Original subtitles

Narrator: How and why did ants build this bridge

With their own bodies?

Daly: The level of cooperation it takes to pull this off

Is mind-blowing.

Narrator: And, no joke, why did the fish cross the road?

Most fish would never do that.

Narrator: And what creature is behind a european crime wave?

These animals caused $330 million

Worth of damage to cars.

The big question is -- why?

Narrator: Nature is awe-inspiring.

But sometimes, it just doesn't make sense.

Man: I have never seen anything like this.

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.

Man #2: My god!

These are...

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

Captions paid for by discovery communications

Luxembourg, 2016 --

Residents of this small european country

Are waking up to a curious crime wave.

Thousands of motorists are finding their cars

Had been damaged and won't start.

However, the evidence is quite strange.

Not only are wires cut through completely,

But there is feces and a strong smell of urine everywhere.

It's not human vandals...

It's animals.

Very angry animals.

Narrator: It turns out that stone martens,

A relative of the american pine marten,

Have been engaging in an ongoing campaign to destroy cars.

What may at first seem like a minor act

Of wildlife vandalism is in fact a very big deal.

Cooke: Between 2010 and 2014,

Stone martens caused $330 million

Worth of damage to cars.

That's over a million insurance claims.

The big question is -- why?

Narrator: To find out, we need to know more about this furtive

And furry rascal.

So, what exactly is a stone marten?

Greive: It's basically a super weasel.

It's about the size and weight of a house cat,

But far slimmer and far more muscular,

And 10 times the mischief.

Narrator: In the last 40 years,

The stone marten population in europe has exploded.

Cooke: So, back in the 1950s,

Stone martens were almost extinct.

They'd been hunted for their fur.

But now, populations are bouncing back,

And they're actually spilling into urban situations.

And that's where we're starting to see this vandalism.

Narrator: However, closer proximity to people

Still doesn't explain why they're terrorizing cars.

And while the bad-boy behavior seems strange,

It's not the first time members of the animal kingdom

Have targeted motor vehicles.

Greive: There's a safari park in mersey side, in England,

Where baboons are famous for tearing off windshield wipers

Just to elicit a response from the drivers within.

Man: [ laughs ] dude.

Child: Look at the monkey!

No! Woman: Go on!

Oh, no!

Ah [bleep]

[ laughter ]

Greive: And in the mountains of new zealand,

There's a large alpine parrot called a kia

That, curious as they are,

Is famous for tearing off pieces of rubber,

Not just from the windshield wipers.

But also from window seals and sun roofs,

And even the tires themselves.

♪

Narrator: But what's driving the stone marten

To carry out this vehicular vandalism?

Greive: So, is this damage caused by young stone

Martens who are basically trying their new teeth out

On anything they can find?

Cooke: Are they just chewing things,

Trying to figure out how their teeth work

And what's good and what isn't?

Greive: A team of scientists are currently

Looking into what it is that stone

Martens are attracted to within vehicles.

Narrator: We paid one of those scientists a visit,

Britta habbe, in hankensbuettel, germany.

Habbe: Stone martens cause a lot of damage in germany.

Now we've got about 66 million euros of damage per year.

Narrator: Habbe works with captive stone

Martens to try to get to the bottom

Of why they are wreaking so much havoc.

We run different tests to find out how to prevent cars

From being damaged by stone martens.

We've put two animals in here.

They are called kate and william.

Stone martens show exploring behavior by gnawing on things.

They've got very sharp teeth, and that's why they can cause

A lot of damage on cables used in cars.

Narrator: So does habbe think teething toddler

Martens are to blame?

We found out that young

Martens don't show this kind of behavior.

At least, they have to be two years old.

The young ones don't do that.

Narrator: Juvenile nibblers are ruled out.

Could there be another reason the stone

Martens go into the vehicles?

Cooke: What if the martens are actually attracted to the cars

Because they think it's a food source?

Well, incredibly, some car cables actually

Have food substances in them.

So that could be attracting the stone martens.

Narrator: Surprisingly, soy- and plant-based sugars

Can be a major component of some car cables.

And though cars now contain up to about a mile of cable,

The stone marten isn't a picky eater

When it comes to which cables to chew.

He'll bite them all.

Studies have shown that there's no material

That makes these wires and cables more

Or less attractive to a stone marten.

Any other substance doesn't seem to make a difference.

So why are they chewing through these cables?

♪

Narrator: Dr. Jan herr, a zoologist in luxembourg,

Tracked wild stone martens over a two-year period,

And thinks the answer may lie

In their highly territorial behavior.

I equipped 13 stone martens with a radio collar

That sends out a signal.

It helps you to follow the animal around,

To locate its position.

I took a location of the animal every 15 minutes, at night.

And it gives you a very good definition

Of where the territory of the animal is.

You can see that, different colors for different martens,

So it's very clear territorial behavior.

Narrator: What he discovered is that the solitary male stone

Marten jealously guards his home turf

By scent-marking objects within it.

Now, you can imagine that the stone marten

That has scent-marked the car over here?

That car is gonna be driven away to a different territory

Within the same town, or a different town,

And that basically means that this stone marten

Is gonna come across a scent mark from a marten

That lives somewhere far away.

And that will obviously trigger their territorial response.

Greive: We now know that these vehicles were targeted simply

Because they are unwitting participants

In an ongoing stone marten turf war.

Narrator: Cars are routinely scent-marked

By a stone marten when parked in its territory.

When the car is moved outside of that area,

It's marked by another rival stone marten.

And when that vehicle then returns home,

All hell breaks loose.

Greive: The original stone martens will tear apart

Every aspect of that vehicle that they can,

Trying to obliterate the scent of their rivals.

And that's not enough for them.

Stone martens take it one step too far

By defecating throughout the vehicle,

To make it very clear who it belongs to.

Narrator: The final insult is ripping through the car's

Internal wiring with their sharp teeth.

And given the size of a stone marten's territory,

That means a lot of cars are in the firing line.

Keep in mind, a stone-marten home range is roughly 200 acres.

That's roughly 800 households.

Just assuming there's one car per household,

That's 800 cars for a stone marten to mark.

Narrator: And how are european drivers

Dealing with this vehicular vandal?

Well, one way is to send out small electric shocks

That deter the martens.

Another is to use sound, a very high-frequency sound,

That will put the martens off from chewing the cables.

Greive: But of course, the only truly effective measure

Is a paid-up insurance policy.

♪

Narrator: Costa rica,

July 30, 2018 --

Extraordinary footage is captured of an army

Ant structure.

Daly: When you first look at it,

It looks more like a rope or a vine,

But upon closer inspection, you can see thousands of ants.

Narrator: The colony has joined forces

To create a living bridge.

I think that's amazing.

Daly: The level of cooperation

It takes to pull this off is mind-blowing.

For an animal with a brain smaller

Than a pin-head, what they achieve is remarkable.

Narrator: But what motivated this miniature feat

Of engineering?

Why have these ants built such an incredible structure?

♪

Narrator: In costa rica, army ants have constructed

A living bridge out of thousands of their own bodies.

How? And why?

To find out, we need to know more about these mini marvels.

There are over 13,000 known species of ants.

Army ants are nomadic and have some of the largest colonies,

Making them a moving swarm --

One that eats almost everything in its path.

One single colony can be comprised of millions of ants.

And within that colony, they can consume

50,000 different prey items per day.

Greive: The ants' strength is entirely in numbers --

The ability to overwhelm an enemy

With relentless stinging and biting.

So, to a colony of army ants,

The entire planet is a moveable feast.

And they are absolutely relentless

In their pursuit of new prey.

Narrator: It's these qualities that make them

The most voracious predators in the rainforest.

On this occasion, the army colony is raiding a wasp's nest,

Carrying off the wasp larvae as a tasty treat.

But the route the army ants have taken is a puzzling one.

Greive: They've taken a very elaborate path.

Why wouldn't they just move directly across the roof

And attack the nest at its base?

It seems like a lot more trouble than it's worth.

♪

Narrator: It turns out that the stalk of the nest,

Where it's fixed to the ceiling,

Is covered in a wasp-made insecticide,

That only they are immune to.

Greive: The wasps create a substance which is quite toxic to ants,

And they coat the entire base of their nest with it.

Narrator: But instead of calling it quits,

The army ants build this living bridge

To circumnavigate the poison.

But how do ants dream up these elaborate structures?

To find out, we met with scientists

Who have been studying ant super powers.

Working with ants is always surprising.

We always underestimate what they can do.

Narrator: Case in point -- ant strength.

While we've always known

They are the heavyweight champions of the insect world,

It's only recently been revealed just how much muscle they have.

Hu: Ants are tremendously strong.

We know that they can carry 10

To almost 100 times their weight,

But their exoskeleton is much stronger.

It can take out 100,000 times an ant's body weight.

That's the equivalent of us being crushed by a house

And still be able to walk away.

Narrator: But it's the swarm intelligence of ants

That makes them such amazing architects.

They don't just build bridges.

When they encounter water,

They make a spontaneous floating device.

Instead of panicking, they'll actually start linking

Their bodies together and building this raft

That can float around on the water's surface.

The ants on the bottom of this raft you think would drown,

But each of these ants actually, when they're together,

They can carry bubbles with them,

Trapped between their legs.

So the ants on the bottom are basically breathing.

Narrator: Ants breathe through an opening in their abdomen

Called a spiracle, which the bubble supplies with oxygen.

But when it comes to bridge building,

It's the ant colony's team work that is the defining factor.

Hu: Cooperation is vital

When they're building these structures.

The ants had started out with basically a single line of ants.

But there was a lot of interest in going to this wasp nest,

So it recruited more and more ants.

And so, the bridge had to grow in width

To accommodate the traffic.

But because there's so much traffic,

The bridge had to become longer to support itself.

Burke: The solution is really elegant and extraordinary.

These ants formed this long length of chain,

On which other worker ants can run back and forth.

Narrator: And by creating a long path to get to the wasp nest,

The ants mount a much more effective raid.

Greive: Thousands of ants continue to fortify this,

Until we have active soldier ants going in to fight the wasp.

And wave after wave of army ants make their way into the nest,

Until they destroy the wasp nest,

And then wave after wave make their way out,

Carrying their booty.

Narrator: Proving that the humble ant is not to be messed.

Daly: Individually, ants may be fairly easy to overlook,

But once in a large group, they are unstoppable.

Grieve: Their ability to construct

Improvised architectural wonders on the fly is without peer.

They're one the most remarkable animals I know of.

♪

Narrator: November 2016, skokomish, washington --

Something fishy is going on on this flooded road.

Animals are using it as an aquatic crosswalk.

Conley: So, this a really cool video,

Where we see a flooded-out highway and fish

Just scooting their way across.

So, the question is -- why?

♪

Narrator: In skokomish, washington,

Fish are crossing the road to get to the other side.

Why?

♪

Nosal: Could these fish be trying to find more space

On the other side?

Maybe things are getting a little tight,

Food is getting a little scarce on one side

And they're trying to expand their range.

Narrator: If so, it wouldn't be the first time.

Conley: There is some footage of catfish crossing a road

In the kruger national park in south africa,

Where you see this behavior.

These large fish will come out of the water

And they'll go somewhere else,

They'll try to find a better habitat.

Narrator: Mudskippers are another famously mobile fish

That can be found in the indo-pacific,

From africa through to australia.

Conley: Mudskippers, they can actually move around

Outside of the water, in order to find

More beneficial conditions for themselves.

And they can survive for quite a long time.

Narrator: In fact, for as long as they can stay wet.

But the anatomy of catfish and mudskippers

Differs from the vast majority of fish.

Nosal: These species are actually able to gulp air

And use it for a period of time.

Most fish are not able to do that.

So it seems unlikely that these fish would actually be

Leaving water to find another place.

Narrator: It looks like these fish

Are not on an exploratory mission.

It turns out that this is an annual rite of passage.

And in fact, this phenomenon seems to happen

At the same time every single year.

Narrator: And there is one species of fish

That will swim past almost any obstacle

To get to where they need to go --

Salmon.

♪

Salmon are born in fresh water,

Typically fairly far from the ocean.

But as they grow, they will swim down toward the coast.

What's amazing is, we don't know a lot about their behavior

When they're out in the middle of the ocean.

What we do know is that,

When it comes time for those salmon to spawn themselves,

They find their way back to the coast,

And then they'll migrate their way

Through the branching rivers.

Narrator: In one of the most stunning feats of nature,

Salmon swim up to 2,000 miles upstream,

Leaping up to 12 feet in the air,

To return to their exact place origin to lay their own eggs.

But it takes more than physical strength to get home.

They also have to dodge predators

Who have staked out their route.

Nosal: A very important food source for bears,

For birds of prey.

Conley: It becomes a feeding frenzy

For all the animals in that environment.

Narrator: But for the salmon that make it,

This remarkable life cycle continues.

Once these migrating salmon swim upstream

And find their natal stream, they mate,

They give birth...

...And they die.

Narrator: But even after death, this super species lives on.

Nosal: These salmon,

They form an important part of the ecosystem.

They contribute so many nutrients

To the surrounding water that they're taken up

In the root systems of nearby trees.

Narrator: In the great forests of north america,

Up to 80% of the vital soil nutrient nitrogen

Comes from salmon.

As such, salmon have been named a keystone species,

Which means they are crucial to the environment.

Nosal: So they are uniquely tied to the rest of their ecosystem,

So it's very important for us to protect

Not only the spawning grounds

But the entire migration route for these salmon.

Narrator: The mystery now is -- how did the skokomish salmon,

Who are just at the beginning of their epic journey,

Even know where to go?

♪

Narrator: In skokomish, washington,

Salmon are playing chicken with the traffic.

It's part of their marathon swim, thousand of miles upstream

To get back to their exact place of birth to spawn.

But how do they even know where to go?

By using a salmon sensory super power.

Nosal: What's amazing is, using some combination

Of geomagnetic and chemical cues,

They'll actually find the stream where they were born

Using the unique signal of that water.

Narrator: So, for these salmon,

The road is just another obstacle

In their miracle journey.

Nosal: It's possible that this stream that they were

Traveling on happened to have a road built over it.

Maybe there was a pipe

That normally allows water to go through.

But if this stream is overflowing

Because of a big rain event,

The salmon, instead of going through the tunnel underneath,

Are gonna just go right on top.

Narrator: Proving that salmon will do whatever it takes

To make it home.