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In the far north of our planet
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00:00:40,760 --> 00:00:43,520
lie vast frozen lands...
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00:00:45,960 --> 00:00:48,160
...of snow-covered forests...
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00:00:49,360 --> 00:00:51,440
...and open tundra.
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00:00:54,400 --> 00:00:56,120
During the months to come,
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00:00:56,120 --> 00:00:58,040
they will be transformed
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00:00:58,040 --> 00:01:01,880
by the greatest
seasonal changes on Earth.
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00:01:04,880 --> 00:01:06,960
But now, in midwinter,
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00:01:06,960 --> 00:01:11,840
conditions are so hostile that
life seems all but impossible.
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00:01:18,040 --> 00:01:19,480
But...
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...not so.
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00:01:24,560 --> 00:01:28,120
In this world of extremes,
animals must go to
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00:01:28,120 --> 00:01:30,760
extraordinary lengths to survive.
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00:02:00,160 --> 00:02:02,840
February, northern Canada.
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00:02:05,600 --> 00:02:06,760
The harsh winter
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00:02:06,760 --> 00:02:10,440
has brought together
an extended family of wolves.
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00:02:12,600 --> 00:02:15,640
But this is no ordinary pack.
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There are 25 of them.
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00:02:26,120 --> 00:02:28,360
A super-pack,
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one of the largest ever recorded.
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00:02:34,000 --> 00:02:36,320
They're ravenously hungry.
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They may have walked over 150 miles
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00:02:40,840 --> 00:02:43,280
since they last had a meal.
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00:02:44,760 --> 00:02:48,800
But now, at last,
the lead male and female
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00:02:48,800 --> 00:02:50,960
have picked up a trail.
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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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00:03:04,440 --> 00:03:06,560
...bison.
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00:03:10,040 --> 00:03:12,040
They're formidable animals,
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00:03:12,040 --> 00:03:14,240
not easy to attack.
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00:03:16,800 --> 00:03:20,720
The bulls are ten times
the size of a wolf.
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00:03:22,720 --> 00:03:24,320
And they have horns
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00:03:24,320 --> 00:03:28,080
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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00:04:02,760 --> 00:04:04,080
To do that,
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00:04:04,080 --> 00:04:07,600
they will have to work as a team
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00:04:07,600 --> 00:04:10,640
and try to start a stampede.
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00:04:30,720 --> 00:04:36,680
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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00:04:44,120 --> 00:04:48,200
A kick from a bison's hind leg
could shatter her jaws.
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00:04:58,040 --> 00:05:02,560
But the pack must feed,
and they take turns to attack.
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The bison head for cover.
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00:05:23,840 --> 00:05:26,920
The deep snow slows down
both attacked...
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...and attacker.
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00:05:35,600 --> 00:05:37,960
The herd splits into two.
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00:05:42,200 --> 00:05:45,160
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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...into a deadly form...
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00:06:02,080 --> 00:06:03,920
...of hide...
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...and seek.
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Discovered.
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00:06:31,720 --> 00:06:35,120
The lead female manages
to chase the smaller group
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00:06:35,120 --> 00:06:36,720
into the open.
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00:06:55,640 --> 00:06:59,920
But here the bison are able
to close ranks once again.
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00:07:06,600 --> 00:07:10,960
The leading wolves wait for
the rest of the pack to catch up.
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The super-pack is once
again at full strength.
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Suddenly, two of the bison panic.
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00:07:39,280 --> 00:07:42,320
It's just what the wolves
have been waiting for.
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00:07:57,200 --> 00:07:59,920
One of the bison is tiring.
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00:08:03,360 --> 00:08:06,120
The lead female
gets a grip on its flanks.
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The male joins her.
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00:08:21,880 --> 00:08:25,160
Together, they might be able
to bring it down.
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00:08:34,680 --> 00:08:37,680
The rest of the wolves
catch up and help.
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00:08:51,640 --> 00:08:57,160
After eight long, hard hours,
the hunt is coming to an end.
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00:09:08,920 --> 00:09:12,200
Victory is sounded to summon
the rest of the pack.
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A single wolf
wouldn't stand a chance
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of making such a kill by itself.
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00:09:25,000 --> 00:09:26,880
The only way they have
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00:09:26,880 --> 00:09:30,880
of surviving the winter
is as a super-pack.
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00:09:46,560 --> 00:09:50,480
These snow-covered forests
encircle the Arctic
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from Scandinavia, through Russia,
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00:09:53,360 --> 00:09:57,160
to Alaska and the rest
of North America.
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00:10:00,120 --> 00:10:02,240
But close to the North Pole,
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00:10:02,240 --> 00:10:04,880
the winters are too long
and too cold
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00:10:04,880 --> 00:10:07,520
for even the hardiest of trees.
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00:10:09,520 --> 00:10:13,200
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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00:10:25,240 --> 00:10:29,600
Here, conditions are even more
extreme than in the forests.
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00:10:34,120 --> 00:10:37,080
During the two months
of winter darkness,
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temperatures may fall
to minus 50 degrees Celsius.
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00:10:44,640 --> 00:10:46,840
The ground deep beneath the snow
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has been frozen solid
since the last Ice Age.
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00:10:56,800 --> 00:10:59,520
There is no shelter of any kind.
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00:10:59,520 --> 00:11:02,280
Very few animals can survive here.
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00:11:07,040 --> 00:11:09,200
But this is one which does.
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00:11:12,080 --> 00:11:14,040
An arctic fox.
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00:11:16,960 --> 00:11:19,720
It has the warmest fur
of any mammal.
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00:11:20,680 --> 00:11:21,920
And it can survive
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00:11:21,920 --> 00:11:24,680
blizzards that may rage
for days on end.
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00:11:29,120 --> 00:11:33,280
It must nonetheless
eventually eat something.
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00:11:34,600 --> 00:11:36,760
But how is that something
to be found
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when you're all by yourself
in this desolation?
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00:11:54,200 --> 00:11:57,080
Arctic foxes are wanderers.
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00:11:59,160 --> 00:12:04,240
And they can travel over 2,000
miles, from Norway to Canada,
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00:12:04,240 --> 00:12:07,080
in a constant search for food.
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00:12:23,960 --> 00:12:26,840
There might be something here.
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00:12:28,080 --> 00:12:31,360
A patch of grass,
kept clear of the snow
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by the near-constant wind.
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The slightest hint of scent
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00:12:36,440 --> 00:12:39,120
might indicate the presence of prey.
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00:12:46,320 --> 00:12:48,840
Less than a metre below the surface
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00:12:48,840 --> 00:12:52,120
may lie a hidden network of tunnels,
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00:12:52,120 --> 00:12:55,920
shown here using
a special filming burrow.
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00:13:13,360 --> 00:13:15,760
Tiny arctic lemmings.
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00:13:18,520 --> 00:13:22,000
With a carpet of edible moss beneath
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00:13:22,000 --> 00:13:24,600
and a thick blanket of snow above...
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00:13:24,600 --> 00:13:27,920
...the lemmings spend
their entire winter
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00:13:27,920 --> 00:13:29,480
hidden below the surface.
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00:13:31,000 --> 00:13:33,480
And here they breed.
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00:13:41,880 --> 00:13:44,120
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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00:13:55,760 --> 00:14:00,360
Lemming burrows may
extend for up to 15 metres.
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00:14:08,160 --> 00:14:11,320
Pinpointing the position
of one of the inhabitants...
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00:14:12,560 --> 00:14:14,560
...is not easy.
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00:14:17,760 --> 00:14:21,000
An acute sense
of hearing is essential.
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00:14:25,200 --> 00:14:26,880
And the arctic fox
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has a special trick.
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It doesn't always work first time.
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00:14:50,760 --> 00:14:53,640
And it does require dedication.
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00:15:14,480 --> 00:15:18,560
With less than 25 lemmings
per square mile of tundra...
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...you have to persevere.
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00:15:31,560 --> 00:15:34,200
And at last,
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one plump lemming.
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00:15:39,360 --> 00:15:43,320
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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00:16:04,440 --> 00:16:07,520
On the tundra's southern fringes,
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winter is significantly less severe.
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00:16:15,000 --> 00:16:18,360
The slight increase
in annual sunlight
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00:16:18,360 --> 00:16:22,200
has enabled a stunted forest
to develop.
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00:16:39,960 --> 00:16:44,240
It's the northern edge of the
world's largest woodland...
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00:16:45,200 --> 00:16:47,760
...the boreal forest.
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00:16:54,400 --> 00:16:58,280
750 billion trees.
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00:17:00,480 --> 00:17:03,440
A quarter of all the trees on Earth.
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00:17:06,400 --> 00:17:09,000
And it encircles the globe.
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00:17:11,280 --> 00:17:14,680
These forests store
twice as much carbon
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00:17:14,680 --> 00:17:19,080
as a tropical forest,
and they play a crucial part
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00:17:19,080 --> 00:17:22,720
in regulating the climate
of the entire planet.
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00:17:28,800 --> 00:17:31,040
One of the most remote tracts
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00:17:31,040 --> 00:17:34,200
stands in the far east of Siberia.
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00:17:39,520 --> 00:17:43,520
It's cut off from the rest of
the world by towering peaks...
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00:17:44,640 --> 00:17:47,480
...and precipitous valleys.
150
00:17:51,360 --> 00:17:54,320
And it is the last stronghold
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of the world's rarest big cat.
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The Amur leopard.
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00:18:18,360 --> 00:18:21,760
Hunting has brought it
close to extinction.
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00:18:21,760 --> 00:18:25,640
Only 120 are left in the wild.
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00:18:28,800 --> 00:18:33,720
And this is one of the very
few ever to be caught on film.
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00:18:46,280 --> 00:18:51,040
Each must patrol a territory
of over 100 square miles
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to find enough to eat.
158
00:18:58,760 --> 00:19:00,840
In the cold of March,
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00:19:00,840 --> 00:19:04,120
prey is at its most scarce.
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00:19:16,320 --> 00:19:19,400
But leopards are clever opportunists
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00:19:19,400 --> 00:19:22,040
and watch for clues.
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Crows.
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00:19:28,040 --> 00:19:30,480
They too are looking for food.
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00:19:33,320 --> 00:19:37,480
And their calls tell him
that they've found something.
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00:19:53,640 --> 00:19:57,720
But he is not
the only predator here.
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00:19:59,000 --> 00:20:03,040
On one of the trees,
the marks of huge claws,
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ten centimetres long.
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00:20:08,840 --> 00:20:12,640
They've been made
by a hunter twice his size...
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...a Siberian tiger.
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00:20:25,320 --> 00:20:28,840
Fewer than 500 remain in the wild.
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00:20:35,120 --> 00:20:40,480
These two rare big cats
are sharing the same territory.
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And fixed remote cameras
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00:20:47,560 --> 00:20:51,360
show that they even use
exactly the same trails.
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00:20:56,560 --> 00:21:00,040
But leopards know
they must be careful.
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00:21:05,400 --> 00:21:09,760
Siberian tigers are the
biggest of all the big cats,
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00:21:09,760 --> 00:21:12,320
and could kill a leopard...
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00:21:15,080 --> 00:21:17,160
...should they ever meet.
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00:21:28,440 --> 00:21:29,560
In winter,
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00:21:29,560 --> 00:21:33,840
many forest animals
rely on carrion for food.
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00:21:38,560 --> 00:21:40,800
And that includes leopards.
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00:21:51,000 --> 00:21:54,120
But he can't let down his guard.
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00:22:05,840 --> 00:22:07,760
The crows that led him here...
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00:22:07,760 --> 00:22:10,880
...may also have alerted the tiger.
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00:22:41,800 --> 00:22:43,280
The crows are disturbed.
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00:22:44,960 --> 00:22:47,880
Another mouthful might be risky.
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00:23:03,520 --> 00:23:07,200
Survival sometimes
depends on knowing
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00:23:07,200 --> 00:23:08,720
when to leave.
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00:23:16,720 --> 00:23:19,960
Only a few choose
to take their chances here
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00:23:19,960 --> 00:23:22,440
in the depths of winter.
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00:23:23,800 --> 00:23:29,200
Elsewhere, vast swathes of
the forest remain eerily empty.
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00:23:33,480 --> 00:23:37,840
Above, there is
an otherworldly light show...
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00:23:42,720 --> 00:23:45,160
...the aurora borealis.
193
00:23:51,760 --> 00:23:53,560
High in the sky,
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00:23:53,560 --> 00:23:57,200
electrically charged
solar particles from space
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00:23:57,200 --> 00:23:59,840
collide with the Earth's atmosphere
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00:23:59,840 --> 00:24:02,760
and create this ethereal display.
197
00:24:15,000 --> 00:24:20,920
Meanwhile, in Canada, through
the six long months of winter,
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00:24:20,920 --> 00:24:25,800
life below ground
is biding its time.
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00:24:31,520 --> 00:24:35,120
The world's most northerly turtle...
200
00:24:36,880 --> 00:24:38,320
...the painted turtle...
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00:24:38,320 --> 00:24:42,080
...seen here
in a special filming chamber.
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00:24:43,400 --> 00:24:46,280
They hatched last autumn
but have remained
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00:24:46,280 --> 00:24:49,800
in a state of suspended
animation ever since.
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00:24:52,720 --> 00:24:55,360
Their hearts have stopped beating...
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00:24:56,720 --> 00:24:59,240
...and only their brains
have remained active,
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00:24:59,240 --> 00:25:01,680
and even then, only very faintly.
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00:25:05,200 --> 00:25:08,640
Painted turtles wait underground
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00:25:08,640 --> 00:25:11,120
for this most important
of moments...
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00:25:20,960 --> 00:25:24,280
...the arrival of spring.
210
00:25:38,880 --> 00:25:42,280
In April, the strengthening sunshine
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00:25:42,280 --> 00:25:46,280
triggers a miraculous
transformation.
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00:26:00,680 --> 00:26:04,920
The turtles' body temperature
rises just above freezing...
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00:26:10,600 --> 00:26:14,360
...and their hearts
start to beat once more.
214
00:26:29,560 --> 00:26:32,360
Slowly, they return to life.
215
00:26:34,320 --> 00:26:39,480
Thanks to this extraordinary
adaptation, these young turtles
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00:26:39,480 --> 00:26:43,240
get a valuable head start
in spring...
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00:26:53,240 --> 00:26:56,880
...and are one of the first
to emerge, ready to take
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00:26:56,880 --> 00:27:00,560
full advantage of the forest's
renewed abundance.
219
00:27:08,520 --> 00:27:12,320
In just a matter of weeks,
the vast northern forests
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00:27:12,320 --> 00:27:14,400
flush green.
221
00:27:29,760 --> 00:27:35,640
For Siberia's big cats, each
spring could bring new hope.
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00:27:39,000 --> 00:27:40,480
Cubs.
223
00:27:42,680 --> 00:27:45,560
Each of them
increases the chance that,
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00:27:45,560 --> 00:27:50,480
even at this very late stage,
both species might recover.
225
00:28:02,920 --> 00:28:07,080
By June, the northern forests
are full of life.
226
00:28:16,120 --> 00:28:20,800
But several thousands of miles
further north, in the tundra,
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00:28:20,800 --> 00:28:23,760
the spring thaw
is only just beginning.
228
00:28:30,920 --> 00:28:34,080
When it does,
under 24-hour daylight,
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00:28:34,080 --> 00:28:37,280
its impact is even more extreme.
230
00:28:42,920 --> 00:28:45,680
Five million square miles of snow
231
00:28:45,680 --> 00:28:48,600
disappear in a matter of days.
232
00:28:59,200 --> 00:29:02,520
Ten centimetres beneath
the surface of the ground,
233
00:29:02,520 --> 00:29:06,960
a snow queen is waiting
to make her appearance.
234
00:29:12,280 --> 00:29:15,480
A Lapland bumblebee.
235
00:29:16,680 --> 00:29:19,000
She's barely alive.
236
00:29:21,040 --> 00:29:25,520
All the other members of her colony
were killed by the cold.
237
00:29:27,880 --> 00:29:31,880
She survived,
as bumblebee queens do,
238
00:29:31,880 --> 00:29:36,840
thanks to her larger size,
her particularly thick fur,
239
00:29:36,840 --> 00:29:41,360
and a natural antifreeze
that she has in her body.
240
00:29:52,720 --> 00:29:55,440
As temperatures continue to rise,
241
00:29:55,440 --> 00:29:58,240
she begins to thaw.
242
00:30:09,520 --> 00:30:12,160
She vibrates her flight muscles,
243
00:30:12,160 --> 00:30:14,440
which raises her body temperature
244
00:30:14,440 --> 00:30:19,040
to over 30 degrees Celsius
in just six minutes.
245
00:30:21,520 --> 00:30:24,840
There is no time to lose.
246
00:30:28,120 --> 00:30:32,040
She must now create
an entire colony.
247
00:30:40,400 --> 00:30:43,400
First, the queen must find
a drink of nectar
248
00:30:43,400 --> 00:30:45,400
to regain her strength...
249
00:30:49,120 --> 00:30:51,480
...travelling as much as
three miles a day
250
00:30:51,480 --> 00:30:54,560
to find the flowers
from which to collect it.
251
00:31:03,960 --> 00:31:05,840
She works tirelessly.
252
00:31:08,560 --> 00:31:10,800
As well as high-energy nectar...
253
00:31:12,760 --> 00:31:15,080
...there's pollen to be gathered.
254
00:31:28,600 --> 00:31:34,240
Back underground, she uses the
pollen to build a waxy cocoon.
255
00:31:36,080 --> 00:31:39,840
And in it,
she deposits the tiny eggs.
256
00:31:43,440 --> 00:31:46,400
Had she laid them
directly on the frozen ground,
257
00:31:46,400 --> 00:31:48,520
the cold would have killed them.
258
00:31:48,520 --> 00:31:51,080
And now she warms them
259
00:31:51,080 --> 00:31:53,080
by pulsating her body.
260
00:32:02,640 --> 00:32:05,160
She has also constructed
a little pot
261
00:32:05,160 --> 00:32:07,240
in which she stores nectar
262
00:32:07,240 --> 00:32:10,440
to provide her with a drink
when she needs it.
263
00:32:16,280 --> 00:32:18,440
For the next three weeks...
264
00:32:19,400 --> 00:32:21,000
...this single mother
265
00:32:21,000 --> 00:32:24,200
works around the clock,
gathering nectar
266
00:32:24,200 --> 00:32:25,960
to top up her pot...
267
00:32:34,600 --> 00:32:36,400
...and vibrating her body
268
00:32:36,400 --> 00:32:39,880
to prevent her developing young
from freezing to death.
269
00:32:51,600 --> 00:32:55,720
Eventually, a new generation of bees
270
00:32:55,720 --> 00:32:58,280
starts to emerge.
271
00:33:04,920 --> 00:33:09,040
She leads each young
worker to her honey pot
272
00:33:09,040 --> 00:33:11,720
and encourages it to drink.
273
00:33:18,400 --> 00:33:21,880
By the end of the following week,
274
00:33:21,880 --> 00:33:25,480
the number in her little colony
has increased to eight.
275
00:33:27,880 --> 00:33:30,880
Her timing has been perfect.
276
00:33:36,960 --> 00:33:40,040
The tundra is now in full bloom.
277
00:33:47,680 --> 00:33:51,000
And the bumblebee families
help to pollinate
278
00:33:51,000 --> 00:33:54,600
the largest wild-flower
meadow on Earth.
279
00:34:09,400 --> 00:34:14,160
But the summer here is one
of the shortest on the planet.
280
00:34:14,160 --> 00:34:17,000
And all of the tundra's residents
281
00:34:17,000 --> 00:34:19,520
are now racing to breed.
282
00:34:22,920 --> 00:34:27,600
Alaskan snowy owls have
a brood of six fluffy chicks
283
00:34:27,600 --> 00:34:30,960
and only eight weeks
in which to raise them.
284
00:34:39,600 --> 00:34:44,000
The parents provide them
with 30 lemmings a day...
285
00:34:45,400 --> 00:34:48,000
...for the chicks will need
to triple their weight
286
00:34:48,000 --> 00:34:50,120
before they reach independence.
287
00:34:59,960 --> 00:35:04,560
Unusually for an owl,
snowies hunt by day.
288
00:35:09,040 --> 00:35:11,160
And over the next two weeks,
289
00:35:11,160 --> 00:35:14,840
they take full advantage of
the Arctic's continuous light.
290
00:35:21,160 --> 00:35:27,320
But this morning, the female
returns to an empty nest.
291
00:35:33,360 --> 00:35:36,000
Her chicks are nowhere to be seen.
292
00:35:45,960 --> 00:35:47,960
They're hiding.
293
00:35:53,160 --> 00:35:57,440
They're so big, the whole group
might be spotted by predators,
294
00:35:57,440 --> 00:36:01,320
so they have scattered
across the tundra.
295
00:36:07,520 --> 00:36:11,960
But that makes feeding them
all much harder work.
296
00:36:23,560 --> 00:36:25,680
Over 600 meals later,
297
00:36:25,680 --> 00:36:28,320
the parents' lab ours
are starting to pay off...
298
00:36:30,400 --> 00:36:34,520
...as the chicks stretch
their newly developed wings.
299
00:36:44,120 --> 00:36:48,440
Just a month is left
before winter returns.
300
00:37:06,000 --> 00:37:07,480
Two weeks more,
301
00:37:07,480 --> 00:37:10,160
and their transformation
is almost complete.
302
00:37:12,280 --> 00:37:14,760
The chicks' wings
might at last be able
303
00:37:14,760 --> 00:37:17,960
to do more than just
lift them from the ground.
304
00:37:23,840 --> 00:37:25,520
Getting there!
305
00:37:31,920 --> 00:37:33,880
Keep going!
306
00:37:37,840 --> 00:37:39,360
Airborne!
307
00:37:39,360 --> 00:37:43,040
The youngsters are ready
for independence.
308
00:37:45,480 --> 00:37:49,360
And the exhausted parents
can take a well-earned rest.
309
00:37:55,400 --> 00:37:58,440
The tundra has come to life
once again.
310
00:38:00,600 --> 00:38:04,040
But in the longer term,
its very foundations
311
00:38:04,040 --> 00:38:06,360
are now at risk.
312
00:38:20,400 --> 00:38:23,600
The ground itself is giving way.
313
00:38:36,520 --> 00:38:42,360
In some places, it's dropped
by more than 60 metres.
314
00:38:46,400 --> 00:38:50,440
Grasslands that once supported
thousands of different species
315
00:38:50,440 --> 00:38:53,360
have become wastelands.
316
00:39:00,520 --> 00:39:03,120
Arctic temperatures are rising
317
00:39:03,120 --> 00:39:06,280
as a consequence of climate change.
318
00:39:10,840 --> 00:39:13,800
The deep soil
which has been frozen solid
319
00:39:13,800 --> 00:39:17,240
for thousands of years,
the permafrost,
320
00:39:17,240 --> 00:39:21,360
is now thawing at a rate
never witnessed before.
321
00:39:27,440 --> 00:39:29,400
Without the ice to bind it together,
322
00:39:29,400 --> 00:39:32,080
the ground becomes unstable.
323
00:39:38,800 --> 00:39:42,480
In Canada, thousands of
tonnes of the tundra
324
00:39:42,480 --> 00:39:45,040
have collapsed in a matter of weeks.
325
00:39:58,760 --> 00:40:03,040
And in Siberia,
huge scars are appearing.
326
00:40:09,240 --> 00:40:13,280
By the end of the century,
an area of Arctic permafrost
327
00:40:13,280 --> 00:40:15,840
one third of the size of Europe
328
00:40:15,840 --> 00:40:17,920
could have thawed.
329
00:40:23,440 --> 00:40:24,920
The warming of the tundra
330
00:40:24,920 --> 00:40:28,440
is having a profound impact
on its wildlife.
331
00:40:30,960 --> 00:40:36,280
For millennia, caribou
have made annual migrations.
332
00:40:41,200 --> 00:40:42,520
Every summer,
333
00:40:42,520 --> 00:40:45,880
driven by the seasonal
changes of the far north
334
00:40:45,880 --> 00:40:49,560
and following
long-established pathways,
335
00:40:49,560 --> 00:40:53,880
they have trekked
almost 400 miles north.
336
00:41:10,920 --> 00:41:17,160
This herd alone in north-east
Alaska numbers over 200,000.
337
00:41:25,920 --> 00:41:27,320
Their destination
338
00:41:27,320 --> 00:41:29,280
is a vast wilderness
339
00:41:29,280 --> 00:41:33,160
known as the Arctic
National Wildlife Refuge.
340
00:41:44,680 --> 00:41:48,400
These summer pastures
provide rich grazing,
341
00:41:48,400 --> 00:41:52,520
just what's needed
to raise newborn calves.
342
00:42:01,760 --> 00:42:04,800
This one, fattening up
on its mother's milk,
343
00:42:04,800 --> 00:42:08,120
would normally double its weight
in just a few weeks.
344
00:42:18,600 --> 00:42:22,440
But now grazing time
is being disrupted.
345
00:42:28,920 --> 00:42:31,920
In summer, the tundra
becomes waterlogged.
346
00:42:35,120 --> 00:42:38,400
These are excellent
breeding conditions
347
00:42:38,400 --> 00:42:41,680
for mosquitoes
and other biting insects.
348
00:42:50,080 --> 00:42:52,200
But as the climate warms,
349
00:42:52,200 --> 00:42:55,920
there are concerns
that insects will breed earlier
350
00:42:55,920 --> 00:42:58,800
and eventually reach
plague proportions
351
00:42:58,800 --> 00:43:01,280
just as the caribou need to feed.
352
00:43:05,480 --> 00:43:07,440
Individual animals could lose
353
00:43:07,440 --> 00:43:12,200
a quarter of a pint of blood
a day to biting insects.
354
00:43:17,960 --> 00:43:21,080
So the caribou may
end their grazing early
355
00:43:21,080 --> 00:43:25,240
and head for cooler,
mosquito-free pastures.
356
00:43:33,320 --> 00:43:35,080
But to get to such places,
357
00:43:35,080 --> 00:43:39,160
they will have to cross rivers
swollen by seasonal runoff.
358
00:43:54,040 --> 00:43:58,640
For a young calf, a deep river
crossing is very dangerous.
359
00:44:04,800 --> 00:44:08,520
He does what he can
to stay close to his mother.
360
00:44:18,280 --> 00:44:20,640
But he doesn't have the strength
361
00:44:20,640 --> 00:44:23,320
to resist the fast-moving current.
362
00:45:15,960 --> 00:45:19,240
He is one of the lucky ones.
363
00:45:23,400 --> 00:45:26,000
Reunited with his mother,
364
00:45:26,000 --> 00:45:29,680
he can continue
on his journey with the herd.
365
00:45:38,800 --> 00:45:42,240
But other calves
are less fortunate...
366
00:45:44,880 --> 00:45:48,840
...and must now
fend for themselves.
367
00:46:00,200 --> 00:46:04,360
Some are too exhausted
to take another step.
368
00:46:12,400 --> 00:46:15,840
But this is not a safe place
to take a rest.
369
00:46:41,200 --> 00:46:42,960
Grizzly bears.
370
00:46:47,080 --> 00:46:48,600
For the past few weeks,
371
00:46:48,600 --> 00:46:51,640
there has been little food
for them on the tundra.
372
00:46:54,360 --> 00:46:57,240
And this one is extremely hungry.
373
00:47:13,600 --> 00:47:17,040
He's looking for the weak and weary.
374
00:47:26,720 --> 00:47:29,640
And he's found one...
375
00:47:41,640 --> 00:47:43,880
...too tired to flee...
376
00:47:47,040 --> 00:47:49,400
...and too weak to resist.
377
00:48:01,040 --> 00:48:02,760
The herd's finally reached
378
00:48:02,760 --> 00:48:05,200
the northern limits of its range.
379
00:48:10,240 --> 00:48:13,680
These coastal pastures
bordering the Arctic Ocean
380
00:48:13,680 --> 00:48:16,560
remain cool enough to provide relief
381
00:48:16,560 --> 00:48:18,680
from the swarms of insects.
382
00:48:23,560 --> 00:48:27,320
Mothers and calves
can finally feed in peace.
383
00:48:34,440 --> 00:48:38,920
For now, this
immense herd is stable.
384
00:48:41,080 --> 00:48:45,800
But in the long term,
its survival is now uncertain.
385
00:48:51,520 --> 00:48:54,520
The seasonal extremes
of the far north
386
00:48:54,520 --> 00:48:58,160
have always tested
its inhabitants to the limits.
387
00:49:00,360 --> 00:49:03,160
But climate change
could present them
388
00:49:03,160 --> 00:49:05,320
with one challenge too many.
389
00:49:07,240 --> 00:49:10,320
Only if we can mitigate its effects
390
00:49:10,320 --> 00:49:13,040
will the remarkable wildlife here
391
00:49:13,040 --> 00:49:16,080
stand a chance of survival.
392
00:49:34,920 --> 00:49:37,880
Filming in the extremes
of the far north...
393
00:49:38,920 --> 00:49:41,920
...the team's greatest
challenge was to capture
394
00:49:41,920 --> 00:49:44,880
the epic showdown between
super-packs of wolves
395
00:49:44,880 --> 00:49:47,480
and bison in midwinter.
396
00:49:50,800 --> 00:49:52,080
The crew travelled to
397
00:49:52,080 --> 00:49:55,040
Wood Buffalo National Park
in northern Canada,
398
00:49:55,040 --> 00:49:58,880
a remote wilderness
the size of Switzerland.
399
00:50:02,120 --> 00:50:04,560
To stand a chance
of filming this drama,
400
00:50:04,560 --> 00:50:06,680
they must take to the skies.
401
00:50:08,120 --> 00:50:09,480
Drawing on local knowledge,
402
00:50:09,480 --> 00:50:13,080
pilot Matt Erhardt
helps to pinpoint
403
00:50:13,080 --> 00:50:15,280
one of the last
free-roaming herds of bison
404
00:50:15,280 --> 00:50:17,960
and the wolves that
specialise in hunting them.
405
00:50:21,600 --> 00:50:23,720
Some of the wolves
have run forwards.
406
00:50:23,720 --> 00:50:25,640
Just have all your kit
ready to go.
407
00:50:27,920 --> 00:50:29,320
With a positive sighting,
408
00:50:29,320 --> 00:50:31,400
it's time to mobilise the film crew.
409
00:50:33,760 --> 00:50:36,840
Cameraman Jamie McPherson
has rigged the helicopter
410
00:50:36,840 --> 00:50:39,600
with a gyrostabilised camera system,
411
00:50:39,600 --> 00:50:42,960
enabling him to capture
rock-steady images
412
00:50:42,960 --> 00:50:44,480
from a safe distance.
413
00:50:44,480 --> 00:50:46,400
You'd think filming
from a helicopter's easy,
414
00:50:46,400 --> 00:50:48,360
because you can just
fly around and film stuff.
415
00:50:48,360 --> 00:50:50,040
But you've got to be
incredibly careful,
416
00:50:50,040 --> 00:50:51,360
not influence the behaviour,
417
00:50:51,360 --> 00:50:52,880
not scare the wolves or the bison.
418
00:50:57,320 --> 00:50:59,680
There we go.
Yeah, that is them.
419
00:51:00,680 --> 00:51:02,080
It's a big pack. Yeah.
420
00:51:03,920 --> 00:51:05,960
They're really chilled out
with the helicopter.
421
00:51:05,960 --> 00:51:07,240
Really encouraging.
422
00:51:09,480 --> 00:51:11,720
But before Jamie can start filming,
423
00:51:11,720 --> 00:51:15,000
the chopper must first drop
the accompanying ground crew.
424
00:51:15,000 --> 00:51:17,200
Good luck. OK.
425
00:51:22,800 --> 00:51:24,200
We got put down
426
00:51:24,200 --> 00:51:25,720
in this vast open space,
427
00:51:25,720 --> 00:51:28,800
and now we're going to
try and hike in and see
428
00:51:28,800 --> 00:51:30,120
if we can get close to them,
429
00:51:30,120 --> 00:51:32,000
or hopefully they'll
get close to us.
430
00:51:33,120 --> 00:51:37,480
To intercept the pack, the team
must scramble into position.
431
00:51:41,400 --> 00:51:43,920
But trudging through
knee-deep snow
432
00:51:43,920 --> 00:51:45,800
is hard going.
433
00:51:50,280 --> 00:51:52,760
Every time I catch up with
Justin, he just keeps on going.
434
00:51:52,760 --> 00:51:54,200
He's a machine!
435
00:52:01,000 --> 00:52:02,120
Yeah, go ahead, Matt.
436
00:52:02,120 --> 00:52:03,880
They're starting to head
437
00:52:03,880 --> 00:52:05,640
a little bit towards
the north-west,
438
00:52:05,640 --> 00:52:07,800
so they're starting to
move away from you.
439
00:52:09,080 --> 00:52:10,520
Oh, Goddamn it!
440
00:52:11,880 --> 00:52:14,280
The ground crew
will have to dig deep
441
00:52:14,280 --> 00:52:17,120
if they're to film
the fleet-footed wolves.
442
00:52:22,000 --> 00:52:23,400
Over the following week,
443
00:52:23,400 --> 00:52:26,040
Jamie manages to track
the wolf pack
444
00:52:26,040 --> 00:52:28,200
from the comfort
of the helicopter...
445
00:52:29,200 --> 00:52:31,200
...while down on the ground,
446
00:52:31,200 --> 00:52:34,800
Justin and Will are having
a tougher time of it.
447
00:52:34,800 --> 00:52:39,680
Ohhh! It's really
incredibly awkward getting around.
448
00:52:39,680 --> 00:52:42,520
Even lunch offers
little consolation.
449
00:52:42,520 --> 00:52:43,760
It's frozen bread,
450
00:52:43,760 --> 00:52:46,720
frozen Brie and frozen pickle.
451
00:52:47,720 --> 00:52:49,040
And with no wolf activity
452
00:52:49,040 --> 00:52:50,200
visible from the air,
453
00:52:50,200 --> 00:52:52,760
Jamie is soon grounded.
454
00:52:52,760 --> 00:52:54,840
Yeah, I'm just
looking for an update.
455
00:53:00,320 --> 00:53:02,520
Great...
456
00:53:05,160 --> 00:53:07,560
The winter weather
takes a turn for the worse.
457
00:53:07,560 --> 00:53:10,200
It's snowing, and it's at
a temperature where it could
458
00:53:10,200 --> 00:53:12,000
potentially stick to the blades
459
00:53:12,000 --> 00:53:14,080
and become really dangerous.
460
00:53:14,080 --> 00:53:18,400
For the next few days, the crew
are forced to sit it out.
461
00:53:24,040 --> 00:53:26,320
Finally, the skies clear.
462
00:53:27,280 --> 00:53:30,080
But after nearly three weeks
on location,
463
00:53:30,080 --> 00:53:32,400
there's precious little
filming time left.
464
00:53:33,520 --> 00:53:35,920
We've got one last shot
465
00:53:35,920 --> 00:53:38,040
to get what we're looking for.
466
00:53:38,040 --> 00:53:41,320
And just hoping that it comes
together at the last minute.
467
00:53:48,440 --> 00:53:50,000
There, there's the trail there,
468
00:53:50,000 --> 00:53:52,000
so they're on the west side
of that trail there.
469
00:53:55,520 --> 00:53:57,840
Soon enough, they find the bison,
470
00:53:57,840 --> 00:53:59,800
along with wolves
471
00:53:59,800 --> 00:54:01,560
who appear to be in hunting mode.
472
00:54:02,760 --> 00:54:05,600
The spotter plane just found
the wolves with the bison,
473
00:54:05,600 --> 00:54:07,960
so we're scrambling to get
there as quick as we can.
474
00:54:29,920 --> 00:54:31,920
There's something about
475
00:54:31,920 --> 00:54:35,480
being in the presence of prey
and predator on the ground
476
00:54:35,480 --> 00:54:37,840
like this which is very special.
477
00:54:39,000 --> 00:54:43,320
Justin is in prime position
to capture the showdown.
478
00:54:50,960 --> 00:54:52,200
As a chase begins,
479
00:54:52,200 --> 00:54:55,760
Jamie picks up the action
from the air.
480
00:55:02,760 --> 00:55:05,440
It'd be amazing
if we could get round that. OK.
481
00:55:09,840 --> 00:55:11,640
In a stop-start pursuit
482
00:55:11,640 --> 00:55:13,040
lasting an entire day,
483
00:55:13,040 --> 00:55:17,280
Jamie manages to record
the full jaw-dropping drama.
484
00:55:20,000 --> 00:55:21,640
They've definitely got
that female.
485
00:55:21,640 --> 00:55:23,640
I think they're going to
bring it down.
486
00:55:27,880 --> 00:55:31,000
Perfect, Jim. We got it.
487
00:55:32,000 --> 00:55:33,960
With the hunt nearly over,
488
00:55:33,960 --> 00:55:36,880
the crew reposition Justin
once more.
489
00:55:46,480 --> 00:55:50,440
We got on the ground
just in time to capture
490
00:55:50,440 --> 00:55:52,440
from a really far distance
491
00:55:52,440 --> 00:55:55,640
the last moments
of the bison's life.
492
00:55:58,560 --> 00:56:00,800
There's a moment of confliction
493
00:56:00,800 --> 00:56:04,240
between your loyalty
for each animal.
494
00:56:04,240 --> 00:56:09,600
One is filled with a mixture of
both celebration for the wolves
495
00:56:09,600 --> 00:56:14,040
but a sadness. Both exist
somehow simultaneously.
496
00:56:19,320 --> 00:56:22,440
Bearing witness to this
rarely seen age-old battle
497
00:56:22,440 --> 00:56:26,160
between predator and prey
leaves the crew
498
00:56:26,160 --> 00:56:29,360
with an appreciation of
just how challenging life is
499
00:56:29,360 --> 00:56:32,440
in the frozen extremes
of the far north.
500
00:56:42,040 --> 00:56:43,280
Next time...
501
00:56:44,680 --> 00:56:47,240
...we meet the scientists
and people...
502
00:56:48,840 --> 00:56:51,080
...who are dedicating their lives
503
00:56:51,080 --> 00:56:53,680
to understanding
the changes taking place...
504
00:56:56,000 --> 00:56:58,440
...across our frozen planet.
505
00:56:59,880 --> 00:57:03,400
Changes that'll impact
the lives of each...
506
00:57:04,520 --> 00:57:05,840
...and every one of us.
507
00:57:08,600 --> 00:57:10,680
The Open University has
produced a poster
508
00:57:10,680 --> 00:57:15,131
exploring how animals adapt to life
in the world's coldest environments.
509
00:57:15,156 --> 00:57:21,053
To order your free copy,
please call 0300 303 0553,
510
00:57:21,078 --> 00:57:26,193
or go to bbc.co.uk/frozenplanet2
511
00:57:26,218 --> 00:57:28,360
...and follow the links
to The Open University.
38768
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