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The gigantic giraffe...
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..boasts some impressive stats.
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It's the tallest mammal on Earth.
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Nearly three times the height of a
professional basketball player.
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And as heavy as a car.
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But have you ever considered what it
takes to feed such a massive frame?
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Or how this giant overcomes
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the rather difficult problem of
drinking?
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Being one of Earth's big beasts has
its advantages,
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but also comes with sizeable
challenges.
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How they overcome life's
big problems...
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..can be truly jaw-dropping.
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Whether it involves a total
meltdown...
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..a brutal battle...
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..or maintaining their own
air-conditioning,
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it seems they've got it licked.
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It's time to meet a remarkable group
of animals.
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Nature's Biggest Beasts.
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From the behemoths of a
bygone age...
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..to the leviathans of
our modern world...
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..it's the biggest beasts that
capture our imagination.
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But size is relative.
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And there are surprising giants
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lurking in places you might
not expect.
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Animals whose claim to fame is
simply being amongst
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the biggest of their kind.
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00:02:30,980 --> 00:02:36,340
But whether they are a titan in a
tiny world or a giant among
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other giants, they all share
the same basic challenges.
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Moving their massive bodies.
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Surviving extreme temperatures.
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Having huge babies.
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And, not least, the need to eat.
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A lot.
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Let's begin with an incontestable
big beast.
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Those giraffes.
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Nearly six metres of mostly leg
and neck,
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perched on feet the size of
dinner plates.
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Being head and shoulders above
the rest does have its perks.
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Seeing for miles around.
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Reaching 35mph,
with its ground-eating strides.
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And, of course, 1.8 metres of neck
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and an extra 50cm of tongue means
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it can reach the food its
competitors can't.
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Just as well, because a giraffe has
a supersized appetite...
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..which it needs to satisfy by
eating foliage.
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To get enough nutrients from just
a few leaves per bite,
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a large male must consume up to
65kg daily.
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To eat through that many leaves
a day can take up to 18 hours.
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But never mind feeding...
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..in dry times, a giraffe can need
up to 38 litres of water
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every few days.
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But how to get it when it's
seemingly so hard to come by?
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Well, it has a neat trick.
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By eating at dawn when
condensation is high,
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it can absorb most of its moisture
from leaves.
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00:06:04,500 --> 00:06:08,060
It also wastes no water sweating
or panting.
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Instead, its temperature fluctuates
with the surrounding air.
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But when beaten by the heat,
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giraffes must join their fellow
beasts at the watering hole.
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Being tall, it's tricky.
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In this pose, the pressure is quite
literally on.
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Pumping blood against gravity up to
the head takes a powerful heart.
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It beats up to 170 times a minute.
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That's twice as fast as ours.
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This huge blood pressure,
the highest of any mammal,
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should give a drinking giraffe
a bad head rush.
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But instead, a clever system of
valves regulates
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blood flow to the brain.
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The giraffe controls blood pressure
so well that Nasa has taken
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inspiration from these humble
goliaths
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for the design of its spacesuits.
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It seems this big beast can even
teach us a thing or two.
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The unique physical characteristics
of a giraffe allow it to feed with
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relative ease.
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Many big beasts, though, have to
fight for their food.
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00:08:29,660 --> 00:08:34,420
This remote Indonesian island is
home to an illustrious lizard.
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It owes its prehistoric good looks
to its age.
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It's one of the few living species
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to have been around for over three
million years.
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The Komodo dragon.
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Earth's largest lizard.
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Big enough to hog a king-sized bed
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and then some.
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00:09:33,340 --> 00:09:35,980
Despite their intimidating
credentials,
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these dragons don't have it easy.
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Around 6,000 remain, making them
vulnerable to extinction.
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00:09:51,620 --> 00:09:54,860
To add to their woes,
these ferocious beasts
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have, for their size,
a bite that is weaker
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than that of
the average house cat.
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00:10:06,180 --> 00:10:10,860
Their survival, though, relies on
satisfying their insatiable hunger.
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These dragons have set their sights
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on this buffalo.
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At ten times a dragon's size, it's
a very dangerous dinner option.
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One well aimed kick, and a dragon
could die hungry.
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So, how does a Komodo, with its
measly nip,
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take on such a formidable adversary?
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Its bite may be weak,
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but it's bolstered by around 60
backward facing, serrated teeth.
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The grip and rip bite.
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00:11:30,620 --> 00:11:34,300
On prey this size, it just draws
a bit of blood.
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It's more deadly than it looks,
though.
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The bite has set the dragon's next
weapon in motion.
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Tucked either side of this
lizard's weak jaw are venom glands.
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A bite releases the poison,
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preventing the prey's blood from
clotting.
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Stage two takes days and days of
patience.
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The buffalo's wound is not healing.
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Three weeks later, and it's finally
time to eat.
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These ravenous reptiles can polish
off 80% of their body weight in
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a single sitting.
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No energy gets wasted on chewing,
either.
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00:13:14,580 --> 00:13:17,780
A tube running from the base of the
tongue to the lungs
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means a dragon can breathe while it
swallows each mouthful...
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..in one.
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00:13:33,180 --> 00:13:38,380
This combination of clever
adaptations means this big beast can
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take down even bigger beasts to
satisfy its need to eat
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and ensure its survival.
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THUNDER RUMBLES
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Enormous appetites have led many
sizeable species to target prey
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that should be out of their league.
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00:14:11,380 --> 00:14:14,380
And the big bugs of the undergrowth
are no exception.
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Imagine an insect that's big enough
to take on a bird.
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00:14:29,020 --> 00:14:32,180
Meet the Kalahari's armoured
ground cricket.
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00:14:40,980 --> 00:14:45,900
This hulk of the insect world puts
its tiny European cousins to shame.
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00:14:50,300 --> 00:14:54,260
As an omnivore, it eats plants,
insects, and crops.
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But there's one more thing it
really needs.
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Red-billed quelea follow the rain,
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00:15:06,100 --> 00:15:09,740
gorging on crops that spring up in
the now fertile ground.
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00:15:21,020 --> 00:15:23,620
They're feeding not just themselves,
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but another million tiny mouths back
at their nests.
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And that is precisely where these
immense vertebrates are headed too.
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You see, life as a giant cricket is
tough.
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Protein is crucial for these
goliaths
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to sustain their huge frames.
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00:16:00,300 --> 00:16:03,660
So they must seize any opportunity
to eat meat.
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00:16:20,180 --> 00:16:23,300
It's hard to slip under the radar,
though, when you're massive.
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00:16:33,500 --> 00:16:36,340
So they've evolved some nifty
defences.
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A spiny, beak-proof armoured shell
protects its insides.
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00:16:51,060 --> 00:16:54,180
And it can fire blood from pores in
its exoskeleton...
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..temporarily blinding its
assailant.
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With the security out of the way,
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the meat feast is finally
within reach.
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This big beast has evolved to use
its brawn and its weapons to get
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the meal it needs to stay alive.
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00:18:04,180 --> 00:18:08,020
The leaf litter is rife with
oversized invertebrates,
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with appetites to match.
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00:18:14,660 --> 00:18:16,580
The Kinabalu giant red leech
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would span the
whole length
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of a grown
man's thigh.
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00:18:22,180 --> 00:18:26,060
It maintains its full figure by
eating its next-door neighbour.
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00:18:29,300 --> 00:18:31,140
The Bornean blue earthworm.
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00:18:32,900 --> 00:18:34,580
It's even bigger than the leech...
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..stretching to below
a grown man's knee.
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In this battle of the titans,
though, it's the smallest that wins.
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The leech's muscular mouth crushes
the worm,
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taking the phrase "down in one" to
the extreme.
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New Zealand's carnivorous
Powelliphanta is the sumo wrestler
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of the snail world.
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The largest can grow to the size of
a fist, and that is just the shell.
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00:19:25,460 --> 00:19:29,740
Their unfortunate prey is scraped
into the gullet by a rasp-like
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structure embellished with
6,000 teeth.
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Japan's finger-length giant hornet
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is one of the largest, heaviest,
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and deadliest insects in the world.
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It feeds on the larvae of the
humble honeybee.
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To get to its meal, it must fight
its way into the hive.
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A team of 30 can decimate a
30,000-strong hive in
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just three hours.
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BUZZING
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Our big beasts may have got their
dining options sorted, but for some,
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size poses another challenge,
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when nature turns up the thermostat.
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The Australian outback.
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Temperatures here can hit
50 degrees Celsius.
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The red kangaroo is the world's
largest marsupial.
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It can grow to a towering height of
almost two metres.
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A single leap can cover
seven metres,
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allowing them to hit a top speed
of 35mph.
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But any exercise generates heat.
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00:22:02,060 --> 00:22:06,420
Big bodies like these have
comparatively small surface areas,
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making it hard for heat to escape.
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As the temperature soars,
they head for shade.
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To cool their overheating bulk,
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they paste themselves in their
own refreshing saliva.
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00:22:38,460 --> 00:22:42,300
Their forearms are covered in
a cobweb of capillaries.
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00:22:42,300 --> 00:22:45,780
As the saliva evaporates,
their blood cools.
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The blue parts of this thermal image
are the coldest,
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showing just how effective
their saliva bath can be.
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They also dig down beneath
the scorching earth
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to the cooler soil below,
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to sit out the worst of
the day's heat.
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00:23:19,100 --> 00:23:22,260
Sometimes, the simplest solutions
are the cleverest.
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In Australia's Northern Territory,
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a famously sun-averse mammal is
also wrestling with the temperature.
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Staying cool just requires escaping
the jaws of death.
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The little red flying fox is
not so little.
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00:24:15,380 --> 00:24:17,140
It's a species of mega bat...
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00:24:20,300 --> 00:24:23,220
..with a body as big as a rat,
and heavier....
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00:24:26,220 --> 00:24:27,700
..and a wingspan of a metre.
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00:24:33,580 --> 00:24:37,380
If temperatures hit a tipping point
of 40 degrees Celsius,
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00:24:37,380 --> 00:24:39,820
hundreds of these big bats can die.
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It's 38 degrees.
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Dangerously near the death zone.
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300,000 bats are dehydrating.
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00:24:59,660 --> 00:25:03,460
Their burly bodies are producing
more heat than they can release.
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What they really need is water.
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00:25:16,900 --> 00:25:20,420
Skimming the river's surface with
their chests is refreshing.
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00:25:21,700 --> 00:25:23,100
But more importantly,
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it collects water in the hairs to
lick off back at the roost
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and quench their thirst.
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00:25:32,220 --> 00:25:36,140
But they are not the only ones
making the most of the river.
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This is the Australian freshwater
crocodile.
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Or freshie, to the locals.
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The sun makes these cold-blooded
reptiles alert,
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00:25:58,260 --> 00:25:59,700
and ready to hunt.
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00:26:18,980 --> 00:26:22,180
This deadly game of tag is
non-negotiable.
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00:26:24,260 --> 00:26:27,500
If they don't risk becoming fodder
for a freshie
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00:26:27,500 --> 00:26:29,180
they'll die in the heat.
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00:26:43,900 --> 00:26:46,580
Fortune favours these brave bats.
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00:26:49,620 --> 00:26:50,660
Most of the time.
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00:27:05,500 --> 00:27:08,980
So, being big is not so great
when it's hot.
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00:27:10,940 --> 00:27:13,940
But can a bulky frame help
stave off the cold?
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00:27:18,740 --> 00:27:21,500
Well, if you're warm-blooded
the answer is yes.
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Mammals tend to be beefier in
cooler climes.
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00:27:30,660 --> 00:27:34,100
Take the biggest bear on earth,
the polar bear.
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00:27:36,620 --> 00:27:42,260
Its huge volume stores the heat in
temperatures as low as -37 Celsius.
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00:27:45,460 --> 00:27:49,900
And their 10cm blubber layer is
such an effective insulator,
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00:27:49,900 --> 00:27:54,060
these mighty mammals sometimes need
a good rub in the snow to cool down.
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00:28:02,820 --> 00:28:05,140
But, if you're cold-blooded,
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00:28:05,140 --> 00:28:08,420
you rely on a daily dose of sun
to warm up your insides.
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00:28:10,460 --> 00:28:14,220
So reptiles and insects generally
fare better in the cold
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00:28:14,220 --> 00:28:15,580
when they're small.
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00:28:18,500 --> 00:28:22,820
Some species, though, just can't
help but defy convention.
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00:28:24,980 --> 00:28:28,420
Remember the gargantuan bird-eating
cricket of the Kalahari?
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00:28:30,540 --> 00:28:32,900
Well, it has a distant cousin,
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00:28:32,900 --> 00:28:35,740
that beats it hands down in the
size stakes.
237
00:28:39,260 --> 00:28:42,780
This colossal beast is
the mountain stone weta...
238
00:28:45,180 --> 00:28:48,140
..an insect that's grown as big as
a mouse...
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00:28:49,820 --> 00:28:51,140
..for one simple reason.
240
00:28:54,980 --> 00:28:58,980
Wetas evolved back when there were
no native mammals.
241
00:28:58,980 --> 00:29:03,300
So they took the ecological niche
normally reserved for small rodents
242
00:29:03,300 --> 00:29:05,060
and matched them for size.
243
00:29:10,820 --> 00:29:13,580
Being a massive insect is fine
when it's warm...
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00:29:14,940 --> 00:29:19,380
..but this monster species lives
high in New Zealand's Southern Alps.
245
00:29:32,060 --> 00:29:35,780
It had to evolve a way to survive
being big in the cold...
246
00:29:38,460 --> 00:29:42,220
..by doing something no other
insect this large can.
247
00:29:46,900 --> 00:29:50,340
Even in the shelter of a cave,
it can be below zero.
248
00:29:52,140 --> 00:29:54,260
When ice sets in around it,
249
00:29:54,260 --> 00:29:58,900
this ingenious hulk of an insect
does something very strange indeed.
250
00:30:01,700 --> 00:30:04,060
It freezes itself to death...
251
00:30:05,420 --> 00:30:07,300
..nearly.
252
00:30:14,780 --> 00:30:16,940
This weta species
253
00:30:16,940 --> 00:30:20,100
actually encourages ice to form
in its body.
254
00:30:23,660 --> 00:30:25,740
Ice crystals are sharp.
255
00:30:25,740 --> 00:30:29,700
If they form inside a cell,
they tear through the membrane,
256
00:30:29,700 --> 00:30:31,300
like razor blades in a balloon.
257
00:30:35,020 --> 00:30:40,820
So the key to survival is to ensure
ice only forms outside its cells.
258
00:30:44,020 --> 00:30:48,460
First the weta dehydrates the cells,
drawing water out.
259
00:30:49,980 --> 00:30:53,220
There, the combination of water and
special proteins
260
00:30:53,220 --> 00:30:55,700
trigger the formation
of ice crystals.
261
00:31:07,700 --> 00:31:13,020
In this state of suspended animation
a mountain stone weta can survive
262
00:31:13,020 --> 00:31:16,300
temperatures as low as -10 Celsius.
263
00:31:20,420 --> 00:31:24,380
An extraordinary 80% of its body can
be frozen solid.
264
00:31:35,380 --> 00:31:37,900
When temperatures rise and
the ice thaws...
265
00:31:39,100 --> 00:31:42,420
..a weta can gradually re-enter
the land of the living.
266
00:32:03,700 --> 00:32:06,340
Having got their temperature
under control,
267
00:32:06,340 --> 00:32:08,820
our big beasts can go about
their day.
268
00:32:09,860 --> 00:32:13,580
But the simple act of moving can be
challenging in itself.
269
00:32:19,220 --> 00:32:22,220
Generally, the bigger the beast,
the more it weighs.
270
00:32:25,940 --> 00:32:27,500
And the heavier the beast,
271
00:32:27,500 --> 00:32:30,340
the harder it finds lifting its
weight against
272
00:32:30,340 --> 00:32:32,660
the downward pull of gravity.
273
00:32:39,940 --> 00:32:45,180
Take Earth's largest land animal,
the six-tonne African elephant.
274
00:32:49,620 --> 00:32:52,300
Tracking down food in
the Namibian desert
275
00:32:52,300 --> 00:32:57,060
can mean lugging its eye-watering
load for 25 miles a day.
276
00:33:03,780 --> 00:33:06,660
Two thirds of an elephant's weight
is channelled
277
00:33:06,660 --> 00:33:08,140
through its front legs.
278
00:33:14,340 --> 00:33:15,500
The solution?
279
00:33:15,500 --> 00:33:20,100
Fatty pads in its dustbin-sized
feet to absorb the shock.
280
00:33:25,100 --> 00:33:27,820
With each step,
they spread the load,
281
00:33:27,820 --> 00:33:31,980
protecting the skeleton from the
impact of its monumental weight.
282
00:33:38,500 --> 00:33:42,260
Even with the help of ingenious
evolutionary adaptation, though,
283
00:33:42,260 --> 00:33:47,180
the fact remains that gravity limits
how big a land animal can get.
284
00:33:56,140 --> 00:33:58,180
So, how do big beasts fare...
285
00:34:03,660 --> 00:34:05,060
..beneath the waves?
286
00:34:11,700 --> 00:34:16,420
Down here, water's buoyancy helps
support nature's heavyweights.
287
00:34:22,140 --> 00:34:25,940
Which is why this is the domain of
the most enormous animal...
288
00:34:27,260 --> 00:34:28,300
..ever to have existed.
289
00:34:33,540 --> 00:34:40,060
The 150-tonne blue whale outdoes
even the biggest dinosaurs for size.
290
00:34:44,700 --> 00:34:47,860
Its tongue alone weighs as much
as its largest land rival,
291
00:34:47,860 --> 00:34:49,340
the elephant.
292
00:34:52,820 --> 00:34:55,820
Its heart is almost as big as
a golf buggy.
293
00:34:59,060 --> 00:35:02,380
Its major artery is as wide as
a human head.
294
00:35:05,060 --> 00:35:07,460
And it's thought they're still
growing.
295
00:35:11,220 --> 00:35:14,100
As long as the blue whale has
enough food,
296
00:35:14,100 --> 00:35:17,380
this species may just keep on
getting bigger.
297
00:35:22,260 --> 00:35:27,180
Despite its eye-popping stats,
the blue whale can move with ease.
298
00:35:31,620 --> 00:35:36,140
Which is more than can be said for
excessively heavy beasts that want
299
00:35:36,140 --> 00:35:37,460
to get airborne.
300
00:35:44,420 --> 00:35:49,260
Some birds have found benefits
to growing big, but in the process,
301
00:35:49,260 --> 00:35:51,180
they've lost the ability to fly.
302
00:35:56,380 --> 00:35:57,900
Take the kakapo,
303
00:35:57,900 --> 00:35:59,820
the world's heaviest parrot.
304
00:36:08,900 --> 00:36:12,580
To reach the fruit and leaves that
maintain its full figure,
305
00:36:12,580 --> 00:36:14,820
it has no choice but to climb.
306
00:36:22,500 --> 00:36:24,460
The ostrich has a similar problem.
307
00:36:27,660 --> 00:36:29,860
It's the largest living bird.
308
00:36:29,860 --> 00:36:31,260
Nearly three metres tall...
309
00:36:32,700 --> 00:36:36,660
..with a vast two-metre wingspan
that is useless for flying.
310
00:36:39,820 --> 00:36:44,260
Instead, it's perfected the art
of running away from predators.
311
00:36:49,940 --> 00:36:53,260
With a top speed of over 40mph,
312
00:36:53,260 --> 00:36:56,500
it's the fastest two-legged animal
on Earth.
313
00:36:56,500 --> 00:37:00,260
It could complete a marathon in
45 minutes.
314
00:37:11,140 --> 00:37:14,620
Being big, though, doesn't have to
make air travel impossible.
315
00:37:18,860 --> 00:37:21,500
Over 65 million years ago,
316
00:37:21,500 --> 00:37:25,620
a beast far larger and heavier than
an ostrich proudly displayed its
317
00:37:25,620 --> 00:37:29,020
aerial skills in the skies above
what is now Europe.
318
00:37:36,500 --> 00:37:40,980
Hatzegopteryx may well be the
largest flying animal ever known.
319
00:37:50,140 --> 00:37:51,580
If it were alive today,
320
00:37:51,580 --> 00:37:54,460
it would be tall enough peer into
a first-floor window.
321
00:37:59,540 --> 00:38:02,220
And they could take off from
a standing start,
322
00:38:02,220 --> 00:38:04,740
owing to the sheer power of
their wing muscles.
323
00:38:11,100 --> 00:38:13,740
Despite their impressive
aerial antics,
324
00:38:13,740 --> 00:38:17,460
it seems they didn't hunt on
the wing, but fed on the ground...
325
00:38:20,180 --> 00:38:24,340
..supporting their great weight with
extra feet on each wing.
326
00:38:40,540 --> 00:38:45,540
Back in the 21st century, the bird
that comes closest to a Hatze,
327
00:38:45,540 --> 00:38:46,940
is the albatross.
328
00:38:56,420 --> 00:38:59,460
At 3.5 metres, the wandering
albatross
329
00:38:59,460 --> 00:39:03,420
has the longest wingspan
of any bird alive today.
330
00:39:09,340 --> 00:39:12,740
And the albatross can do something
Hatze apparently couldn't.
331
00:39:14,980 --> 00:39:16,220
Hunt from the air.
332
00:39:19,340 --> 00:39:23,060
These big birds spend most of
their lives at sea,
333
00:39:23,060 --> 00:39:25,660
scouring the ocean's surface
for food.
334
00:39:40,940 --> 00:39:43,820
They only come in to land to breed.
335
00:39:49,260 --> 00:39:52,540
This royal albatross has made
a pit stop
336
00:39:52,540 --> 00:39:54,780
on New Zealand's South Island,
337
00:39:54,780 --> 00:39:57,540
where her two-month-old chick is
waiting for food.
338
00:40:09,500 --> 00:40:14,660
This big baby can polish off half a
kilo of fish in a single sitting.
339
00:40:20,580 --> 00:40:26,420
To find its next meal, Mum will have
to scour a mere 600 miles of ocean.
340
00:40:30,140 --> 00:40:33,220
So, given she weighs as much
as a small dog,
341
00:40:33,220 --> 00:40:35,260
how does she manage to fly?
342
00:40:40,740 --> 00:40:43,940
Her enormous wings get her big body
airborne.
343
00:40:45,060 --> 00:40:48,060
The secret to the albatross staying
up there, though,
344
00:40:48,060 --> 00:40:49,180
is in its nostrils.
345
00:40:54,860 --> 00:41:00,340
Special sensory organs measure
the speed of the surrounding air.
346
00:41:00,340 --> 00:41:03,940
What they're searching for are
changes in airspeed.
347
00:41:07,100 --> 00:41:10,980
At the water's surface,
the air is almost still,
348
00:41:10,980 --> 00:41:12,660
slowed as it hits the waves.
349
00:41:18,660 --> 00:41:20,660
Ten metres up, it's windier.
350
00:41:23,420 --> 00:41:27,500
As an albatross climbs into the
faster air it gets free lift.
351
00:41:29,820 --> 00:41:33,700
Then, turning sharply, it plunges
down into the slower air.
352
00:41:36,620 --> 00:41:40,540
Gravity has helped it accelerate to
over 70mph.
353
00:41:56,980 --> 00:42:02,180
Downward momentum catapults it back
up again like a roller-coaster
354
00:42:02,180 --> 00:42:03,820
into the lift of the faster air.
355
00:42:06,900 --> 00:42:09,140
It's called dynamic soaring.
356
00:42:11,860 --> 00:42:16,260
And, crucially, it means they can
fly without flapping their wings.
357
00:42:26,580 --> 00:42:29,300
By exploiting the energy of
the wind,
358
00:42:29,300 --> 00:42:31,700
they expend almost none of
their own.
359
00:42:34,460 --> 00:42:39,260
This aerial efficiency is what makes
such a big body capable of flying
360
00:42:39,260 --> 00:42:41,820
nonstop for over 10,000 miles
361
00:42:41,820 --> 00:42:46,540
without the need to set foot on
dry land for years at a time.
362
00:42:57,260 --> 00:43:00,780
For a mother, though, it's straight
back to the nest,
363
00:43:00,780 --> 00:43:04,060
to satisfy the big appetite of
her chunky chick.
364
00:43:15,700 --> 00:43:18,340
The demands of rearing massive
offspring
365
00:43:18,340 --> 00:43:21,340
is something many a big beast
can appreciate.
366
00:43:25,460 --> 00:43:28,220
The challenges often begin at birth.
367
00:43:39,100 --> 00:43:42,700
Because of her size, a hippo
keeps cool in water.
368
00:43:44,740 --> 00:43:49,860
It's here that she'll usually
deliver her 45kg, metre-long baby.
369
00:43:54,660 --> 00:43:56,180
Which leaves her with a problem.
370
00:44:00,780 --> 00:44:02,940
Her little one can't breathe
underwater...
371
00:44:04,300 --> 00:44:08,140
..giving Mum just 40 seconds to get
her newborn to the surface
372
00:44:08,140 --> 00:44:10,100
for its first gulp of air.
373
00:44:26,300 --> 00:44:30,500
Elephant babies spend nearly two
years in the womb to reach
374
00:44:30,500 --> 00:44:32,980
their record-breaking 100kg
birth weight.
375
00:44:36,820 --> 00:44:40,500
They take so long to grow,
that Mum has to nurse them
376
00:44:40,500 --> 00:44:41,900
for up to four years.
377
00:44:55,700 --> 00:44:57,700
For some big beasts, though,
378
00:44:57,700 --> 00:45:01,620
the trials of the mating game begin
long before the birth.
379
00:45:09,180 --> 00:45:13,020
It's the breeding season on the
beaches of northern Patagonia.
380
00:45:19,340 --> 00:45:25,500
Over 15,000 female southern elephant
seals have flocked here to find
381
00:45:25,500 --> 00:45:28,060
themselves a truly massive mate.
382
00:45:35,060 --> 00:45:39,980
A bull seal can be a staggering
eight times his suitor's size.
383
00:45:42,300 --> 00:45:45,620
He can weigh as much
as six dairy cows.
384
00:45:54,700 --> 00:45:58,020
And yet, she's not the one in danger
of getting injured in this game.
385
00:45:59,380 --> 00:46:00,420
He is.
386
00:46:01,580 --> 00:46:04,380
To secure his legacy,
a male must mate
387
00:46:04,380 --> 00:46:07,700
with as many lucky ladies as
possible.
388
00:46:14,940 --> 00:46:19,860
These females are all under
the watchful eye of one bull.
389
00:46:24,380 --> 00:46:28,500
He's the beach master of a harem
that can number 150.
390
00:46:32,740 --> 00:46:35,420
To protect his exclusive
mating rites,
391
00:46:35,420 --> 00:46:41,420
he has to stay on his beach
territory 24/7 without food or drink
392
00:46:41,420 --> 00:46:43,460
for three months.
393
00:46:46,100 --> 00:46:48,580
Luckily for him, he's really fat.
394
00:46:50,740 --> 00:46:55,180
His 15cm blubber, born of a diet
of just seafood,
395
00:46:55,180 --> 00:46:57,420
provides him with energy and water.
396
00:47:04,340 --> 00:47:07,020
For an extra boost while napping,
397
00:47:07,020 --> 00:47:10,140
he holds his breath for minutes at
a time.
398
00:47:10,140 --> 00:47:11,980
Every ounce of energy must be saved.
399
00:47:21,420 --> 00:47:24,020
Competitors are always nearby.
400
00:47:56,180 --> 00:47:59,380
It's a battle of bulk and teeth.
401
00:48:10,060 --> 00:48:14,380
His fat suit can't protect him from
his rival's 8cm canines.
402
00:48:35,460 --> 00:48:37,660
But even after months of fasting,
403
00:48:37,660 --> 00:48:40,420
the beach master defeats his
challenger.
404
00:48:56,220 --> 00:48:59,900
His prize - to father most of
the pups this season.
405
00:49:05,140 --> 00:49:08,100
For the loser, it's game over.
406
00:49:08,100 --> 00:49:11,740
Three quarters of bulls each year
never get to mate.
407
00:49:16,620 --> 00:49:19,980
It's the bigger the better in the
elephant seal mating game.
408
00:49:35,660 --> 00:49:39,620
Securing the next generation is
a risky business.
409
00:49:39,620 --> 00:49:41,900
Not just for males.
410
00:49:41,900 --> 00:49:44,580
One beast has grown so big,
411
00:49:44,580 --> 00:49:47,500
that having babies means gambling
with her life.
412
00:49:55,340 --> 00:49:57,820
The humble hermit crab.
413
00:49:57,820 --> 00:50:01,060
Harmless and, traditionally, small.
414
00:50:05,020 --> 00:50:07,540
Except for this member of
the family.
415
00:50:12,060 --> 00:50:13,100
The coconut crab.
416
00:50:14,100 --> 00:50:17,780
Or robber crab.
The largest land crab on earth.
417
00:50:22,020 --> 00:50:25,940
The South Pacific islands of Vanuatu
are pretty hard to reach.
418
00:50:30,100 --> 00:50:32,700
So having the place mostly to
themselves,
419
00:50:32,700 --> 00:50:35,700
it seems that these critters have
taken the opportunity
420
00:50:35,700 --> 00:50:38,140
to grow as big as
medium-sized mammals.
421
00:50:40,620 --> 00:50:42,340
Their legs can span a metre.
422
00:50:44,220 --> 00:50:48,220
And they're strong enough to lift
the equivalent of ten house bricks.
423
00:50:52,380 --> 00:50:56,060
Being big has allowed them to
cultivate some rare talents.
424
00:51:02,500 --> 00:51:04,980
True to their name, they can crack
a coconut.
425
00:51:08,660 --> 00:51:11,180
And they've been known to kill
and eat rats.
426
00:51:14,060 --> 00:51:17,100
But there's one thing these crabs
simply can't do.
427
00:51:18,060 --> 00:51:19,540
And that is swim.
428
00:51:27,100 --> 00:51:30,700
This crab lives its adult life
entirely on land,
429
00:51:30,700 --> 00:51:33,180
so you'd think this wouldn't be
too much of a problem.
430
00:51:34,540 --> 00:51:36,980
And for most of their days,
it isn't.
431
00:51:44,060 --> 00:51:48,660
But once a year, the females of
these colossal crustaceans have
432
00:51:48,660 --> 00:51:52,780
no choice but to brave the waves in
order to pass on their genes.
433
00:52:12,140 --> 00:52:16,460
This female has been nursing her
fertilised eggs on her abdomen,
434
00:52:16,460 --> 00:52:17,940
having mated some weeks ago.
435
00:52:19,740 --> 00:52:22,900
But tonight is the night to release
her precious cargo.
436
00:52:30,820 --> 00:52:33,380
And, like all crabs, that's done
in water.
437
00:52:41,260 --> 00:52:42,700
She must tread carefully.
438
00:52:43,740 --> 00:52:45,820
She's so well adapted to land
439
00:52:45,820 --> 00:52:48,300
that she's evolved a form of
lung that
440
00:52:48,300 --> 00:52:50,220
can no longer breathe underwater.
441
00:52:53,220 --> 00:52:56,060
And her great weight means if she
gets out of her depth,
442
00:52:56,060 --> 00:52:57,420
she'll sink...
443
00:52:58,420 --> 00:52:59,460
..and drown.
444
00:53:05,020 --> 00:53:09,020
Clinging for life, she releases
her eggs into the waves.
445
00:53:17,660 --> 00:53:20,100
They'll hatch into swimming larva.
446
00:53:25,340 --> 00:53:28,020
But in a month's time,
they'll be back on land...
447
00:53:32,460 --> 00:53:35,300
..where they too will grow into
terrestrial giants.
448
00:53:53,220 --> 00:53:58,020
Across the coral sea from the
coconut crab's paradise isle is
449
00:53:58,020 --> 00:54:02,020
an immense sea beast that also
reproduces just once a year.
450
00:54:04,900 --> 00:54:07,820
When it does, it gets even bigger.
451
00:54:13,460 --> 00:54:18,900
This springtime full moon is the
trigger for a submarine spectacular.
452
00:54:21,460 --> 00:54:23,980
When the perfect tide height,
day length,
453
00:54:23,980 --> 00:54:25,900
and sea temperature all align...
454
00:54:27,540 --> 00:54:28,580
..this happens.
455
00:54:37,220 --> 00:54:42,180
400 species of coral
across 3,000 reefs reproduce
456
00:54:42,180 --> 00:54:44,580
over a series of nights.
457
00:54:51,740 --> 00:54:55,060
Tucked inside
their limestone armour,
458
00:54:55,060 --> 00:54:59,420
millions of coral polyps release
their eggs and sperm simultaneously.
459
00:55:06,500 --> 00:55:10,100
You may be wondering what's big
about these tiny floating jewels.
460
00:55:11,220 --> 00:55:13,900
Well, together are responsible for
growing
461
00:55:13,900 --> 00:55:16,660
the world's largest single
living structure.
462
00:55:19,020 --> 00:55:20,420
The Great Barrier Reef.
463
00:55:31,220 --> 00:55:35,900
At 1,400 miles long, it's over twice
the length of Great Britain...
464
00:55:37,740 --> 00:55:40,700
..making it the only living thing
visible from space.
465
00:55:46,460 --> 00:55:51,260
Each time the reef reproduces,
its gigantic scale increases.
466
00:55:57,220 --> 00:55:59,900
The resulting coral larvae travel
back down
467
00:55:59,900 --> 00:56:02,460
to make their home on the reef.
468
00:56:08,740 --> 00:56:14,140
This monumental structure once grew
by several centimetres each year.
469
00:56:21,740 --> 00:56:24,140
Of course, there's a twist
to this tale.
470
00:56:29,860 --> 00:56:31,500
In recent years,
471
00:56:31,500 --> 00:56:35,540
it's thought that half the coral in
this big beast has died.
472
00:56:37,940 --> 00:56:40,940
It's believed rising sea
temperatures are responsible
473
00:56:40,940 --> 00:56:44,460
for driving away the colourful algae
that live inside coral.
474
00:56:46,460 --> 00:56:49,780
Without nutrients and its
distinctive hues,
475
00:56:49,780 --> 00:56:51,740
it's left bleached white.
476
00:56:56,300 --> 00:57:02,020
It appears our modern world is
taking its toll on this great beast.
477
00:57:09,980 --> 00:57:13,740
We may not be amongst nature's
biggest beasts,
478
00:57:13,740 --> 00:57:17,780
but we do so often have the biggest
impact on our planet and on
479
00:57:17,780 --> 00:57:19,180
the animals we share it with.
480
00:57:22,700 --> 00:57:26,260
Our fascination with the goliaths of
our world can prove
481
00:57:26,260 --> 00:57:28,500
catastrophic for them.
482
00:57:32,300 --> 00:57:37,260
And nature's giants can't survive
without ample space to roam,
483
00:57:37,260 --> 00:57:39,660
plenty to eat, and prime habitat.
484
00:57:48,020 --> 00:57:52,860
Half the remarkable titans featured
here are threatened with extinction.
485
00:58:00,380 --> 00:58:04,500
When you consider the astonishing
solutions nature's biggest beasts
486
00:58:04,500 --> 00:58:06,860
have come up with to life's
big problems...
487
00:58:13,260 --> 00:58:18,340
..ingenious ways to find food,
to keep warm or stay cool,
488
00:58:18,340 --> 00:58:20,860
to move around,
and to reproduce...
489
00:58:24,020 --> 00:58:26,780
..we should not only celebrate
their success,
490
00:58:26,780 --> 00:58:32,340
but also do what we can to ensure
they stick around for generations
to come.
41122
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