Original subtitles

Rarely seen, they have a near-mythical reputation.

They have boundless energy and are able to dive deep...

..and catch the fastest of prey.

Otters.

My name is Charlie Hamilton James,

wildlife cameraman and otter fanatic.

I've been observing and filming these shy but relentless animals

for the last 25 years.

For me, otters are the ultimate predator,

perfectly bridging the gap between two worlds -

one dry, one wet.

Yet across the planet,

their populations have hung in the balance.

I've done what I can for their conservation.

However, many remain in danger.

But otters are fighters...

..supercharged with a huge amount of spirit and determination.

And now, with the help of three orphaned cubs...

..some ground-breaking experiments...

It's done it, that was it!

..and some incredible wild encounters...

..I'm going to reveal their survival secrets

and just why I think otters are such a special group of animals.

I spent my life searching for

glimpses of these rare and elusive creatures.

They're nervous

and fearful of humans.

But there's one place where they're bolder than most -

Florida.

Here, clear, spring-fed rivers provide the ideal opportunity

to film otters moving and hunting underwater.

Something few have ever done.

If I succeed, it'll be the perfect way

to begin a journey into their seldom-seen world.

They know I'm here.

They're far too inquisitive not to have noticed.

But they don't seem to mind.

There are more otters here than anywhere I've ever been.

But, typically, they don't keep still for long.

North American river otters can cover over 40km a day...

..and swim for 400m without coming up for air.

If you're going to observe otters in the wild, you need patience...

..and a bit of luck.

I spot a telltale sign.

A trail of bubbles.

Absorbed by foraging...

..this is my chance to get close.

I want to see how it's hunting.

Something I've never achieved before.

But I know just a flick of its tail and it could be off in a flash.

He's so focused.

I just need to hold my nerve.

In 25 years of watching otters, I've just got these little glimpses

occasionally of them underwater,

and here, in a single morning,

I've seen more otters underwater than in that whole 25 years.

But what's been really interesting is actually looking

at how they're hunting.

It made me watch him and understand and look at the way he was doing

stuff, the way he was swimming and fishing,

in a completely different way.

In this one incredible experience,

a completely wild otter allowed me to come here,

hang out and watch him fish underwater.

There's an otter right there.

HE CHORTLES

This place is so amazing.

There's just otters everywhere. It is otter heaven.

I need to go get back in the water.

It's all very well sitting here talking to the camera

but I'd rather be swimming with an otter.

The experience has reminded me why

otters have captivated me for so long.

They are incredible predators.

Energetic,

inquisitive

and versatile -

..traits they share with their extended family.

The mustelids.

An ancient and diverse group of carnivores

that includes weasels,

stoats, badgers and martens.

Otters can be found on nearly every continent,

from the Arctic Circle

to the swamps of Africa.

And from desert oases to the tempestuous seas of Patagonia.

But there are some things that unite all otter species.

They have long, highly flexible bodies...

..a powerful tail

and webbed feet.

Some can dive to 100 metres...

and hold their breath for over four minutes.

But despite their amazing physical abilities,

all over the world, otter numbers have been in decline.

BARKING

They've been hunted for sport

and for their fur.

They've lost their food to human greed...

..and have seen their habitat poisoned and ruined.

But given the chance, otters are survivors

enduring against all odds.

It's one of the reasons I've always done what I can,

caring for otters in need.

I've even welcomed them into my family.

Otter!

Otter!

Honey, a Eurasian otter

too dependent on humans to be released...

..held a special place in my heart.

And the time I spent with her only made by love for otters stronger.

To help me reveal what I believe sets otters apart,

I'm going to follow three male orphan river otters

on their own story of survival.

As they grow they'll be taught

the vital skills they'll need for a life back in the wild.

After being abandoned by their mothers, the orphans were brought

to Wild Instincts wildlife rehab centre.

On arrival they were weak, defenceless

and would not have survived the night.

Attempting to mirror their wild diet,

centre manager Mark is giving them chopped fish and milk formula.

But he has concerns about the weakest orphan.

He came to us with a kind of a bad leg.

He injured the joint on his right rear leg,

so we're not quite sure whether it's going to heal enough for him

to be released or not and he also did a slight injury to the joint

right in here on this leg also

and even the good leg is not necessarily a good leg.

So what we're going to do is try to find a zoo for him

if he's not able to be released back into the wild,

and if we're unable to find a zoo then he

may have to be euthanized if we can't find a place for him to go.

To keep any attachment to a minimum,

it's Mark's policy not to name any of the animals in his care.

Now eight weeks old,

the cubs need to tackle an essential survival skill -

..learning to swim.

Curiously, baby otters don't really like water.

So Mark needs to teach them their most important life lesson -

that water isn't something to be afraid of.

Just like their mother would in the wild,

Mark makes soothing calls to reassure them.

HE WARBLES SOFTLY

OTTERS CHIRP IN RESPONSE

Each time they try to get out,

Mark plops them back in.

But their swimming lessons don't last too long.

That's because of another surprising quirk of otter biology.

Their coat doesn't become waterproof until they are 12 weeks old.

Until then, being wet could lead to hypothermia.

So surrogate mum Mark does what he can to help out.

Normally in the wild what they would be doing is rolling around in

the grass and the dirt

to get some of the water off themselves,

so we can use the towels to help us out a little bit.

Wild otter cubs face exactly the same issue,

so the adults only take them for short dips

to stop them getting cold and waterlogged.

It's exactly what I saw with a family

of giant river otters in the Amazon.

Wow, look at that. Tiny!

That is really young. That can't be more than six weeks old.

He's got another one.

Giant river otters are highly social

and with such young pups in the water, the whole family helps out.

They're too small to start swimming properly.

It's just a taster session

under the watchful eyes of their parents and siblings.

Eventually, they'll become accomplished enough in the water

to catch fast, wild prey.

Back in Wisconsin, otter foster parent Mark is about to start

teaching the orphans how to fish.

But first the orphan with the bad leg needs a little extra help.

So Mark has designed a swimming aid

and is giving him a course of aquatherapy.

OTTER CHIRRUPS FRANTICALLY

So it looks like the little apparatus we have put on there seems

to be accomplishing what we wanted it to do. It keeps him afloat

and he's using his rear legs much better than he was before without it

so hopefully this will be some good therapy and get him on the path

to being what he needs to be.

He's obviously a little fighter.

As I arrive,

Mark's just about to give them live fish for the first time.

MARK WARBLES

Oh, my God.

Mark adds some minnows to the paddling pool

and hopes that hunting is more instinctive than swimming.

How cute is that?

Go on, then.

Yesterday we were doing a bit of diving and swimming around

and now there'll be something to swim and dive around for

so we'll see if they have any luck chasing around.

This one's completely at home. It's just chased a fish.

Exactly, exactly.

Straightaway. And that's just in a few days.

It's gone from nothing to chasing fish underwater. Right.

He's got a fish.

He's got one.

He let it go.

He's got it, he's got it.

That's his first fish.

Isn't that amazing?

Yesterday he wasn't even putting his head underwater

and today he caught his first little fish.

That is amazing, isn't it? He's just rolling around playing with it.

That's a great moment for them. Wow.

Fishing, for the orphans, appears to be innate.

It's a good sign.

But it's something they'll need to hone.

Do you know what?

To me, there is nothing in the world that compares to otters.

I could sit here all day every day and do nothing else for the rest of

my life, just hang with otters.

That's when I'm at my happiest.

'As the orphans get bigger,

'their swimming abilities will develop, too,

'until they're as agile in the water as the fish they hunt.'

But otters aren't just masters of the water.

They spend up to 80% of their lives on land.

Their ability to lead this semiaquatic double life is what allows them

to cope with diverse habitats and prey.

The key to this lies in their physiology,

and back in the UK,

I've got a furry friend to help reveal the secrets of their success.

This is Rudy. He's an Asian small-clawed otter...

..or short-clawed otter, because he's got tiny little claws.

And the aim is to get a really decent look at Rudy

and how his body works, how his physiology works,

how he turns from an animal that can run around on the land

to an animal that's as fast as a fish in water,

and it gives me an excuse to just hang out with an otter.

I think you need to go and see the dentist, Rudy.

This camera is going to do some nice slow motion shots

and I can track along with the otter and then we can, you know,

we can get a good look at how it's running.

And Rod here is going to film Rudy swimming in close-up

and particularly in slow motion.

The thing I've always wondered, watching them and filming them,

is how do they go from land to water and be so brilliant at both?

And I think the reason I like what we're doing now is because we're

going to get a really detailed look at that and try to get

some understanding of how they manage to do that

because very few animals can just flip between two worlds like that.

Otters do it brilliantly.

When we slow the action right down...

..we can see exactly what's going on.

Otter spines are highly flexible...

..allowing Rudy to rotate his hips...

..swing his leg forward and plant his feet securely on the floor...

..and use his powerful tail for balance.

And unlike most land-based carnivores,

his front feet are well-developed

with long, dextrous fingers for foraging and handling prey.

By bending their highly flexible spines,

otters are able to decrease the distance

between the shoulder and hip by over 20%, allowing them to bound,

running up to 18mph.

But the adaptations that allows them to live a semiaquatic life

become clearer as Rudy enters the water.

A substance 800 times denser than air.

As he puts his head into the water,

his vision becomes blurry, just like it does for us.

But an almost magical adaptation allows him to correct this,

like an in-built pair of swimming goggles.

At first, the density of the water stops light rays

being brought into sharp focus on his retina.

But Rudy has highly specialised muscles in his iris

that squeeze the lens so that its face bulges forward.

This refocuses the light rays onto the back of his eye...

..giving him sharp underwater vision.

Now that he can see clearly,

he enters the water fully and his next trick is revealed.

Pushing his broad head forward and rotating his hips,

he is able to straighten his body like a torpedo.

Tucking his legs in, he reduces the water's drag...

..only untucking them when he wants a burst of speed.

Next he uses his flexible spine in combination with his tail and

webbed rear feet to turn and twist in the water.

The agility of otters blows me away.

Rudy has mastered the skills for a semiaquatic life

but our orphans in Wisconsin are just learning how to make

the most of their two worlds.

They're now 12 weeks of age,

old enough to move outside into an enclosure with permanent water...

..where Mark is going to introduce them

to some different prey.

So today we're going to do some freshwater clams, some crayfish,

then we're also going to do some frogs.

So we're going to start off by introducing the clams first and,

since they really don't know what these things are,

I'm going to cut them open for them,

so I'm going to give each one a clam

and then what we'll do is throw some in the pond,

let them kind of figure it out,

because they'll get the taste for it

and realise that, hey, this is something I can eat.

A wild otter's diet is broad.

They catch and eat everything from snails to octopus.

And their inquisitive nature has led

to one species evolving an incredible talent -

the use of tools.

Sea otters feed on crustaceans and molluscs

but their hard exoskeleton is notoriously tricky to get into.

So each otter has preferred tools for accessing its favourite foods.

Be it a rock for opening clams...

..the bow of an expensive boat for oysters...

..or an empty beer bottle for barnacles.

By focusing on particular prey,

sea otters have a balancing effect on the ecosystem...

..helping to keep it healthy.

Otters seem to have a relentless curiosity.

To me it's an indicator of just how intelligent they are.

An endearing trait, and one that often results in play.

Essential for all otters as they grow and develop...

..teaching them crucial life lessons.

And it's exactly what I had to do with Honey...

..the otter I reared at home.

HE GIGGLES

But play for her wasn't always much fun for me.

Ow! That's my skull! Ah, get off!

This whole biting my skull thing, Honey, I'm not a fan.

In social species, the bonds that play solidifies

makes otter families a formidable force.

Especially important for giant river otters,

who regularly face deadly predators.

With vulnerable young cubs,

this family discovered a large black caiman in their territory.

Identifying it as a threat, they work together,

systematically attacking it.

For three hours, the otters pinned it down,

taking it in turns to attack its underside and head.

Eventually, the enormous size and power of the caiman was no match

for the family, whose bonds are so strong that they would risk dying for each other.

For the orphans in Wisconsin,

their best chance of a future in the wild

will come from staying together.

Now they can get a lot more exercise,

start doing what they need to do and start being a lot less dependent on

us, and we can start cutting off our human contact with them so they can

learn to be otters and not rely on humans too much any more.

They now have their most important piece of survival equipment -

..a warm and completely waterproof coat.

Fur is an otter's secret weapon.

They all rely on it to keep warm.

But to understand its special qualities,

we need to look at sea otters once again.

They have the densest and most luxurious fur of any animal.

It's such high quality

that trappers historically measured all other fur against it.

It's the main reason sea otters

have been persecuted throughout their range.

Their fur has nearly one million hairs per square inch.

To properly appreciate the world's furriest animal,

I've come to Monterey Bay Aquarium in California

whose sea otter reintroduction programme has been

instrumental in the recovery of the population.

Beautiful. 'The aquarium's head vet, Dr Mike Murray, has anaesthetised

'a female otter for a checkup,

'giving me a chance to take a close look.'

Look at the size of that. That's enormous!

She actually feels really warm.

That really, really thick fur they have is designed to conserve heat

and she really doesn't, without cold water, have an opportunity to dump heat.

Her coat is so effective

that Dr Mike has to put bags of ice on her flippers

to stop her overheating.

This is the most beautiful, silky, soft fur you can imagine.

On the outside it's much thicker

but when you get down deep inside it's just silk-smooth.

You can just make out the sort of pale, white skin underneath.

It's amazing how wet it is on the outside

and then you peel it back and it's completely dry on the inside.

That is beautiful.

It's so soft you can barely feel it. It's weird.

And if you look at the undercoat,

they've got these long guard hairs, but down deep,

you look at those microscopically

and they've got all these little scales that stick off the shaft of the fur

and what the otter does when it grooms is,

it just conditions the fur to get those things to lock together

so that it becomes impenetrable to water, essentially,

and they can get air in those spaces,

very similar to a down jacket or down vest that we might be wearing.

Looking at the undercoat in microscopic detail

shows these scales lining the shaft of each hair.

Grooming increases the volume of air trapped in this layer...

..maximising its insulation potential.

And in the freezing waters of Alaska,

survival relies on good insulation.

This mother is fluffing up her baby's coat.

By blowing into its fur

she's filling it with air to keep him warm.

The more trapped air, the warmer it is.

But for it to be effective, it needs to be kept in top condition...

..which means otters spend hours each day grooming...

..using their flexible spine to reach those hard-to-get spots.

We can see just how effective their coat is with the help of some technology.

This is a thermal camera, so what it does,

instead of looking at a straight image of something

as we would normally look at through a camera,

this looks at the heat signature of everything, so it can

tell the difference between hot and cold and it shines up here.

You know, the yellow bits are warmer, the purple bits are colder.

It's going to be really interesting

looking at the sea otter with this camera,

because it'll show me which parts of the sea otter are retaining heat

and which parts are giving off heat.

OK, so she's right underneath me now.

This is going to be a really nice shot.

There she is.

So you can see, looking at that,

the bits that are really shining up yellow

are her eyes and her mouth and nose

and just a few bits on the side of her head,

so those are the main bits that are losing heat. That's amazing.

What's interesting is that the water temperature here's around

7 Celsius, and her body temperature is around 37 Celsius.

So we're actually looking at a 30-degree difference between

the water temperature and her body,

but we're not seeing it on the picture.

Her body is almost the same colour as the water.

So what that means is,

that thick fur that the otter's got

is so good at insulating the otter

that very little heat is coming off it,

almost no difference between the water temperature

and the temperature of the otter on the outside of the otter

because all the heat, that 37 degrees, is being kept inside.

This highly specialised coat is one of the reasons otters

are more capable on land than other semiaquatic mammals...

..like sea lions.

SEA LIONS HONK

One of the differences between these Californian sea lions and otters is

not just the fact that they've given up their legs for flippers...

..but they're fat, great, big fat, lummoxing things.

They're useless on land.

This is pretty much the extent of what they can do on land,

which is climb ashore and go to sleep.

And otters? Otters can be really successful predators on land

and the reason is, they don't have any blubber.

These guys use blubber to keep themselves warm in the sea.

Otters use fur, and one inch of fur

is the equivalent, in insulating terms, of four inches of blubber.

The otter's fur coat not only provides them

with superb insulation in the water,

it also allows them to have incredible agility on land...

..something the orphans in Wisconsin will need to take advantage of.

At five months old, their confidence is growing.

And their curious, intelligent nature is starting to shine through.

So now what we can do is...

So they know you're going to feed them, don't they?

We can toss in a fish or two.

And normally, as soon as you get a couple in there...

Look at that, he's straight on it. Wow.

That was so fast.

It's so lovely to come back here and see how they've developed.

I mean, they're just huge now, compared to what they were.

They were tiny little, helpless, useless otters

and, back then, we gave them their first fish

and thought, "Wow, they can catch a fish, isn't that wonderful?"

Now you watch them and they're just pros now.

Exactly.

If you look,

now you have a hard time telling who

the guy with the bum leg was.

He doesn't show any sign of any problems any more.

He's just as good as the other ones at catching fish

and just as fast and agile as everybody else.

I'm relieved that the injury to his back leg has recovered so well.

It's testament to Mark's skills as a substitute mother.

He's taken the camera out now. Look at that.

The camera is going in.

How can we get this in?

They will figure it out.

Oh, he's reframed it for us!

They're just into everything, aren't they?

Yeah. And that's otters for you, isn't it?

Exactly. Crazy into everything. Everything.

Just like this, with the block.

You worry about them tipping the block over on themselves, and, er...

Aww!

There we go. It's sunk.

THEY LAUGH

They're now swimming around, looking at themselves underwater in it.

They're doing otter selfies.

'I just love their energy and determination.'

These guys are clearly well on the way to having the skills

they'll need to survive in the wild, and that time is fast approaching.

Their release into Wisconsin's northern woods is only a month away.

They've got each other. They do.

I mean, one otter, you know, that's tricky. Three otters together?

They can learn from each other, they are safer in numbers. Exactly.

So they should do pretty well. They can certainly fish.

So I think we'll go on out of here.

they're starting to get a little bit too used to us.

We're trying to keep our contact to a minimum

so let's get on out of here.

Cheers, guys.

Mark's intentionally keeping contact with the orphans to a minimum.

They need to be as independent as possible ahead of their release.

Although they're doing well,

catching fast, wild fish in a big open lake or flowing river

will present them with an enormous challenge.

They'll need to bring all their knowledge and skills together.

To reveal how otters do this, I'm heading to Oakland Zoo in California

where I hope to film a hunt in super-slow motion.

Here, they enrich the lives of the otters by feeding them live prey -

goldfish.

Helping me dissect the action is biology professor Lei Lani Stelle.

Check this out, Lei Lani. What this will allow us to do,

while the otter's swimming, I can track along with it and it shoots in

really decent slow motion.

We can basically slow things down ten times.

Wow, that'll give us amazing detail on what they're doing right at the

moment when they see their food and are able to catch it.

He's going for it. Wow! That was nice, wasn't it?

Look at them chasing it together.

He's having trouble getting that one!

Look at that!

Got it.

Awesome. OK, let's have a look, see what we've got.

Where's the play button?

That's so cool to see it in slow motion,

so you can see all of the details of the moving.

When we were watching it, it was so fast it was hard to see.

It's incredibly agile, isn't it?

Yeah, you can see him doing a really quick turn

and you can definitely see how flexible his spine is.

So it really is, I guess, the spine doing a load of work

and then when he needs to get the fish, the back legs seem to come out.

And that's how, I guess, how they get that turn of speed.

The flexible spine combined with its tail and webbed hind feet

allow the otter supreme agility and speed in the water.

In the final approach, it uses its underwater eyesight

to place the fish right in front of its head.

That's right on the tail of the fish, isn't it?

He kind of nudged it with his nose first. Yeah.

It definitely seems like we're noticing that they're feeling the

fish more than anything,

so it may be that they're detecting it with

their whiskers first and since that has a hard-wire

from the whiskers right to the jaw,

they can just bite it with instinct

without having to take that time for the brain to process the signal.

So they're not, you know, they're not feeling it

and thinking, "Is that to my left? Is that to my right?"

Right. It's like an instant...like us seeing or hearing.

Yeah. Exactly, there's no delay. And that would explain how they're

able to pick up on the fish so quickly.

Because I would have trouble seeing the fish and they would already grab it.

Right. And it is incredibly fast, isn't it?

As soon as the prey touches the whiskers,

an incredible nervous reaction is triggered.

The signal fired to the brain is immediately turned into a command,

stimulating the jaw to grab.

Cutting out any decision-making delay.

And it all happens in a fraction of a second.

'But I've spotted something else intriguing in the footage.'

That otter's nosing that fish and sniffing the fish, right?

And if you look, when it first comes up to it, it puts bubbles out.

It's got loads of bubbles around its mouth. Right.

Because I'm convinced otters can smell underwater.

So do you think the bubbles are going back into the nose or into the mouth?

I think they're going into both. Interesting.

It's not improbable because a lot of animals can smell

underwater, right? And it's just a chemical cue

and as long as it's concentrated, so it's really right close to them,

it makes sense that they would still be able to smell it underwater.

So other animals that can smell underwater,

do they just sniff in water or do they use bubbles in this way?

You know, to be honest, I don't think anyone knows.

It's thrilling to think that otters' ability to smell underwater

could in fact be an undiscovered survival skill.

I've long thought otters must have this secret ability, and seeing

this has inspired me to put my theory to the test.

I'm hoping Rudy might be able to help me once again.

So really the only definitive way of proving that otters can smell

underwater is to do an experiment,

so we're going to get some fake fish and some real fish

and we're going to try and film Rudy telling the difference

between the fake fish and real fish.

So what we've got here is a fake piece of plastic trout.

We're going to put that on here

and we present Rudy with

two identical-looking pieces of fish...

..to see if he can tell the difference.

So we're going to put this experimental block here...

..underwater.

'This relies on Rudy investigating each piece underwater.

'Deciding which one is food and then eating it.

'And Rod and I capturing the whole thing on camera in slow motion.'

No interest in the fake one.

Absolutely none.

Well, come on, Rudy, do it.

It's so fast and it's so subtle,

that it's very difficult to work out exactly what's going on.

'My camera simply isn't capable of slowing it down enough to see the finer details.

'But Rod's camera captures the action 40 times slower than real life.'

Right, Rod, did you get it?

Possibly. Really?

Yeah. It's so quick and obviously we're slowing it down 40 times,

so until we actually see it...

So that... God, that is a close shot. There's his head.

That's a bubble coming out of his mouth, isn't it?

Oh, he's sucked it back in.

It's done it. No way.

That was it. Fantastic.

That's amazing.

A bubble came out of his mouth

and just as he was lifting his head, he sucked it right back in again.

It wasn't his nose, but it was his mouth.

He draws it back in, tasting the fish.

That's amazing, because you can actually see it happening perfectly.

'Rudy actively pushes a bubble onto the surface of the fish...

'..picking up scent molecules before he sucks it back in...

'..obtaining enough information to determine whether it's something he wants to eat.

'This footage helps me understand how otters might find food in

'dark, murky waters where they can't rely on their underwater eyesight.

'They sniff it out.

'It's amazing to think that an animal we are so familiar with...

'..may still hold secrets from us.'

And good to think that the orphans may have this ability too.

The cubs are six months old now and autumn is coming.

It's time for their release.

With his parenting nearly over, Mark has built a pen...

..which he'll leave on the shores of an isolated lake.

'This will give the orphans somewhere familiar to come back to

'until they're able to fend for themselves.'

All set?

Wow, this is the moment, guys.

MARK WARBLES

Oh, look at that.

How amazing.

You can't imagine what it's like. It's like...

MARK WARBLES

..having never been outside in your life, isn't it?

Exactly. All these new, funny things to explore.

They're so funny. They're just into everything.

They run for about ten feet

and then stop and look around and then they run.

They're just crazy.

They're checking everything out.

Checking my tripod out.

You know what's lovely is the point where they get to the water...

..because they're suddenly going to be otters, finally.

It's all very well looking like an otter,

but to actually be free and be

swimming and catching fish, that's the special bit.

So this is the accumulation of all of our efforts coming to the end

and this is the kind of moment we've been waiting for since we started.

And gives you a lot of satisfaction to be able to see them out there,

swimming and doing what they're doing...

..knowing that you had a chance to set it right

for what went wrong in the first place.

We'll still continue to put food out for them

but they need to find their independence now.

And they're smart enough to do it.

I mean, you're still kind of mum, aren't you?

But you're a hands-off mum.

Exactly.

Today we cut the apron strings a little bit. Right.

'And it's obvious that the orphans are relishing their first real taste of freedom.'

They'll just keep expanding their range little by little and start

checking things out and getting more adventurous

and eventually they'll go probably around the whole lake

and, not too much longer, they'll probably start heading

up and down the creeks that are

coming in and out and seeing what's there.

'In the same way a mother otter would keep catching fish

'for her young at this age in the wild...

'..until Mark is sure that they're using

'all their learned and innate skills

'he'll keep putting out food for them.'

And what happens, do you stop feeding them first and then they go

or do they generally just move off?

They generally just move off, so we'll offer food for a while until

we notice the food's not disappearing any more

and we don't see them any more.

So it's their first night alone, now, isn't it?

Yeah, it'll be the first night alone but I think they'll do just fine.

They've had a lot of fun today and I think

they're just going to find a place to go to sleep.

I think they're going to sleep well.

I think so, too. They got a good supper, they should be good.

'As night falls, I can't help but worry for them.

'Although Mark's provided them with food,

'for the first time in their lives

'they will have no one looking out for them.'

'As soon as it's light I'm keen to check up on the orphans.

'At first there doesn't seem to be any sign of them.

'But then I hear some familiar chirps.'

CHIRPING

'I'm delighted. All three are foraging together.'

There's something about when you see a group of otters like this, you know,

three otters almost like this one animal and three bodies.

They move so perfectly, so in sync with each other.

They know where each other is the whole time.

They know what each other is doing.

Even though sometimes they can't see each other.

You know, this is really murky, peaty water.

They can't see in it, but they always know where each other is.

For Mark to have got them from three tiny cubs to this state

and to put them in this place and release them so quickly

and so effectively is brilliant. I think he's done a great job.

Just looking at these guys from this canoe,

it's just like watching a group of wild otters

and they're doing everything that wild otters do.

They're behaving like wild otters.

They're hunting along in the reeds and the lilies

along the edge of the lake.

And they're foraging. That's what otters do.

They're not always out in the middle of the lake speeding after fish.

Most of the time they spend nosing around in the weeds

trying to find some food, and that's exactly what these guys are doing.

So it makes me very hopeful.

You look at them behaving like real, wild otters and you think, well,

if you can do that within 24 hours of being released,

I think the chances of survival for these guys are pretty high.

'Mark has given the orphans a real second chance at life.

'And as long as they stick together,

'harness everything their surrogate mum has taught them...

'..alongside their own natural instincts,

'they should be able to cope with most things.'

I'm reassured that otters have what it takes to survive.

History has shown this.

Where otter populations were at record lows...

..some are now coming back.

40 years ago, the Eurasian otter was extinct across most of the UK.

Now it's found in every county.

And the sea otter numbered just 2,000 individuals a century ago.

But with the help of protection and reintroduction programmes

has made a population increase to 125,000.

We can't get complacent.

Across the globe otters ARE threatened,

but where they're given the chance, they can adapt to a changing world.

CHIRPING

And there's one place where they've made a very surprising comeback.

Downtown Singapore.

Singapore is one of the busiest countries in the world.

Attracting over 15 million visitors a year,

it might not seem like a haven for wildlife.

But despite the hustle and bustle,

and having been thought extinct here just a few decades ago,

in 2014, smooth-coated otters moved into the city centre.

There are now thought to be well over 60 otters

living inside the city state.

The reason? Fresh water in Singapore's Marina Bay has,

for the last nine years, been highly protected.

There's next to no fishing or pollution.

The result is a vast reservoir, absolutely full of fish.

Perfect for otters.

And now, on a daily basis,

they demonstrate one of the characteristics I love most.

Their close family bond.

What's really freaking me out is that

the last time I filmed a group of otters this big and this social

and exciting was in one of the remotest parts of the Amazon.

That was a group of giant otters, 15 of them.

Now I've got 13 completely wild otters right in the middle of,

I guess, one of the most densely populated cities on earth.

'And this family has just expanded Singapore's population even further.

'They have four 11-week-old pups.'

'And just like the orphans in Wisconsin,

'they, too, are on a journey of survival.'

Otters are very sensitive animals.

They've been in trouble across the world for a long time now.

But, if Singapore proves anything to me, it's that they are adaptable.

'I've no doubt otters are survivors.

'For me, it's all about their supercharged nature.

'And I think it's this that makes me smile every time I see one.

'And here in Singapore there are plenty of other smiling faces.

'That's because otters ARE special and, given a chance,

'will always make the most of what's available to them.'

They need nice, clean water, a decent supply of food,

and they need to be free from persecution.

And clearly, Singapore's provided them the perfect home.

And that basically proves to me that these shy, nocturnal,

secretive animals that we kind of all think otters are,

give them the right ingredients for life...

..protect them, and they'll thrive.

And in the weeks and months following their release,

through autumn and winter, the orphans in Wisconsin

are also thriving.