Original subtitles

Narrator: Ever wondered why an apex predator

Would let this guy escape?

So this is very bizarre behavior.

Narrator: What could cause this ominous, dark mass?

So, it looks as though there's this apocalyptic cloud.

Narrator: And why scorpions can light up

Like a las vegas nightclub?

So this is just a mad scene.

♪

Narrator: Nature is awe-inspiring.

But sometimes it just doesn't make sense.

Man: I have never seen anything like this.

Narrator: Our team of experts investigate the weirdest animal behavior...

That's amazing.

...And the most unexpected events...

What is causing that?

...Ever caught on camera.

Woman: My god!

These are...

-- Captions by vitac -- www.Vitac.Com

Captions paid for by discovery communications

Narrator: Londolozi, south africa.

A safari guide captures a dramatic scene.

A civet -- a small, cat-like mammal --

Cowers in the middle of a puddle.

Why is it so scared?

Because it's being eyeballed by an enormous leopard.

♪

It's a case of "wrong time, wrong place"

For this normally nocturnal critter.

The question is, what will it do?

♪

So, it's a really tense bit of footage.

Narrator: The leopard slowly circles the water.

But then...

[ whimsical music plays ]

...Flops down to sleep.

So, why hasn't she launched an attack?

♪

Narrator: Is she the laziest leopard in the world?

Lunch is right there.

There's no chance that that leopard can't see the civet.

The civet's stopped moving, therefore is invisible.

We're not talking about "jurassic park" dinosaurs here.

Schreiber: These are nocturnal hunters.

They have incredible eyesight, they have incredible smell.

There is no way that she has just walked past the puddle

And not noticed a living civet inside of it.

[ beeps ]

Narrator: So, what's going on?

♪

Maybe this leopard does not like hunting in water.

Burke: This leopard looks really reluctant to get its paws wet,

And, of course, cats are quite famous

For not really liking the water.

Narrator: But that's domestic cats.

[ shrieks ] big cats,

Like this jaguar, are a bit different.

I've seen jaguar hunting in the water.

I've seen jaguar hunting caiman, which is a kind of,

You know, crocodile, basically.

♪

Tigers are famous for it as well.

You know, they'll quite happily swim and wallow.

♪

Narrator: And certain leopards actively hunt fish for dinner.

In botswana, there's a population

In an area called savuti where the leopards

Have really specialized in hunting in the water.

They actually hunt catfish.

Narrator: So a puddle this size wouldn't stop a leopard.

I think if it wanted that civet, it would have it.

I think there's other things at play here.

Narrator: Could there be a clue in the civet's stance?

He's standing hair on end to look as big as possible.

♪

[ beeps ]

Has acting tough saved him?

♪

When a predator's coming after you,

Feistiness can be a secret weapon --

Like these river otters that successfully ganged up

To see off a lurking crocodile.

But the crocodile was outnumbered.

So is there more going on here

Than just a civet standing up for itself?

[ beeps ]

Could it be that the civet just isn't that appetizing?

Civets are know for one thing in particular --

Civets are famously smelly animals.

They have massive anal glands,

And they produce this sort of oily, musky secretion,

Which is not particularly nice.

So you've got to be pretty hungry,

I'd imagine, to be a leopard to bother with a civet.

They've probably encountered a civet in the past,

And you don't really want your dinner

Scratching your face as you're eating it.

Narrator: Is this civet just not worth the effort?

As the footage unfolds,

Another leopard enters the picture.

♪

This male comes on the scene.

We start to realize that maybe she's distracted

By something else.

Narrator: Are they more interested in each other

Than in food?

Now, leopards are solitary animals.

They don't spend a lot of time together.

Narrator: Even when hunting, they go it alone.

♪

But when it's time for business,

A pair will stick together for days

And mate up to 100 times in 24 hours.

[ laughs ]

♪

Burke: So as this male joins the female,

They clearly have something else on their mind.

Narrator: Something else, but not necessarily mating.

♪

Burke: There's a lot of tension. They have a little scuffle.

[ grunting ]

Narrator: And they bolt straight up the marula tree.

[ growling continues ]

Another clue, right there in the footage,

Reveals what they're fighting over

And why they've ignored the civet.

This video clip turns from a curious bit of behavior,

Or a curious lack of behavior,

To when the second leopard turns up.

And then as it climbs up that marula tree in the background...

[ growling ]

...At the top of it is probably a key part

Of this whole story.

Narrator: The civet would just be a starter anyway.

It seems the leopards have already stashed

Their main course up in the tree.

Baker: The remains of a kudu carcass -- this is a massive antelope.

So this leopard isn't short of food.

So why eat a civet when you got a belly fully of prime venison?

Burke: So that's the reason why the civet isn't really

That interesting to these leopards --

Because they already have something to eat.

Narrator: Keeping a treetop pantry

Is standard practice for leopards.

Baker: Why bother drag a kudu carcass to the top of a tree

Is that this is africa.

It's full of other animals that will steal your carcass.

Hyenas in particular will easily steal from a leopard,

So they just want to get that up

And out of the way of animals that can't climb.

♪

[ birds and insects chirping ]

♪

Narrator: Phoenix, arizona, summer 2018.

As night falls, a pest-control team

Are sweeping homes and gardens.

They've been called in by worried homeowners

To look for venomous scorpions.

You know, the most we've ever caught in a home is about 280.

Our average is 12 per sweep.

Gaffin: How dangerous are scorpions?

Well, the scorpions from south arizona,

The arizona bark scorpion, are pretty dangerous.

Globally, I think it's about

1.2 million stings per year from scorpions.

Narrator: Why hunt them at night?

Well, during the day they're camouflaged and hard to spot.

But at night under black light, also known as u.V.,

They give themselves away.

They glow. Holland: Here we go.

These are arizona bark scorpions,

Which are the most venomous here in the united states.

♪

They have little hooks on the bottom of their feet

That will grip onto texture,

Much like velcro hooks into the loops,

Which is how they get on people's walls

And in people's houses.

You can see that they glow rather well

Under this ultraviolet light.

♪

Daly: There are over 2,000 known species of scorpions,

Almost all of which are thought to glow under u.V. Light.

♪

Greive: One of the great, vexing questions for entomologists

Is, "why do scorpions glow under ultraviolet light?"

Narrator: It's puzzled scientists for decades.

To try and figure out why, first we need to understand how.

Scorpions have this wicked trick

Where they take light in at one wavelength,

And then put it out at a different wavelength.

It's called fluorescence.

Gaffin: In their outer layer of their skin,

There's a couple of chemicals,

And when ultraviolet light stimulates these molecules,

They emit the fluorescence that we see.

If you want to see fluorescence in a scorpion,

It has to be ultraviolet light.

Greive: The key to a scorpion's ability to glow under ultraviolet light

Is contained in this very hard coating over the entire animal.

The actual chemical that enables scorpions to glow,

It's called carboline,

And this has been true for millions and millions of years.

Scorpions have been around for a very long time.

In fact, there are fossil scorpions

That are, like, this big.

Narrator: The carboline in scorpion skin

Is a u.V.-Absorbing chemical.

In other animals, similar chemicals act as sunscreen.

[ insects chirping ]

[ beeps ]

Could the same be true for scorpions?

♪

Now, this would make sense,

Because way back in evolutionary history

Scorpions may well have been active during the day.

Narrator: So it's possible that the carboline

That made scorpion ancestors glow

Also acted as prehistoric sunscreen.

Greive: So could it be performing

That same function for scorpions today?

Narrator: Maybe, apart from one little hitch.

[ insects chirping ]

[ insects chirping ]

Narrator: In phoenix, arizona, and, in fact, across the world,

Scorpions give up their hiding places

By glowing under u.V. Light.

The chemical that made ancient scorpion ancestors glow

Probably acted as a form of sunscreen.

Is that why scorpions glow today?

Sounds plausible, apart from one small detail.

Today's animals are much smaller

And are almost exclusively nocturnal.

[ insects chirping ]

Narrator: Scorpions are most active just after sunset,

So have no need for sunblock.

Burke: And it wouldn't make sense for them

To keep producing a chemical in their exoskeleton

That is no longer needed.

It just wouldn't make any anagenetic sense,

So I don't think that's the answer.

Narrator: If the chemical is not acting as sunblock,

What is it for?

[ beeps ]

Could it be the scorpions glow

To send each other messages instead?

Are scorpions using this glowing ability

To communicate with other scorpions,

Either to define territories or to repel rivals?

Daly: This isn't completely unlikely.

Fluorescence has been used to communicate

In other species, too.

A study was done on the skulls of chameleons

Where they have these florescent patterns,

Which can help other chameleons

Identify one another in a dark environment.

Narrator: It's not out of the question that a scorpion's glow

Could be for communication, just like the chameleon's.

♪

So what about glowing as a lonely hearts ad?

I wouldn't rule this one out.

I think there is a chance that perhaps males

Might be detecting females from a distance.

♪

Narrator: A faintly glowing female could be like a beacon

To a male scorpion.

That's a "maybe" then to passionate scorpions

Glowing for love.

Professor douglas gaffin has been studying scorpions

For 25 years.

He thinks their glow could be multipurpose,

But that it's most likely for keeping them save.

Perhaps they are using the light as detected through their body

To seek out places to hide for protection.

[ beeps ]

Narrator: Hang on. For protection?

These are scorpions we're talking about --

Fierce, tail-bending stinger demons.

They've got some amazing seismic detectors

On each of the eight legs.

♪

They actually detect vibrations of the crickets as they walk by.

Riskin: They've got pincers,

But those are just sort of for keeping you at bay.

The real business end is at the back.

♪

If the scorpion feels threatened,

It can bring its tail down

And whack you and inject venom very quickly.

♪

Narrator: You have to be brave to face down a scorpion.

But some animals, like this bat-eared fox,

Will take on the challenge.

You see, scorpions are quite exposed

When they're out there on the sand.

There are predators of scorpions.

♪

Narrator: Scorpions are packed to the rafters with fancy features,

But they have an achilles' heel.

Scorpions don't have very good eyesight at all,

So when they're running to hide, they need another mechanism

To help them know whether they're hiding effectively.

Narrator: Could their incredible glow be a tool to help them stay alive?

♪

[ insects chirping ]

[ insects chirping ]

♪

Narrator: In phoenix, arizona,

We're unraveling the secrets

Of why scorpions glow under ultraviolet light.

Could it be for protection?

Scorpion vision is mostly tuned to daytime colors -- green,

Which is fine when the sun is up,

But at night, they need another way to detect

Whether they're hidden properly.

♪

This is where we run our experiments

To learn more about scorpions' reaction to light.

Narrator: A team of scorpion scientists at the university of oklahoma

Decided to find out how they manage it.

Taylor: We'll take it out, and we put them in these little arenas.

Narrator: These arenas will be floodlit

Under the lights of a scorpion disco.

And within these cylinders, we have small lights --

Either green lights or u.V. Lights.

We put this on top.

Within the box, we have a small infrared camera

That videotapes them from below.

Gaffin: So in our early experiments, we found

That scorpions appear to be sort of agitated

Under both green and u.V. Light.

They kind of run in little spurts.

♪

Narrator: Shining both these lights on a scorpion makes it run,

Because it senses the light

And that it's exposed and therefore vulnerable.

We decided to look to see if the eyes were responsible

Or if different parts of the body

Were responsible for this behavior.

So we made these little tiny goggles out of foil

To cover their eyes.

♪

Narrator: The experiment found that with tiny goggles

Blocking their eyes,

The scorpions didn't feel the need to run for cover

Under green light.

They couldn't see it,

So didn't sense that they were out in the open.

But they still ran when ultraviolet light

Was shone on them.

Gaffin: When we cover the eyes,

We still see some behavior under ultraviolet light.

So we had fairly clear difference in behavior,

Suggesting that perhaps there was some sort of detection

Of light beyond the eyes themselves.

Narrator: So it seems that even when blindfolded,

Somehow they were able to still see the u.V.

With other parts of their body.

We don't know exactly how they know they're glowing,

But it's possible that signals from

The u.V. Light-induced glow

Could pass through nerves to their brain

To tell them light is falling on them.

The extraordinary conclusion from doug gaffin's work

Is in effect,

A scorpion is omnispective, all-seeing.

♪

Burke: Having this way of sensing u.V. Light

Across the whole body

Is a really clever way of making sure

That when they're hiding, all of them is actually concealed

And they haven't left any part of their body out and exposed.

Narrator: Why is sensing u.V. In particular important?

Because just after sunset when a scorpion is most active,

The proportion of u.V. Light is at its highest.

So if a scorpion were to scurry when startled

And just any part of its body

Were under a little twig or a leaf,

It could reflexly move towards the shade

And maybe have a measure of protection.

Narrator: It looks like scorpions' attention-grabbing

Fancy fluorescence is actually to help them hide,

And maybe to help them see each other, too.

[ insects chirping ]

♪

Narrator: April 2014.

In northern iceland, a couple on a boat trip

Film a dense cloud hanging over the surface of a lake.

There's this apocalyptic cloud

Rolling across this lake in iceland.

This really thick, dense, dark cloud

Hanging very, very low over the water.

Narrator: What is causing it?

[ volcanic rumbling ]

Iceland is known as the "land of fire and ice."

It's notorious for its ice, but when it comes to its fire,

That's referring to its volcanic activity.

[ volcanic rumbling ]

A thought was, "well, could this be a cloud

From a nearby volcano, an ash cloud or something?"

Narrator: With over 30 active volcano systems,

Iceland has history

With belching out apocalyptic ash clouds.

But no volcanic activity had been recorded at that time.

♪

It became obvious this was not smoke at all.

Narrator: Because this ominous cloud is alive.

♪

[ insects chirping ]

[ insects chirping ]

♪

Narrator: In iceland, an apocalyptic lake cloud

Hangs in clear, blue sky.

At first, it looked like volcanic ash or smoke

Billowing across the surface.

Only when you get a much closer look

At actually what's going on,

You start to see individual organisms.

[ fluttering ]

♪

Of course, they are midges --

Thousands and thousands of midges.

Narrator: Midges are tiny two-winged flies.

And there aren't just thousands -- there are millions.

When a million midges crash your boat trip,

You have to get creative with headgear.

[ fluttering ]

Midges sure know how to wreck a boat trip.

But why do they swarm like this? [ buzzing ]

[ beeps ]

♪

Daly: Midges all hatch at the same time.

That's what creates these huge clouds,

And when they do form these huge clouds,

It's really all about mating.

Narrator: Midges hang out by lakes

Because they need the water.

They lay their eggs in it,

And spend the first part of their life

Living as larvae under the surface.

Burke: Many species have this kind of life cycle.

They might spend years as their larval stage underwater

And only a few days or sometimes even a few hours as adults,

And it's that brief little window

Where they have an opportunity to mate.

Narrator: Adult flying midges have no mouth parts and don't eat,

So they have just a few days to do the deed

And lay their eggs before they die

So the cycle can begin again.

And in lake myvatn,

Which means "midge lake" in icelandic,

Huge clouds of mating midges

Will appear every few weeks during the summer months.

Make sure you have a bucket handy.

[ camera shutter clicks ]

[ insects chirping ]