Original subtitles

Narrator: Ever wonder what happens

When animals have an identity crisis?

Nosal: How did this narwhal find itself among a bunch of belugas?

Narrator: Or what has a 70-mile wide radar footprint?

It's like an alien invasion.

What on earth is going on?

Narrator: And the answer to nature's

Most burning question.

What gives spiders nightmares? That does.

♪

Narrator: Nature is awe-inspiring.

But sometimes, it just doesn't make sense.

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

Narrator: Strange animal behavior,

Unexpected events captured on camera.

[ both screeching ]

The truth behind them is astonishing.

Man: My god!

Narrator: Nature's greatest mysteries solved.

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

Denver, colorado.

October 3, 2017. 7:04 am.

Meteorologist paul schlatter spots something weird and huge

Over the state's capital.

That morning, we saw a bloom erupt on radar.

We weren't exactly sure what it was,

But we certainly hadn't seen a pattern quite like that

In any of our recent memories.

Narrator: The mass is an astonishing 70 miles across

And is moving in a northeasterly direction.

Riskin: Weather officials are totally perplexed

Trying to figure out what they are looking at on their radar.

It looks like it might be a weird, strange cloud,

But people have been paying attention to weather

For a long time, and nobody had seen anything like this.

Narrator: The national weather service agrees

This is not a giant rain cloud.

Schlatter: The radar signature could not have been

A precipitation echo,

Simply because the other radar easily confirmed

That it was nothing weather-related.

It seems a bit of a strange one, so what on earth is going on?

Narrator: Well, storms aren't the only things radar can track.

Animals that swarm in large enough quantities

Can also appear on the screen.

So this could be the emergence

Of a giant bat colony over colorado.

♪

There are these bats in the united states

Called the mexican free-tailed bat

That form these really dense colonies inside caves.

Every square foot of the cave ceiling

Has 300 bats on it.

It's all furry and wiggling, and that's what it's like

During day, but then at night, they all come out

The mouth of the cave and spread out over the countryside.

Narrator: Schlatter confirms that bats could be visible

On the scale seen in denver that day.

Bats can easily have a swarm hundreds of miles across

And they take off at sunset and they expand

To a giant radar bloom that pretty much covers

Most of the radar umbrella.

Narrator: But with this theory, the timing is off.

The one problem with that would be that bats

Tend to roost and travel at nighttime,

But this swarm was detected in the daytime.

Narrator: If not bats,

Is a more obvious flying friend the culprit?

[ birds chirping ]

Schlatter: It certainly could be birds,

Because the typical pattern of birds migrating

Is in a nice big swarm as it moves over the radar.

Oftentimes in the morning, we'll see local flocks of birds

Take off right around sunrise.

Each fall and spring our radar network

Lights up with migrating birds.

It fills the entire central part of the united states.

The purple martin does flock in mass formations.

Birds are known to do that, particularly in the daytime.

Also, birds such as starlings do create

These very tight-knit formations of huge scale.

Narrator: While flocks of starlings can gather

In vast numbers, up to 100,000, even those figures

Don't come close to what was seen in denver's skies.

The problem is, there's really no species of bird

That should be making a cloud that's 70 miles wide.

Narrator: Birds are ruled out.

Riskin: What about insects?

There are lots of insects in colorado,

And if enough of them get up into the air

At the same time you could pick it up on radar.

The plague of locusts is of biblical significance,

But it's not just history.

It's something that actually happens even today.

Narrator: And it's not just locusts.

Woman: Do y'all see this? This is so creepy.

Oh, my god!

Riskin: I mean, it happened in wisconsin,

Right over the mississippi river,

Where millions and millions of mayflies

All emerged at the same time.

Daly: It seems to be this huge, apocalyptic swarm.

It's really hard to actually see what's going on

Until you get a closer look, when you start to see

Lots and lots of individual organisms.

Riskin: Mayflies will just be covering cars and houses,

And it's quite nasty, actually.

Woman: Whoa! They're all over me.

And the reason they're doing this is for sex.

They're all having sex in the air

Above the water and dropping eggs back down

So that they can reproduce for next year.

Narrator: However, the nearest sizable lake

Is over 140 miles away.

Mayflies hatch from large bodies of water,

And there in denver, there aren't

These large bodies of water to be able

To make this a plausible explanation.

Narrator: No water, no mayflies.

But another winged insect might be the cause.

Riskin: It could be a butterfly.

There are butterflies that migrate,

Like the monarch butterfly.

♪

Daly: Monarch butterflies are very unique.

They are one of the few butterflies

That actually can't survive winter.

So they pick up on environmental cues

To start a migration to warmer climates.

Riskin: Monarch butterflies are amazing.

Every fall, a butterfly will fly

All the way from canada, all the way down north america

All the way to mexico to get to

This one little patch of forest for the winter.

It's ridiculous, it shouldn't be possible,

And yet, they do it.

There's recent research that shows

That they actually create their own little microclimates

That keep them safe.

Narrator: As a group, they can maintain

A more constant temperature, surviving the winter

Before taking on the 3,000 mile journey north.

Riskin: The even weirder part is the trip back,

Because the ones that leave mexico go a little ways,

They stop, they have babies, those ones come out

Of their cocoons and fly a little ways,

And this goes five generations before they make it back.

And then the fall, those adults fly it in one fell swoop.

It is not normal for an insect to be able to migrate that far.

Monarch butterflies are ridiculous.

♪

However, butterfly expert mary ann colley

Is not convinced that monarchs are what appeared on the radar.

Monarch migration generally happens further east

Than the rocky mountains,

And so denver metropolitan area

Is not a primary flyway for the monarch migration.

Narrator: With denver not on the monarch super highway,

They're struck off the suspect list.

So could the swarm that we're seeing on the radar

Be caused by the weather after all?

Super weird, but I think that might be it.

♪

♪

Narrator: Denver, colorado.

October 3, 2017.

A mysterious, 70-mile wide mass has appeared on radar.

Experts don't think it's a storm,

Or any kind of animal swarm that they've seen before.

Stumped for an answer, the weather service

Puts out a call for witnesses.

We solved the mystery using social media

When our followers started tweeting in images

Of butterflies just covering their yards.

There was numerous accounts of not the monarch butterfly,

But instead, its relative, the painted lady.

Narrator: These butterflies have the same coloring as monarchs

And also migrate.

Their numbers were supersized by an unusually warm fall.

The painted ladies had the opportunity

To take advantage of our weather.

We still had hundreds of thousands of blooms

For them to feast on.

Narrator: The weather then created a butterfly bottleneck.

There was a low pressure system in denver,

And what that was doing was pulling butterflies

From all areas of north america,

And so all these butterflies

Were actually being funneled to the area.

Narrator: But then, one more thing led the butterflies

To make a forced landing in denver -- the rockies.

Riskin: So wind is pushing them up across denver,

And they would have kept going

Except that there's a whole bunch of mountains there,

So they sort of got pushed up against that and stopped,

And then landed, and as a result

Denver got a beautiful display of butterflies.

♪

Narrator: Hyogo, japan.

June 10, 2013.

Scientist observe some very strange behavior

In this orb weaver spider.

This is a weird one.

Daly: This spider is spinning a very different,

More unusual type of web.

Narrator: It's building a web

That makes no sense for catching prey.

This has to be one of the more bizarre behaviors

I've seen across the spider world.

Why would a spider do this weird thing?

Narrator: The answer is way beyond

Anything you can imagine.

What gives spiders nightmares? That does.

♪

Narrator: The spider's web pattern

Is usually a pretty familiar shape.

Riskin: You have an orb weaving spider

That's supposed to spin a web that looks like,

You know, the cartoon spiderweb does,

But this one doesn't do that.

Narrator: Could it be that this is just a new web design?

Daly: There are roughly 45,000 species of spiders.

So it could be that this orb weaver

Is building a new type of web.

The web is an integral part of a spider's life,

And of course, it's very important

For attracting its prey.

And different prey require different kinds of webs.

Some spiders can make crazy traps that

They push down on top of their prey to catch them.

Some spiders build big, huge, tennis-racket shaped things

So that something can fly into it.

Some build trap doors that animals fall into.

Narrator: The net-casting spider

Slings her web like a spidey superhero.

♪

She throws her silk over her prey,

And then knits it into submission.

Riskin: Spiderwebs are incredibly versatile.

They're incredibly strong. They're incredibly tough.

Daly: When prey gets stuck in a web,

It's pretty much impossible to escape,

And at that moment, the spider strikes,

Injects venom, and eats it alive.

Riskin: Spiderwebs are the most incredible things in nature,

But I think the best thing about spiderwebs

Is that they come out of a spider's butt.

Narrator: So could our orb weaver,

Who relies solely on its web to survive,

Be an innovator of spider silk engineering?

Our experts think not.

This spider's web is not suitable for catching prey.

Something else is going on.

♪

This spider might have eaten something

That is making its brain not work all that well.

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

Riskin: There are some experiments that were done

On giving drugs to spiders to see what will happen to them.

There's evidence that when you give lsd to a spider,

It makes a very weird web.

Daly: Spiders that have ingested caffeine,

Well, they create badly made webs.

Whereas webs exposed to pesticides

Will be eaten by spiders to get rid of them,

So that they can build a new one.

However, in this case, there was no evidence

That these webs were exposed to pesticides or lsd.

Narrator: But color footage of the spider reveals a clue.

That little weird thing on the spider's back.

Sounds far-fetched, but is it possible that

This spider's mind is being controlled by someone else?

♪

♪

Narrator: A japanese orb weaving spider is acting strange,

Dismantling its web and building something else.

It kind of looks like a cocoon,

And spiders don't make cocoons.

Narrator: But it's the yellow object on the spider's back

That's the giveaway.

♪

Riskin: It turns out that little thing on its back is a maggot.

And it's not just any maggot,

It's the maggot of a parasitoid wasp.

And what they do is lay an egg on a victim insect,

Or a spider in this case, and then as that egg hatches

And turns into a maggot, they eat the victim alive.

Narrator: But this parasitic wasp maggot

Isn't just eating the spider --

It's taking control of its brain.

This is a fascinating example of host manipulation.

So the wasp larvae will start to secrete these chemicals

Which essentially control the behavior of the spider.

So what's actually happening here is that the spider

Is being controlled by another animal.

Riskin: So the spider's not gonna make

The web that would help it.

It's gonna make a weird cocoon web

That isn't for the spider at all, it's for the maggot.

Once that thing is built, the maggot eats the spider,

Drops its husk to the ground, and then goes and lives

In that little cocoon until it can grow into a wasp

And do it again to somebody else.

Narrator: Terrifyingly, there are over half a million

Different species of these flying body snatchers.

There's no end to the nasty things they do to their hosts.

The glyptapanteles wasp lays up to 80 eggs

Inside a caterpillar.

Two weeks later, they erupt out like a scene from "alien."

So any time you see a wasp dragging a live creature around,

It's likely a parasite that's injecting an egg

Into its victim, turning it into a zombie slave.

Predators aren't scary. Parasites are scary.

And this spider has a parasite that is terrifying.

♪

Narrator: St. Lawrence river, canada.

July 2018.

The gremm conservation group are conducting research

When they make an unusual sighting.

Nosal: There's a pod of about a dozen beluga whales

Swimming along, but on closer inspection

One of the belugas looks a little different.

It's not as white, and it has a long tusk sticking out of it.

Narrator: It turns out the creature swimming with the belugas

Is the so-called unicorn of the sea.

Cooke: So of all the species of whales and dolphins out there,

There is only one that has an extraordinary long tusk,

And that's the narwhal.

Narwhals originally were thought to be mythical creatures.

They didn't even know that they existed until they were

First recorded as a species in the 16th century.

And its tusk is not like a horn

That you might associate with other kinds of mammals.

It's actually an elongated canine tooth.

Narrator: The narwhal's companions, the belugas,

Are white whales known for their extrovert personalities...

What a good boy! [ laughs ]

...And high-pitched singing,

Giving them their nickname "canary of the sea."

[ beluga whale singing ]

But the narwhal is 600 miles south

Of its normal range, and animal species normally

Stick closely to their own kind, which begs the question...

Why is this narwhal hanging out with these belugas?

♪

Cooke: So could this just be a one-off event?

Maybe it's just coincidence. Maybe they just happened to be

In the same place at the same time.

Narrator: But the behavior of the pod

Puts that theory in doubt.

Nosal: This doesn't seem to just be a one-off encounter,

Because the narwhal is doing everything it can

To fit in with its new friends.

Cooke: The narwhal is doing everything to join in

With the belugas, including blowing bubbles

Back and forth, which is typical beluga behavior.

Nosal: And it's reciprocal. The belugas seem to be

Treating the narwhal as if it were one of their own.

Cooke: Which suggests the relationship

Must be fairly well established

And not some kind of chance encounter.

Narrator: Could the narwhal and belugas be teaming up to hunt?

There are plenty of examples

Of what we call mutualism in nature,

Where two different species live in close proximity,

And they both benefit from living together.

Cooke: It's not uncommon in the animal kingdom

For different species to buddy up

In order to be successful at finding food.

Mongooses and hornbills actually have a relationship

That is mutually beneficial.

The mongooses have got their heads down,

They're snuffling around on the ground,

And what they don't eat,

The hornbill will hop along behind and pick up.

It's the hornbill's job to look out for predators,

So they're scratching each other's backs.

So it's possible that there's a similar relationship

Between belugas and narwhals.

Narrator: Maybe, but differences in their diet

Make this a long shot.

Conley: The reason why that probably isn't

The most likely answer is that

Their hunting habits are very different.

The things that they eat aren't the same.

Narrator: So why have these guys formed a pod?

What's going on here, I think,

Is an example of cross-species adoption.

♪

♪

Narrator: Bizarrely, a narwhal is filmed

Swimming with a group of beluga whales.

So how did these two species become one pod?

The most likely explanation is cross-species adoption.

Cooke: Now that probably sounds a bit strange,

The idea of one species adopting another,

But it's not altogether uncommon,

Especially amongst social species.

♪

Narrator: It turns out, other foster families

Have existed in the wild.

Cooke: There's footage of a group of sperm whales

Adopting a deformed dolphin.

They travel together, and you can even see

The dolphin and the sperm whale rubbing up against each other.

[ clicking ]

There's also instances of red-tailed hawk chicks

Being adopted by bald eagle mamas,

Living with the other bald eaglets,

And then eventually fledging the nest.

♪

Narrator: Red-tailed hawks will eventually

Strike out on their own.

Many whale species, however, thrive on community.

Cooke: Company is really important for social species,

So what I think's going on here

Is this lonely narwhal has sought company

With these belugas and been adopted by them.

Narrator: And it's been working well for some time.

This blended family were first spotted back in 2016.

Two years later, that same narwhal

Was still hanging out with his beluga bros.

Narrator: Raising all kinds of new questions

About animal impulses.

Nosal: It wouldn't surprise me if these intelligent animals

Felt that overarching urge to love simply out of instinct.

So it's not surprising that they might want

To share that affection with another whale,

A very closely related mammal.

Captions paid for by discovery communications