0:00:02 > 0:00:05These are our planet's winter wonderlands.
0:00:07 > 0:00:10And the remarkable animals that call them home.
0:00:13 > 0:00:17I'm Gordon Buchanan and, as a wildlife cameraman,
0:00:17 > 0:00:21I've visited many of these unique and special places.
0:00:21 > 0:00:25But the animals that live in places like this need to be resilient,
0:00:25 > 0:00:28and many of them are specially adapted
0:00:28 > 0:00:30to make the very most of these seasonal conditions.
0:00:30 > 0:00:34I'm going to reveal the extraordinary animals
0:00:34 > 0:00:38that don't just survive, but positively thrive, in the snow.
0:00:40 > 0:00:42Oh, very, very cute!
0:00:42 > 0:00:48Each has different and surprising tactics to face winter head-on.
0:00:48 > 0:00:49From the polar bear mother,
0:00:49 > 0:00:52who spends seven months without food and water
0:00:52 > 0:00:54to give her babies the best start in life.
0:00:54 > 0:00:59To the fox, who can catch food it can't even see.
0:01:01 > 0:01:05And a seasonal specialist, the reindeer,
0:01:05 > 0:01:10and a surprising secret behind that red nose.
0:01:10 > 0:01:13Just how these animals make these places their own
0:01:13 > 0:01:17are amongst the most incredible stories in the natural world.
0:01:17 > 0:01:19I hope you've snuggled up nice and warm,
0:01:19 > 0:01:21because it's time to meet the amazing animals
0:01:21 > 0:01:24that spend their life in the snow.
0:01:39 > 0:01:43Each year, up to one third of our planet is transformed by snow
0:01:43 > 0:01:48into a sparkling world of wonder and white.
0:01:52 > 0:01:57The animals who live here must adapt to this dazzling change.
0:02:03 > 0:02:07How they rise to the challenge of living in the snow
0:02:07 > 0:02:09is what sets each of them apart.
0:02:18 > 0:02:22Our first animal is the world's largest land carnivore.
0:02:22 > 0:02:26They face the coldest temperatures the Arctic has to offer.
0:02:29 > 0:02:32But they seem to take it all in their stride.
0:02:34 > 0:02:35The polar bear.
0:02:36 > 0:02:40Most animals couldn't live this close to the North Pole.
0:02:41 > 0:02:44But he appears to be revelling in it.
0:02:49 > 0:02:53In fact, the bears roll in the snow when they want to cool down.
0:02:55 > 0:02:59But how is it possible to get too hot in the Arctic?
0:03:04 > 0:03:09The polar bear has the thickest fur of any bear.
0:03:09 > 0:03:13But, it's the 11 centimetre fat layer beneath the skin
0:03:13 > 0:03:15that makes all the difference.
0:03:16 > 0:03:20It keeps in the heat like nothing else.
0:03:22 > 0:03:24It works so well,
0:03:24 > 0:03:30polar bears can swim for mile after mile in the freezing Arctic Sea.
0:03:46 > 0:03:48To maintain this vital layer,
0:03:48 > 0:03:53they need to eat as much fatty food as they can find.
0:03:59 > 0:04:03The polar bears' staple diet is seal.
0:04:03 > 0:04:07But they spend most of their time under the ice.
0:04:10 > 0:04:13The bear can't afford a drawn-out game of hide and seek.
0:04:17 > 0:04:21His sense of smell is 100 times better than ours.
0:04:25 > 0:04:28Able to track a scent from 20 miles away.
0:04:39 > 0:04:43A bear can smell a seal through a metre of snow.
0:04:49 > 0:04:54A seal can be nearly 50% blubber.
0:05:03 > 0:05:04He'll catch nearly one a week,
0:05:04 > 0:05:08enough to keep his insulation in top condition.
0:05:13 > 0:05:18At this time of year, female polar bears have a very different problem.
0:05:18 > 0:05:22They have their cubs in the depths of the Arctic winter.
0:05:27 > 0:05:30A polar bear simply can't give birth out on the Arctic ice -
0:05:30 > 0:05:34with such small, vulnerable babies, it is way too cold.
0:05:34 > 0:05:36Down to minus 50 Celsius.
0:05:36 > 0:05:40So, for a pregnant mother living in such a cold and exposed place,
0:05:40 > 0:05:44there's really only one place to be.
0:05:44 > 0:05:46And that is underneath the snow.
0:05:52 > 0:05:54It might sound counterintuitive,
0:05:54 > 0:05:57but we can actually use snow to keep us warm.
0:05:57 > 0:06:00Within this lump of snow is trapped air,
0:06:00 > 0:06:04and trapped air makes a fantastic insulator.
0:06:04 > 0:06:08So, when you're in a snow hole, or a snow den,
0:06:08 > 0:06:10you could even get cosy.
0:06:14 > 0:06:19And, when a polar bear is underneath the snow like this,
0:06:19 > 0:06:24the temperature inside can be an incredible 30 degrees warmer
0:06:24 > 0:06:28than the temperature outside.
0:06:28 > 0:06:31And when she's hidden in a den like this,
0:06:31 > 0:06:34that's when something truly remarkable happens.
0:06:37 > 0:06:41Around the turn of the New Year, across the Arctic,
0:06:41 > 0:06:44under three feet of snow and ice...
0:06:45 > 0:06:48..female polar bears give birth.
0:06:57 > 0:07:02Then in early spring, they emerge for the first time.
0:07:06 > 0:07:08April in Svalbard.
0:07:08 > 0:07:11Just the right moment to see this happen.
0:07:15 > 0:07:16Aw!
0:07:16 > 0:07:19Oh, very, very cute!
0:07:24 > 0:07:28Both cubs combined aren't even as big as the mother's head.
0:07:35 > 0:07:36At three months old,
0:07:36 > 0:07:40this is their very first experience of the outside world.
0:07:46 > 0:07:50During her time in the den, she loses half her body weight.
0:07:52 > 0:07:55Her milk is 30% fat,
0:07:55 > 0:07:57so her cubs grow fast.
0:08:01 > 0:08:03Oh...
0:08:03 > 0:08:05Wow.
0:08:05 > 0:08:07Look at that!
0:08:11 > 0:08:16They're already 20 times heavier than when they were born.
0:08:19 > 0:08:23Just about big enough to take on their frozen world.
0:08:23 > 0:08:27And it's all down to their mother's winter hidden beneath the snow.
0:08:35 > 0:08:38Polar bears aren't the only animals to use this strategy.
0:08:40 > 0:08:45Our very own common dormouse spends more than half of its life asleep.
0:08:47 > 0:08:49Avoiding the winter altogether.
0:08:53 > 0:08:58And the Arctic ground squirrel can let its body temperature drop
0:08:58 > 0:09:00to 2.9 degrees below freezing.
0:09:04 > 0:09:07It's the coldest any mammal can get.
0:09:07 > 0:09:11Remarkably, it appears to change the chemistry of its body
0:09:11 > 0:09:13to stop ice crystals forming.
0:09:16 > 0:09:18Every few weeks, it has to feed,
0:09:18 > 0:09:21so it shivers and shakes in its sleep
0:09:21 > 0:09:24to raise its temperature just enough to wake up.
0:09:29 > 0:09:32But bears are the most impressive hibernators of all.
0:09:35 > 0:09:39Able to survive up to seven months without food or water.
0:09:44 > 0:09:46There is no doubt about it.
0:09:46 > 0:09:50Taking shelter beneath the snow is a really good strategy.
0:09:50 > 0:09:53For a baby bear, for the first few months of its life,
0:09:53 > 0:09:55the den is its world.
0:09:55 > 0:09:59But sooner or later, mother bears and the cubs do need to emerge.
0:09:59 > 0:10:03And getting the timing right is absolutely critical.
0:10:07 > 0:10:09It's spring in North America.
0:10:12 > 0:10:16And this young female black bear has just come out of her den.
0:10:17 > 0:10:22In a normal year, she'd emerge to greet a brand-new spring.
0:10:24 > 0:10:29But an unexpected cold front has blown in from the Arctic.
0:10:35 > 0:10:39What's worse, she has three-month-old twin cubs with her.
0:10:43 > 0:10:46This is her first ever litter.
0:10:48 > 0:10:51She should be keeping them warm.
0:10:51 > 0:10:54Instead, she gets up and leaves.
0:10:57 > 0:11:01After half a year in hibernation, she's desperate for food.
0:11:03 > 0:11:08Her cubs don't have the three layers of waterproof fur
0:11:08 > 0:11:11all adults bears grow - they're defenceless in this weather.
0:11:16 > 0:11:20Their instinctive survival strategy is to climb a tree.
0:11:29 > 0:11:32But this only works for avoiding predators.
0:11:32 > 0:11:36Up here, they're even more exposed to the cold.
0:11:48 > 0:11:51At last, their mum returns.
0:12:02 > 0:12:06But straightaway, she sets off again.
0:12:14 > 0:12:19Walking in thick snow is almost impossible on little legs.
0:12:27 > 0:12:29They struggle to keep up.
0:12:30 > 0:12:33Hopefully, Mum has a plan to keep them warm and safe.
0:12:57 > 0:13:01Overnight, temperatures drop to minus 12 degrees.
0:13:13 > 0:13:16Dawn. The storm has passed.
0:13:16 > 0:13:18But, what about the cubs?
0:13:30 > 0:13:34Their mother led them to a sheltered spot
0:13:34 > 0:13:39and kept them warm through the chill of the night with her own body heat.
0:13:57 > 0:14:01Experience can make all the difference to living in the snow.
0:14:02 > 0:14:07It's been a steep learning curve for this family, but they've made it.
0:14:17 > 0:14:20Being ready and equipped for the cold is critical.
0:14:21 > 0:14:22As I can show you.
0:14:25 > 0:14:27This is a thermal camera.
0:14:27 > 0:14:30It sees temperature as different colours.
0:14:30 > 0:14:32Right now, I'm just wearing a thin top,
0:14:32 > 0:14:35and it should show me losing body heat in red and white.
0:14:37 > 0:14:39Now, as I stand here,
0:14:39 > 0:14:43I can actually feel the cold nipping at my exposed skin.
0:14:43 > 0:14:46On the thermal camera that will show as white hot.
0:14:46 > 0:14:49So it's all about layering up.
0:14:49 > 0:14:54It's about keeping that heat in, and we do that with insulation.
0:14:55 > 0:14:58For any animal that lives in a snowy wilderness,
0:14:58 > 0:15:02they've got to be able to take the cold in their stride.
0:15:03 > 0:15:07And there is one very special animal that does that better than most.
0:15:12 > 0:15:14The Arctic fox.
0:15:18 > 0:15:23They live further north than any other member of the dog family.
0:15:24 > 0:15:27And something extraordinary makes this possible.
0:15:30 > 0:15:33In the warm days of summer, they look very different.
0:15:37 > 0:15:40Then, every year, as the winter approaches,
0:15:40 > 0:15:44they undergo a spellbinding transformation.
0:15:51 > 0:15:56They grow a thick, snow-white winter coat.
0:16:04 > 0:16:07I'm lucky to be able to see this up close,
0:16:07 > 0:16:09with a fox that's been brought up by people.
0:16:15 > 0:16:17Hello, you handsome, handsome boy.
0:16:20 > 0:16:21My word.
0:16:23 > 0:16:29That is the most sumptuous coat I have ever seen on any animal.
0:16:29 > 0:16:34In fact, Arctic foxes have the warmest coat of all Arctic mammals.
0:16:40 > 0:16:44In winter, their fur becomes 200% thicker.
0:16:48 > 0:16:50There's a longer, outer layer,
0:16:50 > 0:16:54with hollow hairs that trap air to increase insulation.
0:16:54 > 0:16:57And a dense undercoat provides even more warmth.
0:17:00 > 0:17:04An Arctic fox won't even start feeling the cold
0:17:04 > 0:17:07until it's minus 40 degrees.
0:17:12 > 0:17:16And, they have other clever features that help them get through winter.
0:17:18 > 0:17:22Their ears are round and tucked into their deep fur to reduce heat loss.
0:17:24 > 0:17:29And, to prevent frostbite, their nose is short and stubby.
0:17:32 > 0:17:34And a magnificent tail
0:17:34 > 0:17:37means that when the Arctic weather is at its worst,
0:17:37 > 0:17:40they can hunker down and use it as a blanket.
0:17:48 > 0:17:53Being well-dressed for winter is an obvious advantage.
0:17:53 > 0:17:56But to survive in a snowy landscape like this,
0:17:56 > 0:18:01you have to be able to exploit every single opportunity to get food.
0:18:01 > 0:18:03And foxes are experts at that.
0:18:06 > 0:18:08They have incredible senses.
0:18:09 > 0:18:11Particularly their hearing.
0:18:13 > 0:18:16And, despite having these fairly small ears,
0:18:16 > 0:18:21this fox will be able to detect its prey with pinpoint accuracy,
0:18:21 > 0:18:23even when it's hidden underneath the snow.
0:18:28 > 0:18:32But learning how to use this skill takes time.
0:18:34 > 0:18:39Their preferred food are lemmings, small, Arctic rodents.
0:18:41 > 0:18:44Many foxes won't make it through their first year
0:18:44 > 0:18:47and that's mostly down to a lack of food.
0:18:49 > 0:18:52Their sensitive hearing means they can detect
0:18:52 > 0:18:54lemmings scurrying through tunnels in the snow.
0:18:56 > 0:19:00But the fox also has to judge the depth of the snow.
0:19:02 > 0:19:03And then...
0:19:11 > 0:19:13..with this dramatic pounce,
0:19:13 > 0:19:16he's trying to punch right through the snow
0:19:16 > 0:19:19and catch the lemming underneath.
0:19:22 > 0:19:24It isn't easy.
0:19:30 > 0:19:33But practice makes perfect.
0:19:46 > 0:19:50The fox's ability to track down prey using its hearing alone
0:19:50 > 0:19:52is truly amazing.
0:19:55 > 0:19:58Relying on your hearing in the snow can be a real challenge.
0:19:58 > 0:20:01Have you ever noticed that when there's a blanket of snow,
0:20:01 > 0:20:03the world seems a very silent place?
0:20:03 > 0:20:08That is because the snow literally deadens the sound waves.
0:20:08 > 0:20:12The snow stops the sound from bouncing and reflecting off things.
0:20:12 > 0:20:14In my pocket I have a speaker,
0:20:14 > 0:20:17and on this speaker, I have the sound of a vole.
0:20:18 > 0:20:22To many creatures, voles means food.
0:20:22 > 0:20:26SCRABBLING NOISE
0:20:26 > 0:20:31See, if your dinner relies on you being able to detect these little
0:20:31 > 0:20:35creatures that are scurrying about, beneath the grass, beneath the snow,
0:20:35 > 0:20:37you'll see what the challenge is.
0:20:37 > 0:20:38Pretty loud.
0:20:38 > 0:20:40There's the vole.
0:20:49 > 0:20:51I can barely hear it.
0:20:52 > 0:20:55It's almost completely gone.
0:20:56 > 0:20:57OK.
0:20:58 > 0:21:00So I'm about a foot and a half above the speaker,
0:21:00 > 0:21:04and I can just about hear it.
0:21:04 > 0:21:07Thankfully, I don't rely on voles for food.
0:21:09 > 0:21:12But, what if you had to listen out for this sound
0:21:12 > 0:21:15from high above the snow?
0:21:17 > 0:21:20That's the challenge faced by the great grey owl.
0:21:23 > 0:21:27But this magnificent bird pinpoints sound so accurately,
0:21:27 > 0:21:29it can launch a strike from the air.
0:21:41 > 0:21:44So, how does it achieve this incredible feat?
0:21:51 > 0:21:56The disc shaped feathers on its face collect the sound waves
0:21:56 > 0:22:00and directs them to the ears on the side of its head.
0:22:02 > 0:22:06It can work out exactly where the sound is coming from.
0:22:09 > 0:22:12These skills come into their own when the owl takes to the wing.
0:22:19 > 0:22:21Special edging on its feathers
0:22:21 > 0:22:25mean that its flight is completely silent.
0:22:36 > 0:22:38Nothing can hear it coming.
0:22:47 > 0:22:49In the final moments,
0:22:49 > 0:22:52it brings its talons into exact alignment
0:22:52 > 0:22:54with the sound of the prey.
0:23:14 > 0:23:18Catching a meal without ever seeing it.
0:23:18 > 0:23:19Phenomenal.
0:23:20 > 0:23:23But there is another way to find a vole under the snow,
0:23:23 > 0:23:26and that's to go in after it.
0:23:29 > 0:23:33Although the least weasel is several times larger than a vole,
0:23:33 > 0:23:36its body is exactly the same width.
0:23:42 > 0:23:44Once the weasel finds a hole,
0:23:44 > 0:23:48it's an old-fashioned game of cat and mouse.
0:24:05 > 0:24:08Although it doesn't always end in getting dinner.
0:24:11 > 0:24:12Whatever the outcome,
0:24:12 > 0:24:16at least the weasel is small enough to take shelter beneath the snow,
0:24:16 > 0:24:18away from the worst of the weather.
0:24:23 > 0:24:27But, what if you aren't able to get out of the cold?
0:24:28 > 0:24:31Well, one animal has some surprising ways to cope.
0:24:43 > 0:24:47Reindeer. There could not be another animal more closely associated
0:24:47 > 0:24:49with snow and Christmas.
0:24:54 > 0:24:58And, there could even be some truth in that famous red nose.
0:25:02 > 0:25:06Reindeer live in the forests and tundra of the far north.
0:25:06 > 0:25:10In winter, they dig through the snow to find food.
0:25:12 > 0:25:15Out here, they're breathing in air
0:25:15 > 0:25:18at temperatures down to minus 40 Celsius.
0:25:21 > 0:25:23To stop it chilling their lungs,
0:25:23 > 0:25:26they pass the air through chambers in their nose...
0:25:28 > 0:25:31..where a network of blood vessels heat it up.
0:25:35 > 0:25:37We can see this on the thermal camera.
0:25:39 > 0:25:44Where they warm the air up, their noses really are red.
0:25:46 > 0:25:49And, when they breathe out,
0:25:49 > 0:25:52their noses take the precious body heat from their breath,
0:25:52 > 0:25:54so it isn't lost to the atmosphere.
0:26:00 > 0:26:03And it isn't the only thing
0:26:03 > 0:26:06that makes reindeer so well-equipped for snow.
0:26:07 > 0:26:13I am a perfect example of an animal that is not adapted
0:26:13 > 0:26:17for walking about a snowy environment like this.
0:26:19 > 0:26:21I'm 12 stone, 12 and a half stone,
0:26:21 > 0:26:26and all of my weight is distributed onto my feet.
0:26:26 > 0:26:28Size 12. Big feet for a human,
0:26:28 > 0:26:32but not big enough to stop me from sinking down into the snow.
0:26:36 > 0:26:40So, why don't reindeer have the same issue?
0:26:40 > 0:26:44The answer lies in their specially adapted feet.
0:26:44 > 0:26:49Their four toes splay out to increase their surface area,
0:26:49 > 0:26:53stopping them from sinking, and giving them traction.
0:26:56 > 0:27:00This ability is one reason we domesticated the reindeer.
0:27:02 > 0:27:04The Dolgan people of Siberia
0:27:04 > 0:27:07use reindeer for their nomadic lifestyle,
0:27:07 > 0:27:11literally moving house every week or so, with their help.
0:27:18 > 0:27:21So clearly, I need to increase the surface area of my feet.
0:27:24 > 0:27:28There we go. Adapted for walking in the snow.
0:27:28 > 0:27:30Big surface area to stop me sinking through,
0:27:30 > 0:27:33spikes to stop me slipping on the ice.
0:27:40 > 0:27:43That is so much better.
0:27:43 > 0:27:45It's easy. I can walk through the forests,
0:27:45 > 0:27:48I'm not sinking down into my waist, I can go fast,
0:27:48 > 0:27:50I can almost go silently.
0:27:52 > 0:27:53Like I belong here.
0:27:58 > 0:28:01Other animals also use this approach.
0:28:04 > 0:28:09Polar bears have huge paws, 30 centimetres across.
0:28:11 > 0:28:15And their pads are covered with tiny bumps to give extra grip.
0:28:19 > 0:28:23And the snowshoe hare has long, fur-covered feet
0:28:23 > 0:28:26to help it move effortlessly across the snow.
0:28:30 > 0:28:33Yet, despite their special equipment,
0:28:33 > 0:28:37even reindeer find sheet ice a little tricky.
0:28:47 > 0:28:51But reindeer have something else that really sets them apart.
0:28:53 > 0:28:55Their eyesight.
0:28:57 > 0:29:00When it's bright and sunny like this,
0:29:00 > 0:29:01my eyes struggle to cope
0:29:01 > 0:29:06with the amount of UV light that's coming from the sun,
0:29:06 > 0:29:08is bouncing back up off the snow.
0:29:08 > 0:29:12But reindeer, they see things differently.
0:29:12 > 0:29:15Not only can they see in colour like I can,
0:29:15 > 0:29:17they can also see in ultraviolet.
0:29:19 > 0:29:21And that's vital.
0:29:21 > 0:29:25Because some very important things show up in ultraviolet.
0:29:31 > 0:29:34Tracks in the snow show up clearly,
0:29:34 > 0:29:37helping reindeer find a path.
0:29:43 > 0:29:46They can see the telltale scent marks of predators in the snow.
0:29:49 > 0:29:55And most important of all, a staple part of their winter diet, lichen,
0:29:55 > 0:29:57stands out like a beacon.
0:30:05 > 0:30:08So, when deep snow covers the other plants they eat,
0:30:08 > 0:30:11they can hone in on this extra food source.
0:30:14 > 0:30:19No wonder reindeer are so closely associated with this time of year.
0:30:19 > 0:30:24With these specialist skills, they can get through the deepest winter.
0:30:43 > 0:30:45When temperatures plummet,
0:30:45 > 0:30:50we start burning more calories, just to keep warm.
0:30:50 > 0:30:53So, finding extra food can make all the difference.
0:30:53 > 0:30:55In fact, it's vital.
0:30:55 > 0:30:59But when your larder is frozen solid, you have to be resourceful.
0:31:02 > 0:31:03The robin.
0:31:04 > 0:31:07The gardener's colourful companion
0:31:07 > 0:31:10relies on soft earth to pick out worms and grubs.
0:31:12 > 0:31:16But a deep frost means the ground is frozen solid.
0:31:18 > 0:31:21If only there were someone to dig it up.
0:31:24 > 0:31:29Deep underground, in total darkness, where the frost can't reach,
0:31:29 > 0:31:31moles are digging their tunnels.
0:31:32 > 0:31:36And pushing up fresh, soft piles of earth.
0:31:38 > 0:31:41For the robin redbreast, this is an opportunity.
0:31:55 > 0:31:57It's a real lifeline.
0:31:59 > 0:32:03And one that could continue for the whole winter.
0:32:08 > 0:32:10When food is hard to find,
0:32:10 > 0:32:13joining forces can help.
0:32:19 > 0:32:24And one resourceful animal has worked out just how to do this.
0:32:27 > 0:32:31Wolverines are the largest member of the weasel family.
0:32:39 > 0:32:41In winter, most of their diet
0:32:41 > 0:32:44is made up of the animals that haven't made it through
0:32:44 > 0:32:46these testing times.
0:32:49 > 0:32:52But, with the world covered by snow,
0:32:52 > 0:32:55it could take hours to find this meal.
0:32:55 > 0:32:59This is where the wolverine's resourcefulness comes in.
0:32:59 > 0:33:02It has an airborne spotter.
0:33:07 > 0:33:08Ravens.
0:33:08 > 0:33:12One of the most intelligent birds in the world.
0:33:12 > 0:33:13Although it's found a moose,
0:33:13 > 0:33:17a raven isn't strong enough to dig it out of the snow.
0:33:19 > 0:33:22So it calls out, attracting the wolverine's attention.
0:33:24 > 0:33:28It will even lead its ally towards the food.
0:33:38 > 0:33:42Wolverines are renowned for their strength.
0:33:43 > 0:33:46But the meat is frozen solid.
0:33:51 > 0:33:55Fortunately, there's an answer for that.
0:33:59 > 0:34:03The wolverine is one of the only animals on the planet
0:34:03 > 0:34:06whose teeth and jaws are specifically adapted
0:34:06 > 0:34:08for eating frozen food.
0:34:09 > 0:34:12They can cut through meat and bone as hard as concrete.
0:34:22 > 0:34:25This is what the raven's been waiting for.
0:34:25 > 0:34:29Newly revealed leftovers are their reward for finding food.
0:34:43 > 0:34:46And there's one final clever strategy
0:34:46 > 0:34:48in case times get really tough.
0:34:48 > 0:34:51The wolverine will bury part of the meal,
0:34:51 > 0:34:54storing it away in the freezer for later.
0:34:56 > 0:34:59Two different species working together like this
0:34:59 > 0:35:02is rare in the natural world.
0:35:03 > 0:35:06But, when you live in one of the toughest places on Earth,
0:35:06 > 0:35:08it can make sense to work as a team.
0:35:11 > 0:35:14Musk ox are Arctic giants.
0:35:14 > 0:35:18They live in family groups of around 20 in the northern tundra,
0:35:18 > 0:35:22where they face some of the planet's most extreme weather.
0:35:30 > 0:35:34When it comes to being prepared for the coldest part of winter,
0:35:34 > 0:35:37these musk ox certainly look ready.
0:35:37 > 0:35:42That long, thick, shaggy coat is so efficient,
0:35:42 > 0:35:46a musk ox only uses a small amount of energy to keep warm.
0:35:47 > 0:35:50They can even slow down their metabolism
0:35:50 > 0:35:54so that in the winter time they require less food.
0:35:54 > 0:35:57Because finding that food can be a challenge.
0:36:07 > 0:36:12In winter, the snow is covered with a thick layer of ice,
0:36:12 > 0:36:14making it hard to get to the plants beneath.
0:36:17 > 0:36:22So musk ox use their large front hooves like snow shovels.
0:36:26 > 0:36:29And the neighbours are quick to spot an opportunity.
0:36:32 > 0:36:37Ptarmigan, hardy Arctic birds that also feed on plants,
0:36:37 > 0:36:40but can't break through the ice on their own.
0:36:45 > 0:36:48Arctic hares join the winter feast too.
0:36:49 > 0:36:52Soon, the musk ox have quite an entourage.
0:36:59 > 0:37:03But finding food is just one of their problems.
0:37:05 > 0:37:09Protecting their calves is perhaps the most important.
0:37:09 > 0:37:12They're born just before the spring.
0:37:14 > 0:37:17Everything is new to this calf.
0:37:17 > 0:37:20But the snow is a particular challenge.
0:37:26 > 0:37:29It'll need to get to grips with it soon.
0:37:31 > 0:37:32There are predators here.
0:37:35 > 0:37:37Arctic wolves.
0:37:37 > 0:37:41They are big, strong, and live in packs.
0:37:46 > 0:37:48The calves are vulnerable.
0:37:50 > 0:37:52They must try to keep up.
0:38:05 > 0:38:10The musk ox form a defensive ring, with the calves in the middle.
0:38:14 > 0:38:19A wolf would be foolish to mess with this impenetrable wall of musk ox.
0:38:27 > 0:38:30When it comes to living in the Arctic,
0:38:30 > 0:38:33these animals are hard to beat.
0:38:33 > 0:38:36LONE WOLF HOWLS
0:38:36 > 0:38:38PACK HOWLS
0:38:41 > 0:38:44Relying on hunting to get a meal is always a challenge.
0:38:46 > 0:38:50So how do predators like wolves get through the toughest time of year?
0:38:50 > 0:38:55Here in northern Norway, these wolves are habituated to people.
0:39:02 > 0:39:04It's a rare opportunity
0:39:04 > 0:39:08to get closer than would ever be possible with a fully wild pack.
0:39:17 > 0:39:19Hello.
0:39:26 > 0:39:28Look at the size of the paws.
0:39:29 > 0:39:31You are a beaut.
0:39:31 > 0:39:34Just stroking this wolf,
0:39:34 > 0:39:38you could lose your hand in its coat.
0:39:40 > 0:39:46And when I part the hair you can see that underneath there's these fine,
0:39:46 > 0:39:51very soft hairs that gives insulation.
0:39:51 > 0:39:56And these longer outer hairs repel the snow and water.
0:39:58 > 0:40:01His coat is perfect for these conditions.
0:40:03 > 0:40:05Look how narrow the wolf is,
0:40:05 > 0:40:09you look at the wolf face on, it's got this big head.
0:40:09 > 0:40:12But its shoulders are quite narrow, and that's a physical adaptation
0:40:12 > 0:40:15that helps him move around through deep snow.
0:40:18 > 0:40:21So, no matter what physical characteristics you have,
0:40:21 > 0:40:24clever hunting strategy is essential.
0:40:24 > 0:40:27And in these bitterly cold conditions,
0:40:27 > 0:40:29it helps to have friends.
0:40:35 > 0:40:38Wolves live in tight-knit family groups.
0:40:40 > 0:40:41There's a strict hierarchy.
0:40:43 > 0:40:45Alpha males and females are in charge.
0:40:45 > 0:40:48Every pack member knows their place.
0:40:57 > 0:41:00The strong relationships between the wolves are critical
0:41:00 > 0:41:02for getting through hard times.
0:41:05 > 0:41:09It's February in Yellowstone National Park.
0:41:18 > 0:41:21At this stage of winter, the elk are weak.
0:41:27 > 0:41:31But elk are several times the size of a wolf.
0:41:35 > 0:41:37They need to work together.
0:41:40 > 0:41:44One wolf charges, making the elk run.
0:41:55 > 0:42:00They can identify the weakest animal by the way it acts and moves.
0:42:03 > 0:42:06One wolf cuts the elk away from the herd.
0:42:07 > 0:42:11While two more come in from the sides.
0:42:11 > 0:42:16A tactical manoeuvre that means the whole family will feed.
0:42:18 > 0:42:22HOWLING
0:42:26 > 0:42:31A wolf's ability to hunt as a team, as a pack,
0:42:31 > 0:42:34that's really what helps guarantee its survival.
0:42:41 > 0:42:42In Yellowstone,
0:42:42 > 0:42:45the wolves have found a way to get through the harsh winter.
0:42:49 > 0:42:52But, for other animals that live here,
0:42:52 > 0:42:55there's another way to survive.
0:43:05 > 0:43:08These bison are caught in the grip
0:43:08 > 0:43:11of the worst winter for a generation.
0:43:18 > 0:43:21The snow is too deep to break through.
0:43:21 > 0:43:23And they need to eat.
0:43:30 > 0:43:32But Yellowstone holds a secret.
0:43:36 > 0:43:39This winter wonderland has a burning heart.
0:43:43 > 0:43:45Formed on a giant volcano,
0:43:45 > 0:43:48Yellowstone is peppered with thousands of hot springs
0:43:48 > 0:43:50and spectacular spouting geysers.
0:43:54 > 0:43:57The bison can take advantage of this,
0:43:57 > 0:43:59but they need to move.
0:44:17 > 0:44:20They're taking a big risk.
0:44:20 > 0:44:24This journey could use all their remaining strength.
0:44:28 > 0:44:31Some won't make it.
0:44:34 > 0:44:36But even as night falls,
0:44:36 > 0:44:38the bison push on.
0:45:08 > 0:45:11The herd have reached an oasis.
0:45:16 > 0:45:19The hot springs warm the air,
0:45:19 > 0:45:22and melt the snow.
0:45:25 > 0:45:26And there's grass here.
0:45:43 > 0:45:46But this paradise is too good to be true.
0:45:50 > 0:45:55Volcanic springs can contain toxic chemicals like arsenic.
0:45:56 > 0:45:59Over time, this could make the bison ill.
0:46:02 > 0:46:06But, right now, this is the lifeline they need.
0:46:10 > 0:46:13Knowing every secret in the landscape
0:46:13 > 0:46:16can make all the difference to surviving in the snow.
0:46:22 > 0:46:27And some animals take using thermal springs to a whole new level.
0:46:34 > 0:46:36In these heated pools,
0:46:36 > 0:46:40Japanese macaques take refuge from the freezing winter temperatures.
0:46:44 > 0:46:48The water is a steamy 41 degrees Celsius.
0:46:54 > 0:46:57It's not just a chance to keep warm, though,
0:46:57 > 0:47:00it's also an opportunity for the group to socialise.
0:47:04 > 0:47:07But this spa is exclusive.
0:47:08 > 0:47:11Only the elite of macaque society are permitted entry.
0:47:18 > 0:47:23The rest are left on the sidelines to look for other distractions.
0:47:34 > 0:47:36Even the less privileged monkeys are lucky,
0:47:36 > 0:47:39compared to those animals that live in the coldest
0:47:39 > 0:47:41and most extreme place on the planet.
0:47:45 > 0:47:48On the day like this in the mountains,
0:47:48 > 0:47:50the temperature is about minus 1, minus 2.
0:47:50 > 0:47:52On a different day with a bit of wind chill,
0:47:52 > 0:47:56you're talking about minus 20, minus 30.
0:47:56 > 0:47:58But, if you want it colder than that,
0:47:58 > 0:48:01if you want the coldest ever recorded temperature,
0:48:01 > 0:48:03you have to go to Antarctica.
0:48:05 > 0:48:08Recorded by satellite in 2010,
0:48:08 > 0:48:14the temperature hit a mind-blowing minus 94.7 degrees Celsius.
0:48:20 > 0:48:24The average temperature at the South Pole is minus 50 degrees.
0:48:33 > 0:48:37Winds have been known to reach nearly 200mph.
0:48:42 > 0:48:45Much of the land is surrounded by permanent sea ice.
0:48:47 > 0:48:51Which means the animals that live here have developed some of the most
0:48:51 > 0:48:54amazing survival strategies in the natural world.
0:49:01 > 0:49:04Harsh as it is up top, in the water,
0:49:04 > 0:49:08temperatures remain about minus 2 degrees all year round.
0:49:14 > 0:49:17This eerily beautiful world
0:49:17 > 0:49:20is where Weddell seals spend much of their lives.
0:49:34 > 0:49:38They live closer to the South Pole than any other mammal.
0:49:40 > 0:49:42Feeding on fish underneath the ice.
0:49:50 > 0:49:53Surely this is a potential problem for an air breathing mammal?
0:50:01 > 0:50:03Well, there are some natural holes,
0:50:03 > 0:50:07cracks and openings in the constantly moving sea ice.
0:50:12 > 0:50:16And that's where the seals' remarkable adaptations come in.
0:50:19 > 0:50:22They can hold their breath for over an hour,
0:50:22 > 0:50:27swimming far and wide in search of the next air hole.
0:50:36 > 0:50:39They've also developed a kind of sonar.
0:50:42 > 0:50:45Listening to the minute differences in the echoes
0:50:45 > 0:50:49from this peculiar call, they can detect gaps in the ice.
0:50:55 > 0:50:59But, most amazing of all is how they stop a hole from freezing over
0:50:59 > 0:51:01in these sub-zero temperatures.
0:51:05 > 0:51:09Weddell seals have large, strong, and protruding teeth.
0:51:13 > 0:51:16They use them to rasp away at the ice.
0:51:21 > 0:51:24It takes extraordinary effort,
0:51:24 > 0:51:27but it keeps their precious breathing holes open.
0:51:29 > 0:51:33Going to these lengths is the only way to survive
0:51:33 > 0:51:35in extreme places like this.
0:51:44 > 0:51:48Our final group of animals can face up to the elements
0:51:48 > 0:51:50like no other -
0:51:50 > 0:51:52the Antarctic penguins.
0:52:06 > 0:52:09Under their skin, penguins have a thick layer of blubber
0:52:09 > 0:52:10to keep them warm.
0:52:13 > 0:52:16And it gives them that distinctive rotund shape.
0:52:19 > 0:52:23To save time and energy, they take advantage of the ice to get about.
0:52:26 > 0:52:29Even their waddle is energy efficient.
0:52:34 > 0:52:40And, on top of all of this is their most fortifying of features -
0:52:40 > 0:52:41feathers.
0:52:43 > 0:52:47Penguins may not be able to fly, but they do have a lot of feathers,
0:52:47 > 0:52:50and it's thought that penguins have more insulating feathers
0:52:50 > 0:52:54than any other bird, and I've got some here.
0:52:54 > 0:52:55Just look at them.
0:52:55 > 0:52:58These are from an emperor penguin,
0:52:58 > 0:53:03a species that has to endure bitterly cold Antarctic conditions,
0:53:03 > 0:53:05and it is a masterpiece.
0:53:05 > 0:53:09At the base, it's incredibly downy and fluffy.
0:53:09 > 0:53:13The quill part is stiff, the end is slick.
0:53:13 > 0:53:15This is the waterproof part.
0:53:15 > 0:53:19And on the bird, these feathers interlock.
0:53:19 > 0:53:22The outside is waterproof.
0:53:22 > 0:53:25It creates a waterproof seal
0:53:25 > 0:53:29and underneath is an air void, full of these downy feathers.
0:53:29 > 0:53:34This is an incredibly sophisticated form of insulation.
0:53:37 > 0:53:39When it comes to a life in the snow,
0:53:39 > 0:53:43the emperor penguin really does deserve its name.
0:53:43 > 0:53:48They're able to live further south than any other penguin.
0:53:49 > 0:53:51For three months each year,
0:53:51 > 0:53:55the males remain out on the ice whilst their partners go fishing.
0:53:58 > 0:54:01They face temperatures of minus 50
0:54:01 > 0:54:05and winds that can exceed 100mph,
0:54:05 > 0:54:09all to achieve one extraordinary thing.
0:54:14 > 0:54:18In a place with no shelter, no materials to build a nest,
0:54:18 > 0:54:21and where everything is frozen solid,
0:54:21 > 0:54:25he is responsible for bringing up the next generation.
0:54:27 > 0:54:32Balanced on his feet, the closest part of his body to the ice,
0:54:32 > 0:54:36he's protecting his most precious possession,
0:54:36 > 0:54:38an egg.
0:54:41 > 0:54:44In a specially adapted pouch,
0:54:44 > 0:54:47the egg is kept at 38 degrees above freezing.
0:54:52 > 0:54:56But it's not just about keeping his egg warm and off the frozen ground.
0:54:58 > 0:55:01To survive, the penguins must stick together.
0:55:05 > 0:55:07They move in and out of formation
0:55:07 > 0:55:10with the other expectant fathers to keep warm.
0:55:39 > 0:55:41Then, one magical day,
0:55:41 > 0:55:47the hard work pays off, and he receives the ultimate gift.
0:55:53 > 0:55:55A brand-new baby penguin...
0:55:59 > 0:56:03..to show off proudly when Mum returns home from fishing.
0:56:17 > 0:56:20Whether a parent or a baby,
0:56:20 > 0:56:24nature's winter wonderlands are demanding places to live.
0:56:30 > 0:56:33Yet, as we've seen,
0:56:33 > 0:56:36our animals are more than up to it.
0:56:43 > 0:56:48They've come up with extraordinary ways to survive,
0:56:48 > 0:56:50and even thrive.
0:56:56 > 0:57:02For me, these animals are some of the most impressive on our planet.
0:57:02 > 0:57:05They've overcome every challenge
0:57:05 > 0:57:10to each lead a remarkable life in the snow.