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Animals can sometimes reach such
numbers they defy our understanding.
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00:00:09,320 --> 00:00:13,880
They seem to rise up
and invade our lives.
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00:00:16,800 --> 00:00:18,960
They become super swarms,
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00:00:18,960 --> 00:00:22,520
So immense
they're impossible to ignore.
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00:00:25,280 --> 00:00:29,160
From the outside,
they can be the stuff of nightmares.
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00:00:29,160 --> 00:00:32,200
From the inside,
they're a thing of beauty.
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00:00:33,280 --> 00:00:35,840
As we enter the heart of the swarm,
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00:00:35,840 --> 00:00:39,960
we'll discover what happens
when they meet our world.
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00:00:50,480 --> 00:00:55,440
It's 1995 at a football match
between Costa Rica and Italy.
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00:00:55,440 --> 00:00:59,880
Killer bees stage a pitch
invasion of a different kind.
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The players' panic
is understandable.
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These bees have been known to Kill.
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00:01:06,120 --> 00:01:10,320
To understand what the swarm was
thinking, we recreated the encounter
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00:01:10,320 --> 00:01:13,640
and slowed it down to match
the bees' reaction times.
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00:01:25,320 --> 00:01:29,840
In Costa Rica, pitch invasions by
killer bees are surprisingly common.
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Swarms like to make a beeline
across open areas,
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which can bring them
right into the field of play.
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00:01:52,640 --> 00:01:54,840
By showing the action
in slow motion,
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00:01:54,840 --> 00:01:56,920
it becomes clear
that the footballers
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are making the situation worse.
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00:01:59,760 --> 00:02:03,400
Swiping at the bees is
a complete waste of time.
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00:02:03,400 --> 00:02:07,840
Their reactions are so fast, they
can easily swerve out of the way.
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It's also a very bad idea.
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Movement not only makes them
angrier,
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00:02:14,040 --> 00:02:15,880
it gives them a target
to aim for.
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00:02:24,440 --> 00:02:26,560
The bees' lives depend on teamwork.
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00:02:26,560 --> 00:02:30,160
Retaliation is swift
and devastating.
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00:02:37,440 --> 00:02:40,200
Although each bee can sting
only once,
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00:02:40,200 --> 00:02:43,400
the sting left behind pumps out
a pheromone,
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00:02:43,400 --> 00:02:46,800
that whips nearby bees
into a fighting frenzy.
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They join the attack and each new
sting brings in more angry bees.
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00:03:04,640 --> 00:03:08,600
Unlike honey bees, killer
bees rarely give up a fight.
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00:03:08,600 --> 00:03:11,760
But this swarm has other
things on its mind.
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00:03:11,760 --> 00:03:13,240
It's house-hunting.
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00:03:16,160 --> 00:03:19,600
Swarms arise
when a hive gets too big.
36
00:03:19,600 --> 00:03:22,480
They view the camera
as a possible new home.
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00:03:23,000 --> 00:03:26,080
Bees are sensitive
to electrical fields.
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00:03:26,080 --> 00:03:29,080
That seems to make
the camera even more desirable.
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00:03:44,000 --> 00:03:47,040
A killer bee sting is no worse
than that of a honey bee,
40
00:03:47,040 --> 00:03:49,640
but hundreds will sting
at any one time
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00:03:49,640 --> 00:03:53,000
and it's this behaviour
that makes them dangerous.
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00:04:04,400 --> 00:04:07,920
Lying down is
a surprisingly good idea.
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00:04:07,920 --> 00:04:09,960
The players merge with the ground
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00:04:09,960 --> 00:04:13,400
and the bees simply fly over them,
unable to find a target.
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00:04:17,000 --> 00:04:20,520
SIRENS WAIL
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00:04:21,280 --> 00:04:24,600
Killer bees were accidentally
created in Brazil in 1957
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by crossing honey bees
with aggressive African bees.
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00:04:28,160 --> 00:04:30,800
Since then, they've spread
northwards
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00:04:30,800 --> 00:04:33,560
as far as
the southern states of America.
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00:04:36,280 --> 00:04:40,680
But there is a swarm that has
created far more devastation
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00:04:40,680 --> 00:04:42,040
than any killer bees.
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00:04:46,240 --> 00:04:49,640
Morocco, December 2004.
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00:04:49,640 --> 00:04:55,000
One of the oldest swarms
on the planet is on the move.
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00:04:55,000 --> 00:04:58,760
One of the ten plagues of Egypt,
they still invade one fifth
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00:04:58,760 --> 00:05:00,520
of the world's land surface
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and affect one tenth of the human
population.
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00:05:04,880 --> 00:05:07,800
Even today,
meeting a swarm is unnerving
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as this home video footage shows.
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00:05:10,120 --> 00:05:12,080
Eurgh!
60
00:05:13,080 --> 00:05:15,560
Mommy! This is crazy.
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00:05:17,960 --> 00:05:21,880
Oh, my God, there are going to be millions
of these and they're all flying off.
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00:05:21,960 --> 00:05:24,760
There's so many of them
just swarming over here.
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00:05:25,160 --> 00:05:25,880
They're still just coming, across
the road on both sides of the car.
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00:05:26,240 --> 00:05:27,200
Oh, my God! ..Complete
infestation...
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00:05:27,360 --> 00:05:29,200
Argh! Mommy! Mommy!
66
00:05:30,080 --> 00:05:32,800
Swarm locusts start life
as hoppers,
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00:05:32,800 --> 00:05:35,400
the offspring of a solitary locust,
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00:05:35,400 --> 00:05:38,120
forced together by a shortage of
food.
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00:05:43,280 --> 00:05:47,240
The hoppers crowd together
to create an insect army.
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00:05:50,320 --> 00:05:55,080
It's an army that marches on its
stomach, eating everything in its path.
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00:06:03,840 --> 00:06:06,280
When they run out of food,
they march some more,
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00:06:06,280 --> 00:06:08,840
crossing open ground
in vast battalions,
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00:06:08,840 --> 00:06:12,440
travelling up to 1.5 miles each day.
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00:06:13,840 --> 00:06:18,000
They stay as a ground
army for four weeks,
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00:06:18,000 --> 00:06:20,520
before changing into an air force.
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00:06:29,120 --> 00:06:31,800
As they fly,
they synchronise their wing beats.
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00:06:31,800 --> 00:06:35,040
This reduces turbulence,
making their flying more efficient.
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00:06:45,920 --> 00:06:49,560
Like fighter pilots,
they fly in perfect formation.
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00:06:49,560 --> 00:06:51,880
But here, one billion locusts
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00:06:51,880 --> 00:06:54,960
are covering an area the size of
Heathrow.
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00:06:57,600 --> 00:07:00,400
It would be an air traffic
controller's nightmare,
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00:07:00,400 --> 00:07:02,360
but the locusts maintain formation
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00:07:02,360 --> 00:07:04,560
by keeping a set distance
from each other.
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00:07:04,560 --> 00:07:08,120
They even have anti-crash detectors,
to avoid mid-air collisions.
85
00:07:09,160 --> 00:07:11,760
They react six times faster
than a human pilot,
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00:07:11,760 --> 00:07:13,640
so even in such crowded air space,
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00:07:13,640 --> 00:07:16,640
split-second manoeuvres
can get them out of trouble.
88
00:07:29,280 --> 00:07:33,440
Such state of the art flight systems
make locusts a force to be reckoned with.
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00:07:51,280 --> 00:07:53,040
When they reach the human world,
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they're almost impossible
to control.
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00:08:00,120 --> 00:08:02,520
They eat their own weight in food
in a day.
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00:08:02,520 --> 00:08:10,080
A large swarm can get through 200,000
tonnes, enough to feed half a billion people.
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00:08:17,640 --> 00:08:21,720
Locusts aren't the only ancient
swarm that still plagues us today.
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00:08:32,040 --> 00:08:36,200
The house mouse originated in Asia
and spread with human agriculture.
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00:08:36,200 --> 00:08:40,480
When conditions are right,
they can quickly become plagues.
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00:08:46,320 --> 00:08:47,640
In South Australia,
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00:08:47,640 --> 00:08:51,160
mice outbreaks happen
on average once every ten years.
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00:09:03,240 --> 00:09:06,880
They erupt after a period of wet
weather creates bumper harvests.
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00:09:06,880 --> 00:09:10,760
By the time they're discovered,
it's usually too late.
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00:09:18,880 --> 00:09:22,000
It's every farmer's
living nightmare.
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00:09:38,320 --> 00:09:43,960
One unfortunate farmer filmed the actual moment
she realised her pest problem was out of control.
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00:09:54,160 --> 00:09:56,080
Oh! They're in my boots! Eugh!
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00:09:56,080 --> 00:09:58,280
Concerned for
the safety of her pigs,
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00:09:58,280 --> 00:10:00,080
she throws caution to the wind.
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00:10:01,800 --> 00:10:03,280
Yuk! Oh!
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SHE SCREAMS
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00:10:13,840 --> 00:10:19,080
Among the pens, the mice found a limitless
supply of food and safety from predators.
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00:10:19,080 --> 00:10:22,520
It didn't take long for their
numbers to go through the roof.
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00:10:43,760 --> 00:10:47,040
The secret of their success is
a rampant sex life
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that turns breeding into a weapon.
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00:10:49,480 --> 00:10:53,280
A pair of mice
can have babies every three weeks.
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00:10:53,280 --> 00:10:58,200
These, in turn, can breed just five weeks later
and their offspring, five weeks after that.
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00:10:58,200 --> 00:11:02,080
Unchecked,
the numbers just keep growing.
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00:11:08,200 --> 00:11:10,880
In theory, one mouse
and her offspring
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00:11:10,880 --> 00:11:12,960
can produce 3,000 mice a year.
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00:11:12,960 --> 00:11:17,480
With few predators to control them,
theory rapidly comes fact.
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00:11:25,680 --> 00:11:30,040
In one outbreak, 35 million mice
were killed in just one month.
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00:11:30,040 --> 00:11:33,040
Even this hardly dented
their numbers.
119
00:11:39,680 --> 00:11:43,920
Eventually, stress and disease take
their toll and the population crashes.
120
00:11:43,920 --> 00:11:48,800
For every 1,000 mice,
just two will remain.
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00:11:48,800 --> 00:11:50,840
But they're breeding machines,
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ready to surprise us
at any time in the future.
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00:11:56,960 --> 00:12:00,720
Some swarms are more predictable.
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00:12:07,440 --> 00:12:10,640
This eerie invasion
happens like clockwork
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00:12:10,640 --> 00:12:13,320
once a year
in the Midwest of America.
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00:12:13,320 --> 00:12:17,440
It can be so dense,
it slows traffic to a crawl.
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00:12:20,480 --> 00:12:24,800
The swarms can smother an area of
4,500 square miles
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00:12:24,800 --> 00:12:26,960
and even show up on radar.
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00:12:35,280 --> 00:12:36,920
These are mayflies.
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00:12:36,920 --> 00:12:39,520
They have emerged
from the Mississippi River,
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00:12:39,520 --> 00:12:42,040
where they lived as larvae
for the past year.
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00:12:42,040 --> 00:12:45,560
They will exist as adults
for only a day.
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00:12:52,200 --> 00:12:57,480
Their cue is a water temperature
of exactly 17.5 degrees centigrade.
134
00:12:57,480 --> 00:13:01,200
They hardly have a chance to
try out their new body and wings
135
00:13:01,200 --> 00:13:03,040
before it's all change again.
136
00:13:05,240 --> 00:13:07,960
For some unknown reason,
the body splits
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00:13:07,960 --> 00:13:10,640
and an almost
identical mayfly emerges.
138
00:13:10,640 --> 00:13:13,880
The previous form may have
existed for less than an hour.
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00:13:19,520 --> 00:13:24,000
They soon spread their second set of
wings, this time in a mating flight.
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00:13:26,080 --> 00:13:29,520
By emerging together,
there's safety in numbers.
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00:13:29,520 --> 00:13:31,600
Nothing could eat this many.
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00:13:31,600 --> 00:13:35,080
They soon return to the Mississippi
to lay their eggs.
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00:13:39,720 --> 00:13:44,400
Each female lays up to 8,000, making
up for the billions of mayflies
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00:13:44,400 --> 00:13:46,880
that never make it back
to the river.
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00:13:50,160 --> 00:13:55,600
It's easy to get lost. They navigate
using the moon as a reference point.
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00:13:55,600 --> 00:13:56,760
But near towns,
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00:13:56,760 --> 00:14:00,760
this ancient navigational system
is next to useless.
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00:14:02,320 --> 00:14:06,400
Artificial moons are everywhere
and these beckoning lights cause
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00:14:06,400 --> 00:14:08,800
mayflies to become
hopelessly confused.
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00:14:14,960 --> 00:14:17,880
The road also reflects light
like the river,
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00:14:17,880 --> 00:14:20,880
attracting the mayflies
down to lay their eggs.
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00:14:26,080 --> 00:14:32,760
As the mayflies are lured further into town,
they spread their own haze of confusion.
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00:14:33,040 --> 00:14:35,400
The locals have seen it all before.
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00:14:35,400 --> 00:14:38,600
It's mayflies' breeding day...
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in South Ballston Virginia.
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00:14:41,240 --> 00:14:46,280
I don't know if you can see this, but this is
mayflies, and they come out in the gajillions!
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00:14:46,280 --> 00:14:49,360
And these things,
they come out like this
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00:14:49,360 --> 00:14:51,520
on certain days, all at once
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00:14:51,520 --> 00:14:54,600
and they cover the streets
of downtown South Ballston,
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00:14:54,600 --> 00:14:58,600
and probably just about anywhere
where the damn river runs through.
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00:14:58,600 --> 00:15:01,760
It sounds like the wind is blowing out
here, because there's so many of them.
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00:15:01,760 --> 00:15:05,280
It's just amazing,
you just wouldn't believe it.
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There are certainly huge numbers,
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00:15:08,440 --> 00:15:13,120
an estimated 18 trillion emerge
for one night only.
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00:15:13,120 --> 00:15:16,320
3,000 times
the world's human population.
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00:15:16,320 --> 00:15:20,160
Many fly straight to
the bright lights of the city,
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00:15:20,160 --> 00:15:23,680
10,000 may cover a single neon sign.
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00:15:27,320 --> 00:15:31,680
By extraordinary coincidence,
the invasion often coincides
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00:15:31,680 --> 00:15:35,360
with one of America's most
important celebrations -
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00:15:35,360 --> 00:15:36,800
Independence Day.
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00:15:40,120 --> 00:15:44,080
As crowds fill the streets
of La Crosse, Wisconsin,
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00:15:44,080 --> 00:15:48,440
they are outnumbered by mayflies
25 million to one.
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00:15:52,640 --> 00:15:57,400
Stand too close to a light and
you certainly know it's mayfly day.
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00:16:03,120 --> 00:16:05,680
Fortunately, the mayflies
are totally harmless.
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00:16:05,680 --> 00:16:09,680
They have no mouth parts, so they
can't even feed, let alone bite.
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00:16:09,680 --> 00:16:11,680
To us, they seem out of control,
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00:16:11,680 --> 00:16:15,080
but inside the swarm,
it's a different picture.
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00:16:18,080 --> 00:16:20,400
These angelic forms
easily avoid each other,
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00:16:20,400 --> 00:16:23,040
even in the thickest gathering.
180
00:16:39,080 --> 00:16:42,440
As America celebrates
its independence,
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00:16:42,440 --> 00:16:46,040
the mayflies enjoy
the last day of their life.
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00:17:07,240 --> 00:17:12,680
Bird swarms invade our cities too,
a fact which many find unnerving.
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00:17:12,680 --> 00:17:15,360
There's some of them. Oh, my God!
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00:17:15,360 --> 00:17:18,760
It's like The Birds, it's like
the invasion of The Birds over here.
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00:17:18,760 --> 00:17:20,880
Look at this!
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00:17:20,880 --> 00:17:24,120
We're driving through them.
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00:17:24,120 --> 00:17:26,720
I have never in my life
experienced this.
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00:17:27,200 --> 00:17:28,320
Ooh, my gosh!
189
00:17:30,520 --> 00:17:33,960
I'm very shocked at this.
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00:17:46,320 --> 00:17:50,480
In recent years, huge flocks of
roosting birds have become a common
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00:17:50,480 --> 00:17:56,240
sight in many cities, but nowhere do
they reach the numbers seen in Rome.
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00:17:56,240 --> 00:18:00,640
Here, they have become a super
swarm that gets bigger year on year.
193
00:18:03,400 --> 00:18:06,120
Ten million starlings flock together
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00:18:06,120 --> 00:18:10,160
to create the most astonishing
aerial display in nature.
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00:18:46,400 --> 00:18:49,560
These spectacular aerial displays
are seen
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00:18:49,560 --> 00:18:51,680
between October and February,
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00:18:51,680 --> 00:18:55,520
when birds pour into Rome
from all over northern Europe.
198
00:19:08,360 --> 00:19:10,880
To create such perfect synchrony,
199
00:19:10,880 --> 00:19:15,120
it was once thought that the birds
might use telepathic communication.
200
00:19:15,120 --> 00:19:20,040
But in reality, the birds react
13 times faster than any person.
201
00:19:20,040 --> 00:19:23,800
They turn in exact synchrony
with their nearest neighbours,
202
00:19:23,800 --> 00:19:28,880
but the tiniest delay in their reflexes help
create these mesmerising waves in the sky.
203
00:19:42,480 --> 00:19:46,480
Until recently, the spectacle
could only be seen from the ground.
204
00:19:46,480 --> 00:19:51,280
Now it's possible to take cameras
into the swarms and fly among them.
205
00:20:19,240 --> 00:20:24,120
This aerial ballet acts as a beacon
to others still entering the city.
206
00:20:24,120 --> 00:20:28,160
Smaller parties join the bigger
flocks, increasing their numbers.
207
00:20:28,160 --> 00:20:33,120
As they swirl in the sky, they collectively make
decisions on where they should spend the night.
208
00:20:41,400 --> 00:20:45,120
After an hour of pirouetting,
the birds dive downwards,
209
00:20:45,120 --> 00:20:48,280
having decided together
where they will roost.
210
00:20:54,320 --> 00:20:59,440
Birds are drawn to cities because they're
warmer than the surrounding countryside.
211
00:20:59,440 --> 00:21:01,600
Rome, with its balmy
Mediterranean climate,
212
00:21:01,600 --> 00:21:04,480
is an especially popular
destination.
213
00:21:07,560 --> 00:21:12,200
But the city pays a heavy price
for hosting this incredible air show.
214
00:21:17,560 --> 00:21:20,920
Each night, ten million birds
produce
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00:21:20,920 --> 00:21:25,320
seven tons of excrement, playing
havoc with the paintwork of cars.
216
00:21:26,520 --> 00:21:29,400
As the birds settle down
for the night,
217
00:21:29,400 --> 00:21:31,840
there is a constant rain
falling below.
218
00:21:36,120 --> 00:21:39,320
Slippery roads and pavements
cause accidents too,
219
00:21:39,320 --> 00:21:41,480
it's a health and safety nightmare.
220
00:21:43,320 --> 00:21:46,760
But the starlings don't
have it all their own way.
221
00:22:02,840 --> 00:22:06,240
They may look like extras
from a sci-fi B-movie,
222
00:22:06,240 --> 00:22:09,480
but these people really are
wearing their work clothes.
223
00:22:12,480 --> 00:22:18,200
They are starling busters, hired to
clear the streets of this urban menace.
224
00:22:20,520 --> 00:22:23,000
Their weapon of choice
is a loudspeaker.
225
00:22:23,000 --> 00:22:28,600
BIRDS SCREECHING
226
00:22:28,600 --> 00:22:33,560
It plays back a starling's
alarm call, amplified 100 times.
227
00:22:40,280 --> 00:22:43,760
For these birds,
there is simply nothing scarier.
228
00:22:43,760 --> 00:22:50,040
This roost of 100,000 starlings will have to
up sticks and find somewhere else to roost.
229
00:22:50,040 --> 00:22:54,560
This bizarre experiment has been
running for the last 12 years.
230
00:22:54,560 --> 00:22:56,600
It certainly moves the starlings,
231
00:22:56,600 --> 00:22:59,760
but Rome offers plenty of
alternative accommodation
232
00:22:59,760 --> 00:23:02,600
and the number of winter visitors
keeps rising.
233
00:23:05,240 --> 00:23:09,720
Some swarms only invade
our cities once in a generation.
234
00:23:13,320 --> 00:23:17,840
It's July 2008,
and in the suburbs of Cincinnati,
235
00:23:17,840 --> 00:23:21,280
an alien invasion is about to begin.
236
00:23:36,760 --> 00:23:40,480
These periodic cicadas have lived
deep underground
237
00:23:40,480 --> 00:23:46,280
for the last 17 years, but now,
under the cover of darkness,
238
00:23:46,280 --> 00:23:48,520
they start to emerge.
239
00:23:48,520 --> 00:23:52,000
Across vast areas of the state
of Ohio,
240
00:23:52,000 --> 00:23:56,400
ten billion cicadas
join the alien invasion.
241
00:24:03,160 --> 00:24:06,000
They have spent their subterranean
lives sucking the sap
242
00:24:06,000 --> 00:24:08,280
from the roots of trees.
243
00:24:12,720 --> 00:24:15,320
Now, in the 17th year,
when the ground warms
244
00:24:15,320 --> 00:24:19,560
to 18 degrees centigrade,
they all come to the surface.
245
00:24:21,120 --> 00:24:26,320
They make their way towards the nearest
tree and immediately start to climb.
246
00:24:34,760 --> 00:24:38,040
Their marching orders are
genetically programmed
247
00:24:38,040 --> 00:24:39,960
and so is their sense of timing.
248
00:24:44,800 --> 00:24:48,840
But genetics couldn't predict the changes
made by those living in the world above.
249
00:24:52,400 --> 00:24:55,360
These cicadas are the lucky ones.
250
00:24:55,360 --> 00:25:00,680
Each year, more of the surface becomes concreted
over, leaving millions trapped beneath.
251
00:25:04,440 --> 00:25:06,320
It's Memorial Day.
252
00:25:06,320 --> 00:25:09,880
In the 17 years the cicadas
have spent underground,
253
00:25:09,880 --> 00:25:13,680
America has fought three wars
and had three Presidents.
254
00:25:13,680 --> 00:25:16,480
And the human world
has been transformed.
255
00:25:21,160 --> 00:25:23,560
With people absorbed
in the commemorations,
256
00:25:23,560 --> 00:25:26,400
the cicadas go mostly unnoticed.
257
00:25:27,960 --> 00:25:31,120
But all this is about to change.
258
00:25:38,680 --> 00:25:41,680
The cicada nymphs break out
of their old body,
259
00:25:41,680 --> 00:25:44,880
a miracle that can
take as little as ten minutes.
260
00:26:01,960 --> 00:26:07,080
Soon, all the cicadas undergo the
same extraordinary transformation.
261
00:26:20,760 --> 00:26:24,120
But before these crumpled wings
can fly,
262
00:26:24,120 --> 00:26:28,680
they must be pumped full of blood,
a marvel of insect hydraulics.
263
00:26:39,040 --> 00:26:41,800
Their gossamer wings
need time to harden.
264
00:26:41,800 --> 00:26:46,600
While they wait, they're often noticed by
their human neighbours for the first time.
265
00:26:51,840 --> 00:26:58,680
The combined racket reaches 100 decibels,
far louder than a jet flying overhead.
266
00:26:58,680 --> 00:27:02,960
The male makes the sound by vibrating
a drum-like organ hidden in his body.
267
00:27:16,160 --> 00:27:19,520
It's not a good time
for those with sensitive hearing.
268
00:27:23,800 --> 00:27:29,680
Adults have seen and heard it all before,
but for kids it's a totally new experience.
269
00:27:29,680 --> 00:27:32,760
One they won't see again
for 17 years.
270
00:27:41,680 --> 00:27:46,560
By appearing all together, cicadas
swamp predators with too much food to eat,
271
00:27:46,560 --> 00:27:51,480
but their trick of using such an odd
intervals of years is a masterstroke.
272
00:27:51,480 --> 00:27:55,560
It stops any predator
breeding to exploit the feast.
273
00:27:55,560 --> 00:28:01,320
They count their 17 years below ground by measuring
seasonal changes in the pressure of tree sap.
274
00:28:03,760 --> 00:28:08,560
Although millions are eaten, the majority
manage to find each other and mate.
275
00:28:19,720 --> 00:28:23,720
After mating, they use
their egg-laying tube as a saw
276
00:28:23,720 --> 00:28:27,000
to cut a slit under the bark,
laying 30 eggs in each incision.
277
00:28:29,760 --> 00:28:34,240
Job done,
they drop dead in their millions.
278
00:28:40,440 --> 00:28:44,840
Having spent the span of
a human childhood underground,
279
00:28:44,840 --> 00:28:47,200
their adult life
is over in just three weeks.
280
00:28:51,200 --> 00:28:55,440
17 years is the longest
cycle of any breeding swarm.
281
00:28:55,520 --> 00:28:58,160
Most occur once every year.
282
00:29:00,840 --> 00:29:03,920
These Cuban land crabs have
spent the last 11 months
283
00:29:03,920 --> 00:29:05,480
hidden in the rainforest.
284
00:29:05,880 --> 00:29:09,320
Today, they begin a six-mile march
back to the sea.
285
00:29:13,880 --> 00:29:17,400
The crustacean army is 100 million
strong
286
00:29:17,400 --> 00:29:20,960
and their cue to migrate
is triggered by the spring rains.
287
00:29:22,040 --> 00:29:24,320
The hordes have to cross
a coast road
288
00:29:24,320 --> 00:29:26,880
that forms a barrier
between land and sea.
289
00:29:26,880 --> 00:29:31,600
It's hardly a motorway, but for the
crabs it's an accident black spot.
290
00:29:48,600 --> 00:29:52,520
For unsuspecting drivers,
coming across the invasion
291
00:29:52,520 --> 00:29:56,760
is 2 memorable experience,
making some reach for the camera.
292
00:29:58,040 --> 00:30:01,560
Those that ignore
the crabs usually pay the price.
293
00:30:01,560 --> 00:30:04,960
One garage mends
100 punctures a day.
294
00:30:08,040 --> 00:30:12,040
Despite the carnage, the crabs
are distinctly unsentimental.
295
00:30:12,040 --> 00:30:15,520
Seizing the chance
for a roadside snack.
296
00:30:24,000 --> 00:30:27,160
Fortunately for the crabs'
ultimate survival,
297
00:30:27,160 --> 00:30:30,040
most of the millions make it
to the other side,
298
00:30:30,040 --> 00:30:32,240
then it's an easy sprint to the sea.
299
00:30:36,280 --> 00:30:38,800
Land crabs came from the ocean.
300
00:30:38,800 --> 00:30:41,760
They need to return here
to lay the eggs
301
00:30:41,760 --> 00:30:43,560
that will secure the next
generation.
302
00:30:44,720 --> 00:30:51,040
Crabs only swarm in the breeding season, but
some animals live their entire life as a swarm.
303
00:30:55,800 --> 00:30:58,720
It's May 2008
and the rains have arrived
304
00:30:58,720 --> 00:31:01,040
in the mountains of East Africa.
305
00:31:03,320 --> 00:31:07,720
One of the most organised swarms
on Earth has appeared above ground.
306
00:31:09,800 --> 00:31:14,640
They're driver ants, an insect
with a fearsome reputation.
307
00:31:19,520 --> 00:31:24,760
In the rainy season they form
these extraordinary hunting trails.
308
00:31:27,960 --> 00:31:30,320
Large soldier ants line the trail,
309
00:31:30,320 --> 00:31:33,000
protecting the smaller workers
inside.
310
00:31:33,000 --> 00:31:36,840
Their massive jaws create
an impregnable barricade.
311
00:31:39,840 --> 00:31:44,400
The soldiers create these protective
tunnels whenever they cross open ground.
312
00:31:54,160 --> 00:31:57,840
The trails radiate
from the nest in every direction,
313
00:31:57,840 --> 00:31:59,560
some stretch 100 metres.
314
00:31:59,560 --> 00:32:04,000
A worker running at full pelt
takes 45 minutes to run its length.
315
00:32:05,080 --> 00:32:08,320
The soldiers protect the trail
at any cost.
316
00:32:14,880 --> 00:32:17,560
Although blind, they're highly
sensitive
317
00:32:17,560 --> 00:32:19,520
to vibrations and air currents
318
00:32:19,520 --> 00:32:22,400
and become instantly
defensive when under attack.
319
00:32:23,560 --> 00:32:26,640
Stress pheromones put
the whole task force on alert.
320
00:32:26,640 --> 00:32:30,920
They're ready to take on anything,
including people.
321
00:32:37,360 --> 00:32:42,160
They're programmed to keep
the trail moving or die trying.
322
00:32:48,880 --> 00:32:52,000
Driver ants are the stuff of legend.
323
00:32:52,000 --> 00:32:55,400
It is said that they Kill
everything that crosses their path.
324
00:32:55,400 --> 00:32:58,680
It is said that no animal is
safe when they're on the warpath.
325
00:32:58,680 --> 00:33:02,360
It is even said that they'll enter
huts to attack people
326
00:33:02,360 --> 00:33:05,240
or kill babies left unattended
in their cots.
327
00:33:06,720 --> 00:33:12,200
BABY CRIES
328
00:33:12,200 --> 00:33:15,040
The truth is somewhat different.
329
00:33:15,040 --> 00:33:19,000
Although the bites are painful,
against people they're purely defensive.
330
00:33:19,000 --> 00:33:23,560
The jaws may slice through human flesh
like butter, but it's simply a warning.
331
00:33:29,960 --> 00:33:34,040
Despite the myths, driver ants are
still ruthless killers,
332
00:33:34,040 --> 00:33:37,280
but in a way that often benefits
the villagers.
333
00:33:37,280 --> 00:33:41,720
Dangerous pests like scorpions are
quickly set upon by the ants.
334
00:33:44,600 --> 00:33:47,400
Even the scorpion's deadly sting
is powerless
335
00:33:47,400 --> 00:33:49,280
against this invincible army.
336
00:33:49,280 --> 00:33:55,960
Both workers and soldiers join the attack,
dividing up their roles according to their size.
337
00:33:58,880 --> 00:34:04,200
As some look for a chink in its leg armour, others
prise open its body plates like a tin opener.
338
00:34:11,120 --> 00:34:15,080
With its sting immobilised and
faced by such overwhelming odds,
339
00:34:15,080 --> 00:34:18,200
the scorpion eventually
gives up the fight.
340
00:34:20,920 --> 00:34:25,760
The dismembered body is hauled back
down the trail to feed the nest.
341
00:34:37,960 --> 00:34:43,040
The farmers' fields provide even
more opportunities for the attack force.
342
00:34:45,840 --> 00:34:51,320
Pests disturbed by digging are soon
dispatched by hundreds of razor-sharp jaws.
343
00:34:53,440 --> 00:34:55,880
The ants make a clean sweep,
344
00:34:55,880 --> 00:35:01,240
capturing up to 100,000 insects
in a single raid.
345
00:35:06,280 --> 00:35:09,000
Despite the ants' formidable
reputation,
346
00:35:09,000 --> 00:35:12,160
most farmers value
their role as pest controllers.
347
00:35:13,760 --> 00:35:17,720
Their feelings about another African
swarm are equally surprising.
348
00:35:19,800 --> 00:35:22,800
Once a month throughout
the rainy season,
349
00:35:22,800 --> 00:35:27,480
mysterious clouds rise over Lake
Victoria, Africa's largest lake.
350
00:35:29,680 --> 00:35:33,880
This smoke on the water
is not quite what it seems.
351
00:35:33,880 --> 00:35:36,160
It's actually a living entity
352
00:35:36,160 --> 00:35:39,200
comprised of trillions
of individuals.
353
00:35:59,480 --> 00:36:03,520
They're lake flies, a kind of midge
that emerges from the water
354
00:36:03,520 --> 00:36:06,840
in astronomical numbers
at the time of the new moon.
355
00:36:17,800 --> 00:36:20,040
There have always been flies here,
356
00:36:20,040 --> 00:36:23,480
but increased pollution
from fertilisers and sewage,
357
00:36:23,480 --> 00:36:25,120
while damaging the lake,
358
00:36:25,120 --> 00:36:27,840
is encouraging these huge columns
of flies.
359
00:36:30,640 --> 00:36:35,520
In terms of sheer numbers, these
are now the biggest swarms on earth.
360
00:36:37,360 --> 00:36:39,760
Eventually they make landfall
361
00:36:39,760 --> 00:36:43,560
and people encounter
the flies for the first time.
362
00:36:46,880 --> 00:36:50,280
Although the air is choked
with billions of flies,
363
00:36:50,280 --> 00:36:51,840
daily life continues.
364
00:36:53,360 --> 00:36:57,560
It's rumoured that the flies can
suffocate people by sheer number.
365
00:36:57,560 --> 00:37:00,720
In reality the lake villagers
are surprisingly blase
366
00:37:00,720 --> 00:37:02,320
about this living smog.
367
00:37:05,200 --> 00:37:09,840
Like many swarms, the midges emerge
together to swamp predators
368
00:37:09,840 --> 00:37:12,520
with too much food to eat
at any one time.
369
00:37:12,520 --> 00:37:14,400
Birds even migrate to the lake
370
00:37:14,400 --> 00:37:17,120
to make the most of this monthly
free lunch.
371
00:37:32,080 --> 00:37:33,720
But it's not only birds
372
00:37:33,720 --> 00:37:37,160
that can't bear to see so much
protein go to waste.
373
00:37:54,760 --> 00:37:59,800
Such incredible quantity of biomass
is equivalent to huge herds of game,
374
00:37:59,800 --> 00:38:01,880
but far easier to catch.
375
00:38:03,200 --> 00:38:07,240
A frying pan
makes the perfect weapon.
376
00:38:13,040 --> 00:38:18,600
The flies are so valuable
the whole village joins in the hunt.
377
00:38:18,600 --> 00:38:23,520
The saucepans have been dampened first to
make the flies stick and then clump together.
378
00:38:26,880 --> 00:38:28,640
These midges are so nutritious,
379
00:38:28,640 --> 00:38:31,360
they're valued as a supplement
to the local diet.
380
00:38:44,080 --> 00:38:46,720
Each patty contains
half a million flies
381
00:38:46,720 --> 00:38:50,720
and has seven times more
protein than the average beefburger.
382
00:38:55,080 --> 00:38:58,640
For people who have little protein
in their diet,
383
00:38:58,640 --> 00:39:01,120
this burger bar
is a health food centre.
384
00:39:03,480 --> 00:39:05,760
Each village has its own recipes,
385
00:39:05,760 --> 00:39:08,640
but fly burgers always
go like hot cakes.
386
00:39:13,080 --> 00:39:19,600
In times of famine, this traditional method of dealing
with the monthly invasion becomes ever more relevant.
387
00:39:25,280 --> 00:39:29,320
Both ants and flies are
swarms with a positive side,
388
00:39:29,320 --> 00:39:33,360
but one African plague
has no such redeeming features.
389
00:39:33,880 --> 00:39:37,960
These are the most numerous birds
on Earth with a growing population
390
00:39:37,960 --> 00:39:40,720
that may now be more
than ten billion.
391
00:39:45,880 --> 00:39:49,760
The largest flock on record
consisted of over 40 million birds
392
00:39:49,760 --> 00:39:53,480
and took five hours to pass.
393
00:39:57,040 --> 00:39:59,640
Sometimes known as the locust bird,
394
00:39:59,640 --> 00:40:02,720
these are quelea, a type of weaver.
395
00:40:06,080 --> 00:40:09,960
They follow the seasonal rains
in an endless search for food.
396
00:40:17,720 --> 00:40:21,600
They eat grass seeds but,
unfortunately for African farmers,
397
00:40:21,600 --> 00:40:25,640
they prefer the more succulent
domesticated varieties,
398
00:40:25,640 --> 00:40:28,360
getting through 10,000 tonnes a day.
399
00:40:28,360 --> 00:40:34,440
Smaller parties break off from the main flock
to make sneaky raids on the farmers' fields.
400
00:40:36,880 --> 00:40:39,320
Even a relatively small flock
will demolish
401
00:40:39,320 --> 00:40:41,280
an acre of rice in less
than an hour.
402
00:40:41,280 --> 00:40:45,400
SCREAMING
403
00:40:45,400 --> 00:40:47,240
Subsistence farmers suffer the most.
404
00:40:47,240 --> 00:40:50,880
It's a full-time occupation
keeping the crop raiders at bay.
405
00:40:50,880 --> 00:40:52,760
HE SHOUTS
406
00:40:55,440 --> 00:40:57,720
It's like trying to dam
an ever-flowing river.
407
00:40:57,720 --> 00:41:00,400
As the flocks separate and reform,
408
00:41:00,400 --> 00:41:04,280
predicting where they might land
is anyone's guess.
409
00:41:04,280 --> 00:41:06,360
With their livelihood at stake,
410
00:41:06,360 --> 00:41:08,840
the whole village creates
a taskforce
411
00:41:08,840 --> 00:41:10,680
to try to stop them settling.
412
00:41:10,680 --> 00:41:12,800
HE BANGS DRUM AND SHOUTS
413
00:41:17,640 --> 00:41:21,560
A flock of one million quelea
consume 60 tonnes of food a day
414
00:41:21,560 --> 00:41:23,920
but, as they're always on the move,
415
00:41:23,920 --> 00:41:26,600
they're almost impossible
to control.
416
00:41:28,160 --> 00:41:32,000
Only when the birds roost
do the farmers get some respite.
417
00:41:34,800 --> 00:41:38,280
Eventually the birds have
to stop their endless travelling.
418
00:41:38,280 --> 00:41:42,080
Nesting is their most vulnerable
time.
419
00:41:43,720 --> 00:41:46,880
The red-billed males
do the main work,
420
00:41:46,880 --> 00:41:49,200
weaving up to 20 of these intricate,
421
00:41:49,200 --> 00:41:52,160
bowl-shaped nests to attract
different females.
422
00:42:01,560 --> 00:42:05,960
He takes the greatest of care, as
his quality of work is being judged.
423
00:42:12,320 --> 00:42:14,720
Only the finest weaving
passes the test.
424
00:42:16,800 --> 00:42:19,240
If she approves, she moves inside.
425
00:42:24,000 --> 00:42:28,000
But stopping to breed
has made them vulnerable.
426
00:42:38,000 --> 00:42:43,200
A colony may cover four square miles
and hold 300,000 birds,
427
00:42:43,200 --> 00:42:46,960
all breeding
a new generation of crop raiders.
428
00:42:46,960 --> 00:42:50,240
As sunset draws the birds back
to the nest,
429
00:42:50,240 --> 00:42:54,640
they pay the ultimate
price for feeding off our success.
430
00:42:54,640 --> 00:42:57,800
COUNTDOWN IS SHOUTED
431
00:43:14,880 --> 00:43:18,920
In the birds' world,
this is Armageddon.
432
00:43:20,520 --> 00:43:24,560
Over 100,000 annihilated
in a single blast.
433
00:43:28,040 --> 00:43:32,520
The inferno brings temporary relief
to nearby farmers but does nothing
434
00:43:32,520 --> 00:43:37,600
to stop the ever-expanding growth
of Africa's quelea population.
435
00:43:37,600 --> 00:43:41,120
We may unintentionally
encourage swarms
436
00:43:41,120 --> 00:43:43,120
but we cannot control them.
437
00:43:43,520 --> 00:43:44,880
It's August 2008.
438
00:43:44,880 --> 00:43:48,120
In the Mississippi and its many
tributaries,
439
00:43:48,120 --> 00:43:50,840
a purely man-made swarm
is on the rise.
440
00:44:04,720 --> 00:44:07,920
In the 1970s,
silver carp were accidentally
441
00:44:07,920 --> 00:44:11,760
introduced into these waters
after escaping from a fish farm.
442
00:44:17,880 --> 00:44:21,800
They now outnumber local fish
by 10-1.
443
00:44:24,960 --> 00:44:27,400
They have some truly
bizarre behaviour.
444
00:44:35,760 --> 00:44:38,640
Some can clear
three metres in a single leap.
445
00:44:54,120 --> 00:44:58,320
They say when fish are leaping,
it's good for anglers.
446
00:44:58,320 --> 00:45:00,920
It's certainly the case
in this part of the river.
447
00:45:06,440 --> 00:45:09,280
Here, fishermen don't
even need a rod and line.
448
00:45:09,280 --> 00:45:13,080
Fish are only too willing
to do the job for them.
449
00:45:17,200 --> 00:45:19,720
It's a phenomenon
that takes some getting used to.
450
00:45:21,680 --> 00:45:23,280
Whoal!
451
00:45:23,280 --> 00:45:25,600
I got him too! There's a guy.
452
00:45:25,600 --> 00:45:28,000
Look out!
SQUEALING
453
00:45:28,000 --> 00:45:29,520
Hey!
LAUGHTER
454
00:45:34,240 --> 00:45:36,000
That could be cut bait.
455
00:45:36,000 --> 00:45:37,480
That could be cut bait.
456
00:45:39,680 --> 00:45:43,440
Hey! We don't even have to get
the fishing pole wet! Look out!
457
00:45:46,440 --> 00:45:49,480
Damn it, let's eat that
thing, see what it tastes like!
458
00:45:50,680 --> 00:45:52,920
It's not just anglers
who are affected.
459
00:45:52,920 --> 00:45:56,320
Pleasure craft
have to run the gauntlet too.
460
00:46:13,520 --> 00:46:17,040
The secret of this extraordinary
behaviour lies in the boats' motors.
461
00:46:19,000 --> 00:46:21,880
The fish mistake pressure waves
from the propeller
462
00:46:21,880 --> 00:46:23,520
for the movement of predators
463
00:46:23,520 --> 00:46:25,800
and literally jump with fright.
464
00:46:33,720 --> 00:46:36,720
They react in alarm
to every passing boat.
465
00:46:47,360 --> 00:46:49,640
With numbers close to
bursting point,
466
00:46:49,640 --> 00:46:52,000
each leaping fish scares
its neighbour,
467
00:46:52,000 --> 00:46:54,160
creating a dangerous chain reaction.
468
00:46:57,880 --> 00:47:02,200
As some weigh over 40 pounds,
collisions can be deadly.
469
00:47:09,360 --> 00:47:13,400
In some parts of the river, 200 fish
missiles can launch at any one time.
470
00:47:13,400 --> 00:47:16,640
They've already caused
serious injuries and,
471
00:47:16,640 --> 00:47:20,720
as they spread to other rivers,
the danger increases by the day.
472
00:47:28,400 --> 00:47:32,520
Silver carp are a swarm
that we accidentally created,
473
00:47:32,520 --> 00:47:36,960
living proof that, as we interfere
with the balance of nature,
474
00:47:36,960 --> 00:47:38,560
we create more swarms.
475
00:47:43,000 --> 00:47:46,360
The honey bee is the only swarm
we have ever domesticated,
476
00:47:46,360 --> 00:47:48,800
but we're still unravelling
the mysteries
477
00:47:48,800 --> 00:47:50,360
of much of their behaviour.
478
00:47:56,840 --> 00:47:59,800
For those who understand
the swarm's inner mind,
479
00:47:59,800 --> 00:48:03,880
it's possible to control them in
a way that is quite extraordinary.
480
00:48:14,960 --> 00:48:18,360
The bees are being summoned
by a secret signal,
481
00:48:18,360 --> 00:48:21,520
one that causes
them to act with a single mind.
482
00:48:26,320 --> 00:48:29,520
Swarms are made
from thousands of organisms
483
00:48:29,520 --> 00:48:31,680
but they work by acting as one.
484
00:48:38,920 --> 00:48:41,760
By understanding the swarm's
secret language,
485
00:48:41,760 --> 00:48:45,200
it's possible to make them
do the most extraordinary things.
486
00:49:12,320 --> 00:49:17,640
100,000 bees cover his body,
creating a living suit.
487
00:49:27,120 --> 00:49:32,800
He has such control over the bees
he rarely suffers a single sting.
488
00:49:37,920 --> 00:49:40,040
He is a professor of entomology,
489
00:49:40,040 --> 00:49:44,120
and has been studying bees and
their communication all his life.
490
00:49:47,440 --> 00:49:50,800
By covering his body with
the pheromone that the queen bee
491
00:49:50,800 --> 00:49:54,680
uses to control her hive,
he has them at his command.
492
00:49:54,680 --> 00:49:57,840
They react by protecting
him with their bodies.
493
00:50:04,720 --> 00:50:08,680
To them, he is the queen bee.
494
00:50:13,160 --> 00:50:16,960
Using science, he has learnt
to control what most of us dread,
495
00:50:16,960 --> 00:50:19,160
and the result is quite disturbing.
496
00:50:24,680 --> 00:50:27,040
As he brings a swarm into our world,
497
00:50:27,040 --> 00:50:29,920
people are forced
to confront their fears.
498
00:50:33,280 --> 00:50:36,480
They also see that, with knowledge,
499
00:50:36,480 --> 00:50:40,240
such an incredible force
of nature can be controlled.
500
00:50:41,240 --> 00:50:44,840
When swarms invade,
we are inevitably separated
501
00:50:44,840 --> 00:50:46,960
by an invisible barrier created
502
00:50:46,960 --> 00:50:49,680
by our different senses
and perceptions.
503
00:50:51,160 --> 00:50:55,800
Swarms may share our world but the
gulf between us couldn't be greater.
504
00:51:01,640 --> 00:51:06,960
To control the swarm, we need to
understand how they see the world.
505
00:51:08,880 --> 00:51:13,640
But swarms not only experience
things differently from us,
506
00:51:13,640 --> 00:51:16,160
they think in a different way too.
507
00:51:23,440 --> 00:51:29,040
The next programme will explore
the extraordinary alien intelligence
508
00:51:29,040 --> 00:51:30,920
that controls the swarm.
44839
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