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In the far north of our planet
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00:00:46,832 --> 00:00:49,592
lie vast frozen lands...
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00:00:52,032 --> 00:00:54,232
...of snow-covered forests...
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00:00:55,432 --> 00:00:57,512
...and open tundra.
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00:01:00,472 --> 00:01:02,192
During the months to come,
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00:01:02,192 --> 00:01:04,112
they will be transformed
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00:01:04,112 --> 00:01:07,952
by the greatest
seasonal changes on Earth.
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00:01:10,952 --> 00:01:13,032
But now, in midwinter,
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00:01:13,032 --> 00:01:17,912
conditions are so hostile that
life seems all but impossible.
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00:01:24,112 --> 00:01:25,552
But...
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...not so.
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00:01:30,632 --> 00:01:34,192
In this world of extremes,
animals must go to
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00:01:34,192 --> 00:01:36,832
extraordinary lengths to survive.
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00:02:06,232 --> 00:02:08,912
February, northern Canada.
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00:02:11,672 --> 00:02:12,832
The harsh winter
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00:02:12,832 --> 00:02:16,512
has brought together
an extended family of wolves.
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00:02:18,672 --> 00:02:21,712
But this is no ordinary pack.
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There are 25 of them.
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00:02:32,192 --> 00:02:34,432
A super-pack,
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00:02:34,432 --> 00:02:37,232
one of the largest ever recorded.
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00:02:40,072 --> 00:02:42,392
They're ravenously hungry.
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They may have walked over 150 miles
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since they last had a meal.
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00:02:50,832 --> 00:02:54,872
But now, at last,
the lead male and female
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have picked up a trail.
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00:03:00,232 --> 00:03:04,392
It's been left by the only
substantial prey there is here
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at this time of year...
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00:03:10,512 --> 00:03:12,632
...bison.
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00:03:16,112 --> 00:03:18,112
They're formidable animals,
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00:03:18,112 --> 00:03:20,312
not easy to attack.
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00:03:22,872 --> 00:03:26,792
The bulls are ten times
the size of a wolf.
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00:03:28,792 --> 00:03:30,392
And they have horns
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00:03:30,392 --> 00:03:34,152
with which they could
rip any attacker to pieces.
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Gathered together and on guard,
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they appear invulnerable.
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The wolf pack's only chance...
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...is to try and break up the group
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and isolate one of them.
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00:04:08,833 --> 00:04:10,153
To do that,
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00:04:10,153 --> 00:04:13,673
they will have to work as a team
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00:04:13,673 --> 00:04:16,713
and try to start a stampede.
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00:04:36,793 --> 00:04:42,753
Even in thick snow,
bison can run at up to 35mph.
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The lead female wolf
leads the chase.
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00:04:50,193 --> 00:04:54,273
A kick from a bison's hind leg
could shatter her jaws.
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00:05:04,113 --> 00:05:08,633
But the pack must feed,
and they take turns to attack.
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00:05:13,713 --> 00:05:16,393
The bison head for cover.
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00:05:29,913 --> 00:05:32,993
The deep snow slows down
both attacked...
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...and attacker.
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00:05:41,673 --> 00:05:44,033
The herd splits into two.
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00:05:48,273 --> 00:05:51,233
But the wolves
are far from giving up.
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Hours pass.
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The thicker vegetation has turned
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a straightforward chase...
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00:06:05,913 --> 00:06:08,153
...into a deadly form...
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00:06:08,153 --> 00:06:09,993
...of hide...
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00:06:11,593 --> 00:06:13,393
...and seek.
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00:06:31,073 --> 00:06:32,193
Discovered.
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00:06:37,793 --> 00:06:41,193
The lead female manages
to chase the smaller group
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into the open.
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00:07:01,713 --> 00:07:05,993
But here the bison are able
to close ranks once again.
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00:07:12,673 --> 00:07:17,033
The leading wolves wait for
the rest of the pack to catch up.
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00:07:32,593 --> 00:07:36,833
The super-pack is once
again at full strength.
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00:07:41,233 --> 00:07:44,193
Suddenly, two of the bison panic.
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00:07:45,353 --> 00:07:48,393
It's just what the wolves
have been waiting for.
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00:08:03,273 --> 00:08:05,993
One of the bison is tiring.
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00:08:09,433 --> 00:08:12,193
The lead female
gets a grip on its flanks.
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The male joins her.
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00:08:27,953 --> 00:08:31,233
Together, they might be able
to bring it down.
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The rest of the wolves
catch up and help.
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00:08:57,713 --> 00:09:03,233
After eight long, hard hours,
the hunt is coming to an end.
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00:09:14,993 --> 00:09:18,273
Victory is sounded to summon
the rest of the pack.
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00:09:22,993 --> 00:09:26,753
A single wolf
wouldn't stand a chance
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00:09:26,753 --> 00:09:28,913
of making such a kill by itself.
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00:09:31,073 --> 00:09:32,953
The only way they have
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00:09:32,953 --> 00:09:36,953
of surviving the winter
is as a super-pack.
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00:09:52,633 --> 00:09:56,553
These snow-covered forests
encircle the Arctic
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from Scandinavia, through Russia,
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00:09:59,433 --> 00:10:03,233
to Alaska and the rest
of North America.
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00:10:06,193 --> 00:10:08,313
But close to the North Pole,
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00:10:08,313 --> 00:10:10,953
the winters are too long
and too cold
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00:10:10,953 --> 00:10:13,593
for even the hardiest of trees.
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00:10:15,593 --> 00:10:19,273
This is the tundra, and it stretches
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all the way to the shores
of the Arctic Ocean.
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00:10:31,313 --> 00:10:35,673
Here, conditions are even more
extreme than in the forests.
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00:10:40,193 --> 00:10:43,153
During the two months
of winter darkness,
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temperatures may fall
to minus 50 degrees Celsius.
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00:10:50,713 --> 00:10:52,913
The ground deep beneath the snow
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00:10:52,913 --> 00:10:57,113
has been frozen solid
since the last Ice Age.
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00:11:02,873 --> 00:11:05,593
There is no shelter of any kind.
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00:11:05,593 --> 00:11:08,353
Very few animals can survive here.
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00:11:13,113 --> 00:11:15,273
But this is one which does.
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An arctic fox.
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00:11:23,033 --> 00:11:25,793
It has the warmest fur
of any mammal.
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00:11:26,753 --> 00:11:27,993
And it can survive
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00:11:27,993 --> 00:11:30,753
blizzards that may rage
for days on end.
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00:11:35,193 --> 00:11:39,353
It must nonetheless
eventually eat something.
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00:11:40,673 --> 00:11:42,833
But how is that something
to be found
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00:11:42,833 --> 00:11:46,873
when you're all by yourself
in this desolation?
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00:12:00,274 --> 00:12:03,154
Arctic foxes are wanderers.
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00:12:05,234 --> 00:12:10,314
And they can travel over 2,000
miles, from Norway to Canada,
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in a constant search for food.
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00:12:30,034 --> 00:12:32,914
There might be something here.
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A patch of grass,
kept clear of the snow
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by the near-constant wind.
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00:12:40,154 --> 00:12:42,514
The slightest hint of scent
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00:12:42,514 --> 00:12:45,194
might indicate the presence of prey.
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00:12:52,394 --> 00:12:54,914
Less than a metre below the surface
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00:12:54,914 --> 00:12:58,194
may lie a hidden network of tunnels,
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shown here using
a special filming burrow.
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00:13:19,434 --> 00:13:21,834
Tiny arctic lemmings.
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00:13:24,594 --> 00:13:28,074
With a carpet of edible moss beneath
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00:13:28,074 --> 00:13:30,674
and a thick blanket of snow above...
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00:13:30,674 --> 00:13:33,994
...the lemmings spend
their entire winter
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00:13:33,994 --> 00:13:35,554
hidden below the surface.
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00:13:37,074 --> 00:13:39,554
And here they breed.
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For a hungry fox...
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...a group of lemmings
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could be a life-saving discovery...
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...if it can catch one.
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00:14:01,834 --> 00:14:06,434
Lemming burrows may
extend for up to 15 metres.
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00:14:14,234 --> 00:14:17,394
Pinpointing the position
of one of the inhabitants...
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00:14:18,634 --> 00:14:20,634
...is not easy.
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00:14:23,834 --> 00:14:27,074
An acute sense
of hearing is essential.
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00:14:31,274 --> 00:14:32,954
And the arctic fox
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has a special trick.
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00:14:48,394 --> 00:14:51,634
It doesn't always work first time.
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00:14:56,834 --> 00:14:59,714
And it does require dedication.
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00:15:20,554 --> 00:15:24,634
With less than 25 lemmings
per square mile of tundra...
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...you have to persevere.
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00:15:37,634 --> 00:15:40,274
And at last,
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one plump lemming.
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00:15:45,434 --> 00:15:49,394
The foxes' tenacity
and unique hunting skills
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enable them to find prey
which few others could catch.
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00:16:10,514 --> 00:16:13,594
On the tundra's southern fringes,
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00:16:13,594 --> 00:16:17,514
winter is significantly less severe.
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00:16:21,074 --> 00:16:24,434
The slight increase
in annual sunlight
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00:16:24,434 --> 00:16:28,274
has enabled a stunted forest
to develop.
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00:16:46,034 --> 00:16:50,314
It's the northern edge of the
world's largest woodland...
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00:16:51,274 --> 00:16:53,834
...the boreal forest.
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00:17:00,474 --> 00:17:04,354
750 billion trees.
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00:17:06,554 --> 00:17:09,514
A quarter of all the trees on Earth.
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00:17:12,474 --> 00:17:15,074
And it encircles the globe.
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00:17:17,354 --> 00:17:20,754
These forests store
twice as much carbon
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00:17:20,754 --> 00:17:25,154
as a tropical forest,
and they play a crucial part
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00:17:25,154 --> 00:17:28,794
in regulating the climate
of the entire planet.
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00:17:34,874 --> 00:17:37,114
One of the most remote tracts
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00:17:37,114 --> 00:17:40,274
stands in the far east of Siberia.
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00:17:45,594 --> 00:17:49,594
It's cut off from the rest of
the world by towering peaks...
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00:17:50,714 --> 00:17:53,554
...and precipitous valleys.
150
00:17:57,434 --> 00:18:00,394
And it is the last stronghold
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00:18:00,394 --> 00:18:03,594
of the world's rarest big cat.
152
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The Amur leopard.
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00:18:24,434 --> 00:18:27,834
Hunting has brought it
close to extinction.
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00:18:27,834 --> 00:18:31,714
Only 120 are left in the wild.
155
00:18:34,874 --> 00:18:39,794
And this is one of the very
few ever to be caught on film.
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00:18:52,354 --> 00:18:57,114
Each must patrol a territory
of over 100 square miles
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00:18:57,114 --> 00:18:59,274
to find enough to eat.
158
00:19:04,834 --> 00:19:06,914
In the cold of March,
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00:19:06,914 --> 00:19:10,194
prey is at its most scarce.
160
00:19:22,394 --> 00:19:25,474
But leopards are clever opportunists
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00:19:25,474 --> 00:19:28,114
and watch for clues.
162
00:19:31,835 --> 00:19:33,115
Crows.
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00:19:34,115 --> 00:19:36,555
They too are looking for food.
164
00:19:39,395 --> 00:19:43,555
And their calls tell him
that they've found something.
165
00:19:59,715 --> 00:20:03,795
But he is not
the only predator here.
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00:20:05,075 --> 00:20:09,115
On one of the trees,
the marks of huge claws,
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00:20:09,115 --> 00:20:10,835
ten centimetres long.
168
00:20:14,915 --> 00:20:18,715
They've been made
by a hunter twice his size...
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00:20:25,795 --> 00:20:28,715
...a Siberian tiger.
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00:20:31,395 --> 00:20:34,915
Fewer than 500 remain in the wild.
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These two rare big cats
are sharing the same territory.
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00:20:51,635 --> 00:20:53,635
And fixed remote cameras
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00:20:53,635 --> 00:20:57,435
show that they even use
exactly the same trails.
174
00:21:02,635 --> 00:21:06,115
But leopards know
they must be careful.
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00:21:11,475 --> 00:21:15,835
Siberian tigers are the
biggest of all the big cats,
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00:21:15,835 --> 00:21:18,395
and could kill a leopard...
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00:21:21,155 --> 00:21:23,235
...should they ever meet.
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00:21:34,515 --> 00:21:35,635
In winter,
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00:21:35,635 --> 00:21:39,915
many forest animals
rely on carrion for food.
180
00:21:44,635 --> 00:21:46,875
And that includes leopards.
181
00:21:57,075 --> 00:22:00,195
But he can't let down his guard.
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00:22:11,915 --> 00:22:13,835
The crows that led him here...
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00:22:13,835 --> 00:22:16,955
...may also have alerted the tiger.
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00:22:47,875 --> 00:22:49,355
The crows are disturbed.
185
00:22:51,035 --> 00:22:53,955
Another mouthful might be risky.
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00:23:09,595 --> 00:23:13,275
Survival sometimes
depends on knowing
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00:23:13,275 --> 00:23:14,795
when to leave.
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00:23:22,795 --> 00:23:26,035
Only a few choose
to take their chances here
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00:23:26,035 --> 00:23:28,515
in the depths of winter.
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00:23:29,875 --> 00:23:35,275
Elsewhere, vast swathes of
the forest remain eerily empty.
191
00:23:39,555 --> 00:23:43,915
Above, there is
an otherworldly light show...
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00:23:48,795 --> 00:23:51,235
...the aurora borealis.
193
00:23:57,835 --> 00:23:59,635
High in the sky,
194
00:23:59,635 --> 00:24:03,275
electrically charged
solar particles from space
195
00:24:03,275 --> 00:24:05,915
collide with the Earth's atmosphere
196
00:24:05,915 --> 00:24:08,835
and create this ethereal display.
197
00:24:21,075 --> 00:24:26,995
Meanwhile, in Canada, through
the six long months of winter,
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00:24:26,995 --> 00:24:31,875
life below ground
is biding its time.
199
00:24:37,595 --> 00:24:41,195
The world's most northerly turtle...
200
00:24:42,955 --> 00:24:44,395
...the painted turtle...
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00:24:44,395 --> 00:24:48,155
...seen here
in a special filming chamber.
202
00:24:49,475 --> 00:24:52,355
They hatched last autumn
but have remained
203
00:24:52,355 --> 00:24:55,875
in a state of suspended
animation ever since.
204
00:24:58,795 --> 00:25:01,435
Their hearts have stopped beating...
205
00:25:02,795 --> 00:25:05,315
...and only their brains
have remained active,
206
00:25:05,315 --> 00:25:07,755
and even then, only very faintly.
207
00:25:11,275 --> 00:25:14,715
Painted turtles wait underground
208
00:25:14,715 --> 00:25:17,195
for this most important
of moments...
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00:25:27,035 --> 00:25:30,355
...the arrival of spring.
210
00:25:44,955 --> 00:25:48,355
In April, the strengthening sunshine
211
00:25:48,355 --> 00:25:52,355
triggers a miraculous
transformation.
212
00:26:06,755 --> 00:26:10,995
The turtles' body temperature
rises just above freezing...
213
00:26:16,675 --> 00:26:20,435
...and their hearts
start to beat once more.
214
00:26:35,635 --> 00:26:38,435
Slowly, they return to life.
215
00:26:40,395 --> 00:26:45,555
Thanks to this extraordinary
adaptation, these young turtles
216
00:26:45,555 --> 00:26:49,315
get a valuable head start
in spring...
217
00:26:59,315 --> 00:27:02,955
...and are one of the first
to emerge, ready to take
218
00:27:02,955 --> 00:27:06,635
full advantage of the forest's
renewed abundance.
219
00:27:14,595 --> 00:27:18,395
In just a matter of weeks,
the vast northern forests
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00:27:18,396 --> 00:27:20,476
flush green.
221
00:27:35,836 --> 00:27:41,716
For Siberia's big cats, each
spring could bring new hope.
222
00:27:45,076 --> 00:27:46,556
Cubs.
223
00:27:48,756 --> 00:27:51,636
Each of them
increases the chance that,
224
00:27:51,636 --> 00:27:56,556
even at this very late stage,
both species might recover.
225
00:28:08,996 --> 00:28:13,156
By June, the northern forests
are full of life.
226
00:28:22,196 --> 00:28:26,876
But several thousands of miles
further north, in the tundra,
227
00:28:26,876 --> 00:28:29,836
the spring thaw
is only just beginning.
228
00:28:36,996 --> 00:28:40,156
When it does,
under 24-hour daylight,
229
00:28:40,156 --> 00:28:43,356
its impact is even more extreme.
230
00:28:48,996 --> 00:28:51,756
Five million square miles of snow
231
00:28:51,756 --> 00:28:54,676
disappear in a matter of days.
232
00:29:05,276 --> 00:29:08,596
Ten centimetres beneath
the surface of the ground,
233
00:29:08,596 --> 00:29:13,036
a snow queen is waiting
to make her appearance.
234
00:29:18,356 --> 00:29:21,556
A Lapland bumblebee.
235
00:29:22,756 --> 00:29:25,076
She's barely alive.
236
00:29:27,116 --> 00:29:31,596
All the other members of her colony
were killed by the cold.
237
00:29:33,956 --> 00:29:37,956
She survived,
as bumblebee queens do,
238
00:29:37,956 --> 00:29:42,916
thanks to her larger size,
her particularly thick fur,
239
00:29:42,916 --> 00:29:47,436
and a natural antifreeze
that she has in her body.
240
00:29:58,796 --> 00:30:01,516
As temperatures continue to rise,
241
00:30:01,516 --> 00:30:04,316
she begins to thaw.
242
00:30:15,596 --> 00:30:18,236
She vibrates her flight muscles,
243
00:30:18,236 --> 00:30:20,516
which raises her body temperature
244
00:30:20,516 --> 00:30:25,116
to over 30 degrees Celsius
in just six minutes.
245
00:30:27,596 --> 00:30:30,916
There is no time to lose.
246
00:30:34,196 --> 00:30:38,116
She must now create
an entire colony.
247
00:30:46,476 --> 00:30:49,476
First, the queen must find
a drink of nectar
248
00:30:49,476 --> 00:30:51,476
to regain her strength...
249
00:30:55,196 --> 00:30:57,556
...travelling as much as
three miles a day
250
00:30:57,556 --> 00:31:00,636
to find the flowers
from which to collect it.
251
00:31:10,036 --> 00:31:11,916
She works tirelessly.
252
00:31:14,636 --> 00:31:16,876
As well as high-energy nectar...
253
00:31:18,836 --> 00:31:21,156
...there's pollen to be gathered.
254
00:31:34,676 --> 00:31:40,316
Back underground, she uses the
pollen to build a waxy cocoon.
255
00:31:42,156 --> 00:31:45,916
And in it,
she deposits the tiny eggs.
256
00:31:49,516 --> 00:31:52,476
Had she laid them
directly on the frozen ground,
257
00:31:52,476 --> 00:31:54,596
the cold would have killed them.
258
00:31:54,596 --> 00:31:57,156
And now she warms them
259
00:31:57,156 --> 00:31:59,156
by pulsating her body.
260
00:32:08,716 --> 00:32:11,236
She has also constructed
a little pot
261
00:32:11,236 --> 00:32:13,316
in which she stores nectar
262
00:32:13,316 --> 00:32:16,516
to provide her with a drink
when she needs it.
263
00:32:22,356 --> 00:32:24,516
For the next three weeks...
264
00:32:25,476 --> 00:32:27,076
...this single mother
265
00:32:27,076 --> 00:32:30,276
works around the clock,
gathering nectar
266
00:32:30,276 --> 00:32:32,036
to top up her pot...
267
00:32:40,676 --> 00:32:42,476
...and vibrating her body
268
00:32:42,476 --> 00:32:45,956
to prevent her developing young
from freezing to death.
269
00:32:57,676 --> 00:33:01,796
Eventually, a new generation of bees
270
00:33:01,796 --> 00:33:04,356
starts to emerge.
271
00:33:10,996 --> 00:33:15,116
She leads each young
worker to her honey pot
272
00:33:15,116 --> 00:33:17,796
and encourages it to drink.
273
00:33:24,476 --> 00:33:27,956
By the end of the following week,
274
00:33:27,956 --> 00:33:31,556
the number in her little colony
has increased to eight.
275
00:33:33,956 --> 00:33:36,956
Her timing has been perfect.
276
00:33:43,036 --> 00:33:46,116
The tundra is now in full bloom.
277
00:33:53,756 --> 00:33:57,076
And the bumblebee families
help to pollinate
278
00:33:57,076 --> 00:34:00,676
the largest wild-flower
meadow on Earth.
279
00:34:15,476 --> 00:34:20,236
But the summer here is one
of the shortest on the planet.
280
00:34:20,236 --> 00:34:23,076
And all of the tundra's residents
281
00:34:23,076 --> 00:34:25,596
are now racing to breed.
282
00:34:28,996 --> 00:34:33,676
Alaskan snowy owls have
a brood of six fluffy chicks
283
00:34:33,676 --> 00:34:37,036
and only eight weeks
in which to raise them.
284
00:34:45,676 --> 00:34:50,076
The parents provide them
with 30 lemmings a day...
285
00:34:51,476 --> 00:34:54,076
...for the chicks will need
to triple their weight
286
00:34:54,076 --> 00:34:56,196
before they reach independence.
287
00:35:06,037 --> 00:35:10,637
Unusually for an owl,
snowies hunt by day.
288
00:35:15,117 --> 00:35:17,237
And over the next two weeks,
289
00:35:17,237 --> 00:35:20,917
they take full advantage of
the Arctic's continuous light.
290
00:35:27,237 --> 00:35:33,397
But this morning, the female
returns to an empty nest.
291
00:35:39,437 --> 00:35:42,077
Her chicks are nowhere to be seen.
292
00:35:52,037 --> 00:35:54,037
They're hiding.
293
00:35:59,237 --> 00:36:03,517
They're so big, the whole group
might be spotted by predators,
294
00:36:03,517 --> 00:36:07,397
so they have scattered
across the tundra.
295
00:36:13,597 --> 00:36:18,037
But that makes feeding them
all much harder work.
296
00:36:29,637 --> 00:36:31,757
Over 600 meals later,
297
00:36:31,757 --> 00:36:34,397
the parents' lab ours
are starting to pay off...
298
00:36:36,477 --> 00:36:40,597
...as the chicks stretch
their newly developed wings.
299
00:36:50,197 --> 00:36:54,517
Just a month is left
before winter returns.
300
00:37:12,077 --> 00:37:13,557
Two weeks more,
301
00:37:13,557 --> 00:37:16,237
and their transformation
is almost complete.
302
00:37:18,357 --> 00:37:20,837
The chicks' wings
might at last be able
303
00:37:20,837 --> 00:37:24,037
to do more than just
lift them from the ground.
304
00:37:29,917 --> 00:37:31,597
Getting there!
305
00:37:37,997 --> 00:37:39,957
Keep going!
306
00:37:43,917 --> 00:37:45,437
Airborne!
307
00:37:45,437 --> 00:37:49,117
The youngsters are ready
for independence.
308
00:37:51,557 --> 00:37:55,437
And the exhausted parents
can take a well-earned rest.
309
00:38:01,477 --> 00:38:04,517
The tundra has come to life
once again.
310
00:38:06,677 --> 00:38:10,117
But in the longer term,
its very foundations
311
00:38:10,117 --> 00:38:12,437
are now at risk.
312
00:38:26,477 --> 00:38:29,677
The ground itself is giving way.
313
00:38:42,597 --> 00:38:48,437
In some places, it's dropped
by more than 60 metres.
314
00:38:52,477 --> 00:38:56,517
Grasslands that once supported
thousands of different species
315
00:38:56,517 --> 00:38:59,437
have become wastelands.
316
00:39:06,597 --> 00:39:09,197
Arctic temperatures are rising
317
00:39:09,197 --> 00:39:12,357
as a consequence of climate change.
318
00:39:16,917 --> 00:39:19,877
The deep soil
which has been frozen solid
319
00:39:19,877 --> 00:39:23,317
for thousands of years,
the permafrost,
320
00:39:23,317 --> 00:39:27,437
is now thawing at a rate
never witnessed before.
321
00:39:33,517 --> 00:39:35,477
Without the ice to bind it together,
322
00:39:35,477 --> 00:39:38,157
the ground becomes unstable.
323
00:39:44,877 --> 00:39:48,557
In Canada, thousands of
tonnes of the tundra
324
00:39:48,557 --> 00:39:51,117
have collapsed in a matter of weeks.
325
00:40:04,837 --> 00:40:09,117
And in Siberia,
huge scars are appearing.
326
00:40:15,317 --> 00:40:19,357
By the end of the century,
an area of Arctic permafrost
327
00:40:19,357 --> 00:40:21,917
one third of the size of Europe
328
00:40:21,917 --> 00:40:23,997
could have thawed.
329
00:40:29,517 --> 00:40:30,997
The warming of the tundra
330
00:40:30,997 --> 00:40:34,517
is having a profound impact
on its wildlife.
331
00:40:37,037 --> 00:40:42,357
For millennia, caribou
have made annual migrations.
332
00:40:47,277 --> 00:40:48,597
Every summer,
333
00:40:48,597 --> 00:40:51,957
driven by the seasonal
changes of the far north
334
00:40:51,957 --> 00:40:55,637
and following
long-established pathways,
335
00:40:55,637 --> 00:40:59,957
they have trekked
almost 400 miles north.
336
00:41:16,997 --> 00:41:23,237
This herd alone in north-east
Alaska numbers over 200,000.
337
00:41:31,997 --> 00:41:33,397
Their destination
338
00:41:33,397 --> 00:41:35,357
is a vast wilderness
339
00:41:35,357 --> 00:41:39,237
known as the Arctic
National Wildlife Refuge.
340
00:41:50,757 --> 00:41:54,477
These summer pastures
provide rich grazing,
341
00:41:54,477 --> 00:41:58,597
just what's needed
to raise newborn calves.
342
00:42:07,837 --> 00:42:10,877
This one, fattening up
on its mother's milk,
343
00:42:10,877 --> 00:42:14,197
would normally double its weight
in just a few weeks.
344
00:42:24,677 --> 00:42:28,517
But now grazing time
is being disrupted.
345
00:42:34,997 --> 00:42:37,997
In summer, the tundra
becomes waterlogged.
346
00:42:41,197 --> 00:42:44,477
These are excellent
breeding conditions
347
00:42:44,477 --> 00:42:47,757
for mosquitoes
and other biting insects.
348
00:42:56,158 --> 00:42:58,278
But as the climate warms,
349
00:42:58,278 --> 00:43:01,998
there are concerns
that insects will breed earlier
350
00:43:01,998 --> 00:43:04,878
and eventually reach
plague proportions
351
00:43:04,878 --> 00:43:07,358
just as the caribou need to feed.
352
00:43:11,558 --> 00:43:13,518
Individual animals could lose
353
00:43:13,518 --> 00:43:18,278
a quarter of a pint of blood
a day to biting insects.
354
00:43:24,038 --> 00:43:27,158
So the caribou may
end their grazing early
355
00:43:27,158 --> 00:43:31,318
and head for cooler,
mosquito-free pastures.
356
00:43:39,398 --> 00:43:41,158
But to get to such places,
357
00:43:41,158 --> 00:43:45,238
they will have to cross rivers
swollen by seasonal runoff.
358
00:44:00,118 --> 00:44:04,718
For a young calf, a deep river
crossing is very dangerous.
359
00:44:10,878 --> 00:44:14,598
He does what he can
to stay close to his mother.
360
00:44:24,358 --> 00:44:26,718
But he doesn't have the strength
361
00:44:26,718 --> 00:44:29,398
to resist the fast-moving current.
362
00:45:22,038 --> 00:45:25,318
He is one of the lucky ones.
363
00:45:29,478 --> 00:45:32,078
Reunited with his mother,
364
00:45:32,078 --> 00:45:35,758
he can continue
on his journey with the herd.
365
00:45:44,878 --> 00:45:48,318
But other calves
are less fortunate...
366
00:45:50,958 --> 00:45:54,918
...and must now
fend for themselves.
367
00:46:06,278 --> 00:46:10,438
Some are too exhausted
to take another step.
368
00:46:18,478 --> 00:46:21,918
But this is not a safe place
to take a rest.
369
00:46:47,278 --> 00:46:49,038
Grizzly bears.
370
00:46:53,158 --> 00:46:54,678
For the past few weeks,
371
00:46:54,678 --> 00:46:57,718
there has been little food
for them on the tundra.
372
00:47:00,438 --> 00:47:03,318
And this one is extremely hungry.
373
00:47:19,678 --> 00:47:23,118
He's looking for the weak and weary.
374
00:47:32,798 --> 00:47:35,718
And he's found one...
375
00:47:47,718 --> 00:47:49,958
...too tired to flee...
376
00:47:53,118 --> 00:47:55,478
...and too weak to resist.
377
00:48:07,118 --> 00:48:08,838
The herd's finally reached
378
00:48:08,838 --> 00:48:11,278
the northern limits of its range.
379
00:48:16,318 --> 00:48:19,758
These coastal pastures
bordering the Arctic Ocean
380
00:48:19,758 --> 00:48:22,638
remain cool enough to provide relief
381
00:48:22,638 --> 00:48:24,758
from the swarms of insects.
382
00:48:29,638 --> 00:48:33,398
Mothers and calves
can finally feed in peace.
383
00:48:40,518 --> 00:48:44,998
For now, this
immense herd is stable.
384
00:48:47,158 --> 00:48:51,878
But in the long term,
its survival is now uncertain.
385
00:48:57,598 --> 00:49:00,598
The seasonal extremes
of the far north
386
00:49:00,598 --> 00:49:04,238
have always tested
its inhabitants to the limits.
387
00:49:06,438 --> 00:49:09,238
But climate change
could present them
388
00:49:09,238 --> 00:49:11,398
with one challenge too many.
389
00:49:13,318 --> 00:49:16,398
Only if we can mitigate its effects
390
00:49:16,398 --> 00:49:19,118
will the remarkable wildlife here
391
00:49:19,118 --> 00:49:22,158
stand a chance of survival.
392
00:49:40,998 --> 00:49:43,958
Filming in the extremes
of the far north...
393
00:49:44,998 --> 00:49:47,998
...the team's greatest
challenge was to capture
394
00:49:47,998 --> 00:49:50,958
the epic showdown between
super-packs of wolves
395
00:49:50,958 --> 00:49:53,558
and bison in midwinter.
396
00:49:56,878 --> 00:49:58,158
The crew travelled to
397
00:49:58,158 --> 00:50:01,118
Wood Buffalo National Park
in northern Canada,
398
00:50:01,118 --> 00:50:04,958
a remote wilderness
the size of Switzerland.
399
00:50:08,198 --> 00:50:10,638
To stand a chance
of filming this drama,
400
00:50:10,638 --> 00:50:12,758
they must take to the skies.
401
00:50:14,198 --> 00:50:15,558
Drawing on local knowledge,
402
00:50:15,558 --> 00:50:19,158
pilot Matt Erhardt
helps to pinpoint
403
00:50:19,158 --> 00:50:21,358
one of the last
free-roaming herds of bison
404
00:50:21,358 --> 00:50:24,038
and the wolves that
specialise in hunting them.
405
00:50:27,678 --> 00:50:29,798
Some of the wolves
have run forwards.
406
00:50:29,798 --> 00:50:31,718
Just have all your kit
ready to go.
407
00:50:33,998 --> 00:50:35,398
With a positive sighting,
408
00:50:35,399 --> 00:50:37,479
it's time to mobilise the film crew.
409
00:50:39,839 --> 00:50:42,919
Cameraman Jamie McPherson
has rigged the helicopter
410
00:50:42,919 --> 00:50:45,679
with a gyrostabilised camera system,
411
00:50:45,679 --> 00:50:49,039
enabling him to capture
rock-steady images
412
00:50:49,039 --> 00:50:50,559
from a safe distance.
413
00:50:50,559 --> 00:50:52,479
You'd think filming
from a helicopter's easy,
414
00:50:52,479 --> 00:50:54,439
because you can just
fly around and film stuff.
415
00:50:54,439 --> 00:50:56,119
But you've got to be
incredibly careful,
416
00:50:56,119 --> 00:50:57,439
not influence the behaviour,
417
00:50:57,439 --> 00:50:58,959
not scare the wolves or the bison.
418
00:51:03,399 --> 00:51:05,759
There we go.
Yeah, that is them.
419
00:51:06,759 --> 00:51:08,159
It's a big pack. Yeah.
420
00:51:09,999 --> 00:51:12,039
They're really chilled out
with the helicopter.
421
00:51:12,039 --> 00:51:13,319
Really encouraging.
422
00:51:15,559 --> 00:51:17,799
But before Jamie can start filming,
423
00:51:17,799 --> 00:51:21,079
the chopper must first drop
the accompanying ground crew.
424
00:51:21,079 --> 00:51:23,279
Good luck. OK.
425
00:51:28,879 --> 00:51:30,279
We got put down
426
00:51:30,279 --> 00:51:31,799
in this vast open space,
427
00:51:31,799 --> 00:51:34,879
and now we're going to
try and hike in and see
428
00:51:34,879 --> 00:51:36,199
if we can get close to them,
429
00:51:36,199 --> 00:51:38,079
or hopefully they'll
get close to us.
430
00:51:39,199 --> 00:51:43,559
To intercept the pack, the team
must scramble into position.
431
00:51:47,479 --> 00:51:49,999
But trudging through
knee-deep snow
432
00:51:49,999 --> 00:51:51,879
is hard going.
433
00:51:56,359 --> 00:51:58,839
Every time I catch up with
Justin, he just keeps on going.
434
00:51:58,839 --> 00:52:00,279
He's a machine!
435
00:52:07,079 --> 00:52:08,199
Yeah, go ahead, Matt.
436
00:52:08,199 --> 00:52:09,959
They're starting to head
437
00:52:09,959 --> 00:52:11,719
a little bit towards
the north-west,
438
00:52:11,719 --> 00:52:13,879
so they're starting to
move away from you.
439
00:52:15,159 --> 00:52:16,599
Oh, Goddamn it!
440
00:52:17,959 --> 00:52:20,359
The ground crew
will have to dig deep
441
00:52:20,359 --> 00:52:23,199
if they're to film
the fleet-footed wolves.
442
00:52:28,079 --> 00:52:29,479
Over the following week,
443
00:52:29,479 --> 00:52:32,119
Jamie manages to track
the wolf pack
444
00:52:32,119 --> 00:52:34,279
from the comfort
of the helicopter...
445
00:52:35,279 --> 00:52:37,279
...while down on the ground,
446
00:52:37,279 --> 00:52:40,879
Justin and Will are having
a tougher time of it.
447
00:52:40,879 --> 00:52:45,759
Ohhh! It's really
incredibly awkward getting around.
448
00:52:45,759 --> 00:52:48,599
Even lunch offers
little consolation.
449
00:52:48,599 --> 00:52:49,839
It's frozen bread,
450
00:52:49,839 --> 00:52:52,799
frozen Brie and frozen pickle.
451
00:52:53,799 --> 00:52:55,119
And with no wolf activity
452
00:52:55,119 --> 00:52:56,279
visible from the air,
453
00:52:56,279 --> 00:52:58,839
Jamie is soon grounded.
454
00:52:58,839 --> 00:53:00,919
Yeah, I'm just
looking for an update.
455
00:53:06,399 --> 00:53:08,599
Great...
456
00:53:11,239 --> 00:53:13,639
The winter weather
takes a turn for the worse.
457
00:53:13,639 --> 00:53:16,279
It's snowing, and it's at
a temperature where it could
458
00:53:16,279 --> 00:53:18,079
potentially stick to the blades
459
00:53:18,079 --> 00:53:20,159
and become really dangerous.
460
00:53:20,159 --> 00:53:24,479
For the next few days, the crew
are forced to sit it out.
461
00:53:30,119 --> 00:53:32,399
Finally, the skies clear.
462
00:53:33,359 --> 00:53:36,159
But after nearly three weeks
on location,
463
00:53:36,159 --> 00:53:38,479
there's precious little
filming time left.
464
00:53:39,599 --> 00:53:41,999
We've got one last shot
465
00:53:41,999 --> 00:53:44,119
to get what we're looking for.
466
00:53:44,119 --> 00:53:47,399
And just hoping that it comes
together at the last minute.
467
00:53:54,519 --> 00:53:56,079
There, there's the trail there,
468
00:53:56,079 --> 00:53:58,079
so they're on the west side
of that trail there.
469
00:54:01,599 --> 00:54:03,919
Soon enough, they find the bison,
470
00:54:03,919 --> 00:54:05,879
along with wolves
471
00:54:05,879 --> 00:54:07,639
who appear to be in hunting mode.
472
00:54:08,839 --> 00:54:11,679
The spotter plane just found
the wolves with the bison,
473
00:54:11,679 --> 00:54:14,039
so we're scrambling to get
there as quick as we can.
474
00:54:35,999 --> 00:54:37,999
There's something about
475
00:54:37,999 --> 00:54:41,559
being in the presence of prey
and predator on the ground
476
00:54:41,559 --> 00:54:43,919
like this which is very special.
477
00:54:45,079 --> 00:54:49,399
Justin is in prime position
to capture the showdown.
478
00:54:57,039 --> 00:54:58,279
As a chase begins,
479
00:54:58,279 --> 00:55:01,839
Jamie picks up the action
from the air.
480
00:55:08,839 --> 00:55:11,519
It'd be amazing
if we could get round that. OK.
481
00:55:15,919 --> 00:55:17,719
In a stop-start pursuit
482
00:55:17,719 --> 00:55:19,119
lasting an entire day,
483
00:55:19,119 --> 00:55:23,359
Jamie manages to record
the full jaw-dropping drama.
484
00:55:26,079 --> 00:55:27,719
They've definitely got
that female.
485
00:55:27,719 --> 00:55:29,719
I think they're going to
bring it down.
486
00:55:33,959 --> 00:55:37,079
Perfect, Jim. We got it.
487
00:55:38,079 --> 00:55:40,039
With the hunt nearly over,
488
00:55:40,039 --> 00:55:42,959
the crew reposition Justin
once more.
489
00:55:52,559 --> 00:55:56,519
We got on the ground
just in time to capture
490
00:55:56,519 --> 00:55:58,519
from a really far distance
491
00:55:58,519 --> 00:56:01,719
the last moments
of the bison's life.
492
00:56:04,639 --> 00:56:06,879
There's a moment of confliction
493
00:56:06,879 --> 00:56:10,319
between your loyalty
for each animal.
494
00:56:10,319 --> 00:56:15,679
One is filled with a mixture of
both celebration for the wolves
495
00:56:15,679 --> 00:56:20,119
but a sadness. Both exist
somehow simultaneously.
496
00:56:25,399 --> 00:56:28,519
Bearing witness to this
rarely seen age-old battle
497
00:56:28,519 --> 00:56:32,239
between predator and prey
leaves the crew
498
00:56:32,239 --> 00:56:35,439
with an appreciation of
just how challenging life is
499
00:56:35,439 --> 00:56:38,519
in the frozen extremes
of the far north.
500
00:56:48,119 --> 00:56:49,359
Next time...
501
00:56:50,759 --> 00:56:53,319
...we meet the scientists
and people...
502
00:56:54,919 --> 00:56:57,159
...who are dedicating their lives
503
00:56:57,159 --> 00:56:59,759
to understanding
the changes taking place...
504
00:57:02,079 --> 00:57:04,519
...across our frozen planet.
505
00:57:05,959 --> 00:57:09,479
Changes that'll impact
the lives of each...
506
00:57:10,599 --> 00:57:11,919
...and every one of us.
507
00:57:14,679 --> 00:57:16,759
The Open University has
produced a poster
508
00:57:16,759 --> 00:57:21,209
exploring how animals adapt to life
in the world's coldest environments.
509
00:57:21,235 --> 00:57:27,125
To order your free copy,
please call 0300 303 0553,
510
00:57:27,157 --> 00:57:32,267
or go to bbc.co.uk/frozenplanet2
511
00:57:32,297 --> 00:57:34,437
...and follow the links
to The Open University.
36724
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