Original subtitles

Narrator: How can a dung beetle roll a ball in a straight line

While standing on its head?

How do they do it?

Narrator: Why would these birds want to hang out with an apex predator?

It makes no sense.

Narrator: And what is this mysterious creature

From the deep?

What could that alien creature have possibly been?

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 investigates the weirdest animal behavior...

That's amazing.

...And the most unexpected events...

What is causing that?

...Ever caught on camera.

My god!

These are...

♪

♪

2010. The florida everglades.

A great white egret

Is taking a ride on an alligator taxi.

And it's not the only one getting up close and personal

With these giant, toothy predators.

Egrets take sleeping with the enemy to a whole new level

And build their nests

Right in the heart of alligator territory.

Why are these birds hanging out with dangerous carnivores?

Nelson: It makes no sense.

I mean, it's a true mystery.

Alligators are predators.

Galante: Why would you nest above them?

Why would a little bird choose to make a nest

Next to a big, toothy reptile

That undeniably would want to eat anything

That comes in front of it?

Narrator: Could it be that gators won't eat egrets?

Are they the brussels sprouts of the bird world?

♪

Nelson: We know alligators are ambush predators,

And we know that they're also very opportunistic.

They'll pretty much eat anything.

Whether that's a bird, a fish,

A turtle, or a mammal,

They're gonna go for it.

They'll feed on almost anything they can get in their mouth.

Narrator: That includes egrets,

And the grisly proof is in the gators' weight.

Alligators that live underneath birds' nests

Are typically 13% heavier, healthier,

And fatter than alligators that don't live near birds' nests.

We do know the gators will take those birds,

So there's a risk to this association.

Narrator: A risk is one way to put it.

Take a few steps in the wrong direction,

And you end up crushed in monstrous, hungry jaws.

Some acrobatic alligators have even learned to jump up

To branch height to grab a meal.

Woman: Oh, my god! Look at this.

This is something...

Oh, my god!

Oh, my god.

So if you're an egret, why put yourself at risk

From these egret eaters?

Galante: Is it possible that these little birds

Just can't see these cryptic alligators?

♪

Narrator: Alligators are stealth superstars designed for ambush.

If you see an alligator, most of the time, it's not moving.

It just lays there. It blends into the environment.

Galante: They're dark on top and light on the bottom.

If you're a little fish looking up from below them,

All you see is light.

And if you're a bird looking down on an alligator,

All you're gonna see is darkness that blends in

Perfectly with the environment and the aquatic area.

Narrator: Semisubmerged, they look more like logs

Than animals.

Is it possible that the alligator's

Almost-perfect camouflage

Means that the birds just can't spot them?

Scientists wanted to find out,

So they set up an experiment using fake gators.

They proved the birds can spot the difference

Between a log and a dangerous predator.

Even so, egrets, herons, storks, and cormorants

All select nurseries in areas teeming with alligators,

So it seems nesting near them is no accident.

Galante: The birds are completely aware of the alligators' presence,

And yet they still choose to nest there.

The birds are actually selecting the company

Of our toothsome friends.

Clearly they see the alligators, but then here's the question --

Why are they nesting near a giant predator?

Narrator: What makes it even more mysterious

Is that at this time of year, the egrets have one priority --

Protecting the precious contents of their nests.

Nelson: They're wanting to raise up a bunch

Of very helpless bird chicks

In an environment full of predators.

Alright, you've got snakes, raccoons, opossums.

All kinds of creatures that would love to eat a bird's nest.

Maybe having an alligator underneath you

Is the least of your worries.

Narrator: Maybe,

But why actively seek out the alligators?

What seems to be happening is that the birds are selecting

To hang out where the gators are

Because they're getting some degree of protection

From the gators.

It's a cost-benefit situation

Because the presence of those gators

Will put off a much more serious group of predators.

Narrator: These alligators are taking babysitting

To a whole new level.

And riding on a gator's back

Provides the best bodyguard going.

It's all an extreme version of keeping your friends close

But your enemies closer.

These birds are basically keeping a psychopathic killer

In their garden to keep a burglar out.

It's an amazing, incredible, crazy adaptation

To having a safe life.

♪

Narrator: Tlakgameng, south africa.

November 2018.

A tourist on safari spots a beetle.

It looks like it's rolling a ball in a dead-straight line.

Woman where is it going with that?

She puts down a ruler to check just how straight

And witnesses the determined precision navigation

Of a dung beetle.

When you're dealing with a nonflat surface

And you're trying to roll a ball that's bigger than you,

It's going to wander around a little bit,

And so keeping it in a straight line is not trivial.

Narrator: Even more impressive, this beetle is upside down,

Doing a handstand, and moving backwards

While rolling with its hind feet.

He's not even fazed by the king of the jungle lying in his path.

He's determined to keep his dead-straight line.

I mean, they're standing on their heads.

They're walking backwards.

How do these beetles navigate in a straight line?

Narrator: And more to the point,

Why is such a straight path important

In the first place?

Well, it's all part of a plan to stop other beetles

Stealing their food.

These dung balls are the finest in dung beetle cuisine.

There could be over 100 different species

On a single dung pile, each fighting for the prize,

As witnessed by dung beetle researcher

Professor marie dacke.

♪

Dacke: They actually physically fight.

They will actually walk in and just put their heads

Under the other beetle and throw it off.

I mean, they go up into the air.

Narrator: And that means that when they find dung,

They can't hang around.

Once they've rolled up that ball of dung,

They're under time pressure to get out of there.

If it moves in a straight line with every footstep it takes,

It gets further and further away from the dung pat,

But if it was, instead, just randomly moving around,

It could also just end up at the dung pat again,

And that is disaster.

It can just have its ball stolen.

Narrator: A straight line helps them move their prize far away

From other beetle competitors as quickly as possible.

But how do they find this straight escape route?

Are they using the same technique

As other insect navigators?

So, one theory is that they've got a really good sense of smell

And they're following a scent trail.

Narrator: When ants or termites find something tasty,

They travel back to the colony to tell their buddies,

Leaving little blobs of pheromone scent as they go.

Think "hansel and gretel" bread crumbs.

They mark where they have walked,

So other ants will find the same scent trail,

And they will mark it again,

And then a third one comes, and it also marks it.

Narrator: This pheromone is super-potent.

Imagine the amount of ink

It takes to write a short paragraph.

If you had that much pheromone, you could make a trail of ants

That went around the earth four times.

Narrator: Could dung beetles be using the same technique?

♪

♪

Narrator: In tlakgameng, south africa,

We are unraveling how determined dung beetles

Can navigate in a dead-straight line.

Are they using the same tactics as ants or termites

And following a scent trail?

Ants, termites are famously very social insects.

They work together as a colony.

They work together as what we call a superorganism.

Narrator: But dung beetles are different.

They're not social insects, so it's not a group of them

That are sharing information

About which way to go to get food.

These are solitary individuals.

Narrator: They're solitary

And, to be honest, bordering on antisocial.

They're going in a straight line,

But they're not using a pheromone trail,

And they're not going back to a burrow,

So how are they keeping it straight?

Narrator: Turns out there's a clue right overhead --

The sun.

♪

Dacke: There are several different animals

That use the sun compass.

It's such an obvious thing in the sky, right?

There are monarch butterflies.

There are the honeybees that are maybe the most famous example.

Narrator: Marie is part of a team from lund university in sweden

Studying how various animals use the sun to find their way.

Could dung beetles be doing the same?

If so, they'd need to keep track of where the sun is

And adjust their position in relation to it.

Dacke: When the conditions in the sky are changing a lot,

We often see the beetle going on the top of its ball,

And then it rotates.

It switches its head out,

And we call it a dung beetle dance.

Narrator: If dung beetles are using the sun

To keep their straight line,

Marie can test it by using a mirror

To trick the beetle into thinking the sun has moved.

Dacke: And here comes the beetle.

Does his dance to check where the sun is.

And rolling.

And now we change the position of the sun...

In one, two, three.

And it's turning around, turning around.

It's now going back from where he came from.

One, two, three.

And turning back again

To its original direction.

Narrator: Changing where the sun is

Changes the beetle's understanding of where he is,

And to double-check it's the sun that matters,

Marie uses tiny beetle baseball caps to block their view.

Okay, here we go.

Outside again. The beetle on its ball.

And it's rolling,

But now it's rolling in circles.

This is because the beetle, when it's wearing the cap,

It can no longer see the sun,

So it can't use the sun to orient by,

And then it can no longer hold a straight line.

Narrator: Poor fella. He's not a hat kind of guy.

If we now take this beetle and remove its cap gently...

Okay.

Back to basics.

And we put it down.

And let's see what it does.

So, it dances on top of the ball,

Again gaining input to its compass, seeing the sky again,

Seeing the sun, and now it can use it

To travel in a straight direction again.

Narrator: A sun compass is the answer

To how dung beetles roll in a straight line.

Mystery solved.

Well, kind of.

There's more to it than that.

While some beetles are active during the day,

There are many that are nocturnal.

Dacke: I mean, the dung restaurant is open 24/7.

There will always be someone visiting this restaurant.

Of course, the nocturnal beetles,

They cannot use the sun, 'cause it's not there.

Narrator: In which case, without any sunlight,

How do these nocturnal species of dung beetle find their way?

Now, there are some dung beetles that can use the moon,

But there are also cases where a dung beetle can do this

When there is no sun and no moon.

Narrator: No sun and no moon,

How do these beetles roll in a straight line?

♪

♪

Narrator: In tlakgameng, south africa, acrobatic beetles use the sun

To navigate and roll their dung balls in straight lines.

At night, they use the moon,

But it turns out they can pull off the same trick

Even on moonless nights.

How?

So, what else is there for them to work with?

Stars, maybe.

Narrator: Could they be navigating by starlight?

♪

So, ancient seafarers were well known

To have used stars to navigate, particularly on moonless nights,

And plenty of animals do the same thing, too.

Migratory birds and even seals are known to do this.

So could the dung beetles be navigating by the stars?

Narrator: Are they spotting particularly bright stars

Like ancient mariners did?

Possibly, but unlikely.

'cause of the way a compound eye works on an insect,

It's gonna be very difficult for them

To be able to see the stars.

Narrator: Their eyes are way too small

To see even the brightest individual stars.

So what are they using?

Time for a dung beetle stargazing trip with researchers

From the university of witwatersrand in south africa.

In a planetarium, they can turn off parts of the sky, stars,

Or the moon to see what happens.

So, I'm just simply going to place the beetle onto the arena.

Narrator: Losing these celestial objects has no effect

On the beetles' ability to roll in a straight line,

So researchers think they must be using

Something much bigger to navigate by...

Perhaps something as big as a whole galaxy.

♪

We're removing the milky way so that we can see

If they will still be able to roll in a straight line.

Narrator: Remove the milky way,

And the dung beetle walks in circles.

Reinstate the milky way, and the beetle

Is back to going straight as an arrow.

So, what this basically tells us is that the beetles

Are actually using the milky way.

The milky way is the cue in the starry sky

That these animals are following

In order to move along a straight bearing.

Dung beetles aren't navigating by individual stars.

They're actually navigating by the whole galaxy itself.

Narrator: With their compound eyes,

The milky way is the brightest feature

Visible to the beetles in the night sky,

Just like the sun is the brightest object during the day.

The tiny humble dung-clearer of the animal kingdom is,

In fact, a galactic navigator.

♪

November 2017. The gulf of mexico.

3,000 feet below the ocean surface, a scientific team

Led by professors brennan phillips

And david gruber are exploring the deep sea,

Using a submersible

With a highly sensitive low-light camera,

When a bizarre apparition comes into view.

Nosal: It's cliché but true that we know more

About the surface of the moon

Than we do the deepest parts of the oceans on earth.

What could that alien creature have possibly been?

♪

♪

Narrator: In the gulf of mexico,

A deep-sea research team

Comes across a strange object 3,000 feet down.

What could this be?

Similar-shaped objects

Have been seen floating at the ocean's surface.

This is a whale's afterbirth.

Could this be what was caught on camera 3,000 feet down?

In theory, yes.

Nosal: Although there would certainly be whales nearby,

They're going to give birth near the surface

Because that baby calf is going to need to take a breath

Shortly after being born.

They're going to have to deliver the afterbirth

After the calf comes out.

Just like a human placenta, any mammal placenta

Is gonna be highly nutritious,

And that's gonna just be gold for other organisms

To try to eat on the way down.

There's no way it would have survived that deep.

Narrator: So, if it's not a whale's placenta, what else could it be?

3,000 feet below the ocean's surface,

The pressure is over 1,300 pounds per square inch.

Some creatures, like this chimaera,

Have evolved extra-bendy bones to cope,

But some deep-sea animals, like squid, octopus,

And jellyfish have no bones at all.

Could this strange bag-like object

Filmed thanks to david gruber's pioneering research

Be a boneless deep-sea animal?

His team of scientists analyzed the movements

And discovered that what they were looking at was a creature

That has only been seen a handful of times before.

It just looks like very, very simple body plan,

Just a flowy bit of membrane, and there's not much else to it.

Nosal: It's actually a kind of jellyfish called deepstaria.

That's the scientific name.

The common name is aptly called the placental jellyfish,

So those who thought that it was a whale's placenta

Were not too far off.

Narrator: This jellyfish has no tentacles.

It doesn't need them.

It waits for its dinner, mostly crustaceans,

To swim upwards and then engulfs them in its saclike body.

♪

And that wire netting pattern all over its body

Is actually its digestive tract.

The mystery creature from the deep

Was actually a very rare jellyfish.

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

Captions paid for by discovery communications