♪♪ NARRATOR: Creatures come both great and small... but it's the goliaths that always capture our attention.

They might be the biggest beast that ever lived -- or simply the biggest of their kind.

If they're not titans to everyone, they still manage to be their own brand of monster.

And all these "giants" face enormous challenges to survive.

Take the largest lizard on Earth -- how can it feed its huge appetite when its bite is weaker than a house cat's?

How does a giraffe, the world's tallest animal, not pass out when it stoops to drink?

How does a mega bat cool its bulky body in croc-infested waters?

Turns out nature's biggest beasts have come up with some fascinating ways to overcome life's biggest problems.

♪♪ ♪♪ ♪♪ [ Stomp ] NARRATOR: From the behemoths of a bygone age... to the leviathans of our modern world... it's the biggest beasts that stand out from the crowd.

♪♪ But size is relative... and there are surprising giants lurking in places you might not expect.

♪♪ Animals whose claim to fame is simply being among the biggest of their kind.

♪♪ But whether they're a titan in a tiny world or a giant among other giants, they all share the same basic challenges: [ Elephant trumpets ] Moving their massive bodies... ♪♪ Surviving extreme temperatures... ♪♪ Having huge babies... ♪♪ And not least, the need to eat... A lot.

♪♪ The biggest appetite on the planet undoubtedly belongs to this monster of the sea.

♪♪ Its heart is almost as big as a golf cart.

♪♪ Its tongue weighs as much as an elephant.

♪♪ Its major artery is as wide as a human head.

♪♪ This legendary record-breaker is, quite simply, the most enormous animal ever to have existed.

♪♪ It's the blue whale of course.

At 150 tons it outdoes even the biggest dinosaurs for size.

♪♪ ♪♪ Their astonishing bulk is entirely sustained by this tiny crustacean... krill.

The secret to getting so big on something so small is eating four tons of them a day.

♪♪ ♪♪ ♪♪ ♪♪ These floating vacuum cleaners can suck up half a million calories in a single gulp.

♪♪ That's just as well, because opening such a massive mouth takes a lot of energy, so the more it can eat it one go, the bigger it can get... And it's thought they're still growing.

♪♪ As long as the blue whale has enough food, this species may just keep on getting bigger.

♪♪ Back on dry land, Earth's tallest mammal has also had to adapt to get enough nutrients.

♪♪ The gigantic giraffe... ♪♪ boasts some impressive stats.

At up to 19 feet of mostly leg and neck, it towers to nearly 3 times the height of a professional basketball player.

It's as heavy as a car.

[ Car horn honks ] And it perches on feet the size of dinner plates.

♪♪ Being head and shoulders above the rest does have its perks.

Seeing for miles around.

♪♪ ♪♪ Reaching 35 miles an hour with its ground-eating strides.

♪♪ And of course with over seven feet of neck and an extra foot and a half of tongue, it can reach the food its competitors can't.

They need that advantage because a giraffe has a super-sized appetite.

♪♪ Which it satisfies by eating foliage.

To get enough nutrients from just a few leaves per bite, a large male must consume up to 145 pounds daily.

To eat through that many leaves a day can take up to 18 hours.

But never mind feeding.

In dry times a giraffe can need up to seven or eight gallons of water every few days... but how to get it, when it's seemingly so hard to come by?

Well, it has a neat trick.

By eating at dawn when condensation is high, it can absorb most of its moisture from leaves.

It also wastes no water sweating or panting, instead its temperature fluctuates with the surrounding air.

♪♪ But when beaten by the heat, giraffes must join their fellow beasts at the watering hole.

♪♪ Being tall it's...tricky.

♪♪ In this pose, the pressure is, quite literally, on.

♪♪ Pumping blood all the way up to its head takes a powerful heart.

It beats up to 170 times a minute -- that's twice as fast as ours.

♪♪ This huge blood pressure, the highest of any mammal, should give a drinking giraffe a bad head rush.

♪♪ But instead, a clever system of valves regulates blood flow to the brain.

♪♪ The giraffe controls blood pressure so well that NASA has taken inspiration from these humble goliaths for the design of its space suits.

♪♪ It seems this big beast can even teach us a thing or two.

♪♪ ♪♪ The unique physical characteristics of a giraffe, allow it to feed with relative ease.

Many big beasts, though, have to fight for their food.

This remote Indonesian island is home to an illustrious lizard.

♪♪ ♪♪ It owes its prehistoric good looks to its extraordinary age.

It's one of the few living species to have been around for over 3 million years.

♪♪ The Komodo Dragon.

♪♪ Earth's largest lizard.

Big enough to hog a king-size bed... and then some.

♪♪ ♪♪ Despite their intimidating credentials, these dragons don't have it easy.

Only around 6,000 remain, making them vulnerable to extinction.

♪♪ To add to their woes, these ferocious beasts have, for their size, a bite that is weaker than that of the average house cat.

Their survival, though, relies on satisfying their beastly hunger.

These dragons have set their sights on this buffalo.

At 10 times a dragon's size, it's a very dangerous dinner option.

♪♪ One well aimed kick and a dragon could die hungry.

♪♪ So, how does a komodo, with its measly nip, take on such a formidable adversary?

Its bite may be weak, but it's bolstered by around 60 backward-facing, serrated teeth.

♪♪ The grip-and-rip bite.

♪♪ ♪♪ On prey this size, it draws just a bit of blood...

But it's more deadly than it looks.

♪♪ The bite has set the dragon's next weapon in motion.

Tucked either side of this lizard's weak jaw are venom glands.

♪♪ A bite releases the poison, preventing the prey's blood from clotting.

Stage two takes days and days of patience.

The buffalo's wound is not healing.

♪♪ Three weeks later, it's finally time to eat.

♪♪ Now ravenous, these reptiles can polish off 80% of their body-weight in a single sitting.

♪♪ No energy gets wasted on chewing either -- a tube running from the base of the tongue to the lungs means a dragon can breathe while it swallows each mouthful... in one.

♪♪ This combination of clever adaptations means this big beast can take down even bigger beasts to satisfy its need to eat and ensure its survival.

♪♪ [ Thunder rolling in distance ] Enormous appetites have led many sizeable species to target prey that should be out of their league.

And the big bugs of the undergrowth are no exception.

Imagine an insect that's big enough, to take on a bird.

Meet the Kalahari's massive armored ground cricket.

Protein is crucial for these goliaths to sustain their huge frames, so they must seize any opportunity to eat meat.

Their unfortunate prey?

Red-billed quelea chicks.

Reaching their meal means getting past the parents.

[ Squirting ] By firing blood from pores in its exoskeleton, the cricket temporarily blinds its assailant.

With security out of the way, the meat feast is finally within reach.

The leaf litter is rife with oversized invertebrates, with appetites to match.

♪♪ The Kinabalu giant red leech, would span the whole length of a grown man's thigh.

It maintains its full figure, by eating its next door neighbor...

The Bornean blue earthworm.

It's even bigger than the leech, stretching to below a grown man's knee.

♪♪ In this battle of the titans, though, it's the smallest that wins.

♪♪ The leech's muscular mouth crushes the worm, taking the phrase "down in one" to the extreme.

♪♪ New Zealand's carnivorous Powelliphanta snail can grow to the size of a fist -- and that is just the shell.

They're the sumo wrestlers of the snail world.

♪♪ Their unfortunate prey is scraped into the gullet by a rasp-like structure, embellished with 6,000 teeth.

♪♪ Japan's finger-length giant hornet is one of the largest, heaviest, and deadliest insects in the world.

It feeds on the larvae of the humble honey bee.

♪♪ To get to its meal, it must fight its way into the hive.

♪♪ A team of 30, can decimate a bee hive 30,000 strong in just a few hours.

♪♪ For all their killer credentials though, these giants do have an Achilles heel... A size-related issue, which can be used against them.

And some bee colonies have wised-up to this weakness.

These bees seem to welcome their attacker into their hive.

Sure enough, the hornet helps itself to a snack.

But as its powerful mandibles chow down on the bee's body, an explosion of attack pheromones is released from the bee.

Now the tribe strikes.

♪♪ By vibrating their flight muscles, they generate heat.

♪♪ Bees, with their tiny bodies, can withstand up to 180 degrees Fahrenheit.

But hornets overheat at four degrees less.

♪♪ The lone hornet scout's big body is both its weapon and its weakness.

Thanks to its size, it's roasted alive.

♪♪ Overheating is a deadly problem faced by big beasts all across the world.

♪♪ Large bodies have comparatively small surface areas, making it hard for heat to escape.

♪♪ In Australia's Northern Territory, a famously sun-averse mammal is wrestling with the temperature.

♪♪ To stay cool, it must escape the jaws of death.

♪♪ ♪♪ The little red flying fox isn't really so little.

It's a species of megabat.

With a body as big as a rat, and heavier.

And a wingspan of three feet.

If temperatures hit a tipping point of 104 degrees Fahrenheit, hundreds of these big bats can die.

♪♪ It's 100 degrees, dangerously near the death zone.

300,000 bats are dehydrating.

Their burly bodies are producing more heat than they can release.

What they really need is water.

♪♪ Skimming the river's surface with their chests is refreshing -- but more importantly, it collects water in the hairs, to lick off back at the roost and quench their thirst.

But they're not the only ones making the most of the river.

♪♪ This is the Australian freshwater crocodile or "freshie" to the locals.

♪♪ The sun makes these cold-blooded reptiles alert... and ready to hunt.

♪♪ ♪♪ This deadly game of tag is non-negotiable.

If they don't risk becoming fodder for a freshie, they'll die in the heat.

♪♪ ♪♪ Fortune favors these brave bats... most of the time.

So being big is not so great when it's hot.

But can a bulky frame help stave off the cold?

♪♪ Well, if you're warm-blooded, the answer is yes.

Mammals tend to be beefier in cooler climes.

Take the biggest bear on Earth: the polar bear.

Its huge volume stores the heat in temperatures as low as minus-50 degrees Fahrenheit.

And their four-inch layer of blubber is such an effective insulator, these mighty mammals sometimes need a good rub in the snow to cool down.

But if you're cold-blooded, you rely on a daily dose of sun to warm up your insides.

So reptiles and insects generally fare better in the cold when they're small.

Some species, though, just can't help but defy convention.

Remember the gargantuan bird-eating cricket of the Kalahari?

Well it has a distant cousin, that beats it hands down in the size stakes.

This colossal beast is the mountain stone weta... An insect, that's grown as big as a mouse, for one simple, reason.

Wetas evolved back when there were no native mammals.

So they took the ecological niche normally reserved for small rodents -- and matched them for size.

♪♪ Being a massive insect is fine when it's warm, but this monster species lives high in New Zealand's Southern Alps.

♪♪ ♪♪ It had to evolve a way to survive being big in the cold... By doing something no other insect this large can.

♪♪ Even in the shelter of a cave it can be below freezing.

When ice sets in around it, this ingenious hulk of an insect does something very strange indeed.

It freezes itself to death -- almost.

♪♪ This weta species actually encourages ice to form in its body.

Ice crystals are sharp.

If they form inside a cell, they'd tear through the membrane like razor blades in a balloon.

♪♪ So the key to survival is to ensure ice only forms outside its cells.

First the weta dehydrates the cells, drawing water out.

There, the combination of water and special proteins trigger the formation of ice crystals.

♪♪ In this state of suspended animation, a mountain stone weta can survive temperatures as low as 14 degrees Fahrenheit.

An extraordinary 80% of its body can be frozen solid.

♪♪ ♪♪ When temperatures rise and the ice thaws, a weta can gradually re-enter the land of the living.

♪♪ ♪♪ ♪♪ Having gotten their temperature under control, our big beasts can go about their day.

But the simple act of moving can be challenging in itself.

Generally, the bigger the beast, the more it weighs.

And the heavier the beast, the harder it finds lifting its weight against the downward pull of gravity.

Take Earth's largest land animal, the six-and-a-half ton African Elephant.

Tracking down food in the Namibian desert can mean lugging its eye-watering load for 25 miles a day.

Two-thirds of an elephant's weight is channeled through its front legs.

The solution?

Fatty pads in its bucket-sized feet to absorb the shock.

With each step they spread the load, protecting their skeleton from the impact of their monumental weight.

[ Elephant trumpets ] Though even with the help of ingenious evolutionary adaptations, the fact remains that gravity limits how big a land animal can get.

So how do big beasts fare... ...beneath the waves?

The world's oceans are home to some of the most incredible heavyweights on earth.

The great white shark needs no introduction.

Suffice to say at 20 feet and up to 5,000 pounds... it's one of the most feared big beasts on the planet.

It's outsized, though, by the world's largest dolphin: the 12,000 pound orca.

[ Orca calling ] The giant Pacific octopus has broken records at 30 feet across.

It's powerful enough to attack and eat sharks.

The six-foot Humboldt squid is as large as a man.

These voracious hunters work in packs, devouring up to nine tons of fish a night.

If food is scarce, they've been known to eat each other.

The weightlessness of water allows underwater goliaths -- even those as vast as the blue whale -- to move with ease.

Which is more than can be said for excessively heavy beasts that want to get airborne.

Some birds have found benefits to growing big, but in the process, they've lost the ability to fly.

♪♪ Take the ostrich.

It's the largest living bird -- nine feet tall, with a vast six-and-a-half-foot wingspan -- that is useless for flying.

Instead, it's perfected the art of running away from predators.

♪♪ With a top speed of over 40 miles per hour, it's the fastest two-legged animal on earth.

It could run a full marathon in 45 minutes.

♪♪ Being big, though, doesn't have to make air travel impossible.

Over 65 million years ago, a beast far larger and heavier than an ostrich proudly displayed its aerial skills in the skies above what is now Europe.

♪♪ Hatzegopteryx may well be the largest flying animal ever known.

♪♪ If it were alive today, it'd be tall enough to peer into a second-floor window.

♪♪ And they could take off from a standing start owing to the sheer power of their wing muscles.

♪♪ Despite their impressive aerial antics, it seems they didn't hunt on the wing, but fed on the ground.

Supporting their great weight with extra feet on each wing.

♪♪ ♪♪ Back in the 21st century, the bird that comes closest to a hatze is the albatross.

At 11 feet, the wingspan of the wandering albatross is the longest of any bird alive today.

And an albatross can do something a hatze apparently couldn't -- hunt from the air.

These big birds spend most of their lives at sea, scouring the ocean's surface for food.

They only come in to land, to breed.

This royal albatross has made a pit-stop on New Zealand's South Island, where her two-month-old chick is waiting for food.

This big baby can polish off a pound of fish in a sitting.

To find its next meal, mom will have to scour a mere 600 miles of ocean, So given she weighs as much as a small dog, how does she manage to fly?

♪♪ Her enormous wings get her big body airborne.

The secret to the albatross staying up there, though, is in its nostrils.

♪♪ Special sensory organs measure the speed of the surrounding air.

What they're searching for are changes in air speed.

At the water's surface, the air is almost still -- slowed as it hits the waves.

♪♪ 30 feet up, it's windier.

As an albatross climbs into the faster air, it gets free lift.

Then, turning sharply, it plunges down into the slower air.

Gravity helps it accelerate to over 70 miles per hour.

♪♪ ♪♪ Downward momentum catapults it back up again, like a roller coaster, into the lift of the faster air.

It's called "dynamic soaring" -- and, crucially, it means they can fly without flapping their wings.

♪♪ ♪♪ By exploiting the energy of the wind, they expend almost none of their own.

♪♪ This aerial efficiency is what makes such a big body capable of flying non-stop for over 10,000 miles without the need to set foot on dry land for years at a time.

♪♪ For a mother, though, it's straight back to the nest to satisfy the big appetite of her chunky chick.

The demands of rearing massive offspring is something many a big beast can appreciate.

The challenges often begin at birth.

♪♪ Because of her size, a hippo keeps cool in water.

It's here that she'll usually deliver her 100-pound, three-foot baby.

Which leaves her with a problem.

♪♪ Her little-one can't breathe under water, giving mom just 40 seconds to get her new born to the surface for its first gulp of air.

♪♪ ♪♪ For some big beasts, though, securing the next generation means risking their own lives.

The humble hermit crab.

Harmless... and traditionally, small.

Except for this member of the family.

The coconut crab, or robber crab -- the largest land crab on earth.

The South Pacific islands of Vanuatu are pretty hard to reach.

So having the place mostly to themselves, it seems these critters have taken the opportunity to grow as big as medium-sized mammals.

Their legs can span some three feet.

And they're strong enough to lift the equivalent of 10 house bricks.

♪♪ Being big has allowed them to cultivate some rare talents.

♪♪ True to their name, they can crack a coconut.

And they've been known to kill and eat rats.

But there's one thing these crabs simply can't do, and that is: swim.

♪♪ This crab lives its adult life entirely on land, so you'd think this wouldn't be too much of a problem.

And for most of their days, it isn't.

But once a year, the females of these colossal crustaceans have no choice but to brave the waves in order to pass on their genes.

Having mated a few weeks ago, this female has been nursing her fertilized eggs on her abdomen.

But tonight's the night to release her precious cargo.

And like all crabs, that's done in water.

She must tread carefully.

She's so well adapted to land that she's evolved a form of lung that can no longer breathe underwater.

And her great weight means if she gets out of her depth, she'll sink and drown.

Clinging on for life, she releases her eggs into the waves.

They'll hatch into swimming larvae.

But in a month's time, they'll be back on land.

There, they too will grow into terrestrial giants.

Across the Coral Sea from the coconut crabs' paradise isle is an immense sea beast that also reproduces just once a year.

When it does, it gets even bigger.

This spring-time full moon is the trigger for a submarine spectacular.

When the perfect tide height, day length, and sea temperature all align...

This happens.

♪♪ Some 400 species of coral across 3,000 reefs reproduce over a series of nights.

♪♪ Tucked inside their limestone armor, millions of coral polyps release their eggs and sperm, simultaneously.

♪♪ You may be wondering, what's big about these tiny floating jewels?

Well, together, they're responsible for growing the world's largest single living structure.

The Great Barrier Reef.

♪♪ At 1,400 miles long, it's almost the vertical length of the United States, making it the only living thing visible from space.

♪♪ Each time the reef reproduces, its gigantic scale increases.

♪♪ The resulting coral larvae travel back down to make their home on the reef.

♪♪ This monumental structure once grew by several inches each year.

♪♪ Of course, now there's a twist to this tale.

♪♪ In recent years, it's thought that half the coral in this big beast has died.

It's believed rising sea temperatures are responsible for driving away the colorful algae that live inside coral.

Without nutrients and its distinctive hues, it's left bleached white.

♪♪ It appears our modern world is taking its toll on this greatest of beasts.

♪♪ We may not be among Nature's biggest beasts, but we do so often have the biggest impact on our planet and on the animals we share it with.

Our fascination with the goliaths of our world can prove catastrophic for them.

Half the remarkable titans featured here are threatened with extinction.

♪♪ When you consider the astonishing solutions nature's biggest beasts have come up with to life's big problems... ♪♪ ...ingenious ways to find food, to keep warm or stay cool, to move around and to reproduce; we should not only celebrate their success, but also do what we can to ensure they stick around for generations to come.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this "Nature" program, visit pbs.org.

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