1 00:00:33,280 --> 00:00:34,919 The polar winter. 2 00:00:41,600 --> 00:00:44,839 This is the planet at its most hostile. 3 00:00:58,520 --> 00:01:05,119 Those that stay here at this time must face the harshest conditions on Earth. 4 00:01:26,840 --> 00:01:30,079 The high Arctic in late autumn, 5 00:01:30,160 --> 00:01:33,999 empty and abandoned to ice and snow. 6 00:01:37,600 --> 00:01:40,439 Most animals migrated south weeks ago. 7 00:01:41,920 --> 00:01:45,239 The few that stay will face violent winds, 8 00:01:45,320 --> 00:01:48,719 plunging temperatures and months of darkness. 9 00:01:52,680 --> 00:01:55,519 A female polar bear searches for shelter. 10 00:02:00,520 --> 00:02:03,799 Other bears are out on the frozen ocean looking for food 11 00:02:03,880 --> 00:02:07,119 but she won't feed again until next spring. 12 00:02:11,400 --> 00:02:16,759 Using as little energy as possible, she starts to dig a shallow nest. 13 00:02:24,040 --> 00:02:26,599 The snow here is easy to work. 14 00:02:26,680 --> 00:02:28,039 It's soft and light, 15 00:02:28,120 --> 00:02:31,999 a sure sign that soon plenty more will accumulate on this slope, 16 00:02:32,080 --> 00:02:33,719 as winter advances. 17 00:02:36,280 --> 00:02:37,959 And that is what she needs. 18 00:02:48,800 --> 00:02:53,919 If she has chosen well, the Arctic wind will do much of her work for her. 19 00:03:07,680 --> 00:03:10,039 Once the snow here is deep enough, 20 00:03:10,120 --> 00:03:12,319 she will dig down to make a den. 21 00:03:12,920 --> 00:03:17,919 She'll then lie, waiting for her cubs to be born as winter sets in. 22 00:03:34,040 --> 00:03:38,399 The sea-ice already covers twice the area it did in summer. 23 00:03:38,480 --> 00:03:42,999 Those animals that a few weeks ago came down here feed in the sea 24 00:03:43,080 --> 00:03:44,719 are now locked out. 25 00:03:47,240 --> 00:03:50,199 But there are windows in this white desert, 26 00:03:50,280 --> 00:03:53,159 gateways to the rich ocean below. 27 00:03:58,160 --> 00:04:02,719 Most birds have migrated south, but in the frozen Bering Sea, 28 00:04:02,800 --> 00:04:05,319 ducks of one particular species 29 00:04:05,400 --> 00:04:08,839 are gathering together in a single, immense flock. 30 00:04:14,480 --> 00:04:19,279 Spectacled eiders, hundreds of thousands of them. 31 00:04:50,600 --> 00:04:54,239 With the seas that fed them throughout the summer all but frozen, 32 00:04:54,320 --> 00:04:57,079 this is the eider's last refuge. 33 00:05:04,680 --> 00:05:08,839 Such patches of open water, kept free of ice by strong currents, 34 00:05:08,920 --> 00:05:12,079 are given a Russian name, polynyas. 35 00:05:19,440 --> 00:05:21,999 If this polynya stays open all winter, 36 00:05:22,080 --> 00:05:25,079 the ducks will have avoided an exhausting migration. 37 00:05:26,480 --> 00:05:31,079 It's a gamble and a tremendous risk, especially for the spectacled eider, 38 00:05:31,160 --> 00:05:35,039 for this polynya holds the world's entire population. 39 00:05:54,840 --> 00:05:56,679 Surrounded by ice, 40 00:05:56,760 --> 00:06:02,039 these spectacled eiders' survival depends on this single, vulnerable oasis 41 00:06:02,640 --> 00:06:05,839 and conditions here can change very fast. 42 00:06:18,720 --> 00:06:20,279 A smaller pool. 43 00:06:21,320 --> 00:06:24,999 Here, common eider ducks are learning a bitter lesson. 44 00:06:26,400 --> 00:06:31,279 An early winter storm has caught them out and the ice is closing in. 45 00:06:34,440 --> 00:06:38,719 The pool is shrinking and the ducks are freezing to death. 46 00:06:53,000 --> 00:06:55,599 These gamblers have lost. 47 00:07:09,880 --> 00:07:14,279 As the sun's influence continues to dwindle here in the north, 48 00:07:14,360 --> 00:07:18,039 the cold pushes south into Arctic lands. 49 00:07:35,720 --> 00:07:39,839 Winter brings a devastatingly destructive force, 50 00:07:41,240 --> 00:07:42,559 frost. 51 00:07:47,280 --> 00:07:51,199 Ice crystals form as moisture in the air freezes. 52 00:07:52,960 --> 00:07:56,839 Inside plants, the same thing is happening to the water in their cells 53 00:07:56,920 --> 00:07:58,679 and their sap. 54 00:08:02,400 --> 00:08:06,159 With these first frosts, most plants die, 55 00:08:06,240 --> 00:08:09,959 their insides ripped apart by ice crystals. 56 00:08:16,440 --> 00:08:19,519 Coniferous trees, however, like fir and pine, 57 00:08:19,600 --> 00:08:21,919 can withstand very low temperatures. 58 00:08:25,000 --> 00:08:29,359 It's these trees that create the greatest forest on our planet. 59 00:08:31,520 --> 00:08:33,799 This is the Taiga. 60 00:08:40,800 --> 00:08:45,119 It encircles the globe and contains one third of all the trees on Earth. 61 00:08:57,480 --> 00:08:58,919 As winter deepens, 62 00:08:59,000 --> 00:09:03,319 frigid air from the Arctic meets warm, moist air from the south, 63 00:09:03,400 --> 00:09:06,239 producing particularly heavy snows. 64 00:09:12,880 --> 00:09:14,959 For the big animals of the forest, 65 00:09:15,040 --> 00:09:17,559 there's no way of hiding from the winter. 66 00:09:22,600 --> 00:09:27,839 But size, for the bison of Northern Canada, is in fact their salvation. 67 00:09:27,920 --> 00:09:31,999 Big bodies lose less heat and can carry more insulation. 68 00:09:33,280 --> 00:09:38,479 That may be why these bison are the largest land animals in North America. 69 00:09:41,960 --> 00:09:45,239 And only a large predator can tackle them. 70 00:09:53,680 --> 00:09:55,559 Wolves hunt better in packs, 71 00:09:55,640 --> 00:10:00,119 but there are only two of them here and the prey they pursue are giants. 72 00:10:16,880 --> 00:10:20,119 A vast Arctic wilderness stretches all around. 73 00:10:20,960 --> 00:10:23,879 In it, somewhere, there are bison. 74 00:10:30,280 --> 00:10:34,559 These deep tracks in the snow are easy to follow 75 00:10:34,640 --> 00:10:37,199 but which way were the bison going? 76 00:10:52,480 --> 00:10:55,679 They have detected a scent, the hunt is on. 77 00:11:01,000 --> 00:11:03,319 Running in the bison's tracks is easy. 78 00:11:03,400 --> 00:11:05,879 The snow here is compressed and firm. 79 00:11:07,640 --> 00:11:10,519 At this rate, the wolves will soon catch up. 80 00:11:15,560 --> 00:11:17,439 They attempt a shortcut. 81 00:11:18,960 --> 00:11:22,999 The giant bison can plough on through virgin snow, 82 00:11:23,080 --> 00:11:25,399 but for the wolves, deep snow is a hindrance 83 00:11:25,480 --> 00:11:27,879 and now they're losing ground. 84 00:11:45,280 --> 00:11:50,199 The hunters rejoin the bison's tracks and the contest is on again. 85 00:12:07,800 --> 00:12:10,719 The bison are the only prey here in winter, 86 00:12:10,800 --> 00:12:14,039 the wolves have no option, they must tackle them. 87 00:12:16,760 --> 00:12:19,319 But bison are 10 times their size! 88 00:12:37,520 --> 00:12:41,399 In winter, the line between life and death is so narrow 89 00:12:41,480 --> 00:12:45,199 that for a wolf, even a small injury could be fatal. 90 00:12:46,320 --> 00:12:48,919 It's crucial they select the right target. 91 00:12:50,000 --> 00:12:51,799 This one is very big. 92 00:12:53,480 --> 00:12:54,959 Good decision! 93 00:13:14,520 --> 00:13:16,999 This is smaller, a yearling. 94 00:13:19,680 --> 00:13:23,999 Even though it's young, it's nonetheless heavier than both wolves combined 95 00:13:24,080 --> 00:13:26,239 and it is extremely powerful. 96 00:13:53,400 --> 00:13:57,559 The male wolf backs off, perhaps he's frightened of injury. 97 00:13:57,640 --> 00:14:01,199 But the female is the more determined, or more desperate. 98 00:14:41,880 --> 00:14:46,079 Having given so much already, she must make the kill. 99 00:14:46,520 --> 00:14:50,399 This a battle of life and death for them both. 100 00:15:01,840 --> 00:15:04,599 The bison has no strength left, 101 00:15:06,040 --> 00:15:07,759 the battle is over. 102 00:15:19,880 --> 00:15:21,959 Winter deepens, 103 00:15:22,040 --> 00:15:26,359 the snow continues to accumulate, smothering the forest. 104 00:15:37,760 --> 00:15:41,439 Some trees are loaded with three tons of snow. 105 00:15:43,480 --> 00:15:46,879 It shuts out what little light there is at these latitudes, 106 00:15:46,960 --> 00:15:50,159 and that shortens the growing season still further 107 00:15:50,240 --> 00:15:53,439 and limits how far north trees are able to grow. 108 00:16:02,760 --> 00:16:07,199 So snow influences both the shapes of the trees 109 00:16:07,280 --> 00:16:09,439 and the extent of this forest. 110 00:16:15,560 --> 00:16:17,599 And it affects the animals, too. 111 00:16:20,600 --> 00:16:25,439 It helps to have friends if you want to find food at this time of the year. 112 00:16:27,200 --> 00:16:31,119 Wolverines and ravens, a match made in the Taiga. 113 00:16:34,000 --> 00:16:36,999 It's the hardest time of the year to find food. 114 00:16:37,200 --> 00:16:41,919 But the wolverine knows that a raven's call is as good as a dinner bell. 115 00:16:45,640 --> 00:16:50,479 And the raven has just recruited the best can-opener in the forest. 116 00:16:53,680 --> 00:16:55,919 The moose carcass is frozen solid, 117 00:16:56,000 --> 00:16:58,799 but the wolverine has immensely powerful jaws, 118 00:16:58,880 --> 00:17:01,839 well able to deal with "frozen food". 119 00:17:02,400 --> 00:17:06,359 The raven's bill is more suited to leftovers. 120 00:17:18,080 --> 00:17:19,919 The raven has to be patient. 121 00:17:27,800 --> 00:17:30,319 A wolverine's appetite is legendary. 122 00:17:31,080 --> 00:17:34,399 According to folklore, it can eat more at one sitting 123 00:17:34,480 --> 00:17:39,039 than any other creature in the forest, hence its other name, the glutton. 124 00:17:51,200 --> 00:17:55,839 What the wolverine can't eat now, it stores in the deep freeze. 125 00:17:56,640 --> 00:17:59,719 It will bury these food parcels across the forest, 126 00:17:59,800 --> 00:18:02,319 planning ahead for leaner times. 127 00:18:12,680 --> 00:18:16,239 For a few, the snow is an ally. 128 00:18:32,480 --> 00:18:36,599 Voles stay active throughout the winter beneath the snow, 129 00:18:36,680 --> 00:18:39,399 despite the freezing temperatures above. 130 00:18:45,160 --> 00:18:47,279 Travelling along tiny corridors, 131 00:18:47,360 --> 00:18:51,479 they move from pocket to pocket of perfectly refrigerated food. 132 00:18:55,680 --> 00:18:58,039 Snow is a great insulator, 133 00:18:58,120 --> 00:19:03,679 so down here the temperature never falls more than a degree or so below zero 134 00:19:04,160 --> 00:19:06,919 and that's warm enough for a vole to thrive, 135 00:19:07,000 --> 00:19:09,679 even if it lacks the stature of a bison. 136 00:19:17,280 --> 00:19:19,919 In some years vole numbers boom, 137 00:19:20,800 --> 00:19:24,839 and then they are forced break cover to search for more food. 138 00:19:53,000 --> 00:19:56,799 The great grey owl is silent and very skillful hunter, 139 00:19:56,880 --> 00:20:00,079 but deep snow can be beyond its reach. 140 00:20:05,360 --> 00:20:08,879 But such snow is no barrier to one predator. 141 00:20:12,040 --> 00:20:13,679 The least weasel. 142 00:20:14,680 --> 00:20:17,999 A tiny hunter and the vole's nemesis. 143 00:20:21,680 --> 00:20:25,279 Its body is exactly the same width as a vole's, 144 00:20:25,360 --> 00:20:29,079 so there's nowhere a vole can go that the weasel can't follow. 145 00:21:14,040 --> 00:21:18,519 The weasel's long, slender shape is perfect for hunting in tunnels, 146 00:21:18,600 --> 00:21:21,559 but the worst possible shape for staying warm. 147 00:21:21,680 --> 00:21:24,359 So they need a special way of doing that. 148 00:21:33,960 --> 00:21:37,439 She plucks the fur from its body, tuft by tuft. 149 00:21:47,400 --> 00:21:51,399 And now she puts it all together to make a cozy blanket, 150 00:21:51,480 --> 00:21:54,639 under which to sleep in her den below the snow. 151 00:22:09,560 --> 00:22:12,079 Midwinter in the northern forests. 152 00:22:13,720 --> 00:22:17,199 The sun is so low that it's twilight at midday. 153 00:22:23,520 --> 00:22:25,919 Further north in the high Arctic, 154 00:22:26,000 --> 00:22:28,719 the sun has been below the horizon for months 155 00:22:28,800 --> 00:22:31,839 and it'll be several more before it appears again. 156 00:23:21,680 --> 00:23:25,639 The male polar bear spends winter out on the frozen ocean. 157 00:23:28,600 --> 00:23:31,359 Few creatures can endure these conditions. 158 00:23:37,800 --> 00:23:42,399 If he's lucky, he will find a carcass that could provide a little food, 159 00:23:42,480 --> 00:23:45,839 possibly that of a fox or another polar bear. 160 00:23:49,040 --> 00:23:52,399 But otherwise, he must live on his reserves. 161 00:23:55,160 --> 00:23:59,319 This is the time to scrape by, to wait. 162 00:24:08,800 --> 00:24:14,999 But on lee-side slopes, beneath the snow, new lives are beginning. 163 00:24:34,720 --> 00:24:38,599 The cubs are born blind and tiny, 164 00:24:38,680 --> 00:24:42,599 an early birth is easier on the mother, who is barely awake. 165 00:24:57,200 --> 00:25:02,359 Despite her sleepiness, her instinct to nurse is overwhelming. 166 00:25:16,960 --> 00:25:21,119 The cubs' clucking calls stimulate her to produce milk. 167 00:25:21,680 --> 00:25:23,439 And what milk! 168 00:25:23,600 --> 00:25:26,279 It's nine times richer than our own 169 00:25:26,360 --> 00:25:29,799 and enables her to double their weight every few weeks. 170 00:25:48,320 --> 00:25:52,439 It's over two months since the autumn snows first arrived. 171 00:25:53,360 --> 00:25:58,239 In two more months, polar bear families will emerge onto the snowy slopes 172 00:25:58,320 --> 00:25:59,999 all around the Arctic. 173 00:26:01,200 --> 00:26:05,759 But for now, they lie protected within their icy cocoons. 174 00:26:29,160 --> 00:26:34,479 A hundred miles above the earth, the Aurora lights up the sky. 175 00:26:44,800 --> 00:26:47,759 After travelling millions of miles across space, 176 00:26:47,840 --> 00:26:51,719 solar winds, attracted by the magnetic pull of the poles, 177 00:26:51,840 --> 00:26:54,159 collide with the Earth's atmosphere. 178 00:26:56,360 --> 00:27:00,999 Trillions of charged particles dance across the sky. 179 00:27:09,200 --> 00:27:14,239 Above the Arctic, the Aurora Borealis, the Northern Lights. 180 00:27:15,400 --> 00:27:19,999 In the south, it's the Aurora Australis, the Southern Lights, 181 00:27:20,080 --> 00:27:23,159 that bring light to Antarctica's long winter. 182 00:27:31,800 --> 00:27:35,839 These spectacular light shows are only a tease. 183 00:27:35,920 --> 00:27:41,119 Solar energy maybe, but no warmth that will help the emperor penguins. 184 00:27:54,120 --> 00:27:56,839 The Arctic winter is brutally cold, 185 00:27:56,960 --> 00:28:01,199 but in Antarctica, the darkest months are even more savage. 186 00:28:17,560 --> 00:28:20,759 The male penguins have not eaten for months 187 00:28:20,840 --> 00:28:24,279 and have only each other for protection from the gales. 188 00:28:34,400 --> 00:28:37,279 Each has been entrusted with a single precious egg, 189 00:28:37,360 --> 00:28:39,319 balanced on top of its feet. 190 00:28:39,880 --> 00:28:41,999 If the egg were to drop onto the ice, 191 00:28:42,080 --> 00:28:45,239 even for a moment, the chick inside would die 192 00:28:45,320 --> 00:28:47,599 and all this would count for nothing. 193 00:28:56,080 --> 00:28:58,919 The emperors are not entirely alone. 194 00:29:03,840 --> 00:29:05,879 The Weddell seal, 195 00:29:05,960 --> 00:29:09,399 the only mammal to remain here throughout the winter. 196 00:29:15,640 --> 00:29:17,759 They must have breathing holes, 197 00:29:17,840 --> 00:29:21,919 and so have to constantly scrape away the ice that threatens to close them, 198 00:29:22,000 --> 00:29:26,599 rasping away fresh build-ups with special, wide-gaped jaws. 199 00:29:31,800 --> 00:29:36,359 Beneath the ice, they are beyond the reach of the bitter winter winds. 200 00:29:40,400 --> 00:29:43,559 The sea is -2 degrees centigrade, 201 00:29:43,640 --> 00:29:47,239 a warm bath compared to the conditions overhead. 202 00:29:59,400 --> 00:30:04,519 The roof of ice insulates this world from the wild fluctuations above. 203 00:30:06,400 --> 00:30:11,679 The temperature down here has barely changed for 25 million years. 204 00:30:20,000 --> 00:30:23,639 Of course, animals must still be hardy. 205 00:30:23,720 --> 00:30:27,919 These Borchgrevinki fish have anti-freeze in their blood, 206 00:30:28,000 --> 00:30:31,359 so they are untroubled swimming among the ice crystals. 207 00:30:36,960 --> 00:30:40,079 Many animals here are remarkably long-lived, 208 00:30:40,160 --> 00:30:42,919 perhaps because the conditions are so stable. 209 00:30:43,800 --> 00:30:46,759 Some sponges could be a thousand years old 210 00:30:46,840 --> 00:30:49,199 and large enough for a human to hide in. 211 00:30:51,480 --> 00:30:53,559 There could hardly be a greater contrast 212 00:30:53,640 --> 00:30:57,239 to the bleak, windswept world just above. 213 00:31:30,480 --> 00:31:33,639 But there is a constant danger here. 214 00:31:39,480 --> 00:31:43,159 Swirling patterns in the water reveal its presence. 215 00:31:44,760 --> 00:31:49,199 They are made by brine, super-concentrated salt water. 216 00:31:50,480 --> 00:31:51,479 It's a warning. 217 00:31:56,400 --> 00:31:58,279 New sea-ice forming above 218 00:31:58,360 --> 00:32:02,959 leaves behind brine that is so extremely salty it sinks rapidly. 219 00:32:08,920 --> 00:32:12,879 As it descends, the sea water around it freezes instantly 220 00:32:12,960 --> 00:32:15,199 and forms a sheath of ice, 221 00:32:15,280 --> 00:32:19,199 a brinicle that grows downwards towards the sea floor. 222 00:32:29,560 --> 00:32:33,159 Winter is reaching down from the cold world above. 223 00:32:47,000 --> 00:32:51,559 As it touches the sea floor, it kills whatever living thing it contacts 224 00:32:51,640 --> 00:32:54,719 by encasing it in a tomb of ice. 225 00:33:21,320 --> 00:33:23,959 Even in the relative warmth of the water, 226 00:33:24,040 --> 00:33:28,319 the lethal cold of winter threatens life on the sea floor. 227 00:33:38,680 --> 00:33:42,799 Another more constant attack rises from below. 228 00:33:43,880 --> 00:33:46,159 Pressure in the depths keeps water liquid 229 00:33:46,240 --> 00:33:48,999 even though its temperature is far from freezing. 230 00:33:52,240 --> 00:33:56,239 Currents bring up this colder water and it turns to ice, 231 00:33:56,320 --> 00:33:59,479 covering everything that can't move away from it. 232 00:34:21,600 --> 00:34:26,519 And then the ice, being lighter than water, begins to float, 233 00:34:27,200 --> 00:34:29,559 lifting away anything attached. 234 00:34:50,080 --> 00:34:53,319 Even some of the faster-moving animals are caught. 235 00:35:09,160 --> 00:35:12,439 So the ice cleanses the sea floor 236 00:35:12,520 --> 00:35:16,999 and strews the ceiling above with remnants of life from below. 237 00:35:28,160 --> 00:35:31,519 A sign that winter is nearly over. 238 00:35:34,080 --> 00:35:39,159 The songs of male Weddell seals, challenging their rivals to battle. 239 00:35:45,880 --> 00:35:49,719 The male seal's calls can heard over 15 miles away. 240 00:36:01,480 --> 00:36:04,559 He aims to control the best breathing holes, 241 00:36:04,640 --> 00:36:07,759 for they will determine his mating rights in spring. 242 00:36:15,480 --> 00:36:19,159 His calls create powerful shockwaves in the water. 243 00:36:19,960 --> 00:36:21,279 They are threats. 244 00:36:32,440 --> 00:36:34,719 This hole has already been claimed 245 00:36:34,800 --> 00:36:37,439 and the owner will not surrender it willingly. 246 00:36:47,760 --> 00:36:49,679 No change this time. 247 00:36:50,360 --> 00:36:53,999 The challenger will need to find a hole with a weaker owner. 248 00:37:02,200 --> 00:37:05,879 The battles continue until the females arrive, 249 00:37:05,960 --> 00:37:08,839 and that time is now close. 250 00:37:35,400 --> 00:37:38,239 The sun returns to Antarctica. 251 00:37:41,120 --> 00:37:46,159 The longest night on earth has ended and winter begins to give way to spring. 252 00:38:16,840 --> 00:38:18,919 Female emperor penguins. 253 00:38:19,000 --> 00:38:23,759 After four months feeding at sea, they are returning sleek and fat. 254 00:38:55,000 --> 00:38:58,519 Penguins, it seems, can fly after all. 255 00:39:01,000 --> 00:39:04,399 But a winter at sea has left them a little out of practice. 256 00:39:57,200 --> 00:40:01,879 There is no time to waste. Far away, the males are waiting. 257 00:40:12,680 --> 00:40:15,959 While the females were gone, the sea-ice grew 258 00:40:16,080 --> 00:40:19,679 and it's now twice the distance from its edge back to their colony. 259 00:40:27,400 --> 00:40:31,919 Seventy miles away, the males are in desperate need of help. 260 00:40:34,800 --> 00:40:37,839 Despite doing all they can to conserve their energy, 261 00:40:37,920 --> 00:40:41,119 many are close to dying from starvation. 262 00:41:32,440 --> 00:41:35,719 Reunited after three months apart. 263 00:41:46,720 --> 00:41:50,959 The reward for her return, a first glimpse of her chick. 264 00:41:57,280 --> 00:42:00,719 The reunion made, it's time for the hand-over. 265 00:42:05,800 --> 00:42:09,199 The father finds it hard to let go. 266 00:42:12,200 --> 00:42:14,839 Some gentle persuasion is needed. 267 00:42:17,280 --> 00:42:20,599 He has endured the most appalling conditions on Earth 268 00:42:20,680 --> 00:42:24,839 to ensure the survival of his chick and the bond is strong. 269 00:42:27,400 --> 00:42:28,999 The exchange must be quick, 270 00:42:29,080 --> 00:42:33,599 as the tiny chick, unprotected, could freeze to death in seconds. 271 00:42:45,040 --> 00:42:48,959 A task that began in autumn has been completed. 272 00:42:49,040 --> 00:42:51,239 Despite the huge odds against it, 273 00:42:51,320 --> 00:42:53,879 the precious chick has survived the winter 274 00:42:53,960 --> 00:42:57,639 and is now with its mother, and she has food. 275 00:43:08,000 --> 00:43:10,199 The chick's first fresh meal. 276 00:43:12,400 --> 00:43:14,159 Her mission is complete. 277 00:43:18,200 --> 00:43:22,799 But for other mothers, the journey ends in disappointment. 278 00:43:25,640 --> 00:43:28,159 Their chicks have not survived. 279 00:43:32,520 --> 00:43:35,879 The female's need to nurture remains strong. 280 00:43:35,960 --> 00:43:40,639 Any chick that strays from its parent is at grave risk of being kidnapped. 281 00:44:17,960 --> 00:44:21,799 The chaos may be a consequence of frustrated parental urge, 282 00:44:21,920 --> 00:44:24,039 but the outcome can be tragic. 283 00:44:41,600 --> 00:44:46,999 For those emperor penguins that survive, the worst is over for this year. 284 00:44:52,400 --> 00:44:55,479 There will soon be abundant food for everyone. 285 00:45:05,080 --> 00:45:08,719 The emperors have taken on the polar winter and won. 286 00:45:09,640 --> 00:45:11,599 The gamble has paid off. 287 00:45:13,120 --> 00:45:15,079 All other animals escaped, 288 00:45:15,160 --> 00:45:17,719 only they remained to raise their young, 289 00:45:18,520 --> 00:45:23,639 and now it is they who will benefit most from the rich southern spring. 290 00:45:32,520 --> 00:45:36,479 Another arrival is the certain confirmation that spring is here. 291 00:45:37,360 --> 00:45:38,559 The Adélies, 292 00:45:38,640 --> 00:45:41,799 having spent winter at sea, have come back, 293 00:45:41,880 --> 00:45:45,919 but they have not even mated yet, let alone laid their eggs. 294 00:45:54,120 --> 00:45:56,639 Now at last, the male emperors 295 00:45:56,720 --> 00:45:59,119 can return to where they are most at home. 296 00:46:15,360 --> 00:46:18,719 One season ends and another begins. 297 00:46:20,080 --> 00:46:23,279 The penguins will soon be joined by migrants 298 00:46:23,360 --> 00:46:27,879 and the far south will bustle with life for a few frantic months. 299 00:46:38,200 --> 00:46:42,599 But there are only a special few, north and south, 300 00:46:42,680 --> 00:46:47,319 who can survive winter at the farthest ends of our planet. 301 00:47:29,600 --> 00:47:31,879 More than any other season in the poles, 302 00:47:31,960 --> 00:47:35,719 winter was to pose the greatest challenge to the Frozen Planet crew. 303 00:47:37,080 --> 00:47:39,919 The team endured winds of over 100 miles an hour 304 00:47:40,000 --> 00:47:43,439 and temperatures as low as -50 degrees centigrade. 305 00:47:44,560 --> 00:47:47,199 Their boats were trapped in sea-ice for days, 306 00:47:47,280 --> 00:47:50,039 while bears trapped others indoors. 307 00:47:55,000 --> 00:47:57,119 Some of the coldest conditions experienced 308 00:47:57,200 --> 00:47:59,919 were near the Arctic circle in Northern Canada. 309 00:48:01,200 --> 00:48:05,079 In winter, temperatures dropped to -40 degrees and stayed there. 310 00:48:07,320 --> 00:48:09,839 On the edge of the vast Taiga forest, 311 00:48:09,920 --> 00:48:12,239 the team hoped to film one the most remarkable 312 00:48:12,320 --> 00:48:14,679 predator-prey relationships on the planet. 313 00:48:16,480 --> 00:48:20,199 What they experienced was the struggle against the elements, 314 00:48:20,320 --> 00:48:24,799 what they witnessed was a more profound struggle for life and death. 315 00:48:35,640 --> 00:48:39,999 Wood Buffalo National Park covers 28,000 square miles, 316 00:48:40,080 --> 00:48:41,479 the size of Denmark. 317 00:48:42,400 --> 00:48:47,039 One of the few cameramen to have filmed wolves and bison here is Jeff Turner. 318 00:48:47,640 --> 00:48:49,759 I first tried to film bison and wolves 319 00:48:49,840 --> 00:48:54,799 in this national park 15 years ago and getting around on the ground 320 00:48:54,880 --> 00:48:58,879 is incredibly difficult at any time of the year, but in the winter it's tough. 321 00:48:58,960 --> 00:49:02,079 We quickly realized that the only way we were going to get anything here 322 00:49:02,200 --> 00:49:04,199 was we had to get up in the air. 323 00:49:04,280 --> 00:49:05,639 The Frozen Planet team 324 00:49:05,720 --> 00:49:08,839 had never attempted aerial filming in such low temperatures. 325 00:49:11,480 --> 00:49:13,919 The first challenge for director Chadden Hunter 326 00:49:14,000 --> 00:49:16,359 was protecting the sensitive aerial camera, 327 00:49:16,440 --> 00:49:20,959 at -40, electrical cables short-circuit like fireworks. 328 00:49:22,440 --> 00:49:23,759 - Oh! - Ooh. 329 00:49:24,360 --> 00:49:27,959 - How cold can you fly this chopper? - Minus-40. 330 00:49:28,160 --> 00:49:32,039 Aerial cameraman Michael Kelem comes from sunny California 331 00:49:32,120 --> 00:49:34,639 and has never experienced temperatures so low. 332 00:49:34,720 --> 00:49:37,519 What kind of temperatures can you operate down to? 333 00:49:37,600 --> 00:49:41,239 Me, usually about 70 degrees Fahrenheit. LA kind of weather, 334 00:49:41,320 --> 00:49:43,479 - Yeah. - I'm only rated for Santa Monica. 335 00:49:44,920 --> 00:49:47,959 Operating delicate controls while wearing gloves 336 00:49:48,040 --> 00:49:51,399 is not easy. A computer and joystick are needed 337 00:49:51,480 --> 00:49:55,079 to control the aerial camera attached to the outside of the helicopter. 338 00:49:55,160 --> 00:49:56,959 It's actually warmed up to -30. 339 00:49:57,040 --> 00:50:01,199 Michael would have to choose between dexterity or warmth. 340 00:50:03,680 --> 00:50:05,399 With their camera mounted on the nose, 341 00:50:05,480 --> 00:50:09,479 the aerial team could now fly hundreds of miles in search of the animals. 342 00:50:11,200 --> 00:50:12,999 Jeff, meanwhile, is still on foot, 343 00:50:13,080 --> 00:50:15,559 scouting the other side of the national park. 344 00:50:16,160 --> 00:50:17,959 I wonder what Jeff’s getting on the ground? 345 00:50:18,040 --> 00:50:19,879 Oh, man, it's cold. 346 00:50:20,320 --> 00:50:23,279 With the wind today it's about -37 347 00:50:23,360 --> 00:50:25,559 so you got to keep these heaters in here, 348 00:50:25,640 --> 00:50:27,719 to keep the camera running at these temperatures. 349 00:50:28,760 --> 00:50:30,319 From 3,000 feet up, 350 00:50:30,400 --> 00:50:33,399 Chadden catches a glimpse of the elusive wolf pack. 351 00:50:34,520 --> 00:50:37,359 I can see wolves, I can see wolves near buffalo. 352 00:50:37,440 --> 00:50:39,919 - 10, 15, there's a big pack. - Wow. 353 00:50:40,040 --> 00:50:42,279 We've got a big pack of wolves here. 354 00:50:42,400 --> 00:50:47,119 The wolf pack turns out to number an extraordinary 25 individuals, 355 00:50:47,200 --> 00:50:48,919 one of the largest ever filmed. 356 00:50:49,000 --> 00:50:51,159 There's two more walking in from the left. 357 00:50:51,240 --> 00:50:54,079 And it looks like they're already on the hunt. 358 00:50:54,160 --> 00:50:58,239 The helicopter allows the team to shadow the wolf pack without disturbing them. 359 00:50:58,320 --> 00:51:02,639 So, let's go back into nice, slow circle around them. 360 00:51:03,840 --> 00:51:05,639 They look pretty determined. 361 00:51:05,720 --> 00:51:07,679 The pack are moving in on their prey 362 00:51:07,760 --> 00:51:10,319 and the aerial team are perfectly placed. 363 00:51:13,880 --> 00:51:15,519 They're making their... definitely making their move. 364 00:51:15,600 --> 00:51:18,599 Wow, there's buffalo on the move. 365 00:51:19,600 --> 00:51:22,679 - The chase is on. - Extreme concentration is now needed 366 00:51:22,760 --> 00:51:25,879 both from pilot and the cameraman to keep the shots smooth. 367 00:51:28,640 --> 00:51:30,199 Yeah, there's more coming in now. 368 00:51:30,280 --> 00:51:32,479 There's a nice, tight little pack challenging them. 369 00:51:32,560 --> 00:51:34,239 We've got a nice shot of the pack, 370 00:51:34,320 --> 00:51:36,959 the wolves coming up at the back. You got them still? 371 00:51:37,040 --> 00:51:38,919 Yeah, I got them here, I'm just going to pick it up a little bit. 372 00:51:39,040 --> 00:51:42,239 Okay, okay, tighten up, just a hair. 373 00:51:42,320 --> 00:51:44,959 Just want to get a shot of the wolves at the back of the pack. 374 00:51:45,080 --> 00:51:47,879 The wolf pack have picked out a young bison. 375 00:51:49,560 --> 00:51:50,879 Holy. 376 00:51:51,240 --> 00:51:53,599 As Michael struggles to hold the shot steady, 377 00:51:53,680 --> 00:51:55,879 no one is prepared for what came next. 378 00:51:56,320 --> 00:52:00,239 Oh, hey, look, they just knocked him down, pretty much. 379 00:52:01,560 --> 00:52:03,239 A one-ton bull charges through, 380 00:52:03,320 --> 00:52:06,479 taking out both the wolves and the young bison. 381 00:52:08,440 --> 00:52:12,519 I've never seen anything like that in the wild, that is unbelievable. 382 00:52:13,600 --> 00:52:16,559 The team have filmed extraordinary new behavior from the air 383 00:52:16,640 --> 00:52:18,879 but Jeff was nowhere nearby. 384 00:52:20,080 --> 00:52:22,839 To complete the sequence, they will need to work together, 385 00:52:22,920 --> 00:52:25,599 only by using the helicopter to position Jeff 386 00:52:25,680 --> 00:52:29,239 will they able to get both air and ground coverage. 387 00:52:38,480 --> 00:52:42,799 This pack will now feast for days, so the crew must move on. 388 00:52:44,800 --> 00:52:47,119 Jeff takes the team deeper into the wilderness 389 00:52:47,200 --> 00:52:49,759 in search of a new wolf pack. 390 00:52:49,840 --> 00:52:53,439 With everyone on board, there are more eyes for spotting. 391 00:52:54,560 --> 00:52:57,959 Bison on the run can only mean one thing, wolves. 392 00:52:58,360 --> 00:53:01,639 But this time, only a pair. 393 00:53:02,720 --> 00:53:05,479 Jeff must anticipate the animals' every move 394 00:53:05,560 --> 00:53:09,119 and direct the helicopter to where he needs to be dropped off. 395 00:53:09,200 --> 00:53:10,679 They're going this way. 396 00:53:12,600 --> 00:53:14,159 I had to figure out exactly 397 00:53:14,240 --> 00:53:16,919 where the buffalo were going to run, try to get there ahead of them. 398 00:53:18,000 --> 00:53:21,119 If I got dropped off in the wrong position, we would blow it. 399 00:53:22,440 --> 00:53:24,399 There wasn't going to be a second chance. 400 00:53:33,920 --> 00:53:36,279 That moment when you get out of the helicopter 401 00:53:36,360 --> 00:53:40,679 and it leaves you behind, you feel an incredible sense of isolation. 402 00:53:43,400 --> 00:53:44,879 On the lake, I'll guide you in, 403 00:53:44,960 --> 00:53:48,439 down to the right, down, zoom in. 404 00:53:49,480 --> 00:53:52,639 - Are you on the back guy? - We're on the back guy. On the back. 405 00:53:53,320 --> 00:53:55,719 - Which one is he going for? - I don't know. 406 00:53:56,080 --> 00:53:57,919 - But there's one broken off. - Oh! 407 00:53:58,520 --> 00:54:01,519 - Oh, my God. - They're coming in now. 408 00:54:02,760 --> 00:54:04,319 When I saw the herd coming around the corner, 409 00:54:04,400 --> 00:54:07,759 I knew we'd picked the right spot, I was right in front of them. 410 00:54:09,120 --> 00:54:10,879 And the buffalo running right towards you, 411 00:54:10,960 --> 00:54:12,919 it definitely does get your heart pounding. 412 00:54:15,320 --> 00:54:16,879 The bison have poor eyesight 413 00:54:16,960 --> 00:54:20,359 and can't see Jeff. It's now test of nerves. 414 00:54:21,320 --> 00:54:24,039 Weighing one ton and running at 40 miles an hour, 415 00:54:24,120 --> 00:54:26,879 one wrong step and the bison could kill Jeff. 416 00:54:27,240 --> 00:54:28,519 At the last second, 417 00:54:28,600 --> 00:54:31,279 they spot him and three peel away to the other side. 418 00:54:34,680 --> 00:54:37,719 At the back of the herd, the wolves have closed in. 419 00:54:39,400 --> 00:54:42,559 They're still at him. They're trying to separate that little one. 420 00:54:45,920 --> 00:54:48,999 - Oh, they got him! - Both wolves are on him. 421 00:54:49,080 --> 00:54:51,039 - Both clamping down on him. - Yeah, he got stomped. 422 00:54:51,120 --> 00:54:52,279 He got stomped on there. 423 00:54:52,400 --> 00:54:55,999 What followed was one of the most emotional and powerful scenes 424 00:54:56,080 --> 00:54:58,519 the Frozen Planet team were ever to film. 425 00:55:00,320 --> 00:55:03,159 Jeff has picked his position perfectly, 426 00:55:03,240 --> 00:55:05,719 he is now only 50 meters from the animals 427 00:55:05,800 --> 00:55:08,439 and able film a truly epic battle. 428 00:55:10,080 --> 00:55:12,959 I had never been so close to a wolf and bison battle, 429 00:55:13,840 --> 00:55:15,999 I could hear them breathing. 430 00:55:16,960 --> 00:55:18,919 And the power of the buffalo, 431 00:55:19,000 --> 00:55:22,359 the way he just threw this wolf around like it was a rag doll. 432 00:55:23,360 --> 00:55:25,839 I couldn't believe the beating this wolf was taking. 433 00:55:29,920 --> 00:55:33,679 The struggles that we'd had with the winter and the cold and the snow 434 00:55:33,760 --> 00:55:37,799 just felt so insignificant compared to these two animals 435 00:55:37,880 --> 00:55:40,119 that were struggling for their very lives. 436 00:55:43,280 --> 00:55:46,279 For over an hour, I watched this wolf and bison 437 00:55:46,360 --> 00:55:48,559 battle each other to a standstill. 438 00:55:50,120 --> 00:55:52,479 They were both unbelievably exhausted. 439 00:56:00,400 --> 00:56:04,279 Watching these two animals engaged in this massive life and death struggle 440 00:56:04,360 --> 00:56:08,039 was one of the most powerful things I'd ever witnessed in the wild. 441 00:56:10,560 --> 00:56:14,319 As a filmmaker, you're definitely torn watching something like this. 442 00:56:14,400 --> 00:56:18,079 You know you need to keep filming and you know this a natural event, 443 00:56:18,600 --> 00:56:20,799 but it's also incredibly sad to know that 444 00:56:20,880 --> 00:56:24,199 one of these two magnificent animals isn't going to make it. 445 00:56:28,560 --> 00:56:33,039 The bison is fatally wounded, the battle is over. 446 00:56:36,000 --> 00:56:39,199 The team have managed to capture a remarkable hunt 447 00:56:39,280 --> 00:56:41,879 from both ground and air. 448 00:56:42,520 --> 00:56:44,119 All of them have been humbled 449 00:56:44,200 --> 00:56:48,039 by witnessing an extraordinary winter struggle for survival.