Original subtitles

Narrator: Ever wonder why crows would gather

Around the body of a fallen comrade?

Man: This must have been one popular crow.

Narrator: What's electrifying the skies over venezuela?

This is the lightning strike capital of planet earth.

Narrator: And what could cause a lake shore

To become smothered in spider webs?

Layers of webs pretty much covering everything.

Narrator: Nature is awe-inspiring,

But sometimes it just doesn't make sense.

Man: I have never, ever seen anything like this.

Strange animal behavior,

Unexpected events captured on camera --

The truth behind them is astonishing.

My god!

Nature's greatest mysteries, "solved."

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

Captions paid for by discovery communications

Narrator: February 14, 2018, seattle, washington --

A seemingly ordinary valentine's morning erupts into chaos.

A cacophony of squawks draws schoolteacher

Jean sherrard to the bizarre scene outside.

Narrator: A huge flock of crows has gathered.

They all seem to be looking at one individual.

The question is, "just what is going on in their bird brains

To make them do this?"

This is a really strange bit of behavior,

And all sorts of questions spring to mind

As to what's actually going on here.

Why have they gathered round this crow?

Perhaps these crows gather round to assess it

And see whether it's just injured

Or whether there'd be a way of that crow coming back around.

Narrator: So have these crows gathered to help out a wounded flock mate?

After all, the social dynamics of crow society

Show these birds of a feather really do flock together.

Crows mate for life.

And young crows might remain with their parents

For 5 or more years, some of them,

So that you get really large extended family groups.

Narrator: But there's no room for being a lazy teenager in a crow family.

Young crows and corvids

Will help their parents to raise siblings.

Marzluff: And those offspring will help feed the young,

Defend the territory, look out for predators.

Narrator: Other animals with strong social bonds like lions

Have been known to support their injured friends.

Is this happening here?

Certainly if a mate is injured in a nonlethal way,

They will still remain together.

They do seem to have a really strong loyalty.

Crows have been reported to feed an injured bird

If it couldn't feed itself.

There are even reports of individual crows

Helping support another bird who's wounded,

And I can see that definitely happening with a mated pair.

But it's really unlikely that they would do that

For unrelated crows.

Narrator: A group of crows is called a murder.

In seattle, this cackling army is at least 60 strong.

But crow families have no more than a dozen members,

So this gathering is unlikely to be a family affair.

So in this instance, all these crows

Gathering round to help a crow, it doesn't seem likely to me.

Narrator: There must be something else going on

To bring this flock together.

On closer inspection, it seems our crow is way beyond help.

It's dead.

For a really long time throughout human history,

We have noticed that crows seem to respond

Really strongly to their dead.

When a crow dies, a murder of crows will gather around

That dead crow in what's known as a crow funeral.

A bird will fly in, and it's...

You know, as it's going about its day,

And it will see a dead crow on the ground.

One starts to call,

Others come in, and they start calling.

It's a cacophony.

Narrator: But what's the motive for this crow funeral?

Could their interest in the dead crow

Be an attempt to come to terms with losing a flock member?

Marzluff: One other reason they could come in to a funeral

Setting would be to mourn the loss of that individual.

Swift: Maybe it was an expression of grief.

One of their neighbors died, or their mate died,

And they're coming to pay their respects.

Marzluff: They might actually be having emotional mourning

Sort of response to that.

Narrator: In the animal kingdom,

Only a handful of species like dolphins and elephants

Respond to their dead in this remarkably human way.

Could crows also be a species that grieves?

John marzluff is professor of wildlife science

At the university of washington and has been working with crows

For decades to better understand their behavior.

John wants to explore the mental reactions of wild crows

When a fellow crow dies.

After anesthetizing his subjects,

He examined their brains in his lab

Using a special bird-sized scanning machine.

The way we scan a crow's brain

Is to use what's called a micro-p.E.T.,

Or positron emission tomography.

Narrator: The p.E.T. Scan will allow john to see which parts of the crow's

Brain light up during a crow funeral.

Firstly, to simulate a crow's reaction to death,

He showed a crow a stuffed dead bird.

John wanted to measure their mental reactions

To the dead crow,

But the result wasn't quite what he'd expected.

I kind of expected them to be very stereotyped,

In a very simple, like, response,

But it wasn't like they were fearful

Or even emotional about this particular scene.

Instead, what we saw was that part of their brain

Was activated that is indicative of complex decision-making.

Narrator: So it seems that the crows at the funeral are flocking

Together not to pay their respects

But to assess the situation and make decisions,

In which case, "what answers are these brainy birds seeking?"

Maybe they're turning detective

And investigating the crime scene.

Perhaps it's a kind of a novel predator like a unique dog

Or a human that they need to learn about.

Narrator: To test the theory, john added a suspect to the crime scene,

A human holding the dead bird.

Swift: Well, they have made this connection

That this person holding a dead crow

Must have had something to do with their death,

Or in some way they're bad.

Narrator: Adding this new threat element

Activated a different part of the crow's brain.

We saw the hippocampus activated,

And the hippocampus is an important part of the brain

That is used to form important social and spatial memories.

That indicates that these birds are forming a memory.

Narrator: John's results suggested that wild birds will commit

These crime scenes to memory,

But just what exactly are these super smart birds

Trying to remember?

Narrator: February 14, 2018, seattle, washington --

A crow funeral is filmed on a suburban street.

What are they doing?

To find out,

Scientist john marzluff has been examining crows

To see how they react to their dead,

And he's discovered that

They seem to be trying to memorize the event.

Crows appear to be really good at learning from crime scenes,

And the two things that we know that they learn,

And there might be other things,

Is the location of the crime scene itself

And any suspects that were present

At the scene of the crime.

Narrator: So is our valentine's day crow funeral in seattle

Really just one big crow investigation.

If so, it could be beneficial for every bird in the flock.

By gathering around the dead or dying crow,

What the others are doing are gleaning information,

Learning and finding out what caused the accident,

What caused their death,

And once they've got that information,

It helps them avoid a similar end themselves.

So make sure that they don't meet the same fate

As this bird that has just recently died.

Marzluff: It pays to be smart and learn things as you go

Because you might be able to use that information in the future.

Narrator: So it's not so much a crow funeral.

It's more like a crow classroom where the birds learn

How to keep themselves safe down the line.

Oh, and by the way, no need to worry

About the welfare of the crows john used in his tests.

We wake the bird up, and then it can be released to the wild

And go about its own life.

♪

Narrator: October 2018, lake vistonida, greece --

Residents living on the lakeshores wake up

To a very strange sight.

Oh, no. Oh, no. Oh, no.

Narrator: Almost overnight, their beach has been transformed

Into an arachnophobe's nightmare.

This is a creepy one.

This place in greece all of a sudden

Is totally covered in spider webs.

Layers of webs covering plants,

Pretty much covering everything and over a huge area.

It looks like Halloween decorations, but it's not.

It's totally real.

Narrator: The super web spans almost 1,000 meters.

What could be going on in the spider world

To make them spin such a gigantic structure?

Could this be the work of a group

Of unusually social spiders?

Spiders certainly aren't known for their teamwork.

Everybody thinks of spiders as these solo hunters,

But there are a few kinds of spiders that act communally,

Almost like an anthill,

Where a whole bunch of spiders will share a great big web,

And that could be what's happening in greece.

Narrator: Of the almost 50,000 species of spider worldwide,

Only 23 species are truly social.

Cooperative spiders create immense webs,

Home to up to 50,000 individuals.

So do we have a fast-growing community

Of social spiders here in greece?

They are a species of orb weaver,

Which typically aren't social.

There aren't any communal spiders in greece

Or anywhere near greece.

That's not going to explain this.

Narrator: If there are no social spiders in greece,

Did these long-jawed orb weavers migrate here?

Spiders crawl slowly through their webs,

And they crawl on the ground.

Narrator: But surely they haven't swum across the lake?

What a lot of people don't realize is

That they can also fly.

Narrator: October 2018, lake vistonida, greece --

The shoreline looks like a Halloween party.

Spider webs are everywhere, so how did they get here?

Could an army of spiders have flown in overnight?

A spider's version of an airplane

Is just a really long strand of web

That gets caught by the wind,

And if the spider is holding on to its strand

And moves with it, it's called ballooning.

They will climb to the top of whatever

Is most prominent in their environment,

So a top of a tree, blade of grass.

They will stand on their tiptoes, raise their abdomen,

Let out silk, and then float away.

♪

So they travel huge distances without any wings,

Just using these silk lines.

Narrator: But only some spider species can balloon,

And it seems unlikely that so many ballooning spiders

Would happen to land in this one spot, as once airborne,

They have little control over where they go.

So could the greek lake have been their launch site?

Maybe all those long strands of web have accumulated

And made these big huge webs that cover everything.

Narrator: When thousands of spiders balloon,

The tangle of silk threads they leave behind

Can be surprisingly lovely to look at,

But why would a bunch of long-jawed orb weaver spiders

Be ballooning in such large numbers?

Well, baby spiders

Have an especially big motivation to move.

Sixty-five babies can hatch from just one egg sac.

And these are all in a very small space,

So there's a lot of competition and potentially predation

Happening from their brothers and sisters

As spiders are cannibalistic.

They will eat each other,

So obviously it's a good idea to disperse

And get far away from any brothers and sisters

That might want to eat them.

Narrator: No wonder young spiders will go to extreme lengths

To find a new home,

But was it a bunch of baby spiders

Ballooning off to pastures new that carpeted the lakeshore?

If they were ballooning, you would expect to find

Just individual strands everywhere,

And these are well-built webs.

Narrator: If they're not ballooning in,

Could the solution be something to do with weather?

This shoreline in greece had warm and humid conditions,

Which is perfect for an abundance of mosquitoes.

Narrator: Millions of mozzies cued a frenzy of feeding and mating.

So the reason there were so many spiders in greece all at once

Is because all of a sudden,

There was a ton of food for them.

With that much food available, the spiders went to town.

Narrator: This glut of food and ideal

Weather led to a breeding bonanza,

And an explosion in the local spider population.

And that's what resulted in this huge, huge

Extraordinary webbing that you saw there.

And so it turns into the new york city of spider webs.

Narrator: Perfect weather and lots of spider food

Means lots of spiders, and that means lots of webs.

Greek spider town mystery...

Solved.

Astronauts at the international space station

Capture a dramatic storm over south america.

One lake in venezuela is particularly electric,

Which begs the question, "why?"

Lightning is a very common occurrence around the globe.

There are around 100 lightning strikes per second.

That averages out to around 3 billion

Lightning strikes per year.

Narrator: 3 billion strikes -- that's a lot of electricity,

And some places are much more hit-prone than others.

Riskin: People love to say that lightning

Never strikes twice in the same place,

But they obviously haven't visited

Lake maracaibo in venezuela.

This place is out of control.

[ thunder rumbling ]

Narrator: With an average of 28 strikes a minute

On 300 nights every year,

This place holds the world record for lightning activity.

This is the lightning strike capital of planet earth.

Narrator: The question is, "what makes this place so electrifying?"

Narrator: What is causing lake maracaibo in venezuela

To be the lightning capital of planet earth?

One possibility is that humans have done something there

That has caused all this lightning to show up.

It sounds impossible, but people can totally influence

Where lightning strikes.

Lightning is always trying to find the quickest path

To the ground, the shortest route possible.

Narrator: And in big cities, that shortest route

Usually starts with the highest skyscraper.

Are man-made structures attracting lightning

To this lake?

It's very unlikely that there would be

Any kind of human element involved

In terms of a building, of a city.

Riskin: You don't have skyscrapers all around this lake.

It's just a few small buildings.

They're not empire state buildings,

So they're probably not big enough to focus the lightning,

And the lightning is not happening there.

It's happening out over the lake.

Narrator: This might be the most electrifying place on earth,

But it's teeming with life.

Jaguars roam the lush banks, and the lake,

Which is three times the size of rhode island,

Is home to freshwater dolphins and over 100 species of fish.

♪

So what could be causing this region's

Tremendous thunderstorms?

Perhaps something more industrial.

Midcap: One of the original theories

Was that it could possibly be driven by or fed by methane.

So the lightning storm is happening way off the ground,

Like 50,000 feet up, and the methane,

If it's coming out of the ground,

Would have to travel a long distance to get there.

Now, anybody who has ever farted knows

That it's going to dissipate pretty quickly,

And to be honest, it would look like a giant fireball,

Not a whole bunch of lightning strikes.

Lightning really doesn't depend on methane

In any way to feed itself or intensify strikes,

So methane has been ruled out.

Narrator: It's not buildings, and it's not gas from the oil industry.

Looks like humanity's off the hook.

Could something natural be responsible

For lighting up the skies above venezuela?

♪

So this is a very fascinating event in that

There are a number of things going on here.

First and foremost would be the geography of the region,

So lake maracaibo is surrounded on three sides.

It's hemmed in to the east, to the west,

And to the south by very high mountains.

To the north, lake maracaibo opens up to the caribbean sea.

So you get all this warm air that comes from the caribbean.

Midcap: It's warm air.

It's moist air, and it creeps into the lake maracaibo region.

That air has to go someplace,

But when it enters the lake itself, it realizes,

"okay, there are mountains here. There are mountains there.

There are mountains. Where am I going to go?

I can't go to the side. I have to go up."

And then you get this cold air down from the andes,

And it mixes and causes a thunderstorm,

But the thunderstorm can't leave.

It's stuck there and just gets amplified.

And this happens night after night after night after night.

Narrator: So the towering mountains are trapping powerful storms,

And with nowhere for them to go, every evening is explosive.

♪