-There's a strange animal living in the creek that runs through our city.

One of the most extraordinary creatures on Earth... the platypus.

For some reason -- it's not really a reason I understand -- it's like I've been granted this window into their world.

Sometimes, I think they live in paradise.

[ Thunder crashes ] Other times, it looks like hell.

Over the next year, I'll try to get to know some individual platypus.

If I can understand their secret world, I might be able to help them.

Sometimes in life, you have those moments.

You realize you just can't keep taking from nature.

It's now time to give something back.

♪♪ ♪♪ ♪♪ ♪♪ -I love living in Hobart.

There's nowhere else in Australia like it.

It's a small city, surrounded by water, nestled in the foothills of a stunning mountain.

And somehow, in spite of itself, it's remained connected to nature.

I think destiny probably drew me to the waterway.

It was a challenging time in my life.

I'd had a cracking headache for over a year.

I didn't feel right.

An escalation of X-rays... scans... ultrasounds... and blood tests followed.

The doctors found numerous lesions in my brain.

At some point, I won't be able to do anything.

[ Heart beating ] It's a feeling that you're receding from your own life.

I go to the rivulet to reconnect with something that I feel I'm losing.

Everyone has tough times in life.

In one of these moments -- it was the middle of summer -- she first appeared.

♪♪ ♪♪ I couldn't believe it the first time that this platypus just zoomed right up to me and put her bill out of the water and started wiggling it, as if she was trying to say something.

The more I saw her, the more she'd zoom up to me.

I named her Zoom.

Hey, Zoom.

Throughout that summer, I'd go down to the waterway, and she'd just be there.

And she would always come up and raise her bill out of the air and wiggle it around.

I'm not sure what she was saying, but I did feel connected to her.

I didn't really understand it, but it felt like a doorway had opened, a magical portal into the world of the platypus.

♪♪ ♪♪ The more I watched Zoom, the more I realized what an incredible animal she is.

She's an aquatic mammal, a bit like an otter, but she lays eggs like a bird.

Platypus are famous for that wonderful bill.

But it's not hard, like a duck's bill.

It's soft and rubbery.

It's extremely sensitive and filled with thousands of electrical receptors.

So when she hunts, she shuts her eyes and ears and her nostrils, using electricity to find her prey.

Her feet have webbing like a frog to propel her through the water.

And she uses her tail, like a beaver, to steer.

When she dives, she can slow her heartbeat right down, holding her breath for up to 10 minutes.

♪♪ ♪♪ Platypus don't have any teeth, but Zoom can grind up her prey between rigid plates in her bill.

The males have spurs on their back legs... that can inject venom into their opponent.

Most people have never even seen a platypus, so it's incredible to think Zoom lives on the edge of the city.

But that also creates problems.

One day, I came across Zoom, and everything changed.

She was tangled in plastic.

[ Camera shutter clicking ] I knew I couldn't help her without adding to her distress.

Luckily, she was able to break free.

She had dodged a bullet.

It was as if the natural world was trying to deliver a message.

"You have to do something to help the platypus."

There was so much rubbish in that part of the waterway.

I realized one person would never change everything.

And I wanted to learn more about the platypus.

I started reaching out to scientists and filmmakers.

-Hello.

Good to see you.

It's been a while.

-How are you?

-Good, good.

My name's Chadden Hunter.

I'm an Australian wildlife biologist.

And I've been fascinated by the platypus for many, many years.

Yeah, I mean, it is a beautiful little section of waterway.

-Gorgeous.

-I first met Pete Walsh a few years ago.

He's almost a local legend around here.

-Whoa.

[ Laughs ] -He's very quietly spoken, has no ego at all.

So, my goal was to find out if Pete's platypus were just random sightings or whether there really was a population on this creek that could sustain itself.

The health of the creek is the critical thing.

I felt like we had about 12 months to work with.

Unless those platypus could reproduce on that waterway, they were really in trouble.

I think, for Pete, his medical diagnosis was a real wake-up call.

It gave him this heightened sense of awareness and, through that, a deeper connection with nature.

-If there's a platy hiding over there somewhere, like deep under the bank, that might just be the tiniest sort of smoke signal.

-Yeah.

-Like, the tiniest thing that wouldn't be there otherwise.

-Yep.

Pete started noticing things that even us wildlife biologists weren't noticing.

-I've loved taking photos my whole life.

[ Camera shutter clicking ] When I'm looking through the camera, everything starts to happen in slow motion.

It's an extension of your body and of yourself.

It focuses your mind on that platypus.

-As researchers, we realized that this waterway was in trouble.

If these platypus were going to survive, we needed to engage the community and really change our ways.

Oh, wow.

This is the outfall from the city tip.

So, in heavy rain, this is full of rubbish.

And, you know, the rubbish gets pounded by the water and forced out of the net.

-Mm.

-And quite often, the net breaks.

I guess it's the short-sightedness of humanity, really, you know, where, "Let's make a tip.

Let's make it in a valley above a city, on top of a waterway, and it'll all be okay."

-Yeah.

-Everything like that.

-Yeah.

-And that.

All the stuff you see in there ends up out here.

Obviously, someone's gonna eat that, whether it's a platypus or fish or whoever.

There's so much of it.

-I know.

It's a miracle anything lives down here.

-Yeah.

Hobart's a fairly average-sized town.

But it's had a lot of heavy industry over the years -- logging and whaling and tanneries.

This one waterway was so important to the history of the town.

Sadly, it became an open sewer.

But if you look close enough and spend enough time, there's surprising life down here.

I think people associate the presence of platypus with pristine environments.

So when I first saw a new platypus in this urban drain, I couldn't believe it.

What was it doing there?

♪♪ ♪♪ It wasn't moving about like Zoom, so we knew it was a different animal.

It looked like a young male.

He's just up there.

His territory seemed to be centered behind the city brewery, in a foamy pool.

[ Whispering ] Try and get some video of him.

It was the way this male Platypus moved -- he never sat still.

I decided to name him Scoot.

Oh.

Oh, dude, you're so close.

He's over there.

[ Laughs ] That's actually pretty cool.

[ Laughs ] Platypus aren't designed for concrete.

You can just see how vulnerable they feel.

They sort of cower as they walk along it.

It's just an area they need to transit.

Males, during the breeding season, are extremely territorial.

Scoot doesn't like anything in his territory.

He even goes after the local ducks.

♪♪ ♪♪ ♪♪ ♪♪ [ Ducks quacking ] ♪♪ ♪♪ Oh!

That's pretty funny.

While we were watching Scoot chase the ducks around, we noticed a second male platypus in this pool.

Scoot might be territorial, but he usually avoids other males.

Venom from this intruder could leave him paralyzed.

The males swim parallel to one another, sizing each other up.

The other male pinned Scoot under a metal ladder and seemed to ram his spur in.

Perhaps there's not enough food in this territory for two males.

I wanted to learn more about what platypus eat, so I got in touch with an expert who might be able to help.

Today's all about learning more about the health of the Hobart rivulet, and one great way to do that is by counting water bugs, because as well as being the platypus' main food source, they're also a really accurate indicator of waterway health.

We're really lucky to have John here help us today.

He is the water-bug wizard.

He runs the national water-bug database.

-Oh, how could you say no if you were a platypus?

Just got one chomp, and, you know, that's brekky.

♪♪ ♪♪ -Water bugs themselves are fascinating.

[ Crunch ] There's a whole miniature world down there.

Some build their home from sand grains.

Some build their homes from sticks.

Zoom and Scoot's survival depends on them.

Bizarrely, you have this little furry creature who is the apex predator of the waterway.

The platypus is like the shark.

They can detect electricity given off by the tiniest muscle movement, like the flick of a water bug's tail.

But I think water bugs know they're in trouble when there's a platypus in the area.

When you see underwater footage of a platypus foraging, what you do see is water bugs just bailing in every direction, trying to escape it.

-There's lots in the main river up there, and there's not so much here.

It's that simple.

And I guess it's just going to get worse as we go in towards town.

It's going to get less and less bugs, less and less food.

Alright, go, go, go.

Give me some slime.

-Nice.

-Alrighty.

How's that?

-That's heaps of slime.

The nutrients and the sunlight and everything means that all we've got here really is lots and lots of green slime.

From the water testing I've done here with John this afternoon, you know, we found one water bug, you know, in total.

The quality of the waterway degrades the further you travel from the mountain down towards the city.

-It was clear that Scoot's home range was a hard place for a platypus to live.

Further upstream, it was like platypus paradise.

I love autumn in Tasmania.

[ Bird chirping ] There's a lot of animal activity.

♪♪ ♪♪ ♪♪ I hadn't seen Zoom in a while, so I headed upriver.

♪♪ ♪♪ ♪♪ The moment Zoom leaves the water directly in front of you, your heartbeat just goes up straightaway.

You're trying to stay calm.

It's like, "What is she going to do?

Is she just coming out for a look?"

But then, you know, she keeps getting closer and closer and closer, till she's right beside you.

And then does a poo.

It's pretty awesome.

It's kind of weird and awesome at the same time.

Did you get that?

After spending so many hours with Zoom, I'm guessing that she's beginning to trust me.

I wanted so desperately to remain in that platypus bubble.

But sometimes, there are startling reminders that the city is never far away.

♪♪ ♪♪ So, up until a few days ago, this was a beautiful pond, full of leaf litter and branches, somewhere the platypus would often come and rest and forage before they headed upstream.

And now, basically, it's a massive gravel pit.

But to actually see it in the waterway, it's a catastrophic amount of gravel.

♪♪ ♪♪ It's difficult to understand.

You know, it's so distressing.

Really, there's no words for it.

Just when you think nothing else can happen... [ Chainsaws whirring ] ...we hear chainsaws in the distance.

Massive willow trees were being chopped down.

They're not native trees, so I understand why they need to be removed.

But the river was looking like a war zone.

♪♪ ♪♪ [ Wind howling ] [ Thunder rumbling ] ♪♪ [ Thunder crashing ] ♪♪ ♪♪ -Another thing that happens to this river in autumn is, we get heavy rain, causing severe flash floods.

They wash logs down and they create dams, debris gets built up.

All of a sudden, the platypus will wake up with a very, very different habitat around them.

The water level can rise 2 meters overnight, and you realize what a struggle this is for the platypus.

♪♪ [ Thunder crashes ] ♪♪ ♪♪ ♪♪ ♪♪ All this floodwater rushes down stormwater drains and under the city.

But for us, the single most dramatic thing about this flood is that Zoom went missing.

Zoom might've been washed underneath the city, maybe out into the harbor, we don't know, but I think Pete just couldn't let this go, and he had to go looking for her.

This is really where our creek changes personalities from heaven to hell.

This is like entering the underworld.

♪♪ -I'm looking for two things.

I'm looking for places where platypus might shelter in an emergency.

And the second thing I'm looking for is any sign of Platypus scats just by the waterway.

For Platypus, there's very little food and there's very few places to shelter.

It's not really where they want to be.

♪♪ ♪♪ Amongst all of these plaster baby heads, it's almost like a tombstone or memorial to the platypus, which is kind of cool and kind of bizarre at the same time.

I'm not sure exactly what the intention was of the artist.

And this is an example of how great our disconnect is with nature, where we turn what was a beautiful waterway into a drain, just out of our own convenience, with no regard to anything that was, you know, whether that was platypus or just whatever the habitat that would've been here.

This really is the graveyard of the Hobart Rivulet.

We're only really here to look for Zoom.

She could've been washed out.

She could've drowned.

She could be injured somewhere.

You know, that's just the reality of this situation.

It was clear the flood threw a lot more than rubbish into the mix.

-He's coming towards the hole.

-The first platypus I saw after the flood wasn't Zoom.

-Oh, you got him?

-It was a female, and she was tangled in twine.

Hey, buddy, we got you safe.

-Ooh, there's a bit of blood.

-Oh, it's cut right in, hasn't it?

It's cut into it.

Once we'd caught the platypus and started removing the twine, you could really see the depth of the injuries.

-Can we see the muscle?

The red?

-Yeah.

-Yeah, we can.

-Yes.

-It really took a community to catch one animal.

The care was incredible there.

Took the platypus in.

They took X-rays and checked her over, gave her a physical, cleaned out the wounds, put in fluids, painkillers, antibiotics, and then put her to bed.

-Yeah, we'll start sort of putting some stitches in this and get it closed up.

-Over a couple of hours, they stitched up the two wounds.

[ Laughs ] It really did take the animal quite a while to wake up.

I think there were a couple of concerned looks.

There's a yawn.

-Did you get that?

-I got that.

-Finally, her eyes opened, and she started wriggling around.

You know, that was a relief.

Come on, bubba.

Wake on up, please.

-A bit woozy.

-So, we're down here at the rivulet to collect some goodies to make the platypus feel like it's at home.

We're getting some fine gravel, some pebbles, leaf litter.

Hopefully there'll be some water bugs amongst all of that, as well.

Alright.

-It was a phenomenal thing to see how much passion was burning inside him at this stage to really try and help the platypus in a much more proactive way.

-Oh, look at that.

So, what I'm doing with my hand the platypus does with its rubbery bill, except after just a couple of minutes, my hand is getting ground down.

Yeah, I think that's probably enough.

I might just start loading this stuff in the car so we can get this stuff to the platypus.

♪♪ ♪♪ -It's just such a lovely thing to come in here and find her curled up asleep.

-I'm surprised at how kind of slow her breathing is and deep.

-It's kind of -- -Yeah.

-Yeah.

-She's had a good 10 hours' sleep, so it'll be safe to let her feed now.

-Yep.

Okay.

♪♪ ♪♪ -Straightaway, there's that behavior of nosing around.

She's had a big operation, and even we wouldn't eat well for the next couple of days.

The main thing is to just offer her as much as she'll take and give her as much time as she needs to feed.

-Yeah.

That was amazing.

Yeah.

That's been a beautiful thing, you know, this morning.

♪♪ -Come on, guys.

Hey.

Look at that, little plat.

You know where you are.

Good to be back, I reckon.

We'd released the platypus into a downstream flow, and while we were talking, I had half an eye on her, and she sort of kept popping in and out of the waterway, which was really peculiar.

And then she did seem to disappear.

I guess that was goodbye.

Standing around, sort of being like a successful release.

Yeah, she's really getting in and out a lot.

And then her little head popped over the concrete.

And she hobbled past us, clearly not able to walk properly.

So we followed her.

Why's she doing that, mate?

That's a really unusual behavior.

She doesn't want to be in there.

And every time she'd touch the water, it was almost like she was repelled by it.

Whether that was pain or the cold or not being able to swim.

Why is she walking so broken?

Is it actually injured, mate, or... Clearly, she was much worse than all of us thought.

-I think probably the best thing for her at this point would be to take her back into care again, as hard as that is.

-Luke took the platypus back to Bonorong that night and actually spent a bit of time checking her over.

And he noticed, like, she'd really lost control of that right claw, like she couldn't knuckle down.

[ Dog whimpers ] And then, the next day, Luke messaged me letting me know that she'd died.

I think even just the response has been sort of really beautiful, you know, that people were touched... you know, by it.

Sorry.

It's a waste of an amazing life.

It's like, you know, this can't be for nothing.

Yeah, I think we have to honor her life and the lives of all of the other animals that have died in that way and do something.

♪♪ [ Wind howling ] It was a tough winter.

When we lost that one platypus, it was a real turning point for me.

-...and these incredible animals that are in the waterway that have somehow... -I'm normally a shy guy, but I realized I needed to step out of my comfort zone.

So, I'd like to introduce Pete Walsh for our next section of the evening.

So thanks, Pete.

[ Applause ] -I started to talk to the public about the challenges platypus face in our city.

So, are we the greatest enemy of the platypus?

And if we are, are we okay with that being our story?

Sadly, Australia's treatment of the natural world continues to make news for all the wrong reasons.

The community reacted in a way I'd never seen before.

More and more people wanted to help save the platypus.

To raise more awareness, we managed to get a big mural of Zoom painted on a coffee-shop wall.

I even started getting calls about pollution in the waterway.

I mean, that spill, at a bad time of the year, in a bad spot.

That's pretty awful, whatever that is.

With this kind of pollution and rubbish, the best way to understand it is not just see it, but to feel it, put your hands in it.

That's what the animals are doing.

You know, that's what we're forcing them to do.

If no one reports a spill, from the point of view of the people who manage the waterway, the spill never happened.

Super-important -- if you see something bad happening, you know, let somebody know so there's a written record of it.

It was clear these urban platypus were living right on the edge.

It was such a relief to see Scoot again.

But his behavior seemed to be changing.

He seemed more energetic... more adventurous.

We watched him climb up and out of his cement world.

There must be something drawing him up the waterway.

He's on, like, a supercharged patrol.

♪♪ ♪♪ When Scoot travels up a concrete slab in the water, he creates this amazing effect, like a giant bow wave.

He's like a dinosaur crossed with a Formula 1 car.

It's just this beautiful fan of water.

Scoot was clearly on a mission.

During the breeding season, male platypus virtually give up on feeding.

They can travel miles out of their home range.

♪♪ ♪♪ It's amazing to see an animal that's built for swimming actually try to climb a waterfall.

Scoot tucks away the webbing on his feet and uses his claws to climb up rocks.

It doesn't always go to plan.

♪♪ ♪♪ ♪♪ -There we go.

Right on the edge.

-It was a relief to see Scoot finally make it into the pristine part of the waterway, you know, above the suburbs, above the city.

The only problem was that Scoot had wandered into the territory of a much bigger male.

♪♪ ♪♪ The males twist and turn to avoid each other's weaponry.

♪♪ ♪♪ ♪♪ Scoot managed to wedge his spur into the other male's rump.

♪♪ ♪♪ ♪♪ ♪♪ This was the first fight we'd seen Scoot win.

I was following Scoot upriver, and we came across a female grooming.

She was lying back, scratching, releasing her scent into the water.

And then I realized... it was Zoom.

All that time she was missing, but here she was upriver.

Scoot had been following the smell of a female he'd never met.

And he'd taken me along as his wingman.

♪♪ ♪♪ ♪♪ Mating doesn't happen immediately.

There's a fair bit of foreplay for platypus.

The females are really testing the males.

Scoot might've been from the wrong side of the tracks, but it felt like Zoom had finally met a male that she was happy to mate with.

♪♪ ♪♪ They put their bill on each other's tail, like they're in a trance.

I call it the platypus love doughnut.

♪♪ ♪♪ It's now the height of spring, the peak of the breeding season.

It was soon after mating that Zoom seemed to go on her own mission.

She's trying to find a burrow that is high enough to be above the flood levels.

She might dig up to 10 meters into the dirt to find a safe place to lay her eggs.

♪♪ ♪♪ She has to get it exactly right for the young to survive.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ This is the first time I've discovered a nesting burrow.

The nest building is like a miracle of nature, in my opinion.

I didn't know that Zoom could curl up her tail like that.

Her grip needs to be strong to hold on to that vegetation.

♪♪ ♪♪ To see Zoom come out of the water with her full load of nesting materials and then disappear into a tiny burrow, it's incredible.

How does all that stuff even fit in the burrow?

The platypus can hardly fit through that hole.

Well, she's constructing that nest in 100% darkness.

♪♪ ♪♪ We were super-fortunate to find Zoom's burrow, so my strategy is to place a number of trail cameras around that burrow, out of her way, and just leave them running.

When they see something happen, they'll send me an alert.

So many people had heard of Zoom by now.

This one platypus was really inspiring the whole community.

Locals were now coming out to help protect the platypus' home.

-It's just really inspiring to see you all out here today to help regenerate this area.

-Seeing the community come together to do the replanting along the rivulet, you know, was a beautiful thing.

It takes a community to care.

-If you want to look after native wildlife, plant Tasmanian native plants.

-One person can never do it all.

And, also, one person won't be around forever.

That is the critical thing -- that the community takes ownership of their waterway and caring for their waterway.

If the work that I've done with platypus has sparked something in people and driven them to act, I think that's a great thing.

When I woke up one morning and looked at my phone, I saw two or three alerts from the trail cameras around that nesting burrow.

It was like, "Something's gone down."

Mm-hmm.

Alright.

The moment of truth.

To a see a youngster come out of Zoom's burrow was such a magical feeling.

[ Laughs ] And the next day, I'd come down to the pond here, and I've just been walking around for a few minutes looking for him.

There's me walking around, looking for him everywhere, but the whole time, he'd been behind me.

Young platypus are so vulnerable... and so clumsy.

But Zoom's work as a mother is done.

Now her baby's out of the burrow, he'll have to find his own way in the world.

Zoom's youngster gives me hope that platypus can continue living in this city.

You know the odds are stacked up against a young platypus surviving, really.

Like, he has to find his home in the platypus world.

But you really want to do whatever you can... to give him the best chance of surviving.

♪♪ ♪♪ It's been a beautiful journey.

If I died tomorrow, I'd be pretty sweet, you know?

♪♪ I think the rivulet's come a long way from what it once was.

But if we were to come back in, say, five years' time, hopefully we'd see a much cleaner waterway.

So, when you look back at your own life... is your legacy that you lived and enjoyed nature... or lived and cared for nature?

♪♪ ♪♪ ♪♪ I thought I was going there to look after nature, but, really, it was nature looking after me.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this "Nature" program, visit pbs.org.