BBC: Animal Battlefield

This is a story about one of nature's top predators...

...and how it uses its stamina, intelligence and tenacity to survive.

For the first time,

you'll have an extraordinary view of the wolf and the wolf's world.

Through the eyes of its leaders and their family - the pack -

you'll witness the stress and success of their life as a team.

And see how the events in the pack's life take place here, in their territory.

A place that's worth protecting in any way they can.

You'll join them in their constant search for food -

food big enough to fight back...

And watch as they battle their bitterest enemies - their neighbours -

and their other fierce rival, the grizzly...

encounters that threaten their future.

This is a story, but everything you're about to see is based on fact.

The strength of the wolf is the pack,

but is this pack up to the challenges of life on the wolf battlefield?

The Rocky mountains of North America... home to hundreds of wolves.

A wilderness that stretches for thousands of square kilometres.

With special technology we can analyse

the wolf's world in a way that ordinary cameras cannot show.

Creating a virtual reality...

From this view, we can focus in on just two hundred square kilometres -

our pack's domain.

Revealing the key zones within it:

Lowland plains...

with ridges above for lookout points...

A river that flows all year round...

Dense, forested slopes for cover...

And all this flanked by towering mountain peaks.

Prime wolf territory, currently occupied by our Battlefield pack - the Jets.

This tightly knit team of seven wolves is led by the alpha pair -

a big, silver male and his smaller, black mate.

The alphas are mother and father to four adolescents -

all born just under two years ago.

The seventh wolf, an adult male, is an outsider -

and pack underdog.

All the wolves are expert hunters. They need to be.

lt's January and on the face of it, the wolf's world looks lifeless...

There's deep snow on the high slopes

and it's minus 2O degrees Celsius.

Most small mammals are hibernating and are off the menu.

Only larger prey, like buffalo and elk, are awake and available.

But they're too big for a single wolf to tackle,

and they're always on the move to find enough to eat.

So, the Jets must stick together, and be nomadic too.

Wolves are built for long-distance travel...

Their long legs, big lungs and hearts

give them a cruising speed of eight miles per hour.

They can average fifty kilometres a day -

and clock up three laps of their territory a week.

But how do they find their way around such a large area -

and where do they start looking for food?

lt's always one of the alpha wolves who leads the way.

The alphas have held this territory for almost three years.

Experience has taught them that the herds don't move randomly.

They visit favourite feeding areas at certain times of year -

and they always follow the same routes.

Wolves don't move randomly either...

...which suggests they have a mental map of their territory,

an in-built route-planner that helps them visualise where they are,

and which path to take to intercept their prey.

A wolf's brain is thirty per cent bigger than a dog's -

and it's this extra brainpower that helps the wolf navigate so effectively.

The pack's trails make up a closed circuit inside their territory -

but some routes connect with their neighbours' trails,

creating a huge network of wolf highways for thousands of square kilometres.

With so many other wolves in this area,

it's vital our pack has exclusive rights to its territory and food supply.

Somehow, the wolves must protect what's theirs...

...because next door

they have the neighbours from hell!

ln just four years, this rival pack has grown unusually large.

There are twenty-two of them.

The Big Pack's alpha wolves have raised many youngsters -

and none of them have left home yet.

There are problems with a pack this size.

They can't afford a day without a kill.

And to find enough food, they need a big territory.

This makes the Big Pack dangerous...

sooner or later they could invade the Jets' living space.

Our pack's best defence is to engage in chemical warfare.

The agent they use is scent.

lt's a clear warning to outsiders to keep out -

a signal all wolves recognise and ignore at their peril.

Wolves leave a scent mark every hundred metres

or so along their trails and boundaries.

These signposts are unmissable, and they last for weeks...

ideal for animals constantly on the move.

And the source material is portable and easy to produce.

As the urine spreads and evaporates, it releases the wolf's personal perfume.

Scent marking is the responsibility of the two pack leaders.

All they need to do is refresh each mark as they travel -

leaving a trail of reassuringly familiar, smelly hotspots.

A wolf has more than two hundred million scent receptors in its nose,

making its sense of smell ten thousand times more sensitive than ours.

Along its territorial boundaries, each pack goes into overdrive,

responding to the threatening smell of its neighbours.

The stakes are so high here

that wolves use droppings, as well as urine, as a double deterrent to intruders.

The alphas encounter and produce a scent signal every two minutes.

By doggedly reinforcing their frontline, they try to keep their territory secure...

...leaving them time to relax and socialise.

The pack's social life revolves around the alpha wolves...

They dominate more by strength of personality than by brute force.

They use facial expressions and body language to keep everyone in line

and show how they feel.

Dominance and submission help keep the peace.

These tussles may look aggressive,

but they can simply be a way of reinforcing bonds

and reassuring each wolf of its place in the pack.

The adolescents are almost full-grown...

but still too young to leave the pack.

For them, free time is playtime.

Company is vital for a wolf...

separation can lead to disaster.

Last spring, the alpha female was left alone...

With prey in very short supply, the pack was forced to split up to search for food,

leaving her at the den to guard her pups.

After a week, she faced a harsh choice -

leave her pups or starve.

Even underground, pups can be vulnerable...

but in the end the mother's hunger drove her to take the risk.

A grizzly's sense of smell is as powerful as a wolf's -

and after a long winter without food, it has a craving for protein.

This time the wolves' attack came too late...

With her pups dead, the female's only chance to breed last year was dashed.

Teamwork is the key to wolf survival.

Even if you're the underdog, it's best to be one of the gang.

Life on his own would be lonely and short.

Operating as a pack is also the only way wolves can hunt big animals effectively.

And it's always the alpha wolves who take the lead.

The Jets haven't eaten for four days

and now they're totally focused on finding food.

Each wolf taps into its mental map,

which isn't just a 3-dimensional route-planner,

it's also a picture catalogue -

a menu of prey animals available.

Any one is an attractive target.

But ranging in size from fifty to a thousand kilos - none is easy meat.

Bighorn sheep are fairly small, but live in groups,

have big attitudes - and serious headgear.

Others, like moose, are solitary and roam territories of their own.

Every few weeks,

the wolves check up on them to see if they've become sick or injured.

Who to hunt and when are key to a successful kill -

and their mental maps help them select animals

that could offer the easiest pickings.

Top of the menu today are elk...

and the wolves must use their mental map to work out how to intercept them.

Years of following migrating herds all through the changing seasons

mean the wolves have memorised the elks' routine.

ln January, they can predict the elk are heading for the valleys to the east,

forty kilometres away.

Just getting here has taken seven hours.

Now they find a vantage point to keep the elk under surveillance.

The best strategy for hunting big animals is to select the most vulnerable.

Usually by midwinter, with food harder to find,

some pregnant females will be struggling...

As well as being almost four months pregnant,

they have their seven month-old calves with them.

The youngsters are weaned, but still stay with their mothers for protection.

Wolves are always interested in calves, as they're more likely to make mistakes.

But so far, this winter's been mild

and food in this valley is still within easy reach.

The females look well fed and healthy - and so do their calves.

Has our pack come all this way for nothing?

And there's another problem -

the Jets are only four kilometers from their northern border.

There's a danger the elk will drift across into Big Pack territory.

From their position above the herd, the wolves may be able to spot a weak animal.

After hours of waiting, it's the alpha male who makes a move...

They've seen no obvious soft target, so it's time to take a closer look.

They make no attempt to hide as they approach...

...and the elk know they're there.

The wolves split up and assess the herd,

looking for the wounded...

the lame...

the weak.

Weakness is easier to see if the elk are moving;

easier still if they're running.

The alpha female has picked out a nervous calf...

at this age, it's had little experience of wolves

and its confidence can be easily shaken.

Now the elk are forced to run,

but the older animals know what to do.

They run towards the front and in the middle of the herd -

furthest away from the chasing pack -

where they're less likely to be spotted if they are carrying an injury.

The wolves can run as fast as elk,

but after going without food for several days,

will they have the stamina to keep up?

The elk head for a frozen riverbed

where drifting snow is deeper than on the slopes.

lt's not a problem for the long-legged elk,

but it slows the wolves and saps their energy...

The wolves clear the drift and accelerate to forty miles per hour.

The herd tries a different strategy and heads for the woods.

They're much more sure-footed on the uneven surface of roots

and hollows around the trees...

Here, the wolves might find it tough to keep up.