0:00:06 > 0:00:09'Welcome to my Deadly Top Ten...'
0:00:10 > 0:00:12Woah!
0:00:14 > 0:00:16'..A chance to choose the most extreme,
0:00:16 > 0:00:17'mass-attacking,
0:00:17 > 0:00:20'defending, airborne
0:00:20 > 0:00:22'and super-sensing animals on the planet.'
0:00:22 > 0:00:24Quick, quick, quick, quick, quick!
0:00:24 > 0:00:27'All deadly in their own world and occasionally, deadly to me.'
0:00:27 > 0:00:28Aarghh!
0:00:28 > 0:00:31'Who do you think will be number one of the Deadly Top Ten?
0:00:38 > 0:00:40'In this show, I'll be counting down
0:00:40 > 0:00:43'deadly hunters that survive in some of the most
0:00:43 > 0:00:44'extreme places on the planet.
0:00:46 > 0:00:48'In searing heat,
0:00:48 > 0:00:50'at dangerous depths,
0:00:50 > 0:00:54'inside creepy caves and even in the coldest places on Earth.
0:00:54 > 0:00:57'These predators make surviving look easy.
0:00:59 > 0:01:03'So, buckle up as we take a rollercoaster ride around the world,
0:01:03 > 0:01:05'finding my...
0:01:05 > 0:01:07'Deadly Top Ten Extreme.
0:01:14 > 0:01:16'Hold on tight, because at ten is
0:01:16 > 0:01:20'the high-altitude Himalayan snow leopard.
0:01:24 > 0:01:28'Their home is the extreme cold, dry cliffs
0:01:28 > 0:01:29'of the Central Asian mountains.
0:01:29 > 0:01:33'Over 5,000 metres above sea level, the steep,
0:01:33 > 0:01:36'broken terrain is harsh and forbidding,
0:01:36 > 0:01:38'and the air is thin with little oxygen.
0:01:40 > 0:01:42'But the snow leopard is perfectly adapted
0:01:42 > 0:01:45'to slink over loose rocks and scramble up and down
0:01:45 > 0:01:48'vertical faces, on the hunt for prey.
0:01:48 > 0:01:54'Their camouflage is incredible. They blend in without a trace.'
0:01:54 > 0:01:57This is probably our best chance of seeing things.
0:01:57 > 0:02:00We're just at the tree line, and all around us,
0:02:00 > 0:02:02the hillsides are open.
0:02:02 > 0:02:04So, we can see for a long, long way.
0:02:07 > 0:02:09Oh, hang on!
0:02:09 > 0:02:11There's a huge herd of animals.
0:02:12 > 0:02:15For an ambush predator like a snow leopard,
0:02:15 > 0:02:17this is kind of easy game.
0:02:17 > 0:02:20'Snow leopards are built to go off-road.
0:02:20 > 0:02:22'Their short, stocky forelegs and massive paws
0:02:22 > 0:02:24'help get a good grip,
0:02:24 > 0:02:26'while their long back legs give them
0:02:26 > 0:02:28'a spring in their step for launching an attack.
0:02:28 > 0:02:32'The long, furry tail stores fat, and crucially,
0:02:32 > 0:02:34'helps with balance as they flow over the slopes.
0:02:35 > 0:02:37'They might be at home here,
0:02:37 > 0:02:41'but it's hard work for me, trekking at this altitude.
0:02:41 > 0:02:42'You have to watch your step.
0:02:44 > 0:02:47'As the locals here in Bhutan know all too well.
0:02:47 > 0:02:50'A wild sheep has been killed just behind their house.'
0:02:50 > 0:02:53Could you show me where this happened,
0:02:53 > 0:02:55and maybe if there is any sign there?
0:03:00 > 0:03:03- He's going to show us the spot.- OK.
0:03:09 > 0:03:10Wow!
0:03:10 > 0:03:14OK. This is all rather unpleasant.
0:03:14 > 0:03:15Very, very strong smell.
0:03:15 > 0:03:18It's still, from the waist up, very much intact.
0:03:19 > 0:03:23It's just eaten the back half, and most of the rest of it is gone.
0:03:26 > 0:03:30'This big cat may be beautiful, but it's also deadly.
0:03:30 > 0:03:33'They can take down prey four times their size.
0:03:33 > 0:03:37'They stalk into position, then ambush from above.
0:03:37 > 0:03:40'Leaping up to 14 metres,
0:03:40 > 0:03:43'they'll chase their prey down almost vertical cliffs.
0:03:46 > 0:03:49'They kill by biting the neck,
0:03:49 > 0:03:52'and drag their prey to a safe place to eat it.
0:03:54 > 0:03:59'The snow leopard makes life on the edge look effortless.
0:04:01 > 0:04:05'From sheer mountain sides to searing deserts, next at nine.
0:04:06 > 0:04:10'It's a prickly, pointed predator - the spiky thorny devil.
0:04:13 > 0:04:15'Australia's Outback is hot.
0:04:15 > 0:04:19'Seriously hot! And very, very dry.
0:04:19 > 0:04:22'Sometimes, it doesn't rain for years.
0:04:27 > 0:04:31'On walkabout here, I'll need to drink four or five litres of water
0:04:31 > 0:04:32'a day to stay healthy.
0:04:34 > 0:04:37'So how do other animals survive this extreme?
0:04:41 > 0:04:44'Meet the rather weird-looking thorny devil.'
0:04:45 > 0:04:47Now, all these very distinctive
0:04:47 > 0:04:53thorns along its back and its tail are actually modified scales.
0:04:53 > 0:04:55They're quite sharp and pointy,
0:04:55 > 0:04:57and certainly, if a dingo was to get a mouthful of it,
0:04:57 > 0:05:00then it would probably drop it.
0:05:00 > 0:05:03'But aside from being a great defence against predators,
0:05:03 > 0:05:05'this lizard's strange skin actually helps it
0:05:05 > 0:05:07'collect water in this arid land.
0:05:13 > 0:05:17'Thorny devils exclusively eat ants, up to 2,000 in a meal.
0:05:20 > 0:05:24'And licking them up one at a time is pretty thirsty work.
0:05:31 > 0:05:34'Water is a vital resource in the Outback.
0:05:35 > 0:05:38'The thorny devil's scaly skin doesn't sweat...
0:05:39 > 0:05:42'..and instead is covered with a network of thousands
0:05:42 > 0:05:45'of tiny grooves that work like straws,
0:05:45 > 0:05:48'sucking up moisture from the ground.
0:05:54 > 0:05:56'The water creeps between the scales,
0:05:56 > 0:05:58'towards the lizard's waiting dry mouth.
0:06:00 > 0:06:03'This way, the thorny devil can absorb water during rains,
0:06:03 > 0:06:06'catch droplets of dew, and even soak up a drink from damp sand.
0:06:08 > 0:06:11'A pretty clever way of quenching your thirst
0:06:11 > 0:06:12'in an extreme dry desert.
0:06:15 > 0:06:19'Now, you might be surprised that the deadly predator at number eight
0:06:19 > 0:06:21'is a plant.
0:06:21 > 0:06:24'It's the strange carnivorous pitcher plant.
0:06:28 > 0:06:32'This odd-looking family of flora are found in extreme locations where
0:06:32 > 0:06:35'the soil is too poor in minerals, too sandy
0:06:35 > 0:06:37'or acidic for most plants to survive.
0:06:39 > 0:06:42'As they can't get their nutrients from the ground like normal,
0:06:42 > 0:06:45'these plants have developed a deadly strategy.
0:06:45 > 0:06:47'They catch and devour insects.
0:06:48 > 0:06:52'Leaves on the plant swell and grow into pods called pitchers,
0:06:52 > 0:06:54'which, when they open, are often filled
0:06:54 > 0:06:56'with a special, syrupy liquid produced by the plant.
0:06:58 > 0:07:00'Like a deadly swimming pool,
0:07:00 > 0:07:04'creatures that fall in will drown and are digested by the juices.
0:07:04 > 0:07:08'To lure in their prey to a watery grave,
0:07:08 > 0:07:09'the plants are brightly coloured,
0:07:09 > 0:07:12'often sweet-smelling, and ooze nectar
0:07:12 > 0:07:16'from the underside of their lids, all a hit with the locals.
0:07:16 > 0:07:19'But the edges of the pitcher have slippery, waxy sides,
0:07:19 > 0:07:21'a one-way ticket to trouble.
0:07:24 > 0:07:26'Ants don't have armbands,
0:07:26 > 0:07:29'so quickly drown in the plant's predatory puddle.
0:07:29 > 0:07:32'Their bodies decompose into a soup,
0:07:32 > 0:07:35'which is absorbed by the plant, a great source of nutrients
0:07:35 > 0:07:38'that the plant would normally get from the soil.
0:07:38 > 0:07:43'Energy needed to grow yet more deadly pitchers.
0:07:44 > 0:07:47'By developing this carnivorous strategy,
0:07:47 > 0:07:50'pitcher plants can thrive in extreme areas where other plants
0:07:50 > 0:07:53never could, even in mid-air with no soil at all.
0:07:55 > 0:07:56'Fantastically fatal flora!
0:07:58 > 0:08:00'So, three down,
0:08:00 > 0:08:02'and we've already seen some extreme survivors.
0:08:02 > 0:08:05'The mountaineering snow leopard,
0:08:05 > 0:08:07'the sucking skin of the thorny devil,
0:08:07 > 0:08:10'and the rather ravenous pitcher plants.
0:08:10 > 0:08:12'As we count down the list,
0:08:12 > 0:08:15'what could beat these three to number seven?
0:08:16 > 0:08:19'Take a deep breath, because it's an odd-looking,
0:08:19 > 0:08:20'swampy river monster.
0:08:21 > 0:08:23'It's the lungfish.
0:08:25 > 0:08:27'These eel-like predators
0:08:27 > 0:08:29'have evolved to be perfectly adapted to life
0:08:29 > 0:08:32'in stagnant, boggy lakes and marshes.
0:08:32 > 0:08:33'They're well camouflaged,
0:08:33 > 0:08:36'but I'm hoping we'll catch one here in the shallows.'
0:08:39 > 0:08:43My friend here has managed to net me a lungfish.
0:08:43 > 0:08:47Now, most fish would really object to being treated like this,
0:08:47 > 0:08:49but the clue to why this one is actually doing OK
0:08:49 > 0:08:51is in the name, lungfish.
0:08:51 > 0:08:55It not only has gills here for breathing in the water,
0:08:55 > 0:08:56but it also has lungs.
0:08:56 > 0:08:59So, that gulping sound you can hear there
0:08:59 > 0:09:01is it breathing oxygen in the air.
0:09:04 > 0:09:06One of the most unusual things about the lungfish
0:09:06 > 0:09:08is what happens if all this water dries up.
0:09:10 > 0:09:14'Lungfish have evolved to cope with the most extreme environment
0:09:14 > 0:09:16'for any fish. Drought.
0:09:16 > 0:09:20'In parts of Africa, a lack of rainfall means that
0:09:20 > 0:09:23'swamps and rivers can dry up completely.
0:09:23 > 0:09:24'This means certain death for most
0:09:24 > 0:09:26'aquatic animals, but the lungfish has a plan.
0:09:33 > 0:09:38'It burrows down into the mud, using its mouth to excavate a chamber.
0:09:38 > 0:09:42'Overhead, the mud dries hard, almost like concrete.
0:09:44 > 0:09:49'But inside its burrow, the lungfish exudes a thick, slimy covering
0:09:49 > 0:09:54'that dries hard around it, forming a waterproof, protective cocoon.
0:09:54 > 0:09:57'Mummified this way, it can survive for months,
0:09:57 > 0:10:00'or even up to four years, entombed in mud.
0:10:00 > 0:10:03'Some lungfish have even found themselves
0:10:03 > 0:10:06'incorporated into mud brick houses.
0:10:08 > 0:10:10'The lungfish stays alive by breathing air
0:10:10 > 0:10:15'and slowing its metabolism to one 60th of its normal rate.
0:10:16 > 0:10:20'It barely moves, and looks as if it's dead,
0:10:20 > 0:10:23'but it holds out until the rains come.
0:10:34 > 0:10:37'At the first sign of moisture, the lungfish begins to stir.
0:10:39 > 0:10:43'Its slime cocoon and muddy burrow soften in the rain.
0:10:43 > 0:10:47'The fish seems to come back to life and slithers straight for the water.
0:10:48 > 0:10:52'Due to its slimy shutdown technique and ability to breathe air,
0:10:52 > 0:10:54'the lungfish can survive the most extreme droughts.
0:10:56 > 0:10:58'A fish out of water? No problem!
0:11:00 > 0:11:03'Next, at six, are some creatures who survive
0:11:03 > 0:11:05'and thrive in constant darkness.'
0:11:08 > 0:11:10'Good to go, Steve. We're good to go. Over'
0:11:11 > 0:11:16'Caves are dark, damp and generally inhospitable places.'
0:11:18 > 0:11:21Up in the roof of the cave, with the bats and the birds
0:11:21 > 0:11:25circling around you, it's kind of like paradise.
0:11:25 > 0:11:27And down here is a kind of hell.
0:11:27 > 0:11:31But there are some deadly creatures that absolutely love it.
0:11:34 > 0:11:38'It's home to bats, bugs and weird, scuttling creepy crawlies.'
0:11:41 > 0:11:45This, possibly, is one of the nastiest places on the planet.
0:11:45 > 0:11:49'Caves are extreme environments, as food is hard to come by.'
0:11:51 > 0:11:53STEVE LAUGHS
0:11:53 > 0:11:55That one just ran over my hand!
0:11:55 > 0:11:57'Anything that lives here has to know how to survive
0:11:57 > 0:11:59'or hunt in pitch darkness.
0:12:07 > 0:12:10'The tiny starlights in the roof of this cave in New Zealand
0:12:10 > 0:12:14'might look lovely, but they are, in fact, the lethal lures...
0:12:15 > 0:12:17'..of the fungus gnat glow worm.
0:12:20 > 0:12:23'To try and catch a meal in this harsh cave environment,
0:12:23 > 0:12:26'the fungus gnat larvae employ a clever hunting technique.
0:12:28 > 0:12:30'They hang sticky threads of mucus-covered silk
0:12:30 > 0:12:33'from the ceiling, like a three-dimensional web.
0:12:33 > 0:12:37'In the still air of the cave, each gnat larva can manufacture
0:12:37 > 0:12:40'up to 70 separate strands of silk,
0:12:40 > 0:12:43'producing a dense curtain of snares that hang down
0:12:43 > 0:12:46'like beautiful, beaded chandeliers.
0:12:46 > 0:12:49'Belching beads of gluey mucus onto each strand of silk
0:12:49 > 0:12:52'turns them into exquisite lethal weapons.
0:12:52 > 0:12:55'Spinning more filaments maximises the chance
0:12:55 > 0:12:58'of catching a meal, as food is scarce.
0:12:58 > 0:13:02'Each gnat larvae emits a pale blue light
0:13:02 > 0:13:03'from the tip of its abdomen,
0:13:03 > 0:13:07'a chemical beacon that's clearly visible in the surrounding darkness.
0:13:07 > 0:13:11'It proves irresistible to any insects that stray into the cave.
0:13:11 > 0:13:14'Mayflies and midges hatching out of underground streams
0:13:14 > 0:13:18'flutter upwards towards the lights, like moths to a flame.
0:13:18 > 0:13:20'The fungus gnat's snares,
0:13:20 > 0:13:23'invisible from below, are devastatingly efficient.
0:13:24 > 0:13:26'In an extreme place like this,
0:13:26 > 0:13:29'where there isn't much food to go around,
0:13:29 > 0:13:32'a successful hunting strategy is vital.
0:13:32 > 0:13:36'Once caught, the fly's struggles only entangle it further.
0:13:37 > 0:13:40'The larva slowly slimes it way over
0:13:40 > 0:13:44'and begins to winch up its meal, bead by slimy bead.
0:13:48 > 0:13:50'The prey is then sucked dry
0:13:50 > 0:13:53'and chopped up into tiny pieces to be eaten.
0:13:53 > 0:13:55'Not a scrap is wasted.
0:13:55 > 0:13:57'By using silken threads,
0:13:57 > 0:14:01'mouthfuls of mucus and a dazzling tail light,
0:14:01 > 0:14:03'this slimy creature can fish for a living
0:14:03 > 0:14:06'in one of the most extreme cave environments.
0:14:11 > 0:14:15'We're halfway through the countdown,
0:14:15 > 0:14:17'and so far, we've seen a big cat that lives on
0:14:17 > 0:14:19'the toughest mountain slopes,
0:14:19 > 0:14:23'the desert devil's smart skin, carnivorous pitcher plants,
0:14:23 > 0:14:27'a drought-busting lungfish and some fatally attracting glow worms,
0:14:27 > 0:14:31'all brilliantly adapted to survive extreme conditions.
0:14:31 > 0:14:33'So, who could beat them on the list?
0:14:33 > 0:14:36'There's a battle for the number five slot.
0:14:36 > 0:14:38'Two foxes are going head-to-head.
0:14:39 > 0:14:42'It's the arctic fox versus
0:14:42 > 0:14:44'its sandy cousin, the fennec fox.
0:14:45 > 0:14:49'First up is the fennec fox,
0:14:49 > 0:14:52'who survives in the extreme heat of North Africa's deserts,
0:14:52 > 0:14:55'where the daytime temperature can reach 43 degrees.
0:14:57 > 0:14:59'This little fox has some clever adaptations
0:14:59 > 0:15:02'to survive the high temperatures of the Sahara.
0:15:02 > 0:15:04'It spends much of its day in its burrow.
0:15:04 > 0:15:06'The freshly-dug sand is cool
0:15:06 > 0:15:09'and a great place to hide from the piercing sun.
0:15:09 > 0:15:11'It also has giant ears.
0:15:11 > 0:15:15'These are packed full of blood vessels and work like radiators,
0:15:15 > 0:15:16'pumping heat away from the body.
0:15:18 > 0:15:22'No water in the desert is also no problem for the fennec.
0:15:22 > 0:15:25'It fills its diet with juicy grubs
0:15:25 > 0:15:30'and succulent snakes, even if they are quite a mouthful.
0:15:30 > 0:15:34'They rarely need to drink water and never sweat.
0:15:34 > 0:15:38'So, the desert-digging, big-eared, snake-munching fennec fox
0:15:38 > 0:15:41'makes living in extreme deserts look like a walk in the park.
0:15:43 > 0:15:45'How does his northern cousin match up?
0:15:47 > 0:15:51'In the spring, the arctic fox is a lean, mean killing machine.
0:15:51 > 0:15:55'It fills its face with seabird chicks and stores food for later,
0:15:55 > 0:15:58'as the arctic winter is going to be tough.
0:16:04 > 0:16:08'Temperatures plummet to -40, 50 or even 60 degrees.
0:16:09 > 0:16:12'And the arctic fox dresses for the weather,
0:16:12 > 0:16:16'donning a snow suit twice as thick as its spring coat,
0:16:16 > 0:16:18'one of the best insulating furs of any mammal.
0:16:20 > 0:16:23'The arctic fox is quite literally the polar opposite of the fennec,
0:16:23 > 0:16:26'with small ears, short legs
0:16:26 > 0:16:28'and a fat, rounded body for keeping in the heat.
0:16:30 > 0:16:33'Its incredible white fur is its weapon against cold,
0:16:33 > 0:16:35'and by curling up into a ball,
0:16:35 > 0:16:38'its tail acts like a duvet over its face.
0:16:40 > 0:16:43'The fox can keep its body over 50 degrees warmer
0:16:43 > 0:16:46'than the surroundings when snuggled up like this.
0:16:46 > 0:16:49'It has furry feet like snowshoes
0:16:49 > 0:16:53'and special blood vessels in the pads to stop its feet freezing.
0:16:56 > 0:16:58'Food is hard to come by in winter,
0:16:58 > 0:17:02'but the adaptable fox can even survive on scavenged scraps.
0:17:07 > 0:17:10'So, both clever canids are pretty extreme,
0:17:10 > 0:17:13'but which one will take the number 5 slot?
0:17:13 > 0:17:16'For me, it has to be the gorgeous arctic fox,
0:17:16 > 0:17:20'surviving freezing temperatures with its oversized overcoat.
0:17:20 > 0:17:22'A super furry animal!
0:17:25 > 0:17:28'From the polar winter to the desert heat next at 4.
0:17:29 > 0:17:32'It's the spoor spider, the master of the dunes.'
0:17:35 > 0:17:38The sun here in the Namib is utterly scorching.
0:17:38 > 0:17:41It can be a bit like wandering around in a sauna,
0:17:41 > 0:17:43and the sun's rays...
0:17:43 > 0:17:46are soaked up by the surface of the sand,
0:17:46 > 0:17:48which is unbearably hot.
0:17:48 > 0:17:51Mind you, if you dig down...
0:17:51 > 0:17:55just a short way, the sand's still cool.
0:17:55 > 0:17:58There's lots of animals here that use both of these things
0:17:58 > 0:18:00to their advantage. They'll bury down beneath the sand
0:18:00 > 0:18:03to stay cool during the daytime, and they can use the heat
0:18:03 > 0:18:05on the surface of the sand as a weapon.
0:18:05 > 0:18:07Ergh!
0:18:07 > 0:18:10'Our next animal doesn't pose any threat to me.'
0:18:10 > 0:18:11Wait for us!
0:18:11 > 0:18:15'But the same definitely can't be said for the local ant population.'
0:18:15 > 0:18:16Ah!
0:18:19 > 0:18:24We've been looking a lot at tracks and signs of animals,
0:18:24 > 0:18:30and under here is the hiding place of a very special hunter.
0:18:30 > 0:18:31See if we can get it out.
0:18:36 > 0:18:37Wow!
0:18:37 > 0:18:39I think I might have him!
0:18:41 > 0:18:42There he is.
0:18:44 > 0:18:47This is a spoor spider.
0:18:47 > 0:18:50He's only very tiny, but he's a very ferocious
0:18:50 > 0:18:53and really quite clever little hunter.
0:18:54 > 0:18:59The spider uses the heat of the sand to kill its ant prey.
0:19:02 > 0:19:04'Unlike most spiders,
0:19:04 > 0:19:07'the spoor spider spins their web on the ground,
0:19:07 > 0:19:10'carefully weaving together fine grains of sand.
0:19:10 > 0:19:13'They then flip themselves under this silken mat, and protected from
0:19:13 > 0:19:17'the sun, begin to construct a burrow in the cool layers beneath.
0:19:20 > 0:19:22'Our thermal camera shows the difference in temperature.
0:19:24 > 0:19:26'Then... Bang!
0:19:28 > 0:19:30'It rockets up its burrow
0:19:30 > 0:19:33'and grabs the ant with one super-strong leg,
0:19:33 > 0:19:35'clamping it down against the baking hot sand
0:19:35 > 0:19:38'until it actually cooks the ant alive.
0:19:47 > 0:19:51'It then drags the body back into its burrow to be devoured.
0:19:52 > 0:19:56'So by adapting its web to be a sunshield and the perfect ant trap,
0:19:56 > 0:20:00'the spoor spider can take down feisty prey twice its size,
0:20:00 > 0:20:04'using the desert heat to barbecue its meat.
0:20:04 > 0:20:06'The competition is hotting up,
0:20:06 > 0:20:09and if that desert hunter got you in a sweat,
0:20:09 > 0:20:12'the animal at number 3 is super cool.
0:20:12 > 0:20:13'It's the emperor penguin.
0:20:17 > 0:20:20'Surging out of cold, Antarctic waters,
0:20:20 > 0:20:23'emperor penguins are ready to start their breeding season.
0:20:24 > 0:20:27'Males have been hunting at sea, and are glossy and fat with fish.
0:20:29 > 0:20:33'But they need to be as they're setting off
0:20:33 > 0:20:36'for the start of one of the most extreme trials on Earth.
0:20:39 > 0:20:41'They trek up to 100 miles on full stomachs,
0:20:41 > 0:20:45'across the frozen ice, to reach their colony.
0:20:49 > 0:20:51'Hours of painstaking plodding.
0:20:59 > 0:21:02'Here, they pair up with their mates for the season.
0:21:03 > 0:21:08'The female hands over the egg and the tag teams switch places.
0:21:08 > 0:21:11'It's now Daddy Day Care's sole job to keep the egg safe and warm
0:21:11 > 0:21:15'inside his pouch for two months until it hatches.
0:21:15 > 0:21:19'And it's about to get a lot colder. Extremely cold!
0:21:21 > 0:21:23'As the sun drops below the horizon and winter sets in,
0:21:23 > 0:21:26'blizzards drive the temperature down.
0:21:26 > 0:21:29'In order to survive, the males are forced to hunker down,
0:21:29 > 0:21:32'shuffling together into a group for warmth,
0:21:32 > 0:21:34'taking it in turns to be on the edge,
0:21:34 > 0:21:36'being buffeted by the vicious winds.
0:21:38 > 0:21:39'They turn their backs to the gales
0:21:39 > 0:21:42'and tuck their beaks down to conserve warmth.
0:21:42 > 0:21:46'If the huddle breaks, even for a moment, precious heat escapes.
0:21:50 > 0:21:53'Antarctica is the coldest, windiest place in the world.
0:21:55 > 0:21:57'The air temperature can drop to -60,
0:21:57 > 0:22:00'with winds of up to 120 miles an hour.
0:22:08 > 0:22:11'By the end of the winter, the male
0:22:11 > 0:22:14'hasn't eaten a thing for four months.
0:22:14 > 0:22:16'Not only has he survived the coldest, darkest winter
0:22:16 > 0:22:19'on the planet and lost around 45%
0:22:19 > 0:22:22'of his body weight, but he still has the energy
0:22:22 > 0:22:25'to provide the tiny chick with a mouthful of vital food.
0:22:31 > 0:22:35'And surviving this extreme is all worth it,
0:22:35 > 0:22:37'so the chicks are born early enough in the season that
0:22:37 > 0:22:40'they can grow big and strong before they head out to sea to hunt.
0:22:47 > 0:22:49'So what can be more extreme than
0:22:49 > 0:22:52'surviving the coldest, darkest winter on earth?
0:22:52 > 0:22:56'In at 2 is the largest toothed hunter in the world,
0:22:56 > 0:22:57'the sperm whale.
0:22:57 > 0:23:02'This giant stalks its prey in the mysterious depths of the oceans.
0:23:03 > 0:23:07'Big males can be 20 metres long and weigh 45 tonnes.
0:23:07 > 0:23:10'That's about as heavy as six elephants!
0:23:10 > 0:23:13'And big animals have big appetites.
0:23:13 > 0:23:16'A sperm whale needs to eat a tonne of food every day.
0:23:16 > 0:23:19'But the reason why the sperm whale is so extreme
0:23:19 > 0:23:22'is that its dinner lives over a mile down,
0:23:22 > 0:23:25'in the crushing, pitch black of the deep sea.
0:23:25 > 0:23:28'It's the deepest-diving of all mammals.
0:23:29 > 0:23:32'Before it submerges, the whale breathes out,
0:23:32 > 0:23:34'a trick to stop its lungs from being damaged
0:23:34 > 0:23:36'under pressure as it dives.
0:23:36 > 0:23:39'Then, with a flick of its massive tail,
0:23:39 > 0:23:41'it descends at 100 metres a minute.
0:23:41 > 0:23:44'It can hold its breath for over an hour.
0:23:44 > 0:23:47'The pressure at a mile down exerts a force
0:23:47 > 0:23:50'the same weight as ten jumbo jets.
0:23:50 > 0:23:53'But the sperm whale's skeleton is designed to bend, not break.
0:23:56 > 0:23:59'Its heartbeat slows to a third of its normal speed.
0:24:00 > 0:24:03'Now, with its body buckled by pressure,
0:24:03 > 0:24:06'no air in its lungs and its heart barely pumping, it starts to hunt...
0:24:09 > 0:24:12'..in complete darkness.
0:24:12 > 0:24:16'The whale uses echolocation to hunt for squid underwater.
0:24:16 > 0:24:18'Like a submarine, he sends out clicks and calls
0:24:18 > 0:24:21'that bounce back to build up a picture of its surroundings.
0:24:23 > 0:24:25'And once it's had its fill,
0:24:25 > 0:24:27'the whale surges to the surface to breathe.
0:24:31 > 0:24:33'By being equipped to go where other mammals can't,
0:24:33 > 0:24:38'the sperm whale gets a rich fishing ground all to itself.
0:24:38 > 0:24:42'Now it's time for a refreshing reminder of the extreme predators
0:24:42 > 0:24:45'we've seen so far in our 10 to 2 countdown.
0:24:45 > 0:24:47'The rock-climbing snow leopard
0:24:47 > 0:24:50'makes crumbly cliffs look cosy at ten.
0:24:50 > 0:24:53'Knobbly 9 is the thirsty thorny devil.
0:24:53 > 0:24:57'Drowning out the competition at 8 are the pitcher plants.
0:24:57 > 0:25:00'Slippery 7 is the slime-covered lungfish.
0:25:01 > 0:25:05'The fatal fairy lights of the glow worm are at 6.
0:25:05 > 0:25:07'Staying alive at 5 is the all-white arctic fox.
0:25:09 > 0:25:12'Our ant-snatching spoor spider is at 4.
0:25:12 > 0:25:15'Weathering the world's worst winter at 3 is the emperor penguin.
0:25:15 > 0:25:19'And diving in at 2 is the phenomenal sperm whale.
0:25:19 > 0:25:22'So, what on earth is going to top all of that
0:25:22 > 0:25:25'to the number 1 in my Deadly Top 10 Extreme?
0:25:25 > 0:25:27'It's the wood frog, and trust me,
0:25:27 > 0:25:29'they have the ultimate survival strategy.
0:25:31 > 0:25:35'The wood frog lives in North America where the winters are harsh.
0:25:36 > 0:25:38'Its range even stretches up into Alaska,
0:25:38 > 0:25:42'further north than any other frog.
0:25:42 > 0:25:45'Cold-blooded creatures struggle to survive in cold weather,
0:25:45 > 0:25:49'so this frog takes extreme survival to another level.
0:25:49 > 0:25:52'When the winter temperature starts to drop,
0:25:52 > 0:25:55'the wood frog takes refuge underground.
0:25:58 > 0:26:00'As it gets colder still,
0:26:00 > 0:26:02'the icy frost penetrates the soil,
0:26:02 > 0:26:06'and being cold-blooded, our toad-in-the-hole starts to freeze.'
0:26:12 > 0:26:13# You're as cold as ice... #
0:26:13 > 0:26:16'The frog uses some clever chemistry to protect itself
0:26:16 > 0:26:20'from spiky, dagger-like ice crystals damaging its insides.
0:26:20 > 0:26:25'It packs its cells with sugars, which work like antifreeze.
0:26:25 > 0:26:28'Using glucose is a pretty sweet trick,
0:26:28 > 0:26:31'as it prevents the frog's cells from being destroyed
0:26:31 > 0:26:34'by ice crystals, which form between the cells
0:26:34 > 0:26:35'and in the bloodstream instead.
0:26:41 > 0:26:44'With no breathing, no movement and even no heartbeat,
0:26:44 > 0:26:47'the frog should be dead.
0:26:47 > 0:26:50'But the sugars stored in its body provide just enough energy
0:26:50 > 0:26:53'to keep the cells alive through the deepest part of the winter.
0:26:53 > 0:26:57'Frozen in time, this incredible frog can survive
0:26:57 > 0:27:01'as an ice pop with 65% of its body frozen solid
0:27:01 > 0:27:03'for up to four weeks.
0:27:03 > 0:27:06'But even with all its vital functions on hold,
0:27:06 > 0:27:09'there is life in the old frog yet!
0:27:10 > 0:27:13'When spring arrives and the temperatures start to rise,
0:27:13 > 0:27:15'the frog's body begins to thaw.
0:27:19 > 0:27:22'The de-frosted heart muscle is kick-started
0:27:22 > 0:27:24'back into action, and blood
0:27:24 > 0:27:26'starts pumping around the body.
0:27:26 > 0:27:29'The once-frozen frog is almost completely back to normal
0:27:29 > 0:27:30'within 24 hours...'
0:27:33 > 0:27:35# I'm a survivor
0:27:35 > 0:27:36# I'm not gon' give up
0:27:36 > 0:27:38# I'm not gon' stop
0:27:38 > 0:27:39# I'm gon' work harder
0:27:39 > 0:27:40# Keep on surviving. #
0:27:42 > 0:27:46'..And hops to it, taking advantage of being the only frog in town!
0:27:47 > 0:27:50'So, that's my Deadly Top 10 Extreme done!
0:27:54 > 0:27:57'Don't forget to join me next time for more Deadly Top 10s.
0:27:59 > 0:28:02'Who's going to be the next Deadly number 1?'
0:28:08 > 0:28:11Subtitles by Red Bee Media Ltd