0:00:02 > 0:00:08Animals can sometimes reach such numbers they defy our understanding.
0:00:08 > 0:00:12They seem to rise up and invade our lives.
0:00:14 > 0:00:17They become Superswarms -
0:00:17 > 0:00:21so immense, they are impossible to ignore.
0:00:24 > 0:00:28From the outside, they can be the stuff of nightmares.
0:00:28 > 0:00:32From the inside, they are a thing of extraordinary beauty.
0:00:32 > 0:00:36Among the apparent chaos, something remarkable is going on.
0:00:36 > 0:00:40A weird kind of intelligence controls the swarm.
0:00:50 > 0:00:52Right now, 8:30 sharp.
0:00:52 > 0:00:54It's like swarms right now,
0:00:54 > 0:00:57you see, they look like black clouds going across the sky.
0:00:57 > 0:00:59At Congress Bridge in Austin, Texas,
0:00:59 > 0:01:02100,000 tourists visit each year
0:01:02 > 0:01:05to watch an incredible natural spectacle -
0:01:05 > 0:01:101.5 million free-tailed bats leaving their roost for the night.
0:01:13 > 0:01:16It's an awe-inspiring sight, that to our eyes looks chaotic.
0:01:19 > 0:01:23Inside the swarm, it's a very different picture.
0:01:24 > 0:01:28The bats fly in perfect unison, always aware of their nearest
0:01:28 > 0:01:31neighbour, chatting together as they stream from the roost.
0:01:31 > 0:01:36The tourists sometimes spot a bird diving among the bats,
0:01:36 > 0:01:37trying to grab a meal -
0:01:37 > 0:01:41this gives even more of a clue as to what is going on.
0:01:42 > 0:01:46Slow down the action and what's happening becomes clearer.
0:01:49 > 0:01:53For the peregrine to succeed, she must single out a bat from
0:01:53 > 0:01:57the masses - an almost impossible task amongst all the confusion.
0:02:03 > 0:02:07A red-tailed hawk tries his luck, but faces the same problem.
0:02:07 > 0:02:09BATS SQUEAK
0:02:11 > 0:02:15The bats' alarm calls warn of danger - they work together.
0:02:19 > 0:02:21They drop like stones from the sky
0:02:21 > 0:02:26- the sudden change of direction wrong-footing their attackers.
0:02:35 > 0:02:38Bats on their own are easier to pick out.
0:02:38 > 0:02:41And there is no-one to watch their backs.
0:02:54 > 0:02:56By sharing information,
0:02:56 > 0:02:59the bats effectively increase their intelligence.
0:03:02 > 0:03:03LOUD SQUEAKING
0:03:08 > 0:03:14Just 60 miles away, at Bracken Cave, a mothers' meeting is taking place.
0:03:17 > 0:03:19Here, female bats gather to give birth.
0:03:19 > 0:03:2540 million bats in all - the largest swarm of mammals on earth.
0:03:25 > 0:03:27The bats migrate to these maternity caves
0:03:27 > 0:03:30from South and Central America.
0:03:33 > 0:03:37It's like a giant creche and the mothers don't stop talking.
0:03:37 > 0:03:41But this isn't idle gossip - they are exchanging information.
0:03:45 > 0:03:50At dusk, the females and young take to the air with a purpose.
0:03:57 > 0:04:02It may seem disorganised, but this is flight school for bats.
0:04:08 > 0:04:11The young learn from their mother how to catch insects.
0:04:11 > 0:04:15Among the millions, she can recognise her own young's call
0:04:15 > 0:04:17and they stay together as they fly.
0:04:32 > 0:04:36At normal speed, you get a sense of how difficult this must be.
0:04:36 > 0:04:40But this Superswarm doesn't exist in any time world we know.
0:04:40 > 0:04:43They react many times faster than we can.
0:04:43 > 0:04:47The older, more experienced females act like scouts,
0:04:47 > 0:04:50leaving the cave first to check that all is clear.
0:04:52 > 0:04:56The novices follow, swirling together to form a bat tornado.
0:05:04 > 0:05:09This vortex grows rapidly, always spinning in the same direction.
0:05:09 > 0:05:13It acts as a beacon, signalling to others that it's time to leave.
0:05:26 > 0:05:29The bats also use the vortex to exchange information.
0:05:29 > 0:05:33They collectively make informed decisions on where they should go,
0:05:33 > 0:05:36based on their experiences from the previous night.
0:05:43 > 0:05:47In this gathering, a kind of swarm intelligence is being created
0:05:47 > 0:05:49and spread among the individuals.
0:06:00 > 0:06:04Other swarms use this behaviour too.
0:06:11 > 0:06:14The vortexes created by fish can be so spectacular
0:06:14 > 0:06:17they appear almost like an alien organism.
0:06:21 > 0:06:23They move like one too -
0:06:23 > 0:06:26a creature that shape-shifts before our eyes.
0:06:41 > 0:06:45Fish have a lateral line system, sensitive to pressure waves,
0:06:45 > 0:06:49that runs like a series of hidden ears along the body.
0:06:49 > 0:06:52This picks up the tiny movements of neighbouring fish so they can
0:06:52 > 0:06:55mirror each other's actions in perfect synchrony.
0:06:55 > 0:06:58The lateral line also detects predators.
0:07:02 > 0:07:05Sailfish are built to deal with this super-organism.
0:07:05 > 0:07:08They are the fastest fish in the ocean.
0:07:08 > 0:07:11But, like birds, they find that dealing with the swarm isn't easy.
0:07:16 > 0:07:19If any member of the shoal detects danger,
0:07:19 > 0:07:21they use pheromones to warn the others.
0:07:21 > 0:07:26With so many individuals on the lookout, their senses are amplified.
0:07:26 > 0:07:29It's difficult for predators to take them by surprise.
0:07:36 > 0:07:42The Sailfish's gameplan is to divide and rule. Smaller shoals are easier.
0:07:51 > 0:07:55They slice through the mass, breaking them into smaller targets.
0:08:14 > 0:08:19But chasing even these mini-swarms is difficult.
0:08:19 > 0:08:22Only the weak or diseased usually get taken.
0:08:26 > 0:08:30The fragmented shoal seeks safety with the master swarm.
0:08:35 > 0:08:38In this fish whirlpool, they communicate by resonating
0:08:38 > 0:08:40their swim bladders or grinding their teeth.
0:08:49 > 0:08:53Together, they become more than the sum of their parts.
0:08:53 > 0:08:57It's as if each fish adds its intelligence to the other,
0:08:57 > 0:08:59to create a single mind.
0:09:03 > 0:09:07The root of such complex behaviour lies with far simpler animals.
0:09:12 > 0:09:14This is Mono Lake in California,
0:09:14 > 0:09:18a hauntingly beautiful location made famous by it's pumice towers.
0:09:23 > 0:09:27Appearances are deceptive - below its calm surface
0:09:27 > 0:09:31is a caustic chemical brew in which almost no life survives.
0:09:31 > 0:09:36Except, that is, for flies. Brine Flies.
0:09:37 > 0:09:40There are billions of them.
0:09:44 > 0:09:47Often so deep they blacken the ground.
0:09:47 > 0:09:50Their young live in the lake and when they emerge,
0:09:50 > 0:09:51they eat nothing but algae.
0:09:59 > 0:10:01Visitors can't help but notice
0:10:01 > 0:10:04the flies' extraordinary swarming behaviour.
0:10:07 > 0:10:10They ripple away from whoever approaches.
0:10:10 > 0:10:12It's a game of chasing shadows.
0:10:23 > 0:10:27Gulls chasing the flies create the same reaction.
0:10:28 > 0:10:31The flies react in a wave,
0:10:31 > 0:10:35sensing their neighbour's movements and reacting instantly.
0:10:39 > 0:10:40Against such organisation,
0:10:40 > 0:10:43the gull's response is about as basic as it gets.
0:10:43 > 0:10:47They open their mouths, run, and hope for the best.
0:11:03 > 0:11:04It's frustrating work -
0:11:04 > 0:11:09for most of the time the flies keep tantalisingly out of reach.
0:11:25 > 0:11:28These apparently simple animals have complex behaviour
0:11:28 > 0:11:30and are capable of learning.
0:11:42 > 0:11:46Working as a swarm, the flies increase their awareness of the world,
0:11:46 > 0:11:49making it difficult for predators to catch them.
0:11:56 > 0:11:59Fortunately, the flies are so high in protein
0:11:59 > 0:12:01the gulls don't actually need to catch that many.
0:12:01 > 0:12:05Just 20 flies a day gives them all the calories they need.
0:12:24 > 0:12:25The flies are so nutritious,
0:12:25 > 0:12:3065,000 Californian gulls come here to breed each year.
0:12:50 > 0:12:54In Rome, yellow-legged gulls also adapt their
0:12:54 > 0:12:55behaviour to feed on a swarm.
0:13:08 > 0:13:12As 10 million starlings stream into the city to roost,
0:13:12 > 0:13:14they outnumber the human residents four to one.
0:13:17 > 0:13:21Each year, these common garden birds of northern Europe
0:13:21 > 0:13:24take a winter break in the warmer south.
0:13:24 > 0:13:27Most are young, inexperienced birds.
0:13:27 > 0:13:31By flocking together, they benefit from each other's knowledge.
0:13:31 > 0:13:37For the gulls, it's like chasing fish shoals in the sky.
0:13:37 > 0:13:40They act like fish shoals too -
0:13:40 > 0:13:42forever changing shape and re-forming.
0:13:50 > 0:13:55The gull attacks, trying to split the flock. The flock regroups.
0:13:55 > 0:13:59The starlings' manoeuvres are too quick for a single predator.
0:13:59 > 0:14:04The gulls try to turn the odds in their favour by working as a team.
0:14:04 > 0:14:08Together, they corral the starlings and try to split the flock.
0:14:08 > 0:14:12But the flock grows more powerful by the minute.
0:14:12 > 0:14:16As more birds join, they gain strength in numbers.
0:14:22 > 0:14:25A peregrine falcon is a greater challenge -
0:14:25 > 0:14:30it reaches 220mph in a dive.
0:14:40 > 0:14:44The starlings snap together in close formation.
0:14:44 > 0:14:45They become a blockade of birds.
0:14:45 > 0:14:48The peregrine risks serious injury if it attacks now.
0:15:00 > 0:15:01The flock is like quicksilver,
0:15:01 > 0:15:05forever splitting and reforming to confuse their attackers.
0:15:08 > 0:15:11It's impossible to target a single bird.
0:15:20 > 0:15:24Like other swarms, birds create this distracting display
0:15:24 > 0:15:26by watching their companions.
0:15:26 > 0:15:28Amazingly, each starling tracks the movements
0:15:28 > 0:15:31of seven of its neighbours at a time.
0:15:35 > 0:15:40By monitoring these seven birds and keeping in formation with them, each
0:15:40 > 0:15:43individual helps keep the swarm as a cohesive force.
0:15:44 > 0:15:49All this happens ten times faster than a human can think.
0:15:56 > 0:15:59We are only just discovering how much information is exchanged
0:15:59 > 0:16:01when birds gather in huge numbers.
0:16:09 > 0:16:13It's May in Delaware Bay on the east coast of America.
0:16:13 > 0:16:16These waders have flown all the way from South America
0:16:16 > 0:16:19to coincide with a very special swarming event.
0:16:20 > 0:16:27As the birds roost, the invasion begins, cued by the cycle of the moon.
0:16:27 > 0:16:31Human visitors usually see them first.
0:16:31 > 0:16:33Well, I tell you, this is creepy...
0:16:33 > 0:16:36not creepy, but just freaky!
0:16:37 > 0:16:39I don't know what they're doing -
0:16:39 > 0:16:42are they battling or something over a female? Holy mackerel!
0:16:42 > 0:16:45Here's a guy swimming along.
0:16:45 > 0:16:48And I just... I love them, they're just so, so, so...
0:16:48 > 0:16:50oh, my God, it's cold! ...So cool.
0:16:50 > 0:16:54You know, you're cool and all, but I really don't want you that close to me.
0:16:54 > 0:16:58I think I could stay out here longer now my feet have gone numb - Ahhhh!
0:16:58 > 0:17:02Dawn reveals the true scale of the spectacle.
0:17:03 > 0:17:07It's an event that has been happening for the last 250 million years.
0:17:09 > 0:17:12The horseshoe crab is truly prehistoric.
0:17:15 > 0:17:18They are more closely related to spiders than crabs.
0:17:18 > 0:17:21They chew with their legs and their digestive tract
0:17:21 > 0:17:23passes through their brain.
0:17:23 > 0:17:27Sometimes known as King crabs, they, appropriately, have blue blood.
0:17:31 > 0:17:33Their timing is precise.
0:17:33 > 0:17:38They always appear in early May, on the highest tides of the month.
0:17:39 > 0:17:42They use an internal body clock.
0:17:42 > 0:17:44This is set by watching the cycles of the moon.
0:17:49 > 0:17:52Their eyes are a thousand times more sensitive than ours.
0:17:52 > 0:17:56They have ten in all and a couple on their tail for good measure.
0:17:59 > 0:18:03Good time-keeping ensures that a half a million crabs synchronise
0:18:03 > 0:18:06their egg-laying with the high spring tides.
0:18:06 > 0:18:11The smaller males cluster around the larger females, fertilising the eggs
0:18:11 > 0:18:13that she buries deep in the sand.
0:18:17 > 0:18:20Laid high up the beach, the eggs are out of the reach of fish
0:18:20 > 0:18:22predators for most of the month.
0:18:26 > 0:18:30But these prehistoric creatures hadn't reckoned on the birds.
0:18:35 > 0:18:39Horseshoe crabs once walked alongside dinosaurs, long
0:18:39 > 0:18:41before birds appeared on Earth.
0:18:42 > 0:18:46Evolution never prepared them for this.
0:18:48 > 0:18:51The birds snatch any eggs they can.
0:18:52 > 0:18:56Fortunately, as each crab lays 100,000 eggs,
0:18:56 > 0:18:58there are plenty to spare.
0:18:58 > 0:19:02The crabs prefer to sneak ashore under the cover of darkness, but
0:19:02 > 0:19:06if the weather is bad, they have to take their chance in the day.
0:19:06 > 0:19:09One million shore birds use the eggs as fuel to
0:19:09 > 0:19:14power their journey onwards to their Arctic breeding ground. Some travel
0:19:14 > 0:19:16ten thousand miles to get here.
0:19:19 > 0:19:23Sand-pipers rely on the surf to reveal the nutritious crab caviar.
0:19:31 > 0:19:34Although the horseshoe crabs' emergence is remarkable,
0:19:34 > 0:19:38the birds' appearance here is even more extraordinary.
0:19:38 > 0:19:41Their journeys are governed by a knowledge held by all the birds
0:19:41 > 0:19:45- a swarm intelligence based on the collective experience of all.
0:19:59 > 0:20:03It is this kind of shared intelligence that drives
0:20:03 > 0:20:07one of the most famous migrations on the planet.
0:20:12 > 0:20:14Wildebeest may seem familiar,
0:20:14 > 0:20:16but look at them from a different perspective
0:20:16 > 0:20:19and it's clear that they act as a swarm.
0:20:24 > 0:20:26As they cross the plains of East Africa,
0:20:26 > 0:20:29following the seasonal rains, they do everything together.
0:20:32 > 0:20:34Like starlings, they are hyper-sensitive
0:20:34 > 0:20:40to their immediate neighbours and their interactions connect the herd together like a web.
0:20:40 > 0:20:45From the air, it's possible to gain a sense of how far the network spreads.
0:20:49 > 0:20:53Dotted among the wildebeest are smaller groups of zebra.
0:20:54 > 0:20:58They exist as small family groups, even within bigger herds.
0:20:58 > 0:21:03Each member reacts intelligently to events. As they join the wildebeest
0:21:03 > 0:21:07migration, it's possible to see their different strategies in action.
0:21:09 > 0:21:13In common with other swarms, migrating wildebeest are gripped by a collective urge -
0:21:13 > 0:21:15nothing stands in their way.
0:21:17 > 0:21:20Driven by the will of the herd, they make decisions
0:21:20 > 0:21:22that, on the face of it, seem quite stupid.
0:21:26 > 0:21:27The river stops them in their tracks
0:21:27 > 0:21:30- it's as if the whole herd has to decide together
0:21:30 > 0:21:32when it's safe to take the plunge.
0:21:35 > 0:21:40Gradually, pressure builds from the ones behind until the front-runners
0:21:40 > 0:21:41are left with no option.
0:21:41 > 0:21:43Someone has to go first -
0:21:43 > 0:21:46but it's the herd that makes the decision.
0:22:17 > 0:22:20This is the moment the crocodiles have been waiting for -
0:22:20 > 0:22:25with thousands of floundering prey, they should have a field day.
0:22:29 > 0:22:33But the crocs soon discover it's not that easy.
0:22:33 > 0:22:36Among the mass of bodies and flailing hooves,
0:22:36 > 0:22:38the crocs can't single out a target.
0:22:40 > 0:22:44Faced by overwhelming numbers, they beat a retreat.
0:22:44 > 0:22:47Jumping in feet first has actually worked for the swarm.
0:22:50 > 0:22:51The zebras arrive.
0:22:51 > 0:22:54Unlike the wildebeest, they prefer to make a plan.
0:23:03 > 0:23:07They carefully consider all options before they join the throng.
0:23:11 > 0:23:14They deliberately avoid the apparently mindless masses.
0:23:29 > 0:23:33Meanwhile, the wildebeest have led themselves up a blind alley.
0:23:33 > 0:23:36They are pinned against a wall that is impossible to climb.
0:23:41 > 0:23:43The zebra appear to have chosen more wisely,
0:23:43 > 0:23:46but independence has its own dangers.
0:23:46 > 0:23:51Their well-considered plan didn't account for the crocodiles.
0:24:05 > 0:24:08On their own, the zebra are an easy target.
0:24:17 > 0:24:20The wildebeest may be floundering, but the mass of bodies pushing
0:24:20 > 0:24:24from behind has helped some to start scaling the wall -
0:24:24 > 0:24:25probing it for escape routes.
0:24:42 > 0:24:45The remaining zebra make it to the other side,
0:24:45 > 0:24:47but their problems continue.
0:24:48 > 0:24:50The bank is too high to get out.
0:24:59 > 0:25:04The wildebeest spread along the bank, testing each section for a possible way out.
0:25:04 > 0:25:07Their vast numbers increase the chance of one of them
0:25:07 > 0:25:08finding an escape route.
0:25:20 > 0:25:23Eventually, some of them are successful.
0:25:23 > 0:25:25The masses follow their lead.
0:25:28 > 0:25:31Swarm intelligence finally pays off.
0:25:36 > 0:25:40The zebra are still paying the price for their independence of mind.
0:25:56 > 0:26:00The whole wildebeest herd funnels up the escape route.
0:26:00 > 0:26:05As they break down the bank, they make it easier for those that follow.
0:26:06 > 0:26:08This fact hasn't been lost on the zebra -
0:26:08 > 0:26:10they now have to join the wildebeest.
0:26:13 > 0:26:16Despite their apparently mindless approach,
0:26:16 > 0:26:18all the wildebeest survived.
0:26:18 > 0:26:21The zebra weren't so lucky.
0:26:21 > 0:26:25Here it's not brain versus brawn -
0:26:25 > 0:26:30it is individual brains versus the intelligence of the swarm.
0:26:33 > 0:26:36Although each zebra has a higher intellect, by working together,
0:26:36 > 0:26:39the wildebeest herd gains greater wisdom.
0:26:39 > 0:26:42It's surely no coincidence that wildebeest outnumber zebra
0:26:42 > 0:26:44by nearly ten to one.
0:26:50 > 0:26:54This swarm is joined by another - red-billed quelea -
0:26:54 > 0:26:57the most numerous bird on the planet.
0:26:57 > 0:27:01When they flock together, they also act with one mind.
0:27:01 > 0:27:06Although they feed in small flocks, they join up to become a mega-flock
0:27:06 > 0:27:09as they make their way to roost sites or waterholes.
0:27:22 > 0:27:25The flocks are mixed ages. Most are this year's young -
0:27:25 > 0:27:27fledgling birds, just a few weeks old.
0:27:27 > 0:27:30LOUD CHIRPING
0:27:44 > 0:27:49They are still very inexperienced - their naivety makes them vulnerable.
0:27:52 > 0:27:56Their biggest enemy is the lanner falcon.
0:27:56 > 0:27:59It soon learns where their watering holes are.
0:28:02 > 0:28:06The lanner reaches 150 miles per hour in a stoop.
0:28:13 > 0:28:17Taken by surprise, the youngster didn't stand a chance.
0:28:23 > 0:28:25The survivors may have had their feathers ruffled,
0:28:25 > 0:28:28but they've learned an important lesson.
0:28:32 > 0:28:34They are in a quandary.
0:28:34 > 0:28:36It's dangerous to drink,
0:28:36 > 0:28:38but they won't survive the night without water.
0:28:40 > 0:28:45This is where their collective intelligence starts to work.
0:28:45 > 0:28:49The flock start to share roles.
0:28:49 > 0:28:52The more adventurous resume drinking, but this time,
0:28:52 > 0:28:55the more nervous birds act as lookouts.
0:28:55 > 0:28:59They watch the braver ones' backs as they drink.
0:29:04 > 0:29:06The falcon tries again.
0:29:10 > 0:29:12FRANTIC CHIRPING
0:29:12 > 0:29:15Quickly spotted, a wave of panic alerts the flock.
0:29:27 > 0:29:32Such group tactics work well because every bird has a slightly different personality.
0:29:32 > 0:29:34Some are wary and hold back,
0:29:34 > 0:29:38others throw caution to the wind, risking all for a drink.
0:29:38 > 0:29:43Once the daredevils have finished, they take over lookout duties.
0:29:47 > 0:29:51By rotating roles, the flock increases its overall awareness.
0:29:51 > 0:29:55Together, they outsmart the lanner falcon.
0:30:35 > 0:30:39Safely refreshed, the flock returns to its roost.
0:30:46 > 0:30:49But this is not simply a dormitory,
0:30:49 > 0:30:54it's a meeting room where almost a million birds exchange information.
0:30:57 > 0:31:02In a way not yet understood, the quelea learn from each other.
0:31:13 > 0:31:14News travels fast.
0:31:14 > 0:31:16Prime feeding spots that yesterday
0:31:16 > 0:31:20were only known by a select few, become today's star attractions.
0:31:22 > 0:31:26They leave the roost with a clear mission on their collective mind.
0:31:26 > 0:31:30A deluge of birds now descends on the ripe grass seeds.
0:31:37 > 0:31:40The leading edge of the flock lands and begins to feed.
0:31:40 > 0:31:44Birds at the back leapfrog to the front of the queue.
0:31:44 > 0:31:46This creates a wave of continuous motion -
0:31:46 > 0:31:50a rolling flock that devours every seed in its path.
0:32:09 > 0:32:13Both wildebeest and quelea show the wisdom of the crowd in action.
0:32:13 > 0:32:19But swarm intelligence actually reaches perfection in insects.
0:32:24 > 0:32:30Even the most basic insects can show surprising social organisation.
0:32:30 > 0:32:37Every month, Lake Victoria in East Africa spawns the largest eruption of flies on earth.
0:32:38 > 0:32:42They emerge from the lake at night after the rains,
0:32:42 > 0:32:44triggered by the onset of the new moon.
0:32:44 > 0:32:46BUZZING
0:32:50 > 0:32:56During an emergence, lakeside islands become blanketed with flies.
0:32:58 > 0:33:02Their sole purpose is to reproduce.
0:33:02 > 0:33:06It's how they go about it that makes them so extraordinary.
0:33:08 > 0:33:14The male use their large feathery antennae like the antlers of rutting deer, to fight with rivals.
0:33:22 > 0:33:25Like deer, those with the most impressive headgear have the
0:33:25 > 0:33:28greatest chance of attracting a mate.
0:33:36 > 0:33:42Once airborne, the power of the swarm really takes off.
0:33:43 > 0:33:47They are about to undertake the world's largest mating ritual.
0:33:48 > 0:33:51At first, the clouds of males look totally random,
0:33:51 > 0:33:55but gradually, order emerges from the chaos.
0:33:55 > 0:33:58The flies decide on a landmark on the ground
0:33:58 > 0:34:00and organise themselves above it.
0:34:03 > 0:34:07They create columns that dance like will-o-the-wisps,
0:34:07 > 0:34:10never shifting from their chosen position.
0:34:11 > 0:34:16The dance of the males is designed to entice the females. The columns
0:34:16 > 0:34:20lure them in from a great distance. Once inside, they mate.
0:34:36 > 0:34:39When the dancing is at its height, it looks almost as
0:34:39 > 0:34:42though the forest is on fire.
0:34:51 > 0:34:54Out on the lake, this mating ritual happens on a spectacular scale.
0:34:54 > 0:34:57Trillions of flies are involved
0:34:57 > 0:35:00and the column may rise 200m into the air.
0:35:02 > 0:35:06Their desire to perform over a fixed point draws them to land.
0:35:12 > 0:35:16Billions of flies create this ephemeral structure.
0:35:16 > 0:35:20It behaves like a single entity, even flying against the wind -
0:35:20 > 0:35:23a seemingly impossible feat, given the flies' tiny size.
0:35:34 > 0:35:36If lake flies can become so organised,
0:35:36 > 0:35:39it is hardly surprising that some insects have taken
0:35:39 > 0:35:43social decision-making to spectacular heights.
0:35:43 > 0:35:46But we are only just discovering how clever they really are.
0:35:46 > 0:35:51A fact some of us may have suspected all along.
0:35:52 > 0:35:54Ew...This is gross.
0:35:54 > 0:35:57OK, go and move the pillow.
0:35:57 > 0:36:01Ah, this is disgusting! Mum, look at...
0:36:01 > 0:36:03how many do you think there are?
0:36:03 > 0:36:05About a thousand.
0:36:05 > 0:36:07What do you think these guys are thinking?
0:36:07 > 0:36:11We have reason to be in awe of ants.
0:36:17 > 0:36:19Slowed down forty times,
0:36:19 > 0:36:23these African driver ants are moving house.
0:36:24 > 0:36:28The 20 million individuals that make up the colony
0:36:28 > 0:36:31have collectively made the decision to move.
0:36:31 > 0:36:36They carry their eggs, larvae and pupae with them,
0:36:36 > 0:36:39dividing up their tasks according to size.
0:36:43 > 0:36:46The workers carry the larvae, while the soldiers hold
0:36:46 > 0:36:50the much larger pupae that will ultimately become new soldiers.
0:37:03 > 0:37:06It's a huge undertaking, but many claws make light work,
0:37:06 > 0:37:11and the entire colony of 20 million individuals relocates
0:37:11 > 0:37:13over the course of 48 hours.
0:37:24 > 0:37:27The heavily fortified trail can stretch a hundred metres from the
0:37:27 > 0:37:31old nest - the equivalent of 11 miles in the human world.
0:37:48 > 0:37:51As we all know, moving house is never easy
0:37:51 > 0:37:54and the ants' journey is fraught with problems.
0:38:01 > 0:38:06A twig blocking their path is like a tree blocking a main road.
0:38:06 > 0:38:09Their first job is to identify the problem.
0:38:11 > 0:38:16Those first at the scene call for back-up, releasing a pheromone.
0:38:16 > 0:38:19The heavy mob arrive and immediately set to work -
0:38:19 > 0:38:22they can lift 50 times their own weight.
0:38:28 > 0:38:32As well as brute strength, this needs supreme organisation.
0:38:32 > 0:38:36They somehow have to all lift and push at the same time -
0:38:36 > 0:38:40a challenge that even we find difficult.
0:38:44 > 0:38:48Obstruction removed, the traffic soon starts flowing again.
0:38:51 > 0:38:54In defence of the trail, the ants take no prisoners,
0:38:54 > 0:38:59but even an innocuous-looking insect can be surprisingly dangerous.
0:39:02 > 0:39:06The soil millipede is killed quickly, but the soldier's highly-
0:39:06 > 0:39:11sensitive antennae immediately reveal that it's poisonous.
0:39:11 > 0:39:16The message soon reaches nearby ants. They know exactly what to do.
0:39:16 > 0:39:20They gather lumps of mud and bury the problem.
0:39:53 > 0:39:56With the millipede out of harm's way, the trail can safely
0:39:56 > 0:39:58continue its journey.
0:40:05 > 0:40:07But more dangers await the trailblazers.
0:40:13 > 0:40:17A praying mantis plucks unsuspecting ants from the column.
0:40:23 > 0:40:25He seems to have the upper hand,
0:40:25 > 0:40:29but the ants he kills send out a dying message.
0:40:29 > 0:40:34Reacting to this pheromone, reinforcements arrive.
0:40:34 > 0:40:37The mantis is a deadly predator,
0:40:37 > 0:40:40but the ants know exactly what they're dealing with.
0:40:45 > 0:40:47One soldier grabs the mantis' jaws,
0:40:47 > 0:40:50stopping it from doing any more damage.
0:40:55 > 0:40:57Other ants swarm over the mantis,
0:40:57 > 0:41:00butchering it with surgical precision.
0:41:14 > 0:41:18The mantis' fate is sealed by a clinical decapitation.
0:41:28 > 0:41:31The eggs and pupae are taken into the new nest.
0:41:35 > 0:41:37Here, they are safe.
0:41:37 > 0:41:40The millions of interlocking ants that make up the nest's
0:41:40 > 0:41:43superstructure create an impenetrable barrier.
0:42:02 > 0:42:05Only from the outside is it possible to get an idea
0:42:05 > 0:42:07of the nest's huge scale.
0:42:13 > 0:42:16Literally millions of individuals
0:42:16 > 0:42:21form a nervous network that communicates using pheromones.
0:42:24 > 0:42:28As ants pass messages to each other, they effectively act like brain cells.
0:42:34 > 0:42:37Through the millions of inter-connections
0:42:37 > 0:42:41they arrive at a decision that works for the benefit of the colony.
0:42:50 > 0:42:54Like human brain cells, individual ants are not "intelligent",
0:42:54 > 0:42:58but the links between them create a mind - an ant superbrain.
0:43:25 > 0:43:28Deep inside is the queen.
0:43:28 > 0:43:33Her role is to replenish the colony by laying 2 million eggs a month.
0:43:38 > 0:43:42She is merely an egg-laying machine, under the collective command of all
0:43:42 > 0:43:45the ants that make up the mind of the hive.
0:44:00 > 0:44:03The ants create a different kind of intelligence -
0:44:03 > 0:44:07a brain that exists outside any single body.
0:44:14 > 0:44:17Other social insects work in a similar way.
0:44:17 > 0:44:20One of the most well-studied is the honey bee.
0:44:24 > 0:44:27Like ants, individual bees communicate with others in
0:44:27 > 0:44:30the hive and their experiences add together to make decisions
0:44:30 > 0:44:32for the benefit of the colony.
0:44:33 > 0:44:39This is most apparent when bees create swarms, as they do when looking for a new home.
0:44:46 > 0:44:50In their searches, they can turn up just about anywhere
0:44:50 > 0:44:54- a disconcerting fact for anyone caught in their path.
0:44:55 > 0:44:58They're all right here, man.
0:44:58 > 0:45:01Every single one of them.
0:45:01 > 0:45:06We'll end up with a whole hive on the thing. Oh yeah.
0:45:20 > 0:45:25What seems to us an odd choice is just part of an efficient process
0:45:25 > 0:45:30that ultimately results in the swarm finding the right place to settle permanently.
0:45:30 > 0:45:34So, choosing a car or a bike isn't necessarily a mistake.
0:45:36 > 0:45:40It has plenty of nooks and crannies where they can build their combs.
0:45:48 > 0:45:52The first bees to land release a pheromone that guides the others in.
0:45:52 > 0:45:55They cluster together in a protective mass.
0:45:57 > 0:46:02But as the sun beats down and temperatures soar, they begin
0:46:02 > 0:46:04to question their choice.
0:46:06 > 0:46:08There is only so much shade to go around.
0:46:08 > 0:46:10They fan their wings to keep cool.
0:46:10 > 0:46:13But the over-heating bees release a chemical signal
0:46:13 > 0:46:16that tells the scout bees that they aren't happy.
0:46:18 > 0:46:23The scouts quickly get the message, and set off to find an alternative.
0:46:24 > 0:46:28With the sun beating down, it's a race against time.
0:46:28 > 0:46:32The scouts look for a cavity large enough to contain the hive.
0:46:32 > 0:46:35This shows distinct possibilities.
0:46:41 > 0:46:42She inspects the property -
0:46:42 > 0:46:46pacing the floor and measuring up, just like a human surveyor.
0:46:58 > 0:47:01Once the scout is happy, she leaves to let the swarm know.
0:47:08 > 0:47:13Back at the temporary bivouac, she announces the good news by dancing.
0:47:13 > 0:47:16But this is a dance with a precise meaning.
0:47:16 > 0:47:18The straight part of the dance shows the angle
0:47:18 > 0:47:20they must fly to find the cavity.
0:47:26 > 0:47:29The duration of her waggle dance shows how far they have to go.
0:47:29 > 0:47:33A second's worth of waggles equals half a mile of flying.
0:47:44 > 0:47:47Other scouts watch the dance,
0:47:47 > 0:47:51following her every move, taking in her directions.
0:47:51 > 0:47:54When she leaves, the scouts follow.
0:47:56 > 0:48:00With her guidance, this advance party makes a beeline to the exact spot.
0:48:07 > 0:48:09Now it's their turn to check it out.
0:48:11 > 0:48:16They too pace out the cavity, checking whether they agree or not.
0:48:23 > 0:48:25Having all made their assessment,
0:48:25 > 0:48:28they hold a committee meeting to consider their findings.
0:48:31 > 0:48:33How they arrive at a consensus is uncertain,
0:48:33 > 0:48:35but eventually they do.
0:48:40 > 0:48:43They let the swarm know the good news.
0:48:53 > 0:48:56The scouts rush through the swarm, vibrating their wings
0:48:56 > 0:48:58in what is called a buzz run.
0:49:04 > 0:49:06This tells the swarm one thing...
0:49:08 > 0:49:10It's time to leave.
0:49:11 > 0:49:17100,000 bees take to the air in less than two minutes.
0:49:21 > 0:49:24The swarm follows the scouts, leading them to their new home.
0:49:34 > 0:49:36As more and more bees settle in,
0:49:36 > 0:49:39they release a scent that attracts in any stragglers.
0:49:42 > 0:49:45Communal thinking is the secret to the swarm's success.
0:49:45 > 0:49:48But this kind of intelligence has its problems.
0:49:48 > 0:49:52It works best when things stay as nature intended.
0:49:52 > 0:49:54But it can't think out of the box.
0:50:02 > 0:50:04Even this might not be the disaster it seems.
0:50:04 > 0:50:07Many swarms have become successful by being transported
0:50:07 > 0:50:09as stowaways around the world.
0:50:15 > 0:50:18..Traffic heavy, one mile south of the airport...
0:50:21 > 0:50:26These are Fireants. They originated in the jungles of Brazil and arrived
0:50:26 > 0:50:29in North America on cargo vessels.
0:50:29 > 0:50:34They now infest many airports, homes and public buildings across the southern states of America.
0:50:35 > 0:50:40Despite their tiny size, they have the power to close down
0:50:40 > 0:50:43airports, traffic control systems and server networks.
0:50:43 > 0:50:46Their destructive influence continues to grow.
0:50:51 > 0:50:54Computers are especially vulnerable.
0:50:54 > 0:50:57Remarkably, it's the electricity that they like.
0:51:00 > 0:51:04Their antennae are electro-sensitive and the ants react
0:51:04 > 0:51:08to electrical charges by attacking them with their jaws.
0:51:08 > 0:51:11The soldier ants also like the sweet taste of the terminals
0:51:11 > 0:51:14and they can't resist having a nibble.
0:51:19 > 0:51:22All this activity creates problems and leads to dangerous
0:51:22 > 0:51:26short circuits as their jaws and legs touch exposed circuitry.
0:51:31 > 0:51:33They are now creating havoc
0:51:33 > 0:51:36over vast areas of the southern states of America.
0:51:46 > 0:51:51Having come from the rainforest, the ants are used to this kind of weather.
0:51:56 > 0:52:01But unknowingly, the ants have built their nest in a drainage ditch.
0:52:02 > 0:52:06Flooding is a challenge for even the most intelligent swarm.
0:52:12 > 0:52:16The ants start an evacuation, moving the nest to higher ground.
0:52:21 > 0:52:23It's women and children first,
0:52:23 > 0:52:27as the ants carry the queen and her pupae to safety.
0:52:29 > 0:52:31But still the water rises.
0:52:46 > 0:52:51The ants react by linking arms together, forming a mesh of inter-connected bodies.
0:52:51 > 0:52:54Between them, they are making a life-raft.
0:52:59 > 0:53:00The ants' most precious cargo,
0:53:00 > 0:53:04the eggs and remaining pupae, are safely stowed on top.
0:53:04 > 0:53:07Flying ants also board - like helicopters on
0:53:07 > 0:53:10an aircraft carrier, ready to lift off to start a new colony
0:53:10 > 0:53:12if the raft gets into trouble.
0:53:15 > 0:53:18Remarkably, some of the pupae are set aside to
0:53:18 > 0:53:22act as flotation devices, to help keep the raft afloat.
0:53:32 > 0:53:37The ants that make up the submerged part of the raft have their own
0:53:37 > 0:53:40emergency air-supply from the air trapped on their bodies.
0:53:43 > 0:53:46As the water level rises further, the raft detaches
0:53:46 > 0:53:51from its moorings - it is now at the mercy of the wind and water.
0:53:59 > 0:54:02Some of the workers paddle with their front legs,
0:54:02 > 0:54:04giving the elements a helping hand.
0:54:07 > 0:54:11On the top deck, the workers tend the pupae and larvae.
0:54:11 > 0:54:15Below deck, workers clean and maintain the underside of the raft.
0:54:22 > 0:54:26As the raft approaches land, it begins to change shape.
0:54:29 > 0:54:32The ants start building a pontoon from the raft that
0:54:32 > 0:54:34reaches towards the bank.
0:54:37 > 0:54:40The individuals are working as a unified team
0:54:40 > 0:54:42for the benefit of the whole colony.
0:54:46 > 0:54:48As fingers of ants reach out,
0:54:48 > 0:54:51they show swarm intelligence working to perfection.
0:55:02 > 0:55:04As more ants add to the pontoon's length,
0:55:04 > 0:55:07it becomes a bridge to the land.
0:55:21 > 0:55:25Once contact is made, the most precious cargo is unloaded first.
0:55:26 > 0:55:30Like a team of porters, they ferry the pupae to the shore.
0:55:30 > 0:55:33The next generation is safe.
0:55:38 > 0:55:45The queen is next to disembark - the colony's future is assured.
0:55:51 > 0:55:56Using their incredible swarm intelligence, fireants are taking on the world.
0:55:59 > 0:56:03As well as invading America, they have started to colonize Australia.
0:56:03 > 0:56:06With global warming, they are likely to invade Europe,
0:56:06 > 0:56:09as far north as southern England.
0:56:11 > 0:56:14They are the swarm of the future.
0:56:17 > 0:56:19As we have explored the world of the swarm,
0:56:19 > 0:56:23we discovered how they profit on the back of our success.
0:56:23 > 0:56:26How they feed off our agriculture
0:56:26 > 0:56:30and take advantage of the new environments we create.
0:56:32 > 0:56:36We have seen how they can erupt at any time - taking us by surprise.
0:56:37 > 0:56:40And how they have hitched a ride with us around the world.
0:56:40 > 0:56:44We have seen how even simple organisms can create spectacles
0:56:44 > 0:56:48that can be awe-inspiring and beautiful.
0:56:48 > 0:56:53And also how they can become the stuff of nightmares.
0:56:53 > 0:56:56We have seen how swarms can learn from their collective experience.
0:56:56 > 0:56:59And how they can act as a single organism.
0:56:59 > 0:57:03We have even seen how looking at swarms is like looking
0:57:03 > 0:57:07into the inner workings of an alien brain.
0:57:07 > 0:57:10But this is one swarm that we have yet to feature -
0:57:10 > 0:57:14one that may even help to save the world.
0:57:16 > 0:57:20These little known creatures are salps - a sea creature that
0:57:20 > 0:57:25in fact is more closely related to us than the jellyfish it resembles.
0:57:26 > 0:57:29They come in many bizarre shape and sizes.
0:57:29 > 0:57:34Many are joined together to create daisy chains - some a mile long.
0:57:41 > 0:57:44At night, all across the oceans of the world,
0:57:44 > 0:57:48they rise to the surface in their billions to feed.
0:57:49 > 0:57:52Recently, their numbers have started to increase
0:57:52 > 0:57:56and swarms now cover thousands of square miles.
0:57:57 > 0:58:02They eat the algae that absorb our greenhouse gasses and then
0:58:02 > 0:58:06safely lock the carbon away at the bottom of the ocean.
0:58:08 > 0:58:13An average swarm removes an incredible 4,000 tons of carbon each night.
0:58:15 > 0:58:20They are a growing swarm with the power to help save our planet and
0:58:20 > 0:58:23their significance has only just been discovered.
0:58:23 > 0:58:29They are living proof that we should never underestimate the power of the swarm.
0:58:49 > 0:58:53Subtitles by Red Bee Media Ltd
0:58:53 > 0:58:57E-mail subtitling@bbc.co.uk