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David Attenborough:
In the far north of our planet
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00:00:41,760 --> 00:00:44,480
lie vast frozen lands...
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00:00:46,960 --> 00:00:49,120
Of snow-covered forests...
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00:00:50,360 --> 00:00:52,400
And open tundra.
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00:00:55,400 --> 00:00:57,000
During the months to come,
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00:00:57,120 --> 00:00:58,920
they will be transformed
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00:00:59,040 --> 00:01:02,840
by the greatest
seasonal changes on earth.
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00:01:05,880 --> 00:01:07,840
But now, in midwinter,
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00:01:07,960 --> 00:01:12,800
conditions are so hostile that
life seems all but impossible.
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00:01:19,040 --> 00:01:20,360
But...
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Not so.
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00:01:25,560 --> 00:01:28,800
In this world of extremes,
animals must go
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00:01:28,920 --> 00:01:31,720
to extraordinary lengths
to survive.
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00:02:01,160 --> 00:02:03,800
February, northern Canada.
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00:02:06,600 --> 00:02:07,640
The harsh winter
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00:02:07,760 --> 00:02:11,400
has brought together
an extended family of wolves.
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00:02:13,600 --> 00:02:16,600
But this is no ordinary pack.
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There are 25 of them.
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A super-pack,
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one of the largest
ever recorded.
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00:02:35,000 --> 00:02:37,280
They're ravenously hungry.
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They may have walked
over 150 miles
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00:02:41,840 --> 00:02:44,240
since they last had a meal.
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00:02:45,760 --> 00:02:49,680
But now, at last,
the lead male and female
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have picked up a trail.
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00:02:55,160 --> 00:02:59,200
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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00:03:05,440 --> 00:03:07,440
Bison.
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00:03:11,040 --> 00:03:12,920
They're formidable animals,
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00:03:13,040 --> 00:03:15,200
not easy to attack.
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00:03:17,800 --> 00:03:21,680
The bulls are ten times
the size of a wolf.
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00:03:23,720 --> 00:03:25,200
And they have horns
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00:03:25,320 --> 00:03:29,040
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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00:03:50,360 --> 00:03:52,200
Is to try and break up the group
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and isolate one of them.
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00:04:03,760 --> 00:04:04,960
To do that,
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00:04:05,080 --> 00:04:08,480
they will have to work as a team
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00:04:08,600 --> 00:04:11,600
and try to start a stampede.
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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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00:04:45,120 --> 00:04:49,160
A kick from a bison's hind leg
could shatter her jaws.
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00:04:59,040 --> 00:05:03,440
But the pack must feed,
and they take turns to attack.
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00:05:08,640 --> 00:05:11,280
The bison head for cover.
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The deep snow slows down
both attacked...
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And attacker.
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00:05:36,600 --> 00:05:38,920
The herd splits into two.
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00:05:43,200 --> 00:05:46,120
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 straightfonnard chase...
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00:06:00,840 --> 00:06:02,960
Into a deadly form...
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00:06:03,080 --> 00:06:04,880
Of hide...
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00:06:06,520 --> 00:06:08,280
And seek.
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Discovered.
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00:06:32,720 --> 00:06:36,000
The lead female manages
to chase the smaller group
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00:06:36,120 --> 00:06:37,680
into the open.
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00:06:56,640 --> 00:07:00,880
But here the bison are able to
close ranks once again.
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00:07:07,600 --> 00:07:09,520
The leading wolves wait
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00:07:09,640 --> 00:07:11,920
for the rest of the pack
to catch up.
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00:07:27,520 --> 00:07:31,720
The super-pack is once again
at full strength.
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00:07:36,160 --> 00:07:39,080
Suddenly,
two of the bison panic.
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00:07:40,280 --> 00:07:43,280
It's just what the wolves
have been waiting for.
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00:07:58,200 --> 00:08:00,880
One of the bison is tiring.
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00:08:04,360 --> 00:08:07,080
The lead female
gets a grip on its flanks.
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The male joins her.
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00:08:22,880 --> 00:08:26,120
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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00:08:52,640 --> 00:08:58,120
After eight long, hard hours,
the hunt is coming to an end.
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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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00:09:26,000 --> 00:09:29,040
The only way they have
of surviving the winter
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00:09:29,160 --> 00:09:31,840
is as a super-pack.
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These snow-covered forests
encircle the arctic
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00:09:51,480 --> 00:09:54,240
from scandinavia,
through Russia,
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00:09:54,360 --> 00:09:58,120
to Alaska and the rest
of North America.
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00:10:01,120 --> 00:10:03,120
But close to the north pole,
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00:10:03,240 --> 00:10:05,760
the winters are too long
and too cold
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00:10:05,880 --> 00:10:08,480
for even the hardiest of trees.
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00:10:10,520 --> 00:10:14,080
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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00:10:26,240 --> 00:10:30,560
Here, conditions are even more
extreme than in the forests.
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00:10:35,120 --> 00:10:37,960
During the two months
of winter darkness,
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00:10:38,080 --> 00:10:42,560
temperatures may fall
to minus 50 degrees celsius.
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The ground deep beneath the snow
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00:10:47,840 --> 00:10:52,000
has been frozen solid
since the last ice age.
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00:10:57,800 --> 00:11:00,400
There is no shelter of any kind.
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00:11:00,520 --> 00:11:03,240
Very few animals
can survive here.
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00:11:08,040 --> 00:11:10,160
But this is one which does.
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00:11:13,080 --> 00:11:15,000
An arctic fox.
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00:11:17,960 --> 00:11:20,680
It has the warmest fur
of any mammal.
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00:11:21,680 --> 00:11:25,640
And it can survive blizzards
that may rage for days on end.
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00:11:30,120 --> 00:11:34,240
It must nonetheless
eventually eat something.
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00:11:35,600 --> 00:11:37,640
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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00:11:55,200 --> 00:11:58,040
Arctic foxes are wanderers.
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00:12:00,160 --> 00:12:05,120
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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00:12:24,960 --> 00:12:27,800
There might be something here.
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00:12:29,080 --> 00:12:32,240
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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00:12:37,440 --> 00:12:40,080
might indicate
the presence of prey.
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00:12:47,320 --> 00:12:49,720
Less than a metre
below the surface
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00:12:49,840 --> 00:12:53,000
may lie a hidden network
of tunnels,
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00:12:53,120 --> 00:12:56,880
shown here using
a special filming burrow.
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00:13:14,360 --> 00:13:16,720
Tiny arctic lemmings.
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00:13:19,520 --> 00:13:22,880
With a carpet
of edible moss beneath
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00:13:23,000 --> 00:13:25,480
and a thick blanket
of snow above...
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00:13:25,600 --> 00:13:28,800
The lemmings
spend their entire winter
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00:13:28,920 --> 00:13:30,440
hidden below the surface.
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00:13:32,000 --> 00:13:34,360
And here they breed.
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00:13:42,880 --> 00:13:45,000
For a hungry fox,
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a group of lemmings could be
a life-saving discovery...
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If it can catch one.
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00:13:56,760 --> 00:14:01,320
Lemming Burrows may extend
for up to 15 metres.
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00:14:09,160 --> 00:14:12,280
Pinpointing the position
of one of the inhabitants...
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00:14:13,560 --> 00:14:15,520
Is not easy.
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00:14:18,760 --> 00:14:21,880
An acute sense of hearing
is essential.
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00:14:26,200 --> 00:14:27,760
And the arctic fox
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has a special trick.
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00:14:43,320 --> 00:14:46,520
It doesn't always work
first time.
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00:14:51,760 --> 00:14:54,600
And it does require dedication.
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00:15:15,480 --> 00:15:19,520
With less than 25 lemmings
per square mile of tundra...
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00:15:20,560 --> 00:15:24,040
You have to persevere.
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00:15:32,560 --> 00:15:33,920
And at last...
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00:15:35,200 --> 00:15:37,040
One plump lemming.
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00:15:40,360 --> 00:15:44,200
The foxes' tenacity
and unique hunting skills
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00:15:44,320 --> 00:15:49,280
enable them to find prey
which few others could catch.
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00:16:05,440 --> 00:16:08,400
On the tundra's
southern fringes,
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00:16:08,520 --> 00:16:12,400
winter is significantly
less severe.
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00:16:16,000 --> 00:16:19,240
The slight increase
in annual sunlight
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00:16:19,360 --> 00:16:23,160
has enabled a stunted forest
to develop.
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00:16:40,960 --> 00:16:45,200
It's the northern edge of
the world's largest woodland...
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00:16:46,200 --> 00:16:48,720
The boreal forest.
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00:16:55,400 --> 00:16:59,240
750 billion trees.
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00:17:01,480 --> 00:17:04,400
A quarter of all the trees
on earth.
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00:17:07,400 --> 00:17:09,960
And it encircles the globe.
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00:17:12,280 --> 00:17:15,560
These forests store
twice as much carbon
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00:17:15,680 --> 00:17:17,480
as a tropical forest,
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00:17:17,600 --> 00:17:19,960
and they play a crucial part
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00:17:20,080 --> 00:17:23,680
in regulating the climate
of the entire planet.
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00:17:29,800 --> 00:17:31,920
One of the most remote tracts
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00:17:32,040 --> 00:17:35,160
stands in the far east
of Siberia.
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00:17:40,520 --> 00:17:44,480
It's cut off from the rest of
the world by towering peaks...
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00:17:45,640 --> 00:17:48,440
And precipitous valleys.
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00:17:52,360 --> 00:17:55,200
And it is the last stronghold
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of the world's rarest big cat.
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00:18:10,920 --> 00:18:13,160
The amur leopard.
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00:18:19,360 --> 00:18:22,640
Hunting has brought it
close to extinction.
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00:18:22,760 --> 00:18:26,600
Only 120 are left in the wild.
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00:18:29,800 --> 00:18:34,680
And this is one of the very few
ever to be caught on film.
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00:18:47,280 --> 00:18:51,920
Each must patrol a territory
of over 100 square miles
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00:18:52,040 --> 00:18:54,160
to find enough to eat.
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00:18:59,760 --> 00:19:01,720
In the cold of march,
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00:19:01,840 --> 00:19:05,080
prey is at its most scarce.
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00:19:17,320 --> 00:19:20,280
But leopards
are clever opportunists
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00:19:20,400 --> 00:19:22,920
and watch for clues.
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00:19:26,760 --> 00:19:28,000
Crows.
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00:19:29,040 --> 00:19:31,440
They, too, are looking for food.
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00:19:34,320 --> 00:19:38,440
And their calls tell him
that they've found something.
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00:19:54,640 --> 00:19:58,680
But he is not the only predator
here.
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00:20:00,000 --> 00:20:03,920
On one of the trees,
the marks of huge claws,
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ten centimetres long.
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00:20:09,840 --> 00:20:13,600
They've been made
by a hunter twice his size...
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00:20:20,720 --> 00:20:23,600
A siberian tiger.
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00:20:26,320 --> 00:20:29,800
Fewer than 500 remain
in the wild.
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00:20:36,120 --> 00:20:41,440
These two rare big cats
are sharing the same territory.
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00:20:46,560 --> 00:20:48,440
And fixed remote cameras
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00:20:48,560 --> 00:20:52,320
show that they even use exactly
the same trails.
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00:20:57,560 --> 00:21:01,000
But leopards know
they must be careful.
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00:21:06,400 --> 00:21:10,640
Siberian tigers are the biggest
of all the big cats,
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00:21:10,760 --> 00:21:13,280
and could kill a leopard...
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00:21:16,080 --> 00:21:18,120
Should they ever meet.
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00:21:29,440 --> 00:21:30,440
In winter,
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00:21:30,560 --> 00:21:34,720
many forest animals
rely on carrion for food.
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00:21:39,560 --> 00:21:41,760
And that includes leopards.
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00:21:52,000 --> 00:21:55,080
But he can't let down his guard.
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00:22:06,840 --> 00:22:08,640
The crows that led him here...
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00:22:08,760 --> 00:22:11,840
May also have alerted the tiger.
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00:22:42,800 --> 00:22:44,240
The crows are disturbed.
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00:22:45,960 --> 00:22:48,760
Another mouthful might be risky.
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00:23:04,520 --> 00:23:08,080
Survival sometimes
depends on knowing
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00:23:08,200 --> 00:23:09,680
when to leave.
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00:23:17,720 --> 00:23:20,840
Only a few choose
to take their chances here
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00:23:20,960 --> 00:23:23,400
in the depths of winter.
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00:23:24,800 --> 00:23:30,160
Elsewhere, vast swathes of
the forest remain eerily empty.
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00:23:34,480 --> 00:23:38,800
Above, there is
an othennorldly light show...
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00:23:43,720 --> 00:23:46,120
The Aurora borealis.
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00:23:52,760 --> 00:23:54,440
High in the sky,
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00:23:54,560 --> 00:23:58,080
electrically charged
solar particles from space
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00:23:58,200 --> 00:24:00,720
collide with
the earth's atmosphere
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00:24:00,840 --> 00:24:03,720
and create
this ethereal display.
197
00:24:16,000 --> 00:24:21,800
Meanwhile, in Canada, through
the six long months of winter,
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00:24:21,920 --> 00:24:26,760
life below ground
is biding its time.
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00:24:32,520 --> 00:24:36,080
The world's
most northerly turtle...
200
00:24:37,880 --> 00:24:39,200
The painted turtle...
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00:24:39,320 --> 00:24:43,040
Seen here
in a special filming chamber.
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00:24:44,400 --> 00:24:47,160
They hatched last Autumn,
but have remained
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00:24:47,280 --> 00:24:50,760
in a state of suspended
animation ever since.
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00:24:53,720 --> 00:24:56,320
Their hearts
have stopped beating...
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00:24:57,720 --> 00:25:00,120
And only their brains
have remained active,
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00:25:00,240 --> 00:25:02,640
and even then,
only very faintly.
207
00:25:06,200 --> 00:25:09,520
Painted turtles wait underground
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00:25:09,640 --> 00:25:12,080
for this most important
of moments...
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00:25:21,960 --> 00:25:25,240
The arrival of spring.
210
00:25:39,880 --> 00:25:43,160
In April,
the strengthening sunshine
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00:25:43,280 --> 00:25:47,240
triggers a miraculous
transformation.
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00:26:01,680 --> 00:26:05,880
The turtles' body temperature
rises just above freezing...
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00:26:11,600 --> 00:26:15,320
And their hearts
start to beat once more.
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00:26:30,560 --> 00:26:33,320
Slowly, they return to life.
215
00:26:35,320 --> 00:26:40,360
Thanks to this extraordinary
adaptation, these young turtles
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00:26:40,480 --> 00:26:44,200
get a valuable head start
in spring...
217
00:26:54,240 --> 00:26:57,760
And are one of the first
to emerge, ready to take
218
00:26:57,880 --> 00:27:01,520
full advantage of the forest's
renewed abundance.
219
00:27:09,520 --> 00:27:13,200
In just a matter of weeks,
the vast northern forests
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00:27:13,320 --> 00:27:15,360
flush green.
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00:27:30,760 --> 00:27:36,600
For Siberia's big cats, each
spring could bring new hope.
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00:27:40,000 --> 00:27:41,440
Cubs.
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00:27:43,680 --> 00:27:46,440
Each of them
increases the chance that,
224
00:27:46,560 --> 00:27:51,440
even at this very late stage,
both species might recover.
225
00:28:03,920 --> 00:28:08,040
By June, the northern forests
are full of life.
226
00:28:17,120 --> 00:28:21,680
But several thousands of miles
further north, in the tundra,
227
00:28:21,800 --> 00:28:24,720
the spring thaw
is only just beginning.
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00:28:31,920 --> 00:28:34,960
When it does,
under 24-hour daylight,
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00:28:35,080 --> 00:28:38,240
its impact is even more extreme.
230
00:28:43,920 --> 00:28:46,560
Five million square miles
of snow
231
00:28:46,680 --> 00:28:49,560
disappear in a matter of days.
232
00:29:00,200 --> 00:29:03,400
Ten centimetres beneath
the surface of the ground,
233
00:29:03,520 --> 00:29:07,920
a snow queen is waiting
to make her appearance.
234
00:29:13,280 --> 00:29:16,440
A lapland Bumblebee.
235
00:29:17,680 --> 00:29:19,960
She's barely alive.
236
00:29:22,040 --> 00:29:26,480
All the other members of her
colony were killed by the cold.
237
00:29:28,880 --> 00:29:32,760
She survived,
as Bumblebee queens do,
238
00:29:32,880 --> 00:29:37,720
thanks to her larger size,
her particularly thick fur,
239
00:29:37,840 --> 00:29:42,320
and a natural antifreeze
that she has in her body.
240
00:29:53,720 --> 00:29:56,320
As temperatures
continue to rise,
241
00:29:56,440 --> 00:29:59,200
she begins to thaw.
242
00:30:10,520 --> 00:30:13,040
She vibrates her flight muscles,
243
00:30:13,160 --> 00:30:15,320
which raises
her body temperature
244
00:30:15,440 --> 00:30:20,000
to over 30 degrees celsius
in just six minutes.
245
00:30:22,520 --> 00:30:25,800
There is no time to lose.
246
00:30:29,120 --> 00:30:33,000
She must now create
an entire colony.
247
00:30:41,400 --> 00:30:44,280
First, the queen must find
a drink of nectar
248
00:30:44,400 --> 00:30:46,360
to regain her strength...
249
00:30:50,120 --> 00:30:52,360
Travelling as much
as three miles a day
250
00:30:52,480 --> 00:30:55,520
to find the flowers
from which to collect it.
251
00:31:04,960 --> 00:31:06,800
She works tirelessly.
252
00:31:09,560 --> 00:31:11,760
As well as high-energy nectar...
253
00:31:13,760 --> 00:31:16,040
There's pollen to be gathered.
254
00:31:29,600 --> 00:31:35,200
Back underground, she uses the
pollen to build a waxy cocoon.
255
00:31:37,520 --> 00:31:40,800
And in it,
she deposits tiny eggs.
256
00:31:44,600 --> 00:31:47,280
Had she laid them
directly on the frozen ground,
257
00:31:47,400 --> 00:31:49,600
the cold would have killed them.
258
00:31:49,720 --> 00:31:51,760
And now she warms them
259
00:31:51,880 --> 00:31:54,240
by pulsating her body.
260
00:32:03,640 --> 00:32:06,040
She has also constructed
a little pot
261
00:32:06,160 --> 00:32:08,120
in which she stores nectar
262
00:32:08,240 --> 00:32:11,120
to provide her with a drink
when she needs it.
263
00:32:17,280 --> 00:32:19,200
For the next three weeks...
264
00:32:20,400 --> 00:32:21,880
This single mother
265
00:32:22,000 --> 00:32:25,080
works around the clock,
gathering nectar
266
00:32:25,200 --> 00:32:26,920
to top up her pot...
267
00:32:35,600 --> 00:32:37,280
And vibrating her body
268
00:32:37,400 --> 00:32:40,840
to prevent her developing young
from freezing to death.
269
00:32:52,600 --> 00:32:56,600
Eventually,
a new generation of bees
270
00:32:56,720 --> 00:32:59,240
starts to emerge.
271
00:33:05,920 --> 00:33:09,920
She leads each young worker
to her honey pot
272
00:33:10,040 --> 00:33:12,680
and encourages it to drink.
273
00:33:19,400 --> 00:33:22,760
By the end
of the following week,
274
00:33:22,880 --> 00:33:26,440
the number in her little colony
has increased to eight.
275
00:33:28,880 --> 00:33:31,840
Her timing has been perfect.
276
00:33:37,960 --> 00:33:41,000
The tundra is now in full bloom.
277
00:33:48,680 --> 00:33:51,880
And the Bumblebee families
help to pollinate
278
00:33:52,000 --> 00:33:55,560
the largest wild-flower Meadow
on earth.
279
00:34:10,400 --> 00:34:15,040
But the summer here is one
of the shortest on the planet,
280
00:34:15,160 --> 00:34:17,880
and all of
the tundra's residents
281
00:34:18,000 --> 00:34:20,400
are now racing to breed.
282
00:34:23,920 --> 00:34:28,480
Alaskan snowy owls have
a brood of six fluffy chicks
283
00:34:28,600 --> 00:34:31,920
and only eight weeks
in which to raise them.
284
00:34:40,600 --> 00:34:44,960
The parents provide them
with 30 lemmings a day...
285
00:34:46,400 --> 00:34:48,880
For the chicks will need
to triple their weight
286
00:34:49,000 --> 00:34:51,080
before they reach independence.
287
00:35:00,960 --> 00:35:05,520
Unusually for an owl,
snowies hunt by day.
288
00:35:10,040 --> 00:35:12,040
And over the next two weeks,
289
00:35:12,160 --> 00:35:15,800
they take full advantage of
the arctic's continuous light.
290
00:35:22,160 --> 00:35:28,280
But this morning, the female
returns to an empty nest.
291
00:35:34,360 --> 00:35:36,960
Her chicks are
nowhere to be seen.
292
00:35:46,960 --> 00:35:48,920
They're hiding.
293
00:35:54,160 --> 00:35:58,320
They're so big, the whole group
might be spotted by predators,
294
00:35:58,440 --> 00:36:02,280
so they have scattered
across the tundra.
295
00:36:08,520 --> 00:36:12,840
But that makes feeding them all
much harder work.
296
00:36:24,560 --> 00:36:26,560
Over 600 meals later,
297
00:36:26,680 --> 00:36:29,280
the parents' labours
are starting to pay off...
298
00:36:31,400 --> 00:36:35,480
As the chicks stretch
their newly developed wings.
299
00:36:45,120 --> 00:36:49,400
Just a month is left
before winter returns.
300
00:37:07,000 --> 00:37:08,360
Two weeks more,
301
00:37:08,480 --> 00:37:11,120
and their transformation
is almost complete.
302
00:37:13,280 --> 00:37:15,640
The chicks' wings
might at last be able
303
00:37:15,760 --> 00:37:18,920
to do more than just
lift them from the ground.
304
00:37:24,840 --> 00:37:26,480
Getting there!
305
00:37:32,920 --> 00:37:34,840
Keep going!
306
00:37:38,840 --> 00:37:40,240
Airborne!
307
00:37:40,360 --> 00:37:44,000
The youngsters are ready
for independence.
308
00:37:46,480 --> 00:37:50,320
And the exhausted parents
can take a well-earned rest.
309
00:37:56,400 --> 00:37:59,400
The tundra has come to life
once again.
310
00:38:01,600 --> 00:38:04,920
But in the longer term,
its very foundations
311
00:38:05,040 --> 00:38:06,920
are now at risk.
312
00:38:21,400 --> 00:38:24,560
The ground itself is giving way.
313
00:38:37,520 --> 00:38:43,320
In some places, it's dropped
by more than 60 metres.
314
00:38:47,400 --> 00:38:51,320
Grasslands that once supported
thousands of different species
315
00:38:51,440 --> 00:38:54,320
have become wastelands.
316
00:39:01,520 --> 00:39:04,000
Arctic temperatures are rising
317
00:39:04,120 --> 00:39:07,240
as a consequence
of climate change.
318
00:39:11,840 --> 00:39:14,680
The deep soil,
which has been frozen solid
319
00:39:14,800 --> 00:39:18,120
for thousands of years,
the permafrost,
320
00:39:18,240 --> 00:39:22,320
is now thawing at a rate
never witnessed before.
321
00:39:28,440 --> 00:39:30,280
Without the ice
to bind it together,
322
00:39:30,400 --> 00:39:33,040
the ground becomes unstable.
323
00:39:39,800 --> 00:39:43,360
In Canada, thousands of tonnes
of the tundra
324
00:39:43,480 --> 00:39:46,000
have collapsed
in a matter of weeks.
325
00:39:59,760 --> 00:40:04,000
And in Siberia,
huge scars are appearing.
326
00:40:10,240 --> 00:40:14,160
By the end of the century,
an area of arctic permafrost
327
00:40:14,280 --> 00:40:16,720
one third of the size of Europe
328
00:40:16,840 --> 00:40:18,880
could have thawed.
329
00:40:24,440 --> 00:40:25,800
The warming of the tundra
330
00:40:25,920 --> 00:40:29,400
is having a profound impact
on its wildlife.
331
00:40:31,960 --> 00:40:37,240
For millennia, caribou
have made annual migrations.
332
00:40:42,200 --> 00:40:43,400
Every summer,
333
00:40:43,520 --> 00:40:46,760
driven by the seasonal changes
of the far north,
334
00:40:46,880 --> 00:40:50,440
and following
long-established pathways,
335
00:40:50,560 --> 00:40:54,840
they have trekked
almost 400 miles north.
336
00:41:11,920 --> 00:41:18,120
This herd alone in north-east
Alaska numbers over 200,000.
337
00:41:26,920 --> 00:41:28,200
Their destination
338
00:41:28,320 --> 00:41:30,160
is a vast wilderness
339
00:41:30,280 --> 00:41:34,120
known as the arctic
national wildlife refuge.
340
00:41:45,680 --> 00:41:49,280
These summer pastures
provide rich grazing,
341
00:41:49,400 --> 00:41:53,480
just what's needed
to raise newborn calves.
342
00:42:02,760 --> 00:42:05,680
This one, fattening up
on its mother's milk,
343
00:42:05,800 --> 00:42:09,080
would normally double
its weight in just a few weeks.
344
00:42:19,600 --> 00:42:23,320
But now grazing time
is being disrupted.
345
00:42:29,920 --> 00:42:32,880
In summer, the tundra
becomes waterlogged.
346
00:42:36,120 --> 00:42:39,280
These are excellent
breeding conditions
347
00:42:39,400 --> 00:42:42,640
for mosquitoes
and other biting insects.
348
00:42:51,080 --> 00:42:53,080
But as the climate warms,
349
00:42:53,200 --> 00:42:56,800
there are concerns
that insects will breed earlier
350
00:42:56,920 --> 00:42:59,680
and eventually reach
plague proportions
351
00:42:59,800 --> 00:43:02,240
just as the caribou
need to feed.
352
00:43:06,480 --> 00:43:08,320
Individual animals could lose
353
00:43:08,440 --> 00:43:13,160
a quarter of a pint of blood
a day to biting insects.
354
00:43:18,960 --> 00:43:21,960
So the caribou may
end their grazing early
355
00:43:22,080 --> 00:43:26,200
and head for cooler,
mosquito-free pastures.
356
00:43:34,320 --> 00:43:35,960
But to get to such places,
357
00:43:36,080 --> 00:43:40,120
they will have to cross rivers
swollen by seasonal runoff.
358
00:43:55,040 --> 00:43:59,600
For a young calf, a deep river
crossing is very dangerous.
359
00:44:05,800 --> 00:44:09,480
He does what he can
to stay close to his mother.
360
00:44:19,280 --> 00:44:21,520
But he doesn't have the strength
361
00:44:21,640 --> 00:44:24,280
to resist
the fast-moving current.
362
00:45:16,960 --> 00:45:20,200
He is one of the lucky ones.
363
00:45:24,400 --> 00:45:26,880
Reunited with his mother,
364
00:45:27,000 --> 00:45:30,640
he can continue
on his journey with the herd.
365
00:45:39,800 --> 00:45:43,200
But other calves
are less fortunate...
366
00:45:45,880 --> 00:45:49,800
And must now
fend for themselves.
367
00:46:01,200 --> 00:46:05,320
Some are too exhausted
to take another step.
368
00:46:13,400 --> 00:46:16,800
But this is not a safe place
to take a rest.
369
00:46:42,200 --> 00:46:43,920
Grizzly bears.
370
00:46:48,080 --> 00:46:49,480
For the past few weeks,
371
00:46:49,600 --> 00:46:52,600
there has been little food
for them on the tundra.
372
00:46:55,360 --> 00:46:58,120
And this one
is extremely hungry.
373
00:47:14,600 --> 00:47:18,000
He's looking
for the weak and weary.
374
00:47:27,720 --> 00:47:30,600
And he's found one...
375
00:47:42,640 --> 00:47:44,840
Too tired to flee...
376
00:47:48,040 --> 00:47:50,360
And too weak to resist.
377
00:48:02,040 --> 00:48:03,640
The herd's finally reached
378
00:48:03,760 --> 00:48:06,160
the northern limits
of its range.
379
00:48:11,240 --> 00:48:14,560
These coastal pastures
bordering the arctic ocean
380
00:48:14,680 --> 00:48:17,440
remain cool enough
to provide relief
381
00:48:17,560 --> 00:48:19,640
from the swarms of insects.
382
00:48:24,560 --> 00:48:28,280
Mothers and calves
can finally feed in peace.
383
00:48:35,440 --> 00:48:39,880
For now,
this immense herd is stable.
384
00:48:42,080 --> 00:48:46,760
But in the long term,
its survival is now uncertain.
385
00:48:52,520 --> 00:48:55,400
The seasonal extremes
of the far north
386
00:48:55,520 --> 00:48:59,120
have always tested
its inhabitants to the limits.
387
00:49:01,360 --> 00:49:04,040
But climate change
could present them
388
00:49:04,160 --> 00:49:06,280
with one challenge too many.
389
00:49:08,240 --> 00:49:11,200
Only if we can
mitigate its effects
390
00:49:11,320 --> 00:49:13,920
will the remarkable
wildlife here
391
00:49:14,040 --> 00:49:17,040
stand a chance of survival.
392
00:49:36,240 --> 00:49:38,840
Filming in the extremes
of the far north...
393
00:49:39,920 --> 00:49:42,800
The team's greatest
challenge was to capture
394
00:49:42,920 --> 00:49:45,800
the epic showdown
between super-packs of wolves
395
00:49:45,920 --> 00:49:48,400
and bison in midwinter,
396
00:49:52,120 --> 00:49:53,280
The crew travelled to
397
00:49:53,400 --> 00:49:55,920
wood buffalo national park
in northern Canada,
398
00:49:56,040 --> 00:49:59,680
a remote wilderness
the size of Switzerland.
399
00:50:03,240 --> 00:50:05,760
To stand a chance
of filming this drama,
400
00:50:05,880 --> 00:50:07,640
they must take to the skies.
401
00:50:09,120 --> 00:50:10,360
Drawing on local knowledge,
402
00:50:10,480 --> 00:50:13,960
pilot Matt erhardt
helps to pinpoint
403
00:50:14,080 --> 00:50:16,080
one of the last
free-roaming herds of bison
404
00:50:16,200 --> 00:50:18,920
and the wolves that specialise
in hunting them.
405
00:50:22,600 --> 00:50:24,400
Some of the wolves
have run fonnards.
406
00:50:24,520 --> 00:50:26,600
Just have all your kit
ready to go.
407
00:50:28,920 --> 00:50:30,240
With a positive sighting,
408
00:50:30,360 --> 00:50:32,360
it's time to mobilise
the film crew.
409
00:50:35,080 --> 00:50:37,720
Cameraman Jamie mcpherson
has rigged the helicopter
410
00:50:37,840 --> 00:50:40,480
with a gyrostabilised
camera system,
411
00:50:40,600 --> 00:50:43,840
enabling him to capture
rock-steady images
412
00:50:43,960 --> 00:50:45,560
from a safe distance.
413
00:50:45,680 --> 00:50:47,800
You'd think filming
from a helicopter's easy,
414
00:50:47,920 --> 00:50:49,336
because you can just
fly around and film stuff.
415
00:50:49,360 --> 00:50:50,920
But you've got to be
incredibly careful,
416
00:50:51,040 --> 00:50:52,160
not influence the behaviour,
417
00:50:52,200 --> 00:50:53,840
not scare the wolves
or the bison.
418
00:50:58,320 --> 00:51:00,640
There we go. Yeah, that is them.
419
00:51:01,800 --> 00:51:03,040
- It's a big pack.
- Yeah.
420
00:51:05,200 --> 00:51:06,536
They're really chilled out
with the helicopter.
421
00:51:06,560 --> 00:51:07,840
Really encouraging.
422
00:51:10,800 --> 00:51:12,640
But before Jamie
can start filming,
423
00:51:12,760 --> 00:51:15,880
the chopper must first drop
the accompanying ground crew.
424
00:51:16,000 --> 00:51:18,160
- Good luck.
- Ok.
425
00:51:23,440 --> 00:51:25,080
We got put down
426
00:51:25,200 --> 00:51:26,920
in this vast open space,
427
00:51:27,040 --> 00:51:29,560
and now we're going to
try and hike in and see
428
00:51:29,680 --> 00:51:30,920
if we can get close to them,
429
00:51:31,040 --> 00:51:32,680
or hopefully
they'll get close to us.
430
00:51:34,440 --> 00:51:38,440
To intercept the pack, the team
must scramble into position.
431
00:51:42,280 --> 00:51:44,800
But trudging through
knee-deep snow
432
00:51:44,920 --> 00:51:46,680
is hard going.
433
00:51:51,280 --> 00:51:53,640
Every time I catch up with
Justin, he just keeps on going.
434
00:51:53,760 --> 00:51:56,160
He's a machine!
435
00:52:01,840 --> 00:52:03,000
Yeah, go ahead, Matt.
436
00:52:03,120 --> 00:52:05,120
Over radio:
They're starting to head
437
00:52:05,240 --> 00:52:06,616
a little bit towards
the north-west,
438
00:52:06,640 --> 00:52:08,720
so they're starting to
move away from you.
439
00:52:10,160 --> 00:52:11,480
Oh, goddamn it!
440
00:52:13,200 --> 00:52:15,480
David: The ground crew
will have to dig deep
441
00:52:15,600 --> 00:52:18,280
if they're to film
the fleet-footed wolves.
442
00:52:22,880 --> 00:52:24,280
Over the following week,
443
00:52:24,400 --> 00:52:26,920
Jamie manages to track
the wolf pack
444
00:52:27,040 --> 00:52:28,840
from the comfort
of the helicopter...
445
00:52:30,200 --> 00:52:32,080
While down on the ground,
446
00:52:32,200 --> 00:52:35,680
Justin and will are having
a tougher time of it.
447
00:52:35,800 --> 00:52:37,680
- Ohhh!
- It's really
448
00:52:37,800 --> 00:52:40,560
incredibly awkward
getting around.
449
00:52:40,680 --> 00:52:43,400
Even lunch offers
little consolation.
450
00:52:43,520 --> 00:52:44,640
It's frozen bread,
451
00:52:44,760 --> 00:52:47,680
frozen brie and frozen pickle.
452
00:52:49,040 --> 00:52:51,080
And with no wolf activity
visible from the air,
453
00:52:51,200 --> 00:52:53,640
Jamie is soon grounded.
454
00:52:53,760 --> 00:52:55,800
Yeah, I'm just
looking for an update.
455
00:53:04,720 --> 00:53:07,960
The winter weather
takes a turn for the worse.
456
00:53:08,080 --> 00:53:11,080
It's snowing, and it's at
a temperature where it could
457
00:53:11,200 --> 00:53:13,880
potentially stick to the blades
and become really dangerous.
458
00:53:15,320 --> 00:53:19,680
For the next few days, the crew
are forced to sit it out.
459
00:53:25,360 --> 00:53:27,600
Finally, the skies clear.
460
00:53:28,600 --> 00:53:30,960
But after nearly three weeks
on location,
461
00:53:31,080 --> 00:53:34,400
there's precious little
filming time left.
462
00:53:34,520 --> 00:53:36,800
We've got one last shot
463
00:53:36,920 --> 00:53:38,840
to get what we're looking for.
464
00:53:38,960 --> 00:53:42,280
And just hoping that it comes
together at the last minute.
465
00:53:49,600 --> 00:53:50,880
There, there's the trail there,
466
00:53:51,000 --> 00:53:52,960
so they're on the West Side
of that trail there.
467
00:53:56,520 --> 00:53:58,720
Soon enough,
they find the bison,
468
00:53:58,840 --> 00:54:00,680
along with wolves
469
00:54:00,800 --> 00:54:02,440
who appear to be
in hunting mode.
470
00:54:02,560 --> 00:54:06,440
The spotter plane just found
the wolves with the bison,
471
00:54:06,560 --> 00:54:08,920
so we're scrambling to get
there as quick as we can.
472
00:54:30,920 --> 00:54:32,800
There's something about
473
00:54:32,920 --> 00:54:36,280
being in the presence of prey
and predator on the ground
474
00:54:36,400 --> 00:54:39,880
like this which is very special.
475
00:54:40,000 --> 00:54:45,240
Justin is in prime position
to capture the showdown.
476
00:54:51,800 --> 00:54:53,080
As a chase begins,
477
00:54:53,200 --> 00:54:56,720
Jamie picks up the action
from the air.
478
00:55:04,080 --> 00:55:05,760
It'd be amazing
if we could get round that.
479
00:55:11,160 --> 00:55:13,920
In a stop-start pursuit
lasting an entire day,
480
00:55:14,040 --> 00:55:18,560
Jamie manages to record
the full jaw-dropping drama.
481
00:55:21,120 --> 00:55:22,456
They've definitely got
that female.
482
00:55:22,480 --> 00:55:24,600
I think they're going to
bring it down.
483
00:55:28,880 --> 00:55:31,960
Perfect, Jim. We got it.
484
00:55:33,320 --> 00:55:34,920
With the hunt nearly over,
485
00:55:35,040 --> 00:55:37,560
the crew reposition Justin
once more.
486
00:55:47,480 --> 00:55:51,240
We got on the ground
just in time to capture
487
00:55:51,360 --> 00:55:53,320
from a really far distance
488
00:55:53,440 --> 00:55:56,360
the last moments
of the bison's life.
489
00:55:59,560 --> 00:56:01,760
There's a moment of confliction
490
00:56:01,880 --> 00:56:05,120
between your loyalty
for each animal.
491
00:56:05,240 --> 00:56:10,480
One is filled with a mixture of
both celebration for the wolves
492
00:56:10,600 --> 00:56:15,320
but a sadness. Both exist
somehow simultaneously.
493
00:56:20,640 --> 00:56:23,640
Bearing witness to
this rarely seen age-old battle
494
00:56:23,760 --> 00:56:27,040
between predator and prey
leaves the crew
495
00:56:27,160 --> 00:56:30,160
with an appreciation of
just how challenging life is
496
00:56:30,280 --> 00:56:33,320
in the frozen extremes
of the far north.
35699
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