[insects chirruping, birds calling] [woodpecker pecking] [narrator] The great forests. Spectacular landscapes where some of nature's
most dramatic transformations play out. Throughout the year,
the challenges for its inhabitants change, from the rich pickings of summer
to the bleakest of winters. For all manner of creatures,
it's worth the fight to lay claim to their patch of territory and to share in the natural riches
of the forest. [birds chirping] It's only really from the air that it's possible to appreciate
the scale of our global forest. Trees cover four billion hectares
of our planet. Thirty-one percent of the land
is blanketed in woods that help purify our air
and create oxygen. Much of the Northern Hemisphere
is wrapped in its life-giving embrace. From east to west,
it provides food and shelter for creatures of every conceivable form. [calls] [howls] But for all its protective properties... [wolf sniffing] it can be a testing place to live, especially now, in the heart of winter. Wolves always have company. With strong bonds,
they have the solidarity of the pack to get them through winter. But even so, with the landscape
buried beneath the snow, it can be hard to find food. It can smell the sable. But the wily weasel has plenty
of boltholes to stay out of harm's way. The exquisite beauty of the snow
may be a treat for the eyes, but it makes living very tough
for the forest's inhabitants. [animal yelps] [moose calls] Moose are hardy northern specialists,
expert in nibbling whatever they can find. At this time of year,
it's little more than twigs. [moose calling] Though they hang out together in winter,
the animals can be on edge. Food resources are running low and it doesn't take much
for tempers to flare. Both males and females fight,
but at this time of year, the bulls have lost
their distinctive antlers. All arguments now are settled with boxing. [moose grunts] The hooves are more
than just weapons, though. They are also valuable snow shovels
used to uncover buried vegetation. Their squabbles attract a bear,
a rare sight in winter. [moose grunting] Normally he'd be tucked up in a den
to sleep through the long, cold months, but from time to time,
bears arise and look for a snack. It's late winter and the snow is soft. Hard going for the short-legged bear. He doesn't stand any chance
of catching up to a moose. Their long legs keep their bodies
above the snow and they walk in each other's tracks
to save energy. Perhaps the bear will stumble
slowly back to bed. On the other side of the world, the snow causes problems
for a very different forest dweller. [wind howling] The Japanese macaques
work quickly to dig the snow, trying to find leaves
that have been preserved beneath. Apart from humans, no other primates live
so far north or in such cold conditions. Being out in the blizzard
can get a bit much. [macaque screeches] Luckily for this troop,
there is a break from the cold. The perfect respite.
A dip in the local hot spring. Volcanic activity underground
means even on the coldest days, there is a warm bath waiting for them. [screeches] After a day at the spa, they are ready
once again to tackle the cold. Winter is tough on everything
that has to face it. But there are a few animals that opt out. Dormice and many other small creatures
hibernate through winter, entering a state of torpor when the functions of their body
grind almost to a halt. Large animals like badgers
have their own version... just slowing their metabolisms down
and resting to save energy and stay in out of the cold. [wind whistling] While some forests remain green and lush,
others are stark and bare during winter. Deciduous trees shed their leaves... leaving skeletons of their former glory. It doesn't leave much food or shelter, but that doesn't mean the forest
isn't alive with the hardy and adaptable. [woodpecker chirping] A lucky find, fallen seeds,
can cause conflict. But distracted by the chance to feed,
the birds face a far bigger threat. [birds chirping] [loud chirping] It just takes one alert bird
and the cat goes hungry. [boar snorts] Sometimes the predator is unlucky. Other times it's the prey that loses out. Winter's long and hard, but gradually
the sun's rays are getting stronger. There are sounds and sights in the forest
that suggest change is in the air. [crane trumpets] The migratory crane pair has returned
to their forest nesting ground. To remind themselves
just what a good couple they make, they mimic one another's movements,
demonstrating perfect harmony. [crane calling] They are not the only pair to return. The riches of the forest
call back those residents too fragile to have stayed over winter. With their bond reconfirmed
and their patch secured, it's time for some family planning. Spring is on its way. [birds singing] [insects chirruping, birds calling] The white of winter slowly ebbs away,
revealing a surprise. Far from destroying the forest,
the snow has been protecting it... creating a barrier against the frost... a warm blanket under which plants have got
a head start on their season's growth. The spring snowflakes first,
replacing one white carpet with another. The melting snow waters the plants, the final ingredient they needed
to announce the spring. Patiently the forests
have lain dormant through winter, but the wait is finally over. Now that the air has warmed,
water can fall as rain instead of snow. Water and sun, a magic formula
that can cause an explosion of life. [birds calling] In anticipation of spring's riches,
new faces appear in the forest. [boar snorting] The skirt of a tree provides
a ready-made nursery for this litter. Wild boars deliver
around a dozen stripy piglets. Now a week old,
the youngsters are ready to fly the nest. And seem to have a lot of pent-up energy. From the word go,
there is a piglet pecking order. The bossiest piglets will get
the best opportunities to feed and will grow faster than their siblings. There will be milk on tap for around
their first three months of life. After that, not only will they
have to feed themselves, but they will grow out
of their racing stripes. The forests that were silent for so long
now ring with birdsong, as each of these featherweights
lay claim to a small home where they can raise their young. [chirping] [distant bird calling] [distant animal calling] Babies come in all sizes,
and the moose is one of the biggest. It takes a matter of minutes
for the gangly infant to get balanced on its stilts. But it'll need the height advantage when it reaches for milk
from its massive mother. Despite being the biggest predator
of the forest, the brown bear has
among the smallest babies. Her cubs were born
during her winter sleep. They arrived half the size
of a bag of sugar and for their first few months stay hidden
in dens with their sleeping mothers. [cub whines] They share a close bond with their mum
and will spend several years by her side. With such a big, powerful mother,
they can afford to kick back and play. [insects chirruping, birds singing] [distant animal calls] [frog croaking] Within weeks of spring thaw, every puddle or tree trunk
seems to be occupied and the woods put on
their most elaborate display. [babies peeping] The colors of spring are a call to action
for a fleet of pollinators. The plants use bright colours
and sweet nectars to lure the bugs. A sugary treat awaits them, as long as they transfer pollen
in return for the favour. While some seem
to show off their existence, others are hardly noticeable. The roots of an old oak tree
provide the perfect safehouse where a mother fox delivered her pups. Born blind, deaf and toothless, the hamster-sized youngsters are
totally dependent on their mother. [pups whining] And for their first few weeks of life,
she'll barely leave their side. The den she made will be their home
for the next few months. [birds chirping] The oak leaves above
are the perfect hunting ground for a pair of coal tits, who transport juicy caterpillars
back to their nest. Like all songbirds,
they keep a low profile, trying not to reveal
the location of their nest. [babies chirping] But they are being watched. [babies chirping] When a hungry chick can eat as many
as 100 caterpillars a day, it's hard for the parents to go unseen. [bird calls] Under the cover of darkness,
they pay the price. [calling] But one family's loss is another's gain. [owlets chirping] There's light in the darkness. Mixing chemicals in her body, the female glow-worm shines a beacon
to draw in a potential mate. [birds calling] While the forest seems
to find its stride... [boar snorting] draped in lush greenery... [pups whimpering] The vixen finds herself
with her hands full. Her pups are growing quickly
and need constant attention. [pup whining] It takes a lot of milk, but eventually
it calms the family down. [woodpecker pecking] White storks have high-rise accommodation. Today they mostly nest on roofs
and other man-made structures, but their roots lie in the woods. Trees were their preferred locations. Of course, that means building materials
need to be transported in. Luckily, timber for home building
is never in short supply in the forest. There is quite an art to getting
the feng shui right and this builder's a perfectionist. Woodland browsers like red deer
nibble at young trees and so control their growth. Thanks to them, clearings
are maintained in the forest... which are not only rich in grass but provide open,
sunny playgrounds for the calves. Deer might be the biggest browsers,
but they are not the most numerous. Millions of mini beasts
munch their way through the forest. Combined, they outweigh
all of the big mammals. And they, in turn, feed mini predators. Although they are not always
easy to catch. [ant thuds] Forest pools provide a moat,
surrounding the crane's fortress. The island nest is the best way
to keep their eggs away from foxes and other nest raiders. The eggs are not impervious
to attack from above, and the great grey owls
keep a close eye on the goings on. But there is drama enough in their nest.
A tragedy unfolding. The owls lay multiple eggs,
but rarely raise them all. The first chick to hatch
will be the biggest and will be the parents' priority
when they deliver food. In this rare incident,
the runt of the litter's got lucky, but its success is short-lived. Bullied out of food,
the little one's unlikely to survive. [bird screeches] The cranes, on the other hand,
are attentive parents, teaching their chick what to eat
and never letting it out of their sight. [squawks] The owlet soon
outcompetes its siblings, and now, without competition, he has a good chance
of making it to adulthood. [woodpeckers pecking] [pups whine] At a month old, the fox cubs are stronger
and more curious about their surroundings. Time to start exploring. Their baby-blue eyes are darkening
and will soon turn brown, but right now they are filled
with the wonders of the forest. He spots one of the shiest inhabitants,
the black stork. Some of his neighbours
are quite intimidating. Forest pools and streams provide
the perfect fishing ground for the black stork pair. Less social than the white storks, they build secluded nests
hidden deep in the trees. Black stork chicks start out white. It will take several months
for the insulating down to be replaced by adult plumage. Throughout the breeding season, the parents continue to reaffirm
their commitment to each other with some ritualised bill clapping. From their lofty perch, they can watch
the forest unpack its summer riches. The plants grow, and so too
do the animals they shelter. The deer fawns are starting
to enjoy solid food. Lynx kittens are growing fast. They are still dependent
on their mother's milk, but with a growing sense of independence. Sometimes mum needs to intervene
to keep her brood together. It'll take six months
for her to raise these kittens, turning them into top hunters. For the wildcat, even a lazy summer's day
can't distract it from the chance to hunt. The trees are alive with animals
hard at work to feed their young. But it doesn't make it any easier
for the cat to catch them. [chirps] [woodpeckers pecking] At two months old, the badger family's out
enjoying a long warm summer evening. The leaf litter offers rich pickings:
insects, bulbs and nuts. Though it's interrupted by play,
even the grown-ups join in. But the family's shy about being out
in the daylight, and easily spooked. Fixed addresses offer a safe playground
where young animals can learn the ropes... figuring out what to hunt
and how to interact with each other. The fox cubs are also out exploring. Already, hunting instinct comes naturally, and when he spots
the movements of a squirrel, it's a target
that's too tempting to resist. But he's going to have to
improve his game. Better practise on his siblings. There are many dangers in the world. But at the moment, even the wolves
are more focused on quality family time. [raven squawking] Despite being top predators,
wolves are shy and secretive and never more so than around their den,
a secluded forest clearing. [squawking] Though it's hard to keep a low profile with ravens constantly shouting
about your presence. The intelligent birds
often follow wolves around, knowing that scraps of meat will be left
after the wolfpack's meals. The parents are the alpha pair,
the leaders of the pack, and will stay together for life. The youngsters will likely stay with mum
and dad for a number of years before branching out in search of a mate
and a home range for themselves. All through the forest,
youngsters are growing up. On their high-rise, the stork chicks
are now as big as their parents. They have just discovered their wings. It takes a while to master
the two-meter span. They begin with short trial flights. The storks will not stick around
for a northern winter. As soon as the flock's strong enough, they will head south
to seek some African sun. They know that the riches
of summer won't last. The storms of late summer
give the forest one last watering. It's good for the landscape
but tough on its inhabitants. [thunder crashes] Once he's dried off a bit, a tree trunk
helps the bear to primp its fur. [bird squawking] The soundtrack of the forest is changing. [bellowing] The temperature's dropping,
but hormone levels are on the up. [bellowing] And it's not just the animals, the trees
themselves are undergoing changes. [bird squawks] The oak casts out its acorns, baby bundles that contain
all the materials and nutrients needed to start a new tree. Millions rain down, but most
won't have the chance to grow. [boar snorting] For squirrels, boars,
and many other species, the manna from above
couldn't have come at a better time. A feast that will fatten them up
for the lean months that lie ahead. Deer don't have time
to worry about acorns. This is the rut. The fallow bucks strut their stuff,
bellowing... challenging others
to question their superiority. Anyone who does want to test their title
will have to fight. [horns clattering] Productivity in the forest
is shutting down. It's a time of death and decay, but also when the landscape
takes on its most magnificent hues. All over the Northern Hemisphere, the deciduous trees
are shedding their leaves. They will no longer
turn sunlight into food, but instead they will decompose, creating rich soil and ultimately
returning the nutrients to the tree. For forest wildlife,
it's a colourful wake-up call. The easy living is over. Life's going to get a lot tougher, and all creatures get to work eating
as much as they can while they still can. For bears, like the Asiatic black bear,
a countdown begins. He'll sleep through winter but will only survive if he manages
to get enough reserves of body fat. But he's still young and would rather
play with his brother. Before long the siblings
will go their separate ways and lead solitary adult lives. [moose grunting] [animal calling] The cold air seems to get moose hot. The bull cautiously approaches
a cow and calf. Female moose will only let him near
when they are ready. [raven croaking] The calf is old enough to go it alone now, so if he plays his cards right,
the bull's in with a chance. He's watched from the wings
by a young hopeful. [animal calling] But until his antlers have grown a bit, it would be futile for him
to risk a challenge. Full-on moose fights are rare,
but things do occasionally go wrong. Which can provide a much-needed feast
for the bear family. [squawking] A rich supper before bed. The first snowflakes will encourage
the bears to seek shelter and hunker down. Not all animals will have that luxury. For creatures great and small,
a struggle's underway. Even the biggest animals,
like the European bison, seek shelter in the trees. But it's not just the cold
they need to worry about. The wolves are now old enough
to travel with the pack. But the bison's not going to stand
for any nonsense today. The snow wraps the woods
in an eerie silence. Many creatures have left,
or retreated to their burrows. But for the hardy who remain, it's back
to nibbling on twigs and shovelling snow. It'll be a long, tough winter. A challenge to endure. But it will be worth the fight when spring once again reveals
the riches of the forest.
