All language subtitles for NOVA - S49E02 - Secrets in the Scat_track4_[eng]

Viewers like you make
this program possible.

Support your local PBS station.

♪

SCOTT BURNETT: It might
look dull and smell disgusting,

but when you know how to read it,

poop is the oracle of knowledge.

Ecologists like me call it scat,
and we're passionate about it.

Just imagine the size of the bum
that this dropped out of.

The world is full of fabulous
feces stories,

like the mystery of the Australian wombat

and its cube-shaped poop.

PATRICIA YANG:
How would a square come out of

a round hole?
That's the big question.

[whale moans]

BURNETT:
Or the tale told by DNA

in blue whale scat.

And what's really cool is,
we've kind of figured that out

by digging through their poop.

BURNETT:
Even in tiny krill,

we're discovering the real power of poop.

SO KAWAGUCHI:
For me, it's the most important

animal on the planet.

BURNETT: There's always
a new mystery to be solved.

"Secrets in the Scat."

Right now, on "NOVA."

♪

♪

BURNETT:
My name is Scott Burnett.

They call me Scat Man.

When I was young, I wanted to be
a wildlife tracker,

looking for secret traces
that would lead me

to extraordinary creatures
in the vast Australian bush.

My dream came true:
today, I'm an ecologist.

And I use scats to tell
the stories of species.

I look for clues in poos,

facts in feces.

I know my shit.

♪

Scat is a gold mine of information.

It illuminates the role of poop
in the health of ecosystems

and how animals communicate.

It holds the secrets of wildlife behavior

and can even help to save
species from extinction.

All of this we can learn
without invading their privacy.

That's why scat science is real science.

♪

Join me on a journey where few
people have dared to tread,

looking for scats,
unraveling their secrets,

and meeting other scientists
with a passion for poop.

♪

♪

This scat tale begins in one of
the oldest rain forests

in the world.

I'm here to investigate
a spectacular dropping.

It may hold clues to why these forests

remain so diverse and resilient over time.

It comes from the bottom
of an imposing bird.

The southern cassowary.

♪

The cassowary is flightless,
like the emu and the ostrich.

Its wings may be useless for liftoff,

but powerful legs can propel
the bird into the air

to reach overhead fruit.

This taste for the bounty of the
rain forest is the beginning

of a beautiful story.

A story that can only
be revealed if we stop

and take the time to read its scat.

Well, thanks so much.
Yeah. Good luck, all right?

Cheers. Ta.

♪

[voiceover]:
You can sometimes hear and feel

the cassowary's deep, booming
call before you see one.

[cassowary rumbling]

The low frequency may help them
communicate

through these dense tropical forests.

♪

[grunts]

You have to be careful; you have
to really respect these birds.

You never know when you're going
to run into one

when you're following their tracks.

They do have the potential to
inflict considerable harm.

Ah, here's his trail here.

Whoa.

You can see the cassowary's come through

the creek here, and there
are these beautiful footprints

in the soft mud.

It's quite slippery.

And he's come through...

This one, they look just like

little dinosaur footprints, don't they?

♪

[voiceover]: The tracks
should lead me to fresh scat.

But first, they deliver a rare encounter.

♪

The first time you come across a
cassowary in the forest on foot

is a really intimidating experience.

This animal is virtually looking
at you eye-to-eye.

And it has these massive talons
which it uses in defense.

Looking at a cassowary,
you can see straight back

into the dinosaur heritage
of all our birds.

It's very hard to escape the
feeling that you're interacting

with something not too far
removed from a velociraptor.

♪

So that male cassowary

just dropped this scat
before my eyes moments ago, so

you can still feel the warmth
coming off that,

and it's chockers full of
rain forest fruits.

And there's this beautiful
big cassowary plum seed,

and this is really significant.

[voiceover]: Because
cassowaries and cassowary plums

have a mutually beneficial relationship.

The fruit is large and poisonous,

which limits the number of species

that can disperse its seeds.

The cassowary is the only animal
in these forests

that can swallow this fruit whole.

The fruit passes through
the cassowary's gut so fast

that only a small portion
of the toxins are absorbed.

And when the intact seed
comes out the other end,

it will sprout in a matrix
of ready-made fertilizer

at a distance from the parent tree.

The plant gets its seeds dispersed

and the cassowary gets to eat...

a fruitful relationship if ever
there was one.

The cassowary disperses
the seeds of around 238 plants.

But just how effective

is the big bird to the health
of these precious forests?

♪

After the rainy season,
I'll return to the Wet Tropics

to take part in an experiment
designed to find out.

It involves a much closer look
at cassowary scat,

which is right up my alley.

♪

Scats are splendid things,

filled with fabulous facts.

From them, we can identify species...

[animal shrieking]

...and their most recent meals.

And once in a while,
a scat comes along that elevates

poop science to another level.

Introducing the cube,

the only six-sided scat in nature,

an exceptional excrement,

direct from the bottom
of the common wombat.

Wombats are Australian marsupials.

They graze continuously.

It can take up to two weeks
for them to digest their food.

The process squeezes out
every last drop of water,

a good strategy in Australia's
harsh climate.

But that doesn't explain how, or
why, the end result is a cube.

♪

The first serious research into
this mysterious scat

happened independently
in the U.S. and here in Tasmania

around the same time.

It seemed the scats had aligned.

I'm here to see the result
of that research.

My scat investigations usually
begin once the

shit hits the ground.

♪

In this case, I need to know
what goes on behind the scenes.

♪

Like many scientific breakthroughs,

the investigation into this
mystery started accidentally,

here, inside the laboratory
of Scott Carver.

G'day, Scott, how ya goin'? G'day.

Good to see ya, come on in.

BURNETT:
There she is.

CARVER:
Yeah, she is.

Oh, look at her.

Yeah, she's a female adult,

would have been hit by a car.

Just pop her down here.

CARVER [voiceover]: I study
infectious diseases of wildlife,

and as part of that work, we've
been dissecting some wombats

that are either, had disease and died

or had been hit by a car and died.

And we were doing some of these
dissections.

And to our surprise,

for the first time, we actually
discovered that they have these

cubes formed inside of their body.

CARVER: So it was just a situation
just like this,

where we discovered that the
feces were formed into cubes in

the last part of the intestine.

And so before your work on this topic,

there were a few competing
hypotheses about where that

cubed shape of the wombat scats
comes from.

Yeah, one of them was that they
had a square-shaped anus.

So that bum doesn't look too
square-shaped, does it?

No, it's not square-shapedat all.

BURNETT [voiceover]: Further
confirmation came when they performed

the first ever CT scan on a live wombat.

That's not a square.

CARVER:
So we're just gonna start here

below the rib cage

and just cut a line down

and finish straight down here
and reveal the intestines.

Now if you peel this back here a
little bit, we can actually see

some of these cubes starting to form.

Yeah, it's amazing. Yeah, it certainly is.

Yeah, you can really see the cubes here.

Mm, they're really well-defined,
aren't they?

Yeah, really clearlydefined.

Really sharp edges along those corners...

♪

CARVER [voiceover]: So we
started collecting some of the tissues

from these intestines
to look at the thickness.

At the same time,

we had some colleagues in the
U.S. contact us,

and they study the fluid
mechanics of many things,

including how feces are formed.

And, and they were interested in this

when somebody pointed out that
wombats can produce cubes

during a conference.

BURNETT: One of the scientists
on the U.S. team was Patricia Yang,

based at Georgia Tech, an expert
on the physics of feces.

She thought she knew everything
about poop,

until she was faced with the cube.

So I did some online search,
and a lot of images or photos

come up, and those are...

For, for my eyes,
it looks very artificial.

And that increased the doubt
even more, like,

is that even a real thing
comes out from animal body?

But I just couldn't believe it,

because that is way too weird
from my knowledge of feces.

And that triggered my curiosity.

I was thinking, if, for normal
defecation process

for most mammals, including humans,

the feces come out like
a toothpaste coming out.

So when you squeeze it,

the shape of feces is the same
as the, the orifice,

and this sort of soft matter
comes out slowly

but smoothly, as a sausage.

But how would wombat have this
cubicle shape?

♪

Our hypothesis is that
it must be the intestine

that molded this shape.

There might be something that's critical

but invisible to our eyes, and
we're going to figure this out.

CARVER: The logical next
thing to do for us was to examine

microscopically what the tissues
looked like.

We found thicker and thinner muscle

around that circumference,

and along the length of the intestine,

these sort of thicker and
thinner regions formed bands.

YANG: So we have never seen
this before in any kind of animals.

We are wondering

if different thickness,
the thicker and thinner bands,

how would that affect the stretchiness

of the wombat intestine?

So we put a wombat intestine

into this tensile test.

Tensile test is the way to test
how stretchy this material is.

♪

And we discovered that the
wombat intestines stretch,

but they are not stretched in even way.

For the thicker part, they
stretch less than the soft part.

We were surprised that the
stretchiness were four times

different among these two bands.

With this measurement,
we fitted this information

to a mathematical model,
and that it contracts.

And over several cycles' contraction,

we see a shape with four corners.

CARVER: I've got a really
simple way of showing pretty much

how they form these cubes
using this rubber band here.

And so we can just kind of pinch
the sides of the rubber band

and kind of simulate those,
those more stiff regions

of the intestine.

And if you just hold it like
this, you can just go like that,

and it begins to form a cube.

So when the contractions happen,
it is basically squeezing

the feces into this shape,

and it does this rhythmically over time,

and so they eventually get
molded into that.

And as the moisture is absorbed

out of the feces, it starts to
fragment along its length

and form the distinctive actual
cubes that come out at the end.

♪

So after three years of
collaborating and work

with a big team,

we finally figured out why
wombat cube have six faces.

[audience cheering and applauding]

BURNETT: For their
discovery, the international team

won a coveted Ig Nobel Prize

for science that makes you laugh
and then think.

Thank you.

Wombats are solitary
herbivorous marsupials.

They produce cube-shaped scats.

When feces dry, it contracts
and forms cracks.

Wombats are scientific proof
that you can squeeze

a square peg into a round hole.

[audience laughing, applauding]

BURNETT: The time we were
able to spend in the lab gave me

a really great understanding
of how wombat scats get formed.

But the question still remains:

what role does it serve
in the wombat's ecology?

♪

The most popular theory about
why wombat scat is cubed

is that the shape makes
communication easier.

But first we have to ask

if wombats even use their poop
to message one another,

whatever its shape.

In the next two days,

we'll conduct a pilot experiment
to help find out.

♪

Maria Island in Tasmania

is the perfect natural laboratory.

There are between 2,000
and 3,000 wombats here.

♪

Wombat scats are not all
obviously cube-shaped

like we saw in the lab.

Variations in physiology, diet,
and moisture

cause shape changes.

It can even depend on
how you look at them.

But they do all have six sides,

which is what makes them special.

Wash your hands.

There are thousands of wombat scats

aggregated in clusters across the island.

These are latrine sites.

Many animals use latrines
for social communication.

They sniff out the scent of who's around

and leave their own scat messages.

But are wombats using their
latrines for this purpose?

It's never been directly
investigated, until now.

Our pilot experiment is simple.

We'll drop the poop of a
stranger wombat into a latrine

and watch what happens.

If the wombats are communicating
with their scat,

they should react to the new poop.

The home ranges of wombats
overlap and vary in size.

To ensure the poop is foreign,

I pick fresh scat
from one side of the island

and take it to the other,

where I've found a very
impressive latrine.

That's a lotta shit.

And here's a selection
of fresh, fresh pellets.

[voiceover]:
If these latrines are being used

for social communication,
you'd expect that where we

dropped foreign wombat pellets
in, there'd be some sort of

response from the resident wombats.

I set up camera traps on
ten latrines across the island.

I add stranger poop to five of the sites

and leave the other five unchanged.

These are our control sites.

We'll use them to gauge
what normally goes on

around wombat latrines
so we can quantify any effects

from adding scats.

I'll return to check
the camera traps in 24 hours.

♪

Scott Carver has left the lab
to join me on Maria Island.

He's going to perform an elegant
experiment designed to test

another element of the wombat
communication theory:

that the cubes give the wombat
an evolutionary advantage.

♪

Here's the thing:

wombats have bad eyesight, but
they have a keen sense of smell.

If they are communicating
through their scat,

they're well equipped to sniff it out.

So it shouldn't be surprising
to discover that the process

of evolution has found a way
to amplify the scent

of wombat scat.

There's a little wombat
poo tower over here.

[voiceover]:
Meet the wombat scat stack.

Does the unique shape

of wombat scat have any bearing
on poop stacking?

Tonight, we're going to find out.

But first, we need some essential data.

♪

CARVER: So I reckon we might be
able to get a measurement on how high

the, the bum is from the ground
here, Scott.

This one seems pretty habituated.

Yep, looks like about 15 centimeters.

BURNETT [voiceover]:
This is science.

This is what we do.

What would happen if a wombat
had round-shaped scat?

Would it stack?

We've made cubes and spheres
out of modeling dough.

We'll drop them from the height
of a wombat's bottom

and compare how they land.

The hypothesis is that the cubes
will aggregate

and the round ones will roll away.

So it's super-simple little experiment.

Wombats often drop them on a rock or a log

that's at a similar angleto this.

And here we can just test
with the circular ones

how well they go relative
to the cube-shaped ones.

If the hypothesis is correct,

the cube-shaped poo, the yellow ones,

shouldn't spread out as far as
the pink ones, correct?

Yeah, they shouldn't, they should end up

a little bit more closer together and...

It's looking good so far, looks right...

It's off the table! Hey!

Pretty striking, eh?

[laughs] You, you couldn't hope for
a better result.

That might be our best trial so far. Yeah.

So, not surprisingly,
balls roll further than boxes.

But, as scientists, we have to
actually do the experiment, hey?

BURNETT [voiceover]: We have so
much fun that we replicate the experiment

into the wee hours of the morning.

Time and again, the cubed shapes aggregate

and the sphere shapes dissipate.

It looks like pooping cubes

would have an evolutionary advantage

for a near-sighted wombat

that needs to sniff out a latrine.

It's a fine theory,

but we still have no scientific proof that

they do communicate through their scat.

Scott Carver's on his way back to the lab,

and I'm about to find out
what's happened overnight

at our pilot communication experiment.

This is really exciting.

There's a new pile
of fresh scats right here

beside the stranger's scats I
dropped in yesterday afternoon.

So a wombat's definitely been here,

and, you know, pooed overnight.

Let's have a look at the camera
and see if we can see any

sort of interaction with this
new pile that we've dropped in.

That's very exciting.

[inhales]

[exhaling]:
Let's see.

Ah, here comes a wombat.

Ah, it's sniffing the new pile.

Oh, my God.

And then it's

taking a poo

right in front of the camera.

[laughs]:
It's got its backside facing

directly towards the trial camera.

So there we go.

That's our first bit of evidence
that these latrines do trigger

some sort of scent-marking behavior,

or that the strange scent here
has, has some influence

on the behavior of these wombats.

At the five control sites where
I didn't place scat,

the wombats showed no reaction.

But at three of the five
manipulated sites,

wombats responded by sniffing
the foreign scat

and then pooping.

What could the wombats be talking about?

Because they're mostly solitary animals,

it would be really important

to know reproductive status of females

or to stay clear of dominant animals.

That all still remains quite speculative,

but I think at this point,

we can say that the latrine sites are used

in some sort of social communication way.

♪

While we need a lot more
information before we can say

for certain what's going on here,

the latrines of some mammals
have been well researched,

including one animal under
constant threat from poachers.

Across the ocean, the wondrous latrines

of Rhinoceros unicornis await me.

They may hold the key

to survival for this vulnerable species.

♪

The greater one-horned rhinoceros

is best viewed from a distance.

It's the second-largest
of all rhinoceros species,

as heavy as an S.U.V.

and able to charge at the speed
of a galloping horse.

The beauty of scat science is,

we don't have to catch one
to learn about its life.

So this is an amazing spot here.

We've got rhinos grazing out on this side,

maybe a couple of hundred meters,

and on the other side,

rice paddies and villages.

There's just over 100 rhinos

in this area of just under
40 square kilometers.

♪

[voiceover]: Which makes
the Pobitora area a great place

to find a rhinoceros latrine.

♪

Look at the size of this scat.

This is one that was dropped last night.

It's really fresh,
sort of beautiful stuff.

If this had come out of
the bottom of my compost heap

at home, I'd be really pleased
with how well it's gone.

There's all these

really finely masticated
and digested plant material.

And just by coincidence, there's a cowpat

here in front of the rhino heap.

So you can really get a sense of
how massive these animals are,

and they're just roaming in and out of

the village here, and everyone
seems to be getting along.

Just imagine the size of the bum
that this dropped out of.

♪

[voiceover]:
These are just single scats.

I'm after the motherlode.

I've made a pair of tongs out of bamboo

to handle the scat hygienically.

And there we go.

[voiceover]: Coming
across fresh scat in the wild

is a golden opportunity
for a scatologist like me,

even if it's not for my research.

Collecting samples for other scientists

can help their studies.

Some of this rhino poo
may even be used to help save

the greater one-horned rhinoceros.

So this large pile of scat here

is a latrine site
used by a few different rhinos.

They communicate to

the other animals in their population

via the chemicals in their scats.

They communicate social status
and reproductive status

and who's in the neighborhood.

It's like a Fecesbook for rhinos.

♪

[voiceover]: But this social
platform also attracts ruthless killers.

A fresh poop pile is a message to poachers

that rhinos visit here.

They're killed for their horns,

which are smuggled out of the country

and used for luxury goods

or in traditional medicine
in parts of Asia.

[people talking indistinctly]

Scientists have figured out
a way to protect the rhinos

by using their scat for forensics.

They collect scat in the wild
and extract DNA,

which goes into a database.

When a dead rhino is found

or a rhino horn
confiscated from criminals,

authorities can match its
DNA with DNA in the database

to locate where it came from.

The DNA evidence
can be used to convict poachers

and to know where
to concentrate police efforts.

In the 1900s, they faced extinction.

Now there are over 2,600 greater
one-horned rhinoceros in Assam.

Perhaps this scat
will go towards saving one more.

Just using my GPS here

to get a geolocation for this sample.

[voiceover]: Latrines
helps rhinos communicate,

and now they may also protect

these superb pachyderms from extinction.

That's a good poop story.

♪

Rhinoceros scat is easy to collect.

But some scat is more elusive,

especially that of the most
prodigious pooper on the planet.

♪

I am about to leave my comfort zone,

turn my back on the terrestrial realm...

where animals leave their scats
in forests and fields...

and head to sea with a whale biologist

who shares my passion for poop.

I'm known as the whale poo girl,

which I embrace wholeheartedly,

and it goes back to where

this whole blue whale project
in Sri Lanka began.

WOMAN:
Blow!

DE VOS: I was off the
southeast coast of Sri Lanka

doing some research on sperm whales

on a whale research vessel,

and had this amazing encounter

with an aggregation of blue whales

and a floating pile of whale poop.

Everything that I had been taught

in my undergrad and in school
about blue whales

was that they did these
long-range migrations

between cold feeding areas and
warm breeding and calving areas.

BURNETT: Asha de Vos discovered
that the blue whales in these waters

have a different lifestyle
from most others.

They don't migrate and
they have some unique behavior.

♪

What was going on?

Turns out the answer
could be in their scat,

and today, I hope to see some of it

while Asha continues her research.

Hi, Scott, good morning.

Hey, Asha.

Welcome.
Come on board.

It's good to see you. Great to meet you.

Come on in. Thank you.

♪

DE VOS:
As soon as you see a blow...

so it's a very tall, powerful spout

that you'll see in the distance...

do shout it out.

We've got the team ready to
take down the data.

Yep. You'll keep your hand out

so that we can make sure
we don't lose the animal.

We'll try to get a distance
and sort of a bearing

to the animal and start to approach to,

within a reasonable distance
so that we can start to get

all the other information that we need.

So, do you think you're
ready for the task?

Cool, let's go do it.

All right, let's go.

♪

BURNETT [voiceover]: We're waiting
for a whale to come up to breathe and,

hopefully, to leave a gift...

one of the largest scats in the world.

♪

We don't know where, when,

or even if a whale will appear.

Neither do the hundreds of whale watchers

that are out on the water today.

But I... and they just...
Yeah, and these whales

were here just waiting.

These whales have been here for centuries.

Yeah, yeah. And that's the thing.

And most people in Sri Lanka
didn't even know

these whales were in our waters.

And then I started getting,
like, mail from people saying,

"We didn't know there were
whales in our waters."

So is this when the tourism industry

all sprung up, too?

Just in the last decade?
WOMAN: Blow!

Yeah... sorry. [people exclaiming]

[people speaking non-English language]

[people calling out]:
Blow! [camera clicking]

[De Vos speaking non-English language]

Blow!

DE VOS:
Hurry up.

[camera clicking] WOMAN:
Blow!

BURNETT [voiceover]:
The encounter only lasts a few minutes.

BURNETT: Blow. [people exclaiming]

Blow.

BURNETT [voiceover]:
We can follow their breaths,

but we can't follow them down.

DE VOS: It's gonna go,
it's gonna go, it's gonna go,

it's gonna go, it's gonna go.

WOMAN:
Whoo! [people talking in background]

Dive angle?

Dive angle 110.

WOMAN: One-one-zero
[inaudible].

Time: 10:07.

DE VOS: And you were so excited
when you saw the blue whale,

and then when you saw, you know,

it skimming under the surface, and you saw

that beautiful, um... That blue color.

..blue color. Turquoise, mm-hmm.

But wait till you seethe poo.

I cannot wait
to see your face, I bet you. Mm.

[people talking in background]

BURNETT [voiceover]: We get a
distant glimpse of surface feeding.

There's a wealth of marine resources

in these warm waters for the whales.

MAN:
Whoo!

DE VOS: We've been seeing
more feeding this year

than any other year, really. Mm.

Which is fantastic. Mm.

But the real mystery is,
where is all that feeding going?

What happens to it?

Why is it not coming out of the back?

Mm. Where's our poo?

Right? [chuckling]

♪

BURNETT [voiceover]:
The whale leaves no trace.

But Asha doesn't disappoint.

She's defrosted samples
no longer needed for research.

Not only will I get
a chance to see it up close,

but to experience just how difficult

this scat is to collect.

DE VOS:
You have to be pretty much

there when it happens. BURNETT:
Mm.

Quickly get the net out,
grab as much as we can.

Um...

BURNETT: It doesn't last long
in the water.

It really is red gold,

isn't it?

Gold of the ocean. [De Vos murmuring]

I'm complete as a scatologist.

♪

DE VOS: This is where the science happens,

because when we start
trudging through the data,

that's when we start to see the trends,

that's when we start to
recognize individuals,

and that's when we
start to build the stories

around these animals.

In Sri Lanka,

our blue whales
fluke up before a deep dive

more often than anywhere else
in the world,

maybe, like, 60% of the time.

So this is lifting their flukes

out of the water..Exactly.

DE VOS:
And for a long time,

we tried to figure out what that was,

what was the reason.

And what's really cool is,

we've kind of figured that out by

digging through their poop.

♪

BURNETT [voiceover]:
A piece of prey DNA

from a scat sample was analyzed.

What they found showed just how unusual

the Sri Lankan blue whales really are.

Everywhere else in the world,

blue whales
would feed on krill. Mm.

Here, they're feeding on a
particular kind of shrimp

that is actually deeper
in the water column.

And so they do have to get deeper.

It makes a lot of sense
that you want to make yourself,

turn yourself into a kind of
a torpedo to descend.

[whale calling]

And so, you know, the poo's sort of been

this really big clue into

not just understanding, you know,

what are they feeding on,

but how does that impact their life cycle,

and their life history
and their behaviors,

which I think is really neat.

♪

BURNETT: After three
days on the boat with Asha,

I have my sea legs.

Now biologist and underwater cameraman

Simon Enderby

has invited me to see
a blue whale beneath the water.

He won't be letting us jump in

unless it's completely safe
for the whale and for me.

But our encounter today is with

something much bigger than a whale.

[ship horn blaring]

There's been a flotilla
of whale watching boats

following this whale
and her calf all morning

this morning, really harassing it,

and they've chased her out
into the shipping lane,

which is where we're sitting now.

It's dangerous out here for them.

Strikes from propellers of these
big cargo ships kill whales.

I had hoped to get into the water,

you know, sensitively,

ahead of the whale,
and let her swim past me,

but I'm feeling quite distressed at

what I've witnessed here this morning,

and I don't really feel like
adding to any of the stress

that these whales are obviously feeling.

This reminds me, it really drives home

why it's so useful and so,

such a powerful tool to use scats

to understand the ecology of animals...

whales or animals on the land.

It allows us to get into their lives

without being in their faces

or invading their personal space.

[voiceover]: Scat helps
us to understand whales,

and it may also help fertilize the oceans.

Here's how we think it works.

Migrating blue whales
head to Antarctica in summer

to feast on iron-rich Antarctic krill,

then they poop.

The iron in their poop may
feed microscopic phytoplankton,

which generates a large percentage

of the planet's oxygen.

Phytoplankton are
the favorite food of krill,

which in turn are eaten by whales.

And on it goes.

It's unlikely that whale scat
alone is sufficient

to feed the world's phytoplankton.

But there's another, not so
obvious poop in the loop:

the scat of the Antarctic krill itself.

Could it be providing the iron
that phytoplankton need?

♪

Unfortunately, that's not me on deck.

Scientists from the
Australian Antarctic Division

are investigating the biology of krill.

Doing research in the Southern Ocean

is an enormous challenge,

so they've figured out how to breed

this little crustacean in captivity.

Krill ecologist So Kawaguchi

has helped develop a world-class aquarium

dedicated to krill research.

Today, he's invited me

to watch the pooping of the krill.

They look like giant icy poles,

don't they, in those plastic bags?

[laughing]:
Yes.

So these are the phytoplankton

isolated from Antarctic Ocean,

so we culture these for,
as a food for krill.

Are we going to have a chance
to feed some krill here today?

Yeah, of course.

I'm looking forward to that.

I'm imagining sort of the water boiling

like a pool full of piranhas.
[Kawaguchi laughs]

KAWAGUCHI:
You don't really want to

pour it, you know, from the, the pot.

You just gently, you know, submerge it

and then release it
into the, the water. Okay.

Yeah, that's it.

Oh, they're very reactive, aren't they?

Yes. They're straightaway...
they're even

going into the bucket.

This is exciting. Yes.

They're beautiful little animals,

although not even that little.

I mean, they're...
I'm surprised

at the size of them.

KAWAGUCHI: They're really
cute when they, you know,

come up and see you,

because they have really big black eyes,

you know? BURNETT:
Mm.

And yeah, it's just really nice to watch.

Mm. Yeah, you know.

♪

KAWAGUCHI: For me, it's the
most important animal on the planet.

Because, you know, the amount of krill

that we have on the planet is enormous.

Like, it weighs almost equivalent to

the total weight of
the human being on the planet.

♪

You know, when they poo, they poo a lot.

BURNETT:
Researchers estimate there are

over 400 million tons of Antarctic krill.

The Australian Antarctic Division

recently recorded a super-swarm

made up of hundreds of millions of them.

There are records of super-swarms

several kilometers long.

Imagine all that scat!

30 minutes after feeding,
So's krill begin to poop.

The delicate scat threads
are easily fragmented by

the constant motion of their tiny legs.

At a microscopic level,
when the pellets break up,

a cloud of nutrients
is thought to be released.

What the nutrients are

and how they are used are questions that

researcher Abigail Smith wants to answer.

My field is trace metal chemistry,

and that's a really important field

in the Southern Ocean,

where we have such
low concentrations of iron.

So we're talking, like, nanomolar level.

Really, really low.

Sources of iron down there

often come from things like
melting sea ice.

When ice is melting in spring,

you get this sudden input of iron,

which stimulates this big
phytoplankton bloom.

But once those sources have
pretty much been exhausted,

we need something that recycles
and maintains the iron supply.

And that's where krill come in,
and we believe that

through their excretion
and their defecation,

they're actually putting iron
back into the water.

BURNETT: And that iron
may be fertilizing phytoplankton

in a continuous cycle.

Krill ingest iron
when they eat phytoplankton;

it's then excreted in their scat.

Bacteria break down the scat,
liberating the iron

in a form that
the phytoplankton can absorb.

But it's difficult to know

how much iron is involved in the process.

SMITH: It's not something
that we can measure

very easily in the field,

you know, going down to Antarctica.

You can try and measure the iron,

but the iron's taken up so rapidly that,

you know, you really
have to be there on the spot

to measure any influence.

BURNETT: As a step to finding
out how much iron is available

for the phytoplankton to take up,

Abigail conducts a controlled
experiment in So's lab.

She'll measure the time
it takes a scat to travel

from krill bottom to ocean bottom.

[inaudible]

So you can see it coming down there now.

SMITH: The speed that it's
dropping is gonna be really important

for how much of the nutrients

are able to leach out of the fecal pellet.

Mm-hmm. As soon as it drops

out of the upper ocean,
it's sort of exported to depth

where phytoplankton can't access it.

BURNETT [voiceover]: After
over 50 of these experiments,

Abigail found
the sinking rates are variable.

Some scats stay around, others sink fast.

Our pellet was one of the latter.

The bacteria and phytoplankton

would need to act fast
to take up the iron.

But all is not lost,

because even a fast-sinking scat

has a gift for the planet.

It can remove carbon from the atmosphere.

Krill ingest carbon from phytoplankton

and excrete it in their scat.

The sinking scat transports

millions of tons of carbon a year

to the depths.

The Southern Ocean
is critical for controlling

how much CO2 is in the atmosphere.

The scat of this
unassuming little crustacean

may be one reason why.

Right now, below the surface,

hundreds of millions of tons of krill

are pooping out torrents of
iron- and carbon-rich pellets.

That's the real power of poop.

♪

My journey has come full circle,

back to the ancient rain forests
of the Wet Tropics,

home to the southern cassowary.

We want to find out

how important the big bird's scat is

to the future of those forests.

It will require patience.

We must wait for a cassowary
to answer the call of nature.

♪

[birds chittering]

I'm going to perform
a cassowary pooping experiment

with colleague Andrew Dennis.

To stay safe and let the bird
get on with its business,

we'll remain a captive audience
for as long as it takes.

There's a lovely bowl of fruit
there for you to eat. Come on...

BURNETT [voiceover]:
This is just one experiment

Andrew performed for a comprehensive

seed dispersal survey.

[murmuring]

DENNIS [voiceover]: We've
done a large project over six years

looking at the entire process.

We looked at 65 different
vertebrate animal types

and about one-and-a-half thousand plants

that have fleshy fruit

that are moved by those animals.

It became very clear that cassowaries

provided a very unique service

within the rain forest.

BURNETT: We want to find
out how efficient the cassowary is

at dispersing seeds.

To do that, we'll time how long it takes

for a seed to travel from mouth to bottom.

We offer a selection of fruits,

including the cassowary plum
and the blue quandong.

[birds chittering]

♪

BURNETT:
Four, five. DENNIS: Yes.

Eight.

Nine.

A good feeding day. Yeah, yeah.

[birds chittering]

BURNETT: Yep, 14.

DENNIS:
14, yep.

♪

BURNETT [voiceover]: We expect the
digestion process to be relatively swift,

because this giant bird has
a very simple gastric system.

It has short intestines,

a stomach that gently massages
the pulp from the fruit,

and a unique combination of enzymes

that allow it to digest the fruit

while leaving the seed intact.

[plopping]

♪

[birds squawking in distance]

[plopping]

Ooh. Oh, cool.

There's one.

Yep, I got that. Time?

Yep.

It's, uh...

Ten to 10:00.

BURNETT:
Ten to 9:00, I mean. DENNIS: 51.

Yep. All right, well,

looks like Airlie's done his job.

Time to get him back into his pen.

BURNETT:
Mm, looks like...

I'll get these two scats.

Yes, I had 14.

Yep, and I got 18,

so we got 32.

So three-and-a-half hours ago,
that bird ate

73 quandongs.

Often, in three-and-a-half
hours, cassowaries will move

between one and two kilometers.

Mm, so it seems

quite a quick passage rate... So...

...but still, just
the mobility of those birds

means that these seeds
are getting... Can go quite a long way.

...kilometers away
from the parent tree. Yep.

BURNETT: The distance the
cassowary travels is important.

Seeds have a better chance of survival

when they're transported away from

the parent tree.

If the fruits stay where they drop,

they're often eaten by seed predators

or infected by fungi.

Andrew's study found

there are many successful seed dispersers

in these forests,

but no other animal

can transport large seeds great distances.

♪

Thanks to the cassowary,
hundreds of species of plants

in these ancient rain forests
remain diverse and abundant.

This marvelous scat grows forests.

Given the area of habitat
that's available,

the cassowary population is stable,

but threats remain...

like the effects of climate change.

DENNIS:
Cassowaries prefer

lowland coastal rain forests.

There's modeling now that shows

how much of that rain forest
is going to be inundated

by storm surges from cyclones
or just plain sea level rise.

So what we're now expecting
is that cassowaries

will have to start finding new areas

to live and disperse seeds.

The trouble they're facing

is that the lowland areas in Australia

have been fragmented.

A lot of the forest has been
cleared for agriculture,

and cassowaries can't move through.

♪

BURNETT: The only way
cassowaries will have enough habitat

is if we plant corridors of trees

that connect with larger tracts
of inland forest

where they can find food.

[Dennis murmurs]

BURNETT [voiceover]: Now we
are becoming the forest gardeners.

-These are a massive bird shit, aren't they?
-[chuckling]: Yeah.

♪

BURNETT [voiceover]:
Volunteers have raised

over 100,000 trees

from the seeds in cassowary scat

and planted them to
create cassowary corridors.

♪

This seedling came from a cassowary scat.

We've taken their trees.

Now we're trying to give them back,

hopefully in time

to make a difference
to all of our futures.

♪

Scat just keeps on giving.

♪

This is fun science,

but that's not the main reason we do it.

Scats really do make the world go round.

And they unite the world, as well.

They unite us through our,

our natural inquisitiveness

and the sense of wonder
that we have at nature

and the natural processes
that sustain this planet.

♪

[engine starting]