The Life of a Baby Polar Bear - Ep. 4 | Wildlife: The Big Freeze

• [Narrator] Before becoming the biggest land predator on the planet, polar bears are born small and helpless. They must then embark on an odyssey to grow more than 100 times their weight. And learn everything they need to survive before their mother abandons them at two and a half years old. Less than 50% will survive. I think our little bear has got a problem here. Run, run, run. The Arctic is no place for cute.

At first glance, the Arctic feels brutally devoid of life. Though a select group of animals have figured out a way to thrive. But the real force here works quietly under foot. Every winter, sea ice starts small and delicate, then it grows over millions of square miles. How is it possible that this freezer holds the key to our entire planet? Like a lung, sea ice breathes life into the Arctic every year in a cycle that impacts the climate across the globe. This is the story from the edge of the Canadian Arctic, where it all starts.

My name's Bertie Gregory and I'm a National Geographic wildlife film-maker. Everything is at stake; we're all waiting for the big freeze. As winter slowly gives way to spring, on the edge of the Arctic, polar bear mothers break out of their dens. And get ready for a treacherous 40-mile trek to hunt at sea. Finding them in this massive, featureless landscape is nearly impossible unless you're this guy. Morris Spence's been combing this area for more than forty years.

Well, it looks like Morris is already onto something. It's crazy what he can pick up on, looking at little marks in the ground that I'd just drive right past.

• They could be on the edge of the lake like this, they could be anywhere.

• I can't quite believe we've found this beautiful female polar bear. I say "we found her," I had nothing to do with it. It was all down to our incredible polar bear tracker, Morris. But most importantly, between her legs, snuggled up, is a tiny, tiny little polar bear cub. And you can see it's so tightly snug in mum. And that's really key, 'cause right now it doesn't have a lot of body fat; that fur isn't that thick. So it's really gotta rely on mum to keep warm.

This cub might look small now, but with only a 60-day gestation period, polar bears are born the size of a squirrel and weigh less than two pounds inside the den. So this little one has been building his strength in preparation for the big, wild world above ground. Just imagine how exciting everything must be for that little cub. I mean, all it's ever known is a dark little snow den and then all of a sudden, mum punches out a big hole and it's got all these new smells, and sounds, and the blue sky, and trees. (gentle laughter)

• She puts up with quite a bit when they have one cub because that's all she got to play with. She has no little brother or sister to pick on, but the mother.

Polar bear litters in the Hudson Bay are getting smaller, as declining sea ice means females have less time to fatten up before entering their dens. So if this mother wants her only cub to survive, she'll need to ensure it masters the important game of recognizing which smells to trust, and which ones to run away from.

See her taking big sniffs into the air, and I'm sure part of that is smelling us, checking out what we are. But the biggest threat to these cubs are wolves. 'Cause while she can take on one wolf no problem, the problem is the wolves work as a pack, and work together, and can separate the two of them.

This mother faces a really tough decision. The more she waits, the stronger the cub will be for the trek, but the mother hasn't had a good meal in eight months, and if she waits too long, her milk is going to dry up. And there they go, off on their 40-mile trek to the sea. That little, tiny polar bear cub has the next two, two and a half years to learn everything it needs to know from its mum about how to be a polar bear.

Morris has found her day den. Pretty deep. She made this right after breaking out of her hibernation den. It's warm. To think what the actual den must be like. You know, unfortunately, it's blown in, so we can't get in it, but to be totally enclosed, straight out of the elements. You know, this snow and ice is such a good insulator, that is one of the perfect ways to conserve your energy over the winter while you're raising these little cubs.

Here's some fur. You know this is really their secret weapon against the cold. So cool. After two and a half years of being inseparable, polar bear cubs wake up to a hard truth: mum is gone. She's got to start another breeding cycle.

Well, we've caught up with this little bear and now that it's on its own, it's in the toughest year of its life. It's lost the best bouncer in the world, its mum, who would, you know, back it up through anything and also hunt for it. And now, it's got to do everything for itself, so it's got a really tough time ahead of it.

Little bear's got to be really, really resourceful. Don't know what it's got, maybe some frozen berries or something under the snow, but it's got its butt in the air, digging a little hole. It's definitely eating something; you can see its jaw chomping. It takes time to get used to this solitary life.

Lesson number one: never let your guard down. Wait, what's that smell? You've smelt this before. What is it? (wolves growling) (dramatic music) Wolves! I think our little bear's got a problem here. That bear's gotta be overheating; that coat, it's its secret weapon, but it's gotta be a curse now.

If it can just get to the water, that wolf is not going to follow. Run, run, run. Life is certainly not a playground around here. But through baptism by fire, this little cub has learned an invaluable lesson, and she's one step closer to joining the ranks of the biggest predators in the Arctic.