:59And the newborn calf must keep up with her
0:36:59 > 0:37:03as the herd continues on their long journey to find water.
0:37:06 > 0:37:10After five miles, the calf is flagging.
0:37:14 > 0:37:16Enough is enough.
0:37:25 > 0:37:28The young mother encourages her calf to continue,
0:37:28 > 0:37:30but there is still a long way to go,
0:37:30 > 0:37:33and the calf is already getting dehydrated.
0:38:01 > 0:38:05The elephants are now so close to water that they can smell it.
0:38:31 > 0:38:32Water, at last.
0:38:34 > 0:38:36ELEPHANT TRUMPETS
0:38:55 > 0:38:58This is the calf's first encounter with a waterhole.
0:39:00 > 0:39:04She's not sure what to make of it or, indeed, how to get out of it.
0:39:12 > 0:39:14Her mother tries to help her,
0:39:14 > 0:39:17but she has no experience of dealing with babies.
0:39:18 > 0:39:20BABY ELEPHANT CRIES OUT
0:39:26 > 0:39:31As the herd moves deeper into the swamp, the calf follows,
0:39:31 > 0:39:33but now she is in real trouble.
0:39:38 > 0:39:40BABY ELEPHANT CRIES OUT
0:39:42 > 0:39:47Elephant babies can, and do, get permanently stuck in deep mud.
0:40:12 > 0:40:17Her mother's attempts to help her baby are only making matters worse.
0:40:17 > 0:40:21It's stuck beneath her and she's pushing it deeper still.
0:40:24 > 0:40:29But now the baby's grandmother spots the problem and steps in.
0:40:36 > 0:40:37MUFFLED THUMP
0:40:37 > 0:40:39MOTHER TRUMPETS
0:40:39 > 0:40:42Drastic action! She pushes mother out of the way
0:40:42 > 0:40:44with an unceremonious poke in the rump,
0:40:44 > 0:40:48and enables her granddaughter to scramble free.
0:40:54 > 0:40:58Mother and calf have learned a valuable lesson from grandma.
0:41:01 > 0:41:04Such passing of wisdom across generations
0:41:04 > 0:41:08has been an important element in the survival of elephants.
0:41:24 > 0:41:29The largest animal on land, the elephant is a mammal.
0:41:31 > 0:41:35And so are the largest animals in the sea.
0:41:49 > 0:41:53A female humpback whale and her calf.
0:41:55 > 0:41:59Every few years, she will travel 3,000 miles,
0:41:59 > 0:42:02from the rich waters of the Antarctic
0:42:02 > 0:42:06to these warm, but comparatively sterile, waters of the Pacific
0:42:06 > 0:42:09to give birth to a single calf.
0:42:36 > 0:42:42The seas around Tonga are not only a nursery for humpbacks,
0:42:42 > 0:42:45but also their mating ground.
0:42:45 > 0:42:48WHALE CALLS OUT
0:42:57 > 0:43:02This 50-year-old female has come here to seek the best partner,
0:43:02 > 0:43:06and she starts by announcing her arrival to potential suitors.
0:43:30 > 0:43:33One by one, the males arrive.
0:43:46 > 0:43:49But as they do, she swims away,
0:43:49 > 0:43:54compelling her half a dozen or so suitors to follow her.
0:44:06 > 0:44:12She leads, while the males jockey for position behind her.
0:44:12 > 0:44:14WHALE BELLOWS
0:44:14 > 0:44:17The males bellow threats to one another,
0:44:17 > 0:44:19creating huge plumes of bubbles.
0:44:28 > 0:44:33So far, it has been a relatively gentle affair.
0:44:33 > 0:44:35Now the competition becomes serious.
0:44:38 > 0:44:42Hour after hour, the males battle for position, right behind her.
0:45:04 > 0:45:09And now the 40-tonne males begin to smash into one another.
0:45:31 > 0:45:36This is the most massive battle in all nature.
0:45:36 > 0:45:38Rival males can kill one another.
0:45:48 > 0:45:52As the conflict reaches its climax,
0:45:52 > 0:45:54they try to force each other downwards.
0:46:13 > 0:46:17At last, a victor takes his place alongside the female
0:46:17 > 0:46:20and remains unchallenged.
0:46:23 > 0:46:26By inciting the males to fight,
0:46:26 > 0:46:30the female has secured the best mate for herself -
0:46:30 > 0:46:35the one who is most likely to father the strongest offspring.
0:46:48 > 0:46:51Together, the couple dive to the depths.
0:46:52 > 0:46:56But still, no-one knows where they will mate.
0:47:23 > 0:47:26All mammals, including ourselves,
0:47:26 > 0:47:30share a set of winning characteristics.
0:47:35 > 0:47:42Warm bodies, extraordinary senses and highly-developed intelligence -
0:47:42 > 0:47:48and those qualities have contributed to their, and our, success.
0:47:53 > 0:47:56But perhaps the most important characteristic of all
0:47:56 > 0:47:59lies in the strength of our family ties.
0:48:02 > 0:48:07It is the mammal family that has conquered the earth.
0:48:40 > 0:48:43Tonga is famous for humpback whales,
0:48:43 > 0:48:47but even here, finding and filming whales in the open ocean
0:48:47 > 0:48:49would prove challenging.
0:48:49 > 0:48:50For the Life team,
0:48:50 > 0:48:54capturing the humpback whales' unique mating contest,
0:48:54 > 0:48:55known as a heat run,
0:48:55 > 0:49:01would need local knowledge, hours on the water, and a big slice of luck.
0:49:01 > 0:49:05We've heard that one of the boats further inland
0:49:05 > 0:49:09has seen a female with a calf and an escort,
0:49:09 > 0:49:13which is something which might build to, hopefully, a heat run,
0:49:13 > 0:49:15so we're gonna head over there and take a look.
0:49:15 > 0:49:20Any adult female with a calf could be coming into season,
0:49:20 > 0:49:22and so might be a target for amorous males.
0:49:23 > 0:49:25When we got there, I was pretty excited,
0:49:25 > 0:49:28a little bit nervous, didn't know what to expect.
0:49:31 > 0:49:34Once I got in the water and dived down,
0:49:34 > 0:49:36it was surprisingly quiet and mellow.
0:49:38 > 0:49:41Certainly didn't expect what happened next.
0:49:41 > 0:49:43The calf just came straight up towards me.
0:50:11 > 0:50:15She seemed really relaxed, and definitely interested in me.
0:50:22 > 0:50:26It's literally just swimming around within metres of them,
0:50:26 > 0:50:29flicking its tail, just being inquisitive I think,
0:50:29 > 0:50:30and having a bit of fun.
0:50:36 > 0:50:37It's obviously quite young,
0:50:37 > 0:50:40so it's staying on the surface quite a long time.
0:50:40 > 0:50:41It's not diving down for very long,
0:50:41 > 0:50:44maybe a couple of minutes. The mother will be
0:50:44 > 0:50:47about five or ten metres below just keeping an eye on it.
0:50:57 > 0:51:00But even a calf has great power in its fins and tail.
0:51:00 > 0:51:04Roger will need to be careful.
0:51:14 > 0:51:16Got it?
0:51:18 > 0:51:23That was the most silly thing I've ever seen in my life.
0:51:23 > 0:51:27It was just gambolling around like a little newborn lamb.
0:51:27 > 0:51:28But it's two tonnes.
0:51:28 > 0:51:30THEY LAUGH
0:51:30 > 0:51:34Couple of bumps as it's come round, splashed his fluke at me or whatever.
0:51:34 > 0:51:36I got a great shot of it, Jason.
0:51:36 > 0:51:39Jason was backpedalling like this!
0:51:42 > 0:51:44It's just a baby. Like a little puppy,
0:51:44 > 0:51:47you're playing with a little puppy, but it's four metres long.
0:51:47 > 0:51:51- It's just ludicrous. - Was his mum all right?
0:51:51 > 0:51:53She is just totally chilling out underneath.
0:51:53 > 0:51:57Pecs back. Just hanging like this at about 15 metres.
0:51:57 > 0:51:59Yeah, just hanging there.
0:51:59 > 0:52:01Probably didn't even see it, I don't think.
0:52:04 > 0:52:07It's one thing to be close to a playful baby.
0:52:07 > 0:52:09It will be another to be in the path
0:52:09 > 0:52:12of a testosterone-charged group of males,
0:52:12 > 0:52:16each ten times her size.
0:52:16 > 0:52:18MUTTERED CONVERSATION
0:52:21 > 0:52:26There are enough males here for a heat run, but are they in the mood?
0:52:27 > 0:52:28Oh!
0:52:28 > 0:52:30- Woo-hoo!- Yes!
0:52:33 > 0:52:34That was pretty good.
0:52:38 > 0:52:39When you guys are ready.
0:52:41 > 0:52:42Quick as you can.
0:52:51 > 0:52:55These whales can weigh up to 40 tonnes and move surprisingly quickly.
0:52:55 > 0:52:57As well as getting the camera to get the shots -
0:52:57 > 0:52:58they have to be fairly close -
0:52:58 > 0:53:01we have to be careful they don't get bumped.
0:53:01 > 0:53:03If they get a knock from one of these guys,
0:53:03 > 0:53:05it could do some serious damage.
0:53:12 > 0:53:13He's right towards you.
0:53:13 > 0:53:16To avoid disturbing the whales' behaviour,
0:53:16 > 0:53:22the team need to free-dive, without scuba tanks,
0:53:22 > 0:53:24holding their breath as long as they can.
0:53:24 > 0:53:28On a good dive, I can hold my breath for maybe two minutes.
0:53:28 > 0:53:31These guys, they can go for 20 minutes or more
0:53:31 > 0:53:33before they have to come up for air.
0:53:33 > 0:53:34There's no contest.
0:53:34 > 0:53:37More and more whales are gathering,
0:53:37 > 0:53:40but it's not turning into a heat run yet.
0:53:48 > 0:53:50Hard to say what's going on.
0:53:51 > 0:53:54Were there five that time?
0:53:56 > 0:54:00They're kind of moving around, coming up and under and over.
0:54:00 > 0:54:02Hopefully, something's starting to happen.
0:54:02 > 0:54:03Maybe love's in the air?
0:54:03 > 0:54:05HE CHUCKLES
0:54:09 > 0:54:13Love may be in the air, but it isn't in the water.
0:54:13 > 0:54:17Despite keeping tabs on the whales over the next ten days,
0:54:17 > 0:54:19there was still no sign of a heat run starting.
0:54:19 > 0:54:23You'd think it'd be quite easy to keep track of a 40-tonne animal.
0:54:23 > 0:54:26And we've got six of them out here,
0:54:26 > 0:54:29and we keep losing them. One minute they're there,
0:54:29 > 0:54:30we get up reasonably close,
0:54:30 > 0:54:34and within 30 seconds, they've dived and they're gone again.
0:54:34 > 0:54:37And then it takes another maybe five minutes, ten minutes,
0:54:37 > 0:54:41and then they'll come up again and they'll be 300 yards away,
0:54:41 > 0:54:43and it takes ages just to get close to them.
0:54:43 > 0:54:47So we're just playing a continuous game of cat and mouse.
0:54:49 > 0:54:52Cat and mouse? It's whales.
0:54:53 > 0:54:56The mating season is coming to an end,
0:54:56 > 0:54:59and the crew haven't completed their mission.
0:54:59 > 0:55:03But then, at last, the whales' behaviour seems to have changed.
0:55:05 > 0:55:06Well, this is it!
0:55:06 > 0:55:09We just spotted about six or seven humpbacks on the horizon.
0:55:09 > 0:55:11We think it's a heat run.
0:55:11 > 0:55:14The last 16, 17 days on the water
0:55:14 > 0:55:17are probably gonna come down to the next two hours,
0:55:17 > 0:55:19as to whether we get our shots or not.
0:55:19 > 0:55:21The chase is on!
0:55:48 > 0:55:51There was at least three or four males going past -
0:55:51 > 0:55:53they were competing and knocking into each other
0:55:53 > 0:55:56as they tried to get the poll position behind the female.
0:55:56 > 0:55:59It's right at you, it's right at you.
0:55:59 > 0:56:03The whales are moving so fast that, to stand any chance of filming them,
0:56:03 > 0:56:07the crew needs to be dropped right in front of the charging group.
0:56:22 > 0:56:25Just as Roger gets alongside the males,
0:56:25 > 0:56:28the tempo of the chase suddenly shifts to full bore
0:56:28 > 0:56:29with a flick of a tail.
0:56:44 > 0:56:49Facing the charging males deep underwater, Roger keeps shooting,
0:56:49 > 0:56:51holding his breath until the group pass over.
0:57:00 > 0:57:04A quick gasp of air, and Roger's back down again.
0:57:14 > 0:57:17The whales continue to rush by.
0:57:17 > 0:57:20In the end, Roger just can't keep up any longer.
0:57:27 > 0:57:33Exhausted, it's time to return to the boat for the last time.
0:57:33 > 0:57:36Amazing! That was the most amazing experience I've ever had.
0:57:36 > 0:57:38There was about...
0:57:38 > 0:57:43seven or eight. Both dived down about 20 metres in front.
0:57:43 > 0:57:47And then the female came through first, quite close.
0:57:47 > 0:57:49And then they all just started diving towards me,
0:57:49 > 0:57:52it was like standing in a stream of traffic.
0:57:52 > 0:57:55It was just one one side, one the next side, one the next side.
0:57:55 > 0:57:57And then, after about 40 seconds,
0:57:57 > 0:58:0140, 45 seconds, I was getting a little bit out of breath.
0:58:01 > 0:58:06And then I looked up, and there's one sitting right on top of me.
0:58:06 > 0:58:09- Did you get it?- I think so. Hope so.
0:58:09 > 0:58:11If not, then we're both fired!
0:58:13 > 0:58:18It's taken 18 days and hundreds of dives,
0:58:18 > 0:58:21but at last the team have been able to reveal a secret
0:58:21 > 0:58:25of these whales' lives that few people have ever seen.
0:58:44 > 0:58:47Subtitles by Red Bee Media Ltd
0:58:47 > 0:58:50E-mail subtitling@bbc.co.uk