0:00:02 > 0:00:05To us, winter can appear magical.
0:00:05 > 0:00:07The way the snow transforms the landscape
0:00:07 > 0:00:09is little short of miraculous.
0:00:11 > 0:00:13But for the animals who have to live through it,
0:00:13 > 0:00:17winter is a time of incredible challenges.
0:00:17 > 0:00:20This is the story of a small group of baby animals
0:00:20 > 0:00:25facing some of the harshest conditions on the planet.
0:00:25 > 0:00:28Polar bear cubs following their mums
0:00:28 > 0:00:30to the ends of the Earth.
0:00:30 > 0:00:33Reindeer calves trying to keep up with the herd.
0:00:36 > 0:00:40Young otters and Arctic foxes learning to fend for themselves.
0:00:42 > 0:00:44Penguin chicks racing to independence.
0:00:46 > 0:00:48And baby snow monkeys
0:00:48 > 0:00:51who must find their place in the troop to survive.
0:00:53 > 0:00:56With the help of their mums...
0:00:56 > 0:00:58dads...
0:00:58 > 0:00:59and families,
0:00:59 > 0:01:02they might just make it through their first year.
0:01:07 > 0:01:10These are the snow babies.
0:01:19 > 0:01:22Antarctica is the coldest place on Earth.
0:01:23 > 0:01:25In winter, there's little daylight
0:01:25 > 0:01:30and the temperature may fall to minus 80 degrees centigrade.
0:01:32 > 0:01:35But for one remarkable animal, this is home.
0:01:37 > 0:01:39The emperor penguin.
0:01:51 > 0:01:53Winter fades.
0:02:13 > 0:02:16Spring isn't the only new arrival.
0:02:19 > 0:02:23He may be tiny, but he has a huge adventure ahead of him.
0:02:24 > 0:02:27If he's to survive his first winter,
0:02:27 > 0:02:30he must learn to stand on his own two feet by then.
0:02:32 > 0:02:34For the moment, though,
0:02:34 > 0:02:36he relies completely on his parents.
0:02:37 > 0:02:40Or, more precisely, his dad.
0:02:41 > 0:02:44This little chap has never met his mum.
0:02:44 > 0:02:48Two months before he hatched, in the darkest days of winter,
0:02:48 > 0:02:53she set off to get fish for her and her unborn chick.
0:02:54 > 0:02:58But right now it's 80 kilometres to the water's edge
0:02:58 > 0:03:00and she has a long journey home.
0:03:04 > 0:03:08Dad has fed his son what he can, and has little left to offer.
0:03:11 > 0:03:13He needs a proper meal...
0:03:13 > 0:03:15and soon.
0:03:21 > 0:03:23So does Dad.
0:03:23 > 0:03:26He hasn't eaten for over 100 days,
0:03:26 > 0:03:28and weighs half what he used to.
0:03:34 > 0:03:37But he can't leave until Mum comes back.
0:03:37 > 0:03:40All they can do is wait...
0:03:40 > 0:03:43and hope that nothing has happened to her.
0:03:53 > 0:03:56At last, a sight for sore eyes.
0:04:00 > 0:04:03It's the mums, returning with fish and squid
0:04:03 > 0:04:06for chicks they've never even set eyes on.
0:04:08 > 0:04:11HONKING
0:04:11 > 0:04:13It's a warm welcome home.
0:04:20 > 0:04:24But with 20,000 penguins all calling out at once,
0:04:24 > 0:04:27how will the mums ever find their own families?
0:04:29 > 0:04:32Incredibly, even in the uproar,
0:04:32 > 0:04:35penguins can recognise the calls of their partners.
0:04:39 > 0:04:41She's found them.
0:04:41 > 0:04:43Reunited at last.
0:04:47 > 0:04:50After two months apart,
0:04:50 > 0:04:53the adults spend a tender moment together.
0:05:03 > 0:05:08The chick has never seen his mum before, and is a little shy.
0:05:09 > 0:05:13For Mum, it's love at first sight.
0:05:23 > 0:05:26After months of it being just the two of them,
0:05:26 > 0:05:29it's hard for Dad to let go.
0:05:40 > 0:05:44It takes a lot of gentle persuasion...
0:05:44 > 0:05:46but he's finally ready.
0:05:50 > 0:05:53The chick has only a thin down to keep him warm.
0:05:53 > 0:05:58Just two minutes on the ice would be enough to kill him.
0:05:58 > 0:06:00They have to move fast.
0:06:03 > 0:06:04Mission accomplished.
0:06:09 > 0:06:12The young chick gets his first full meal,
0:06:12 > 0:06:14Mum gets time with her baby,
0:06:14 > 0:06:17and Dad can finally go fishing.
0:06:18 > 0:06:21Just 80 kilometres to go.
0:06:34 > 0:06:36At the other end of the world,
0:06:36 > 0:06:38in the high Arctic,
0:06:38 > 0:06:41winter is equally harsh.
0:06:43 > 0:06:45It engulfs the world like a ghost.
0:06:48 > 0:06:50It whips the land without mercy.
0:06:54 > 0:06:57But, again, it doesn't last for ever.
0:07:02 > 0:07:04Spring reveals new life.
0:07:12 > 0:07:15This polar bear cub was born two months ago
0:07:15 > 0:07:18and has only just come out of her den beneath the snow.
0:07:22 > 0:07:24Mum has been feeding her on rich, fatty milk,
0:07:24 > 0:07:28but hasn't had anything to eat herself for almost eight months.
0:07:36 > 0:07:39She needs to get them moving,
0:07:39 > 0:07:42just as soon as she's sure Baby can keep up.
0:07:53 > 0:07:56If she's to make it through her first year,
0:07:56 > 0:07:59the cub will have to be continually on the move.
0:07:59 > 0:08:04It's the only way to survive in a place where food is hard to come by.
0:08:06 > 0:08:08Mum makes it look easy.
0:08:12 > 0:08:14Baby's not so sure...
0:08:31 > 0:08:33..and needs some gentle reassurance.
0:08:34 > 0:08:36GENTLE RYTHMIC CALLING
0:08:39 > 0:08:42But if they're to catch any seals
0:08:42 > 0:08:45they'll need to get onto the sea ice before it starts to melt.
0:08:47 > 0:08:49And the sooner, the better.
0:08:50 > 0:08:53They've got a lot of travelling to do.
0:09:01 > 0:09:05Further south, the snow is still thick on the ground.
0:09:09 > 0:09:11The nights are still long,
0:09:11 > 0:09:14and the temperature well below freezing.
0:09:24 > 0:09:27This shivering little reindeer has only just been born...
0:09:29 > 0:09:32..yet she has only a few hours to find her feet
0:09:32 > 0:09:33and join the rest of the herd.
0:09:46 > 0:09:49The reindeer, or caribou,
0:09:49 > 0:09:52are on the longest overland migration of any mammal,
0:09:52 > 0:09:56searching for tender new grass revealed by the melting snow.
0:09:58 > 0:10:02But new-born calves are an easy target for hungry wolves.
0:10:07 > 0:10:09Shadowed as they go,
0:10:09 > 0:10:12these reindeer may walk more than 4,000 kilometres in a year
0:10:12 > 0:10:16and the calves will have to keep up to survive.
0:10:24 > 0:10:28But even animals born to run must take a break some time.
0:10:38 > 0:10:42When reindeer calves play, they aren't just having fun -
0:10:42 > 0:10:44they're getting fit and agile
0:10:44 > 0:10:47practising the defensive moves they'll need to survive.
0:10:47 > 0:10:50And not a moment too soon.
0:10:53 > 0:10:56A white-tailed eagle has got them in its sights.
0:10:57 > 0:11:00These enormous birds can easily kill a young calf.
0:11:06 > 0:11:10A small group of mums and calves have strayed away from the herd.
0:11:12 > 0:11:13A miss.
0:11:20 > 0:11:21But the eagle isn't giving up.
0:11:25 > 0:11:26A strike.
0:11:26 > 0:11:28The eagle succeeds.
0:11:34 > 0:11:37It's a harsh lesson for the surviving calves,
0:11:37 > 0:11:39but they must stay with the herd.
0:11:41 > 0:11:45With one calf less, the herd continues north,
0:11:45 > 0:11:47chasing the melting snow.
0:12:01 > 0:12:04The thaw is also a busy time for adult Arctic foxes.
0:12:06 > 0:12:10Spring brings new mouths to feed.
0:12:19 > 0:12:21By the time winter comes around,
0:12:21 > 0:12:25these cubs must be all grown up and completely independent
0:12:25 > 0:12:28so they have a lot of learning to do.
0:12:28 > 0:12:32And, as we all know, youngsters learn faster when it's fun.
0:12:41 > 0:12:45The cubs are still too young to hunt for themselves,
0:12:45 > 0:12:48but they've seen their parents catching rodents under the snow
0:12:48 > 0:12:50and are already honing their skills.
0:13:03 > 0:13:05It's Mum.
0:13:09 > 0:13:11But she's come back without any food.
0:13:14 > 0:13:18It's still early in the year and there's little for her to catch.
0:13:21 > 0:13:23Mum isn't about to give up, though.
0:13:23 > 0:13:26She heads back out to try again.
0:13:26 > 0:13:29Until they can hunt and scavenge for themselves,
0:13:29 > 0:13:32all the cubs can do is wait and hope.
0:13:42 > 0:13:46In the polar regions, winters are long and harsh
0:13:46 > 0:13:49and spring is slow to arrive.
0:13:59 > 0:14:02The same is true here, in the mountains of Japan,
0:14:02 > 0:14:05where winter is a brutal affair.
0:14:08 > 0:14:11There is little greenery and few plants to eat.
0:14:14 > 0:14:17But when spring finally comes,
0:14:17 > 0:14:19life returns quickly.
0:14:23 > 0:14:26A troop of macaques makes the most of the sunshine.
0:14:33 > 0:14:36It's the perfect time to welcome a new addition to the family.
0:14:44 > 0:14:45It's a baby boy.
0:14:47 > 0:14:51This tiny monkey will need all the warmth, protection and milk
0:14:51 > 0:14:53his devoted mum can offer.
0:15:10 > 0:15:12Surrounded by greenery,
0:15:12 > 0:15:15it's hard to believe that Japanese macaques
0:15:15 > 0:15:17are also known as snow monkeys.
0:15:17 > 0:15:19Yet, in only six months' time,
0:15:19 > 0:15:22this baby monkey will be in a world of white.
0:15:24 > 0:15:26If he's to make it through his first winter,
0:15:26 > 0:15:29he too has a lot of learning to do.
0:15:30 > 0:15:33Not just about feeding himself,
0:15:33 > 0:15:35but also about fitting in.
0:15:36 > 0:15:40Snow monkey troops have a very strict pecking order.
0:15:41 > 0:15:43A queen-like female rules the roost.
0:15:46 > 0:15:49Below her, a whole cast of class-conscious males
0:15:49 > 0:15:52decides who gets into the gang...
0:15:56 > 0:15:58..and who doesn't.
0:16:08 > 0:16:11Probably best just to stick with Mum.
0:16:16 > 0:16:20Polar bear cubs must also stay close to their mums.
0:16:24 > 0:16:27It's the only way a cub is ever going to learn how to hunt.
0:16:31 > 0:16:35Ringed seals make their dens in the sea ice.
0:16:35 > 0:16:40But polar bears have the best sense of smell of any mammal.
0:16:43 > 0:16:45Unfortunately for her,
0:16:45 > 0:16:49ringed seals flee at the first hint of danger.
0:16:54 > 0:16:59Only 2% of polar bear hunts are successful,
0:16:59 > 0:17:02so Mum will just have to keep trying.
0:17:02 > 0:17:06At least, Baby has seen how it's done,
0:17:06 > 0:17:09though she might need a little more practice.
0:17:23 > 0:17:25Mum's not giving up.
0:17:25 > 0:17:27Seals make their dens in the ice,
0:17:27 > 0:17:30so the rising temperatures mean that they will soon be gone.
0:17:35 > 0:17:38Despite her growing hunger,
0:17:38 > 0:17:41Mum still makes time to play with her baby.
0:17:42 > 0:17:44But the clock is ticking.
0:17:46 > 0:17:50As the sea ice gradually melts, the seals will head out to sea.
0:17:51 > 0:17:54They have to keep moving, searching for their prey.
0:18:00 > 0:18:02The cub keeps up as best she can,
0:18:02 > 0:18:07but polar bears might walk as much 55 kilometres in a day
0:18:07 > 0:18:11and that's tough on a cub's tender little paws.
0:18:20 > 0:18:23The cub takes a rest to soothe them.
0:18:29 > 0:18:31But there's no time to waste.
0:18:36 > 0:18:38It's time to get moving again.
0:18:44 > 0:18:48In the Antarctic, spring is slower to take hold.
0:18:52 > 0:18:55But the penguin chicks are growing fast.
0:18:57 > 0:19:00And no wonder - in four months' time,
0:19:00 > 0:19:03this chick will be heading off to the open ocean.
0:19:04 > 0:19:07In the meantime, there's some local exploring to do.
0:19:16 > 0:19:20As far as Mum's concerned, a little independence is no bad thing.
0:19:23 > 0:19:26Still, better follow him, just in case.
0:19:34 > 0:19:36At the first sign of mischief,
0:19:36 > 0:19:38he's dragged back by the scruff of the neck.
0:19:42 > 0:19:45But this little chap has a will of his own.
0:19:59 > 0:20:01In the beginning, it's brilliant.
0:20:02 > 0:20:07It's his first slice of freedom, and it tastes great.
0:20:14 > 0:20:19The trouble is that he's in a colony of 80,000 penguins.
0:20:21 > 0:20:23Everyone looks pretty much the same.
0:20:28 > 0:20:31The result is inevitable.
0:20:34 > 0:20:36He's completely lost.
0:20:42 > 0:20:44It's the moment every toddler dreads.
0:20:59 > 0:21:02All he wants is to find his mum.
0:21:06 > 0:21:09But this mum belongs to someone else.
0:21:26 > 0:21:28Oh, dear.
0:21:28 > 0:21:32Some of the other females have lost their babies,
0:21:32 > 0:21:35and their maternal instincts are so overwhelming
0:21:35 > 0:21:38they'll steal any stray baby they see.
0:21:39 > 0:21:42Suddenly, he's running for his life.
0:21:44 > 0:21:47It's chaos and very frightening.
0:22:06 > 0:22:08He's on his last legs...
0:22:11 > 0:22:13..when Mum comes to the rescue.
0:22:19 > 0:22:22The chick has learned his lesson about leaving his mother's side.
0:22:29 > 0:22:33Though he might have preferred a slightly more dignified exit.
0:22:54 > 0:22:58In the mountains of Japan, baby snow monkeys are still busy
0:22:58 > 0:23:00trying to find their place in the pecking order.
0:23:04 > 0:23:07Being the youngest in the troop can be tough
0:23:07 > 0:23:10when all the older kids have already worked out who their mates are.
0:23:16 > 0:23:19But if this monkey doesn't make friends,
0:23:19 > 0:23:22he could be in real trouble when winter comes round.
0:23:23 > 0:23:25An older baby comes over to investigate...
0:23:32 > 0:23:34..and a friendship begins.
0:23:47 > 0:23:50Soon, everyone wants to say hi.
0:23:50 > 0:23:53It's official - he's part of the gang.
0:24:06 > 0:24:09Yellowstone in the Rocky Mountains of North America.
0:24:12 > 0:24:16In winter, this volcanic area is thick with snow,
0:24:16 > 0:24:20and temperatures can easily reach 40 degrees below zero.
0:24:21 > 0:24:24As winter ends, the white melts away...
0:24:27 > 0:24:29..and the green takes over.
0:24:31 > 0:24:32It's late spring,
0:24:32 > 0:24:36and a family of otters emerge from their holt for the very first time.
0:24:38 > 0:24:41Being born later in the year
0:24:41 > 0:24:44means that the pups avoid the worst of the cold weather.
0:24:45 > 0:24:49It's a great strategy for keeping the new-borns from freezing
0:24:49 > 0:24:52but it means they have less time to pile on the fat
0:24:52 > 0:24:54before their first winter comes around.
0:24:55 > 0:24:57They've timed it perfectly.
0:24:59 > 0:25:02Around here, otters survive mainly on a diet of fish,
0:25:02 > 0:25:06and the local trout have just arrived to lay their eggs.
0:25:08 > 0:25:10The pups must learn how to hunt, of course.
0:25:10 > 0:25:14But on the first day of school, maybe just a demonstration will do.
0:25:27 > 0:25:30Their mum is an excellent teacher.
0:25:36 > 0:25:39The fish are full of tiny eggs -
0:25:39 > 0:25:41perfect for little mouths.
0:25:42 > 0:25:44As long as the food keeps coming,
0:25:44 > 0:25:47they should be in good shape for winter.
0:25:54 > 0:25:57Back in the realm of the polar bears,
0:25:57 > 0:26:01the Arctic sea ice now shimmers with late spring heat haze.
0:26:03 > 0:26:07This mother and her cub have had a good couple of months
0:26:07 > 0:26:09hunting seals on the frozen sea.
0:26:09 > 0:26:14The problem is the surface of the ice is beginning to melt.
0:26:25 > 0:26:29Polar bear cubs have tiny bristles on their paws
0:26:29 > 0:26:31that help to stop them slipping,
0:26:31 > 0:26:34but it's no match for the melting ice.
0:26:37 > 0:26:40Beneath the ice, the seal pups are growing up
0:26:40 > 0:26:42and heading out to the open ocean,
0:26:42 > 0:26:46and catching them is proving increasingly difficult.
0:26:49 > 0:26:53The bears follow the seals out to sea, on thinner and thinner ice,
0:26:53 > 0:26:58knowing that this might be their last chance of a meal
0:26:58 > 0:26:59for many months to come.
0:27:06 > 0:27:09In Antarctica, it stays colder for longer.
0:27:17 > 0:27:19Unlike the polar bear cub,
0:27:19 > 0:27:23this penguin chick doesn't have to travel to get his food.
0:27:23 > 0:27:25Mum and Dad do all the work.
0:27:26 > 0:27:30He's now old enough to be left alone while his parents go fishing.
0:27:32 > 0:27:34Plus, he's made a lot of friends.
0:27:36 > 0:27:39And he and his mates look out for each other...
0:27:41 > 0:27:43..most of the time.
0:27:45 > 0:27:47There's the odd disagreement, of course.
0:27:49 > 0:27:51Though it's usually quickly forgotten.
0:27:59 > 0:28:02Mum and Dad are now both working full-time
0:28:02 > 0:28:04just to keep their baby fed.
0:28:06 > 0:28:09Even with the ice melting and the sea getting closer,
0:28:09 > 0:28:13it's still a two-week round trip to catch food.
0:28:16 > 0:28:18The adults have no choice.
0:28:18 > 0:28:21Their chicks have some serious growing to do
0:28:21 > 0:28:24if they're to leave home before next winter.
0:28:31 > 0:28:35But, even in summer, the weather can turn in an instant.
0:28:36 > 0:28:39In an Antarctic blizzard,
0:28:39 > 0:28:43temperatures can quickly fall to minus 55 degrees Centigrade.
0:28:45 > 0:28:49The chicks' only chance of survival is to huddle together for warmth.
0:28:51 > 0:28:54The cold, though, is only part of the problem.
0:28:55 > 0:28:58They've lost the rest of the colony.
0:29:03 > 0:29:04They have two choices.
0:29:05 > 0:29:09They can stay together and hope that they are found,
0:29:09 > 0:29:13or they can break the huddle, search for the remaining adults,
0:29:13 > 0:29:15and risk freezing to death.
0:29:17 > 0:29:21Young and afraid, they decide to risk it.
0:29:25 > 0:29:28But they could be heading in completely the wrong direction.
0:29:54 > 0:29:57In the end, luck is on their side.
0:29:58 > 0:30:00Even at the height of the blizzard,
0:30:00 > 0:30:04there's still a column of adults bringing fish back from the sea.
0:30:05 > 0:30:08The chicks are led home like a party of lost schoolchildren.
0:30:37 > 0:30:40Back with the colony, they form a creche once more.
0:30:44 > 0:30:46But nothing beats snuggling up to Mum.
0:30:52 > 0:30:55Hanging out with your mates is all very well
0:30:55 > 0:30:57but mums are definitely better.
0:31:14 > 0:31:17In the Arctic, there's little snow left,
0:31:17 > 0:31:20as over 75,000 reindeer soldier on,
0:31:20 > 0:31:23covering up to 50 kilometres a day.
0:32:13 > 0:32:16This is boom time for the reindeer.
0:32:17 > 0:32:21The little calves are feeding for themselves now.
0:32:21 > 0:32:24Though they'll still drink mum's milk when they get a chance.
0:32:29 > 0:32:31With coats designed for the cold,
0:32:31 > 0:32:33overheating can be a problem for the reindeer.
0:32:34 > 0:32:36True arctic animals,
0:32:36 > 0:32:39they seek out the last patches of snow to keep cool.
0:32:40 > 0:32:45And then they're off once more, always in search of new pastures.
0:32:47 > 0:32:49But danger is never far away.
0:32:51 > 0:32:53The wolves have decided to strike.
0:32:55 > 0:32:58HOWLING
0:33:00 > 0:33:01Their strategy is fear.
0:33:03 > 0:33:04Panic the reindeer,
0:33:04 > 0:33:08and the calves will fall behind or get separated from the herd.
0:33:10 > 0:33:13In the chaos, anxious mums call desperately for their babies.
0:33:13 > 0:33:15RYTHMIC BAYING
0:33:23 > 0:33:25Most of the calves are lucky.
0:33:25 > 0:33:28This one was separated but survived.
0:33:29 > 0:33:31Now she just needs to find Mum.
0:33:34 > 0:33:36But while there may be safety in numbers,
0:33:36 > 0:33:38it's also easier to get lost.
0:33:43 > 0:33:46THEY CALL TO EACH OTHER
0:33:51 > 0:33:55Found at last, and desperate for Mum's reassurance.
0:33:56 > 0:33:59Others may not have been so fortunate.
0:34:00 > 0:34:04But at least this little one is safe and back with the herd.
0:34:10 > 0:34:14At the peak of the Arctic summer, the sun never sets.
0:34:24 > 0:34:26This constant warmth and energy
0:34:26 > 0:34:29triggers an incredible burst of life.
0:34:30 > 0:34:35Millions of seabirds flock to the cold, rich seas now freed from ice.
0:34:39 > 0:34:42Humpback whales arrive for a spectacular feast
0:34:42 > 0:34:43of shrimp-like krill.
0:35:03 > 0:35:07The fox cubs get their share of the feast - an adult seabird.
0:35:11 > 0:35:14They're already displaying signs of independence, fighting over food.
0:35:16 > 0:35:19As adults, they will live largely alone,
0:35:19 > 0:35:22and it's quickly becoming every pup for himself.
0:35:27 > 0:35:30High above them, guillemots race to feed their hungry chicks
0:35:30 > 0:35:32while summer lasts.
0:35:33 > 0:35:36Only three weeks old, it's time for the young birds
0:35:36 > 0:35:38to take their first flight into the unknown.
0:35:41 > 0:35:45And they only get one shot to reach the safety of the sea,
0:35:45 > 0:35:47with mum following anxiously behind.
0:36:05 > 0:36:08For many, it's a perfect - if bumpy - landing.
0:36:11 > 0:36:13But not all of them succeed.
0:36:26 > 0:36:30A botched first flight delivers easy pickings for a mother fox.
0:36:32 > 0:36:36Wily Mum stores her catch for harder times ahead.
0:36:37 > 0:36:40In the Arctic, it pays to be prepared.
0:36:57 > 0:37:01The summer thaw in the Antarctic has melted much of the ice...
0:37:04 > 0:37:08..and this penguin colony is now on the verge of being washed away.
0:37:14 > 0:37:16It's make or break time for the chicks.
0:37:17 > 0:37:21They've started growing their waterproof adult feathers
0:37:21 > 0:37:23and their parents have stopped feeding them.
0:37:24 > 0:37:29It's time to take to the water, whether they like it or not.
0:37:38 > 0:37:41Eventually, after much hesitation,
0:37:41 > 0:37:44they summon their courage and take the plunge.
0:37:51 > 0:37:53Swimming is a wonderful discovery.
0:38:07 > 0:38:10At last, they're almost the same size as the adults...
0:38:12 > 0:38:15..and a perfect meal for a leopard seal.
0:38:16 > 0:38:20Having barely wet their beaks, they shoot back on to the ice.
0:38:47 > 0:38:51It's been a harsh introduction to the reality of life at sea.
0:38:58 > 0:39:02But they can't stay here for ever - they have to start fishing.
0:39:02 > 0:39:04It's time for another deep breath.
0:39:12 > 0:39:17This time, they swim straight out to the open ocean
0:39:17 > 0:39:19and off to independence.
0:39:24 > 0:39:28High summer in the Arctic and there's little ice left.
0:39:32 > 0:39:36It's the hardest time of year for hungry polar bears.
0:39:36 > 0:39:40There are still a few seals, but not enough ice to hunt them on.
0:39:41 > 0:39:43There's only one thing for it.
0:39:53 > 0:39:56Polar bears are superb swimmers
0:39:56 > 0:40:00and can easily swim 55 kilometres a day.
0:40:05 > 0:40:09Mum is perfectly at home under water.
0:40:09 > 0:40:12but seals can swim faster and deeper.
0:40:21 > 0:40:25It's time to admit defeat and head for dry land.
0:40:34 > 0:40:37Eventually the days close in.
0:40:37 > 0:40:39Summer slowly fades.
0:40:43 > 0:40:46A chill comes to the mountains of Japan.
0:40:55 > 0:40:59Mothers and babies must cuddle together for warmth.
0:41:04 > 0:41:06Autumn is finally here.
0:41:08 > 0:41:10THUNDER
0:41:19 > 0:41:22As they make the most of the dwindling grass,
0:41:22 > 0:41:25the reindeer calves also grow thicker coats.
0:41:27 > 0:41:30The fox cubs' coats are not just getting thicker,
0:41:30 > 0:41:34they're also getting paler to match the coming snow.
0:41:35 > 0:41:40They'll be leaving home soon to face their first winter alone.
0:41:41 > 0:41:46As a result, their play is much more like real hunting now.
0:41:47 > 0:41:51And playing with their food is positively encouraged.
0:41:58 > 0:42:00When you're having fun,
0:42:00 > 0:42:04it's easy to think that the good times will last for ever.
0:42:11 > 0:42:14But there's no mistaking the change in the air.
0:42:20 > 0:42:25Further north, these polar bears have swum back to shore.
0:42:27 > 0:42:31Until the sea freezes over again, there's little for them to eat.
0:42:33 > 0:42:35What is Mum up to?
0:42:36 > 0:42:39Actually, desperation is setting in.
0:42:41 > 0:42:42She must forage for what she can.
0:42:46 > 0:42:49A bit of seaweed hardly helps with the hunger.
0:42:49 > 0:42:52It's more like a vitamin supplement than a meal,
0:42:52 > 0:42:54but it's better than nothing.
0:43:04 > 0:43:07While Mum hunts in the water,
0:43:07 > 0:43:10baby grabs the chance to hunt on land.
0:43:21 > 0:43:23Just a little bit more practice.
0:43:30 > 0:43:33Her baby is still getting milk
0:43:33 > 0:43:37but it's been months since Mum last ate a proper meal.
0:43:38 > 0:43:42And these bones from a beached whale were picked clean years ago.
0:43:44 > 0:43:45All they can do
0:43:45 > 0:43:49is wait for the sea to freeze over.
0:43:57 > 0:44:00When winter comes, it makes a dramatic entrance...
0:44:03 > 0:44:04..arriving with a force
0:44:04 > 0:44:07that the snow babies have never experienced before.
0:44:26 > 0:44:30The youngsters have learned all they can.
0:44:30 > 0:44:32For most of them,
0:44:32 > 0:44:35it's time to face the greatest challenge of their lives.
0:44:37 > 0:44:40With the change in season, the reindeer turn south.
0:44:44 > 0:44:491,500 freezing kilometres now separate the calves
0:44:49 > 0:44:51from the lush southern pastures.
0:45:04 > 0:45:07At last, the first shock is over.
0:45:10 > 0:45:13The world is transformed.
0:45:34 > 0:45:39In Japan, this year's babies are seeing snow for the first time.
0:45:41 > 0:45:43At first, they're just curious.
0:45:44 > 0:45:46Then they get creative.
0:45:51 > 0:45:53Snow monkeys are quick learners,
0:45:53 > 0:45:55and this young monkey has found
0:45:55 > 0:45:57a wonderful way of entertaining himself.
0:46:01 > 0:46:03Making snowballs.
0:46:12 > 0:46:17The only problem is it keeps rolling away.
0:46:26 > 0:46:28Or maybe that's the point.
0:46:28 > 0:46:32After all, why else would he take it to the top of the hill again?
0:46:41 > 0:46:44For this particular troop of macaques,
0:46:44 > 0:46:48making snowballs has become part of their unique culture.
0:46:48 > 0:46:50By copying the others,
0:46:50 > 0:46:54this little monkey is doing his best to stay part of the gang.
0:47:14 > 0:47:18When you're young, snow is fun and extremely exciting.
0:47:21 > 0:47:24But the sense of fun doesn't always last.
0:47:28 > 0:47:32Snow monkeys are the most northerly monkeys on earth
0:47:32 > 0:47:35and face winter temperatures that are well below freezing.
0:47:38 > 0:47:40There's nowhere to shelter...
0:47:41 > 0:47:44..and food is hard to come by.
0:47:55 > 0:47:59But snow monkeys are nothing if not resourceful.
0:48:02 > 0:48:07They'll eat berries, leaves, fruit, nuts and insects.
0:48:10 > 0:48:12And, when there's no food on the ground,
0:48:12 > 0:48:14they'll try the water.
0:48:16 > 0:48:19And that includes the babies.
0:48:23 > 0:48:26Small crustaceans are hiding under the rocks,
0:48:26 > 0:48:32and this baby snow monkey has been taught by his mum how to find them.
0:48:33 > 0:48:37It's fiddly work and the water is freezing...
0:48:39 > 0:48:41..but beggars can't be choosers.
0:48:47 > 0:48:49With their thick coats,
0:48:49 > 0:48:52adult snow monkeys are well equipped to deal with the wind and the snow.
0:48:55 > 0:48:57The babies aren't so lucky.
0:48:59 > 0:49:04Without some respite, this baby could be in real trouble.
0:49:17 > 0:49:20Back in the Rockies, the otter family have no such problems.
0:49:33 > 0:49:37Thanks to hot volcanic springs, there are gaps in the ice
0:49:37 > 0:49:39which make excellent fishing holes.
0:49:47 > 0:49:48But they're not alone.
0:49:49 > 0:49:52A hungry coyote is on the prowl.
0:49:56 > 0:50:00Coyotes will happily kill and eat an otter pup if given half a chance.
0:50:02 > 0:50:05But this one seems to have other things on his mind.
0:50:08 > 0:50:10With his incredible sense of smell,
0:50:10 > 0:50:13the coyote sniffs out the otters' larder.
0:50:17 > 0:50:19Unlucky.
0:50:20 > 0:50:23Watched by the increasingly frustrated otters,
0:50:23 > 0:50:24he tries again.
0:50:37 > 0:50:39This time he's in luck.
0:50:40 > 0:50:43It's a huge Yellowstone cutthroat trout,
0:50:43 > 0:50:45fresh out of the otters' freezer.
0:50:47 > 0:50:51Still, better that he takes a fish than a pup.
0:51:04 > 0:51:08As winter deepens, even the sea freezes.
0:51:15 > 0:51:18The surface turns to icy slush.
0:51:27 > 0:51:31Gradually, the ice merges into flat plates.
0:51:36 > 0:51:39Eventually, after much toing and froing,
0:51:39 > 0:51:41the plates lock together...
0:51:45 > 0:51:48..and the sea becomes land again.
0:51:53 > 0:51:59At last, the Arctic is just how polar bears like it.
0:52:03 > 0:52:06They are back on solid ice,
0:52:06 > 0:52:09and seals are back at the top of the menu.
0:52:13 > 0:52:15Hunting day and night,
0:52:15 > 0:52:18this mum has been making up for lost time.
0:52:19 > 0:52:21Ringed seals are abundant
0:52:21 > 0:52:24and the ice is no longer melting underfoot.
0:52:30 > 0:52:33Mum is having a field day,
0:52:33 > 0:52:35and so too is her little cub.
0:52:40 > 0:52:43With their bellies full, they take a well-earned rest.
0:52:43 > 0:52:46It's four degrees below...
0:52:47 > 0:52:49..and just how they like it.
0:52:54 > 0:52:57And what about the fox cubs?
0:52:57 > 0:52:59They're all grown up and living on their own now.
0:53:01 > 0:53:06Their winter coat gives them the best insulation of any mammal
0:53:06 > 0:53:08and excellent camouflage in the snow.
0:53:10 > 0:53:16This cub is now a master at hunting rodents scurrying beneath the snow.
0:53:17 > 0:53:20But some of the best food is served frozen.
0:53:21 > 0:53:24Whether killed by illness, or by the cold,
0:53:24 > 0:53:28this adult reindeer will keep for a long, long time.
0:53:29 > 0:53:32The cub's mum and dad would be proud of him.
0:53:37 > 0:53:41The reindeer calves are also independent of their mums.
0:53:41 > 0:53:45Heading south, they are keeping one step ahead of the weather...
0:53:46 > 0:53:49..ensuring the snow is still shallow enough to move through
0:53:49 > 0:53:51and find food in.
0:54:01 > 0:54:04Arctic wolves may still be shadowing them
0:54:04 > 0:54:07but the calves are bigger and faster now
0:54:07 > 0:54:09and no longer easy prey.
0:54:17 > 0:54:21The young reindeer still have an epic journey ahead of them,
0:54:21 > 0:54:24but the future is definitely looking brighter.
0:54:27 > 0:54:31But the reindeer aren't the only ones on an epic journey.
0:54:35 > 0:54:38Having left the ice at the height of the summer,
0:54:38 > 0:54:41they've journeyed well beyond the Antarctic Circle.
0:54:43 > 0:54:45At over a metre long,
0:54:45 > 0:54:49the young penguins are now the same size as their parents,
0:54:49 > 0:54:53and they can dive to depths of over 500 metres on a single breath.
0:54:58 > 0:55:02They are, at last, the essence of freedom.
0:55:09 > 0:55:13High in the Rocky Mountains, the otter family are staying put.
0:55:15 > 0:55:17They have a plentiful supply of fish
0:55:17 > 0:55:22and will stay together all winter, looking after each other.
0:55:23 > 0:55:26Having mastered the art of survival,
0:55:26 > 0:55:29they can now afford to play.
0:55:48 > 0:55:52Why run when you can toboggan?
0:56:00 > 0:56:04But life doesn't look quite so easy for the Japanese macaques.
0:56:06 > 0:56:08In their volcanic mountains,
0:56:08 > 0:56:11the snow monkeys are living up to their name.
0:56:14 > 0:56:18The weather has taken a turn for the worse.
0:56:19 > 0:56:22But they have a secret.
0:56:29 > 0:56:34Heated by the volcano, it's an enormous hot tub.
0:56:37 > 0:56:41For a little monkey, it doesn't get better than this.
0:56:42 > 0:56:45Surrounded by family and friends,
0:56:45 > 0:56:47all his efforts to get in with the rest of the troop
0:56:47 > 0:56:50have finally paid off.
0:56:50 > 0:56:52He hasn't been left out in the cold.
0:57:04 > 0:57:08But there's someone who deserves some special attention.
0:57:09 > 0:57:13She's seen him through the toughest times.
0:57:13 > 0:57:18She's nursed him, protected him, and taught him everything he knows.
0:57:20 > 0:57:23Because of her, his future is looking good.
0:57:27 > 0:57:28Thanks, Mum.
0:57:47 > 0:57:50Thanks to everything they've learned along the way,
0:57:50 > 0:57:53all our snow babies have made it through
0:57:53 > 0:57:55the most difficult time of their young lives...
0:57:57 > 0:58:01..with a little help from family and friends.
0:58:32 > 0:58:36Subtitles by Red Bee Media Ltd