Black bears.
For the first time thermal cameras reveal their winter den.
Yet this is no wilderness...
all across North America bears and skiers are closer than you might think.
And the trouble really starts when they emerge in the spring.
Whistler mountain, in western Canada
is criss-crossed with some of the most demanding downhill runs in the world.
These slopes are not just a challenge for the skiers＃
This is the story of two mother bears.
One has been named Marissa 每 by the people who study her＃
and these are her two black cubs.
Marissa will raise her cubs in a truly wild way
near the summit of Whistler's busy mountains.
But that's not the only way to bring up a bear family.
Our other mother bear is called Jess.
She's also a black bear but, unlike Marissa, her cubs are brown.
Jess will turn her back on the wilderness.
Her family will spend the year becoming streetwise in and around Whistler town centre.
Both mothers face the same challenges:
they must keep their cubs out of danger and find huge quantities of food.
Each family will have to stack up enough fat this summer
to get them right through their winter sleep.
But each mother is going about it in very different ways.
So which cubs will get the best start in life?
Their story begins in January 每 the height of the ski season.
Fifteen hundred metres above Whistler town centre,
the ski and snowboarding runs are packed.
Each winter over a million visitors are attracted to these slopes despite the sub-zero cold.
Humans are not built for these temperatures, as this thermal image camera reveals.
Without exception, skiers are glowing bright greens and oranges
because they are much hotter than the blue surrounding slopes.
Despite their thick winter clothing all this heat is escaping into the atmosphere
每 they're losing heat fast.
Right next to the ski slopes,
all around North America,
other black bears are hibernating in dens beneath the snow,
protected from the cold by their thick, dense fur.
Thermal cameras can locate a bear den,
but to see under the snow, we need special tiny cameras.
And these reveal for the very first time newborn wild cubs in their natural den.
They weigh less than 500 grams
and need help to find their mother's rich milk.
She curls around them like a giant, furry anorak,
to protect them from their greatest threat 每 the cold.
No-one here is aware there's life under the slope.
Yet the bears sense the action overhead.
That's because they don't totally shut down like hibernating marmots.
Instead they wake up regularly and shuffle around the den.
From April bear mothers peer out to see if it's getting any warmer.
Soon they will all need to emerge from their winter hideaway.
Thanks to their mother's energy rich milk,
these cubs have already tripled their birth weight.
They spend their waking hours exploring the den and trying out bear hugs.
Wrestling is an important part of their development
it stimulates muscle growth so they'll be strong by the time they leave the den.
Their fur is already well developed
but it's not as efficient as their mother's.
While she's sussing-out spring
they are losing heat rapidly.
Fortunately she's not gone for long.
She's decided it's still too early to get out of their winter bed,
so she tucks them up again.
The bears that fed well last summer
are still producing enough milk for the cubs from their well-stocked bodies.
There's no need to venture out.
They have the luxury of a lie-in.
Not all bears are so lucky.
Spring is still weeks away,
but this one's been forced out before time.
It didn't fatten up enough, so now it's desperately hungry.
Natural food is still locked away under frozen ground,
so a half-built ski restaurant is its only hope.
At dawn there are no workers about,
but neither are there any lunchboxes to raid.
Hungry bears can be dangerous
and when the builders do arrive they call for help.
They don't want this bear to make a habit of coming here.
The bear expert sets a trap, and arms himself with a pepper-spray.
A direct hit.
The hot pepper is irritating, but does no lasting damage.
The bear heads back to the safety of the woods
but unless the thaw comes soon and exposes wild food,
it won't survive for long.
Even artificial snow won't prolong the winter ski season.
By the end of April nothing can stop the temperature rising.
Even the highest black runs, near the summit, are greening up.
Here our wilderness bear, Marissa, and her cubs are finally emerging from the den,
although she looks like she has that Monday morning feeling!
The cubs, on the other hand,
are full of bounce, and eager to explore this new world.
This is not the start of a carefree summer.
Marissa's first concern is to sniff out - and avoid - male bears.
A male will kill her cubs
because it's the only way he can re-trigger her breeding cycle.
This is the biggest threat the infants face＃
assuming they don't hurt themselves first.
Three years ago Marissa nearly lost cubs to a male,
so she's choosing to live very high up where there aren't many males about.
The family can just get on with notching up the calories.
The icy black runs are now carpeted in tender shoots.
However at this altitude the greens are growing in poor soil
and aren't very nutritious.
The cubs might be safer
but it will be much harder gaining weight than down in the foothills.
Down here Jess and her brown cubs have also woken up to spring.
The grass is greener but they don't have it all to themselves.
Many bears are joining them from their own winter hideaways.
Bears with more than just food on the brain.
As more and more bears surface there are face-offs
to remind each other who controls the best stretches of the former ski-runs.
Back rubbing can have more to do with laying claim to land than sorting out an itch.
The nursery slopes aren't just set up for inexperienced skiers.
They've been deliberately planted by the ski school,
with tasty grasses and clover to help wild bears get a good start.
It's a great place for Jess to fatten up her family,
but it's not somewhere she can relax.
The high quality food encourages a greater density of bears, including hostile males.
And already she's in trouble.
A male has picked up her scent.
The only hope for her family is to take to the trees.
He wants to mate with Jess,
but can only bring her into season by killing her cubs.
They must stay out of his reach.
Although he's heavy he's equipped with claws like grappling hooks,
and a head for heights.
It's an easy climb.
But the cubs are higher still
- clinging to the thinnest branches, which won't support the male's weight.
And Jess is blocking the way.
Reluctantly he retreats to find an easier conquest.
Ten percent of cubs die in their first year.
Jess is reunited with her cubs,
but this is unlikely to be the last time they're threatened.
She needs to get away from the cub-killing males
and the only place without this danger is further down the slopes again
- the uncharted streets of Whistler town itself.
It's a pivotal decision,
which will affect the cubs for the rest of their lives.
These bears are about to join life in the fast lane.
Town life may not be so bad.
There's the chance to scrounge from our high-fat diets.
Meals which certainly put clover on the side.
Jess and her cubs won't be alone.
Other drifters are arriving all the time.
The arrival of bears in spring is a timely reminder to the people of Whistler
to make sure their rubbish is cleared away.
Visitors must also remember to treat these wild bears with respect.
Bears will try anything for food.
They're strong, have a wicked sense of smell
and they're ingenious.
They see our urban landscape as a field of opportunity.
Jess and her cubs are soon on the make.
But will they learn enough tricks of this new trade
to fatten up in time for winter and survive the fresh dangers?
Back up near the mountain summit
Marissa's cubs are already noticeably thinner than Jess's.
She's successfully avoiding violent males
but is this high-altitude strategy also high-risk?
Food up here has a fraction of the fat and protein which Jess's cubs are getting.
Has Marissa scuppered her cubs' chances of finding enough to eat?
On the lower foothills, from where Jess fled to town,
big males are still keen to mate.
But not all females are as spooked as Jess.
Those without cubs are looking for a date.
Bringing your own mattress is one way to impress the girls.
But not her.
The male seems to get inspiration from the giant diggers preparing next season's ski runs.
He tries bulldozing his way into her affections.
It does the trick - the earth certainly moved around them.
Her fertilized eggs will only develop if she puts on enough weight before the winter.
Food, as always, is the bare necessity.
Whistler is full of tourists, even in summer.
As the crowds spill up the slopes
Marissa and her cubs become one of the main attractions.
Human contact and food could easily steer Marissa off her wild course.
But Whistler's visitors have been given strict instructions:
Do not feed the bears!
Marissa stumbles across a store of snowboarding kit.
The cubs are curious, as ever.
They're not in luck this time.
There's no food here so they stick with their natural way of life.
Several weeks later, as the evenings start to get chilly again,
Marissa's cubs are still dangerously underweight.
They won't survive winter at this rate.
But autumn triggers a change to their bodies and their behaviour,
which puts them into feeding over-drive.
This phase, known as hyperphagia,
means they can feed for up to 18 hours each day and yet never feel full.
Through the summer cubs have been ripping into logs in search of protein-rich ants.
and digging up tuber roots stuffed with carbohydrates.
But in autumn, when their bellies are constantly rumbling,
they go berry picking.
It may be slow food,
but two thousand berries an hour - from dawn to dusk
- will put on 16,000 calories a day.
And even that won't dent their appetites.
Berries are so important in this run-up to hibernation
that they keep picking come rain or shine.
This year it's a good berry crop.
At last Marissa's cubs are clocking up the kilos.
Back downtown, Jess and her cubs have made the most of the fast food mountain.
Even though they're huge, their bodies also change into pre-hibernation mode
每 they can't stop themselves wanting more and more.
And berries 每 ripening up in gardens and along trails
- are suddenly within easier reach than burgers.
Jess is now both street-wise and confident around humans.
With hunger now uppermost in a bear's mind
it's extremely unwise to cycle around with a sandwich in your mouth
每 you never know what may lie around the corner.
In autumn the tourists are thinning out.
There's less junk food about - at the very time bears are at their hungriest
So everything else is up for grabs.
Even if it doesn't taste as good as it smells.
What's worse Whistler has had a crackdown.
Bins have been bear-proofed,
and even the most nimble-fingered animals can't get their claws in.
But Jess won't give up that easily.
When Jess first arrived in Whistler she tried to avoid the public.
Now she's becoming more brazen.
Bear attacks are virtually unheard of in Whistler,
but this guy sensibly gives a bear some space.
If Jess keeps this up,
she'll be marked as a nuisance bear,
and that could spell disaster.
One way wise old urban bears stay out of trouble is by becoming nocturnal.
But destroying a Rowan tree in the Mayor's garden
won't help this bear stay unnoticed for long.
It slopes off towards the town centre,
to continue its love affair with food
- lured by the hypnotic smells of the restaurant district.
Sadly he's too late for a take-away.
Better luck round the back.
Although the dumpsters have been bear-proofed,
this one hasn't been shut.
An old pro has no trouble climbing in.
He gets a wholesome reward for persistence
so he'll be back tomorrow night for sure.
Dawn at the golf course
and there's more than water hazards here.
Jess and her cubs are breakfasting on the fairway.
With the odd sandwich on the side,
this lush lawn has become a vital food source.
And it's also one of the few places in Whistler without bear-proof bins.
Jess is getting more belligerent by the day.
And her cubs are learning from her every move.
The fatter of the two cubs attacks the golf bag.
He can smell food inside
and it will take more than a poorly aimed putter to distract him.
Smash and grab is now their way of life.
And at this time of year it's each cub for himself.
Reinforcements arrive just in time.
But the golf buggy merely moves the problem on.
Jess heads straight for the dumpsters
＃and is ready to take on all-comers.
She and her cubs are already more than fat enough for winter.
They don't need to eat any more
but they're driven by their greedy instincts.
Although these aren't even food bins 每 they're full of cardboard
- Jess can't resist climbing in.
They're all programmed to keep piling on the kilos.
Even when the dump truck arrives Jess is reluctant to leave.
Greedy bears have been known to be picked up and dropped into the trailer.
Whistler has its own force of bear police to deal with troublemakers.
But by the time they turn up, Jess has vanished.
Jess and the cubs are next sighted in a nearby garden.
They may be on the run,
but they're still eating.
The police have lost her trail
and can only fire warning shots into the air
in the hope that she'll be scared back into the hills.
But flimsy fireworks aren't enough to deter this hardened gang.
Patience is wearing a little thin
and the police decide to set a trap.
Problem bears are tempted into a cage.
But this year Jess is far from the only nuisance bear in town.
A fat male, possibly the one making the most of Whistler's nightlife,
can't resist the smell of sticky molasses.
He'll be released in a remote wilderness.
It's the short, sharp shock treatment.
But being dumped in a strange location in the territory of other bears,
when the race for food is at its most crucial, is a traumatic experience.
Suddenly the bear police get an emergency call.
They race to a half-built hotel complex
where a bear has somehow climbed up to the seventh floor and got stuck.
The builders think they've seen a cub, too.
This is not something covered in the health and safety manual
- no-one knows what to do.
The hotel lies in Jess' territory.
But is it her?
Has she taken her cubs on an adventure too far?
The bear police do carry live ammunition,
but it takes a desperate situation to use it.
This was that rare event: a cornered bear in a tight spot.
The police had no option but to shoot.
It turns out not to be Jess.
She and her cubs were scoffing berries through the drama.
The cubs are so fat they'll easily make it through the winter.
Their street urchin existence has paid off.
However they now show no fear of humans.
They've learned habits from their mum which are now deeply ingrained
and which might get them into big trouble.
With winter approaching,
Jess is taking her cubs out of Whistler, back up the slopes.
But will the smell of the streets draw them back next year?
High up in the mountains, Marissa has also pulled it off.
These cubs aren't as obese as the urban bears
but they're fat enough.
They've survived AND with their wild instincts intact.
They tolerate humans but do not rely on them.
Will this be better long-term?
The town bear and the country bear - both successful mothers.
But next summer, when the cubs are alone,
will the urban bears stay on the right side of the law
after they emerge from beneath the black run?
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