The Blue Planet 1x4

1. The frozen seas are worlds unto themselves

2. Beneath their ceiling of ice they have an eerie,

3. almost magical stillness, cut off from the storms that rage above

4. In the winter, the feeble slanting rays of the sun bring little warmth

5. and the temperature seldom rises above minus fifty degrees Centigrade

6. For much of the year, it is dark and cripplingly cold

7. Yet, there is life here - at both ends of the earth...

8. the Arctic and the Antarctic

9. For most animals, whether they live in or out of water,

10. the winters, when much of the sea is frozen, bring the greatest challenge

11. The Northern hemisphere

12. It's February, and as the Earth tilts on its axis,

13. the sun's rays creep slowly northwards

14. and the Arctic emerges from its harsh winter

15. The Arctic is a frozen ocean surrounded by continents

16. - and when the surface of the sea between the continents freezes

17. from shore to shore, land predators walk out onto it - to hunt

18. It's early March and the sea is still covered with ice

19. But there are patches of open water - polynyas - that never freeze over

20. Here, where tidal currents are squeezed between islands,

21. the water movement is so strong that ice cannot form

22. Walruses spend the winter in polynyas

23. Here they have permanent access to the air,

24. but they can also retreat to the sea to shelter to hunt

25. Other sea mammals overwinter in the polynyas as well

26. - in this one, a young bowhead whale

27. Here the current is really fast and the shifting ice is dangerous

28. This whale became trapped when ice encircled it last autumn

29. There is no food here, but a whale must breathe and the only place

30. that it can do so, for miles around, is in this tiny hole

31. It's living entirely on its reserves of fat, but now they are dangerously low

32. It will be some months yet, before it can escape

33. Elsewhere, other whales have also been trapped

34. These are belugas

35. Their tiny hole in the ice has been kept open,

36. not by currents but by the belugas' continuous movements

37. as they rise to breathe

38. Open water is now some twenty miles away

39. It will be two months yet before the ice melts

40. The belugas are extremely thin - and most of them are horribly scarred

41. But their wounds were not inflicted by the ice

42. A whale would be a huge prize for any meat-eating hunter and these belugas,

43. trapped by the ice, are within reach of polar bears

44. Well aware of the danger, the belugas stay submerged as long as they can

45. But they can only hold their breath for about twenty minutes

46. Catching a four-metre long whale that weighs one ton is no easy task

47. - even if that whale is weakened by starvation

48. But a beluga is well worth waiting for

49. Day by day, as the hole gets bigger,

50. it becomes increasingly difficult for the bear to land a whale

51. Keeping its fur in good condition and free from salt is important for warmth

52. - and the bear uses snow like blotting paper

53. These belugas have been attacked by many bears over the last six months

54. - and some have been caught

55. It may have taken a long time and a lot of patience, but a catch,

56. when it's made, brings abundant rewards of energy rich blubber

57. Gulls rely on bear-kills at this time of the year

58. - and the colour of blood staining the ice attracts them from a long way away

59. The remaining belugas still have a long wait before they are released

60. from their prison and the threat of slaughter

61. Arctic foxes also rely on the polar bears to hunt on their behalf

62. They're the jackals of the north and scavenge from bear kills whenever they can

63. In winter and early spring, they are wholly dependent on bears

64. Only in the summer, when the sea ice melts,

65. will they regularly catch prey for themselves

66. They are not strong enough to tackle adult seals,

67. but can certainly take new-born pups or birds

68. This canny individual is going to bury its prize

69. - it may need it during the uncertain times ahead

70. The presence of bears affects the behaviour of almost

71. all the animals here - big and small

72. The bears tend to avoid the fringe of fragmented ice bordering open water

73. - where travelling can be very laborious

74. But that very fact makes this area - the pack ice

75. - a particularly good place for seals to pup

76. Harp seals breed here

77. Their pups are born with white coats which camouflage them

78. very effectively against the snow

79. Harp seals have a very short nursing period

80. - a necessity on this unstable pack ice

81. But suckling is intensive

82. The pup feeds for just twelve days on milk that is 45 percent fat

83. Then it is abandoned and has to fend for itself

84. A male hooded seal

85. This impressive nasal display is used to warn away other males...

86. and to win a mate Hooded seals also breed on pack ice

87. Their pups suckle for only four days

88. - the shortest nursing period known for any mammal

89. - and all because the threat of polar bears

90. caused them to breed on the unstable ice

91. Another Arctic seal opts for the solid ice further north

92. Because it's easy for bears to hunt here,

93. these ringed seals must be particularly vigilant and have to hide their pups

94. Ringed seals are comparatively small, so they can give birth

95. to their pups in little caves, or lairs, under the snow

96. Here, a pup is out of sight and protected from bad weather

97. In late March and into April, female bears emerge from winter

98. dens with their new cubs

99. The mother has not eaten for at least five months and she's hungry - very hungry

100. If she doesn't succeed in catching a regular supply of seals,

101. her milk will fail and her cub will die

102. Bears have an extraordinarily sensitive sense of smell

103. and can detect seal pups hidden in the snow from two kilometres away

104. But a female ringed seal uses several lairs

105. and a bear will almost certainly have to break into a number

106. before it finds one that is occupied

107. This is a crucial time for the cub

108. By watching its mother hunt and by copying her actions,

109. it's beginning to acquire the rudiments of its own hunting skills

110. Play is also important for developing muscles and improving co-ordination

111. As the days go by, the sun rises higher

112. and remains above the horizon even at night

113. The female bear continues to hunt

114. until her cub is too tired and can't keep up

115. She has smelt something

116. The pup escapes through a hole in its lair that leads to the sea below

117. Only one in twenty hunts is successful

118. But this mother must find a seal pup soon if her cub is not to starve to death

119. As spring turns into summer, the sun's heat begins to melt the sea ice

120. Now the ocean is accessible and the Arctic's summer visitors return

121. Migrating birds arrive from the south to nest

122. and feed on the seafood that's now within their reach

123. Brunnich's guillemots are the northern equivalent of penguins

124. But they have retained the power of flight,

125. for they need to reach cliff ledges

126. where their nests will be safe from predatory bears and foxes

127. Nonetheless, they are as at home in the water as in the air

128. They dive down to a depth of fifty metres or more to catch fish

129. In June, the ice begins to fracture

130. The cracks - or leads - form useful corridors

131. of open water for air-breathing animals

132. Belugas, migrating to their feeding grounds,

133. use these leads to penetrate the ice-covered seas

134. and reach areas where their preferred food,

135. Arctic cod, has spent the winter

136. The males regularly dive to about five hundred metres to find fish

137. The females and young, which have smaller lungs, only go to about 350

138. In late June and July, narwhals arrive

139. The females, who usually lack tusks, come first with their new calves

140. The males follow a little later

141. They also move up the leads in search of fresh feeding grounds

142. Bowheads. Up to 18 metres long and weighing a hundred tonnes,

143. these are the only large whales that stay in the Arctic all year round

144. They are not after fish They are seeking smaller prey

145. Despite having the largest mouths in the animal kingdom,

146. the size of a small garage, they eat tiny crustaceans

147. - copepods - straining them from the water with the four-metre long strips

148. of baleen that hang from their upper jaws

149. In the summer they store enough energy to last them

150. through the following winter, when food will be less abundant

151. As the ice melts away, the polar bears are forced to head for land

152. They are excellent swimmers and can cover a hundred miles

153. of continuous open water if need be

154. Off east Greenland, there is little ice left by August,

155. so walruses haul out to rest on land

156. At this time of the year they are moulting,

157. getting rid of their old scarred and parasite-ridden skin

158. A bathe in the cold water brings some relief from the itching

159. But even there, the odd scratch is irresistible

160. They make daily excursions out to deeper water

161. Down at 20 metres, they root around in the sediment,

162. using their sensitive bristles to search out soft-shelled clams

163. Once they find a clam, they suck its flesh from the shell

164. with their powerful, muscular mouths

165. Walruses can feed for about five minutes at this depth

166. before they have to return to the surface to breathe

167. Elsewhere in the Arctic, belugas are gathering in their thousands

168. They congregate in just a few large estuaries

169. Belugas of all ages and sizes come here

170. There are even young calves

171. Some are so young - born only a week or so ago - that they need help

172. They swim on their mothers' backs so that they can breathe more easily

173. As the tide moves up the estuary, the belugas follow,

174. swimming into surprisingly shallow water

175. Like walruses, they also need to moult

176. A combination of warm fresh water and vigorous rubbing

177. against the gravel does the trick

178. They remain here for days, or even weeks,

179. so it's likely that socialising is also important to them

180. After moulting, they head back out to sea to feed

181. It's now autumn and the sea begins to freeze over, once again

182. Thin sheets of ice form at the surface and pile up,

183. layer upon layer, gradually creating an impenetrable barrier

184. By late November, the Arctic Ocean is sealed once again by ice

185. The lights of the aurora play in the winter sky

186. At the other end of the planet - in the Antarctic

187. - there is the southern aurora

188. Antarctica is now emerging from winter

189. This is the coldest, windiest place in the world

190. Temperatures are still hovering at a numbing minus 50

191. and the returning sun has virtually no warmth

192. Very few animals can survive such extreme conditions

193. But emperor penguins can

194. Standing on the frozen sea, they endure the full force of the Antarctic storms

195. Only by huddling together can they can survive the appalling winter months

196. They take it in turns to bear the brunt of the gales

197. They can only live here at all because Antarctica is surrounded

198. by the Great Southern Ocean and no land predators have been able to reach it,

199. so unlike Arctic animals, they're not threatened by polar bears

200. The sea is still frozen

201. But one seal, nonetheless, manages to stay here,

202. even throughout the winter...

203. the Weddell seal

204. Underwater, it's protected from the storms above

205. But it must have access to the air all year - in order to breathe

206. And they keep their breathing holes open - with their teeth

207. Only by continually scraping away at the ice can they maintain access to the air

208. But that means that their teeth get badly worn down

209. Then they can no longer hunt and eat effectively

210. Weddell seals die young

211. The continent of Antarctica is so isolated

212. and so high - almost five thousand metres in places

213. - that it's considerably colder than the Arctic

214. Ice slides slowly down from its centre towards its rim in immense glaciers

215. During winter, the continent effectively doubles in size as the sea freezes over

216. Ice forms around its shores and extends outwards

217. for hundreds of miles around the entire land mass

218. Under the sea-ice live small shrimp-like creatures - krill

219. They have been here all winter

220. During these dark months, they feed by scraping algae from the ice

221. Remarkably, they also shrink in size

222. and revert to their juvenile form to save energy

223. As the temperature rises in spring,

224. the ice begins to melt and little air bubbles trapped within it are released

225. Microscopic algae grow around these bubbles and the krill now graze on them,

226. gathering them up with their beating legs

227. As the sun's rays grow stronger and penetrate deeper into the water,

228. floating algae begin to flourish and krill leave

229. the dwindling ice and gather in swarms as they harvest this new crop

230. Far to the north, beyond the blanket of sea ice,

231. chinstrap penguins have been overwintering in the open ocean

232. The occasional iceberg gives them the chance of a rest

233. - if they can get onto it

234. But at this time of year, where they really want to be is on land

235. It's just getting there that's tricky

236. It's spring and the penguins are returning to breed

237. Their need to get ashore is now urgent and imperative

238. Doing so is all a matter of timing - and picking the right wave

239. But their journey has only just begun

240. Most of them will have to walk many miles before they can find a nest site

241. This is Zavodovski Island, which has the largest penguin colony in the world

242. About two million chinstraps breed here

243. - and they come to this island for a good reason

244. It's an active volcano

245. The heat from the crater and the fumeroles

246. keeps the slopes free from the ice and snow,

247. allowing these chinstraps to start breeding earlier than those further south

248. But then again, living on an active volcano is not without its risks

249. Unlike the emperors, these penguins are able to lay their eggs on the bare ground

250. Little wonder so many of them choose to brave

251. the mountainous waves in order to get here

252. Further south, near the continent,

253. the blanket of sea ice is beginning to break up

254. Icebergs are gigantic fragments of ice that have broken away

255. into the sea from the front of glaciers

256. During the winter they were frozen into the sea ice,

257. but now they are set adrift once more

258. As the bergs break up, they form brash ice

259. It litters the backwaters of the Antarctic Peninsula

260. Minke whales make their way into these placid waters in summer

261. This is the most abundant whale in the Southern Ocean

262. Minkes are one of the smallest of all the baleen whales

263. And like all others, they come here to feed

264. The majestic humpback whales are also summer visitors

265. They have travelled thousands of miles from their winter

266. breeding grounds in the tropics to gather the food

267. that becomes available here in summer

268. In just four months, they accumulate enough fat

269. to provide them with energy for the whole of the rest of the year

270. All these animals have come here in search of one thing - the krill

271. Krill is the mainstay of the Antarctic food web

272. It occurs in phenomenal quantity

273. - billions of individuals in a single swarm,

274. and swarms can stretch for miles

275. Fur seals also collect this rich superabundant food

276. Krill swarms are very patchy, but once found, feeding is easy

277. Humpbacks engulf hundreds of thousands of them in a single gargantuan mouthful

278. When the going is good, the whales feed continuously,

279. each eating up to two tonnes of krill in twenty-four hours

280. Further south, near the continent, the sea ice is still sound

281. Here, where the ice remains for most of the summer,

282. emperor penguins make their home

283. These have been feeding out at sea and are now ready

284. to make their way back to the colony to feed their chicks

285. Instead of heading straight for the ice edge,

286. the penguins hesitate some distance from it

287. They're nervous

288. They dive down and investigate the ice edge

289. And for good reason Leopard seals patrol this border

290. Leopard seals are the Antarctic's equivalent of polar bears

291. They are the top predators

292. But they hunt most successfully in the water,

293. so by and large, the animals they prey on are safer out on the ice

294. They have a lazy grace that belies their ferocious nature

295. Confident that the coast is clear, the emperor penguins head for the ice

296. But they certainly don't linger

297. Now they have a long walk back to the colony

298. Emperor penguin colonies are some way back from the ice edge

299. In winter they may be as much as a hundred miles from it,

300. but as the summer progresses and the ice melts,

301. the edge comes ever closer to the colony

302. So by the time the chicks are fledged and ready to take their first swim,

303. the water is close by

304. This colony is in the lee of a headland

305. and that prevents the ice from being broken up by ocean currents

306. The returning adults are so full of food that they can barely walk

307. But with no predator to threaten them now, they can take their time

308. Somehow, in this melee of sixty thousand or so penguins,

309. a parent has to find its chick

310. It returns to the place where it last left its chick in the hope that

311. it might still be close by

312. But chicks tend to wander, so the adult has to call to it

313. The chick responds - and they slowly home in on one another

314. The plaintive entreaties of the chick stimulates

315. the adult to regurgitate a mouthful of fish

316. With the return of one parent,

317. the other is free to go to sea to feed for itself

318. Aware of the leopard seal's presence,

319. the penguins press together at the ice edge,

320. unwilling to be the first to risk diving in

321. Occasionally, the seal comes out onto the ice and attempts to grab one

322. But its most successful strategy by far is to lie in wait

323. It hides behind a corner of ice

324. The emperors gain confidence and make a dash for it

325. The first wave of penguins escape

326. Once in open water, they will be safe

327. But the seal is alerted by the noise, and through the mass of bubbles,

328. it makes its attack

329. Almost invariably, it makes a kill

330. Encouraged by the absence of the seal,

331. the remaining penguins make a break for the open sea

332. In time, their chicks will fledge

333. And when the Antarctic autumn is near its end,

334. these adults will walk across the newly formed ice,

335. to endure yet another winter on the frozen sea