1
00:00:08,800 --> 00:00:10,218
Laysan.
2
00:00:10,301 --> 00:00:13,304
A remote island in the Pacific Ocean.
3
00:00:17,308 --> 00:00:20,895
Home to this Laysan albatross chick.
4
00:00:25,483 --> 00:00:29,320
He's ready to make
his maiden flight to the open ocean.
5
00:00:31,072 --> 00:00:34,075
But there can be no room for error.
6
00:00:40,707 --> 00:00:43,084
Tiger sharks.
7
00:00:44,377 --> 00:00:47,589
They've traveled a thousand kilometers
to get here,
8
00:00:48,173 --> 00:00:51,718
arriving just in time
for the fledging season.
9
00:00:57,265 --> 00:01:01,352
Leaving will be
the most dangerous journey of his life.
10
00:01:05,065 --> 00:01:09,194
But it's his neighbors,
black-footed albatross chicks,
11
00:01:09,277 --> 00:01:10,695
that go first.
12
00:01:21,748 --> 00:01:23,083
A splash landing.
13
00:01:23,958 --> 00:01:26,461
Just what the sharks are waiting for.
14
00:01:44,813 --> 00:01:46,606
Now, it's his turn.
15
00:01:51,736 --> 00:01:53,613
With the summer winds picking up,
16
00:01:53,696 --> 00:01:58,701
conditions are finally right
for him to spread his wings
17
00:01:59,410 --> 00:02:00,410
and fly.
18
00:02:12,507 --> 00:02:16,845
He's airborne
for the first time in his life.
19
00:02:20,515 --> 00:02:22,934
But when the breeze suddenly drops...
20
00:02:24,978 --> 00:02:26,771
...so too does the chick.
21
00:02:31,526 --> 00:02:32,652
Without wind,
22
00:02:33,695 --> 00:02:34,946
he's helpless.
23
00:02:44,956 --> 00:02:46,916
A very lucky escape.
24
00:03:13,109 --> 00:03:14,109
He's off!
25
00:03:14,903 --> 00:03:18,698
He may not touch land again for five years
26
00:03:19,908 --> 00:03:23,328
as he travels
hundreds of thousands of kilometers
27
00:03:23,411 --> 00:03:26,748
across the ocean searching for food.
28
00:03:50,688 --> 00:03:53,566
Our planet is solar-powered.
29
00:03:56,569 --> 00:03:59,614
The sun's rays take eight minutes
to reach us.
30
00:04:01,783 --> 00:04:06,579
But due to the Earth's tilt,
they don't strike its surface evenly.
31
00:04:09,290 --> 00:04:13,002
This solar energy
arrives in varying amounts
32
00:04:13,086 --> 00:04:17,048
at different times of the year,
depending on where it strikes.
33
00:04:18,466 --> 00:04:20,718
And in the Northern Hemisphere,
34
00:04:20,802 --> 00:04:23,763
the huge increase that comes with summer
35
00:04:23,846 --> 00:04:26,391
triggers countless journeys.
36
00:04:34,148 --> 00:04:35,858
In early July,
37
00:04:35,942 --> 00:04:39,445
the flower meadows of Europe
receive more sunlight
38
00:04:39,529 --> 00:04:42,198
than at any other time of the year.
39
00:04:46,202 --> 00:04:50,415
And that makes it
a very busy time for honeybees.
40
00:04:54,877 --> 00:04:58,923
Few animals work harder
to exploit the summer's riches.
41
00:05:02,218 --> 00:05:04,971
To make just half a kilo of honey,
42
00:05:05,054 --> 00:05:09,475
a colony of bees
must fly 90,000 kilometers
43
00:05:09,559 --> 00:05:12,186
and visit over a million flowers.
44
00:05:17,567 --> 00:05:22,864
And we have taken advantage
of their labors for thousands of years.
45
00:05:28,202 --> 00:05:30,538
In this domestic hive in Germany,
46
00:05:30,621 --> 00:05:34,917
60,000 bees are working together
as one superorganism.
47
00:05:44,010 --> 00:05:48,639
And with the larger queen
laying an egg every 30 seconds,
48
00:05:48,723 --> 00:05:52,268
it's a colony
that is now bursting at the seams.
49
00:05:55,688 --> 00:06:00,443
There could be another 40,000 bees
developing in this hive.
50
00:06:01,069 --> 00:06:04,530
And there just isn't enough room
for them all.
51
00:06:09,869 --> 00:06:13,247
The superorganism has to split.
52
00:06:25,259 --> 00:06:29,138
Those in the leaving party
gather at the entrance.
53
00:06:35,728 --> 00:06:39,649
And when they reach a critical mass,
they begin to swarm.
54
00:06:52,203 --> 00:06:54,372
They must find a new home.
55
00:06:55,540 --> 00:07:00,878
But the first stop
is just a staging post close to the hive.
56
00:07:15,601 --> 00:07:19,939
In a few minutes,
30,000 bees gather around the queen,
57
00:07:21,107 --> 00:07:23,401
who is now shielded by the swarm.
58
00:07:35,496 --> 00:07:39,208
Out in the open,
they're vulnerable to the elements.
59
00:07:43,212 --> 00:07:47,008
So the race is on
to find somewhere else to live.
60
00:07:50,261 --> 00:07:54,265
Scouts set off
looking for a suitable home.
61
00:07:55,641 --> 00:08:01,147
A tree hole that is just the right size,
height, and angle to the sun.
62
00:08:06,652 --> 00:08:08,112
This one looks possible.
63
00:08:09,322 --> 00:08:11,449
But... too shady.
64
00:08:15,119 --> 00:08:16,119
Too small.
65
00:08:20,625 --> 00:08:21,918
Already taken.
66
00:08:29,050 --> 00:08:31,177
Now, what about this one?
67
00:08:34,138 --> 00:08:35,973
It looks promising.
68
00:08:48,778 --> 00:08:51,197
Yes, this will do nicely.
69
00:08:53,699 --> 00:08:56,911
So it's back to the staging post
70
00:08:56,994 --> 00:08:59,413
to convince the rest of the colony.
71
00:09:03,334 --> 00:09:06,295
And she does that by dancing.
72
00:09:09,382 --> 00:09:12,927
The angle of her waggle dance
relative to the sun
73
00:09:13,010 --> 00:09:16,556
tells them in which direction
the hole can be found,
74
00:09:17,807 --> 00:09:21,310
while the duration lets them know
how far away it is.
75
00:09:22,228 --> 00:09:26,065
And the better the spot,
the more intense her performance.
76
00:09:29,277 --> 00:09:32,446
Others return to advertise their finds.
77
00:09:33,489 --> 00:09:38,119
But their moves
just don't cut it compared to hers.
78
00:09:42,415 --> 00:09:44,584
Interest grows around her.
79
00:09:45,835 --> 00:09:48,838
And more bees set out
to inspect the new hole.
80
00:09:51,090 --> 00:09:53,593
It's house hunting by committee.
81
00:09:59,348 --> 00:10:00,558
It seems they agree,
82
00:10:01,517 --> 00:10:05,229
and they return to spread the news
to the rest of the swarm.
83
00:10:11,193 --> 00:10:15,573
To do so,
the scouts must touch every bee in turn.
84
00:10:18,284 --> 00:10:21,162
And, incredibly, in just half an hour,
85
00:10:21,245 --> 00:10:24,874
all 30,000 of them are ready to leave.
86
00:10:43,017 --> 00:10:47,730
Upon arrival, each bee
fans a pheromone across the forest,
87
00:10:48,564 --> 00:10:51,817
helping others to find the new nest site.
88
00:10:54,362 --> 00:10:57,448
More and more arrive at the new location.
89
00:10:59,283 --> 00:11:02,828
All joining in
to spread the chemical message.
90
00:11:09,627 --> 00:11:14,423
Within a few hours,
the entire swarm has made the move.
91
00:11:20,346 --> 00:11:22,807
Bees are only able to move like this
92
00:11:22,890 --> 00:11:26,268
when the sun's energy
provides them with enough food
93
00:11:26,352 --> 00:11:29,105
to rebuild their colony from scratch.
94
00:11:30,564 --> 00:11:33,025
So for the next few weeks,
95
00:11:33,109 --> 00:11:35,736
they will need to be as busy as,
96
00:11:35,820 --> 00:11:37,405
well, a bee!
97
00:11:44,286 --> 00:11:46,956
In July, the further north you go,
98
00:11:47,039 --> 00:11:48,916
the more daylight there is.
99
00:11:50,876 --> 00:11:53,003
And, for just a brief period,
100
00:11:53,087 --> 00:11:55,256
this increase in solar power
101
00:11:55,339 --> 00:11:59,218
turns the Arctic tundra
into a rich grassland,
102
00:12:00,302 --> 00:12:03,806
attracting more than a million snow geese.
103
00:12:11,021 --> 00:12:13,649
They've traveled the length
of North America,
104
00:12:13,733 --> 00:12:16,777
a distance of 5,000 kilometers,
105
00:12:16,861 --> 00:12:19,822
and they've come here to breed.
106
00:12:24,243 --> 00:12:26,328
Arctic summers are short,
107
00:12:26,412 --> 00:12:29,039
so the geese start laying straightaway.
108
00:12:29,874 --> 00:12:32,752
The female sits tight on the nest.
109
00:12:35,337 --> 00:12:38,466
While the male
keeps an eye out for enemies.
110
00:12:42,678 --> 00:12:44,555
And he doesn't have long to wait.
111
00:12:48,851 --> 00:12:51,771
Arctic foxes live here the year-round,
112
00:12:51,854 --> 00:12:54,982
and they eagerly await
the return of the geese.
113
00:13:02,865 --> 00:13:07,620
The fox's survival
depends on a steady supply of eggs.
114
00:13:24,011 --> 00:13:27,890
But snow geese only lay one clutch a year.
115
00:13:30,976 --> 00:13:33,103
And they defend it with their lives.
116
00:13:38,275 --> 00:13:43,697
Nonetheless, a single fox may steal
over a thousand eggs in a season.
117
00:13:59,630 --> 00:14:01,298
Despite these losses...
118
00:14:03,801 --> 00:14:06,220
...plenty of eggs do hatch.
119
00:14:13,143 --> 00:14:16,981
It may be the height of summer,
but it's still the Arctic.
120
00:14:17,523 --> 00:14:21,110
So the goslings stay with Mother
to keep warm.
121
00:14:29,827 --> 00:14:33,330
But there's only so much room
under one wing.
122
00:14:41,630 --> 00:14:44,300
Still, it's better to keep out of the way
123
00:14:45,175 --> 00:14:48,512
when the tundra's larger residents
pass through.
124
00:14:50,848 --> 00:14:53,517
Caribou themselves pose little risk.
125
00:14:54,393 --> 00:14:56,478
But they do bring problems.
126
00:14:58,647 --> 00:15:02,776
Grizzly bears follow them
in the hope of an easy meal.
127
00:15:10,326 --> 00:15:14,496
And their presence
causes a stir within the colony.
128
00:15:28,761 --> 00:15:32,139
Any chick in its path is hoovered up.
129
00:15:41,273 --> 00:15:43,275
With things getting dangerous,
130
00:15:43,359 --> 00:15:47,071
it's time for these chicks
to start their life on the move.
131
00:15:54,036 --> 00:15:57,331
The family heads
for the safety of the water.
132
00:16:02,920 --> 00:16:07,257
In just eight weeks,
when the sun's power starts to wane here,
133
00:16:09,093 --> 00:16:12,179
the goslings will make
their first flight south,
134
00:16:13,514 --> 00:16:16,141
all the way to the Gulf of Mexico.
135
00:16:28,779 --> 00:16:32,783
Not all animals migrate
as the seasons change.
136
00:16:34,994 --> 00:16:39,123
Lions control the same territory
year in, year out.
137
00:16:40,249 --> 00:16:46,463
So this pride in East Africa's Serengeti
relies on prey coming to them.
138
00:16:48,132 --> 00:16:51,385
Right now,
it's the height of the dry season,
139
00:16:51,468 --> 00:16:54,388
and the long grass plains
where these lions live
140
00:16:54,471 --> 00:16:56,223
are relatively empty.
141
00:16:59,059 --> 00:17:01,687
But things are about to change.
142
00:17:03,939 --> 00:17:08,318
Heading towards them
are hundreds of thousands of wildebeest.
143
00:17:14,658 --> 00:17:19,747
Together, they make up the biggest
terrestrial migration on Earth.
144
00:17:24,960 --> 00:17:30,507
The herd eats its way
through nearly 5,000 tons of grass a day,
145
00:17:31,216 --> 00:17:34,011
which means they have to keep on the move.
146
00:17:36,055 --> 00:17:39,099
Something the lions have been counting on.
147
00:17:44,980 --> 00:17:48,817
The long dry grass
is of little nutritional value,
148
00:17:49,526 --> 00:17:51,987
but the herd must pass through it.
149
00:17:54,490 --> 00:17:56,366
And the lions know that.
150
00:18:01,622 --> 00:18:06,251
The grass provides
a very effective cloak of invisibility.
151
00:18:21,600 --> 00:18:23,936
To prevent her scent being detected,
152
00:18:24,645 --> 00:18:27,815
the lioness approaches from downwind.
153
00:18:33,821 --> 00:18:35,155
Stalking.
154
00:18:37,658 --> 00:18:38,700
And stopping.
155
00:18:43,705 --> 00:18:45,249
Every movement
156
00:18:46,500 --> 00:18:47,500
considered.
157
00:18:48,627 --> 00:18:52,548
One careless step
could reveal her presence.
158
00:19:12,901 --> 00:19:15,154
Any disturbance in the grass
159
00:19:15,779 --> 00:19:18,740
could be a potential threat for the herd.
160
00:19:22,786 --> 00:19:24,371
That's just a guinea fowl.
161
00:19:26,582 --> 00:19:27,583
A false alarm.
162
00:19:34,464 --> 00:19:36,884
Or... perhaps not.
163
00:19:41,180 --> 00:19:43,473
She's almost perfectly placed.
164
00:19:45,809 --> 00:19:48,645
Just 20 meters from her target.
165
00:20:34,358 --> 00:20:39,029
After months with little to eat,
this is a vital meal.
166
00:20:43,784 --> 00:20:46,870
The pride will need to make the most
of the migration
167
00:20:47,454 --> 00:20:49,081
while it's passing through.
168
00:20:50,624 --> 00:20:53,919
Soon, the herds
will have left the lions' territory,
169
00:20:54,670 --> 00:20:58,757
moving north in their never-ending search
for fresh grazing.
170
00:21:10,435 --> 00:21:14,731
In August, the Northern Hemisphere
is at its warmest.
171
00:21:15,941 --> 00:21:18,568
And on Canada's Vancouver Island,
172
00:21:18,652 --> 00:21:23,198
there's one animal whose life cycle
depends on these higher temperatures.
173
00:21:26,785 --> 00:21:29,454
As day breaks over Cedar Lake,
174
00:21:29,538 --> 00:21:32,374
something is stirring in its depths.
175
00:21:39,798 --> 00:21:44,970
Tadpoles here spend their nights
hiding in deep, cool water.
176
00:21:46,722 --> 00:21:50,267
Now, with the sun up,
they set off across the lake.
177
00:21:55,022 --> 00:21:57,441
Initially, in hundreds.
178
00:21:59,526 --> 00:22:01,611
Then thousands.
179
00:22:05,365 --> 00:22:08,618
All are heading for the sunlit shallows.
180
00:22:13,290 --> 00:22:18,378
Here, the water is five degrees warmer
than in the lake's depths,
181
00:22:19,254 --> 00:22:22,549
and that will speed
their transformation into toads.
182
00:22:25,927 --> 00:22:27,387
But when night falls,
183
00:22:28,305 --> 00:22:30,974
they head back to the safety of the deep.
184
00:22:32,309 --> 00:22:34,353
Until the next morning.
185
00:22:36,605 --> 00:22:39,232
Every day they repeat the journey.
186
00:22:40,317 --> 00:22:41,151
Sun.
187
00:22:42,361 --> 00:22:43,361
Swim.
188
00:22:44,696 --> 00:22:45,697
Feed.
189
00:22:46,698 --> 00:22:47,698
Repeat.
190
00:22:57,084 --> 00:22:58,585
It seems perfect.
191
00:22:59,753 --> 00:23:04,257
Except others take advantage
of their daily routine.
192
00:23:07,511 --> 00:23:09,304
Dragonfly larvae.
193
00:23:14,351 --> 00:23:17,229
They are ambush predators
194
00:23:18,730 --> 00:23:21,233
with extendable jaws.
195
00:23:23,652 --> 00:23:25,862
And they have voracious appetites.
196
00:23:33,245 --> 00:23:36,665
Blind leeches patrol the muddy bottom.
197
00:23:46,299 --> 00:23:47,884
Once they catch something...
198
00:23:49,970 --> 00:23:52,305
they suck out its blood.
199
00:24:03,817 --> 00:24:05,152
Throughout the summer,
200
00:24:06,695 --> 00:24:10,031
the tadpoles continue their daily commute.
201
00:24:19,040 --> 00:24:21,418
Until, after a few weeks...
202
00:24:23,670 --> 00:24:26,590
...they start to look like tiny toads.
203
00:24:29,968 --> 00:24:34,014
By harnessing the sun's energy,
they've grown quickly.
204
00:24:36,892 --> 00:24:39,561
Now, they stop their daily routines
205
00:24:39,644 --> 00:24:42,731
and prepare for their journey
into the forest.
206
00:24:49,529 --> 00:24:50,572
Here too,
207
00:24:51,865 --> 00:24:53,325
predators await.
208
00:24:59,289 --> 00:25:02,584
Garter snakes specialize
in eating amphibians.
209
00:25:03,293 --> 00:25:06,880
Though they rarely have
as much choice as this.
210
00:25:23,188 --> 00:25:29,110
Eventually, the sheer numbers
of young toads overwhelm the snakes.
211
00:25:33,907 --> 00:25:36,409
The survivors spread out into the forest
212
00:25:36,493 --> 00:25:39,162
where they'll spend the next four years.
213
00:25:46,419 --> 00:25:51,883
Until it's time for them
to head back to the lake to breed.
214
00:26:04,854 --> 00:26:10,110
By midsummer, there is little snow left
in America's Pacific Northwest.
215
00:26:12,445 --> 00:26:14,364
Meltwater fills the rivers,
216
00:26:14,447 --> 00:26:17,701
ready to carry travelers
who make what is perhaps
217
00:26:17,784 --> 00:26:20,620
the most extraordinary
and demanding journey
218
00:26:20,704 --> 00:26:22,455
tackled by any animal.
219
00:26:26,501 --> 00:26:27,752
Sockeye salmon.
220
00:26:28,253 --> 00:26:31,172
And they're heading upriver to breed.
221
00:26:41,725 --> 00:26:44,728
After three years
feeding in the Bering Sea,
222
00:26:44,811 --> 00:26:48,607
they find their way
across hundreds of kilometers of ocean,
223
00:26:48,690 --> 00:26:51,234
guided by the Earth's magnetic field
224
00:26:51,318 --> 00:26:55,572
and their astounding ability
to recognize the taste of the river
225
00:26:55,655 --> 00:26:57,198
in which they hatched.
226
00:26:59,534 --> 00:27:05,457
They are one of the few fish in the world
that can move from saltwater into fresh.
227
00:27:06,374 --> 00:27:08,001
And over the next month,
228
00:27:08,084 --> 00:27:11,254
they will travel 200 kilometers upstream,
229
00:27:11,338 --> 00:27:15,884
past Lake Iliamna,
to their spawning pools just beyond.
230
00:27:19,763 --> 00:27:24,225
It's the last journey
these salmon will ever make.
231
00:27:29,606 --> 00:27:32,525
As they enter the river, they stop eating...
232
00:27:35,362 --> 00:27:38,782
putting all their efforts
into battling the current.
233
00:27:46,539 --> 00:27:50,669
Swift rapids and high waterfalls
do not stop them.
234
00:28:01,805 --> 00:28:03,723
Four weeks into their journey,
235
00:28:03,807 --> 00:28:06,685
their bodies begin to change.
236
00:28:08,770 --> 00:28:11,648
Flashes of red appear in their flanks.
237
00:28:15,610 --> 00:28:17,904
These are their breeding colors.
238
00:28:18,613 --> 00:28:21,741
And the redder the fish,
the fitter they are.
239
00:28:24,035 --> 00:28:27,288
A few more weeks,
and they're barely recognizable.
240
00:28:28,915 --> 00:28:32,669
The jaws of the males
have become hooked beaks,
241
00:28:32,752 --> 00:28:35,213
which they will use to fight for a mate.
242
00:28:37,424 --> 00:28:42,387
But their spawning pools
are still nearly 100 kilometers away.
243
00:28:43,805 --> 00:28:45,223
And just upriver,
244
00:28:45,890 --> 00:28:49,269
there are predators
ready to intercept them.
245
00:29:00,572 --> 00:29:03,825
Bears depend on the annual salmon run
246
00:29:05,326 --> 00:29:07,954
to fatten up for the winter ahead.
247
00:29:15,754 --> 00:29:19,758
And right now, they're very, very hungry.
248
00:29:41,112 --> 00:29:42,697
During the migration,
249
00:29:42,781 --> 00:29:46,493
an adult bear can eat 40 salmon a day.
250
00:29:50,747 --> 00:29:52,916
The salmon are quick and agile.
251
00:30:07,931 --> 00:30:10,475
But, as the water gets shallower...
252
00:30:12,769 --> 00:30:16,356
the advantage swings
in favor of the bears.
253
00:30:34,749 --> 00:30:36,793
Several kilometers upstream,
254
00:30:36,876 --> 00:30:40,505
the fish finally reach Lake Iliamna.
255
00:30:42,257 --> 00:30:45,927
One of the last pristine waterways
in America.
256
00:30:50,431 --> 00:30:53,393
Their spawning pools lie just upstream.
257
00:30:53,977 --> 00:30:55,812
But, for now, the sockeye linger
258
00:30:55,895 --> 00:30:59,065
while the females' eggs
complete their development.
259
00:31:07,699 --> 00:31:10,410
But their troubles are not yet over.
260
00:31:15,248 --> 00:31:20,670
These waters are the home
of the only freshwater seals in America.
261
00:31:35,476 --> 00:31:38,313
The salmon haven't eaten in eight weeks,
262
00:31:39,731 --> 00:31:42,150
but they can still outswim
these predators.
263
00:31:57,332 --> 00:31:59,918
The seals switch strategy
264
00:32:00,001 --> 00:32:03,254
and start to hide in plain sight.
265
00:32:08,551 --> 00:32:10,762
In a rarely seen behavior,
266
00:32:11,471 --> 00:32:14,682
they wait for the salmon to come to them.
267
00:32:17,894 --> 00:32:21,773
Surprisingly, they ignore the males
right in front of them.
268
00:32:27,028 --> 00:32:28,696
And go for the females,
269
00:32:29,781 --> 00:32:32,492
who are laden with calorie-rich eggs.
270
00:32:49,217 --> 00:32:51,594
But for every salmon that's taken,
271
00:32:53,304 --> 00:32:55,056
thousands get through.
272
00:33:04,273 --> 00:33:07,485
Battered and bruised
from their long journey,
273
00:33:07,568 --> 00:33:11,322
they have, at last,
reached their spawning pools.
274
00:33:13,658 --> 00:33:16,786
Once here, males and females pair up
275
00:33:16,869 --> 00:33:20,373
and, together,
fight for the best nest sites.
276
00:33:35,430 --> 00:33:37,932
Finally, they mate.
277
00:33:46,065 --> 00:33:49,569
It's the only time they will ever do so.
278
00:33:58,953 --> 00:34:03,624
They've given everything
to complete this epic migration.
279
00:34:05,835 --> 00:34:08,713
Their lives are over.
280
00:34:12,216 --> 00:34:16,471
The nutrients from their decaying bodies
fertilize the water.
281
00:34:18,181 --> 00:34:21,768
A sacrifice that ensures
the next generation
282
00:34:21,851 --> 00:34:24,437
will have the very best start in life.
283
00:34:33,654 --> 00:34:36,240
August in the High Arctic.
284
00:34:37,450 --> 00:34:40,119
After three months of continuous daylight,
285
00:34:40,203 --> 00:34:42,789
little is left of the sea ice.
286
00:34:48,878 --> 00:34:53,049
And that makes life
very hard for this ice bear
287
00:34:54,217 --> 00:34:56,719
and her eight-month-old cubs.
288
00:35:03,226 --> 00:35:07,855
Three months ago, they were hunting
blubber-rich seals out on the ice.
289
00:35:09,482 --> 00:35:13,194
Now they're forced to swim continuously
for days on end
290
00:35:14,362 --> 00:35:17,073
in search of whatever food they can find.
291
00:35:27,542 --> 00:35:32,213
Polar bears use five times more energy
when swimming than walking.
292
00:35:34,507 --> 00:35:39,178
And that is beginning to take its toll
on her smallest cub.
293
00:36:10,626 --> 00:36:12,795
He's finding it hard to keep up.
294
00:36:15,381 --> 00:36:18,467
But his mother
is too hungry to wait for long.
295
00:36:18,551 --> 00:36:21,554
She can smell food
somewhere on this island.
296
00:36:26,309 --> 00:36:30,938
And the dive-bombing gulls
are a sign that she's close.
297
00:36:33,941 --> 00:36:36,861
For the largest land carnivore on Earth,
298
00:36:36,944 --> 00:36:38,779
these chicks are not much of a meal.
299
00:36:40,072 --> 00:36:43,993
Though they would be a much-needed boost
for the cubs...
300
00:36:48,623 --> 00:36:51,959
if they can get down to it
before it's gone.
301
00:36:55,463 --> 00:36:59,091
The weaker cub is not very sure-footed.
302
00:37:12,855 --> 00:37:16,484
By the time he's caught up, it's too late.
303
00:37:25,534 --> 00:37:27,286
With food so scarce,
304
00:37:28,329 --> 00:37:30,623
there is no time for rest.
305
00:37:34,710 --> 00:37:38,381
The climb back up should be easy.
306
00:37:41,968 --> 00:37:46,013
Certainly, his sibling seems to take it
in his stride.
307
00:37:48,307 --> 00:37:53,479
But after that long swim
the weaker cub has little energy left.
308
00:37:57,942 --> 00:38:00,778
Unable to follow, he panics
309
00:38:00,861 --> 00:38:03,114
and heads in the wrong direction.
310
00:38:04,699 --> 00:38:09,412
A slip here would mean
a 15-meter fall onto the rocks below.
311
00:38:18,129 --> 00:38:21,215
His mother takes no notice
of his problems,
312
00:38:21,299 --> 00:38:23,676
so desperate is she for another meal.
313
00:38:33,102 --> 00:38:36,772
His survival depends
on staying close to his mother.
314
00:38:39,317 --> 00:38:43,779
If he can't keep up,
she will be forced to abandon him.
315
00:39:13,601 --> 00:39:14,643
He's made it.
316
00:39:18,647 --> 00:39:22,485
Only to find
that he must still keep going.
317
00:39:27,656 --> 00:39:31,577
It's a journey
this young cub may not survive.
318
00:39:36,540 --> 00:39:40,211
With summer sea ice
melting earlier than we've ever known,
319
00:39:40,294 --> 00:39:44,131
polar bears are having to spend
more of their year swimming.
320
00:39:47,176 --> 00:39:50,388
For animals used to traveling across ice,
321
00:39:50,471 --> 00:39:53,766
these changes may well prove
to be too great.
322
00:40:06,821 --> 00:40:09,782
Six thousand kilometers
south of the Arctic,
323
00:40:09,865 --> 00:40:15,204
the summer sun is also heating
the shallow waters of the Persian Gulf,
324
00:40:15,287 --> 00:40:19,041
making the sea here
the hottest on the planet.
325
00:40:24,463 --> 00:40:28,175
And that attracts
the ocean's biggest fish.
326
00:40:31,095 --> 00:40:32,888
The whale shark.
327
00:40:39,395 --> 00:40:42,064
After a journey
of thousands of kilometers,
328
00:40:42,148 --> 00:40:47,111
it's arrived in time for one of
the best feeding events of its year...
329
00:40:49,530 --> 00:40:52,324
and is heading to a particular spot.
330
00:40:56,412 --> 00:41:00,082
The waters of the Al Shaheen Oil Fields.
331
00:41:04,545 --> 00:41:07,256
The platforms act as reefs,
332
00:41:07,339 --> 00:41:10,426
providing a home for hundreds of species.
333
00:41:12,803 --> 00:41:17,516
No vessels are allowed
within half a kilometer of each rig,
334
00:41:18,767 --> 00:41:23,731
so creating marine sanctuaries
where fish can spawn in safety.
335
00:41:27,485 --> 00:41:29,069
Tuna are among them.
336
00:41:29,987 --> 00:41:35,201
They can only breed when the water
is 25 degrees Celsius or more.
337
00:41:38,913 --> 00:41:42,625
So, in summer,
when the gulf is at its hottest,
338
00:41:42,708 --> 00:41:48,047
they gather together
and release hundreds of millions of eggs.
339
00:41:51,592 --> 00:41:54,970
The water's surface
becomes thick with spawn.
340
00:41:56,847 --> 00:42:01,018
And that is what the whale shark
has crossed oceans for.
341
00:42:14,198 --> 00:42:17,868
Taking in water
through its meter-wide mouth,
342
00:42:17,952 --> 00:42:19,787
it collects the eggs.
343
00:42:29,213 --> 00:42:32,341
More sharks arrive to join the feast.
344
00:42:36,053 --> 00:42:39,306
But this is the hottest sea on Earth.
345
00:42:41,642 --> 00:42:45,062
And after feeding
for a few hours each morning,
346
00:42:45,145 --> 00:42:48,899
the whale sharks
will have to return to the cooler depths.
347
00:42:56,907 --> 00:42:58,993
At the height of the spawning season,
348
00:42:59,076 --> 00:43:02,329
there may be over 100
per square kilometer.
349
00:43:05,791 --> 00:43:09,587
It's one of the largest gatherings
of whale sharks on the planet.
350
00:43:11,380 --> 00:43:17,428
And all the more remarkable that it was
only recorded for the first time in 2010.
351
00:43:31,108 --> 00:43:33,068
Back in the Serengeti,
352
00:43:33,152 --> 00:43:37,114
a million wildebeest and zebra
are still on the move,
353
00:43:37,197 --> 00:43:41,076
following the sun and rain
in search of fresh grazing.
354
00:43:45,831 --> 00:43:47,833
And in amongst the throng...
355
00:43:49,335 --> 00:43:50,544
...new life.
356
00:43:54,214 --> 00:43:59,053
This zebra foal and his family
travel amongst the wildebeest for safety.
357
00:44:02,514 --> 00:44:05,059
He is just four weeks old,
358
00:44:05,142 --> 00:44:08,729
and keeping pace with the herd
is a daily struggle.
359
00:44:13,192 --> 00:44:16,570
Yet his biggest hurdle lies just ahead.
360
00:44:19,031 --> 00:44:20,366
The Mara River.
361
00:44:25,037 --> 00:44:26,747
Its fast-flowing waters
362
00:44:26,830 --> 00:44:30,584
claim the lives of 6,000 animals a year.
363
00:44:33,212 --> 00:44:38,884
Crossing it will be a major trial
for a foal that has never swum before.
364
00:44:42,179 --> 00:44:44,682
The herd nears the river's edge.
365
00:44:46,934 --> 00:44:49,561
None wants to be the first to cross.
366
00:44:51,146 --> 00:44:52,731
But as numbers increase,
367
00:44:53,357 --> 00:44:55,734
pressure mounts on those at the front.
368
00:44:59,196 --> 00:45:00,572
Once one commits,
369
00:45:00,656 --> 00:45:02,408
the floodgates open.
370
00:45:18,507 --> 00:45:21,135
But the foal and his family wait.
371
00:45:29,643 --> 00:45:32,938
Many wildebeest drown in the crush.
372
00:45:54,668 --> 00:45:56,962
Still, the zebra hold back.
373
00:46:00,132 --> 00:46:01,633
And with good reason.
374
00:46:03,594 --> 00:46:06,305
Five-meter-long Nile crocodiles.
375
00:46:07,222 --> 00:46:09,391
Amongst the biggest in Africa.
376
00:46:16,607 --> 00:46:21,487
These giant reptiles may not have eaten
since this time last year.
377
00:46:29,620 --> 00:46:32,331
With so many targets from which to choose,
378
00:46:32,414 --> 00:46:34,625
they can afford to take their time.
379
00:46:55,771 --> 00:46:57,397
Soon, perhaps,
380
00:46:57,481 --> 00:47:00,400
the crocodiles will have taken their fill.
381
00:47:07,074 --> 00:47:09,117
No such luck.
382
00:47:14,164 --> 00:47:16,583
The zebra can wait no longer.
383
00:47:16,667 --> 00:47:19,169
They must stay with the herd.
384
00:47:20,212 --> 00:47:25,509
So, the young foal
must now swim for his life.