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