Episode 1 Nature's Weirdest Events

The modern world is connected like never before -

the very instant that something new, unexpected

or downright strange happens,

it's captured, uploaded

and shared around the planet.

That means that natural events that would've been dismissed as hearsay,

urban legend or simply flights of fancy just a few years ago

now come with good, first hand documentary evidence.

From a mystery giant,

terrorising the residents of an Australian neighbourhood...

Oh, my goodness.

SHRIEK

..to a sea of green gunge along the Chinese coast...

..and something strange in the Caribbean.

Can you see them?

Whoa!

Using eyewitness testimony,

leading experts and the top scientific brains,

we are going to try to explain what on earth is going on

with these weird natural events.

Right, to kick off...

..we start by taking the plunge, with some marine mysteries.

There's danger lurking in the fish tank...

..and a predator making a big splash.

My wife was just screaming at the top of her lungs.

But first, we head to the Caribbean.

With perfect beaches and idyllic waters...

..the islands of the Bahamas are a dream destination.

But something unexpected is taking to the water.

All of a sudden, these things

were beginning to swim towards the boat.

Which way are they?

And I don't know what they are.

Why are they in the water?

Oh, my God!

You guys, help us out - which way?

I was trying to swim around them quickly

and they were...faster than me.

Can you see them?

They were shooting every direction, these legs.

SHOUTING

But they were swimming fast.

It was one of the most unusual things I've seen in my entire life.

So here in paradise,

just what is stalking these swimmers?

Mike Corey is a film-maker from Canada

and in 2011, he was working in the Caribbean.

And he headed out to the tiny uninhabited island of Big Major Cay.

That day, I was getting really excited to see sharks.

We stopped for a lunch break

and the boat operator got this big bag of...

It was lettuce heads, French fries, just food scraps.

And they were starting to dump it in the water, next to the boat.

All of a sudden, these...things

started bolting out of the woods.

They were black, they were white, they were brown,

I almost thought they were dogs...

DOG BARKS

Goats... GOAT BLEATS

..I didn't really know.

I didn't expect them to go into the water next.

Mike couldn't work out what they were.

But as they got closer,

he realised, that gliding through the waves towards him...

were swimming pigs.

PIG WHINES

-The world's a crazy place.

-Look at it!

I didn't know pigs could swim.

We swam with them - I had my camera.

Their feet were going crazy karate chops, every single direction.

There were stingrays underneath, fish all around us -

it was a beautiful day.

One of the best days of my life, I'd say.

Now, pigs may not be able to fly,

but why do they need to swim?

Well, in fact, paddling pigs have been known for some time

and they're actually pretty good at it -

as this footage of the late great Ralph the swimming pig shows.

In his heyday, in 1970s Texas,

he would enthral up to 350,000 visitors

at Aquarena Springs.

And pigs are one of the few animals

that don't have functional sweat glands,

so to cool themselves down,

they need to wallow in mud or water.

So it makes sense for them to know how to swim.

They were better swimmers than we were.

I was trying to swim around them quickly and they were...

faster than me.

The pigs were flailing their little pool cue hooves every direction.

We had to kind of dodge around those, they were sharp.

Well, I guess if you're a big animal like that

and you've got some body fat, you'd float quite well.

But pigs aren't usually found

living on deserted islands in the Caribbean.

So the big question is,

how did these porcine paddlers end up in paradise?

The theories about how they got here have become local legends.

Could they have swum from another inhabited island?

Well, in Scotland,

two baby boar have recently been spotted making the 1.5 km swim

from the Isle of Longa back to the mainland,

so it's a possibility.

Or perhaps these Caribbean pigs

are descendants of a few that were once shipwrecked.

Mike has found out about yet another story.

From what I heard, there was a boy with a pig

and he was scared his pig was going to get eaten

by his family and his father.

So he stole the pig away, put it on this island

and would go every day to feed the pig.

And after a while, more pigs arrived

and he would still go and feed these animals.

No-one knows exactly what happened,

but the most likely explanation

is that they were introduced by locals.

But what's in no doubt

is that once they got to the island, they thrived.

And now, there are around 40 pigs that call this place home.

So how have they been so successful?

Well, I've got to tell you - pigs are clever.

In fact, they're sometimes described as the world's 4th smartest animal.

And they use this brain power

to find food in the wild.

So, stranded on a Caribbean island,

they've learned a new way to get a free and nutritious meal.

Rather than spend hours digging and searching for food,

they've realised they can get hand-outs from passing boats.

If I was a pig

and I was stranded on a desert island and I saw a boat,

I don't know if I would have the brains to just jump in the water,

dodge the sharks, the stingrays -

all of those things to go out and see if I could get lunch.

But that's exactly what they've learned to do.

The pigs have claimed this piece of paradise for themselves.

And Pig Island really is a testament to the tenacity,

the resourcefulness

and the pioneering spirit of the not-so-humble pig.

Now, from the bliss of the Caribbean

to a hidden danger

that could be lurking in your own home.

Miami, in the USA.

Life is usually pretty laid back in this sun-drenched city.

But away from the beach,

an invisible killer is on the loose.

Bryan Kutcher is the owner of an aquarium shop,

specialising in tropical fish and living coral.

And he has seen a lot of strange things in his time.

We've had fish give birth, a shark hatch out of an egg,

um, blue-ringed octopus...

But I've never seen anything mind-blowing as this.

In January of 2013,

Bryan noticed something pretty unusual.

Everyday we come in the shop and we go through all our corals

and make sure nothing has fallen, everything looks healthy

and I noticed when I came in in the morning,

all the corals were pulled to the middle of the rocks.

So I pulled them all back out and I explain to everybody,

if you're going to clean the glass,

to please move the corals back when you're done.

Everybody kind of denied it and said they didn't do it.

The finger of blame pointed at some of Bryan's colleagues.

So he really wasn't happy when it happened again.

I was starting to get upset with everybody, cos I thought

that they were actually just not bringing them back

to where they were supposed to be.

The following day, we got a coral shipment in.

There's a coral called the "finger leather", which is a soft coral.

I put it in, came back next morning

and it was only about a half inch on each tentacle.

Something had eaten about three to four inches.

This was extremely odd.

But what Bryan didn't know

was that similar reports were coming in from all around the world.

And the victims weren't just corals...

..but entire fish, eaten alive.

So who - or what -

was responsible for this aquarium atrocity?

Bryan wanted to investigate.

I decided to take all the rock out of the aquarium

and at that point, the aquarium was extremely murky, it was cloudy

and out of nowhere,

this giant thing just started swimming around the tank.

It was like mayhem, we were in the tank, trying to go everywhere,

trying to catch this thing, that we didn't really know what it was...

The reaction was crazy. "Oh, my God, get a net - what is that?"

And this is what Bryan caught -

It's a bobbit worm.

This bizarre looking creature

usually lives in the waters of the Indo-Pacific ocean.

But that's not the half of it.

Because this turned out to be the size of a snake!

And shockingly,

other people are finding them lurking in their tanks too.

Wow, that thing is massive!

It is quite revolting.

Oh, it's huge, Goops...

I can't believe I've never seen him, though.

This mega-worm can grow up to three metres in length..

In the wild, they hide in the sediment on the ocean floor,

using their highly tuned antennae to sense prey.

When an unfortunate fish comes by,

it strikes in a split second,

as if from nowhere.

Someone who can vouch for the worm's deadly bite

is Emma Sherlock,

the curator of invertebrates at the Natural History Museum in London.

They are really, really powerful animals.

They will attack with their jaws

and it can be so fast and so vicious,

they can actually snap fish in two.

Definitely wouldn't want to get your fingers too close to these guys,

because they've got really muscular pharynx

and definitely give you a nasty nip.

This is a highly weaponised worm,

not to be messed with.

But there's still one thing that doesn't add up.

It's something that's been in this aquarium for a very long time,

that we never noticed

and we're in and out of the aquarium probably...

30 times a day, 20 times a day.

So how can a giant worm stay hidden in a fish tank?

It seems staggering to people.

But actually,

what's happening is that when these animals are very small,

they can fit very easily into little crevices

in rocks and corals

and when you're making up your aquarium,

you put in these bits of coral,

unknowing of what's lurking inside.

As the bobbit worm grows,

it hides under the sand and rocks.

The only sign of its presence

is the ever-increasing list of missing aquarium animals.

And it's fantastic at basically playing a big game of hide and seek

and so people don't actually know they're there,

until they see the damage that they cause.

Now, when we build aquariums,

I'm always wondering what I'm going to find in the rocks.

I'm wondering what I grab. Sometimes I wear gloves.

I always wonder if something's going to pop out...

As far as a four foot worm would be amazing,

but it's always on my mind now.

Who ever would have thought

that there would be an organism as monstrous as the bobbit worm

living in a fish tank?

But you know, it does go to prove that in nature,

if ever there's an opportunity,

if ever there's a resource,

something will evolve to exploit it.

For our next event,

we go to the west coast of Mexico

and to an ocean predator on a completely different scale.

In 2011,

keen scuba divers Laura Howard and her husband, Richard

decided to celebrate their 20th anniversary

by doing something special.

So they headed down to Baja in Mexico,

for the holiday of a lifetime.

This is the view from our beautiful, beautiful room.

My husband loves underwater photography.

We were scuba diving for the week - so excited about that.

This part of the world is known for its magnificent underwater life

and it wasn't long before they were meeting the locals.

But on the second day, their dive was cut short,

when the boat's captain reported

seeing something strange off the boat.

The couple went for a closer look.

Out at the front, everything was calm.

But out back, it was about to kick off.

Whoo! Whoo!

You got to be kidding me! 'Oh, my goodness...'

These are killer whales. These are orca!

Oh, my God!

'I mean, there we have these enormous animals...'

I mean, they're at the top of the food chain.

And they're inches off the back of our boat.

Whale breath just sprayed in my face, sprayed on the camera.

They were huge, they were massive, they were bigger than the boat.

And as we're looking around, there's not just one or two,

there's about 20 in this pod.

So why were these killer whales chasing the boat that day?

And what were they after?

Killer whales, or orca,

are some of the ocean's largest and most powerful predators.

They're intelligent, organised and ruthless.

They're a true force to be reckoned with.

The two types of killer whale that we know best know

are resident and transient killer whales.

Now, the resident groups tend to stay around coastlines

and predominantly feed on fish,

whereas the transient killer whales are fearsome hunters,

roaming the oceans, looking for seals, sea lions

and even whales to prey upon.

So if we know they're capable of that...

Right here, right here.

..perhaps the killer whales saw Richard and Laura as lunch?

Even being on a boat doesn't necessarily mean you're safe.

When Weddell seals are found resting out of the water in Antarctica,

it's no problem for the orca.

The pod swim towards the iceberg in unison,

to create a wave that topples the seal into the water.

And I'm afraid there's only one winner.

So have these Mexican killers learned a similar trick?

Well, perhaps the answer lies with some of their relatives?

Despite the name, killer whales, are in fact,

the largest member of the dolphin family.

And smaller dolphins are known for surfing waves

and riding the bows of boats.

So is there a link?

The one man who can help shed some light on this mystery

is zoologist Mark Cawardine.

It's amazing how many times I've been on a boat,

travelling in one direction

and you're passing a school of dolphins

and they will turn around 180 degrees

to come up to the boat and play with it.

And they've obviously realised over the years

that boats just mean fun.

This behaviour, though, actually evolved

long before the dolphins had boats to create the perfect ride.

You get a big whale like a blue whale,

like the size of a Boeing 737,

these little tiddly dolphins will race around the blue whale

and annoy it and the whale will surge, you know?

Just out of frustration and anger maybe

and create a bow wave in front of it

and the dolphin would get a few seconds of just

playing in the bow wave.

When boats and ships came along,

they couldn't have believed their luck,

because there are these things that are creating bow waves

all day long, all night long and they can play as much as they want.

There is still one crucial difference, though.

The dolphins are being pushed along at the front of boat.

But on this day in Mexico,

the killers were at the back,

in the boat's wake.

So can this really be the same thing?

Well, there's no doubt the whales will have gone to the boat

because they just wanted to have a good time.

But this type of play behaviour isn't exclusively for fun.

Swimming close together, they're actually learning to hunt.

It's quite a useful technique to develop and learn,

because it's useful in hunting, you know?

They'll be working as a team when they're hunting

and they'll instinctively know when to take over,

when to move position.

This orchestrated training session

gives the killer whales an advantage when it comes to a real hunt.

Building stamina and developing teamwork

in this man-made surf school.

So, although it looks like

Richard and Laura weren't on the menu that day,

it is entirely possible that the killer whales

were using the boat to fine-tune their hunting skills -

the skills that make killer whales

one of the most feared predators in the ocean.

What all these events show

is that ocean is a fascinating source of weird surprises,

whether it's pigs in paradise,

a worm the size of snake...

..or a killer whale academy.

With the ocean covering 71% of the earth's surface,

it makes you wonder what else is out there.

Whilst it's easy to be impressed

by big, bold and brazen displays of behaviour,

our next set of stories is no less astonishing

and it pits the small against the mighty.

Coming up, a wasp that seems to have a death wish...

..and a stoat that appears to have lost its mind.

But first, to North America and to the United States...

..famous for fast food

and dedicated meat-eaters.

On average, Americans eat 125 kg of meat

every single year -

if any nation could be said to be built on the stuff,

this is it.

But the burgers have gone bad.

Almost overnight, people have started to suffer

life-threatening allergic reactions to meat...

I was fighting for air and I was having difficulty breathing.

I was going to pass out on my feet.

..and it's spreading,

taking down even the most devoted carnivores.

Hamburger, ribs, meatloaf, meatballs, bacon -

all off my list.

Never in my life did I imagine something like this

would change my life so drastically.

Fred Marienfeld is a physical education coach from Long Island.

In August 2011,

his world collapsed.

I was out playing softball one evening and I came home

and had a normal meal - threw a couple of hamburgers on the grill

and cooked them up had some dinner

and watched the ball game for a little while and went to bed.

About four o'clock in the morning,

I woke up and I was covered in hives, from head to toe.

Itching, scratching - I couldn't get any relief -

it just came out of nowhere

and I knew I was having a reaction, but to what, I didn't know.

It was extremely serious.

I couldn't breath,

I couldn't get enough air, I was actually gasping for air,

thinking I had a blockage in my airway.

My wife got me in the car and took me to the emergency room.

But being rushed to hospital was just the start of Fred's ordeal.

After leaving the emergency room,

I made an appointment to see an allergist, just to kind of...

To figure what exactly was causing this reaction in me.

After a series of tests,

Fred was told he was allergic to red meat.

Completely off my diet -

bacon, cheeseburgers, meatballs, meatloaf, ribs - no more.

It was crushing.

So who or what had caused this terrible reaction?

And would Fred ever be able to eat meat again?

Dr Erin McGintee is Fred's allergist

and she was instrumental in unravelling this meaty mystery.

So the first patient I ended up diagnosing with this allergy

was in 2010.

It was one of those things where you think,

"Oh, that's crazy, nobody's allergic to meat."

But they were.

And it only got crazier.

Erin started to see an increase in these meat allergies,

but doctors in other parts of the states

weren't seeing the same pattern.

So what was going on?

Perhaps the meat was contaminated -

or was it something else entirely?

One of my patients suspected he was allergic to shellfish,

because he had a couple of episodes hours after eating shellfish.

But then he said, but the most recent time it happened,

I hadn't even eaten shellfish.

One by one,

all the usual suspects were ruled out.

But finally, Erin had a breakthrough.

It wasn't that the meat had changed -

it was Fred.

And the culprit was lurking in the grass.

The Lone Star Tick.

But what was the connection?

Now, ticks are small parasites,

that specialise in sucking the blood of vertebrates.

They're the sort of vampires of the parasite world.

They lie in wait, often in long grass

and use special sensory organs at the tip of their front legs

to detect the presence of a host.

When a target comes by,

they make their move.

And the victim doesn't feel a thing.

The tick saliva contains anaesthetic properties.

By the time Fred realised he'd been bitten,

it was too late.

OK, so we know who dunnit,

but how on earth is this tiny tick

forcing people to become vegetarian?

All non-primate mammals express a carbohydrate called alpha-gal

throughout all the cells in their body.

When we eat it normally, it doesn't cause us a problem,

it's not dangerous to people.

We've been eating meat our whole life - it's not a problem.

But ticks can pick up this alpha-gal when they feed from mammals

and it stays inside them.

When a tick bites a human,

a small amount of this alpha-gal

gets transferred into the bloodstream.

And this is when it becomes a problem.

So what happens when alpha-gal gets into the body?

Well, let's imagine that this row of sweets here is your bloodstream.

These are all of the red blood corpuscles.

What scientists think is that when the tick bites you,

it introduces a small amount of alpha-gal that's been left there

from its last meal - maybe when it bit a deer, or something like that.

Now, the body doesn't like this,

so it produces proteins called antibodies

and these attach themselves to the outside of any toxin or bacteria

and render it harmless.

Job done.

But, of course, the body keeps a template of these antibodies,

so that if the toxin appears again, it can react immediately.

But then what happens is that you have a massive meal of meat

and when it's digested,

more of the alpha-gal is introduced into your bloodstream -

this time, in much larger amounts.

So the body reacts accordingly.

It produces vast quantities of the antibodies

and...

..it swamps your bloodstream.

And it's this which causes the massive allergic reaction.

And the allergy is spreading.

Cases have been reported all over the eastern and southeastern USA

and across the world,

there are reports of other tick-induced meat allergies.

The ticks are on the march.

But what does the future hold for those affected?

Well, studies suggest that alpha-gal allergy recedes over time,

as the antibody levels fall.

So after a while,

those with the condition can eventually eat meat again.

As for Fred, he's still waiting for the all clear.

And whilst he waits,

he dreams of a return to some meaty morsels.

Well, I'm looking forward to coming home

and my wife saying she prepared my favourite meal.

Having a nice steak on the grill. Having meatloaf and mashed potatoes,

corn on the cob, a couple cheeseburgers.

Any of the above, I would be thrilled with getting

the OK from my doctor to sit down and have.

So there we have it.

It's almost unbelievable

to think that a tiny tick

can make a confirmed carnivore allergic to meat.

It does prove you don't have to be big

to have a big impact.

And now, from one tiny terror in the USA

to one other animal that punches above its weight

on the grasslands of the UK.

It involves this small, feisty animal -

the stoat.

The stoat is one of the UK's most secretive and elusive animals.

But in some places,

they're being spotted acting very strangely indeed.

-There it is, there it is.

-So fast!

Adam Lee managed to film one of these peculiar incidents.

I was out on a walk with my son,

when I suddenly noticed a flash of white -

the white underbelly of a stoat.

It was doing lots and lots of different moves

and lots and lots of rolls.

I got my camera out as quickly as possible and videoed it,

but we had no plausible explanation

as to why the stoat would display this kind of mad behaviour

in the middle of nowhere, in the middle of the day.

Other footage shows similar behaviour -

out in the open, oblivious to danger,

stoats manically leaping and dancing,

even attacking vegetation.

It's almost as if they've gone completely mad.

So why are Britain's stoats acting so bizarrely?

Well, maybe there's a clue closer to home.

Anyone who's owned a cat or a dog

knows how crazy they go when they've got fleas.

This behaviour looks similar and in fact,

stoats are infested by something much worse than fleas.

This is the skull of a stoat

and if you look closely,

you can see that it's pitted with tiny holes.

The culprit is this -

a parasitic worm, just 20mm long,

that lives in the stoat's nasal cavity.

Now, a heavy infestation causes this characteristic pitting...

but can it also be blamed for stoats throwing shapes on the lawn?

Well, weasels, polecats and other members of the same family

also get infected with this parasite.

But they have never been seen dancing like this.

So if they're not being driven crackers by a head full of worms,

could they be behaving like this on purpose?

Despite their small size,

stoats are efficient and deadly hunters...

..and they'll kill anything they can get their paws on,

but rabbits are top of their wish list.

With adult rabbits weighing at least

three times as much as these little predators,

it's clear that they need another weapon in their hunting arsenal

to guarantee success.

And some people think that the stoat's dance is exactly that -

not madness, but a carefully devised hunting strategy.

The theory is that this dance is a form of hypnosis -

the crazed moves send a rabbit into a trance,

freezing on the spot,

making it easier to catch.

And as far-fetched as it seems,

other predators also appear to use hypnosis to catch their prey.

Cuttlefish send ripples of colour across their skin

as they draw close to their prey,

which scientists think might distract it

in the last few seconds before a strike.

But there is a problem with this theory.

Rabbits do freeze when they see a stoat, or any predator.

But a stoat's killing reaction

is actually triggered by a moving rabbit.

So making them stop simply wouldn't make sense.

And that's not the only reason

that we can cross hypnosis off the list of explanations.

In most of the footage,

the stoats don't seem to be performing to an audience at all.

Well, there weren't any other rabbits in the vicinity,

that we could see that day -

in fact, there weren't any other animals.

So with the stoats dancing like no-one's watching,

the evidence suggests that they're making these mad moves

purely for their own amusement.

But no - everything in the natural world happens for a reason.

What you're really seeing here isn't play -

it's one half of a fight to the death.

Just like a kung fu master practising his moves,

the stoat is honing his attack skills,

ready for the next hunt.

After all, it could be a matter of survival.

And of course, moments like this, captured on video,

give us a unique opportunity

to enjoy the stoat's delightful yet deadly dancing.

And it's not just stoats that are doing things differently.

Next up is a creature whose behaviour is so unexpected,

it's verging on the suicidal.

Now, I think that tarantulas like this are really rather beautiful,

but of course, for many people, they're the stuff of nightmares.

Nevertheless, we have to admit that they are

one of nature's most respected and feared killers

and their technique is simple.

They remain stock still, just like this,

camouflaging themselves to avoid the attention of any predators

and so they can ambush their prey,

which they then envenomate,

using these massive fangs,

or chelicerae, here.

And you can see hers are quite literally

dripping with venom.

And that venom really does pack a punch.

It easily overcomes any invertebrates

and it's powerful enough to kill lizards,

mice and even small birds.

So we head to Texas,

for an alarming encounter with these arachnids.

In 2010, when a man filmed a wasp and a tarantula in his yard,

the outcome seemed a forgone conclusion.

Uh-oh, we might have a little war here.

-Oh, that's crazy.

-Yeah.

That's the first time I've actually even seen this.

But incredibly, this wasn't a one-off event.

Others were seeing the same thing happen elsewhere.

-That's amazing, he's...

-Oh, sweet!

-You're getting this, right?

-Oh, yeah.

-No way...

-Yeah.

-Sweet.

-That is amazing.

-You're kidding me?

So what is this massive flying insect

and why is it taking on a tarantula?

It's a clash of the titans.

One of the largest spiders in the world

against one of the biggest wasps.

In the midst of this frenzy,

it's hard to tell who's the victim

and who's the attacker.

But surely, the sheer size

and powerful venom of the tarantula

will give it the upper hand?

Well, actually, no -

because this is not any wasp.

This is the tarantula hawk wasp

and it has one of the most painful stings of any insect in the world.

Biologist Dr Justin Schmidt

has felt the sharp end of a tarantula hawk wasp for himself.

It just sends this electric shock just totally through your body,

just paralyses you, you sit there and scream.

You're just...just overwhelmed with pain.

With such a powerful venom,

the wasp is more than a match for the tarantula.

But why would a flying insect

risk putting itself in harm's way in the first place?

Well, a closer look

reveals that this isn't self-defence by the wasp -

it's naked aggression.

This wasp is looking for trouble.

But why?

Well, often, when small animals spot predators,

such as birds of prey or foxes,

they mob and harass them until they move away.

So perhaps the wasp's nest or its young are nearby

and it's desperately trying to keep the tarantula away?

But then, the wasp isn't chasing off the spider.

In a sinister twist,

the predatory spider has become the prey.

The spider appears to be lifeless,

but in fact, it's just paralysed.

The wasp is keeping it alive

and storing the body.

And she's not feeding herself, either.

Tarantula hawk wasps are actually largely vegetarian.

So if the wasp isn't going to eat the spider,

why risk injury or worse

to tackle a tarantula and then bury it alive?

Well, she's tracking them down for her offspring.

It's kind of curious - they're good moms.

You know, rather than eating the dinner, you keep it for your young.

Her babies eat tarantulas.

That's right - young hawk wasps eat tarantulas.

She doesn't kill it, she just paralyses it and puts it in a cell,

where she makes a little burrow, lays an egg on it,

seals it up and goes away - mother's job is done.

She doesn't eat any of the tarantula.

It's her baby that eats it.

One baby to one tarantula, which explains why they're so big.

The tarantula isn't a meal for mum,

it's a living larder for her larvae.

And over the next 10-14 days,

they eat it alive.

They choose the non-essential organs first,

so they eat the blood, the muscles, the fat, the reproductive organs.

Only then do they turn to the heart and the brain.

And after pupating,

they finally emerge as an adult.

It's a pretty gruesome process for the tarantula,

but of course, the wasp isn't being sadistic -

she's a caring mother,

making sure that her young have fresh food.

And the wasp's supermum skills don't stop there -

she can actually choose which offspring to lay in each spider.

And so she does that by...

A boy is unfertilised eggs.

And if it gets fertilised, it becomes a female,

so what she does is get a nice, big, juicy tarantula.

Wow. We want to make a girl out of this,

because she's got to be strong and tough,

to overcome her tarantulas when she's an adult.

While if it's a small tarantula,

then she'll lay an egg that becomes a male.

Because a male, all he has to do is fly around and find females.

He doesn't have to fight with tarantulas - he can be a little runt.

By matching the gender of her larvae to each tarantula that she tackles,

the wasp makes the most of every spider she finds.

This is one mother that you wouldn't mess with.

She's not only caring,

but clever, strategic and brave,

putting her own life at risk

to place her young inside a deadly predator.

So whether it's ticks turning carnivores vegetarian,

stoats rehearsing for a hunt

or wasps turning the tables...

..what these encounters show

is that although natural behaviours may seem strange at first,

there's always a method in the madness.

Our final set of weird happenings

sees nature taking over our lives.

From an unstoppable tide of green slime in China...

..to a deserted shopping mall with some unusual tenants.

Oh, this is cool.

But first, we head to Australia,

where something big has emerged from the forest.

The north eastern coast of Queensland.

People come here for the relaxing lifestyle

and a chance to live amongst the beautiful beaches

and pristine rainforest.

But lately,

local gardens have become the scene of some very alarming encounters.

It is the 16th of June 2012,

it's just me and Jonah here.

Oh, my goodness.

No, you do not go out there.

Even a simple car journey

is more like living in a scene from Jurassic Park.

SQUAWK

Wait, let him come, let him come.

SHE WHIMPERS

It's big, it looks threatening

and up close,

it's even more startling.

So what are these velociraptor-like visitors?

And why are they turning up in town?

Well, the creature is in fact a southern cassowary -

a usually shy, rarely seen bird

that roams these ancient rainforests.

It's as tall as a man

and along with emus and ostriches,

it's the closest thing that we have to a living dinosaur.

It's flamboyant coloured face and wattles

act like a beacon in the forest gloom.

It's a gloriously bizarre bird.

But one rather frightening feature

makes them stand out.

This is an old skeleton of a cassowary.

It's a bit battered, but it does give us the opportunity

to take a closer look at that part of its anatomy

that gives the bird its fearsome reputation -

its foot.

You can see it's got these three toes here,

for gripping the rainforest floor as it's running along.

But it's this interior toe here

that makes it potentially so dangerous.

You see, that claw can grow to 12cm in length.

So a good kick from a cassowary

could quite literally unzip a human.

I'm not sure I'd want to play chicken or kung fu with a cassowary.

Its kick has even been known to kill -

and that ranks them as the most dangerous bird on earth.

But what would provoke an attack?

Cassowaries are fiercely territorial

and defend their patch of forest from other birds.

They're also caring parents

and if they need to, they'll protect their chicks

by striking out with their fighting feet.

So no wonder people are a bit concerned

when they find a bird armed with a flick knife

next to their barbie.

I'm standing in my house and there's a cassowary in my yard.

Ooh, that's a bit freaky.

Don't...don't go out there.

But it's very curious.

-Wow, isn't that amazing, Jonah?

-Yeah.

Extremely...

Evidence like this suggests that these garden invaders

are staking a new claim on suburbia.

But there might be a clue to their takeover

in a devastating event that happened in 2006.

Cyclone Larry lashed the coast with devastating effect,

wrecking property and destroying huge swaths of forest.

In the coastal community of Mission Beach,

suddenly cassowaries were everywhere.

You see, the cassowaries had lost their forest homes -

and with them, they'd lost their food source.

Now, cassowaries eat fruit -

and a lot of it, up to 5kg a day.

And fruit is something that gardens in Mission Beach have in abundance.

It's eating the Davidson plums.

Hello there.

With the cassowaries' reputation for confrontation

and their new-found love of grow-your-own,

there could be trouble ahead.

But does this bird really merit its bad name?

The truth is, that left alone and treated with respect,

cassowaries are actually quite shy

and not the angry birds we might think.

But one thing can make them bold

and even aggressive.

Because studies have shown

that feeding cassowaries changes their natural behaviour.

SQUAWK

This can make them habituated to people

and associate us with food.

And on top of this,

the coastal towns of Queensland are ever expanding,

fragmenting the cassowaries' natural habitat

and bringing birds and people closer together.

The consequences are potentially deadly.

CAR HORN

Luckily, some people have taken this oddball bird to their hearts.

There are now plans to protect the cassowary.

So, with luck,

there may still be some life in the old bird yet.

From terror in suburban Australia,

we move on to an invader in the depths of a city.

Bangkok - the bustling capital of Thailand,

home to eight million people

and a well-worn travel destination.

In 2011, over 12 million tourists and backpackers

passed through the city.

And in the ever-popular Khaosan Road area,

a rumour began to spread of a new, must-see wildlife attraction.

But this was far away from Thailand's stunning seas

and fauna-rich forests.

This was right here,

in the heart of the city.

Oh, this is cool.

Jesse Rockwell was a student living in Bangkok at the time

and he overheard some locals

discussing a derelict shopping mall.

They were a bit mysterious about it -

they didn't want to tell us exactly where it was.

But it sounded quite interesting.

Our level of Thai at that time wasn't outstanding,

so we just heard "building" and "fish".

We were thinking aquarium -

we weren't sure exactly what they were talking about.

But this was enough to pique the interest of Jesse and his friends.

We decided to go hunting for it one day

and we had about a square mile radius to work from,

that we were pretty sure it was located in.

And we spent the day walking in circles,

in and out of small alleys

and we finally came upon a big iron gate that said,

"strictly no admittance" in big Thai letters.

There was actually a policeman on his motorcycle parked outside,

so we decided to wait about 30 minutes, until he puttered off

and we opened the door

and we were just amazed at what we found.

Jesse, and many other tourists following in his footsteps,

found thousands and thousands of fish,

thriving in the ruins of this burned out shopping centre.

Over a course of minutes, there were just more and more building up

and they got more and more active

and there was easily 5,000-6,000 fish, though.

We decided to go outside and buy some food -

some bread and some vegetables to feed them.

Once we started throwing food in,

it was just amazing how many fish there were.

Thousands just came right up to us.

There were more fish than actual water.

So how did this urban lake form

in the centre of a city in the first place?

And how did all of these fish get into it?

Well, the city of Bangkok was built on marshland

and many of the buildings are slowly sinking.

In some areas, the water table has risen so high

that monsoon rains simply don't drain away.

Roofless after a fire, the rain gradually accumulated,

leaving this vast pond in the basement.

But that still doesn't explain the presence of so many fish.

Well, fish have been known to colonise new ponds very quickly -

often birds introduce fish eggs on their feet,

or drop their dinner by mistake.

But in fact, there are few water birds in the centre of Bangkok

and those that do exist

are unlikely to enter a dilapidated shopping centre.

So what happened to bring the fish in here?

The water... It had been flooded for a number of years.

So people were having quite a few problems with mosquitoes.

In the general area, there's a lot of food vendors

and outdoor vendors in the old town.

And they were being really bothered by the mosquitoes,

so it's been said that somebody started to introduce the fish

to control the mosquito population.

So that could explain how a few of these fish got here,

but how are they thriving in such huge numbers in this murky water?

The fish are mostly tilapia, carp and catfish

and all of them will eat mosquito larvae.

These species are all hardy and adaptable

and they can survive in water which has very little oxygen.

Catfish, for example,

can even switch to breathing air if necessary,

taking gulps at the surface

and absorbing oxygen through their mouth.

And as well as fewer mosquitoes,

there's a second benefit for the local residents.

It's pretty obvious - a new source of food,

right on their doorstep.

Catfish is probably the most popular eating fish in Thailand.

I'm pretty convinced people were going in there

and you know, getting dinner,

because people fish in much dirtier water in Bangkok.

And that's probably the easiest place to fish in the world,

if I've ever seen it, you know?

Despite appearances,

these waters support a unique ecosystem -

proving that life will take hold, even in the most unlikely places,

if you give it half a chance.

In the midst of a teeming metropolis,

this unpromising building

provides an oasis of tranquillity.

Staying in Asia,

we move from an unexpected oasis

to the biggest party on Earth.

May 2008.

For 12 years, China had been preparing to host

the largest sporting event the world had ever seen.

Yes, the Olympics were rolling into town.

And of course, the organisers had spent billions on the event.

But there was one thing that no-one had planned for.

On the coast,

a headline-hitting invasion was under way.

It's a state of the art water sports facility -

everything you'd expect from a modern Olympic games -

except for one big, green problem.

Just six weeks before the start of the sailing events,

a thick green blanket engulfed

as much as 13,000 square kilometres of the Yellow Sea coast...

..solidifying the water.

What was this choking green blanket?

And where on Earth had it come from?

The culprit is an alga.

We know many of them more commonly as seaweeds.

And they're at the heart of many marine ecosystems.

In favourable conditions,

algal seaweeds like giant kelp

reach incredible sizes,

providing a home for hundreds of species.

So what got so out of hand in China?

Well, a valuable pillar of the ocean community

had become a relentless coastal invader.

But this wasn't an attempt to colonise the land,

or some sort of weird mutation.

It was actually a natural phenomenon -

blooming.

Professor Tim Nelson is an algal bloom expert.

Algae bloom usually

when there's the right combination of ideal conditions -

so plenty of light,

plenty of nutrients - nitrogen, phosphorus, iron -

those kinds of things

and ideally the perfect temperature,

which is just a bit warmer than the average temperature for the year.

But this was the biggest algal bloom

the world had ever seen.

So what was going on in the Yellow Sea

to trigger this astonishing event?

China, the world's fastest-growing economy,

had seen a huge surge in farming and industry.

Industrial pollution and raw sewage

were flowing into the sea at record levels.

The water was quite simply supercharged with nutrients.

At any other time of year, that might not have mattered -

but the Olympics took place at the height of summer.

In China, you've got the ideal conditions,

the perfect storm for algae growth and accumulation.

Into this perfect storm

drifted a free-floating seaweed -

the aptly named Ulva prolifera.

A patch the size of a football field

could cover a county - a large county in England,

a small state in the United States within a couple of months

and within four months,

could theoretically cover the world.

Spurred on by a bonanza of nutrients, warmth and sunlight,

an immense bloom grew rapidly out at sea.

Scientists and officials were keen to find out

where this super bloom had originated.

The answer came from space.

The bloom was so massive,

it showed up on satellite images.

Researchers tracked it back to its source,

about 240km south,

just off the coast of Jiangsu province.

Satellite images also revealed

vast new seaweed farms nearby,

stretching 13km out into to the sea.

A coincidence?

These seaweed farms are growing this -

it's called nori

and it's a type of seaweed that's used in the manufacture of sushi.

And given the increased global demand for this sushi,

the farms have sprung up to cater for that.

But Ulva prolifera also grows there -

as a pest.

So in springtime, the farmers go out and scrape it off of the rafts.

It then drifts into the open ocean,

where it meets conditions that are absolutely ideal

for a bloom of Olympic proportions.

The amazing scenes of 2008 were just the beginning.

Huge green tides have washed ashore at Qingdao

every summer since.

As for the Olympics,

the Chinese government drafted in 10,000 people

to clear the beach by hand,

removing an estimated million tonnes of algae.

The Games were saved.

And there we have it.

From giant birds in your garden,

fish swarming in a shopping mall

or green slime taking over the Olympics,

the resilience of life to survive and thrive in such weird ways

is truly something to behold.

What all of these amazing events tell us

is that nature always has the capacity to surprise us.

And whether it's bonkers behaviour

or simply animals in the wrong place at the wrong time,

the persistence of life impresses us too.

But sometimes, when our paths collide,

our reaction is confusion, shock -

even to be a little scared.

Only by looking closer

can we fully comprehend

who and what we share our planet with.

Next time on Nature's Weirdest Events...

Fish out of water...

That knocked my hat off!

..slugs get into a tangle...

What is happening? Augh!

It's so disturbing...

..and yes, stampeding rabbits!

HE LAUGHS

That tickles!