0:01:17 > 0:01:20Water - hundreds of thousands of tons of it,
0:01:20 > 0:01:23lying frozen on the mountains of the world.
0:01:23 > 0:01:28It covers not only the poles, but caps great peaks on the equator.
0:01:38 > 0:01:42Water molecules, distilled from the sea by the heat of the sun,
0:01:42 > 0:01:43condense in the sky.
0:01:43 > 0:01:46As they fall gently through the air, they pack together into shapes
0:01:46 > 0:01:52that echo their six-fold symmetry and form infinitely varied crystals of ice.
0:01:54 > 0:01:59They settle on the high mountains and compact into snow and ice
0:01:59 > 0:02:01that is, chemically, almost pure water,
0:02:01 > 0:02:05much purer than the sea from which most of it came.
0:02:05 > 0:02:08On Mount Rainier in the western United States,
0:02:08 > 0:02:11permanent snow begins at 7,000 feet.
0:02:11 > 0:02:18You might think that this was one of the most inhospitable places on Earth for life.
0:02:18 > 0:02:22After all, no vegetation grows on these snowfields,
0:02:22 > 0:02:29so there can be no animals that feed on it, like marmots or mice or rabbits,
0:02:29 > 0:02:33and if there are no herbivores, there can't be any carnivores, any predators
0:02:33 > 0:02:35like hawks or weasels.
0:02:35 > 0:02:41But in fact, there is a surprising amount of life here.
0:02:41 > 0:02:47There is some life actually within this snowfield itself,
0:02:47 > 0:02:52because this snow is not white, but red.
0:02:53 > 0:02:58The colour comes from microscopic plants - algae.
0:02:58 > 0:03:01The redness is produced by light reflected from their cell walls,
0:03:01 > 0:03:06and is almost invisible when, under the microscope, light shines through them.
0:03:06 > 0:03:09Internally, they're green with chlorophyll.
0:03:09 > 0:03:13With its aid, they use the sun's energy to convert carbon dioxide and water
0:03:13 > 0:03:15into sugars.
0:03:15 > 0:03:18And these, together with the minerals dissolved in the melt water,
0:03:18 > 0:03:21are all the algae need to grow and reproduce.
0:03:21 > 0:03:24The heavy falls of winter snow will bury them feet deep,
0:03:24 > 0:03:30but in spring, when the surface melts, they divide, develop tiny beating hairs,
0:03:30 > 0:03:33and swim up to the surface in the sunshine.
0:03:33 > 0:03:37As they age, and the minerals are used up, they change colour,
0:03:37 > 0:03:42forming huge smears of red in snowfields all over the world.
0:03:48 > 0:03:52Eventually, the snow algae produce spores as fine as dust
0:03:52 > 0:03:56and in that form they are blown from one snowfield to another.
0:03:56 > 0:04:00But other, bigger animals, also brought up by the wind,
0:04:00 > 0:04:03and blow across the snows of Mount Rainier.
0:04:09 > 0:04:12Ladybirds. Thousands of them.
0:04:12 > 0:04:17Nobody knows why they come up in such numbers and assemble like this.
0:04:17 > 0:04:23But in late summer they fly up from the valleys up to these high peaks
0:04:23 > 0:04:26and here assemble in the rocks.
0:04:26 > 0:04:29When the winter snows come, the ladybirds remain underneath
0:04:29 > 0:04:31the snow in the rocks,
0:04:31 > 0:04:37and then in the spring, as now, the snow melts and the sun warms the ladybirds,
0:04:37 > 0:04:42and they become active and fly off back to the valley to feed on aphids.
0:04:45 > 0:04:50The ladybirds are only temporary residents of the Mount Rainier snowfields.
0:04:50 > 0:04:52Other insects manage, almost unbelievably,
0:04:52 > 0:04:57to live all their lives in this seemingly inhospitable snow.
0:04:57 > 0:04:59The best time to find them is at night.
0:05:22 > 0:05:25A whole community lives here,
0:05:25 > 0:05:30feeding on pollen grains and the bodies of dead insects blown up on the wind.
0:05:31 > 0:05:35Some, like this primitive relation of the cockroach, a grylloblattid,
0:05:35 > 0:05:39have a body chemistry so well adjusted to function at low temperatures
0:05:39 > 0:05:43that if you pick them up, your hand's warmth will kill them.
0:05:50 > 0:05:53Permanent snow lies directly on bare rock,
0:05:53 > 0:05:57but lower down, where it comes and goes, there can be a little vegetation
0:05:57 > 0:05:58to be grazed.
0:06:02 > 0:06:05Mountain sheep. These on Mount McKinley are the kind
0:06:05 > 0:06:07known as Dall sheep.
0:06:19 > 0:06:21Little ground squirrels live up here too.
0:06:21 > 0:06:25Unlike the sheep, which retreat to lower altitudes in winter,
0:06:25 > 0:06:27the squirrels are permanent residents,
0:06:27 > 0:06:31insulated in their burrows from the frosts by the cover of snow.
0:06:41 > 0:06:44There are sheep like these in mountains all through North America,
0:06:44 > 0:06:45Asia and Europe.
0:06:45 > 0:06:49They all carry big horns, and all the senior males, in autumn,
0:06:49 > 0:06:52indulge in the most alarming courtship battles.
0:07:35 > 0:07:39It's net easy for plants to grow on steep, high slopes
0:07:39 > 0:07:43The warming by day and freezing by night makes the gravelly soil slip
0:07:43 > 0:07:47downwards, so it's difficult for plants to keep a hold.
0:07:47 > 0:07:49With few plants, grazing animals are rare,
0:07:49 > 0:07:53though there may be more than there appear to be at first sight.
0:07:58 > 0:08:01These, in the Himalayas, are blue sheep,
0:08:01 > 0:08:06so nimble and sure-footed they simply able to reach almost any vegetation on
0:08:06 > 0:08:07the steep slopes.
0:08:13 > 0:08:18But if these are rare, rarer still is the animal that preys on them,
0:08:18 > 0:08:20the snow leopard.
0:08:27 > 0:08:31During the summer it stays high, at between 12,000 and 15,000 feet,
0:08:31 > 0:08:35hunting small rodents and birds as well as mountain sheep.
0:08:55 > 0:08:59Snow leopards have been seen as high as 18,000 feet in summer.
0:08:59 > 0:09:04But when winter comes and there are heavy falls of snow, it retreats to the valleys.
0:09:13 > 0:09:17Game is now so scarce that there's barely enough in even a large valley
0:09:17 > 0:09:20to support more than one leopard,
0:09:20 > 0:09:22so this animal hunts alone.
0:09:29 > 0:09:32Its thick, dense fur is now paler.
0:09:32 > 0:09:36It has a thick, woolly undercoat and cushions of hair under its paws
0:09:36 > 0:09:39which prevent it from sinking in the snow.
0:09:50 > 0:09:53The mountains of Africa, even though they so close to the equator,
0:09:53 > 0:09:56are permanently capped by snow.
0:09:56 > 0:10:00Kilimanjaro, 19,000 feet high, is a volcano.
0:10:00 > 0:10:06Mount Kenya, also volcanic, is 2,000 feet lower but still has its own glaciers
0:10:06 > 0:10:09Each has its own animals and plants
0:10:09 > 0:10:13specially adapted to life at low temperatures.
0:10:13 > 0:10:19And here, at about 13,000 feet, grow some most beautiful and dramatic plants.
0:10:19 > 0:10:22Giant groundsels and giant lobelias.
0:10:22 > 0:10:24At these altitudes, plants like these
0:10:24 > 0:10:29have to face two totally conflicting problems every 24 hours.
0:10:29 > 0:10:34Every night the temperature falls so low that they're in danger of freezing solid.
0:10:34 > 0:10:39And every day the sun rises and beats down so strongly in this very thin air
0:10:39 > 0:10:44that it threatens to warm them up and rob them of their moisture by evaporation.
0:10:44 > 0:10:48But look how this lobelia deals with those problems.
0:10:48 > 0:10:53This little pond of water in the leaf rosette freezes over every night,
0:10:53 > 0:10:58and this shield of ice prevents the water beneath from freezing,
0:10:58 > 0:11:02so that it acts as a liquid jacket, preventing the frost from reaching
0:11:02 > 0:11:04the heart of the plant.
0:11:04 > 0:11:08But then, as the day wears on, there comes the other problem.
0:11:08 > 0:11:11As it gets warmer, this water is in danger of
0:11:11 > 0:11:15evaporating and the plant of losing its night-time insulation.
0:11:15 > 0:11:20But it isn't just rainwater that's accumulated in this rosette of the plant.
0:11:20 > 0:11:24It's been secreted by the plant itself and it's slightly slimy.
0:11:24 > 0:11:29It contains pectin, a colloidal substance which greatly reduces evaporation.
0:11:29 > 0:11:32But there's another kind of lobelia
0:11:32 > 0:11:35which deals with these two problems in a quite different way.
0:11:41 > 0:11:44This one grows very tall and has extremely long leaves,
0:11:44 > 0:11:48each fringed with tiny hairs which acting much the same way as the fur
0:11:48 > 0:11:53of an animal, trapping air between them, so that they insulate the stem from chills.
0:11:53 > 0:11:56They also prevent the wind from robbing the plants of moisture.
0:11:59 > 0:12:02Each group of lobelias is owned by a pair of sunbirds
0:12:02 > 0:12:05which collect the small insects the plants attract.
0:12:05 > 0:12:07They keep themselves warm with fluffed-up feathers.
0:12:09 > 0:12:11And among the rocks are hyrax.
0:12:18 > 0:12:24The reason these little creatures are so tame and I can get so close to them
0:12:24 > 0:12:28as I am, is just because they're living so high up.
0:12:28 > 0:12:32Up here, there are very few creatures to prey on them.
0:12:32 > 0:12:37An occasional leopard may come up and hunt them, but apart from that, nothing.
0:12:37 > 0:12:42And so they can come out during the few brief hours of sunshine
0:12:42 > 0:12:45and bask on the rocks without any fear,
0:12:45 > 0:12:47just as they're doing now.
0:12:51 > 0:12:54Hyrax also live down on the hot plains below,
0:12:54 > 0:13:00but these, in response to the cold, have developed particularly long fur.
0:13:00 > 0:13:04Though you might not think it from their shape, they often climb trees to crop leaves.
0:13:04 > 0:13:08But at these altitudes, there's only grass and lobelias,
0:13:08 > 0:13:11and they share it with the little furry-eared rat.
0:13:19 > 0:13:23Mount Kenya, like its neighbours Kilimanjaro and Ruwenzori,
0:13:23 > 0:13:27is an isolated patch of snow and ice surrounded by the baking hot
0:13:27 > 0:13:28African plains.
0:13:30 > 0:13:31But the great mountains of South America,
0:13:31 > 0:13:36like Cotopaxi, 19,000 feet high, are very different.
0:13:36 > 0:13:41These volcanoes, some active, some dormant, are not isolated peaks
0:13:41 > 0:13:46but part of a continuous range that runs the whole length of the continent
0:13:46 > 0:13:50and is surrounded by the high, cold plains of the Altiplano,
0:13:50 > 0:13:55so their flanks support a large and varied population of animals,
0:13:55 > 0:14:00all adapted to life at high altitudes and low temperatures.
0:14:00 > 0:14:04Here lives a wild South American camel, the vicuna.
0:14:04 > 0:14:08Its coat is fine and silky and protected so effectively from the cold,
0:14:08 > 0:14:12that it has, paradoxically, led to its near-extinction.
0:14:12 > 0:14:17Men have recognised that vicuna wool has an unexcelled softness and warmth
0:14:17 > 0:14:21and hunted the animal for it until it's close to extinction.
0:14:27 > 0:14:31The people of the Andes have domesticated another wild camel,
0:14:31 > 0:14:32the guanaco,
0:14:32 > 0:14:36to produce heavy-fleeced versions which not only produce excellent wool
0:14:36 > 0:14:38but serve as beasts of burden.
0:14:38 > 0:14:43Here, in Ecuador and Peru, close to the equator, wild camels live at
0:14:43 > 0:14:45around 14,000 feet.
0:14:46 > 0:14:52But as you travel south down the range of the Andes, the snowline gets lower.
0:14:52 > 0:14:55Half-way down, 2,000 miles south of Cotopaxi,
0:14:55 > 0:15:01the line of permanent snow has dropped from 16,000 feet to 13,000 feet.
0:15:03 > 0:15:07A thousand miles farther south still, the mountains are not nearly so high
0:15:07 > 0:15:11but are almost completely covered with snow, which comes down to
0:15:11 > 0:15:13within a few hundred feet of the sea.
0:15:15 > 0:15:18So, on the southernmost tip of South America,
0:15:18 > 0:15:20in Patagonia and Tierra del Fuego,
0:15:20 > 0:15:25the guanaco doesn't live at great altitudes, but almost at sea level.
0:15:25 > 0:15:32Yet it needs its warm coat just as much, for here, even in summer, it's very cold,
0:15:32 > 0:15:35and during the winter the whole land is snowbound.
0:15:48 > 0:15:53The reason that it gets colder as we get closer to the pole is not complicated.
0:15:53 > 0:15:58Rays from the sun strike the Earth at the equator at right angles.
0:15:58 > 0:16:00But as you travel round the curve of the Earth,
0:16:00 > 0:16:03the rays become more and more glancing.
0:16:04 > 0:16:07So a given amount of heat falling on the equator
0:16:07 > 0:16:11is distributed over a very much greater area in the polar regions
0:16:11 > 0:16:14and has to travel through more of the Earth's atmosphere,
0:16:14 > 0:16:17which weakens it still further.
0:16:18 > 0:16:23So down in Patagonia, the sun's rays are very much less intense and carry
0:16:23 > 0:16:27much less heat, and the glaciers flow right down to the sea.
0:16:40 > 0:16:44Farther south still, across the near-frozen seas off Cape Horn,
0:16:44 > 0:16:47you reach chains of small volcanic islands
0:16:47 > 0:16:51that run down towards the Antarctic continent itself.
0:16:51 > 0:16:53Remote, little-known archipelagos
0:16:53 > 0:16:57such as the South Sandwich and, here, the South Orkneys.
0:16:59 > 0:17:04There are only two flowering plants that can manage to survive
0:17:04 > 0:17:06in this bleak, icy country.
0:17:06 > 0:17:12One is a kind of thrift and the other is a small, stunted grass.
0:17:12 > 0:17:17And apparently, no land-living animals of any kind.
0:17:17 > 0:17:22But when the snows melt in summer, they reveal that the rocks and
0:17:22 > 0:17:27the boulders are covered with more than 100 different kinds of mosses and lichens,
0:17:27 > 0:17:31some of them rounded green cushions, others like miniature trees.
0:17:33 > 0:17:38The capacity of these simple plants to endure cold is phenomenal.
0:17:38 > 0:17:42Some species can even survive being frozen solid for weeks on end.
0:17:48 > 0:17:54Within this miniature tangled jungle lives a whole menagerie of tiny animals.
0:17:56 > 0:17:58Primitive creatures little bigger than pinheads
0:17:58 > 0:18:03manage to survive by slowly chewing away at the lichens and mosses
0:18:03 > 0:18:04during summer.
0:18:04 > 0:18:06In winter they almost grind to a halt,
0:18:06 > 0:18:12yet they survive unfrozen because their blood contains a kind of antifreeze
0:18:12 > 0:18:16and remains liquid even when the temperature falls well below zero.
0:18:21 > 0:18:26The majority are vegetarians, but there are also carnivorous mites among them
0:18:26 > 0:18:28which clamber around the grazing herds,
0:18:28 > 0:18:31picking off individuals as they fancy.
0:18:33 > 0:18:37In this extreme cold, the processes of life are greatly slowed down,
0:18:37 > 0:18:42not only those of growth, but those that lead to old age and death.
0:18:42 > 0:18:46So such tiny creatures as these, which elsewhere might live for merely months,
0:18:46 > 0:18:50survive for two or three years within the green mossy carpets.
0:18:53 > 0:18:57The seas around these Antarctic islands are strewn with ice.
0:18:57 > 0:19:01The pack ice that litters the surface is frozen sea water,
0:19:01 > 0:19:04and in winter forms a solid cover to the sea.
0:19:04 > 0:19:06The icebergs are different.
0:19:06 > 0:19:09They're made of fresh water and have broken away from glaciers flowing
0:19:09 > 0:19:11into the sea.
0:19:12 > 0:19:16And this is the source of those bergs - the edge of a glacier.
0:19:18 > 0:19:21Beyond it, the continent of Antarctica.
0:19:23 > 0:19:25It's huge, bigger than the whole of Europe,
0:19:25 > 0:19:29and, for the most part, it seems totally devoid of life.
0:19:32 > 0:19:36But not all of Antarctica is covered by snow and ice.
0:19:36 > 0:19:41In parts of the interior there are valleys where almost no snow ever falls.
0:19:42 > 0:19:46This is as desolate a part of the Earth as exists.
0:19:46 > 0:19:51The cold is extreme, it's drier even than the centre of the Sahara,
0:19:51 > 0:19:53it's dark for half the year
0:19:53 > 0:19:58and it's scoured by a never-ending, howling wind.
0:19:59 > 0:20:03And the wind is responsible for these carvings in the solid granite.
0:20:03 > 0:20:07Crystals of salt form beneath tiny flakes on the surface,
0:20:07 > 0:20:12and grow slowly, but so powerfully that particles are broken loose.
0:20:12 > 0:20:15The wind then sweeps them up and hurls them at the rock face,
0:20:15 > 0:20:17eroding it still further.
0:20:21 > 0:20:26Desolate though this waste of shattered rocks may seem, there is life even here.
0:20:34 > 0:20:39Algae. Beneath the stone, the wind doesn't dry it out,
0:20:39 > 0:20:41and it's protected from the worst of the cold.
0:20:41 > 0:20:45It gets the light it needs to grow through the translucent rock.
0:20:52 > 0:20:55There are also green patches actually within the rock.
0:20:55 > 0:21:00Algae have penetrated the microscopic spaces between the rock's constituent particles
0:21:00 > 0:21:02and there managed to grow.
0:21:04 > 0:21:07Glaciers flow down these dry valleys,
0:21:07 > 0:21:11fed by the ice cap that covers the centre of the continent.
0:21:11 > 0:21:15They're among the world's fastest moving, advancing as much as
0:21:15 > 0:21:17300 feet in a year.
0:21:17 > 0:21:23As they surge downwards, their surface is torn into thousands of crevasses.
0:21:39 > 0:21:42During the summer, even though the winds are bitterly cold,
0:21:42 > 0:21:46the sun is sufficiently strong to melt a little of the glacier's surface.
0:21:48 > 0:21:52Where it accumulates in pools, blue-green algae grows vigorously,
0:21:52 > 0:21:57its dark colour enabling it to absorb a high proportion of the sun's feeble heat.
0:22:01 > 0:22:06These pools and streams are the only places in all of Antarctica's interior
0:22:06 > 0:22:09where life flourishes in any abundance.
0:22:10 > 0:22:14The Earth, right at the beginning of the history of life
0:22:14 > 0:22:17before any higher plants or any animals had appeared,
0:22:17 > 0:22:20must have looked something like this.
0:22:25 > 0:22:31Yet here, mysteriously, lie the corpses of large animals.
0:22:31 > 0:22:34A crab-eater seal. It looks comparatively fresh,
0:22:34 > 0:22:40but examination of its tissues show that it is about 300 years old.
0:22:40 > 0:22:43This extreme climate has freeze-dried it.
0:22:43 > 0:22:46It must have lost its way, perhaps because of sickness,
0:22:46 > 0:22:50and misguidedly crawled up here from the coast, 25 miles away.
0:22:52 > 0:22:56Although the land of the Antarctic is almost sterile,
0:22:56 > 0:22:58its waters are extremely fertile,
0:22:58 > 0:23:04so its margins, particularly the beaches of its off-shore islands, are rich in life.
0:23:13 > 0:23:17These fur seals in South Georgia flourish in great numbers
0:23:17 > 0:23:19because the surface waters of the seas
0:23:19 > 0:23:25are thick with shoals of floating shrimp - krill, which is their main food.
0:23:25 > 0:23:29Every year they come ashore to the beaches to pup and mate.
0:23:32 > 0:23:35They're not true seals but are technically called eared seals,
0:23:35 > 0:23:37for they have small external ears.
0:23:37 > 0:23:41They also have hind flippers that can be brought forward, which enables
0:23:41 > 0:23:45them to move quite fast on land, something that true seals can't do.
0:23:45 > 0:23:49These fur seals retained the fur of their land-living ancestors,
0:23:49 > 0:23:50and indeed they thickened it.
0:23:50 > 0:23:55So that now some of these big males have manes on them which give them
0:23:55 > 0:23:59that other name of sea lion.
0:23:59 > 0:24:02This fur lies in two layers.
0:24:02 > 0:24:07There's an outer guard hair and then there is a very thick layer close to the skin,
0:24:07 > 0:24:12and that traps air in it, so it acts as an insulator and keeps the animals warm
0:24:12 > 0:24:14when they go swimming.
0:24:14 > 0:24:16But the trouble with fur as an insulator
0:24:16 > 0:24:18is that if you dive too deep,
0:24:18 > 0:24:21the pressure of the water will squeeze out the air,
0:24:21 > 0:24:23and then it's no use.
0:24:23 > 0:24:28So fur seals, for the most part, fish in the surface waters.
0:24:30 > 0:24:34True seals, like these pups of the elephant seal, have a different kind
0:24:34 > 0:24:37of insulation. Their fur on their body is sparse,
0:24:37 > 0:24:41but beneath the skin they have a thick layer of oily fat, blubber,
0:24:41 > 0:24:44which surrounds their entire body.
0:24:44 > 0:24:47Elephant seals dive to great depths to hunt squid,
0:24:47 > 0:24:51finding their way in the dark with sonar helping their huge eyes,
0:24:51 > 0:24:57but they don't get chilled, for pressure has no effect on the insulating qualities of blubber.
0:24:57 > 0:25:01With every year, the blubber which kept them so warm
0:25:01 > 0:25:04in the freezing seas loses its power.
0:25:04 > 0:25:08Because every year the sea elephants have to moult,
0:25:08 > 0:25:11and in order to grow new skin they have to bring
0:25:11 > 0:25:14a blood supply close to the surface.
0:25:14 > 0:25:17So blood vessels open up through the blubber
0:25:17 > 0:25:21and the skin is flushed with blood just below the surface.
0:25:21 > 0:25:25If they stayed in the sea in that condition, they'd chill very quickly.
0:25:25 > 0:25:28But they don't. Instead...
0:25:28 > 0:25:29SEAL GRUNTS
0:25:31 > 0:25:34..they haul themselves up onto the beaches and come up into mud wallows
0:25:34 > 0:25:39like this one. And there, the big old bulls like that one have to
0:25:39 > 0:25:43suppress the feelings of antagonism they felt only a few months ago
0:25:43 > 0:25:48and lie close together with their fellows in the interests of keeping warm.
0:25:55 > 0:25:57These are the biggest of all seals.
0:25:57 > 0:26:01The huge adult males develop a bladder on top of their noses,
0:26:01 > 0:26:03like a kind of trunk.
0:26:07 > 0:26:12But they also justify their name of sea elephant by their immense size.
0:26:12 > 0:26:17The bulls may grow to 20 feet long and weigh three tons.
0:26:26 > 0:26:30If you wanted to pick a creature to symbolise the frozen wastes of the Antarctic,
0:26:30 > 0:26:34you might well choose a creature like this.
0:26:34 > 0:26:37These are macaroni penguins on the island of South Georgia,
0:26:37 > 0:26:42halfway between the southern end of South America and the Antarctic.
0:26:42 > 0:26:44But it seems the original penguins evolved
0:26:44 > 0:26:48not so much in cold climates as in relatively warm ones.
0:26:48 > 0:26:51Even today, there are species of penguins that live on the equator,
0:26:51 > 0:26:54in the Galapagos islands.
0:26:54 > 0:26:58So this dense coat of insulating feathers with a layer of fat beneath it
0:26:58 > 0:27:03was probably originally developed simply to keep them warm in the seas anywhere,
0:27:03 > 0:27:07but it serves them just as well in the freezing Antarctic winds,
0:27:07 > 0:27:10standing on land or on a surging iceberg.
0:27:29 > 0:27:32And they are superb swimmers.
0:27:34 > 0:27:37Not only are they swift and agile through the water,
0:27:37 > 0:27:40when they come in to land through breakers that would smash any boat
0:27:40 > 0:27:43they seem to have the resilience of rubber balls.
0:27:53 > 0:27:56These chinstrap penguins are only a couple of feet high.
0:27:56 > 0:27:59King penguins are half as tall again.
0:27:59 > 0:28:03Large size can be an advantage in cold climates.
0:28:03 > 0:28:04The bigger a body,
0:28:04 > 0:28:08the smaller the surface area of its skin in proportion to its volume.
0:28:08 > 0:28:12So a big penguin retains it's heat better than a smaller one.
0:28:12 > 0:28:15But their great size causes considerable problems in breeding.
0:28:15 > 0:28:19They lay just one egg, which they keep off the freezing ground
0:28:19 > 0:28:24by the ingenious if rather inconvenient method of holding it on top of their feet,
0:28:24 > 0:28:26covered by a fold of feathered skin.
0:28:26 > 0:28:29They keep it here for eight long weeks.
0:28:29 > 0:28:33When it does at last hatch, the chick takes so long to grow to it's full size and independence,
0:28:33 > 0:28:38that they have to feed it for a further ten months
0:28:39 > 0:28:42These king penguins aren't the biggest of all penguins.
0:28:42 > 0:28:46They have a cousin, living farther south, which grows even bigger.
0:28:46 > 0:28:50It, too, has fearsome problems in raising its chicks
0:28:50 > 0:28:53and it solves them in the most dramatic way imaginable.
0:28:53 > 0:28:58They lay their eggs not in spring, but at the end of summer.
0:28:58 > 0:29:02Their breeding grounds are on the permanent sea ice near the coast.
0:29:02 > 0:29:06The females return to the sea after laying to feed,
0:29:06 > 0:29:09and now, as winter sets in, the males are left with the eggs.
0:29:09 > 0:29:12They shuffle back and forth, each with an egg on his feet,
0:29:12 > 0:29:15held carefully above the ice.
0:29:22 > 0:29:25The gales intensify as the winter advances
0:29:25 > 0:29:27and the sun sinks lower.
0:29:29 > 0:29:33In the skies above, the aurora plays.
0:29:33 > 0:29:37The male emperors stoically sit out the months of winter darkness.
0:29:37 > 0:29:42The sea ice can offer them no nest. Not even a scrape of a few pebbles.
0:29:42 > 0:29:47They have nothing to eat, and nothing to do except protect the precious egg
0:29:47 > 0:29:52and prevent it from freezing while the chick slowly forms inside it.
0:29:52 > 0:29:57As the gales intensify, the males huddle together to give one another shelter.
0:29:57 > 0:30:02Then, 65 days after it was laid, the chick begins to hatch.
0:30:20 > 0:30:22The newly-emerged chicks are hungry.
0:30:22 > 0:30:27All the male can provide is a little secretion from his throat and
0:30:27 > 0:30:30long-empty stomach. He's close to starving himself,
0:30:30 > 0:30:34having been sustained only by the layer of fat beneath his skin.
0:30:34 > 0:30:36He's lost a third of his weight.
0:30:39 > 0:30:42But soon after, the female reappears with a full stomach
0:30:42 > 0:30:47and takes the chick onto her feet and gives it its first proper feed.
0:30:47 > 0:30:53From now on the parents will take turns to trek back and forth to the sea,
0:30:53 > 0:30:55bringing food for their youngsters.
0:30:55 > 0:30:57But now, at the end of winter,
0:30:57 > 0:31:00the sea ice has extended far off from the coast,
0:31:00 > 0:31:04and the penguins may have to walk 50 miles to reach open water.
0:31:05 > 0:31:09The adults have a powerful urge to cherish a chick.
0:31:09 > 0:31:12Those that have lost one will try and adopt any that wanders by.
0:31:12 > 0:31:15Others will even incubate pieces of ice.
0:31:27 > 0:31:29Repeatedly, the parent in charge
0:31:29 > 0:31:33manages to find something from the pit of its stomach
0:31:33 > 0:31:35to feed the ever-hungry chick.
0:31:40 > 0:31:43Until the chicks lose their down and get their adult plumage,
0:31:43 > 0:31:47they can't swim and so can't feed for themselves.
0:31:47 > 0:31:52But being so big, they, like the king penguins, take a long time to grow to
0:31:52 > 0:31:56full size, and week after week their parents must make the long march
0:31:56 > 0:31:58to the sea to collect food for them.
0:32:00 > 0:32:04Though the winter is almost over, there is still bad weather.
0:32:04 > 0:32:06Blizzards rage over the ice,
0:32:06 > 0:32:09and the young, who are becoming independent, huddle together in
0:32:09 > 0:32:12groups of their own amongst the parent birds.
0:32:17 > 0:32:21Many of the youngsters haven't got the strength to withstand the cold.
0:32:21 > 0:32:22Many die.
0:32:24 > 0:32:26As the sun rises higher each day,
0:32:26 > 0:32:29the adults guarding the chicks suffer in a different fashion.
0:32:29 > 0:32:33On sunny days they get uncomfortably hot in their insulating blanket of feathers,
0:32:33 > 0:32:36and eat snow in order to cool themselves.
0:32:39 > 0:32:42The chicks still have their downy feathers and still can't swim.
0:32:42 > 0:32:46But ten months after the eggs were first laid the chicks fledge,
0:32:46 > 0:32:50and over the next few weeks, the whole community makes it way down
0:32:50 > 0:32:56to the sea, which now, once more, with the spring break-up of the ice, is close at hand.
0:32:58 > 0:33:02Now, at last, the adults can feed entirely for themselves.
0:33:02 > 0:33:05They've got two months in which to restore their weight
0:33:05 > 0:33:08before they start the whole process over again.
0:33:13 > 0:33:16These birds, at first sight so penguin-like,
0:33:16 > 0:33:19live not near the south pole, but near the north.
0:33:19 > 0:33:24They're not penguins but guillemots, members of the auk family.
0:33:24 > 0:33:28All auks, like penguins, are excellent underwater swimmers.
0:33:28 > 0:33:30They use their wings like flippers, like penguins do.
0:33:30 > 0:33:34But they have not become such specialised swimmers as the penguins,
0:33:34 > 0:33:36for they can still fly.
0:33:36 > 0:33:40These are the guillemots' smaller cousins, the little auk.
0:33:58 > 0:34:02Auks and penguins, similar though they are, are not closely related.
0:34:02 > 0:34:06They've come to resemble one another by adopting a similar lifestyle
0:34:06 > 0:34:08at opposite ends of the Earth.
0:34:12 > 0:34:16Unlike Antarctica, that isolated continent surrounded by sea,
0:34:16 > 0:34:21the Arctic is connected by land to more temperate parts of the world.
0:34:21 > 0:34:25So the land animals of Europe and North America have been able
0:34:25 > 0:34:29to reach it, colonise it, and become adapted to its particular demands.
0:34:32 > 0:34:34Foxes have moved up here.
0:34:34 > 0:34:38The coat of the Arctic fox is lighter than its cousin down south,
0:34:38 > 0:34:40and in winter becomes completely white.
0:34:40 > 0:34:43On land, it feeds on small rodents,
0:34:43 > 0:34:46and on ice floes, it may hope to catch a few birds.
0:34:46 > 0:34:49It's just as well the little auks have kept their powers of flight.
0:35:05 > 0:35:12The ice floes are also the hunting ground of one of the biggest of all carnivores.
0:35:19 > 0:35:21The polar bear.
0:35:22 > 0:35:25This one has killed a bearded seal.
0:35:37 > 0:35:42A young bear is eager to take a share of the kill, but it has to be cautious.
0:35:42 > 0:35:45Adults sometimes kill youngsters in squabbles.
0:36:18 > 0:36:21The polar bear is clearly a close relative of the bears
0:36:21 > 0:36:25that live farther south in Europe and America.
0:36:25 > 0:36:28Its whiteness is an obvious adaptation to the snow and ice,
0:36:28 > 0:36:31but so is its huge size.
0:36:31 > 0:36:34The principle of a big body retaining heat better than a small one,
0:36:34 > 0:36:37applies to bears just as it does to penguins,
0:36:37 > 0:36:40and polar bears are very much bigger
0:36:40 > 0:36:43than their cousins in temperate lands farther south.
0:37:01 > 0:37:04Polar bears, if forced to, will eat all kinds of things
0:37:04 > 0:37:09but their preferred food is flesh, particularly that of seals.
0:37:09 > 0:37:13They especially like the blubber just below the skin of the seal,
0:37:13 > 0:37:17and often leave the meat for the scavenging gulls and foxes.
0:37:17 > 0:37:19GRUNTING
0:37:19 > 0:37:20BIRDS SQUAWK
0:37:23 > 0:37:25LOW GRUNT
0:37:44 > 0:37:49Among the glaucous gulls is the much rarer and pure-white ivory gull.
0:37:58 > 0:38:03The polar bear's white coat and great size are not its only adaptations to
0:38:03 > 0:38:04life in the Arctic.
0:38:04 > 0:38:08It gets a good grip on the ice with long, sharp claws
0:38:08 > 0:38:12and thick hair on the soles, which also makes them excellent paddles
0:38:12 > 0:38:14in the water.
0:38:14 > 0:38:18For the polar bear spends a lot of time swimming during the summer.
0:39:01 > 0:39:03Ringed seals are much hunted by polar bears,
0:39:03 > 0:39:06and when they haul themselves out on the ice,
0:39:06 > 0:39:08they must be constantly on the alert.
0:39:12 > 0:39:16They have to have regular holes in the ice through which they can leave the water,
0:39:16 > 0:39:19or at least stick up their heads in order to breathe.
0:39:24 > 0:39:29A polar bear will wait for many hours, motionless, beside such a hole.
0:39:34 > 0:39:38They also stalk seals that are rash enough to lie out on the ice.
0:39:54 > 0:39:59The polar bear has lost, but about once in every five hunting days,
0:39:59 > 0:40:01it does kill, and that is enough.
0:40:09 > 0:40:15The most powerful and effective hunter of all, however, on the northern ice, is man.
0:40:19 > 0:40:22Eskimo, or Inuit, as they prefer to call themselves,
0:40:22 > 0:40:25came up to the Arctic in very early times.
0:40:25 > 0:40:29Superb hunters, they were able to live for many months in the winter
0:40:29 > 0:40:32on nothing whatever but raw meat.
0:40:32 > 0:40:34THEY SPEAK IN THEIR NATIVE TONGUE
0:40:45 > 0:40:48They were so skilled in the techniques of living out on the ice
0:40:48 > 0:40:50that with nothing more than a knife of bone
0:40:50 > 0:40:54they could make a waterproof house from snow in an hour or so.
0:41:07 > 0:41:10A slab of sea ice made a window.
0:41:11 > 0:41:13CHILD CRIES
0:41:13 > 0:41:14LAUGHTER
0:41:30 > 0:41:34Inside, the igloo was lit with lamps fed by seal blubber.
0:41:34 > 0:41:36Heat from the flame and from their own bodies
0:41:36 > 0:41:39could raise the temperature sufficiently for them
0:41:39 > 0:41:42to remove their heavy clothing and relax.
0:41:56 > 0:42:00It was a life of extraordinary rigour and privation.
0:42:00 > 0:42:03These pictures were taken 20 years ago.
0:42:03 > 0:42:06No Eskimo lives in this way today.
0:42:08 > 0:42:10The poles have not always been so cold.
0:42:10 > 0:42:13One explanation of why they've become so concerns
0:42:13 > 0:42:15the warming effect of ocean currents.
0:42:15 > 0:42:19If they can circulate the waters of the polar seas down towards the equator,
0:42:19 > 0:42:22they would keep them relatively warm.
0:42:22 > 0:42:26And maybe they did so 100 million years ago, when the continents were
0:42:26 > 0:42:27distributed like this.
0:42:27 > 0:42:31But since then, the continents have shifted, the polar seas become more
0:42:31 > 0:42:34enclosed and any such currents interrupted.
0:42:37 > 0:42:40At the other end of the world, during the same period,
0:42:40 > 0:42:45the Antarctic continent drifted south until it came to rest over the south pole.
0:42:45 > 0:42:50There was no way now that ocean currents there could keep that part of the world warm either,
0:42:50 > 0:42:53and so an ice cap formed.
0:42:53 > 0:42:56Once that happened, the whiteness reflected back 90% of the heat
0:42:56 > 0:42:58in the already feeble rays of the sun.
0:42:58 > 0:43:03So ice now covers the whole of Antarctica and the seas of the north pole.
0:43:03 > 0:43:07Over the past million years, there have been other variations,
0:43:07 > 0:43:10probably connected with the varying strength the sun
0:43:10 > 0:43:13and the ice cover has waxed and waned.
0:43:13 > 0:43:16At the moment, fortunately for us, we're in one of the warmer phases,
0:43:16 > 0:43:20but even so, Antarctica is still buried beneath ice a mile thick,
0:43:20 > 0:43:27and in the north, ice and snow extend for 1,000 miles away from the pole.
0:43:48 > 0:43:52Eventually, as you come down the mountain or away from the pole,
0:43:52 > 0:43:58the land becomes warm enough to prevent it being covered by ice and snow throughout the entire year.
0:43:58 > 0:44:03Beyond, the country is bleak enough. Boulders and gravel, rocks
0:44:03 > 0:44:07that have been ground to fragments by the glaciers and pushed in front of them.
0:44:08 > 0:44:14This is the tundra, and it's a land full of strange shapes and patterns.
0:44:14 > 0:44:18Fine muds and sands retain more moisture than coarse gravel,
0:44:18 > 0:44:21so when they freeze, they expand more
0:44:21 > 0:44:24and push the gravel away from the centre to produce
0:44:24 > 0:44:26these geometric shapes.
0:44:26 > 0:44:30A foot or so down, the soil is still frozen, permafrost,
0:44:30 > 0:44:34so the melted water the summer can't soak away and the land is
0:44:34 > 0:44:38covered with bogs and ponds that often lie within the polygonal ridges,
0:44:38 > 0:44:42so that the land looks almost as though it's been cultivated by man.
0:44:46 > 0:44:49In places, the underground ice pushes upwards
0:44:49 > 0:44:52into a mountain called a pingo.
0:44:52 > 0:44:54It looks like a small volcano,
0:44:54 > 0:44:56but instead of hot lava in its heart,
0:44:56 > 0:44:59it has cold, blue ice.
0:45:10 > 0:45:15Even though the ice relaxes its grip for only a mere six or eight weeks in summer,
0:45:15 > 0:45:19a surprising number of plants and animals manage to find
0:45:19 > 0:45:20a permanent home here.
0:45:24 > 0:45:27Small flowering plants keep low,
0:45:27 > 0:45:30for within a few inches of the ground there is little wind
0:45:30 > 0:45:32and the sun's rays can be quite warm.
0:45:40 > 0:45:44One kind of tree manages to live up here in surprisingly large numbers
0:45:44 > 0:45:47by adopting exactly the same policy.
0:45:48 > 0:45:51This is the Arctic willow and it lies flat.
0:45:51 > 0:45:54It grows extremely slowly in these cold temperatures,
0:45:54 > 0:45:57and this one may well be a century or so old,
0:45:57 > 0:45:59as the rings in its tiny trunk would show.
0:46:00 > 0:46:03In shallow burrows in the topsoil
0:46:03 > 0:46:08live the harvesters of this meagre crop of leaves and grass - lemmings.
0:46:11 > 0:46:15During the summer, when there's food about, they breed with astounding speed.
0:46:15 > 0:46:20One female produces five or six babies in a litter, and does so four or five times
0:46:20 > 0:46:25in a single season. So in a few months she may produce 30 young.
0:46:25 > 0:46:29And what is more, the babies grow so quickly that the first to be born in the spring
0:46:29 > 0:46:33can themselves produce young before the winter returns.
0:46:40 > 0:46:44At the peak of summer, all the tundra plants put out their leaves
0:46:44 > 0:46:45and there's lots to eat.
0:46:53 > 0:46:56The swarming hordes of lemmings attract hunters.
0:46:59 > 0:47:00Snowy owls.
0:47:13 > 0:47:16During the summer, lemmings are the owl's main food.
0:47:36 > 0:47:38Abundant though the lemmings are,
0:47:38 > 0:47:41the hunting has not been sufficiently good for this owl.
0:47:41 > 0:47:43She may have laid as many as eight eggs,
0:47:43 > 0:47:45but only one chick has survived.
0:48:01 > 0:48:06As the days lengthen, herds of caribou migrate up from the south.
0:48:06 > 0:48:10Their calves were born early in the season and the herd moves as much as
0:48:10 > 0:48:1215 miles a day.
0:48:12 > 0:48:16They have to keep travelling in order to find enough food to sustain them all.
0:48:45 > 0:48:48They follow the same route each year.
0:48:48 > 0:48:51In places, paths have been worn 18 inches deep
0:48:51 > 0:48:54where the animals have passed, century after century.
0:49:00 > 0:49:03Snow geese fly up, too.
0:49:03 > 0:49:07They've come from as far away as Mexico, 3,000 miles distant,
0:49:07 > 0:49:11to claim a share in summer's brief crop and to breed.
0:49:20 > 0:49:22They exist in two forms.
0:49:22 > 0:49:27Ones with dark feathers on the body, as well as pure-white ones.
0:49:27 > 0:49:30But they're all the same species, and mixed couples are common.
0:49:34 > 0:49:38Soon the tundra is thick with their nests.
0:49:40 > 0:49:45Ptarmigan, now in their dark summer plumage, feed on the willow scrub.
0:49:52 > 0:49:56The caribou take not only willow, but grasses and lichen.
0:50:08 > 0:50:12The first snow geese to arrive and go to nest already have goslings,
0:50:12 > 0:50:14and are foraging as a family.
0:50:23 > 0:50:25Later arrivals are still on the nest,
0:50:25 > 0:50:29and can't leave until the last of their eggs have hatched.
0:50:29 > 0:50:32While they stay there, the first goslings to emerge and their parents
0:50:32 > 0:50:37are plagued by hordes of voracious blood-hungry mosquitoes.
0:50:37 > 0:50:39BUZZING
0:50:52 > 0:50:56From the warming pools, more and more mosquitoes hatch.
0:51:02 > 0:51:05They in turn provide food for the red-necked phalarope,
0:51:05 > 0:51:08and there are plenty to gather.
0:51:08 > 0:51:12A square yard of fresh water here can produce 100,000 insects in a season.
0:51:13 > 0:51:15Now the blackfly larvae,
0:51:15 > 0:51:19that have spent the winter as eggs attached to stones in the shallow pools,
0:51:19 > 0:51:21are also beginning to emerge.
0:51:42 > 0:51:44Activity now is intense,
0:51:44 > 0:51:49for it is light for almost the whole 24 hours of the day.
0:51:51 > 0:51:56But by late August, the snow geese begin to sense the imminence of winter
0:51:56 > 0:51:58and start to head southwards again.
0:52:08 > 0:52:10The caribou, too, come to the end of their grazing,
0:52:10 > 0:52:14and start to plod back across the tundra.
0:52:14 > 0:52:16As they go, they continue to feed,
0:52:16 > 0:52:18building up the reserves of fat they will need
0:52:18 > 0:52:21to sustain themselves through the winter.
0:52:22 > 0:52:24HONKING
0:52:40 > 0:52:44As the weather gets colder and colder, the need to find shelter
0:52:44 > 0:52:49becomes more urgent and the herds may cover 25 miles in a day.
0:53:09 > 0:53:13And then, at last, the returning travellers
0:53:13 > 0:53:15reach the first tall trees.
0:53:15 > 0:53:18It's the beginning of the great coniferous forest
0:53:18 > 0:53:22that lies south of the tundra right round the globe.
0:53:22 > 0:53:25The snow geese will fly on for thousands of miles yet,
0:53:25 > 0:53:29but the caribou have reached their wintering grounds.
0:53:29 > 0:53:31The forest is a sanctuary
0:53:31 > 0:53:35which will protect them from the bitter cold of the coming winter
0:53:35 > 0:53:39and it's here that we shall be coming in the next programme.