Nature's Great Events E06 - The Great Feast
Transcript
00:00The power of the sun drives the seasons, transforming our planet.
00:13Vast movements of ocean and air currents bring dramatic change throughout the year.
00:23And in a few special places, these seasonal changes create some of the greatest wildlife
00:29spectacles on Earth.
00:36The seas along the Pacific coast of North America can be some of the richest on the
00:41planet.
00:47These coastal waters create the perfect conditions for the greatest explosion of life on Earth.
00:54It's driven by some of the tiniest creatures.
01:00As their numbers multiply, they feed vast shoals of fish, which in turn provide food
01:06for ever larger hunters.
01:12Billions of lives will be shaped by this immense bloom.
01:20And the mightiest hunter of them all has devised a remarkable way to harvest this great feast.
01:50It's January.
02:07Both land and sea are locked in the depths of winter.
02:16The seas along the coast of Alaska and British Columbia can become the richest on Earth.
02:25But for the moment, they lie dormant.
02:30The time of great feasting is many months away.
02:35And a number of magical changes must first take place.
02:42The most crucial change will be driven by the sun.
02:48But now it is weak and offers little to those trapped here for winter.
03:00This coastline, a maze of islands and inlets carved by glaciers, will also shape this great
03:07event.
03:10And now it remains shrouded in cold.
03:16Only the toughest can survive.
03:20Stella's sea lions huddle together to share warmth.
03:26It's just five degrees Fahrenheit.
03:37They have little choice but to suffer this.
03:41The coldest Alaskan winter on record.
03:54The shoals of fish they depend on spend winter in the deepest water.
04:00For now, the fishing is hard.
04:10It's an unforgiving place to raise a family.
04:17Conditions are so severe that mothers must suckle their young for up to three years.
04:33For this pregnant sea lion, the risks are even greater.
04:39The seas must come to life in good time for the arrival of her pup.
04:43And at this stage, the odds don't look good.
04:54For now, all she can do is wait for the sun to bring change.
05:09These seas have the potential to be so rich at the height of the great feast that they
05:13will attract animals from across the vast Pacific.
05:20And 3,000 miles away, in the waters of Hawaii, another mother is about to embark on an epic
05:28journey.
05:38This humpback whale has already given birth.
05:48Her calf is just a few weeks old.
05:54He stays close to his mom.
06:09The difference between Hawaii and Alaska could hardly be greater.
06:22These are calm, warm waters with few predators, an ideal nursery for the youngster.
06:31The calf is now drinking 100 gallons of milk every day, building up strength for the long
06:38voyage he'll soon have to undertake.
06:50More than 5,000 humpbacks come to Hawaii each year.
07:01The males, lured here in the hope of mating, compete among themselves with great shows
07:06of strength.
07:28But none of these whales can actually feed here.
07:33For these tropical waters are comparatively lifeless.
07:43The ocean's greatest riches are only to be found in colder seas, so all these whales
07:50must return to the North Pacific to feed.
07:59The playful calf suckles from his mother every day, but she hasn't had anything to
08:07eat since she left Alaska over four months ago, and she won't feed again until she returns.
08:23The pregnant sea lion, this mother has to get her timing right.
08:30She must arrive in Alaska for the moment when the seas are at their richest, full of fish.
08:40The journey north will take three months.
09:09Back in Alaska, the seas are starting to awaken.
09:17It's March, and as the sun gathers strength, winter loosens its grip.
09:30For the sea lions, things are beginning to look up.
09:37The sun is drawing life from the depths.
09:51With each passing day, the sun warms the water for longer, penetrating deep into the mineral-rich
09:58waters.
10:02Fertilizing nutrients of phosphorus and nitrogen fuel a miraculous change that is just beginning.
10:14Empty seas start to come to life.
10:23As we enter an enhanced view of this microscopic world, we see the beginnings of a magical
10:30transformation.
10:32Phytoplankton, tiny floating plants, emerge.
10:45Each is scarcely bigger than a speck of dust, but together these plankton will bloom in
10:52such immense numbers that they transform lifeless seas.
11:01And whether that will happen this year is yet to be determined.
11:14All creatures here, from the sea lions to the migrating whales, ultimately depend on
11:20these miniature plants.
11:26For one creature that relies directly on the plankton, this is the moment to emerge.
11:37Pacific herring have spent the winter in the depths of the fjords, but they now rise up
11:43and head for the shallow coast.
11:47Stimulated by the sun and the warming water, they gather in their hundreds of millions.
11:56But they're not drawn here to feed.
12:02They're following an irresistible urge to breed.
12:11Groups of males sweep through the shallows and release their sperm in vast milky clouds.
12:24The females follow, covering the seabed with eggs.
12:33Such a concentration of fish is just what the sea lions have been waiting for.
13:04The herring won't be here for long.
13:10The sea lions must make the most of the fishing while it lasts.
13:20Other predators gather, also hungry after the lean winter.
13:30This short-lived bounty is a magnet for millions of migrating birds.
13:38This is just the first brief course in the great feast.
14:03The herring's spawning will be over in a matter of days, and the shoals of fish will
14:09then scatter along the coast.
14:16The herring have spawned on an astonishing scale.
14:23They turn hundreds of miles of coastline white with spawn.
14:30In this bay alone, they have laid 800 billion eggs.
14:45The herring's spawning is so timed that when the next generation hatch in a few weeks,
14:50they'll be able to feed on the growing plankton.
15:02And this year, the herring appear to have timed it just right.
15:10The minute plant plankton, the driving force behind the sea's transformation, are starting
15:16to bloom.
15:19Great swathes of sea grow green with life.
15:30The humpbacks are still out in the middle of the Pacific.
15:37They've missed the first taste of the great feast.
15:43But at just eight weeks old, the young calf must cross the biggest ocean in the world.
16:00His mother will only swim as fast as her young calf.
16:06As he tires, she supports him from beneath.
16:33She's been living off her fat reserves for the last six months, and has lost a third
16:39of her body weight.
16:45She's close to starving.
16:56It will be a further two months before mother and son reach their feeding grounds in the
17:02North Pacific.
17:09It's May, early summer in Alaska, and the days are getting ever longer.
17:19The sun continues to fuel the growth of microscopic plants that make up the plankton bloom.
17:32They're joined by a growing community of tiny animals, zooplankton.
17:44These are the first creatures to feed on the bloom.
17:58Over the coming months, they will multiply, crowding the surface waters in their trillions.
18:04The next stage of the great feast is underway.
18:22All life here depends on this plankton bloom.
18:32The herring feed on it directly.
18:35The greater the bloom, the more abundant the shoals.
18:45And the fish themselves become food for the larger hunters.
18:55But the shoals of herring are now spread far and wide, and once again, for the sea lions,
19:01the fishing is tough.
19:05They must venture further to find food.
19:10But open water is a risky place to fish.
19:19This male sea lion hunts alone.
19:23He's ten feet long and over 2,000 pounds in weight.
19:29Few would dare tackle him.
19:49The smaller females travel as a group, keeping a watchful eye in all directions.
19:59They know that killers lurk in the depths.
20:05The surface is a dangerous place to linger, especially if you're alone.
20:24Orca, killer whales.
20:44The sea lion is wounded, but the killers keep their distance.
20:51His powerful jaws are still a threat to the hungry orca.
21:00He struggles towards the safety of land.
21:12But his injuries are slowing him down.
21:41Blow by blow, they wear him down.
21:58It's a carefully coordinated attack.
22:06One killer distracts his attention while another hits his soft underside.
22:34The richest seas on Earth can be treacherous.
22:44Orca attacks, although savage, have little impact on the fate of most sea lions.
22:58Their survival depends more on the tiny plankton that sustains the great shoals of fish on
23:04which they feed.
23:14It's now late May.
23:16The sunlight lasts for 17 hours a day.
23:24But the bloom will need more than just sun if it's to reach its full extent.
23:39Nutrients held in these waters are continuously used up as the bloom increases.
23:48If they're exhausted too early, the plankton will die and the food chain will collapse.
23:54The effects will be felt by all.
24:01Meanwhile, on the sea lion colony, new life is now arriving.
24:11After a year carrying her pup, this mother can at last give birth.
24:35The pup is utterly dependent on his mum.
24:40As he makes sense of his new world, she encourages him to take his first feed of milk.
24:52The mother has waited until early summer to have her baby.
24:56Such a small pup would never survive the winter.
25:03Along this coast, thousands of pups are born within a matter of weeks, timed to coincide
25:09with the better conditions that may lie ahead.
25:32The migrating humpbacks are still weeks away from Alaska and their first meal.
25:43In these turbulent seas, mother and calf must stay close.
26:01A huge Pacific storm is brewing and heading straight for the coast of British Columbia.
26:26Directly in its path lies the sea lion nursery.
26:33The pups are now at the mercy of the elements.
26:45The mothers must get their young to the safety of higher ground, if they can find it.
27:03In desperation, a mother tries to drag her pup away from the gathering tempest.
27:33A pup swept into the water is unlikely to be seen again.
28:03As the seas begin to subside, many have survived, but others have not.
28:33There's nothing this mother could have done to save her pup.
29:01These mighty storms, though devastating for some, bring fresh life to the great feast.
29:25When these storms hit the coast, they stir up vital nutrients into the surface waters,
29:30nutrients that feed the plankton.
29:35Replenished seas combined with the lengthening days to create a plankton explosion.
29:45And this has come just in time for those at the end of an incredible journey.
30:07The humpbacks have arrived.
30:20After 3,000 miles, mother and calf have finally made it to the coast of Alaska.
30:35There are other whales that have also made the long voyage.
30:39But their journey isn't over, for they have yet to feed.
30:49They're heading for a particular stretch of coast deep in the network of channels,
30:54where they know they can find the great shoals of herring.
31:01It's to these ancestral feeding grounds that the mother now guides her new calf.
31:12The unique geography of this coastline holds the final secret to this great event.
31:24Glaciers have carved a landscape of deep fjords and islands over tens of thousands of years.
31:38This patchwork creates a labyrinth through which powerful ocean and tidal currents flow,
31:46bringing up the vital raw ingredients needed for the bloom.
31:51It's as if an endless supply of fertilizer is being added to the water.
32:00In other seas, the plankton would be subsiding by now.
32:05But here, the seas are repeatedly invigorated,
32:09which fuels the plankton bloom time and again throughout the summer.
32:19With the sun at its most powerful,
32:21all these elements combine to create a plankton bloom of great intensity.
32:31In July, the ocean is alive.
32:38This floating community of plants and animals is the basis for all life here,
32:45and a bloom of this intensity signals the start of a truly great feast.
32:55Where this rich soup hits the seedbed, life carpets every available surface.
33:13The feasting begins with millions of tiny mouths.
33:24Barnacles sift morsels of plankton brought in on the currents.
33:31Many of these creatures started their lives as part of the plankton
33:35before reaching adulthood and settling on the seafloor.
33:46These animals are giants.
33:48They filter the plankton-rich water, growing larger here than anywhere else in the world.
34:04Jellyfish gather, forming great swarms.
34:16They too eat the plankton, rising to the surface where it is at its most abundant.
34:33By late summer, the plankton bloom is so vast it radiates across the North Pacific.
34:44Blooms like these provide Earth with over half of its oxygen.
34:51This bloom eclipses even the Amazon rainforest in sheer abundance of plant life.
35:03And it is most intense where the ocean streams through the maze of coastal waterways.
35:15The shoals of herring are now at their most plentiful.
35:27After feeding through the summer months, the fish themselves are a good catch,
35:32the main target for predators now gathering here.
35:50After enduring the bitter winter, the sea lions can enjoy the bounty they've been waiting for.
36:12Hunting together, they drive the herring to the surface.
36:30Then, with mesmerizing grace, they pick off fish one by one.
37:00For a few short weeks, they'll have their share of the great feast.
37:16Others arrive to feed in the coastal waterways.
37:27Pacific white-sided dolphins.
37:35They dart in and snatch fish as they go.
37:43The tidal currents now sweep herring up to the surface.
37:56Here, they're within diving range of seabirds.
38:06Murs are the first to find the fish.
38:15The shoal twists and turns, trying to escape the surface dangers.
38:31But murs are so fast, they can even out-swim the herring.
38:37They head off the escape, making the shoal turn in on itself, creating a bait ball.
38:50The birds corral the herring into an ever-tighter ball.
39:00But the commotion hasn't gone unnoticed.
39:07Gulls, ever the opportunists, are the next to turn up.
39:18They can only dive down three feet, so the fish are still out of reach.
39:27The murs only attack from beneath, trapping the fish against the surface.
39:39But they push the herring within range of the gulls.
39:46It's a feeding frenzy.
39:52The table is set for the mightiest predator of them all.
40:08The humpbacks have reached their feeding grounds.
40:14After six months without a bite to eat, the humpbacks can finally eat.
40:22But the herring are still hungry.
40:28After six months without a bite to eat, the humpbacks can finally break their fast.
40:46The whales have learned to target these ready-made balls of fish.
40:58But they'll need more than just a mouthful, and with the feast now in full swing, this is their chance.
41:18To exploit the vast shoals of herring that are in deeper water, they rely on teamwork.
41:26For these whales have developed a truly remarkable way of hunting.
41:34The inlets echo to the sound of a mysterious song.
41:42The inlets echo to the sound of a mysterious song.
41:58A curtain of bubbles and the haunting call hold the secret to an enigma.
42:12A ingenious way of fishing.
42:18This is bubble net feeding.
42:24This is bubble net feeding.
42:46A dozen whales work together to harvest the herring bonanza.
42:54A dozen whales work together to harvest the herring bonanza.
43:04Such fishing requires an extraordinary level of intelligence and cooperation.
43:12The lead whale dives first. She is the bubble blower.
43:18It's her job to find the fish.
43:24The rest follow in formation.
43:33Each takes exactly the same position in every lunge.
43:39Once she's located the fish,
43:49the leader blows a net of bubbles that completely encircles the shoal.
44:02Another whale calls to synchronize the group.
44:09They're all in sync.
44:27Panicked by the eerie sound and the blinding bubbles, the fish won't cross this fizzing curtain.
44:39They're all in sync.
44:49They're all in sync.
45:01They're all in sync.
45:09They're all in sync.
45:22As few as a hundred humpbacks have learned how to feed as a team like this.
45:39And this is the only place on the planet where whales fish in this way.
45:56At the height of the summer, these humpbacks fish around the clock,
46:02each eating a thousand pounds of herring a day.
46:09Only man has learned to exploit the seas on a greater scale.
46:30As the summer ends, the feast draws to a close.
46:39The sun is weakening, and with it, the plankton bloom subsides.
46:49The microscopic plants that brought life to empty seas begin to die.
47:01The herring descend to spend the winter in the depths.
47:09Life for the sea lions will be harder once again.
47:23But they fed well enough to face the dark days ahead.
47:39The humpback whales will soon leave these shores.
47:51It's astonishing to think that some of our world's mightiest creatures
47:57ultimately rely on some of its tiniest.
48:09Here, along the North Pacific coast, the interplay between land, sea and sun
48:15has produced a bloom of plankton so immense
48:19it has created one of nature's great events.
48:39To capture the spectacle of the great feast,
48:45the team would face many challenges, none greater than filming it underwater.
48:51It was the lead to some surprising encounters.
48:57The crew had three weeks in late summer
49:08to try to film all the underwater drama.
49:16They wanted to find the bait balls of herring that occur here
49:20in the hope of discovering exactly how the different predators round them up.
49:27Cameramen Shane Moore and David Reichert
49:31both have years of experience working here,
49:35but even they were in for a big surprise.
49:41The key to filming the bait balls was to first find the predators.
49:49We're looking for gulls because the gulls tell us
49:53where the diving birds are that are pushing the herring up.
49:57So usually our first clue to the good action
50:01is just distant gulls in the air.
50:05A lot of diving birds though, the murres are all here and the auklets.
50:09So they're the ones that bring it all together.
50:11So they're all here, so we just have to watch it.
50:17Something, I think that's some bait right there.
50:21It won't last long, so the crew had to get to this one quickly.
50:31But once in the water, a very careful approach is called for.
50:41So as not to panic the birds, David eased closer to the action.
50:51And with this sensitive approach,
50:55the birds stayed focused on the feeding frenzy,
50:59giving David the chance for a rather close-up view.
51:09But with so many predators, the fish were getting hammered.
51:13The bait ball was gone within minutes.
51:17It was an encouraging start, but to get the full sequence they hoped for,
51:21the crew would need to film more bait balls.
51:25And, of course, they weren't the only ones looking for herring.
51:38It's only in the last five or six or seven years
51:40that the humpback population here has grown.
51:44And this area has increased, which is really encouraging.
51:48Look, you can see one way over there.
51:55It was good to see the whales return,
51:57but it posed an intriguing safety concern for Shane.
52:01I think it's extremely unlikely that you could get swallowed by a whale,
52:05but if there is a place, this is the place to do it,
52:08because they're coming up, they're very motivated to get this ball of fish,
52:12and we're right there, and we're just a little thing to a 30-ton whale.
52:16The good news is I've seen whales swallow birds and other things,
52:19even big fish that they don't like, and they stop and spit it out.
52:22So just way, way, way in the back of my mind
52:25is the outside possibility that they might swallow David.
52:28You can tell me that.
52:32Mindful that there were whales in the area,
52:35the crew turned their attention to filming the other stars of the great feast.
52:39Stella's sea lions.
52:44The plan was to dive amongst the kelp
52:46and wait for the sea lions to come to them.
52:49We'll go in and try to, like, find a little eddy in there,
52:52cos the animals are just on that point there.
52:58This coast has some of the strongest tidal currents in the world,
53:02essential for fuelling the plankton bloom,
53:05but not so good if you're swimming against them pushing a bulky camera.
53:15The current was getting stronger
53:17and the sea lions were nowhere to be seen.
53:24David was forced to admit
53:26that even the best-laid plans don't always work.
53:30That dive was a bit of a mess.
53:32You know, the currents come up so fast around here
53:34that as soon as we got down there and got set up,
53:37the current was going, like, four knots
53:39and we were just hanging on to kelp
53:41and trying to get in to find, like, some sort of an eddy or something
53:46to work in, but we never did.
53:48Finally, we just got washed down.
53:51The team had to wait for the tide to calm down.
53:57And it wasn't just the currents that made for the worst.
54:01It was the currents that made filming sea lions underwater a bit tricky.
54:07What's really kind of driving us crazy here is all this plankton.
54:10The water's very green.
54:12I don't know, like the tropics where it's, you know, clear and beautiful,
54:15but it's also what feeds everything here and that's why we have
54:19a great amount of sea lions and all the fish and vertebrates.
54:24On the next slack tide,
54:26it was back into the soupy water to try again.
54:31They'd have to settle down on the seabed
54:33and hope the sea lions' inquisitive nature would draw them in.
54:40And this year's youngsters were definitely not camera shy.
54:49The sea lions were obviously comfortable
54:52getting up close and personal with Shane.
54:57Sometimes even a bit too personal.
55:01The sea lions were not.
55:11Even this ten-foot-long male seemed to want his share of the limelight.
55:22After success with the sea lions,
55:24it was time for Shane and David
55:26to turn their attention back to the bait balls.
55:31The strengthening tides were bringing more fish to the surface
55:34and so, with just a few days left,
55:37this was their best chance to get the shots they still needed.
55:54The birds were gorging on herring.
55:57But at least one fish had a lucky escape.
56:01The herring, of course, in a panic,
56:03looked for a place to hide and they found my camera.
56:06So they'd be up in my viewfinder
56:08and, of course, they'd get in between those tubes there
56:10because everything is trying to eat them.
56:13The murres and everything.
56:16There he is.
56:17There he is.
56:18Okay.
56:19So, let's see.
56:21This might be the lucky one.
56:31Big ball of fish.
56:34It was the best year for bait balls that David and Shane had ever seen.
56:41And they discovered how each of the predators feeds.
56:44It's the murres that corral the bait ball against the surface,
56:48only ever attacking from beneath,
56:50while the gulls just grab what they can.
56:53But no-one was prepared for what happened next.
57:08And David was right there.
57:12So, what's it like to find yourself that close to a feeding humpback?
57:17Everything was hitting the wall.
57:19I could hear the seagulls, of course.
57:21They were all around.
57:22I said, boom, I got quiet.
57:23And they all lifted off and I was like, hmm.
57:25And then, sure enough, all the murres dropped out the bottom.
57:28And he was right there, right when I got real close.
57:31I was like, ah!
57:33His mouth was just...
57:45Scary?
57:46Yeah.
57:48Scary?
57:49Yeah, it was scary.
57:53To capture such astonishing images, and for the very first time,
57:57was an unforgettable experience.
58:01Sitting beside that bait ball, and there's that moment of tension,
58:05and that whale just came roaring through there.
58:08And, you know, that's something that's going to stay with me forever.
58:18Shane and David had revealed a dramatic new way
58:22that humpback whales take advantage of the Great Feast.
58:47The Great Feast