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The Arctic has always
been the toughest test,
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00:00:20,882 --> 00:00:24,300
no more so than
in the far corner of Alaska
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00:00:24,334 --> 00:00:28,235
called the Arctic National
Wildlife Refuge.
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00:00:28,269 --> 00:00:31,376
Thousands of caribou face the cold...
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00:00:33,240 --> 00:00:36,036
the terrain...
10
00:00:36,070 --> 00:00:41,075
and formidable predators
to reach one special place
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00:00:41,110 --> 00:00:43,146
at just the right time...
12
00:00:43,181 --> 00:00:47,426
a vast, beautiful plain
on the edge of the Arctic Ocean.
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00:00:49,980 --> 00:00:52,259
Here, they give birth.
14
00:00:55,124 --> 00:00:58,575
This is the story of the last
great land migration
15
00:00:58,610 --> 00:01:00,129
in North America.
16
00:01:02,441 --> 00:01:07,653
And of how every Arctic creature
is now on a daunting journey
17
00:01:07,688 --> 00:01:11,899
from a timeless past
into a vastly different future.
18
00:01:44,242 --> 00:01:46,140
On the top of the world,
19
00:01:46,175 --> 00:01:48,867
it is still the ice age.
20
00:02:01,121 --> 00:02:04,262
It's northern Alaska in winter.
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00:02:04,296 --> 00:02:06,643
The temperature drops to 50 below.
22
00:02:18,207 --> 00:02:21,796
Frozen rivers curl north
from the Brooks Range
23
00:02:21,831 --> 00:02:25,041
and down to a plain
stretching to the Beaufort Sea
24
00:02:25,075 --> 00:02:28,113
and the Arctic Ocean, now locked in ice.
25
00:02:31,806 --> 00:02:34,326
This vast stretch of white mountains,
26
00:02:34,361 --> 00:02:36,501
tundra, and icy rivers,
27
00:02:36,535 --> 00:02:39,987
forms one of the world's
most important wildernesses...
28
00:02:40,021 --> 00:02:43,680
the Arctic National Wildlife Refuge.
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00:02:43,715 --> 00:02:46,890
It's a home for courageous
creatures from another time.
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00:02:51,240 --> 00:02:54,139
This wildlife community will face a year
31
00:02:54,174 --> 00:02:55,761
of difficult decisions.
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00:02:59,213 --> 00:03:03,666
Hundreds of miles southeast,
bravest of all perhaps,
33
00:03:03,700 --> 00:03:07,221
is a pregnant caribou.
34
00:03:07,256 --> 00:03:10,224
She's part of the Porcupine caribou herd
35
00:03:10,259 --> 00:03:13,434
and will undertake the longest
annual land migration
36
00:03:13,469 --> 00:03:15,540
on the planet.
37
00:03:15,574 --> 00:03:19,233
In her lifetime, she's likely
to walk the same distance
38
00:03:19,268 --> 00:03:23,306
as a complete circuit of the globe.
39
00:03:23,341 --> 00:03:26,344
It's December, and the caribou
are waiting,
40
00:03:26,378 --> 00:03:29,174
eating lichen in the twilight.
41
00:03:29,209 --> 00:03:33,454
The journey ahead needs precise timing.
42
00:03:33,489 --> 00:03:35,663
She'll march through forests,
43
00:03:35,698 --> 00:03:37,941
over mountains, across rivers,
44
00:03:37,976 --> 00:03:39,633
to the coastal plain.
45
00:03:39,667 --> 00:03:43,464
It's a round trip
of almost a thousand miles.
46
00:03:47,330 --> 00:03:49,988
Some 160,000 caribou
47
00:03:50,022 --> 00:03:51,886
will walk from their wintering grounds
48
00:03:51,921 --> 00:03:54,682
in the Yukon and Northwest Territories
49
00:03:54,717 --> 00:03:58,030
to their calving grounds
in the Wildlife Refuge.
50
00:04:02,518 --> 00:04:05,037
The Brooks Range stands in their way,
51
00:04:05,072 --> 00:04:08,731
running parallel to the coast.
52
00:04:08,765 --> 00:04:12,390
The sun sets for the last time
until the New Year.
53
00:04:23,435 --> 00:04:26,990
The only sunlight is reflected
by a wintry moon.
54
00:04:35,447 --> 00:04:37,449
Hundreds of miles above,
55
00:04:37,484 --> 00:04:41,073
solar radiation fires up the ionosphere,
56
00:04:41,108 --> 00:04:42,696
and the ghostly aurora.
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00:04:58,367 --> 00:05:00,576
This is a world of huge planetary
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00:05:00,610 --> 00:05:04,131
forces in constant flux.
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00:05:04,165 --> 00:05:08,687
This is nature at its most
spectacular and extreme.
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00:05:20,389 --> 00:05:24,462
A dawn twilight returns in January.
61
00:05:32,815 --> 00:05:35,680
Blizzards blast the tundra.
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00:05:35,714 --> 00:05:40,098
Most animals have left or are
hibernating under the deep snow,
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00:05:40,132 --> 00:05:41,858
but musk ox remain.
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00:05:47,795 --> 00:05:51,972
They are loyal to a home range
and won't leave.
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00:05:52,006 --> 00:05:54,215
They rarely visit the valley.
66
00:05:54,250 --> 00:05:55,872
The snow is too deep,
67
00:05:55,907 --> 00:05:59,117
and they can't dig out the frozen grass.
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00:05:59,151 --> 00:06:01,844
Even up here, it's hard work.
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00:06:07,574 --> 00:06:11,163
Winters seem to be more erratic recently,
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00:06:11,198 --> 00:06:13,649
on average more than eight degrees warmer
71
00:06:13,683 --> 00:06:17,411
than 50 years ago, which sounds better,
72
00:06:17,446 --> 00:06:21,173
but now there's freezing rain
on top of heavier snowfall.
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00:06:24,453 --> 00:06:26,938
The caribou are becoming restless.
74
00:06:32,530 --> 00:06:36,430
Her belly is beginning to swell
with her unborn calf.
75
00:06:41,918 --> 00:06:46,992
She's searching for reindeer
lichen, her winter food.
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00:06:47,027 --> 00:06:50,168
She's a reindeer as much as a caribou.
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00:06:50,202 --> 00:06:52,239
They are the same species.
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00:06:57,693 --> 00:07:01,766
She digs through snow like the musk ox.
79
00:07:01,800 --> 00:07:03,526
For a prospective mother,
80
00:07:03,561 --> 00:07:07,323
finding enough food
is her principal focus.
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00:07:07,357 --> 00:07:09,498
But it's not her only worry.
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00:07:20,819 --> 00:07:23,166
It's a lone wolf.
83
00:07:35,834 --> 00:07:39,355
The caribou's instinct
is to stay on the move.
84
00:07:39,389 --> 00:07:42,082
Somewhere has to be better than this.
85
00:07:47,881 --> 00:07:51,125
But migration is not blind instinct.
86
00:07:51,160 --> 00:07:55,095
It's a series of collective
decisions based on subtle clues
87
00:07:55,129 --> 00:07:58,788
to weather patterns and journey times.
88
00:07:58,823 --> 00:08:00,894
Every year is different.
89
00:08:04,069 --> 00:08:06,727
The wolf has choices to make, too.
90
00:08:06,762 --> 00:08:10,248
He can follow the caribou,
but they move fast,
91
00:08:10,282 --> 00:08:12,422
and the journey is too far.
92
00:08:18,152 --> 00:08:21,017
The first birth of spring.
93
00:08:21,052 --> 00:08:22,571
It's not a caribou,
94
00:08:22,605 --> 00:08:26,920
but a newborn musk ox, a 30-pound baby,
95
00:08:26,954 --> 00:08:30,786
delivered straight onto the snow.
96
00:08:30,820 --> 00:08:33,064
The family surrounds her,
97
00:08:33,098 --> 00:08:36,377
a protection from dangers
outside their circle.
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00:08:48,666 --> 00:08:53,636
But within hours, the calf wants out.
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00:08:53,671 --> 00:08:56,190
There's a beautiful new world to explore.
100
00:09:04,440 --> 00:09:07,339
Every calf is precious.
101
00:09:07,374 --> 00:09:10,170
Musk ox were hunted
to extinction in Alaska
102
00:09:10,204 --> 00:09:12,103
in the 1860s,
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00:09:12,137 --> 00:09:15,934
but were brought back in the 1930s.
104
00:09:15,969 --> 00:09:19,075
There are now a few thousand
here in Alaska.
105
00:09:24,011 --> 00:09:27,428
A little river gully is a new
adventure for the calf.
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00:09:33,055 --> 00:09:37,818
Once in, getting back out is harder.
107
00:09:49,692 --> 00:09:51,591
The mother won't follow.
108
00:09:51,625 --> 00:09:53,903
She doesn't know how deep the snow is
109
00:09:53,938 --> 00:09:55,664
and could easily get stuck.
110
00:09:59,806 --> 00:10:02,567
She tracks her calf from the bank.
111
00:10:11,576 --> 00:10:13,820
The calf discovers...
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00:10:13,854 --> 00:10:15,649
ice.
113
00:10:35,462 --> 00:10:38,638
There's a physical urgency
to find your feet here...
114
00:10:41,571 --> 00:10:44,920
...but perhaps a greater
mental urgency for the calf
115
00:10:44,954 --> 00:10:47,267
to figure out her world.
116
00:10:51,271 --> 00:10:54,101
The patient mother waits...
117
00:10:54,136 --> 00:10:56,690
and her calf finds a way out.
118
00:11:17,297 --> 00:11:19,368
She's got maybe another two years
119
00:11:19,402 --> 00:11:21,819
looking after this youngster.
120
00:11:21,853 --> 00:11:25,270
The herd of about 15
will protect the calves
121
00:11:25,305 --> 00:11:29,861
and search for food around their
large home range until summer.
122
00:11:40,423 --> 00:11:44,600
The caribou have left
the winter woodland far behind,
123
00:11:44,634 --> 00:11:46,844
and are heading north.
124
00:11:56,785 --> 00:11:59,649
By April, the snow is starting to melt,
125
00:11:59,684 --> 00:12:03,757
and many rivers run earlier
than a decade ago.
126
00:12:03,792 --> 00:12:08,935
Spring is moving north faster,
and the caribou need to keep up.
127
00:12:16,977 --> 00:12:20,291
The herd heads on for about
a hundred miles,
128
00:12:20,325 --> 00:12:21,982
then will turn west
129
00:12:22,017 --> 00:12:24,985
towards the Arctic National
Wildlife Refuge.
130
00:12:30,266 --> 00:12:34,167
It's the end of April.
They are over halfway.
131
00:12:34,201 --> 00:12:35,789
The mothers will all give birth
132
00:12:35,824 --> 00:12:38,585
within days of the third of June.
133
00:12:38,619 --> 00:12:40,138
Six weeks to go.
134
00:12:48,768 --> 00:12:52,495
Golden eagles nest along the route.
135
00:12:52,530 --> 00:12:54,049
They came up from the south
136
00:12:54,083 --> 00:12:56,810
and established territories in March,
137
00:12:56,845 --> 00:13:00,469
feeding on hares, ptarmigan, or marmots.
138
00:13:02,851 --> 00:13:08,546
The eagle pair returns to the
same spectacular nest each year.
139
00:13:08,580 --> 00:13:13,551
They are loyal to a site
decided over a decade ago.
140
00:13:13,585 --> 00:13:16,347
But the calendar has changed
a lot since then.
141
00:13:28,221 --> 00:13:31,500
By early May, the chicks
are near fledging,
142
00:13:31,534 --> 00:13:34,572
and the caribou herd has already passed.
143
00:13:42,994 --> 00:13:45,617
A ground squirrel is breakfast.
144
00:13:58,354 --> 00:14:00,701
It will take a new generation of eagles
145
00:14:00,736 --> 00:14:04,705
to make the huge adjustment
to the changes unfolding here.
146
00:14:08,330 --> 00:14:13,542
A lone wolf has stuck with
the herd for many miles.
147
00:14:31,111 --> 00:14:35,150
Caribou from a broad area either
side of the Canadian border
148
00:14:35,184 --> 00:14:37,807
are converging on the same route.
149
00:14:37,842 --> 00:14:41,466
They'll navigate around the
eastern end of the Brooks Range,
150
00:14:41,501 --> 00:14:44,400
about 40 miles from the Arctic shore.
151
00:14:57,551 --> 00:15:00,830
In a few places, the route has bottlenecks
152
00:15:00,865 --> 00:15:03,212
around rivers and lakes.
153
00:15:18,365 --> 00:15:22,542
This migration of Arctic caribou
is compared to wildebeest
154
00:15:22,576 --> 00:15:26,615
on the African savanna,
and so the coastal plain
155
00:15:26,649 --> 00:15:30,619
is sometimes called America's Serengeti.
156
00:15:42,872 --> 00:15:44,978
As the herd funnels through the foothills
157
00:15:45,013 --> 00:15:46,738
of the Brooks Range,
158
00:15:46,773 --> 00:15:49,741
the wolf briefly gains an advantage.
159
00:15:59,648 --> 00:16:03,997
The weaker calves from last year
are struggling to keep up.
160
00:16:04,032 --> 00:16:06,448
There's been little time to stop and eat.
161
00:16:13,593 --> 00:16:16,009
As long as the herd stays watchful
162
00:16:16,044 --> 00:16:19,116
and maintains a distance, they're safe.
163
00:16:28,090 --> 00:16:30,955
Caribou are faster.
164
00:16:30,990 --> 00:16:33,268
The wolf is a tactician,
165
00:16:33,302 --> 00:16:36,616
but tactics are hard if you work alone.
166
00:16:58,086 --> 00:17:02,055
Here is an unparalleled amount
of food on the hoof,
167
00:17:02,090 --> 00:17:06,301
but to this lone wolf, it might
as well not be here at all.
168
00:17:19,762 --> 00:17:24,629
By May, spring has reached the
Arctic National Wildlife Refuge.
169
00:17:26,562 --> 00:17:30,739
Life here has slept under snow
for eight months.
170
00:17:35,709 --> 00:17:39,334
Plovers and redpolls arrive to nest,
171
00:17:39,368 --> 00:17:41,991
part of a massive aerial migration.
172
00:17:46,272 --> 00:17:50,379
Millions of snow geese
leave California or Texas
173
00:17:50,414 --> 00:17:54,349
and are on their way
to the Arctic Islands of Canada.
174
00:17:54,383 --> 00:17:57,179
They'll stop off here on their way back.
175
00:18:09,295 --> 00:18:12,677
Sandpipers are part of
the worldwide event.
176
00:18:18,718 --> 00:18:22,480
Golden plovers set off from Argentina.
177
00:18:22,515 --> 00:18:26,898
Terns, loons, and songbirds
come from Antarctica
178
00:18:26,933 --> 00:18:30,005
or Africa or East Asia.
179
00:18:30,039 --> 00:18:33,042
Hundreds of species cross the planet
180
00:18:33,077 --> 00:18:35,493
on their way to the Arctic north.
181
00:18:49,300 --> 00:18:54,616
A world of birds is heading to
the summer paradise of Alaska.
182
00:19:07,007 --> 00:19:12,323
The golden plover couple have
arranged a nest on the ground,
183
00:19:12,358 --> 00:19:15,878
laid their eggs,
and are raising their chicks.
184
00:19:29,340 --> 00:19:33,068
The parents provide some
protection against Arctic foxes
185
00:19:33,102 --> 00:19:35,208
or predatory birds,
186
00:19:35,243 --> 00:19:38,763
but it's mainly just warmth
under a camouflaged wing.
187
00:19:49,636 --> 00:19:53,537
Once thawed out, the chicks have
to get back to finding food
188
00:19:53,571 --> 00:19:55,090
for themselves.
189
00:20:08,414 --> 00:20:11,382
The mother leaves after a couple of weeks,
190
00:20:11,417 --> 00:20:14,834
and the father follows a week or so later.
191
00:20:14,868 --> 00:20:17,146
But the chicks stay longer
192
00:20:17,181 --> 00:20:20,598
and have to find their own way
back to South America.
193
00:20:23,670 --> 00:20:26,190
In the meantime, the chicks catch insects
194
00:20:26,225 --> 00:20:28,261
for as long as they can,
195
00:20:28,296 --> 00:20:31,022
then come running back to warm up again.
196
00:20:36,200 --> 00:20:39,617
Their mother knows it's not just
the cold that will get them.
197
00:20:51,940 --> 00:20:56,738
Arctic foxes live in tunnels in
the layer above the permafrost.
198
00:21:02,157 --> 00:21:03,917
The parents returned a few months ago
199
00:21:03,952 --> 00:21:08,439
from their winter wanderings
in snowy white coats
200
00:21:08,474 --> 00:21:11,477
to give birth and turn brown for summer.
201
00:21:21,694 --> 00:21:25,422
The cubs were born here in early May.
202
00:21:25,456 --> 00:21:28,045
Now, a few weeks later,
203
00:21:28,079 --> 00:21:30,841
they enjoy the remarkably warm days.
204
00:21:53,484 --> 00:21:56,556
They need to grow up fast.
205
00:21:56,591 --> 00:21:59,007
The cubs are already eating meat
206
00:21:59,041 --> 00:22:02,079
and seem constantly hungry.
207
00:22:02,113 --> 00:22:04,668
Ground squirrels
and nesting birds are here
208
00:22:04,702 --> 00:22:07,360
in large numbers in May and June.
209
00:22:09,673 --> 00:22:12,331
One delivery is not enough for them all.
210
00:22:17,784 --> 00:22:20,408
The others don't notice
the mother's return
211
00:22:20,442 --> 00:22:22,444
until it's almost too late.
212
00:22:43,638 --> 00:22:45,156
Oh, well.
213
00:22:45,191 --> 00:22:47,193
Dad will be back soon with more.
214
00:22:54,096 --> 00:22:56,961
It's a constant meal service during days
215
00:22:56,996 --> 00:22:58,963
that never quite seem to end.
216
00:23:03,692 --> 00:23:06,937
Nesting on the ground is dangerous,
217
00:23:06,971 --> 00:23:12,874
but there is one bird that would
fight off any fox... the jaeger.
218
00:23:12,908 --> 00:23:15,463
Jaeger means hunter in German.
219
00:23:18,638 --> 00:23:21,814
The caribou are beginning to arrive.
220
00:23:21,848 --> 00:23:27,198
They are tired, hungry,
many are about to give birth,
221
00:23:27,233 --> 00:23:30,478
and they could so easily tread
on a bird's nest.
222
00:23:34,930 --> 00:23:38,313
The jaegers are not going
to let that happen.
223
00:23:38,347 --> 00:23:41,109
They start with some gentle warnings,
224
00:23:41,143 --> 00:23:43,456
but the caribou ignore them.
225
00:23:47,633 --> 00:23:50,636
Yet the jaegers are fearless.
226
00:24:09,240 --> 00:24:12,278
The caribou mother has come
hundreds of miles,
227
00:24:12,312 --> 00:24:14,349
faced raging torrents,
228
00:24:14,383 --> 00:24:17,973
been jammed by lakes, escaped wolves,
229
00:24:18,008 --> 00:24:20,493
and now there's a determined parent bird
230
00:24:20,528 --> 00:24:22,599
that doesn't want her here at all.
231
00:24:31,815 --> 00:24:35,819
The caribou respond to
the swooping bird ballet
232
00:24:35,853 --> 00:24:38,235
with strange dance moves of their own.
233
00:25:13,408 --> 00:25:15,514
As more of the herd arrives,
234
00:25:15,548 --> 00:25:19,138
the jaegers battle tirelessly
to keep their eggs safe.
235
00:25:21,416 --> 00:25:25,662
For the birds, and for all life
here, there's little rest.
236
00:25:28,181 --> 00:25:30,390
Even the sun keeps going,
237
00:25:30,425 --> 00:25:34,291
skimming above the horizon
for most of June.
238
00:25:44,404 --> 00:25:47,442
This midnight sun warms the caribou
239
00:25:47,476 --> 00:25:50,825
as they all finally reach
their destination.
240
00:25:59,765 --> 00:26:02,250
These are their calving grounds,
241
00:26:02,284 --> 00:26:06,047
in the heart of the Arctic
National Wildlife Refuge.
242
00:26:11,431 --> 00:26:15,884
She must arrive precisely,
so that she's in the right place
243
00:26:15,919 --> 00:26:18,611
when, a week to 10 days
after the snow melts,
244
00:26:18,646 --> 00:26:22,235
the sedges and grasses
are at their most nutritious.
245
00:26:24,859 --> 00:26:27,758
Somewhere is a mother giving birth...
246
00:26:27,793 --> 00:26:35,214
one new calf among 160,000,
anonymous to all but each other.
247
00:26:35,248 --> 00:26:39,390
Almost all the mothers
give birth within a few days.
248
00:26:50,022 --> 00:26:53,853
The calf doubles in size in two weeks.
249
00:26:53,888 --> 00:26:57,823
The first green flush of sedges
is briefly high in protein
250
00:26:57,857 --> 00:27:01,067
and sugars and coincides within a few days
251
00:27:01,102 --> 00:27:04,519
of when the calf needs most milk.
252
00:27:04,553 --> 00:27:08,005
A week or so later, the grass
will become coarser,
253
00:27:08,040 --> 00:27:11,112
bitter, and indigestible.
254
00:27:18,671 --> 00:27:20,846
The caribou slowly spread out,
255
00:27:20,880 --> 00:27:25,367
surfing a wave of melting snow
and growing grass.
256
00:27:34,480 --> 00:27:36,758
The successful flood of energy
257
00:27:36,793 --> 00:27:39,968
transforms the character of the caribou.
258
00:27:45,353 --> 00:27:48,528
The first people here feel part of it.
259
00:27:48,563 --> 00:27:52,981
Humans and caribou were created
as one, they believe,
260
00:27:53,016 --> 00:27:57,952
and each still contains
a piece of each other's heart.
261
00:27:57,986 --> 00:28:01,093
To the Gwich'in, this is the sacred place
262
00:28:01,127 --> 00:28:03,612
where life begins.
263
00:28:21,009 --> 00:28:26,912
It's late June, and paradise
suddenly closes in.
264
00:28:26,946 --> 00:28:30,639
A plague of mosquitoes emerges.
265
00:28:32,365 --> 00:28:36,059
Each one may take just a drop of blood,
266
00:28:36,093 --> 00:28:40,063
but the warmer summers favor the insects.
267
00:28:40,097 --> 00:28:43,273
They emerge earlier and breed faster.
268
00:28:53,145 --> 00:28:55,388
The mosquitoes take so much blood
269
00:28:55,423 --> 00:28:58,391
and distress the caribou mothers so much
270
00:28:58,426 --> 00:29:00,773
that the herd spends
the rest of the summer
271
00:29:00,808 --> 00:29:02,775
attempting to avoid them
272
00:29:02,810 --> 00:29:06,020
by searching for somewhere cooler.
273
00:29:06,054 --> 00:29:09,437
Life becomes a daily
balancing act of finding
274
00:29:09,471 --> 00:29:11,473
food for yourself
275
00:29:11,508 --> 00:29:15,823
and not being food for mosquitoes.
276
00:29:15,857 --> 00:29:19,240
The consequences of the hotter
summers may be subtle
277
00:29:19,274 --> 00:29:22,001
and complex for the caribou,
278
00:29:22,036 --> 00:29:27,489
but the effects to the north
are much more obvious.
279
00:29:27,524 --> 00:29:30,665
Over the last 40 years,
the decline of sea ice
280
00:29:30,699 --> 00:29:32,356
in the Beaufort Sea
281
00:29:32,391 --> 00:29:35,670
is one of the most
dramatic changes anywhere.
282
00:29:42,884 --> 00:29:47,337
One of the animals affected most
is the polar bear.
283
00:29:47,371 --> 00:29:49,166
During the last ice age,
284
00:29:49,201 --> 00:29:54,413
they would probably spend
all year on the frozen sea.
285
00:29:54,447 --> 00:29:57,830
Since the ice age ended,
polar bears hunted seals
286
00:29:57,865 --> 00:30:00,902
on the Arctic ice in winter and spring,
287
00:30:00,937 --> 00:30:03,629
and in late summer, rested on land,
288
00:30:03,663 --> 00:30:06,770
snoozing and living off their fat.
289
00:30:14,502 --> 00:30:18,575
Nowadays the ice on
the Beaufort Sea is erratic.
290
00:30:18,609 --> 00:30:23,822
It melts faster, and the bears
arrive early and thinner.
291
00:30:37,766 --> 00:30:42,806
By July, they are hunting
for food along the shore.
292
00:30:42,841 --> 00:30:45,913
They're not a huge threat
to the caribou herd.
293
00:30:45,947 --> 00:30:49,468
They are lumbering on land,
and easily overheat.
294
00:30:59,547 --> 00:31:01,929
Years are more variable now,
295
00:31:01,963 --> 00:31:05,864
and polar bears are showing
unexpected flexibility.
296
00:31:05,898 --> 00:31:08,004
They search for smaller prey
297
00:31:08,038 --> 00:31:10,834
and scavenge or fight over scraps.
298
00:31:14,251 --> 00:31:16,909
The Arctic Refuge is a safe home,
299
00:31:16,944 --> 00:31:20,844
but there is no refuge
from the outside world.
300
00:31:20,879 --> 00:31:22,881
It's too hot for them.
301
00:31:22,915 --> 00:31:26,815
The July record here is now
85 degrees Fahrenheit.
302
00:31:30,302 --> 00:31:32,787
It's often hardest for a mother.
303
00:31:41,071 --> 00:31:45,041
Polar bear cubs are born in midwinter.
304
00:31:45,075 --> 00:31:49,183
This coast is one of the most
important onshore denning areas
305
00:31:49,217 --> 00:31:50,770
in North America.
306
00:31:56,466 --> 00:31:59,400
These cubs are almost two years old
307
00:31:59,434 --> 00:32:01,333
but still need their mother's milk.
308
00:32:20,490 --> 00:32:25,081
Polar bears have declined
in the southern Beaufort Sea.
309
00:32:25,115 --> 00:32:28,877
There are about half of how many
were here 35 years ago.
310
00:32:34,780 --> 00:32:37,472
These are desperate times.
311
00:32:44,238 --> 00:32:49,001
North Alaska has the largest
oil field in America.
312
00:32:59,529 --> 00:33:02,463
The base at Prudhoe Bay is next to
313
00:33:02,497 --> 00:33:05,638
the Arctic National Wildlife Refuge.
314
00:33:05,673 --> 00:33:07,330
It's a stark reminder
315
00:33:07,364 --> 00:33:10,057
of the cause of the changing seasons.
316
00:33:22,276 --> 00:33:25,037
Pipelines extend south
317
00:33:25,072 --> 00:33:28,661
and cross several caribou
migration routes.
318
00:33:37,256 --> 00:33:40,466
The polar bears search for food
across land
319
00:33:40,501 --> 00:33:43,745
now scarred by oil exploration.
320
00:34:02,419 --> 00:34:06,078
For the caribou, the green surge is over,
321
00:34:06,113 --> 00:34:07,942
and they are eating willow shrub
322
00:34:07,976 --> 00:34:12,947
and searching for anywhere
cooler and mosquito free.
323
00:34:12,981 --> 00:34:16,226
For some, that means the coast.
324
00:34:16,261 --> 00:34:20,506
Others head south into the
foothills of the Brooks Range.
325
00:34:28,376 --> 00:34:33,209
After enduring the heat of July,
by late August, it's cooler.
326
00:34:41,113 --> 00:34:45,359
A mother and calf turn south,
with the protection of the herd.
327
00:34:48,327 --> 00:34:52,814
Waiting for them is a grizzly.
328
00:34:52,849 --> 00:34:55,541
Grizzlies and caribou meet each year.
329
00:34:58,303 --> 00:35:02,030
The herd is named after the
Porcupine River they must cross.
330
00:35:10,867 --> 00:35:15,182
The bear's journey here
is equally hazardous.
331
00:35:15,216 --> 00:35:19,531
In summer, grizzlies hunt
all the way to the Arctic Ocean.
332
00:35:51,218 --> 00:35:53,530
The Porcupine caribou herd
333
00:35:53,565 --> 00:35:56,119
is heading south into the Brooks Range.
334
00:36:04,748 --> 00:36:08,304
Away from the water,
the caribou start to relax.
335
00:36:12,618 --> 00:36:14,206
It's a mistake.
336
00:36:27,219 --> 00:36:31,119
Caribou may be faster than bears
on the open plain,
337
00:36:31,154 --> 00:36:33,950
but they must also rest the calves.
338
00:36:39,921 --> 00:36:43,615
Grizzlies and polar bears
are almost the same species
339
00:36:43,649 --> 00:36:46,997
and increasingly overlap and interbreed,
340
00:36:47,032 --> 00:36:50,449
but grizzlies are a more
serious threat to the herd.
341
00:36:52,831 --> 00:36:56,524
The bear has learned
to chase off the mothers
342
00:36:56,559 --> 00:36:59,872
and then search for calves
hiding in the scrub.
343
00:37:15,302 --> 00:37:16,889
He's found two.
344
00:37:19,375 --> 00:37:22,861
In a moment of indecision...
345
00:37:22,895 --> 00:37:24,311
he loses both.
346
00:37:28,867 --> 00:37:32,215
The calf's mother gallops to his side.
347
00:37:32,250 --> 00:37:36,012
It's a huge victory
after so much hardship.
348
00:37:43,502 --> 00:37:45,055
Though not for the bear.
349
00:37:53,754 --> 00:37:58,103
The journey south crosses
the Brooks Range in fall.
350
00:37:58,137 --> 00:38:01,762
In spring, this route is blocked by snow,
351
00:38:01,796 --> 00:38:04,903
but now they can return
straight over the mountains.
352
00:38:33,000 --> 00:38:37,625
For the calf, this is his
first taste of the wider world,
353
00:38:37,660 --> 00:38:41,871
with some new characters...
Dall sheep.
354
00:38:49,672 --> 00:38:54,159
They are cousins of bighorns,
little bighorns,
355
00:38:54,193 --> 00:38:56,126
and mountain specialists.
356
00:38:59,958 --> 00:39:02,478
Like musk ox, they don't migrate,
357
00:39:02,512 --> 00:39:05,515
but they do move around
the mountains looking for grass
358
00:39:05,550 --> 00:39:09,105
and shrubs between the rocks.
359
00:39:09,139 --> 00:39:13,351
The ewes give birth to a single
lamb in late May.
360
00:39:13,385 --> 00:39:17,665
By September, they are all
enjoying the last of the summer.
361
00:39:34,786 --> 00:39:40,930
The mothers gather in flocks
and watch for wolves and eagles.
362
00:39:40,964 --> 00:39:43,415
This is the migration route south,
363
00:39:43,450 --> 00:39:46,004
familiar to more than just caribou.
364
00:40:07,474 --> 00:40:09,476
The fledged golden eagle
365
00:40:09,510 --> 00:40:14,066
has been shadowing the caribou herd south.
366
00:40:14,101 --> 00:40:16,068
As the herd turns east,
367
00:40:16,103 --> 00:40:19,382
the caribou face the mountains' wolves.
368
00:40:24,594 --> 00:40:28,564
In a small valley, the herd slows to rest.
369
00:40:33,327 --> 00:40:36,330
A lone female plans her hunt.
370
00:40:42,509 --> 00:40:44,511
She doesn't try to hide.
371
00:40:44,545 --> 00:40:47,168
The mountains are on her side now.
372
00:41:10,571 --> 00:41:13,643
A calf becomes separated.
373
00:41:31,040 --> 00:41:32,455
To its mother,
374
00:41:32,490 --> 00:41:37,460
almost home, the trek has
lost its meaning, its purpose.
375
00:41:45,572 --> 00:41:51,543
The snow geese arrive here from
the northernmost Arctic islands.
376
00:41:51,578 --> 00:41:55,685
This is an important stopover
on their way back to California,
377
00:41:55,720 --> 00:41:58,308
Texas, and Mexico.
378
00:42:03,175 --> 00:42:07,697
Snow geese numbers have grown
over the last 20 years.
379
00:42:07,732 --> 00:42:09,837
There are now 20 million of them.
380
00:42:15,498 --> 00:42:17,845
In a world of so much decline,
381
00:42:17,880 --> 00:42:21,055
it's good to know
some species are doing well.
382
00:42:46,978 --> 00:42:51,258
The autumn storms are sweeping in.
383
00:42:51,292 --> 00:42:53,674
The weather changes very quickly.
384
00:43:05,859 --> 00:43:10,035
Ptarmigans have been caught
in their summer plumage.
385
00:43:10,070 --> 00:43:13,038
They'll turn white to
an out-of-date schedule.
386
00:43:17,318 --> 00:43:20,011
As long as the snow isn't too deep,
387
00:43:20,045 --> 00:43:23,186
they can feed on willow buds and birch.
388
00:43:30,297 --> 00:43:33,162
Ptarmigans are here all year.
389
00:43:33,196 --> 00:43:37,476
That makes them a reliable
target for a red fox.
390
00:43:53,492 --> 00:43:56,841
The many eyes of a flock
391
00:43:56,875 --> 00:44:00,154
and their sharp calls
protect them for now.
392
00:44:02,640 --> 00:44:05,228
Red foxes are thriving in the Arctic
393
00:44:05,263 --> 00:44:09,577
and out-compete Arctic foxes
if the weather is milder.
394
00:44:25,732 --> 00:44:28,838
By October, the rivers are frozen
395
00:44:28,873 --> 00:44:30,598
and are buried under snow.
396
00:44:38,123 --> 00:44:41,713
The musk ox have to dig
for vegetation again.
397
00:44:48,547 --> 00:44:52,448
The male musk ox have other concerns.
398
00:44:52,482 --> 00:44:54,174
Before winter arrives,
399
00:44:54,208 --> 00:44:57,384
they must sort out mating rights
to the harem.
400
00:44:57,418 --> 00:44:59,593
The rut started in August
401
00:44:59,627 --> 00:45:02,251
and a clear victor has yet to emerge.
402
00:45:54,372 --> 00:45:58,307
The musk ox are also related
to bighorn sheep,
403
00:45:58,341 --> 00:46:00,274
but are much bigger.
404
00:46:00,309 --> 00:46:03,105
Males weigh in at 800 pounds,
405
00:46:03,139 --> 00:46:07,765
and their closing speed
is close to 60 miles an hour.
406
00:46:07,799 --> 00:46:10,664
Their skulls are heavily reinforced
407
00:46:10,698 --> 00:46:13,391
and the brain protected by fluid.
408
00:46:26,784 --> 00:46:30,960
They back away,
but only to prepare for combat.
409
00:46:37,484 --> 00:46:40,832
On the right, the older waits,
410
00:46:40,867 --> 00:46:42,972
then charges.
411
00:46:55,571 --> 00:46:58,298
There's probably no other animal on Earth
412
00:46:58,332 --> 00:47:00,162
that could survive this battle.
413
00:47:03,579 --> 00:47:06,237
The winner will now mate with the herd.
414
00:47:12,346 --> 00:47:16,903
By October, the land is frozen solid.
415
00:47:20,182 --> 00:47:23,461
Two polar bear cubs
have survived the summer
416
00:47:23,495 --> 00:47:25,221
thanks to their mother.
417
00:47:35,335 --> 00:47:38,027
The sea won't freeze solid until November,
418
00:47:38,062 --> 00:47:43,377
but some coastal bays and river
estuaries freeze earlier.
419
00:47:43,412 --> 00:47:47,347
It's their playground while they wait.
420
00:47:50,626 --> 00:47:52,386
On warm days the surface
421
00:47:52,421 --> 00:47:55,942
starts to melt and becomes slippery
422
00:47:55,976 --> 00:47:59,324
and tides weaken the new ice.
423
00:47:59,359 --> 00:48:02,224
The surface is still fragile.
424
00:48:23,383 --> 00:48:26,938
By midwinter, they'll be
sniffing out seals
425
00:48:26,973 --> 00:48:30,252
in a freezing twilight far from land.
426
00:48:36,292 --> 00:48:40,227
This is their ice age home at last,
427
00:48:40,262 --> 00:48:44,887
a timeless scene that leaves
behind a world of change.
428
00:48:53,033 --> 00:48:57,279
Then the ice breaks, and reality returns.
429
00:49:10,637 --> 00:49:13,157
The sea melts and refreezes
430
00:49:13,191 --> 00:49:17,092
and will melt again
for two frustrating months.
431
00:49:26,618 --> 00:49:30,208
The polar bears of the southern
Beaufort Sea are doing better
432
00:49:30,243 --> 00:49:33,867
than many others around the Arctic.
433
00:49:46,293 --> 00:49:50,470
The Arctic National Wildlife
Refuge protects the dens,
434
00:49:50,504 --> 00:49:54,646
and mothers have become expert scavengers.
435
00:49:54,681 --> 00:49:59,720
Their sense of smell is probably
the best of all animals.
436
00:50:18,153 --> 00:50:20,293
And look what they've found.
437
00:50:26,506 --> 00:50:30,234
It's a bowhead whale...
what's left of it.
438
00:50:35,239 --> 00:50:38,138
With unpredictable winter ice ahead,
439
00:50:38,173 --> 00:50:42,073
this bowhead carcass is
a salvation for the family
440
00:50:42,108 --> 00:50:45,594
and for all the local polar bears.
441
00:50:45,628 --> 00:50:47,837
They will feed for weeks.
442
00:50:49,839 --> 00:50:55,466
Bowhead whales are increasing,
maybe thanks to longer summers.
443
00:50:55,500 --> 00:50:58,883
Everything is changing,
and everything is connected.
444
00:51:01,575 --> 00:51:04,233
There is regulated whale hunting here,
445
00:51:04,268 --> 00:51:06,201
and this carcass has actually been left
446
00:51:06,235 --> 00:51:08,651
on the beach for the wildlife.
447
00:51:11,033 --> 00:51:13,794
For the polar bears, it's a lifeline,
448
00:51:13,829 --> 00:51:15,313
but maybe little more.
449
00:51:17,798 --> 00:51:21,181
They are ice bears,
evolved in another world.
450
00:51:27,084 --> 00:51:31,433
Across millions of years,
the Earth has seen huge changes
451
00:51:31,467 --> 00:51:33,780
many times.
452
00:51:33,814 --> 00:51:38,785
The most recent was the end of
the Ice Age, 12,000 years ago.
453
00:51:46,206 --> 00:51:48,070
This extraordinary wilderness
454
00:51:48,105 --> 00:51:51,349
protects these Ice Age survivors...
455
00:51:51,384 --> 00:51:55,250
the polar bears, musk ox, arctic foxes,
456
00:51:55,284 --> 00:51:57,631
and the spectacular caribou,
457
00:51:57,666 --> 00:52:02,049
holding out on the top of the world.
458
00:52:02,084 --> 00:52:06,502
Now, even for them,
the ice age may, finally,
459
00:52:06,537 --> 00:52:08,366
be coming to an end.
34192
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