- 1. The world's greatest wilderness,
- 2. the open ocean.
- 3. It covers over half
the surface of our planet.
- 4. Here, there is nowhere to hide
- 5. and little to eat.
- 6. It's the marine
equivalent of a desert.
- 7. And patrolling this desert,
- 8. They stick together.
- 9. In a super pod, 5,000-strong.
- 10. That maximises their chances
of finding something to eat.
- 11. Like all who live here,
- 12. they must go to extraordinary lengths
- 13. to make their home in the big blue.
- 14. There are rare moments
- 15. when these empty seas
can explode with life.
- 16. Lanternfish off the Pacific Coast
of Costa Rica.
- 17. They're scarcely bigger than minnows.
- 18. But what they lack in size,
- 19. they make up for in numbers.
- 20. They are one of the most
numerous fish anywhere.
- 21. Normally they only come
to the surface at night
- 22. to feed on plankton.
- 23. But this immense shoal
has risen during the day,
- 24. almost certainly in order to spawn.
- 25. For the dolphins,
this would be a bonanza.
- 26. They have located the shoal
using their echo-sounding calls.
- 27. But they
have to get to it quickly.
- 28. They are not the only hunters here.
- 29. Yellowfin tuna have also
detected the shoal.
- 30. And behind them,
with their two-metre wingspans,
- 31. Mobula rays.
- 32. Now sailfish,
- 33. one of the fastest fish in the sea,
have joined the chase.
- 34. The lanternfish may return
to the deep at any moment.
- 35. But now, the dolphins have got here.
- 36. They swim beneath the shoal,
pinning it to the surface
- 37. and forcing the lanternfish
to pack more closely together.
- 38. And now the sea begins to boil.
- 39. The tuna charge into
the shoal at over 40 miles an hour.
- 40. The slower swimming rays arrive at last.
- 41. With their immense mouths agape,
- 42. they scoop up the lanternfish
by the hundred.
- 43. The shoal has now
been largely dispersed,
- 44. and the sailfish pick off the survivors.
- 45. In just 15 minutes,
- 46. all that's left
is a silvery confetti of scales.
- 47. But here, such feasts
are only too infrequent.
- 48. Whilst the dolphins perform
great feats of endurance,
- 49. others are driven
to even greater extremes
- 50. to find food in this ocean desert.
- 51. A sleeping giant.
- 52. A sperm whale.
- 53. This family is resting
between bouts of feeding.
- 54. Who knows what the owners
- 55. of the biggest brain
in the planet dream about.
- 56. One has a calf.
- 57. It's about two weeks old, but still
dependent on its mother's milk.
- 58. It's hungry.
- 59. It communicates with
its mother using a pattern of clicks.
- 60. But its mother slumbers on.
- 61. The calf,
covered in suckerfish,
- 62. of which it can't yet rid itself,
- 63. has to be patient.
- 64. Sleep over, and refreshed,
- 65. the whales move on.
- 66. Sperm whales don't wait for their prey
to rise to the surface.
- 67. They swim down
into the depths to find it.
- 68. They take a series of heavy breaths...
- 69. to saturate their blood with oxygen.
- 70. Then, down they go.
- 71. This entire family
dives together in search of squid.
- 72. The mother will push her body
to the limits of her endurance,
- 73. and already it's hard for her calf
to keep up with her.
- 74. The calf sticks to its mother
as closely as it can
- 75. touching her frequently
- 76. as if for reassurance.
- 77. But 500 metres down,
- 78. it seems the calf
can't hold its breath any longer.
- 79. In their early years,
calves are forced to sit out the hunt.
- 80. The adults continue their dive.
- 81. The mother changes her calls
- 82. into a series of louder
and more rapid clicks.
- 83. She's now using sonar
to hunt down shoals of squid.
- 84. At 800 metres, a burst of clicks.
- 85. Then, silence.
- 86. She's made a catch.
- 87. The hunters could be away
for as much as an hour.
- 88. Finally, the mother
returns from the deep
- 89. with a stomach full of squid.
- 90. After a long wait,
- 91. this hungry calf can take some milk.
- 92. It's one of the richest
produced by any mammal.
- 93. And the calf guzzles
a bathful of it a day.
- 94. It may be six years before a calf
masters the art of deep diving
- 95. and is able to find food for itself.
- 96. The emptiness of the big blue
is what makes life so hard for hunters.
- 97. But it's this emptiness
- 98. that makes it
comparatively safe for prey.
- 99. A baby turtle, hatched just days ago,
- 100. is leaving the crowded,
dangerous waters of the coast,
- 101. and heading for the open ocean.
- 102. Only recently have we
begun to solve the mystery
- 103. of where baby turtles disappear to
in their early years.
- 104. To start with, they fill
their little stomachs with plankton.
- 105. But soon, they need
something more substantial.
- 106. Hundreds of miles offshore,
in every ocean,
- 107. there are communities
of young castaways.
- 108. So, anything
that floats attracts them.
- 109. A Ivy-
- 110. It may have been
at sea for several years,
- 111. and it has already become
the centre of a small community.
- 112. Young pufferfish are here
for the same reason.
- 113. A floating log
is just the kind of refuge
- 114. this young turtle has been looking for.
- 115. Here, there's not only seaweed
on which to graze,
- 116. but barnacles.
- 117. But it's important to stay undercover.
- 118. A young ocean-going
silky shark is here too.
- 119. It's learning what tastes good,
- 120. and what doesn't.
- 121. We now know
that many young turtles
- 122. stay in such places for several years
- 123. until adulthood.
- 124. Even if it means facing
the full force of the high seas.
- 125. The sun, beating down
on the deep blue,
- 126. warms the surface waters
so that they evaporate.
- 127. As the vapour rises,
it condenses into clouds.
- 128. They rapidly build into
gigantic burgeoning towers,
- 129. which eventually
generate violent storms,
- 130. some a thousand miles across.
- 131. Hurricane force winds
sweep across the open ocean,
- 132. building waves
that could rise to 30 metres tall.
- 133. Out here, ships have been
known to sink without trace.
- 134. One hundred
and thirty million containers
- 135. are shipped across
the oceans every year.
- 136. And on average, four of them
fall into the sea every day.
- 137. In 1992,
- 138. a few were lost that contained
a consignment of bath toys,
- 139. including 7,000
plastic ducks like these.
- 140. They started their travels
a thousand miles off Alaska.
- 141. Some drifted
right across the Pacific Ocean,
- 142. and reached Australia.
- 143. Others were carried north,
- 144. and landed on shores
between Russia and Alaska.
- 145. They even found their way
into the high Arctic.
- 146. One duck,
having been at sea for 15 years,
- 147. and crossing three oceans,
- 148. eventually landed
on the west coast of Scotland.
- 149. Their travels vividly illustrate
- 150. how a network of currents
connects all our oceans
- 151. into one gigantic circulatory system.
- 152. Many of the inhabitants of the big blue
- 153. rely on these currents
to carry them to feeding grounds.
- 154. The blue shark.
- 155. It travels over 5,000 miles a year,
- 156. riding on the currents,
- 157. supported by its broad wing-shaped fins.
- 158. This one may not
have eaten for two months.
- 159. But the currents can carry
promising traces of fatty oils
- 160. from many miles away
- 161. and will lead it to its next meal.
- 162. After days of travel,
the smell of food gets stronger.
- 163. A dead whale,
recently struck by a ship.
- 164. This could be a real feast,
- 165. but the blue shark must be cautious.
- 166. Great white sharks,
- 167. ten times heavier than the blue,
- 168. are highly possessive
around a whale carcass.
- 169. Great whites are eager
to feed on energy-rich whale blubber,
- 170. which we now know
forms a major part of their diet.
- 171. Once the great white has had its fill,
- 172. smaller sharks, like the blue shark,
- 173. tackle what's left of the carcass.
- 174. As the oils from this dead whale
spread more widely,
- 175. more and more blue sharks appear.
- 176. Within days, the carcass
will be stripped of its blubber.
- 177. Then, no longer kept buoyant by its oil,
- 178. it will sink into the depths below.
- 179. The blue, with its reserves
of fat replenished,
- 180. can now survive
for another two months without eating.
- 181. Over half of all animals
in the open ocean
- 182. drift in currents.
- 183. jellyfish cross entire oceans
- 184. feeding on whatever happens
to tangle with their tentacles.
- 185. Some can grow to a metre,
even two metres across.
- 186. And when, by lucky chance,
- 187. they encounter
a patch of sea rich in plankton,
- 188. their numbers explode.
- 189. It's such a successful strategy,
- 190. that jellies are one of the most
common lifeforms on the planet.
- 191. But among the jellies,
- 192. and looking somewhat like them,
- 193. is a rather more complex
and sinister creature.
- 194. The Portuguese man 0' war.
- 195. It floats with the help
of a gas-filled bladder,
- 196. propped by a vertical membrane.
- 197. With that serving as a sail,
- 198. it maintains a steady course
through the waves.
- 199. Long threads trail behind it,
- 200. some as much as 30 metres long.
- 201. Each is armed with
many thousands of stinging cells.
- 202. A single tentacle could kill a fish,
- 203. or, in rare cases, a human.
- 204. But among its lethal tentacles,
- 205. lurks a man 0' war fish
- 206. that feeds by nibbling them.
- 207. Whilst this fish
has some resistance to the stings,
- 208. it must still be extremely careful.
- 209. Most other fish are not so lucky.
- 210. A tentacle has caught
this one, and reels it in.
- 211. It's already paralysed.
- 212. Specialised muscular tentacles
- 213. transfer the victim to others
that digest the catch,
- 214. liquefying it with powerful chemicals.
- 215. Eventually all that is left
- 216. is a scaly husk.
- 217. This voracious man 0' war
- 218. may collect over a hundred
small fish in a day.
- 219. For the most part,
the big blue seems featureless.
- 220. A place where the winds blow,
uninterrupted by land.
- 221. But beneath the surface,
- 222. there are long
mountain ranges, deep trenches,
- 223. and isolated volcanic peaks
- 224. that make it far more varied
than the human eye can see.
- 225. We're only just discovering
in any detail
- 226. how the inhabitants
of the big blue exploit that.
- 227. A lonely whale shark
- 228. on a special journey.
- 229. She is as long as a small aircraft,
- 230. and she weighs over 20 tonnes.
- 231. Like many sharks, she does not lay eggs,
- 232. but gives birth to live young.
- 233. She carries up to 500 of them
- 234. in her swollen belly.
- 235. She may be the biggest fish in the sea,
- 236. but the place where whale sharks
give birth has not yet been found.
- 237. Today, however, we may be a step
closer to solving this mystery.
- 238. We have known
that great numbers of whale sharks,
- 239. at certain times of the year,
- 240. appear around the Galapagos Islands.
- 241. Here they assemble around a tiny islet
- 242. that rises abruptly
from particularly deep water.
- 243. It's known as Darwin Island.
- 244. Here, swirling currents
bring out nutrients from the deep,
- 245. so enriching these waters
- 246. that they attract
great concentrations of fish
- 247. from far and wide.
- 248. Thousands of hammerhead sharks
also assemble here.
- 249. They are nearly all female.
- 250. They, too, it seems,
have come here to breed.
- 251. The whale shark receives
an extraordinary welcome.
- 252. Silky sharks,
themselves three metres long,
- 253. bounce against her rough skin,
- 254. perhaps to scrape off
any parasites they might have.
- 255. These sharks could be a danger
to any newly-born young.
- 256. So, perhaps to avoid them,
- 257. the whale shark dives
- 258. down to around 600 metres.
- 259. And there, she may release her young.
- 260. In these great depths,
- 261. away from the predators
that hunt in the waters above,
- 262. and with abundant food,
- 263. her babies could grow
and eventually disperse.
- 264. No one, it is true,
- 265. has ever seen young ones
in these little-visited depths.
- 266. But the fact that hundreds
of expectant whale sharks
- 267. come here every year,
- 268. is strong evidence that somewhere here
- 269. lies the nursery
of the biggest fish in the sea.
- 270. There are almost 50,000 sizeable islands
- 271. scattered across the world's oceans.
- 272. One of them is South Georgia.
- 273. An ideal place for those ocean-dwellers
- 274. who are compelled to land
in order to breed.
- 275. The wandering albatross.
- 276. It may spend as much
as a year continuously at sea,
- 277. searching for food,
- 278. gliding on wings that are
three and a half metres across.
- 279. The biggest of any living bird.
- 280. The entire world population
- 281. of 76, 000 Wanderers
nest on South Georgia
- 282. and half a dozen or so
of the other smaller islands
- 283. that lie in the Southern Ocean.
- 284. It's spring.
- 285. And this bird is returning
to the nest site it has always used.
- 286. Its lifelong partner is already here.
- 287. In South Georgia,
- 288. individual birds have been
studied for their entire lives
- 289. revealing that older pairs
in their late thirties
- 290. will go to extraordinary lengths
- 291. to give their young
the best possible start in life.
- 292. This chick is now several weeks old,
- 293. but still has its warm, downy coat.
- 294. The chick will need a regular
supply of regurgitated fish and squid.
- 295. With food so scarce in the open ocean,
- 296. both parents may have to scour
thousands of square miles
- 297. just to provide enough for one meal.
- 298. Ageing parents struggle on
all through the Antarctic winter,
- 299. to raise a chick that is big,
strong and healthy.
- 300. After some 130 days,
- 301. the youngster begins to replace
its down with flight feathers.
- 302. Finally, nine months
after their egg was laid,
- 303. this chick is ready to leave.
- 304. Of all the chicks
they've reared in recent years,
- 305. such a favoured chick
will have the best chance of survival.
- 306. But it will also be their last.
- 307. Elderly parents never recover
from their exertions.
- 308. They will soon leave this island,
- 309. never to be seen again.
- 310. Surviving in the open ocean
- 311. has always tested animals to the limit.
- 312. But today, they face a new,
- 313. Plastic.
- 314. just over a hundred years ago,
- 315. we invented a wonderful new material
- 316. that could be moulded
into all kinds of shapes.
- 317. And we took great trouble to ensure
- 318. that it was hard-wearing, waterproof,
- 319. and virtually indestructible.
- 320. Now, every year,
- 321. we dump around eight million
tonnes of it into the sea.
- 322. Here, it entangles and drowns
vast numbers of marine creatures.
- 323. But it has even more widespread
and far-reaching consequences.
- 324. A pod of short-finned pilot whales.
- 325. They live together in,
what are perhaps,
- 326. the most closely-knit of families
in the whole ocean.
- 327. Today, in the Atlantic waters
off Europe, as elsewhere,
- 328. they have to share
the ocean with plastic.
- 329. A mother is holding
her new-born young.
- 330. It's dead.
- 331. She is reluctant to let it go
- 332. and has been carrying
it around for many days.
- 333. As plastic breaks down,
it combines with other pollutants
- 334. that are consumed
by vast numbers of marine creatures.
- 335. In top predators like these,
- 336. the toxic chemicals
can build up to lethal levels.
- 337. It's possible her calf
may have been poisoned
- 338. by her own contaminated milk.
- 339. Pilot whales have big brains.
- 340. They can certainly experience emotions.
- 341. judging from
the behaviour of the adults,
- 342. the loss of the infant
has affected the entire family.
- 343. Unless the flow of plastics
into the world's oceans is reduced,
- 344. marine life will be poisoned by them
for many centuries to come.
- 345. The creatures
that live in the big blue
- 346. are, perhaps, more remote
than any animals on the planet.
- 347. But not remote enough, it seems,
- 348. to escape the effects of what
we are doing to their world.
- 349. Next time, we journey
into the bountiful green sea.
- 350. These are enchanted worlds,
- 351. home to strange creatures...
- 352. where only the most ingenious