Bears The Wonder of Animals

Planet Earth...

millions of species...

..but a few are special...

..born to thrive.

ELEPHANT SNORTS

GORILLA HOOTS AND ROARS

These are the opportunists.

TRAFFIC NOISE

The collaborators.

The survivors.

What makes these animals so successful?

In this series we'll delve deep beneath the skin

to reveal the unique features that set some species apart.

BEAR SNIFFS

New behaviour,

and the very latest scientific discoveries,

will offer fresh insight into

the Wonder of Animals.

From the North Pole

to the tropics,

and everywhere in between...

..one group of animals

has mastered practically every environment on earth.

Rainforests...

..mountains...

..and even the open ocean.

Wherever they live, bears have the supreme ability

to find the highest quality food

and this is a skill that depends upon three key factors -

an extraordinary anatomy,

incredible intelligence,

and a truly remarkable physiology.

Tropical rainforests are amongst the most bio-diverse

places on Earth.

Bountiful ecosystems,

teeming with life.

But the bears living here, are only interested

in the most energy-rich food -

and that is found in the most

inaccessible places.

To reach it requires a very specialised anatomy.

Night-time

in the Indian jungle.

A sloth bear is on the hunt for food.

But the most protein-rich meal for this bear

is hidden inside a sun-baked fortress.

With claws up to 8cm long,

it breaks through the rock-hard structure...

..to reach the prize -

termites.

Sloth bears can sniff out termites

through a metre of earth.

But once disturbed,

the moveable feast rapidly disperses.

So the bears have evolved a practical solution.

They've lost their two front teeth

and by drawing air in through the gap,

they can suck up the termites.

This versatile vacuuming snout means that sloth bears

can consume vast quantities in one sitting.

And to stop any termites straying up its nose,

it's adapted a flap to shield its nostrils.

Sloth bears have specialised to exploit the rich pickings

at ground level.

In the lush cloud forests of the Andes,

the best food is even harder to reach -

but not for South America's only bear species,

the spectacled bear.

They're lured into the trees by these -

bromeliads.

The problem is, they are about 15 metres off the ground.

Taller trees with larger canopies offer more plants,

so the higher they can climb,

the better.

For an animal that weighs 100kg

this could pose quite a challenge.

But the bears' anatomy has adapted to overcome this.

Each front paw has an enlarged wrist bone

which acts like a rudimentary thumb,

helping them to grip the branches.

The rewards for their efforts

are the sugar rich cores of the bromeliads.

But to access them, they must chew through the tough exterior.

Relative to their size,

spectacled bears have the largest jaw muscles of any bear species...

..and teeth that are secured into their jaws with three roots,

instead of two.

But what if the food you seek is not only in the treetops,

but also has a built-in deterrent, too?

In the dense lowland forest of Borneo,

sun bears are on the hunt for an exceptionally concentrated

source of calories -

honey.

And they use a perfect combination of adaptations to get it.

Whilst smell is their primary sense,

as they climb, they tap the tree trunk

to listen out for hollow cavities

that might just conceal a beehive.

BUZZING INSECTS

Whilst bee stings would harm most animals, sun bears' skin

is protected by an incredibly thick fur.

But one of the few places they don't have fur, is on their feet.

Naked soles give them a better grip as they climb.

And with an extra long tongue - almost 25 centimetres long -

they can not only reach the honey,

but also the protein-rich larvae deep inside the hive.

The bears in the tropics have a specialised anatomy

which allows them to reach the richest food

in the most inaccessible places.

And although this is a challenge,

at least their food is available

all year round.

North America -

bountiful summers,

followed by bleak winters.

In seasonal climates, food supply is dictated by time of the year,

so to survive these periods of boom or bust,

bears need more than physical adaptations.

What they need is intelligence.

Grizzly bears have an incredible ability to anticipate

the changing seasons.

From fresh grass shoots in spring,

to clams and berries in summer,

the bears know exactly where and when

to find the best food.

August marks the arrival of one of the year's richest food hauls

and it can be found in an unexpected location,

more than 3,000 metres up,

on the peaks of the Rocky mountains.

These grizzly bears have come to seek it out.

It's a long and arduous journey,

but they make this pilgrimage

at the same time every year

for a very good reason.

Hidden under these barren rocks

is an abundant supply of food.

Tiny packets of protein and fat.

Moths...

in their millions.

The bears have learned, and remembered,

that for a short period of time each year,

moths roost beneath these boulders.

During the day, they're less active and easier to catch.

Whilst they might seem like a tiny meal for such a large animal...

..a bear can devour up to 40,000 moths in a single day.

And that's 20,000 calories.

Their knowledge is passed onto their cubs,

so generations of grizzlies return to the same spot

in the same month, year after year.

Grizzlies anticipate the changing seasons and lean times ahead.

As summer draws to a close,

there's one last opportunity

to stock up before winter.

They begin to gather near the coast

searching out a prime position.

And this is what they've been waiting for - salmon

returning to spawn in their thousands.

These bears are first in line for a nutritious catch.

Triggered by hormonal changes,

the grizzly bears now enter a phase of hyperphagia.

This allows them to eat constantly for up to 20 hours a day,

without ever feeling full.

They can consume up to 100,000 calories in a single day.

And given the abundance of salmon,

they can afford to be picky.

Just like the bears in the tropics,

they seek out the highest form of energy,

selecting only the fat-rich eggs,

the skin, and brain of the fish.

In open water, it's not always easy.

But as the salmon move further upstream...

..the grizzlies are here, too.

Where the river narrows it will be easier to land a catch.

The salmon run is the very last chance to fatten up.

But only bears that have eaten well enough

will stand any chance at all

of surviving the unforgiving winter.

Up until now, their intelligence has seen them through,

but at this point, it's imperative that their physiology takes over.

As winter closes in,

there are few foraging opportunities left to exploit.

Now the bears' metabolism transforms

to survive without food,

and they enter hibernation.

By mid-January,

temperatures can plummet as low as minus 20 degrees centigrade.

But beneath the frozen surface, in its den,

a grizzly's body temperature is around 35 degrees.

The substantial fat reserves built up over the summer

act as fuel for heat generation.

As fat is broken down,

the cholesterol content of the bear's blood surges.

It's not yet fully understood,

but somehow the bears' sophisticated physiology

means that they can withstand high levels of cholesterol

without any risk of heart disease.

During its slumber, a bear won't eat, urinate or defecate.

Instead, it recycles the nitrogen

that would otherwise be excreted,

and uses it to rebuild wasting muscles.

This continual process, over the course of months,

ensures that they emerge fit, healthy

and ready to feed again in the springtime.

Incredibly, some bears will even give birth whilst hibernating.

These cubs are taking their first steps into the world.

For the mother, it's a triumph of survival.

She has starved herself for almost six months,

and lost a third of her bodyweight.

The priority now is to find food again.

Hibernation is a crucial physiological solution

to surviving the boom and bust of the seasons.

But one species of bear has a completely different strategy.

Its physiology has evolved

so it doesn't need to hibernate, at all.

The Giant Panda.

They feed almost exclusively on bamboo.

The cellulose in bamboo is difficult to break down...

..but pandas have a unique set of gut bacteria

which produce the enzymes necessary

to digest the tough plant matter...

..and release energy.

They are the only vegetarian species of bear,

and have even lost the ability to taste meat.

The genes for that switched off four million years ago.

Pandas have evolved to become bamboo specialists.

In the Qinling mountains of China, food is abundant

and available all year,

so the pandas can keep feeding throughout the seasons.

They are the only temperate bear species

that doesn't hibernate during cold winters.

Across the planet,

bears are able to take advantage of almost any feeding opportunity.

Specialised anatomy, highly developed intelligence

and a unique physiology,

all play their part.

But how does this superb opportunist cope

when it's faced with one of the bleakest habitats on Earth?

The Arctic.

This vast icy wilderness spans 15 million square kilometres.

Temperatures can plummet to minus 50 degrees centigrade.

And for five long months,

the sun doesn't rise.

Few mammals can tolerate this winter wasteland.

But one bear species has the senses,

physiology and anatomy to reign supreme.

At up to 700kg, the polar bear

is the biggest of the bears

with the highest energy demand.

For every day it doesn't eat,

it will lose a kilo in weight.

Feeding opportunities are so sparsely distributed

over this vast landscape

that a single polar bears' range

can span 300,000 square kilometres.

Over these distances, with few visual clues,

the polar bear has an incredible ability to seek out food.

They have one of the most powerful noses in the animal kingdom...

THE BEAR SNIFFS

..able to identify a scent from over 30km away.

And they can even detect what lies concealed beneath the ice.

With the sea frozen over,

ringed seals rely on air holes to breathe.

But the bears can sniff these out,

even when they're covered in a metre of snow.

Polar bears are the most carnivorous of the bears.

But they aren't interested in devouring the meat.

Digesting that could lead to a build-up of nitrogen,

and to excrete the nitrogen the bears would need to drink water.

But the only fresh water here is the snow,

and consuming the snow

would lower the core body temperature of the bear.

So instead, they concentrate on the energy-rich blubber...

..absorbing almost 97% of the fat they consume.

They have evolved to be obese, yet suffer no ill effects.

But how do polar bears endure the brutal Arctic winter?

As the days shorten, the weather closes in.

Just like grizzly bears,

females with cubs go into hibernation at this time,

but remarkably the males don't.

For them, winter offers the best feeding opportunities,

so in almost total darkness,

they battle through the bitterly cold winds.

But without the warmth of the sun,

it's a challenge to maintain a critical body temperature

of 37 degrees.

The polar bears' dense fur certainly plays a part -

with up to 1,600 hairs per square centimetre,

it's a fantastic insulating layer.

But a recent discovery has revealed

it's actually the fur's colour, or rather the lack of it,

that keeps the bears warm.

Appearing white, each hair is actually hollow and transparent.

With no pigment to absorb colour,

they reflect back the entire spectrum of light,

including the invisible wavelengths

such as infrared radiation, or heat.

The polar bears' warm body gives off infrared waves,

which radiate out from the skin's surface.

This valuable warmth could be lost to the elements,

but when the waves hit a hair filament,

they're bounced straight back onto the bears black skin

to be reabsorbed.

Trapping and recycling body heat in this way,

means that the polar bear is able to keep warm

when there's no sun,

and hunt for seals throughout the winter.

By May, days are getting longer.

Temperatures are rising.

The sea ice begins to melt.

For most animals, the change in season is welcome respite

from the Arctic winter.

But not the polar bear.

With the sea ice gone,

seals are largely out of their reach.

As the ice breaks up,

they're forced to take to water more and more often.

They can be at sea for 10 days...

..swimming for hundreds of kilometres.

And when they reach dry land,

energy-rich food here

is even scarcer than on the ice.

So during the summer months,

their physiology changes.

Faced with starvation,

polar bears could reverse the hibernation strategy of their cousins,

and sleep through the lean summer,

but that would mean missing out on potential food.

So instead, they have devised a remarkable alternative -

they hibernate whilst awake.

With scant feeding opportunities,

polar bears start recycling nitrogen to maintain their muscles,

just as hibernating grizzly bears do.

The difference is, that during this hibernation

polar bears remain alert.

So if they DO happen on a meal,

however small - like this seaweed -

they can switch off the recycling process of hibernation

to take in new nutrients and new energy.

This process of walking hibernation

appears to be exclusive to polar bears,

but its precise mechanism is not yet fully understood.

In their quest for the finest quality foods,

bears can reach the most inaccessible places,

they can survive times of boom and bust,

and even succeed in some of the planet's

most inhospitable environments.

Their extraordinary intelligence,

anatomy and physiology

mean they can take advantage of any habitat they find themselves in.

These animals can thrive

where few other species can even survive.

And that is the wonder of bears.