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[narrator] Earth
is a restless place.
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00:00:15,058 --> 00:00:16,320
[thunder crashing]
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00:00:18,496 --> 00:00:21,890
Its seasons driven
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00:00:21,891 --> 00:00:23,011
by the orbit around our sun.
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00:00:25,373 --> 00:00:27,417
An epic journey
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00:00:27,418 --> 00:00:28,636
that sets the rhythms
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00:00:28,637 --> 00:00:30,030
of all life.
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00:00:33,120 --> 00:00:34,642
Humans honour this passage
through ritual and celebration.
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00:00:34,643 --> 00:00:38,125
[fireworks crackling]
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00:00:41,954 --> 00:00:45,393
Nature marks the cycle
with its own patterns.
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00:00:50,615 --> 00:00:55,706
Over the course of a year,
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00:00:55,707 --> 00:00:57,667
the planet's most spectacular
events of migration,
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00:01:00,799 --> 00:01:02,366
rebirth
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00:01:03,411 --> 00:01:04,455
and transformation unfold.
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00:01:06,414 --> 00:01:09,459
[roaring]
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00:01:09,460 --> 00:01:10,722
Moment by moment,
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00:01:12,681 --> 00:01:13,681
[roaring]
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00:01:13,682 --> 00:01:15,075
month by month,
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00:01:17,555 --> 00:01:19,209
throughout a wild year on Earth.
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00:01:38,663 --> 00:01:43,319
Early July sees the sun's
abundant energy
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00:01:43,320 --> 00:01:45,627
focused
on the northern hemisphere.
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00:01:53,200 --> 00:01:58,160
Intense light and heat
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00:01:58,161 --> 00:01:59,379
act as catalysts
on the ice caps of the Arctic,
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00:01:59,380 --> 00:02:02,122
as they start to shift and thaw.
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00:02:12,523 --> 00:02:17,440
Water carves vertical rivers
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00:02:17,441 --> 00:02:19,001
that plummet deep
into the frozen abyss.
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00:02:22,446 --> 00:02:25,057
[water rushing]
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00:02:33,501 --> 00:02:36,895
The icy landscape accelerates
its flow towards the sea.
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00:02:42,597 --> 00:02:46,208
Huge fault lines appear.
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00:02:46,209 --> 00:02:48,298
Something has got to give.
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00:03:04,749 --> 00:03:08,275
[crashing]
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00:03:15,934 --> 00:03:19,460
This is iceberg calving season.
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00:03:27,468 --> 00:03:32,559
The ice sheets in Greenland
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00:03:32,560 --> 00:03:33,798
shed billions of tons of ice
a year during the melt.
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00:03:33,822 --> 00:03:39,174
In recent years,
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00:03:39,175 --> 00:03:41,456
the melt season has started
earlier and is lasting longer.
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00:03:45,573 --> 00:03:47,791
Now, more ice melts
in the summer
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00:03:47,792 --> 00:03:49,112
than gets replenished
over winter.
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00:03:52,275 --> 00:03:54,155
The overall loss of ice
has become catastrophic.
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00:03:55,496 --> 00:03:59,847
30 years ago,
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00:03:59,848 --> 00:04:01,805
Greenland's ice sheets
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00:04:01,806 --> 00:04:03,606
would melt 25 billion tons
of ice each summer.
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00:04:05,593 --> 00:04:08,943
Last season,
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00:04:08,944 --> 00:04:11,104
more than 600 billion tons
of ice was lost in the melt.
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00:04:14,602 --> 00:04:15,802
The climate is truly changing.
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00:04:25,830 --> 00:04:31,748
The glacial melt
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00:04:31,749 --> 00:04:34,949
adds to some of the world's most
nutrient-rich waters in the
Svalbard archipelago.
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00:04:36,667 --> 00:04:38,060
[squawking]
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00:04:41,585 --> 00:04:46,720
By July,
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00:04:46,721 --> 00:04:47,938
millions of seabirds
have migrated from the south
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00:04:47,939 --> 00:04:49,699
to feed around the clock
in 24-hour daylight.
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00:05:03,390 --> 00:05:06,828
It's an ideal place for birds
to breed and raise their young.
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00:05:12,790 --> 00:05:15,879
Auks have chosen to nest
in the scree slopes
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00:05:15,880 --> 00:05:17,447
at the base
of the island's cliffs.
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00:05:23,235 --> 00:05:27,630
For Arctic foxes that have spent
the winter scavenging,
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00:05:27,631 --> 00:05:31,373
it's a perfect time to hunt.
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00:05:31,374 --> 00:05:33,028
[ominous music playing]
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00:05:37,772 --> 00:05:42,819
The eggs are well protected,
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00:05:42,820 --> 00:05:44,620
but the adult birds
still have to venture out.
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00:05:47,782 --> 00:05:51,785
[squawking]
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00:05:51,786 --> 00:05:53,962
[dramatic music playing]
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00:06:03,450 --> 00:06:06,844
Though, attacking them head-on
rarely works.
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00:06:11,327 --> 00:06:12,927
The auks are just too quick
off the mark.
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00:06:14,635 --> 00:06:17,593
What's required
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00:06:17,594 --> 00:06:18,954
is some of that famous fox
cunning.
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00:06:29,954 --> 00:06:33,480
[chirping]
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00:06:48,059 --> 00:06:51,585
And a lucky break wouldn't hurt.
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00:06:58,896 --> 00:07:02,422
A gull is also on the hunt.
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00:07:05,729 --> 00:07:06,809
[suspenseful music playing]
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00:07:17,654 --> 00:07:21,092
The threat from above distracts
the auks for a split second.
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00:07:27,055 --> 00:07:28,839
And a split second
is all the fox needs.
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00:07:33,409 --> 00:07:36,891
He has outfoxed the auks.
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00:07:40,677 --> 00:07:45,159
[squawking]
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00:07:45,160 --> 00:07:49,206
Many auk species avoid predation
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00:07:49,207 --> 00:07:50,905
by nesting
on the precarious cliffs.
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00:07:55,518 --> 00:07:57,912
The more perilous their perch,
the better off they are.
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00:08:03,700 --> 00:08:06,224
Each pair only have
one precious offspring.
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00:08:12,883 --> 00:08:16,278
It's only three weeks
since the chick has hatched.
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00:08:21,588 --> 00:08:23,228
But already,
it's eager to leave the nest.
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00:08:26,418 --> 00:08:30,639
It's quite the maiden flight.
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00:08:30,640 --> 00:08:32,440
Hundreds of metres
to the safety of the ocean.
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00:08:36,124 --> 00:08:38,691
And every summer,
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one brave chick
is the first to take the leap.
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00:08:43,479 --> 00:08:44,698
[heroic music playing]
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00:08:51,182 --> 00:08:55,969
It's more like falling
than flying
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as their tiny wings
act as a parachute.
87
00:09:02,063 --> 00:09:03,423
But their fathers
follow them down.
88
00:09:06,763 --> 00:09:08,563
Helping to steer them
towards a water landing.
89
00:09:16,860 --> 00:09:21,081
Soon, the sky begins to fill
with jumpers.
90
00:09:21,082 --> 00:09:24,302
And their chaperones.
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00:09:27,305 --> 00:09:31,831
In just a few days,
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100,000 chicks
will take the leap.
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00:09:32,833 --> 00:09:35,923
None do it alone.
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00:09:39,143 --> 00:09:40,362
But not all make it.
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00:09:42,233 --> 00:09:45,409
[crying]
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00:09:45,410 --> 00:09:46,889
Some fall short
on a dangerous landing strip
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filled with hungry predators.
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00:09:53,636 --> 00:09:57,900
Luckily, Dad is about.
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00:09:57,901 --> 00:09:59,621
And from here,
it's a quick dash to the sea.
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00:10:05,605 --> 00:10:09,869
The chicks that make it
to the water
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have no time to rest.
102
00:10:12,394 --> 00:10:15,004
Not strong enough
to take to the air again,
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the chicks now commence
a heroic migration,
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swimming to waters off Iceland.
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00:10:20,881 --> 00:10:23,578
Even as far as North America.
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00:10:23,579 --> 00:10:25,668
Over 1,000 kilometres away.
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[birds cawing]
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In Alaska,
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the land is also shedding
its icy cloak,
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as streams splash
towards the sea.
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These changes
trigger the arrival
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of another great traveller.
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Sockeye salmon are returning
to Bristol Bay,
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the place they were born.
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00:11:07,492 --> 00:11:10,712
They have migrated thousands
of kilometres
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from the deep ocean,
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using the earth's magnetic field
like a compass.
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The smell of their home stream
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has been imprinted
in their memory since birth.
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[water flowing]
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Their arrival is keenly
anticipated by brown bears,
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who start gathering along
the banks of the bay
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00:11:44,921 --> 00:11:47,054
as the salmon return.
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00:11:50,927 --> 00:11:52,887
They've come for the ultimate
teddy bears' picnic.
125
00:12:01,590 --> 00:12:04,985
As the salmon exhaust the last
of their energy to spawn,
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00:12:06,987 --> 00:12:10,381
they reach the end
of their life cycle.
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00:12:13,994 --> 00:12:15,908
What seems like a river of death
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00:12:15,909 --> 00:12:17,214
is actually a vital regenesis.
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00:12:23,830 --> 00:12:27,224
Rivers usually take nutrients
out to sea.
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00:12:31,185 --> 00:12:34,317
But here,
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00:12:34,318 --> 00:12:38,365
the annual spawning returns
nutrients to the rivers.
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00:12:38,366 --> 00:12:40,671
Feeding not just the bears,
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but also,
the trees for kilometres around.
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00:12:45,765 --> 00:12:47,245
It's a cycle that is reset
every year,
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00:12:49,725 --> 00:12:50,845
where nothing goes to waste.
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00:12:53,860 --> 00:12:56,470
Across North America,
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summer warms the land.
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00:13:01,606 --> 00:13:03,486
California's valleys
are iridescent with growth.
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00:13:07,830 --> 00:13:09,049
Its beaches bustle.
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00:13:15,751 --> 00:13:19,233
Inland, its deserts sizzle.
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00:13:30,374 --> 00:13:35,291
In the rolling sands
of the Sonoran Desert,
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00:13:35,292 --> 00:13:37,468
there's no relief
under the cloudless skies.
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00:13:41,777 --> 00:13:43,213
[rattling]
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00:13:44,911 --> 00:13:47,042
The sidewinder snake
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must change her behaviour
in summer.
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00:13:51,221 --> 00:13:55,877
To avoid the blistering heat,
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00:13:55,878 --> 00:13:57,398
she limits her time
searching for prey,
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00:14:01,623 --> 00:14:03,543
venturing out only
in the early morning and dusk.
149
00:14:03,712 --> 00:14:08,890
Shunning the hot sand,
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00:14:08,891 --> 00:14:11,011
she restricts her contact
to two body parts at a time.
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00:14:13,591 --> 00:14:15,984
The peculiar mode of locomotion
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00:14:15,985 --> 00:14:18,769
helps make her the fastest
rattlesnake on sand.
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00:14:18,770 --> 00:14:21,425
Leaving a J-shaped signature
as she hunts.
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00:14:29,956 --> 00:14:33,394
Dunes like mountains
become a Sisyphean task.
155
00:14:45,667 --> 00:14:49,149
[eerie piano music playing]
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[sand flowing]
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00:15:06,557 --> 00:15:09,952
Persistence is the only option
for this hungry snake.
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00:15:16,741 --> 00:15:21,136
But with little moisture
to carry scent,
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00:15:21,137 --> 00:15:23,139
sniffing out prey is hard.
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00:15:27,535 --> 00:15:30,189
Using special temperature pits
on the side of her head,
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00:15:30,190 --> 00:15:32,322
she scans the environment
for life's heat signal.
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00:15:37,327 --> 00:15:39,502
Able to pick
out the slightest variation
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00:15:39,503 --> 00:15:41,548
between the hot sand
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00:15:41,549 --> 00:15:42,942
and a hot lunch.
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00:15:45,640 --> 00:15:48,772
A gecko is cold-blooded,
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00:15:48,773 --> 00:15:51,173
making it virtually invisible
to the snake's thermal sensors.
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00:15:55,128 --> 00:15:58,479
But that only works
if it stands still.
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00:16:03,745 --> 00:16:05,747
One false movement,
and it's game over.
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00:16:12,058 --> 00:16:16,931
Fortunately, the sidewinder
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00:16:16,932 --> 00:16:18,532
can survive an entire month
without food.
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00:16:21,284 --> 00:16:22,404
Enough time to catch a meal.
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00:16:27,334 --> 00:16:32,338
Deserts cover almost one quarter
of the Earth's surface.
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00:16:32,339 --> 00:16:35,603
But not all deserts
are scorching sand dunes.
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00:16:40,477 --> 00:16:42,261
The arid steppes of Central Asia
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00:16:42,262 --> 00:16:43,480
are an empty, windswept place.
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00:16:47,919 --> 00:16:50,617
But as high summer draws close,
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00:16:50,618 --> 00:16:52,738
scattered rains bring
the promise of greener pastures.
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00:16:56,711 --> 00:16:59,321
Drifting with the season,
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00:16:59,322 --> 00:17:01,122
the nomads of Mongolia
are always on the move.
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00:17:04,806 --> 00:17:08,591
When grazing is scarce,
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00:17:08,592 --> 00:17:09,912
they must travel
longer distances.
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00:17:13,815 --> 00:17:15,535
Over hundreds of kilometres
to find pasture.
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00:17:20,517 --> 00:17:22,477
Their lives are inextricably
tied to their horses.
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00:17:25,131 --> 00:17:26,392
It's been part
of their existence
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00:17:26,393 --> 00:17:27,568
for over 3,000 years.
186
00:17:30,962 --> 00:17:35,879
Children learn to ride
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00:17:35,880 --> 00:17:37,440
almost as soon
as they are able to walk.
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00:17:39,841 --> 00:17:43,496
And summer is the time
for gathering
189
00:17:43,497 --> 00:17:45,673
and racing across country.
190
00:17:52,941 --> 00:17:57,423
The nomads believe to be
without a horse,
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is like a bird without wings.
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[screaming]
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00:18:20,969 --> 00:18:25,364
The nomads depend on their
livestock
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00:18:25,365 --> 00:18:27,322
for all of life's essentials.
195
00:18:27,323 --> 00:18:30,456
So they will stay here
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00:18:30,457 --> 00:18:31,737
as long as there is
enough grass.
197
00:18:34,374 --> 00:18:36,254
Using the sun and stars,
the hills and mountains
198
00:18:36,419 --> 00:18:40,683
to find their way.
199
00:18:40,684 --> 00:18:42,990
For these people,
200
00:18:42,991 --> 00:18:44,111
life is in perpetual motion.
201
00:18:47,952 --> 00:18:52,434
Further westwards,
202
00:18:52,435 --> 00:18:54,088
summer is also transforming
203
00:18:54,089 --> 00:18:55,482
the mighty Himalayas.
204
00:19:02,924 --> 00:19:07,841
The rooftop of the world
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00:19:07,842 --> 00:19:09,362
reaches over 7 kilometres
into the sky.
206
00:19:13,500 --> 00:19:16,067
[triumphant music playing]
207
00:19:21,682 --> 00:19:26,773
Known as the Third Pole,
208
00:19:26,774 --> 00:19:28,209
the Himalayas are home
to the largest body of ice
209
00:19:28,210 --> 00:19:30,386
outside the Arctic
and Antarctica.
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00:19:40,744 --> 00:19:45,357
The heat of the summer
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00:19:45,358 --> 00:19:47,272
causes meltwater
from the mountains
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00:19:47,273 --> 00:19:49,535
to spill into ravines
and fill rivers
213
00:19:49,536 --> 00:19:51,929
running towards the lowlands.
214
00:20:01,374 --> 00:20:07,117
By July,
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00:20:07,118 --> 00:20:09,918
the migration of water from
mountaintops to valleys reaches
a crescendo.
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00:20:18,826 --> 00:20:23,873
In the Terai region of Nepal,
217
00:20:23,874 --> 00:20:25,914
floodplains receive
rich deposits of Himalayan silt,
218
00:20:30,620 --> 00:20:32,012
providing nutrition
219
00:20:32,013 --> 00:20:33,773
for some of the tallest grasses
in the world.
220
00:20:41,065 --> 00:20:45,330
July's lush growing season
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00:20:45,331 --> 00:20:48,115
also cultivates another
222
00:20:48,116 --> 00:20:49,396
of nature's seasonal flourishes.
223
00:20:52,729 --> 00:20:56,645
[buzzing]
224
00:20:56,646 --> 00:20:58,213
Insects.
225
00:21:06,743 --> 00:21:11,530
One particular insect
226
00:21:11,531 --> 00:21:12,811
stirs
from its hibernation state.
227
00:21:17,537 --> 00:21:21,757
Hatching from
water-borne wriggler
228
00:21:21,758 --> 00:21:24,151
into its winged form.
229
00:21:24,152 --> 00:21:27,328
The warm, wet conditions
230
00:21:27,329 --> 00:21:28,409
are perfect for mosquitoes.
231
00:21:35,729 --> 00:21:40,559
Females make a higher pitched
buzz than males,
232
00:21:40,560 --> 00:21:44,040
and it's the females
that cause vexation.
233
00:21:44,041 --> 00:21:46,261
Because only they seek
a blood meal.
234
00:21:50,744 --> 00:21:53,789
It's not just mosquitoes.
235
00:21:53,790 --> 00:21:56,183
Ticks, gnats, flies
236
00:21:56,184 --> 00:21:58,839
all boom at this time of year
as well.
237
00:22:02,669 --> 00:22:06,280
It's impossible to keep up
238
00:22:06,281 --> 00:22:08,121
with the endless swatting
of pesky freeloaders.
239
00:22:14,158 --> 00:22:18,988
The greater one-horned rhino
240
00:22:18,989 --> 00:22:21,861
may appear to have
impenetrable armour.
241
00:22:21,862 --> 00:22:23,982
However, its plates are nothing
but big folds of skin.
242
00:22:30,566 --> 00:22:33,961
And it's the folds
the flies love best.
243
00:22:38,487 --> 00:22:40,183
For these cracks
244
00:22:40,184 --> 00:22:41,620
are the sweatiest parts
of the rhino's body,
245
00:22:41,621 --> 00:22:43,187
full of bacteria
and dead skin cells.
246
00:22:47,583 --> 00:22:49,019
Delicious.
247
00:22:51,370 --> 00:22:53,893
Living with a blanket of bugs
248
00:22:53,894 --> 00:22:54,981
is a constant
summer time irritation
249
00:22:54,982 --> 00:22:56,940
for the rhino.
250
00:22:59,247 --> 00:23:01,204
But help is at hand.
251
00:23:01,205 --> 00:23:03,206
Mynah birds love to forage
252
00:23:03,207 --> 00:23:04,861
on creepy crawlies.
253
00:23:07,864 --> 00:23:08,735
Even the baby rhino
254
00:23:08,736 --> 00:23:09,976
becomes a walking dinner table.
255
00:23:12,869 --> 00:23:14,827
[dramatic music playing]
256
00:23:14,828 --> 00:23:17,438
Despite the irritation
of insects,
257
00:23:17,439 --> 00:23:20,485
for the mynah bird,
258
00:23:20,486 --> 00:23:21,726
they provide a veritable feast.
259
00:23:24,968 --> 00:23:26,361
[buzzing]
260
00:23:29,973 --> 00:23:33,455
[rain pouring]
261
00:23:37,459 --> 00:23:39,068
July and August
262
00:23:39,069 --> 00:23:40,709
are monsoon months
across South East Asia.
263
00:23:43,900 --> 00:23:45,598
[water flowing]
264
00:23:55,695 --> 00:24:00,568
The rains reach into Cambodia,
265
00:24:00,569 --> 00:24:02,169
causing the mighty Mekong River
to flood.
266
00:24:06,836 --> 00:24:11,318
Swollen with so much water,
267
00:24:11,319 --> 00:24:13,407
the river
starts to flow backward,
268
00:24:13,408 --> 00:24:15,323
away from the sea.
269
00:24:18,544 --> 00:24:21,371
The inflow of water
is so immense
270
00:24:21,372 --> 00:24:23,809
that it triggers
the largest freshwater lake
271
00:24:23,810 --> 00:24:25,289
in South East Asia to balloon.
272
00:24:29,076 --> 00:24:31,904
Lake Tonle Sap
273
00:24:31,905 --> 00:24:33,035
grows an astonishing six times
its former size,
274
00:24:33,036 --> 00:24:37,736
becoming a vast inland sea
275
00:24:37,737 --> 00:24:39,057
that swallows
a fifth of Cambodia.
276
00:24:43,656 --> 00:24:48,355
It's one of the biggest
seasonal variations
277
00:24:48,356 --> 00:24:49,879
faced by any people
on the planet.
278
00:24:53,317 --> 00:24:56,145
Roads become rivers.
279
00:24:56,146 --> 00:24:58,306
Houses built on stilts
can now only be reached by boat.
280
00:25:10,987 --> 00:25:14,556
[rowing]
281
00:25:23,086 --> 00:25:28,308
The water teems
282
00:25:28,309 --> 00:25:29,223
with the largest gathering
of freshwater fish in the world,
283
00:25:29,224 --> 00:25:32,878
filling both the lake
284
00:25:32,879 --> 00:25:34,279
and the surrounding
flooded forests.
285
00:25:46,327 --> 00:25:50,591
[chirping]
286
00:25:50,592 --> 00:25:54,508
As the lake grows,
287
00:25:54,509 --> 00:25:56,162
millions of birds migrate here
288
00:25:56,163 --> 00:25:57,363
to feed on the seasonal feast.
289
00:26:00,950 --> 00:26:02,385
They'll stay here
290
00:26:02,386 --> 00:26:04,106
till the life-giving waters
start to recede.
291
00:26:05,868 --> 00:26:06,955
But for now,
292
00:26:06,956 --> 00:26:08,076
it's a fisherman's paradise.
293
00:26:10,917 --> 00:26:12,353
[chirping]
294
00:26:16,662 --> 00:26:20,143
While the natural world
is on the move, humans are too.
295
00:26:26,889 --> 00:26:31,937
It's the last lunar month
of the Islamic calendar.
296
00:26:31,938 --> 00:26:35,070
Millions of pilgrims
travel to the Holy City of Mecca
297
00:26:35,071 --> 00:26:39,422
in Saudi Arabia,
298
00:26:39,423 --> 00:26:40,816
the spiritual centre of Islam.
299
00:26:49,520 --> 00:26:53,959
All Muslims strive
to make The Hajj
300
00:26:53,960 --> 00:26:57,005
at least once in their lives.
301
00:26:57,006 --> 00:26:59,269
Circling the Kaaba seven times,
all sins are dispelled.
302
00:27:10,541 --> 00:27:15,371
Each year,
303
00:27:15,372 --> 00:27:16,808
more than two million pilgrims
gather
304
00:27:16,809 --> 00:27:18,593
to join the sacred sea
of people.
305
00:27:25,078 --> 00:27:29,995
The Islamic calendar
306
00:27:29,996 --> 00:27:31,474
follows the motion of the moon,
not the sun.
307
00:27:31,475 --> 00:27:35,478
It's one of many calendars
across cultures
308
00:27:35,479 --> 00:27:37,279
recording the passing of time
since antiquity.
309
00:27:41,355 --> 00:27:42,877
For the natural world,
310
00:27:42,878 --> 00:27:44,662
the calendar is unwritten.
311
00:27:44,663 --> 00:27:47,100
Length of day.
312
00:27:49,450 --> 00:27:50,669
Falling temperature.
313
00:27:52,714 --> 00:27:54,394
A change in current announces,
"It's time."
314
00:28:00,722 --> 00:28:05,508
Southern right whales
315
00:28:05,509 --> 00:28:07,162
rely on these
natural timekeepers
316
00:28:07,163 --> 00:28:09,209
to know when to move.
317
00:28:12,081 --> 00:28:14,126
Each year,
318
00:28:14,127 --> 00:28:15,257
as winter takes its grip
on the South Pole
319
00:28:15,258 --> 00:28:18,608
and the days become shorter,
320
00:28:18,609 --> 00:28:21,568
whales migrate from the waters
around Antarctica
321
00:28:21,569 --> 00:28:24,354
to the safe harbour
of Australia.
322
00:28:28,924 --> 00:28:31,099
In the warm shallows,
protected from predators,
323
00:28:31,100 --> 00:28:34,538
a young calf
takes a vital breath.
324
00:28:41,981 --> 00:28:45,506
[uplifting music playing]
325
00:28:55,690 --> 00:29:00,563
Here in the calm winter waters,
326
00:29:00,564 --> 00:29:02,204
the calf fattens
up on mother's rich milk.
327
00:29:06,962 --> 00:29:11,009
In a few months
when the days are longer
328
00:29:11,010 --> 00:29:14,099
and the calf is stronger,
329
00:29:14,100 --> 00:29:16,057
they'll embark together
on the long return journey
330
00:29:16,058 --> 00:29:18,713
to the feeding grounds
of Antarctica.
331
00:29:33,380 --> 00:29:37,818
Further south,
332
00:29:37,819 --> 00:29:39,907
in a bay of island Tasmania,
333
00:29:39,908 --> 00:29:42,108
the churning surface of the sea
cloaks what stirs below.
334
00:29:48,395 --> 00:29:50,875
A spindly army of spider crabs
335
00:29:50,876 --> 00:29:52,556
march to the beat
of their primordial drum.
336
00:29:57,360 --> 00:30:01,320
Winter sea temperatures
337
00:30:01,321 --> 00:30:02,481
have triggered their advance.
338
00:30:04,977 --> 00:30:08,109
In places,
339
00:30:08,110 --> 00:30:09,850
they are ten bodies thick,
340
00:30:09,851 --> 00:30:11,171
forming a mountain
of crustaceans.
341
00:30:16,510 --> 00:30:21,383
Hundreds of thousands of crabs
342
00:30:21,384 --> 00:30:23,822
migrating
to the shallows to transform.
343
00:30:29,392 --> 00:30:32,874
An itch here.
344
00:30:35,355 --> 00:30:36,878
A scratch there.
345
00:30:39,446 --> 00:30:42,404
A sign that the old coat
346
00:30:42,405 --> 00:30:43,885
is ready to come off.
347
00:30:46,801 --> 00:30:47,975
One of the first to moult,
348
00:30:47,976 --> 00:30:50,499
this male secretes enzymes
349
00:30:50,500 --> 00:30:52,328
to lift
and separate his old shell.
350
00:31:00,075 --> 00:31:04,383
He cracks through
351
00:31:04,384 --> 00:31:05,602
to reveal his new coat,
352
00:31:08,605 --> 00:31:09,824
bright orange and soft.
353
00:31:14,220 --> 00:31:18,092
His shell offers no protection
until it hardens.
354
00:31:18,093 --> 00:31:22,140
Now, at the most vulnerable
moment in his life,
355
00:31:22,141 --> 00:31:25,056
the very crowd
he sought for protection
356
00:31:25,057 --> 00:31:28,060
turn against him.
357
00:31:30,671 --> 00:31:31,890
[dramatic music playing]
358
00:31:35,284 --> 00:31:37,644
All around, newly moulted crabs
are hunted and ripped apart.
359
00:31:47,731 --> 00:31:52,561
This mutilated crab
360
00:31:52,562 --> 00:31:54,042
limps desperately
searching for cover.
361
00:31:57,916 --> 00:32:01,049
But he's an easy target.
362
00:32:04,444 --> 00:32:06,184
Even with four missing limbs,
363
00:32:06,185 --> 00:32:08,491
he fights back.
364
00:32:14,497 --> 00:32:17,936
Perhaps these angels
will give him sanctuary.
365
00:32:24,768 --> 00:32:28,294
Safe at last.
366
00:32:31,340 --> 00:32:32,780
In time,
he'll eventually regenerate.
367
00:32:36,215 --> 00:32:39,391
His attackers
368
00:32:39,392 --> 00:32:40,610
may not be so lucky.
369
00:32:44,179 --> 00:32:46,379
Smooth stingrays arrive
for this all-you-can-eat buffet.
370
00:32:52,100 --> 00:32:53,380
It's hard to know where
to start.
371
00:32:55,408 --> 00:32:56,538
Entree.
372
00:32:56,539 --> 00:32:58,063
Main.
373
00:32:59,542 --> 00:33:02,328
Dessert.
374
00:33:05,809 --> 00:33:09,725
And with a flick of his tail,
375
00:33:09,726 --> 00:33:11,685
he is back for seconds.
376
00:33:15,341 --> 00:33:17,301
The crabs' only defence
is in their sheer numbers.
377
00:33:20,346 --> 00:33:23,043
By dawn,
378
00:33:23,044 --> 00:33:24,218
hundreds have been hoovered up.
379
00:33:24,219 --> 00:33:25,299
[suspenseful music playing]
380
00:33:38,016 --> 00:33:42,497
Finally satiated,
381
00:33:42,498 --> 00:33:43,847
the rays slink into the murk.
382
00:33:48,896 --> 00:33:52,421
[sad music playing]
383
00:33:56,773 --> 00:34:00,907
The surviving spider crabs
384
00:34:00,908 --> 00:34:02,561
march solemnly
towards the depths,
385
00:34:02,562 --> 00:34:04,955
stepping over fallen comrades.
386
00:34:08,568 --> 00:34:09,786
Or is it leftover lunch?
387
00:34:19,274 --> 00:34:23,712
This mob will meet again
next year
388
00:34:23,713 --> 00:34:26,324
for the same gruesome event
389
00:34:26,325 --> 00:34:27,674
in Tasmania's winter waters.
390
00:34:34,072 --> 00:34:39,293
On the continent of Africa,
391
00:34:39,294 --> 00:34:41,454
it's the movement of rain
that sets the pulse for life.
392
00:34:44,256 --> 00:34:48,215
By August,
393
00:34:48,216 --> 00:34:51,392
one of the natural world's
greatest migrationsis now
underway.
394
00:34:51,393 --> 00:34:53,873
On the border of Kenya
and Tanzania,
395
00:34:53,874 --> 00:34:55,745
wildebeest are on the move.
396
00:34:59,184 --> 00:35:02,882
Having left the Serengeti,
397
00:35:02,883 --> 00:35:04,683
they have travelled
over 500 kilometres north.
398
00:35:08,802 --> 00:35:12,500
Towards the savannah grasslands
of the Masai Mara,
399
00:35:12,501 --> 00:35:15,330
storms on the horizon
are their beacon.
400
00:35:20,422 --> 00:35:22,684
They know instinctively
that where there's rain.
401
00:35:22,685 --> 00:35:25,123
there's greener pastures.
402
00:35:29,910 --> 00:35:34,218
As the living tributaries
converge,
403
00:35:34,219 --> 00:35:36,698
the wildebeest grow in numbers.
404
00:35:36,699 --> 00:35:39,659
[stampeding]
405
00:35:44,490 --> 00:35:47,928
Soon the herd
is over one million strong.
406
00:35:55,327 --> 00:35:59,808
By August,
407
00:35:59,809 --> 00:36:01,089
the herd reaches the Mara River.
408
00:36:05,728 --> 00:36:09,167
The crocodiles
have been expecting them.
409
00:36:22,963 --> 00:36:27,314
For some,
410
00:36:27,315 --> 00:36:29,098
this is the first time
411
00:36:29,099 --> 00:36:30,539
they've encountered
such an obstacle.
412
00:36:33,103 --> 00:36:34,663
Others know all too well
what's to come.
413
00:36:37,325 --> 00:36:38,979
Herd leaders assess the danger,
414
00:36:44,202 --> 00:36:47,162
searching for a crossing point
where the odds seem just a
little bit better.
415
00:36:49,990 --> 00:36:53,253
They pause at the water's edge,
416
00:36:53,254 --> 00:36:54,995
waiting for someone
to break rank.
417
00:37:07,181 --> 00:37:11,924
Somehow,
418
00:37:11,925 --> 00:37:13,245
he makes it past
the waiting jaws.
419
00:37:17,583 --> 00:37:21,108
Then, the dam breaks.
420
00:37:25,417 --> 00:37:28,942
[triumphant music playing]
421
00:37:37,472 --> 00:37:42,346
In an hour,
422
00:37:42,347 --> 00:37:43,867
thousands will cross
at this one point.
423
00:37:46,916 --> 00:37:50,398
Most will make it.
424
00:37:59,233 --> 00:38:02,758
Some will not.
425
00:38:07,502 --> 00:38:11,027
The river takes its sacrifice.
426
00:38:24,693 --> 00:38:28,218
As the rain clouds move on,
427
00:38:31,570 --> 00:38:32,832
so too do the wildebeests.
428
00:38:36,575 --> 00:38:37,775
To the lust pastures of Kenya.
429
00:38:41,841 --> 00:38:43,059
[calming music playing]
430
00:38:50,893 --> 00:38:55,549
Further south, in Zambia,
431
00:38:55,550 --> 00:38:58,465
the lack of rain
and relentless sunshine
432
00:38:58,466 --> 00:39:00,338
sucks the life from the earth.
433
00:39:13,699 --> 00:39:18,442
The clear blue skies
434
00:39:18,443 --> 00:39:19,803
are welcomed
by Carmine bee-eaters.
435
00:39:22,969 --> 00:39:27,015
Every year,
436
00:39:27,016 --> 00:39:27,974
they migrate hundreds
of kilometres southward
437
00:39:27,975 --> 00:39:31,063
to converge here,
438
00:39:31,064 --> 00:39:32,152
on Zambia's Luangwa River.
439
00:39:36,243 --> 00:39:38,243
As the water level drops,
it exposes the riverbank.
440
00:39:52,825 --> 00:39:57,176
This is what the birds
are seeking.
441
00:39:57,177 --> 00:39:59,222
For it's where they nest.
442
00:40:02,312 --> 00:40:04,880
[triumphant music playing]
443
00:40:18,677 --> 00:40:23,376
[chirping]
444
00:40:23,377 --> 00:40:25,423
Each bird rushes
to secure a spot.
445
00:40:30,123 --> 00:40:31,515
But they won't necessarily
get their first choice.
446
00:40:31,516 --> 00:40:34,867
Resident white-fronted
bee-eaters are already here.
447
00:40:36,651 --> 00:40:41,525
They live year-round
in the region.
448
00:40:41,526 --> 00:40:43,286
And recently moved
to the riverbank to breed.
449
00:40:46,835 --> 00:40:48,395
They've had a head start
making burrows.
450
00:40:50,970 --> 00:40:54,582
And won't be evicted
without a fight.
451
00:40:55,975 --> 00:40:59,457
[chirping]
452
00:41:03,548 --> 00:41:05,550
[triumphant music playing]
453
00:41:13,079 --> 00:41:17,125
But the migrants
haven't travelled this far
454
00:41:17,126 --> 00:41:18,954
for nothing.
455
00:41:29,225 --> 00:41:32,751
[chirping]
456
00:41:37,712 --> 00:41:40,032
A prime patch of real estate
is worth every flying feather.
457
00:41:44,719 --> 00:41:48,505
Both bird species
dig into the riverbank
458
00:41:48,506 --> 00:41:51,117
to lay their eggs.
459
00:41:54,686 --> 00:41:58,384
The location of the burrow
is key.
460
00:41:58,385 --> 00:42:02,823
Too close to the bottom
461
00:42:02,824 --> 00:42:04,384
and reptiles
can barge through the door.
462
00:42:09,004 --> 00:42:14,095
Too close to the top,
463
00:42:14,096 --> 00:42:15,976
and they're in easy reach
for other egg thieves.
464
00:42:19,449 --> 00:42:21,669
The middle of the bank
is optimum.
465
00:42:26,195 --> 00:42:27,315
Passers-by can do just that.
466
00:42:33,333 --> 00:42:38,206
Thankfully,
467
00:42:38,207 --> 00:42:39,727
all neighbourhoods
have access to food.
468
00:42:43,299 --> 00:42:46,388
Even mid-dry season,
469
00:42:46,389 --> 00:42:47,564
permanent waterholes
of the Luangwa River
470
00:42:47,565 --> 00:42:51,176
harbour aquatic insects.
471
00:42:51,177 --> 00:42:52,457
And the birds
are nimble hunters.
472
00:42:59,054 --> 00:43:02,536
But their favourite food
is along the riverbank.
473
00:43:07,193 --> 00:43:09,716
In August,
474
00:43:09,717 --> 00:43:10,877
the sausage tree is in bloom.
475
00:43:15,375 --> 00:43:18,944
That's a boom for bees.
476
00:43:22,208 --> 00:43:23,601
And bee-eaters.
477
00:43:25,864 --> 00:43:27,866
[chirping]
478
00:43:36,701 --> 00:43:41,182
The only problem with this diet
479
00:43:41,183 --> 00:43:42,620
is the sting in the tail.
480
00:43:46,058 --> 00:43:47,178
But that's quickly disabled.
481
00:44:05,381 --> 00:44:09,689
Like all halcyon days,
482
00:44:09,690 --> 00:44:10,909
they'll soon be over.
483
00:44:15,087 --> 00:44:19,917
The bee-eaters must hatch
and fledge their chicks
484
00:44:19,918 --> 00:44:21,638
before the rains return
and the river rises.
485
00:44:22,485 --> 00:44:27,402
When this happens,
486
00:44:27,403 --> 00:44:28,926
the riverbank nests
will vanish underwater.
487
00:44:28,927 --> 00:44:31,843
And the birds will once again,
take to the wing.
488
00:44:39,546 --> 00:44:44,550
The great animal migrations
on the African continent
489
00:44:44,551 --> 00:44:47,119
are rivalled by similar
migrations in the African seas.
490
00:44:53,691 --> 00:44:55,300
Along the KwaZulu-Natal
coastline in South Africa,
491
00:44:55,301 --> 00:44:59,521
the arrival
of a cold-water current
492
00:44:59,522 --> 00:45:02,829
sweeps up the coast,
493
00:45:02,830 --> 00:45:04,270
carrying with it
a bloom of plankton.
494
00:45:08,053 --> 00:45:10,271
This cool, northwards flow
495
00:45:10,272 --> 00:45:12,312
helps propel billions
of sardines in search of food.
496
00:45:28,682 --> 00:45:33,555
At their peak,
497
00:45:33,556 --> 00:45:35,427
shoals can span over
seven kilometres,
498
00:45:35,428 --> 00:45:37,517
providing an irresistible lure
for predators.
499
00:45:42,957 --> 00:45:47,265
Army of common dolphins,
15,000 or more,
500
00:45:47,266 --> 00:45:49,790
arrive ready to strike
in a coordinated assault.
501
00:45:56,188 --> 00:46:00,452
They separate
the school of sardines,
502
00:46:00,453 --> 00:46:03,498
corralling the fish
503
00:46:03,499 --> 00:46:04,819
by blowing
a barricade of bubbles.
504
00:46:11,420 --> 00:46:14,859
Weaving them
into tighter and tighter balls.
505
00:46:19,385 --> 00:46:22,779
[clicking]
506
00:46:22,780 --> 00:46:25,042
As they push the sardines
to the surface,
507
00:46:25,043 --> 00:46:26,483
the tiny fish
have nowhere to escape.
508
00:46:32,746 --> 00:46:36,184
The oily scent of the battle
attracts more hungry predators.
509
00:46:42,538 --> 00:46:46,150
Dusky sharks move in
510
00:46:46,151 --> 00:46:47,586
to take advantage
of the dolphins' hard work.
511
00:46:47,587 --> 00:46:49,458
[dramatic music playing]
512
00:46:54,463 --> 00:46:56,383
Jaws slash through
the bait balls with precision.
513
00:47:03,864 --> 00:47:07,302
The churn on the surface signals
to the aerial attack force.
514
00:47:12,873 --> 00:47:14,874
Gannets hover.
515
00:47:14,875 --> 00:47:16,485
Then they too, join the fury.
516
00:47:21,273 --> 00:47:24,842
[intense music playing]
517
00:47:45,427 --> 00:47:50,344
Diving at
100 kilometres an hour,
518
00:47:50,345 --> 00:47:52,025
they strike the water
and torpedo to depth.
519
00:47:55,655 --> 00:47:56,874
[intense music playing]
520
00:48:17,372 --> 00:48:20,898
But the feast is worth it.
521
00:48:25,119 --> 00:48:26,598
The predators
along this coastline
522
00:48:26,599 --> 00:48:29,775
cannot always rely
523
00:48:29,776 --> 00:48:31,096
on the sardines
passing their way.
524
00:48:34,955 --> 00:48:39,698
[clicking]
525
00:48:39,699 --> 00:48:42,179
Warming oceans
means the cool currents
526
00:48:42,180 --> 00:48:45,138
which trigger the sardine run
527
00:48:45,139 --> 00:48:46,539
have been happening
later and later.
528
00:48:49,578 --> 00:48:51,840
Some years,
529
00:48:51,841 --> 00:48:53,973
the run has failed completely.
530
00:48:53,974 --> 00:48:57,368
For many species
across our planet,
531
00:48:57,369 --> 00:49:00,632
the timing of natural events
is changing
532
00:49:00,633 --> 00:49:03,548
because of rising
global temperatures.
533
00:49:03,549 --> 00:49:06,725
For the creatures
adapted so precisely
534
00:49:06,726 --> 00:49:10,076
to nature's biological clock,
535
00:49:10,077 --> 00:49:11,599
climate change presents
a new rhythm they must shift to.
536
00:49:11,600 --> 00:49:15,256
If they can.
537
00:49:17,998 --> 00:49:20,739
If they cannot,
538
00:49:20,740 --> 00:49:22,620
many of the great migration
events on our planet
539
00:49:25,092 --> 00:49:26,440
may diminish,
540
00:49:26,441 --> 00:49:27,660
or simply disappear.
38604
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