The Blue Planet 1x4

1. The frozen seas are worlds unto themselves.

2. Beneath their ceiling of ice,

3. they have an eerie, almost magical stillness,

4. cutoff from the storms that rage above.

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

6. and the temperature seldom rises above minus 50 degrees Centigrade.

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

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

9. the Arctic and the Antarctic.

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

11. the winters, when much of the sea is frozen,

12. bring the greatest challenge.

13. The northern hemisphere.

14. It's February,

15. and as the earth tilts on its axis,

16. the sun's rays creep slowly northwards

17. and the Arctic emerges from its harsh winter.

18. The Arctic is a frozen ocean surrounded by continents,

19. and when the surface of the sea between the continents

20. freezes from shore to shore,

21. land predators walk out onto it

22. to hunt.

23. It's early March,

24. and the sea is still covered with ice...

25. But there are patches of open water - polynyas -

26. that never freeze over.

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

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

29. Walruses spend the winter in polynyas.

30. Here they have permanent access to the air,

31. but they can also retreat to the sea to shelter, to hunt.

32. Other sea mammals overwinter in polynyas as well - in this one,

33. a young bowhead whale.

34. Here, the current is really fast

35. and the shifting ice is dangerous.

36. This whale became trapped

37. when ice encircled it last autumn.

38. There is no food here,

39. but a whale must breathe,

40. and the only place it can do so for miles around is in this tiny hole.

41. It's living entirely on its reserves of fat,

42. but now, they're dangerously low.

43. It will be some months yet before it can escape.

44. Elsewhere, other whales have also been trapped.

45. These are belugas.

46. Their tiny hole in the ice

47. has been kept open not by currents,

48. but by the belugas' continuous movements

49. as they rise to breathe.

50. Open water is now some 20 miles away.

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

52. The belugas are extremely thin

53. and most of them are horribly scarred.

54. But their wounds were not inflicted by the ice.

55. A whale would be a huge prize for any meat-eating hunter,

56. and these belugas, trapped by the ice,

57. are within reach of polar bears.

58. Well aware of the danger,

59. the belugas stay submerged as long as they can,

60. but they can only hold their breath for about 20 minutes.

61. Catching a four-meter-long whale that weighs one ton

62. is no easy task,

63. even if that whale is weakened by starvation.

64. But a beluga is well worth waiting for.

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

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

67. Keeping its fur in good condition and free from salt

68. is important for warmth,

69. and the bear uses snow like blotting paper.

70. These belugas have been attacked by many bears

71. over the last six months,

72. and some have been caught.

73. It may have taken a long time and a lot of patience,

74. but a catch when it's made brings abundant rewards

75. of energy-rich blubber.

76. Gulls rely on bear kills at this time of the year,

77. and the color of blood staining the ice

78. attracts them from a long way away.

79. The remaining belugas still have a long wait

80. before they're released from their prison

81. and the threat of slaughter.

82. Arctic foxes also rely on the polar bears

83. to hunt on their behalf.

84. They're the jackals of the north,

85. and scavenge from bear kills whenever they can.

86. In winter and early spring,

87. they're wholly dependent on bears.

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

89. will they regularly catch prey for themselves.

90. They're not strong enough to tackle adult seals,

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

92. This canny individual

93. is going to bury its prize.

94. It may need it during the uncertain times ahead.

95. The presence of bears

96. affects the behavior of almost all the animals here, big and small.

97. The bears tend to avoid the fringe of fragmented ice

98. bordering open water

99. where traveling can be very laborious,

100. but that very fact makes this area - the pack ice -

101. a particularly good place

102. for seals to pup.

103. Harp seals breed here.

104. Their pups are born with white coats

105. which camouflage them very effectively against the snow.

106. Harp seals have a very short nursing period -

107. a necessity on this unstable pack ice -

108. but suckling is intensive.

109. The pup feeds for just 12 days

110. on milk that is 45 per cent fat.

111. Then it's abandoned

112. and has to fend for itself.

113. A male hooded seal.

114. This impressive nasal display

115. is used to warn away other males...

116. and to win a mate.

117. Hooded seals also breed on pack ice.

118. Their pups suckle for only four days,

119. the shortest nursing period known for any mammal,

120. and all because the threat of polar bears

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

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

123. these ringed seals must be particularly vigilant

124. and have to hide their pups.

125. Ringed seals are comparatively small,

126. so they can give birth to their pups

127. in little caves or lairs under the snow.

128. Here, a pup is out of sight

129. and protected from bad weather.

130. In late March and into April,

131. female bears emerge from winter dens with their new cubs.

132. The mother has not eaten for at least five months

133. and she's hungry - very hungry.

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

135. her milk will fail

136. and her cub will die.

137. Bears have an extraordinarily sensitive sense of smell

138. and can detect seal pups hidden in the snow

139. from two kilometers away.

140. But a female ringed seal uses several lairs

141. and a bear will have to break into a number

142. before it finds one that is occupied.

143. This is a crucial time for the cub.

144. By watching its mother hunt

145. and by copying her actions, it's beginning to acquire the rudiments

146. of its own hunting skills.

147. Play is also important for developing muscles

148. and improving co-ordination.

149. As the days go by,

150. the sun rises higher and remains above the horizon even at night.

151. The female bear continues to hunt

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

153. She's smelt something.

154. The pup escapes through a hole in its lair

155. that leads to the sea below.

156. Only one in 20 hunts is successful,

157. but this mother must find a seal pup soon

158. if her cub is not to starve to death.

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

160. Now, the ocean is accessible

161. and the Arctic's summer visitors return.

162. Migrating birds

163. arrive from the south

164. to nest and feed on the seafood now within their reach.

165. Brunnich's guillemots

166. are the northern equivalent of penguins,

167. but they have retained the power of flight

168. for they need to reach cliff ledges

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

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

171. They dive down to a depth of 50 meters or more

172. to catch fish.

173. In June, the ice begins to fracture.

174. The cracks - or leads -

175. form useful corridors of open water

176. for air-breathing animals.

177. Belugas, migrating to their feeding grounds,

178. use these leads to penetrate the ice-covered seas and reach areas

179. where their preferred food, Arctic cod, has spent the winter.

180. The males regularly dive to about 500 meters to find fish.

181. The females and young, which have smaller lungs,

182. only go to about 350.

183. In late June and July, narwhals arrive.

184. The females, who usually lack tusks,

185. come first with their new calves.

186. The males follow a little later.

187. They also move up the leads

188. in search of fresh feeding grounds.

189. Bowheads. Up to 18 meters long

190. and weighing 100 tons.

191. These are the only large whales

192. that stay in the Arctic all year round.

193. They are not after fish.

194. They're seeking smaller prey.

195. Despite having the largest mouths in the animal kingdom -

196. the size of a small garage -

197. they eat tiny crustaceans - copepods -

198. straining them from the water

199. with the four-meter-long strips of baleen

200. that hang from their upper jaws.

201. In the summer, they store enough energy

202. to last them through the following winter

203. when food will be less abundant.

204. As the ice melts away,

205. the polar bears are forced to head for land.

206. They are excellent swimmers,

207. and can cover 100 miles of continuous open water if need be.

208. Off east Greenland,

209. there is little ice left by August, so walruses haul out

210. to rest on land.

211. At this time of year, they are molting,

212. getting rid of their old, scarred, parasite-ridden skin.

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

214. but even there,

215. the odd scratch is irresistible.

216. They make daily excursions out to deeper water.

217. Down at 20 meters,

218. they root around in the sediment,

219. using their sensitive bristles

220. to search out soft-shelled clams.

221. Once they find a clam,

222. they suck its flesh from the shell

223. with their powerful, muscular mouths.

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

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

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

227. They congregate in just a few large estuaries.

228. Belugas of all ages and sizes come here.

229. There are even young calves.

230. Some are so young -

231. born only a week or so ago -

232. that they need help.

233. They swim on their mothers' backs

234. so that they can breathe more easily.

235. As the tide moves up the estuary,

236. the belugas follow,

237. Like walruses,

238. they also need to molt.

239. A combination of warm fresh water

240. and vigorous rubbing against the gravel does the trick.

241. They remain here for days

242. or even weeks,

243. so it's likely that socializing

244. is also important to them.

245. After molting, they head back out to sea to feed.

246. It's now autumn,

247. and the sea begins to freeze over once again.

248. Thin sheets of ice form at the surface

249. and pile up, layer upon layer,

250. gradually creating an impenetrable barrier.

251. By late November, the Arctic ocean is sealed once again by ice.

252. The lights of the aurora

253. play in the winter sky.

254. And at the other end of the planet - in the Antarctic -

255. there is the southern aurora.

256. Antarctica is now emerging from winter.

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

258. Temperatures are still hovering at a numbing minus 50,

259. and the returning sun has virtually no warmth.

260. Very few animals can survive such extreme conditions...

261. but Emperor penguins can.

262. Standing on the frozen sea,

263. they endure the full force of the Antarctic storms.

264. Only by huddling together

265. can they survive the appalling winter months.

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

267. They can only live here at all

268. because Antarctica is surrounded by the great Southern Ocean

269. and no land predators have been able to reach it,

270. so, unlike Arctic animals,

271. they're not threatened by polar bears.

272. The sea is still frozen,

273. but one seal, nonetheless, manages to stay here,

274. even throughout the winter -

275. the Weddell seal.

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

277. but it must have access to the air all year

278. And they keep their breathing holes open

279. with their teeth.

280. Only by continually scraping away at the ice

281. can they maintain access to the air,

282. but that means that their teeth get badly worn down.

283. Then, they can no longer hunt and eat effectively.

284. Weddell seals die young.

285. The continent of Antarctica

286. is so isolated and so high -

287. almost 5,000 meters in places -

288. that it's considerably colder than the Arctic.

289. Ice slides slowly down from its canter

290. towards its rim in immense glaciers.

291. During winter, the continent effectively doubles in size

292. 6S the sea freezes over.

293. Ice forms around its shores

294. and extends outwards for hundreds of miles

295. around the entire land mass.

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

297. They have been here all winter.

298. During these dark months,

299. they feed by scraping algae from the ice.

300. Remarkably, they also shrink in size

301. and revert to their juvenile form to save energy.

302. As the temperature rises in spring,

303. the ice begins to melt,

304. and little air bubbles trapped within it are released.

305. Microscopic algae grow around these bubbles

306. and the krill now graze on them,

307. gathering them up with their beating legs.

308. As the sun's rays grow stronger

309. and penetrate deeper Into the water,

310. floating algae begin to flourish,

311. and krill leave the dwindling ice

312. and gather in swarms

313. as they harvest this new crop.

314. Far to the north,

315. beyond the blanket of sea ice,

316. chinstrap penguins

317. have been overwintering in the open ocean.

318. The occasional iceberg

319. gives them the chance of a rest-

320. if they can get onto it.

321. But at this time of year, where they really want to be

322. is on land.

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

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

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

326. Doing so is all a matter of timing,

327. and picking the right wave.

328. But their journey has only just begun.

329. Most of them will have to walk many miles

330. before they can find a nest site.

331. This is Zavodovski Island,

332. which has the largest penguin colony in the world.

333. About two million chinstraps breed here,

334. and they come to THIS island for a good reason.

335. It's an active volcano.

336. The heat from the crater and the fumaroles

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

338. allowing these chinstraps to start breeding earlier

339. than those further south.

340. But then again,

341. living on an active volcano is not without its risks.

342. Unlike the Emperors,

343. these penguins are able to lay their eggs on the bare ground.

344. Little wonder so many choose to brave the mountainous waves

345. in order to get here.

346. Further south, near the continent,

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

348. Icebergs are gigantic fragments of ice

349. that have broken away into the sea from the front of glaciers.

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

351. but now they're set adrift once more.

352. As the bergs break up,

353. they form brash ice.

354. It litters the backwaters of the Antarctic peninsula.

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

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

357. Minkes are one of the smallest of all the baleen whales,

358. and like all others, they come here to feed.

359. The majestic humpback whales

360. are also summer visitors.

361. They have traveled thousands of miles

362. from their winter breeding grounds in the tropics

363. to gather the food that becomes available here in summer.

364. In just four months,

365. they accumulate enough fat

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

367. All these animals have come here in search of one thing -

368. the krill.

369. Krill is the mainstay

370. of the Antarctic food web.

371. It occurs in phenomenal quantity -

372. billions of individuals in a single swarm,

373. and swarms can stretch for miles.

374. Fur seals also collect this rich, super-abundant food.

375. Krill swarms are very patchy,

376. but once found,

377. feeding is easy.

378. Humpbacks engulf hundreds of thousands of them

379. in a single gargantuan mouthful.

380. When the going is good,

381. the whales feed continuously,

382. each eating up to two tons of krill

383. in 24 hours.

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

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

386. Emperor penguins make their home.

387. These have been feeding out at sea,

388. and are now ready to make their way back to the colony

389. to feed their chicks.

390. Instead of heading straight for the ice edge,

391. the penguins hesitate some distance from it.

392. They're nervous.

393. They dive down

394. and investigate the ice edge...

395. And for good reason.

396. Leopard seals patrol this border.

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

398. They're the top predators,

399. but they hunt most successfully in the water,

400. so by and large,

401. the animals they prey on are safer out on the ice.

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

403. Confident that the coast is clear,

404. the Emperor penguins head for the ice...

405. but they certainly don't linger.

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

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

408. In winter, they may be as much as 100 miles from it,

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

410. the edge comes ever closer to the colony.

411. So by the time the chicks are fledged

412. and ready to take their first swim,

413. the water is close by.

414. This colony is in the lee of a headland,

415. and that prevents the ice from being broken up

416. by ocean currents.

417. The returning adults are so full of food

418. that they can barely walk,

419. but with no predator to threaten them now,

420. they can take their time.

421. Somehow, in this melee of 60,000 or so penguins,

422. a parent has to find its chick.

423. It returns to the place where it last left its chick

424. in the hope that it might still be close by...

425. but chicks tend to wander,

426. so the adult has to call to it.

427. The chick responds,

428. and they slowly home in on one another.

429. The plaintive entreaties of the chick

430. stimulates the adult to regurgitate a mouthful of fish.

431. With the return of one parent,

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

433. Aware of the leopard seal's presence,

434. the penguins press together at the ice edge

435. unwilling to be the first to risk diving in.

436. Occasionally, the seal comes out onto the ice

437. and attempts to grab one...

438. But its most successful strategy by far

439. is to lie in wait.

440. It hides behind a corner of ice.

441. The Emperors gain confidence

442. and make a dash for it.

443. The first wave of penguins escape.

444. Once in open water, they will be safe.

445. But the seal is alerted by the noise,

446. and through the mass of bubbles, it makes its attack.

447. Almost invariably, it makes a kill.

448. Encouraged by the absence of the seal,

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

450. In time, their chicks will fledge,

451. and when the Antarctic autumn is near its end,

452. these adults will walk across the newly-formed ice

453. to endure yet another winter

454. on the frozen sea.