Episode 1 Nature's Weirdest Events

No matter how well we think we know

our planet, the natural world still

has the ability to surprise us,

to shock us and maybe sometimes even

to scare us with its extraordinary

events and bizarre behaviour.

And new technology means

that nature's weirdest phenomena

are being caught ever more readily

on camera.

So we're going to bring you

the strangest stories

our world has to offer.

To kick off, we're going to look at

some of nature's weirdest romantics.

The shores of Lake Erie on America's

beautiful border with Canada

have always been a tranquil place

of peace and quiet.

Until, early in the summer of 2010,

it became the setting for a swarm

of phenomenal proportions.

This gas station is being

attacked by...something.

And that lady

won't even get out of her car.

It's like it's snowing.

A swarm of literally billions

stretched over a mile inland

and for miles

along the western shore.

Local resident Greg Stewart

recalls the experience.

They were all over the wall

of the city,

and I didn't know if I should even

get out of my car, it was that bad.

And, as I got out, they started

crunching under my feet.

Then, within days,

they spontaneously started to die

in their billions.

Seriously, a pile of bugs.

The drifts of dead bodies got

so deep that the local authorities

had to use snow ploughs

to unblock the roads.

And, as they started to break down,

they left another treat, too.

It smelled of motor oil and vomit.

So what were these insects,

and what could have caused

such an extraordinary plague?

Don Schloesser is an expert

in the wildlife of Lake Erie

The big swarms are really the result

of the life history pattern

of the western Lake Erie mayflies.

They live in the mud for about two

years and they grow and they moult.

About the middle of May,

the first of June,

they all come

out of the water at one time.

go back out into the water

to lay the eggs.

And then the whole process

starts all over again.

Mayfly spend about 99%

of their lives

as aquatic larvae at the bottom

of ponds and rivers.

They spend their time feeding

and growing

until, in a cunning plan

to avoid getting eaten,

they all emerge en masse to mate.

The first few are easy pickings.

But soon the sheer numbers

overwhelm predators -

they simply can't make a dent

in the overall population.

After about two days,

there's a swarm,

a swirling swarm like

a little funnel cloud

that's formed by the mayflies.

And what happens is the females

jump into that swarm,

they are fertilized in the air.

Once they have mated, the male dies

and the female heads out

over the water

to release her fertilised eggs

before she too passes away.

The entire process takes

just a matter of days.

Each year, as the event

comes to an abrupt end,

it's all hands on deck for the task

of clearing up the dead.

But there's still a lot of questions

surrounding their mass emergence.

When they come out is still

a mystery to us.

We can't predict very well in that

two- or three-week period

when they are actually going

to be coming out.

Sometimes it is related to

storm events,

sometimes it is related to rain

events, but somehow

the mayflies all get a cue when they

are down in the bottom of the lake.

But why are there

so many in Lake Erie?

Lake Erie supplies

the types of sediment

that this critter

likes to burrow into.

It used to have mayflies

many years ago,

then they went away

for many years due to pollution.

Now they're back and they've

come back with sort of a vengeance

in terms of the numbers

and the abundances

that we see come out of the water.

So this almighty insect orgy

is all down

to a particularly perfect

set of conditions.

The enormous size of the lake and

its newly clean waters contribute to

a swarm so large that it can bring

a whole city to a grinding halt.

No-one likes a relationship

that's all give and no take.

Coming up next, a few love affairs

that have become

a little bit too one-sided -

from the worm

with an eye on a new home

to the fly whose young

play hard to get out.

We investigate nature's weird world

of the unwanted guest.

Back in 2009, climbing expert

Tim Fogg arrived back in the UK

from a trip to the

Central African Republic.

Nothing odd to report,

until one day...this happened.

Suddenly, my hand swelled up

for no apparent reason.

ten days later my arm swelled up

and then it went down.

Just bits of me kept swelling up.

As a rope access specialist,

Tim has travelled

to some of the world's most

bizarre and extreme environments,

but never before had his body parts

randomly swollen

for no apparent reason.

This bizarre bodily behaviour

continued for two years.

So what could be causing

these spontaneous swellings?

After several medical tests,

Tim was diagnosed as having

contracted loa loa,

or the African eye worm.

It gets its gruesome name from

the only time it becomes visible

in infected humans -

as it passes through

its host's eyeballs.

It's an incredible parasite

that's carried by certain types

of day biting flies

in the swamps of west Africa,

exactly where Tim had returned

home from two years earlier.

I think I got it wading through

a load of mud in the forest where

mango flies live, which is

the thing that transmits it.

Infection occurs

when the larvae of the worm

are passed to a human

as the fly bites.

The larvae then develop under

the skin until they become adults

and start their travels

around the body.

As they move about under the skin,

the immune system

starts to react and it's this

that causes the swelling.

I guess it was in my hand

to start with,

it presumably went up one arm

then my other arm swelled up,

so presumably somehow it got

right across my shoulder

and down into the other arm.

Or maybe it was another worm.

I have no idea.

Incredibly, the worm can grow to

be seven centimetres long and live

for 17 years creeping around under

the surface of the host's body.

for 17 years creeping around under

the surface of the host's body.

The worst thing about this thing

wandering about under your skin

is its habit of coming up to your eye

and wandering across your eye and

across the bridge of your nose

and into the other eye.

And that is apparently very,

very painful.

And I did have one incident where

the side of my face swelled up

which meant it was there,

it was getting close

and thinking about going

across my eye.

Luckily, it changed its mind.

The beauty of this parasite

is that it doesn't hurt you at all,

and it didn't make me feel ill.

It was just the swelling,

so it's very clever.

I mean, it just wants to feed off me,

it doesn't want to give me

bother if it can, cos I might

get rid of it.

After he was diagnosed in 2011,

Tim's doctor put him

on an intensive course of drugs,

and a year later in June 2012

he was deemed tentatively clear

of his tenacious little body mate.

Our last story is more body

burrowing than bunny boiling,

a gruesome but truly ingenious

example of nature's

weird relationships gone bad.

And so to Panama, where an innocent

traveller has picked up

a couple of unwanted passengers.

Do you see it? Right there.

What started as two small insect

bites has become swollen and angry.

It's ready to come out.

Yeah, it is.

And there was something inside.

Whatever they were simply

had to be extracted.

They are big. I can feel it trying to

pull back in. Gross.

That's huge!

So, what on earth are they?

Dr Mark Rowland works at

the London School Of Hygiene

and Tropical Medicine

and has travelled the world

studying parasites.

Those insects that we are trying to

pull out of people's bodies are

the larvae of the botfly and I have

some here, pickled inside this jar.

They are quite large. They are about

one and a half centimetres long.

But how does something this big get

under your skin in the first place?

The botfly itself is quite large,

it's about the size

of a bumblebee, so if it were

to actually land on a host itself,

it would probably be detected

by the human or by the cattle or pig

and be brushed away.

That makes it

less likely for the fly

to succeed in laying its eggs

successfully on the host.

So the botfly has come up with

a very sneaky tactic.

What the fly has cleverly done

is to grab,

usually an insect like a mosquito

or a tick or even a housefly.

After a quick air ambush,

the botfly pins down the fly

and quickly attaches its eggs.

And then off it goes to do

the botfly's dirty work.

On contacting the human, or animal

host, the small botfly larvae

inside the egg will be able

to detect the warmth of the host,

and it will hatch at that point.

And it does this very

quickly indeed.

The larvae is able to penetrate

and embed itself

in the skin of the host.

Over the course of several

weeks, it will grow

and eat its way into the flesh.

And just in case you were thinking

of getting rid of it at that stage,

it has spiny bristles

that hold it in

and make it impossible to pull out.

Oh, my God! Oh, God!

That definitely is the trick,

man, overnight.

The only way to win this tug of war

is to play dirty.

One trick that you can do to make

it easier is to

smear a gel or fat

over the rear end of the larvae.

This will block the breathing

tubes of the larvae.

That makes it easier to actually

draw the larvae from the body.

Only when you've cut off its air

supply will the botfly let go.

Of course, the other option is

to let nature take its course

and wait six weeks for the larva

to become a maggot,

eat its way out and drop onto the

ground before becoming an adult fly.

It's a nasty business,

however they exit.

But after all of this, you should

just end up with a little scar -

no problem.

What all of the stories in

this programme seem to illustrate

is that a bit of understanding

and tolerance help in all

of our relationships.

So, if we can implement

a bit of love and respect

towards all of nature's wonders,

there's absolutely no doubt that

the world would be a richer place.

And of course,

the world is always getting smaller.

So as we welcome more and more

of these bizarre creatures

into our own back-yards,

what we think of as weird now

might be a lot weirder

in the future.