♪♪ NARRATOR: From the mighty grizzly bear... [ Bears growling ] ...to the endearing real-life Paddington, the spectacled bear... and the majestic polar bear, king of the frozen north... ♪♪ ...this remarkable animal family has long captured our imagination.

♪♪ To survive, they must draw on all their skills.

So whether it's raiding nature's larder... standing up to their rivals... [ Bears growling ] ...raising the cubs... or even proving that you're smarter than the average bear... ♪♪ ...today, bears face their biggest obstacles yet... as they try to get to grips with a changing world.

But whatever they're up against, bears bring curiosity, cunning, and creativity to every challenge.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ NARRATOR: Bears are some of the most charismatic creatures to walk our planet.

And they all share the same key characteristics.

Like this Alaskan brown bear.

Their impressive size and strength sets them apart.

They have forward-facing eyes with vision similar to our own.

♪♪ But their sense of smell is over a hundred times more powerful.

♪♪ Large, dexterous paws are tipped with long claws that can open up even more opportunities.

♪♪ Although they're classified as carnivores, most bears eat a diverse mix of plants, insects, and meat.

♪♪ Across the world, there are just eight species, yet they range over a wide variety of habitats -- From the ice world of the north... ♪♪ ...through the mountains of Asia... ♪♪ ...to the heat of the Tropics.

♪♪ To live in these very different places, they've had to adapt.

♪♪ The skills they need to survive must be learned and mastered over a lifetime.

So making it as a bear is far from easy.

♪♪ Katmai National Park in Alaska.

A wilderness where mountains meet the sea.

♪♪ This is home to the brown bear, also known as the grizzly.

♪♪ And they're gathering for one of the most extraordinary events in nature.

♪♪ The salmon run.

♪♪ Every summer, millions of salmon head upstream to spawn.

♪♪ Waterfalls are a natural barrier for the migrating fish.

♪♪ And the bears know it.

♪♪ ♪♪ Three cubs emerge from the forest.

Their mother is bone-thin and needs to eat.

But this is a dangerous place for a young family.

♪♪ Competition for every fish is fierce.

[ Bears growling ] ♪♪ For their own safety, the cubs are kept on the sidelines.

It's a prime position for watching the action.

Catching a powerful, slippery salmon takes practice.

♪♪ And the grizzlies, like all bears, must work out the best way to tackle their prey.

There's the "dash and grab."

♪♪ Less energetic is the "stand and wait" approach.

♪♪ But it has its downsides.

♪♪ Beneath the falls, "sit and wait" is the most successful strategy.

♪♪ Fights can break out at any moment.

[ Bears growling ] ♪♪ For now, the cubs are out of their depth.

♪♪ An experienced big male can catch 30 salmon a day.

♪♪ And, eventually, most of them have had enough.

♪♪ The mother decides it's safe enough to return.

♪♪ ♪♪ Her cubs are depending on her technique -- a combination of patience and experience.

♪♪ ♪♪ And now her family can share a meal.

♪♪ The skill and judgment needed to master a chaotic situation like this, with tricky prey and other bears, takes years to learn.

♪♪ So, for cubs, lessons start early.

The forested areas of North America are home to the grizzly's smaller cousin -- the American black bear.

It is the most numerous of the eight species.

♪♪ These cubs are just under four months old.

♪♪ Their small size makes them extremely vulnerable, so they must learn quickly to stay out of danger.

♪♪ There are predators in these forests.

♪♪ Weighing up to 12 pounds, a bald eagle could easily snatch and kill a cub.

♪♪ As could a coyote.

Most dangerous of all are grey wolves.

♪♪ But there is a place the cubs can seek safety.

♪♪ Thanks to their strong, curved claws, these cubs can climb from a very young age.

♪♪ But perfecting the technique takes time.

♪♪ They need to learn which trees are best for gripping onto.

♪♪ Smaller trees and branches are good for practice.

Well, most of the time.

♪♪ This tree is too flaky.

♪♪ This tree is too slippery.

♪♪ But this tree is just right.

♪♪ Going up is one thing.

♪♪ But coming down again can require a helping hand.

[ Cubs grunting ] All bears must learn how to avoid danger, but there's one species that's come up with an unusual strategy.

♪♪ India.

♪♪ Home to the sloth bear.

Here, there are fewer tall trees to escape into.

♪♪ And, in any case, the local predators are skilled climbers.

♪♪ So these sloth-bear cubs need a different escape plan.

♪♪ When their mother sounds the alarm, they head for the safest place around.

♪♪ Her shaggy coat allows the cubs to climb onto her back, clinging on, using strong forelegs and toes.

It's unusual for a big cat to challenge a sloth-bear mother.

Unlike her cubs, who so often do.

A mother bear is the cubs' protection... and their only guide.

♪♪ With so many skills to learn, most bear cubs stay with their mother for two to three years.

[ Bear growls ] In Alaska, a five-month-old grizzly cub is working out his boundaries.

♪♪ Adult bears spend most of their lives alone, so this time with his mother helps him learn how to interact with other bears.

♪♪ All cubs need to master their new surroundings.

♪♪ In the Arctic, young polar bears emerge from their den to take their first steps in the snow.

♪♪ This cub is more cautious.

♪♪ They need to get to grips with this terrain quickly.

♪♪ Soon they will have to walk many miles in search of food.

♪♪ In Canada, another grizzly cub is trying his luck at fishing.

♪♪ His mother demonstrates how it's done.

♪♪ Observational learning is one of the most effective ways for cubs to pick up new skills.

And with so many salmon here, he's got a good chance.

♪♪ Now, to hold onto it.

♪♪ [ Cub grunts ] [ Thunder rumbles ] As cubs grow more independent, they start trying things out for themselves.

[ Bees buzzing ] In the woodlands of Minnesota, a fallen tree holds something that bears are famously fond of.

[ Buzzing ] Honey.

[ Buzzing ] And it hasn't gone unnoticed.

This nine-month old black-bear cub may have never encountered bees before.

♪♪ And sometimes, learning can be a painful process.

[ Bear growls ] His experienced mother has a tried and tested technique.

♪♪ This "smash and grab" leads to fewer stings.

♪♪ Honeycomb provides sugars and protein from the bee larvae inside.

♪♪ Much of a cub's learning is focused on food.

As one of the biggest land animals, some bears need over 5,000 calories just on an average day.

In many parts of the world, bears have to adapt and specialize to fuel their sizeable appetites.

[ Thunder rumbles ] The Andes Mountains in South America.

Home to this continent's only bear.

White facial markings are a clue to its name -- the spectacled bear.

But to many of us, it's far more familiar as the storybook character of Paddington who came all the way from "darkest Peru."

♪♪ Like its fictional counterpart, this bear has a sweet tooth.

Although in these cloud forests, marmalade sandwiches aren't an option.

♪♪ Fortunately, there's another high-calorie food here.

Bromeliads.

A family of plants that includes the pineapple.

Perched yards off the ground, they're out of reach for most large mammals.

Bromeliads are notoriously robust plants, but the spectacled bear can break them apart with ease.

That's because, relative to its size, it has the largest jaw muscle of any bear species... and grinding teeth that are secured into its jaws with three roots instead of two.

It's after the sugar-rich core.

The spectacled bear will also eat palm nuts, birds' eggs, and small animals.

But half of its diet is made up of these high-energy plants.

The spectacled bear can satisfy its need for calories by using its strength and its ability to find and remember food sources.

But on the other side of the world, a very different habitat presents an even greater challenge.

Across Asia, many of the forests are populated by one kind of plant -- bamboo.

In China alone, bamboo forests cover an area of over 20,000 square miles.

But for an animal trying to make it here, there's just one problem.

♪♪ Bamboo is incredibly tough and fibrous... and particularly low in calories.

♪♪ So, to conquer this landscape, one bear has done something quite extraordinary.

♪♪ The giant panda has adapted its body, and even its behavior, to almost exclusively eat bamboo.

♪♪ The bear spends its days searching the Qinling Mountains for the most nutritious part of the plant.

♪♪ It usually sits down to eat... so that its flexible forepaws are free to help harvest the bamboo.

It's the only bear that has evolved a wrist bone to act as an opposable thumb, allowing it to select and manipulate the most tender part of the plant.

To prevent injury from bamboo splinters, its esophagus and stomach are lined with tough, thick walls.

But its digestive system, like those of other bears, is built for eating meat, and it lacks the plant-digesting bacteria of a true herbivore.

♪♪ So, to get enough nutrients, the panda has to munch for up to 14 hours a day, chewing its way through 26 pounds or more of bamboo.

♪♪ This low-energy diet also affects a panda's behavior.

♪♪ To avoid exhaustion, it limits unnecessary socializing and walking in tricky terrain.

♪♪ ♪♪ Bamboo is evergreen, so at least the panda can eat all year round.

♪♪ It's even come up with a method of breaking ice off frozen leaves, by using its warm snout.

♪♪ Fossil evidence suggests that pandas have been eating bamboo for the last four million years.

But their complete dependence on this one plant has put them in danger.

♪♪ Pandas once thrived across Eastern and Southern China, but due to poaching and the decline of their forests, by the 1990s, their population had crashed to just 1,000 bears.

Today their range is restricted to six isolated mountain ranges.

Over the last six decades, efforts have been made to save the panda, by giving them protection and setting up reserves.

♪♪ And in the early 1980s, China opened its first captive breeding center.

♪♪ This program has been very successful, with over 300 pandas born in captivity.

♪♪ Some of these are now being released into the wild.

♪♪ [ Indistinct conversations ] All the work to bring this bear back from the brink of extinction is starting to pay off.

Today, the wild population has nearly doubled to more than 1,800 pandas.

An almost exclusively vegetarian diet is the exception for bears.

Most need more protein to thrive, and they'll go to extreme lengths to get it.

♪♪ In India's dry grasslands, food is hard to come by.

♪♪ This fortress holds the answer.

♪♪ But how to get inside?

The sloth bear is the real-life Baloo, the character in Rudyard Kipling's "Jungle Book."

♪♪ Its distinctive shaggy coat made early explorers think it was a sloth.

But it's the bear's powerful paws and unusual face which are key to how it gets its food.

♪♪ Under cover of darkness, it targets the mound's inhabitants.

Termites.

They build these giant mounds, which are fortified by a wall of sun-baked clay.

Most termites are less than half an inch long, but there could be over a million of them inside.

♪♪ To get to them, the sloth bear has just the tools for the job.

It uses 3-inch-long claws to tear into the mound.

♪♪ Soldier termites have pincers, but they're no match for this bear's next form of attack.

Long, floppy lips and a lack of front teeth allow it to use its mouth like a vacuum cleaner and suck up hundreds of termites at a time.

♪♪ It can also shut its nostrils to avoid inhaling dirt or any stray insects.

♪♪ A sloth bear can demolish an entire termite colony in a single night.

♪♪ Rich in fat, as well as protein, termites provide almost double the calories of a steak.

Available throughout the year, insects like these can form 95% of a sloth bear's diet.

Around the world, physical adaptations allow different bear species to specialize in the most nutritious food available.

♪♪ In Southeast Asia, nothing is out of reach for the sun bear.

♪♪ Sickle-shaped claws and bare-soled feet mean it can access fruit in the jungle's tallest trees.

♪♪ Powerful paws expose insect larvae.

♪♪ And they use a 9-inch-long tongue to fish them out.

♪♪ ♪♪ Japan.

On the rocky slopes of the Hida Mountains, an Asiatic black bear uses its sense of smell, and careful footwork, to uncover its prey -- ants.

♪♪ It can spend up to eight hours a day flipping these rocks.

♪♪ When it comes to food, most bears show a remarkable level of resourcefulness.

And that's just as well, because the bears living in the Northern Hemisphere face a particularly difficult challenge.

♪♪ North America.

In seasonal climates, the food available changes with the time of year, so bears like these grizzlies have to switch food sources every few weeks.

♪♪ Spring brings new growth.

♪♪ Succulent sedges and grasses are just a few of the 175 different plant species in grizzly bears' diet.

As summer approaches, seafood appears on the menu.

But the bears need to plan ahead.

They time their hunting during the three-to-five-hour window of low tide.

On the exposed sand, they detect their prey by smell.

Clams.

With over a billion nerve cells in their nose, they can even smell these crustaceans through the sand, and grizzlies can dig up as many as a hundred clams in one low tide.

They'll also gather seaweed, barnacles, and mussels to add to their diverse diet.

But in early autumn, the bears' appetites suddenly go into overdrive.

On the coast, this coincides with the appearance of a major food source.

♪♪ The salmon are back.

Hormonal changes cause the bears to enter a phase of excessive eating, or hyperphagia.

They eat almost continuously, without ever feeling full.

At this time of year, grizzlies can consume up to 100,000 calories a day.

♪♪ That's the equivalent of over 1,000 boiled eggs.

But this gluttony has a purpose.

♪♪ [ Wind rushing ] ♪♪ [ Howling ] As winter tightens its grip in the north... ♪♪ ...feeding opportunities begin to disappear.

♪♪ ♪♪ For many large animals, this can spell disaster.

♪♪ But bears have a solution.

♪♪ And it requires an extraordinary feat of physiology.

♪♪ After their autumn feeding frenzy, they retreat to a den.

♪♪ Inside, they enter a state of hibernation.

♪♪ In this deep sleep, their body temperature drops several degrees, and their heartbeat slows to as few as 10 beats a minute.

♪♪ ♪♪ They don't eat or drink for up to seven months.

Instead they rely solely on their fat reserves to stay alive.

Grizzlies and American and Asiatic black bears all enter this deep form of hibernation in colder climes.

They don't experience any heart complications, blood clots, or even bone and muscle loss during this extended period of inactivity.

The implications for human medicine are huge.

NASA scientists are hoping the bears' biochemical secrets will one day help astronauts with long-distance space travel.

[ Bird chirping ] ♪♪ With the arrival of spring, the bears emerge healthy and lean.

After their long fast, they stock up in the meadows.

♪♪ Bears have had to adapt to make the most of the food available.

♪♪ But it's not the only challenge they face.

Adult bears lead mostly solitary lives.

♪♪ And as the season warms up, many animals have just one thing on their mind.

♪♪ So how does a bear find a mate?

♪♪ The answer involves trees... ♪♪ ...and a good old-fashioned back scratch.

♪♪ ♪♪ As they rub, they mark the tree with their scent.

It's like leaving a calling card.

♪♪ The higher they can rub, the better.

This way, their scent can travel farther.

♪♪ And it doesn't take long for these chemical signals to attract other bears... ♪♪ ...who then leave their own messages.

♪♪ It's thought that this unusual form of communication helps individuals work out who's around, who to avoid, and who's available.

Now all they need to do is get together.

On the Alaskan coast, the dating game has moved to the next stage.

Male and female grizzlies gather on the meadows.

Some travel for hundreds of miles to be here.

♪♪ The big males show off with a strut, known as the "cowboy walk."

But there's more to this swagger than meets the eye.

As they twist their paws into the grass, they leave behind a scent trail made up of 26 volatile chemicals.

The effect is enhanced with urine.

These pungent scents and body postures signal the bears' intent to mate and help males establish a hierarchy.

But when males are evenly matched, there's only one way to resolve their differences.

♪♪ [ Bears growling ] ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ With the battle over, the victor can continue his courtship.

In some parts of the world, finding a mate is even more challenging.

♪♪ The Arctic.

♪♪ Freezing temperatures and gale-force winds make this land of snow and ice one of the most inhospitable places on the planet.

♪♪ But to the polar bear, it's home.

♪♪ Polar bears evolved from brown bears many thousands of years ago and spread north.

♪♪ Here, a lone male occupies a massive home range... sometimes in excess of 100,000 square miles.

♪♪ That's an area over 4,000 times the size of Manhattan.

♪♪ So, the chances of meeting a mate here seem vanishingly small.

♪♪ But this Arctic nomad has a strategy.

♪♪ In common with grizzlies, polar bears have sweat glands on the soles of their feet.

So their footprints are full of information.

♪♪ All a male has to do is follow them.

But his long-distance trek is no guarantee of romance on the first date.

When he finds her, he's got to impress.

♪♪ She'll only mate with him if she thinks he's fit and strong.

So she puts him to the test.

His downhill tobogganing lacks style.

But he's keeping up.

The next challenge is a rocky ascent.

The female makes it look easy.

Weighing almost twice as much as she does and at close to half a ton, his size isn't helping him now.

He needs some encouragement, and she has a unique way of giving it.

This is one of the few times that polar bears come together as adults.

Courtship can last three weeks.

Then they'll go their separate ways.

♪♪ The female will spend the winter months under the snow... where she'll give birth to her cubs.

♪♪ And the male will endure the coldest weather that any bear on the planet must face.

♪♪ Temperatures will drop as low as minus 40 degrees.

But this extraordinary bear has mastered the art of staying warm.

A double-layered fur coat not only helps to keep out the cold, but it also keeps the heat in by trapping infrared radiation.

And underneath is a layer of pure blubber, up to 4 inches thick, which provides vital insulation.

But to maintain its ample waistline, a polar bear needs high-fat food.

Seals.

And the best place to catch them is on the sea ice.

This is where the seals create breathing holes and dens.

♪♪ The polar bear's sense of smell is the most acute of all the bears.

Seven times more powerful than a bloodhound, it can pick up the scent of a seal from 20 miles away.

♪♪ To help him walk across the ice sheet, large paws act like snowshoes to spread his weight, while bumps of skin on his footpads and hairs between his toes provide grip.

♪♪ ♪♪ He can pinpoint his prey, by smell, 3 feet beneath the ice.

♪♪ ♪♪ But seals are agile swimmers, and nine out of ten hunts end in failure.

There are successes, and to survive, each bear must catch at least one adult seal every 10 to 12 days.

But today, polar bears are facing a new challenge.

With rising year-round temperatures, their hunting grounds are shrinking.

Enormous masses of ice that were frozen for thousands of years have broken apart and melted away.

[ Bear grunting ] Each year, the Arctic's frozen ocean is becoming smaller and thinner.

♪♪ Polar bears are being forced to swim ever-greater distances to hunt seals.

♪♪ With their powers of endurance pushed to the limit, many will starve or even drown.

♪♪ If current trends continue, some scientists predict the summer sea ice in the Arctic could be gone within half a century and, with it, potentially a third of all polar bears.

♪♪ ♪♪ In some parts of the Arctic, polar bears are trying to adapt to this changing world.

[ Trucks beeping ] Driven by hunger, the normally solitary bears have been filmed coming together to feed on our leftovers.

It's a desperate and alarming strategy.

In today's world, people are increasingly encroaching on the wilderness.

This is a problem for all animals, but the bears' opportunistic nature means many of them will try to take on this new challenge.

[ Siren wails ] Bears have an inbuilt curiosity and the largest brains, relative to body size, of all carnivores.

♪♪ They've discovered a way into our world.

[ Laughter ] And cubs follow the lead of their mothers.

With their dexterous paws, they are practically made for breaking and entering.

♪♪ Unlike many animals, they'll readily investigate anything new... and quickly work out if it can be useful.

♪♪ Because of their broad diet, they thrive on our food.

♪♪ Some scientists believe that the bears' problem-solving abilities mean they should be ranked with monkeys in terms of intelligence.

♪♪ Learning by trial and error, they've discovered that our world can bring many benefits... ♪♪ CHILD: The bear's right next to us!

NARRATOR: ...although our interaction with bears can at times be fraught with danger for both of us.

[ Indistinct shouting ] CHILD: Oh, my goodness!

Dad!

Dad!

[ Children screaming ] NARRATOR: Where bears and people increasingly need to share resources, there are occasions when this relationship can be more harmonious.

Serranías del Burro.

A mountainous region in Mexico's northeast.

It's home to the black bear, which is endangered in this country.

For this family, the big challenge in summer is finding enough to drink.

The underlying limestone soaks up the rain, leaving no permanent streams.

Fortunately, there's another source... but reaching it requires a certain cunning.

[ Cattle lowing ] ♪♪ This is an area used for cattle grazing.

♪♪ The ranchers have set up watering holes by tapping into underground springs.

♪♪ The bears can take advantage of this.

But the cattle are desperate for water, too.

They're naturally wary of potential predators and armed with sharp horns which could easily injure or even kill a bear.

♪♪ ♪♪ The livestock gradually move off.

The family finally have their chance to drink.

The ranchers here are very tolerant of bears.

They even provide a step up for the cubs.

♪♪ ♪♪ Weighing all the risks and taking advantage of new opportunities are vital skills for bear cubs to learn.

Soon they will have to take their first steps to independence and stand on their own two feet.

♪♪ ♪♪ After spending their early years in the care of their mother, young bears face a very different world.

♪♪ For the first time in their lives... they are alone.

♪♪ To be a bear takes a lot of skill... ♪♪ ...from avoiding danger... surviving the seasons... and learning to tackle whatever food is in front of them.

♪♪ And if they can do that, they'll reap the rewards.

♪♪ But the bear's biggest challenge yet... [ Ship horns blaring ] ...is today's rapidly changing world.

[ Ship horns blaring ] Six of the eight species of bear are vulnerable to extinction.

♪♪ There is more pressure than ever on their habitats and the food they depend on.

They'll need our help... and our willingness to share space.

If we give them a chance, their brains, brawn, and ability to adapt will do the rest.

♪♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this "Nature" program, visit pbs.org.

♪♪