0:00:09 > 0:00:13Rarely seen, they have a near-mythical reputation.
0:00:15 > 0:00:20They have boundless energy and are able to dive deep...
0:00:22 > 0:00:24..and catch the fastest of prey.
0:00:27 > 0:00:28Otters.
0:00:31 > 0:00:34My name is Charlie Hamilton James,
0:00:34 > 0:00:38wildlife cameraman and otter fanatic.
0:00:40 > 0:00:45I've been observing and filming these shy but relentless animals
0:00:45 > 0:00:47for the last 25 years.
0:00:48 > 0:00:52For me, otters are the ultimate predator,
0:00:52 > 0:00:55perfectly bridging the gap between two worlds -
0:00:55 > 0:00:58one dry, one wet.
0:01:01 > 0:01:03Yet across the planet,
0:01:03 > 0:01:05their populations have hung in the balance.
0:01:06 > 0:01:10I've done what I can for their conservation.
0:01:10 > 0:01:12However, many remain in danger.
0:01:13 > 0:01:15But otters are fighters...
0:01:16 > 0:01:21..supercharged with a huge amount of spirit and determination.
0:01:22 > 0:01:25And now, with the help of three orphaned cubs...
0:01:27 > 0:01:30..some ground-breaking experiments...
0:01:31 > 0:01:33It's done it, that was it!
0:01:33 > 0:01:36..and some incredible wild encounters...
0:01:38 > 0:01:42..I'm going to reveal their survival secrets
0:01:42 > 0:01:47and just why I think otters are such a special group of animals.
0:01:59 > 0:02:01I spent my life searching for
0:02:01 > 0:02:04glimpses of these rare and elusive creatures.
0:02:05 > 0:02:07They're nervous
0:02:07 > 0:02:08and fearful of humans.
0:02:10 > 0:02:14But there's one place where they're bolder than most -
0:02:14 > 0:02:16Florida.
0:02:20 > 0:02:24Here, clear, spring-fed rivers provide the ideal opportunity
0:02:24 > 0:02:27to film otters moving and hunting underwater.
0:02:31 > 0:02:32Something few have ever done.
0:02:35 > 0:02:38If I succeed, it'll be the perfect way
0:02:38 > 0:02:40to begin a journey into their seldom-seen world.
0:03:08 > 0:03:09They know I'm here.
0:03:10 > 0:03:12They're far too inquisitive not to have noticed.
0:03:13 > 0:03:15But they don't seem to mind.
0:03:23 > 0:03:26There are more otters here than anywhere I've ever been.
0:03:30 > 0:03:33But, typically, they don't keep still for long.
0:03:41 > 0:03:45North American river otters can cover over 40km a day...
0:03:47 > 0:03:51..and swim for 400m without coming up for air.
0:03:53 > 0:03:56If you're going to observe otters in the wild, you need patience...
0:03:57 > 0:03:58..and a bit of luck.
0:04:02 > 0:04:04I spot a telltale sign.
0:04:05 > 0:04:06A trail of bubbles.
0:04:17 > 0:04:18Absorbed by foraging...
0:04:19 > 0:04:21..this is my chance to get close.
0:04:25 > 0:04:27I want to see how it's hunting.
0:04:29 > 0:04:31Something I've never achieved before.
0:04:34 > 0:04:38But I know just a flick of its tail and it could be off in a flash.
0:04:41 > 0:04:42He's so focused.
0:04:44 > 0:04:45I just need to hold my nerve.
0:04:57 > 0:05:01In 25 years of watching otters, I've just got these little glimpses
0:05:01 > 0:05:03occasionally of them underwater,
0:05:03 > 0:05:06and here, in a single morning,
0:05:06 > 0:05:10I've seen more otters underwater than in that whole 25 years.
0:05:14 > 0:05:17But what's been really interesting is actually looking
0:05:17 > 0:05:18at how they're hunting.
0:05:22 > 0:05:26It made me watch him and understand and look at the way he was doing
0:05:26 > 0:05:27stuff, the way he was swimming and fishing,
0:05:27 > 0:05:29in a completely different way.
0:05:33 > 0:05:35In this one incredible experience,
0:05:35 > 0:05:40a completely wild otter allowed me to come here,
0:05:40 > 0:05:42hang out and watch him fish underwater.
0:05:54 > 0:05:56There's an otter right there.
0:05:56 > 0:05:57HE CHORTLES
0:05:58 > 0:06:01This place is so amazing.
0:06:01 > 0:06:03There's just otters everywhere. It is otter heaven.
0:06:05 > 0:06:07I need to go get back in the water.
0:06:07 > 0:06:09It's all very well sitting here talking to the camera
0:06:09 > 0:06:12but I'd rather be swimming with an otter.
0:06:15 > 0:06:16The experience has reminded me why
0:06:16 > 0:06:19otters have captivated me for so long.
0:06:21 > 0:06:23They are incredible predators.
0:06:24 > 0:06:26Energetic,
0:06:26 > 0:06:27inquisitive
0:06:27 > 0:06:29and versatile -
0:06:31 > 0:06:33..traits they share with their extended family.
0:06:35 > 0:06:36The mustelids.
0:06:36 > 0:06:41An ancient and diverse group of carnivores
0:06:41 > 0:06:42that includes weasels,
0:06:42 > 0:06:46stoats, badgers and martens.
0:06:46 > 0:06:49Otters can be found on nearly every continent,
0:06:49 > 0:06:51from the Arctic Circle
0:06:51 > 0:06:54to the swamps of Africa.
0:06:54 > 0:06:59And from desert oases to the tempestuous seas of Patagonia.
0:07:03 > 0:07:06But there are some things that unite all otter species.
0:07:08 > 0:07:11They have long, highly flexible bodies...
0:07:15 > 0:07:17..a powerful tail
0:07:17 > 0:07:18and webbed feet.
0:07:21 > 0:07:25Some can dive to 100 metres...
0:07:25 > 0:07:30and hold their breath for over four minutes.
0:07:36 > 0:07:41But despite their amazing physical abilities,
0:07:41 > 0:07:45all over the world, otter numbers have been in decline.
0:07:45 > 0:07:47BARKING
0:07:49 > 0:07:52They've been hunted for sport
0:07:52 > 0:07:54and for their fur.
0:08:01 > 0:08:03They've lost their food to human greed...
0:08:06 > 0:08:09..and have seen their habitat poisoned and ruined.
0:08:14 > 0:08:18But given the chance, otters are survivors
0:08:18 > 0:08:21enduring against all odds.
0:08:23 > 0:08:27It's one of the reasons I've always done what I can,
0:08:27 > 0:08:28caring for otters in need.
0:08:30 > 0:08:33I've even welcomed them into my family.
0:08:36 > 0:08:38Otter!
0:08:38 > 0:08:39Otter!
0:08:41 > 0:08:42Honey, a Eurasian otter
0:08:42 > 0:08:44too dependent on humans to be released...
0:08:45 > 0:08:47..held a special place in my heart.
0:08:50 > 0:08:56And the time I spent with her only made by love for otters stronger.
0:09:02 > 0:09:05To help me reveal what I believe sets otters apart,
0:09:05 > 0:09:08I'm going to follow three male orphan river otters
0:09:08 > 0:09:11on their own story of survival.
0:09:13 > 0:09:15As they grow they'll be taught
0:09:15 > 0:09:18the vital skills they'll need for a life back in the wild.
0:09:21 > 0:09:26After being abandoned by their mothers, the orphans were brought
0:09:26 > 0:09:29to Wild Instincts wildlife rehab centre.
0:09:29 > 0:09:32On arrival they were weak, defenceless
0:09:32 > 0:09:36and would not have survived the night.
0:09:36 > 0:09:39Attempting to mirror their wild diet,
0:09:39 > 0:09:44centre manager Mark is giving them chopped fish and milk formula.
0:09:48 > 0:09:51But he has concerns about the weakest orphan.
0:09:51 > 0:09:54He came to us with a kind of a bad leg.
0:09:54 > 0:09:56He injured the joint on his right rear leg,
0:09:56 > 0:09:59so we're not quite sure whether it's going to heal enough for him
0:09:59 > 0:10:02to be released or not and he also did a slight injury to the joint
0:10:02 > 0:10:05right in here on this leg also
0:10:05 > 0:10:08and even the good leg is not necessarily a good leg.
0:10:08 > 0:10:11So what we're going to do is try to find a zoo for him
0:10:11 > 0:10:14if he's not able to be released back into the wild,
0:10:14 > 0:10:15and if we're unable to find a zoo then he
0:10:15 > 0:10:19may have to be euthanized if we can't find a place for him to go.
0:10:21 > 0:10:24To keep any attachment to a minimum,
0:10:24 > 0:10:28it's Mark's policy not to name any of the animals in his care.
0:10:31 > 0:10:34Now eight weeks old,
0:10:34 > 0:10:37the cubs need to tackle an essential survival skill -
0:10:38 > 0:10:40..learning to swim.
0:10:45 > 0:10:49Curiously, baby otters don't really like water.
0:10:58 > 0:11:03So Mark needs to teach them their most important life lesson -
0:11:03 > 0:11:06that water isn't something to be afraid of.
0:11:11 > 0:11:14Just like their mother would in the wild,
0:11:14 > 0:11:17Mark makes soothing calls to reassure them.
0:11:17 > 0:11:18HE WARBLES SOFTLY
0:11:18 > 0:11:19OTTERS CHIRP IN RESPONSE
0:11:21 > 0:11:23Each time they try to get out,
0:11:23 > 0:11:25Mark plops them back in.
0:11:28 > 0:11:30But their swimming lessons don't last too long.
0:11:34 > 0:11:38That's because of another surprising quirk of otter biology.
0:11:39 > 0:11:43Their coat doesn't become waterproof until they are 12 weeks old.
0:11:44 > 0:11:48Until then, being wet could lead to hypothermia.
0:11:50 > 0:11:54So surrogate mum Mark does what he can to help out.
0:11:55 > 0:11:57Normally in the wild what they would be doing is rolling around in
0:11:57 > 0:11:59the grass and the dirt
0:11:59 > 0:12:01to get some of the water off themselves,
0:12:01 > 0:12:04so we can use the towels to help us out a little bit.
0:12:14 > 0:12:17Wild otter cubs face exactly the same issue,
0:12:17 > 0:12:20so the adults only take them for short dips
0:12:20 > 0:12:23to stop them getting cold and waterlogged.
0:12:37 > 0:12:40It's exactly what I saw with a family
0:12:40 > 0:12:42of giant river otters in the Amazon.
0:12:50 > 0:12:53Wow, look at that. Tiny!
0:12:55 > 0:13:01That is really young. That can't be more than six weeks old.
0:13:01 > 0:13:02He's got another one.
0:13:09 > 0:13:11Giant river otters are highly social
0:13:11 > 0:13:16and with such young pups in the water, the whole family helps out.
0:13:21 > 0:13:23They're too small to start swimming properly.
0:13:24 > 0:13:26It's just a taster session
0:13:26 > 0:13:29under the watchful eyes of their parents and siblings.
0:13:31 > 0:13:35Eventually, they'll become accomplished enough in the water
0:13:35 > 0:13:37to catch fast, wild prey.
0:13:46 > 0:13:50Back in Wisconsin, otter foster parent Mark is about to start
0:13:50 > 0:13:53teaching the orphans how to fish.
0:13:54 > 0:13:57But first the orphan with the bad leg needs a little extra help.
0:14:01 > 0:14:04So Mark has designed a swimming aid
0:14:04 > 0:14:06and is giving him a course of aquatherapy.
0:14:06 > 0:14:09OTTER CHIRRUPS FRANTICALLY
0:14:11 > 0:14:14So it looks like the little apparatus we have put on there seems
0:14:14 > 0:14:17to be accomplishing what we wanted it to do. It keeps him afloat
0:14:17 > 0:14:21and he's using his rear legs much better than he was before without it
0:14:21 > 0:14:25so hopefully this will be some good therapy and get him on the path
0:14:25 > 0:14:26to being what he needs to be.
0:14:30 > 0:14:31He's obviously a little fighter.
0:14:33 > 0:14:35As I arrive,
0:14:35 > 0:14:38Mark's just about to give them live fish for the first time.
0:14:44 > 0:14:45MARK WARBLES
0:14:47 > 0:14:48Oh, my God.
0:14:55 > 0:14:58Mark adds some minnows to the paddling pool
0:14:58 > 0:15:01and hopes that hunting is more instinctive than swimming.
0:15:04 > 0:15:05How cute is that?
0:15:05 > 0:15:06Go on, then.
0:15:10 > 0:15:12Yesterday we were doing a bit of diving and swimming around
0:15:12 > 0:15:15and now there'll be something to swim and dive around for
0:15:15 > 0:15:17so we'll see if they have any luck chasing around.
0:15:20 > 0:15:23This one's completely at home. It's just chased a fish.
0:15:23 > 0:15:25Exactly, exactly.
0:15:25 > 0:15:27Straightaway. And that's just in a few days.
0:15:27 > 0:15:30- It's gone from nothing to chasing fish underwater.- Right.
0:15:30 > 0:15:31He's got a fish.
0:15:31 > 0:15:33He's got one.
0:15:33 > 0:15:35He let it go.
0:15:35 > 0:15:37He's got it, he's got it.
0:15:37 > 0:15:38That's his first fish.
0:15:38 > 0:15:39Isn't that amazing?
0:15:40 > 0:15:43Yesterday he wasn't even putting his head underwater
0:15:43 > 0:15:45and today he caught his first little fish.
0:15:45 > 0:15:48That is amazing, isn't it? He's just rolling around playing with it.
0:15:48 > 0:15:50- That's a great moment for them.- Wow.
0:15:52 > 0:15:54Fishing, for the orphans, appears to be innate.
0:15:55 > 0:15:57It's a good sign.
0:15:57 > 0:16:00But it's something they'll need to hone.
0:16:01 > 0:16:03Do you know what?
0:16:04 > 0:16:09To me, there is nothing in the world that compares to otters.
0:16:09 > 0:16:13I could sit here all day every day and do nothing else for the rest of
0:16:13 > 0:16:16my life, just hang with otters.
0:16:16 > 0:16:17That's when I'm at my happiest.
0:16:19 > 0:16:21'As the orphans get bigger,
0:16:21 > 0:16:24'their swimming abilities will develop, too,
0:16:24 > 0:16:28'until they're as agile in the water as the fish they hunt.'
0:16:35 > 0:16:39But otters aren't just masters of the water.
0:16:39 > 0:16:42They spend up to 80% of their lives on land.
0:16:44 > 0:16:49Their ability to lead this semiaquatic double life is what allows them
0:16:49 > 0:16:51to cope with diverse habitats and prey.
0:16:54 > 0:16:58The key to this lies in their physiology,
0:16:58 > 0:17:00and back in the UK,
0:17:00 > 0:17:04I've got a furry friend to help reveal the secrets of their success.
0:17:07 > 0:17:11This is Rudy. He's an Asian small-clawed otter...
0:17:12 > 0:17:15..or short-clawed otter, because he's got tiny little claws.
0:17:16 > 0:17:19And the aim is to get a really decent look at Rudy
0:17:19 > 0:17:23and how his body works, how his physiology works,
0:17:23 > 0:17:26how he turns from an animal that can run around on the land
0:17:26 > 0:17:29to an animal that's as fast as a fish in water,
0:17:29 > 0:17:33and it gives me an excuse to just hang out with an otter.
0:17:35 > 0:17:37I think you need to go and see the dentist, Rudy.
0:17:40 > 0:17:44This camera is going to do some nice slow motion shots
0:17:44 > 0:17:49and I can track along with the otter and then we can, you know,
0:17:49 > 0:17:51we can get a good look at how it's running.
0:17:51 > 0:17:55And Rod here is going to film Rudy swimming in close-up
0:17:55 > 0:17:57and particularly in slow motion.
0:17:58 > 0:18:02The thing I've always wondered, watching them and filming them,
0:18:02 > 0:18:05is how do they go from land to water and be so brilliant at both?
0:18:05 > 0:18:08And I think the reason I like what we're doing now is because we're
0:18:08 > 0:18:11going to get a really detailed look at that and try to get
0:18:11 > 0:18:14some understanding of how they manage to do that
0:18:14 > 0:18:17because very few animals can just flip between two worlds like that.
0:18:19 > 0:18:20Otters do it brilliantly.
0:18:23 > 0:18:25When we slow the action right down...
0:18:28 > 0:18:30..we can see exactly what's going on.
0:18:35 > 0:18:37Otter spines are highly flexible...
0:18:38 > 0:18:40..allowing Rudy to rotate his hips...
0:18:42 > 0:18:47..swing his leg forward and plant his feet securely on the floor...
0:18:50 > 0:18:53..and use his powerful tail for balance.
0:18:57 > 0:19:00And unlike most land-based carnivores,
0:19:00 > 0:19:03his front feet are well-developed
0:19:03 > 0:19:07with long, dextrous fingers for foraging and handling prey.
0:19:13 > 0:19:17By bending their highly flexible spines,
0:19:17 > 0:19:19otters are able to decrease the distance
0:19:19 > 0:19:26between the shoulder and hip by over 20%, allowing them to bound,
0:19:26 > 0:19:27running up to 18mph.
0:19:30 > 0:19:34But the adaptations that allows them to live a semiaquatic life
0:19:34 > 0:19:38become clearer as Rudy enters the water.
0:19:38 > 0:19:41A substance 800 times denser than air.
0:19:43 > 0:19:45As he puts his head into the water,
0:19:45 > 0:19:48his vision becomes blurry, just like it does for us.
0:19:50 > 0:19:54But an almost magical adaptation allows him to correct this,
0:19:54 > 0:19:57like an in-built pair of swimming goggles.
0:19:59 > 0:20:02At first, the density of the water stops light rays
0:20:02 > 0:20:05being brought into sharp focus on his retina.
0:20:07 > 0:20:11But Rudy has highly specialised muscles in his iris
0:20:11 > 0:20:14that squeeze the lens so that its face bulges forward.
0:20:16 > 0:20:19This refocuses the light rays onto the back of his eye...
0:20:20 > 0:20:23..giving him sharp underwater vision.
0:20:25 > 0:20:27Now that he can see clearly,
0:20:27 > 0:20:30he enters the water fully and his next trick is revealed.
0:20:32 > 0:20:35Pushing his broad head forward and rotating his hips,
0:20:35 > 0:20:38he is able to straighten his body like a torpedo.
0:20:39 > 0:20:43Tucking his legs in, he reduces the water's drag...
0:20:47 > 0:20:50..only untucking them when he wants a burst of speed.
0:20:53 > 0:20:58Next he uses his flexible spine in combination with his tail and
0:20:58 > 0:21:01webbed rear feet to turn and twist in the water.
0:21:04 > 0:21:08The agility of otters blows me away.
0:21:15 > 0:21:19Rudy has mastered the skills for a semiaquatic life
0:21:19 > 0:21:23but our orphans in Wisconsin are just learning how to make
0:21:23 > 0:21:26the most of their two worlds.
0:21:26 > 0:21:29They're now 12 weeks of age,
0:21:29 > 0:21:32old enough to move outside into an enclosure with permanent water...
0:21:36 > 0:21:38..where Mark is going to introduce them
0:21:38 > 0:21:39to some different prey.
0:21:41 > 0:21:45So today we're going to do some freshwater clams, some crayfish,
0:21:45 > 0:21:46then we're also going to do some frogs.
0:21:46 > 0:21:49So we're going to start off by introducing the clams first and,
0:21:49 > 0:21:52since they really don't know what these things are,
0:21:52 > 0:21:53I'm going to cut them open for them,
0:21:53 > 0:21:55so I'm going to give each one a clam
0:21:55 > 0:21:57and then what we'll do is throw some in the pond,
0:21:57 > 0:21:59let them kind of figure it out,
0:21:59 > 0:22:00because they'll get the taste for it
0:22:00 > 0:22:03and realise that, hey, this is something I can eat.
0:22:04 > 0:22:06A wild otter's diet is broad.
0:22:07 > 0:22:10They catch and eat everything from snails to octopus.
0:22:12 > 0:22:15And their inquisitive nature has led
0:22:15 > 0:22:18to one species evolving an incredible talent -
0:22:18 > 0:22:20the use of tools.
0:22:26 > 0:22:29Sea otters feed on crustaceans and molluscs
0:22:29 > 0:22:33but their hard exoskeleton is notoriously tricky to get into.
0:22:39 > 0:22:44So each otter has preferred tools for accessing its favourite foods.
0:22:47 > 0:22:50Be it a rock for opening clams...
0:22:53 > 0:22:55..the bow of an expensive boat for oysters...
0:23:02 > 0:23:05..or an empty beer bottle for barnacles.
0:23:10 > 0:23:13By focusing on particular prey,
0:23:13 > 0:23:16sea otters have a balancing effect on the ecosystem...
0:23:17 > 0:23:19..helping to keep it healthy.
0:23:23 > 0:23:26Otters seem to have a relentless curiosity.
0:23:26 > 0:23:30To me it's an indicator of just how intelligent they are.
0:23:32 > 0:23:36An endearing trait, and one that often results in play.
0:23:41 > 0:23:44Essential for all otters as they grow and develop...
0:23:48 > 0:23:51..teaching them crucial life lessons.
0:24:15 > 0:24:17And it's exactly what I had to do with Honey...
0:24:18 > 0:24:19..the otter I reared at home.
0:24:22 > 0:24:23HE GIGGLES
0:24:25 > 0:24:29But play for her wasn't always much fun for me.
0:24:29 > 0:24:33Ow! That's my skull! Ah, get off!
0:24:33 > 0:24:37This whole biting my skull thing, Honey, I'm not a fan.
0:24:42 > 0:24:46In social species, the bonds that play solidifies
0:24:46 > 0:24:48makes otter families a formidable force.
0:24:52 > 0:24:54Especially important for giant river otters,
0:24:54 > 0:24:57who regularly face deadly predators.
0:25:00 > 0:25:02With vulnerable young cubs,
0:25:02 > 0:25:05this family discovered a large black caiman in their territory.
0:25:11 > 0:25:15Identifying it as a threat, they work together,
0:25:15 > 0:25:17systematically attacking it.
0:25:31 > 0:25:35For three hours, the otters pinned it down,
0:25:35 > 0:25:38taking it in turns to attack its underside and head.
0:25:56 > 0:26:01Eventually, the enormous size and power of the caiman was no match
0:26:01 > 0:26:06for the family, whose bonds are so strong that they would risk dying for each other.
0:26:28 > 0:26:30For the orphans in Wisconsin,
0:26:30 > 0:26:32their best chance of a future in the wild
0:26:32 > 0:26:34will come from staying together.
0:26:35 > 0:26:38Now they can get a lot more exercise,
0:26:38 > 0:26:42start doing what they need to do and start being a lot less dependent on
0:26:42 > 0:26:45us, and we can start cutting off our human contact with them so they can
0:26:45 > 0:26:49learn to be otters and not rely on humans too much any more.
0:26:51 > 0:26:54They now have their most important piece of survival equipment -
0:26:57 > 0:26:59..a warm and completely waterproof coat.
0:27:03 > 0:27:06Fur is an otter's secret weapon.
0:27:08 > 0:27:10They all rely on it to keep warm.
0:27:14 > 0:27:16But to understand its special qualities,
0:27:16 > 0:27:18we need to look at sea otters once again.
0:27:20 > 0:27:24They have the densest and most luxurious fur of any animal.
0:27:26 > 0:27:27It's such high quality
0:27:27 > 0:27:31that trappers historically measured all other fur against it.
0:27:33 > 0:27:34It's the main reason sea otters
0:27:34 > 0:27:37have been persecuted throughout their range.
0:27:40 > 0:27:43Their fur has nearly one million hairs per square inch.
0:27:48 > 0:27:51To properly appreciate the world's furriest animal,
0:27:51 > 0:27:55I've come to Monterey Bay Aquarium in California
0:27:55 > 0:27:58whose sea otter reintroduction programme has been
0:27:58 > 0:28:00instrumental in the recovery of the population.
0:28:03 > 0:28:08- Beautiful.- 'The aquarium's head vet, Dr Mike Murray, has anaesthetised
0:28:08 > 0:28:10'a female otter for a checkup,
0:28:10 > 0:28:12'giving me a chance to take a close look.'
0:28:13 > 0:28:17Look at the size of that. That's enormous!
0:28:17 > 0:28:18She actually feels really warm.
0:28:20 > 0:28:24That really, really thick fur they have is designed to conserve heat
0:28:24 > 0:28:28and she really doesn't, without cold water, have an opportunity to dump heat.
0:28:29 > 0:28:31Her coat is so effective
0:28:31 > 0:28:34that Dr Mike has to put bags of ice on her flippers
0:28:34 > 0:28:35to stop her overheating.
0:28:39 > 0:28:43This is the most beautiful, silky, soft fur you can imagine.
0:28:44 > 0:28:46On the outside it's much thicker
0:28:46 > 0:28:52but when you get down deep inside it's just silk-smooth.
0:28:52 > 0:28:57You can just make out the sort of pale, white skin underneath.
0:28:58 > 0:29:00It's amazing how wet it is on the outside
0:29:00 > 0:29:03and then you peel it back and it's completely dry on the inside.
0:29:05 > 0:29:07That is beautiful.
0:29:07 > 0:29:10It's so soft you can barely feel it. It's weird.
0:29:11 > 0:29:14And if you look at the undercoat,
0:29:14 > 0:29:16they've got these long guard hairs, but down deep,
0:29:16 > 0:29:18you look at those microscopically
0:29:18 > 0:29:22and they've got all these little scales that stick off the shaft of the fur
0:29:22 > 0:29:25and what the otter does when it grooms is,
0:29:25 > 0:29:29it just conditions the fur to get those things to lock together
0:29:29 > 0:29:32so that it becomes impenetrable to water, essentially,
0:29:32 > 0:29:34and they can get air in those spaces,
0:29:34 > 0:29:37very similar to a down jacket or down vest that we might be wearing.
0:29:39 > 0:29:42Looking at the undercoat in microscopic detail
0:29:42 > 0:29:44shows these scales lining the shaft of each hair.
0:29:46 > 0:29:49Grooming increases the volume of air trapped in this layer...
0:29:52 > 0:29:56..maximising its insulation potential.
0:30:00 > 0:30:03And in the freezing waters of Alaska,
0:30:03 > 0:30:05survival relies on good insulation.
0:30:08 > 0:30:11This mother is fluffing up her baby's coat.
0:30:12 > 0:30:14By blowing into its fur
0:30:14 > 0:30:17she's filling it with air to keep him warm.
0:30:20 > 0:30:23The more trapped air, the warmer it is.
0:30:28 > 0:30:32But for it to be effective, it needs to be kept in top condition...
0:30:34 > 0:30:38..which means otters spend hours each day grooming...
0:30:43 > 0:30:47..using their flexible spine to reach those hard-to-get spots.
0:30:54 > 0:30:59We can see just how effective their coat is with the help of some technology.
0:31:01 > 0:31:04This is a thermal camera, so what it does,
0:31:04 > 0:31:07instead of looking at a straight image of something
0:31:07 > 0:31:09as we would normally look at through a camera,
0:31:09 > 0:31:11this looks at the heat signature of everything, so it can
0:31:11 > 0:31:14tell the difference between hot and cold and it shines up here.
0:31:14 > 0:31:18You know, the yellow bits are warmer, the purple bits are colder.
0:31:18 > 0:31:20It's going to be really interesting
0:31:20 > 0:31:21looking at the sea otter with this camera,
0:31:21 > 0:31:24because it'll show me which parts of the sea otter are retaining heat
0:31:24 > 0:31:27and which parts are giving off heat.
0:31:28 > 0:31:30OK, so she's right underneath me now.
0:31:30 > 0:31:32This is going to be a really nice shot.
0:31:32 > 0:31:33There she is.
0:31:38 > 0:31:39So you can see, looking at that,
0:31:39 > 0:31:42the bits that are really shining up yellow
0:31:42 > 0:31:44are her eyes and her mouth and nose
0:31:44 > 0:31:46and just a few bits on the side of her head,
0:31:46 > 0:31:50so those are the main bits that are losing heat. That's amazing.
0:31:52 > 0:31:57What's interesting is that the water temperature here's around
0:31:57 > 0:32:017 Celsius, and her body temperature is around 37 Celsius.
0:32:01 > 0:32:04So we're actually looking at a 30-degree difference between
0:32:04 > 0:32:06the water temperature and her body,
0:32:06 > 0:32:08but we're not seeing it on the picture.
0:32:08 > 0:32:10Her body is almost the same colour as the water.
0:32:13 > 0:32:14So what that means is,
0:32:14 > 0:32:17that thick fur that the otter's got
0:32:17 > 0:32:19is so good at insulating the otter
0:32:19 > 0:32:21that very little heat is coming off it,
0:32:21 > 0:32:24almost no difference between the water temperature
0:32:24 > 0:32:27and the temperature of the otter on the outside of the otter
0:32:27 > 0:32:31because all the heat, that 37 degrees, is being kept inside.
0:32:36 > 0:32:40This highly specialised coat is one of the reasons otters
0:32:40 > 0:32:43are more capable on land than other semiaquatic mammals...
0:32:47 > 0:32:48..like sea lions.
0:32:48 > 0:32:49SEA LIONS HONK
0:32:53 > 0:32:59One of the differences between these Californian sea lions and otters is
0:32:59 > 0:33:03not just the fact that they've given up their legs for flippers...
0:33:04 > 0:33:07..but they're fat, great, big fat, lummoxing things.
0:33:07 > 0:33:09They're useless on land.
0:33:09 > 0:33:13This is pretty much the extent of what they can do on land,
0:33:13 > 0:33:15which is climb ashore and go to sleep.
0:33:15 > 0:33:18And otters? Otters can be really successful predators on land
0:33:18 > 0:33:21and the reason is, they don't have any blubber.
0:33:21 > 0:33:23These guys use blubber to keep themselves warm in the sea.
0:33:24 > 0:33:28Otters use fur, and one inch of fur
0:33:28 > 0:33:32is the equivalent, in insulating terms, of four inches of blubber.
0:33:40 > 0:33:43The otter's fur coat not only provides them
0:33:43 > 0:33:45with superb insulation in the water,
0:33:45 > 0:33:49it also allows them to have incredible agility on land...
0:33:52 > 0:33:56..something the orphans in Wisconsin will need to take advantage of.
0:33:58 > 0:34:01At five months old, their confidence is growing.
0:34:02 > 0:34:06And their curious, intelligent nature is starting to shine through.
0:34:07 > 0:34:09So now what we can do is...
0:34:09 > 0:34:11So they know you're going to feed them, don't they?
0:34:11 > 0:34:12We can toss in a fish or two.
0:34:15 > 0:34:17And normally, as soon as you get a couple in there...
0:34:19 > 0:34:21Look at that, he's straight on it. Wow.
0:34:23 > 0:34:24That was so fast.
0:34:29 > 0:34:32It's so lovely to come back here and see how they've developed.
0:34:32 > 0:34:35I mean, they're just huge now, compared to what they were.
0:34:35 > 0:34:38They were tiny little, helpless, useless otters
0:34:38 > 0:34:41and, back then, we gave them their first fish
0:34:41 > 0:34:44and thought, "Wow, they can catch a fish, isn't that wonderful?"
0:34:44 > 0:34:46Now you watch them and they're just pros now.
0:34:47 > 0:34:48Exactly.
0:34:48 > 0:34:50If you look,
0:34:50 > 0:34:51now you have a hard time telling who
0:34:51 > 0:34:53the guy with the bum leg was.
0:34:53 > 0:34:56He doesn't show any sign of any problems any more.
0:34:56 > 0:34:59He's just as good as the other ones at catching fish
0:34:59 > 0:35:01and just as fast and agile as everybody else.
0:35:03 > 0:35:07I'm relieved that the injury to his back leg has recovered so well.
0:35:07 > 0:35:11It's testament to Mark's skills as a substitute mother.
0:35:11 > 0:35:14He's taken the camera out now. Look at that.
0:35:14 > 0:35:16The camera is going in.
0:35:16 > 0:35:18How can we get this in?
0:35:18 > 0:35:20They will figure it out.
0:35:20 > 0:35:22Oh, he's reframed it for us!
0:35:23 > 0:35:26They're just into everything, aren't they?
0:35:26 > 0:35:28- Yeah.- And that's otters for you, isn't it?
0:35:28 > 0:35:32- Exactly.- Crazy into everything. - Everything.
0:35:32 > 0:35:34Just like this, with the block.
0:35:34 > 0:35:38You worry about them tipping the block over on themselves, and, er...
0:35:38 > 0:35:40Aww!
0:35:43 > 0:35:44There we go. It's sunk.
0:35:44 > 0:35:46THEY LAUGH
0:35:48 > 0:35:52They're now swimming around, looking at themselves underwater in it.
0:35:52 > 0:35:54They're doing otter selfies.
0:36:00 > 0:36:04'I just love their energy and determination.'
0:36:05 > 0:36:08These guys are clearly well on the way to having the skills
0:36:08 > 0:36:13they'll need to survive in the wild, and that time is fast approaching.
0:36:13 > 0:36:17Their release into Wisconsin's northern woods is only a month away.
0:36:18 > 0:36:21- They've got each other. - They do.
0:36:21 > 0:36:24I mean, one otter, you know, that's tricky. Three otters together?
0:36:24 > 0:36:28- They can learn from each other, they are safer in numbers.- Exactly.
0:36:28 > 0:36:32- So they should do pretty well. - They can certainly fish.
0:36:34 > 0:36:36So I think we'll go on out of here.
0:36:36 > 0:36:38they're starting to get a little bit too used to us.
0:36:38 > 0:36:41We're trying to keep our contact to a minimum
0:36:41 > 0:36:43so let's get on out of here.
0:36:43 > 0:36:45Cheers, guys.
0:36:47 > 0:36:50Mark's intentionally keeping contact with the orphans to a minimum.
0:36:52 > 0:36:55They need to be as independent as possible ahead of their release.
0:37:03 > 0:37:06Although they're doing well,
0:37:06 > 0:37:10catching fast, wild fish in a big open lake or flowing river
0:37:10 > 0:37:13will present them with an enormous challenge.
0:37:19 > 0:37:23They'll need to bring all their knowledge and skills together.
0:37:34 > 0:37:39To reveal how otters do this, I'm heading to Oakland Zoo in California
0:37:39 > 0:37:44where I hope to film a hunt in super-slow motion.
0:37:44 > 0:37:49Here, they enrich the lives of the otters by feeding them live prey -
0:37:49 > 0:37:50goldfish.
0:37:51 > 0:37:56Helping me dissect the action is biology professor Lei Lani Stelle.
0:37:56 > 0:38:00Check this out, Lei Lani. What this will allow us to do,
0:38:00 > 0:38:04while the otter's swimming, I can track along with it and it shoots in
0:38:04 > 0:38:06really decent slow motion.
0:38:06 > 0:38:09We can basically slow things down ten times.
0:38:09 > 0:38:13Wow, that'll give us amazing detail on what they're doing right at the
0:38:13 > 0:38:16moment when they see their food and are able to catch it.
0:38:19 > 0:38:21- He's going for it.- Wow! That was nice, wasn't it?
0:38:24 > 0:38:26Look at them chasing it together.
0:38:28 > 0:38:31He's having trouble getting that one!
0:38:31 > 0:38:33Look at that!
0:38:33 > 0:38:35Got it.
0:38:35 > 0:38:40Awesome. OK, let's have a look, see what we've got.
0:38:40 > 0:38:42Where's the play button?
0:38:48 > 0:38:50That's so cool to see it in slow motion,
0:38:50 > 0:38:53so you can see all of the details of the moving.
0:38:53 > 0:38:56When we were watching it, it was so fast it was hard to see.
0:39:00 > 0:39:02It's incredibly agile, isn't it?
0:39:05 > 0:39:08Yeah, you can see him doing a really quick turn
0:39:08 > 0:39:13and you can definitely see how flexible his spine is.
0:39:13 > 0:39:16So it really is, I guess, the spine doing a load of work
0:39:16 > 0:39:20and then when he needs to get the fish, the back legs seem to come out.
0:39:22 > 0:39:25And that's how, I guess, how they get that turn of speed.
0:39:28 > 0:39:33The flexible spine combined with its tail and webbed hind feet
0:39:33 > 0:39:38allow the otter supreme agility and speed in the water.
0:39:40 > 0:39:44In the final approach, it uses its underwater eyesight
0:39:44 > 0:39:46to place the fish right in front of its head.
0:39:58 > 0:40:01That's right on the tail of the fish, isn't it?
0:40:01 > 0:40:03- He kind of nudged it with his nose first.- Yeah.
0:40:04 > 0:40:08It definitely seems like we're noticing that they're feeling the
0:40:08 > 0:40:09fish more than anything,
0:40:09 > 0:40:12so it may be that they're detecting it with
0:40:12 > 0:40:16their whiskers first and since that has a hard-wire
0:40:16 > 0:40:19from the whiskers right to the jaw,
0:40:19 > 0:40:21they can just bite it with instinct
0:40:21 > 0:40:24without having to take that time for the brain to process the signal.
0:40:25 > 0:40:27So they're not, you know, they're not feeling it
0:40:27 > 0:40:29and thinking, "Is that to my left? Is that to my right?"
0:40:29 > 0:40:33- Right.- It's like an instant...like us seeing or hearing.
0:40:33 > 0:40:37Yeah. Exactly, there's no delay. And that would explain how they're
0:40:37 > 0:40:39able to pick up on the fish so quickly.
0:40:39 > 0:40:42Because I would have trouble seeing the fish and they would already grab it.
0:40:42 > 0:40:44Right. And it is incredibly fast, isn't it?
0:40:49 > 0:40:51As soon as the prey touches the whiskers,
0:40:51 > 0:40:55an incredible nervous reaction is triggered.
0:40:55 > 0:41:00The signal fired to the brain is immediately turned into a command,
0:41:00 > 0:41:03stimulating the jaw to grab.
0:41:03 > 0:41:08Cutting out any decision-making delay.
0:41:09 > 0:41:12And it all happens in a fraction of a second.
0:41:18 > 0:41:22'But I've spotted something else intriguing in the footage.'
0:41:24 > 0:41:27That otter's nosing that fish and sniffing the fish, right?
0:41:29 > 0:41:33And if you look, when it first comes up to it, it puts bubbles out.
0:41:33 > 0:41:35- It's got loads of bubbles around its mouth.- Right.
0:41:35 > 0:41:38Because I'm convinced otters can smell underwater.
0:41:38 > 0:41:42So do you think the bubbles are going back into the nose or into the mouth?
0:41:42 > 0:41:44- I think they're going into both. - Interesting.
0:41:44 > 0:41:47It's not improbable because a lot of animals can smell
0:41:47 > 0:41:50underwater, right? And it's just a chemical cue
0:41:50 > 0:41:53and as long as it's concentrated, so it's really right close to them,
0:41:53 > 0:41:56it makes sense that they would still be able to smell it underwater.
0:41:59 > 0:42:01So other animals that can smell underwater,
0:42:01 > 0:42:06do they just sniff in water or do they use bubbles in this way?
0:42:06 > 0:42:09You know, to be honest, I don't think anyone knows.
0:42:11 > 0:42:16It's thrilling to think that otters' ability to smell underwater
0:42:16 > 0:42:18could in fact be an undiscovered survival skill.
0:42:21 > 0:42:25I've long thought otters must have this secret ability, and seeing
0:42:25 > 0:42:28this has inspired me to put my theory to the test.
0:42:36 > 0:42:40I'm hoping Rudy might be able to help me once again.
0:42:42 > 0:42:47So really the only definitive way of proving that otters can smell
0:42:47 > 0:42:49underwater is to do an experiment,
0:42:49 > 0:42:52so we're going to get some fake fish and some real fish
0:42:52 > 0:42:56and we're going to try and film Rudy telling the difference
0:42:56 > 0:42:58between the fake fish and real fish.
0:42:58 > 0:43:02So what we've got here is a fake piece of plastic trout.
0:43:04 > 0:43:08We're going to put that on here
0:43:08 > 0:43:11and we present Rudy with
0:43:11 > 0:43:14two identical-looking pieces of fish...
0:43:16 > 0:43:18..to see if he can tell the difference.
0:43:18 > 0:43:22So we're going to put this experimental block here...
0:43:23 > 0:43:24..underwater.
0:43:27 > 0:43:31'This relies on Rudy investigating each piece underwater.
0:43:33 > 0:43:35'Deciding which one is food and then eating it.
0:43:36 > 0:43:41'And Rod and I capturing the whole thing on camera in slow motion.'
0:43:46 > 0:43:48No interest in the fake one.
0:43:50 > 0:43:52Absolutely none.
0:43:58 > 0:44:00Well, come on, Rudy, do it.
0:44:02 > 0:44:04It's so fast and it's so subtle,
0:44:04 > 0:44:08that it's very difficult to work out exactly what's going on.
0:44:09 > 0:44:14'My camera simply isn't capable of slowing it down enough to see the finer details.
0:44:15 > 0:44:19'But Rod's camera captures the action 40 times slower than real life.'
0:44:22 > 0:44:24Right, Rod, did you get it?
0:44:24 > 0:44:25- Possibly.- Really?
0:44:25 > 0:44:30Yeah. It's so quick and obviously we're slowing it down 40 times,
0:44:30 > 0:44:33so until we actually see it...
0:44:33 > 0:44:36So that... God, that is a close shot. There's his head.
0:44:40 > 0:44:42That's a bubble coming out of his mouth, isn't it?
0:44:45 > 0:44:46Oh, he's sucked it back in.
0:44:46 > 0:44:48It's done it. No way.
0:44:48 > 0:44:50- That was it.- Fantastic.
0:44:50 > 0:44:51That's amazing.
0:44:52 > 0:44:54A bubble came out of his mouth
0:44:54 > 0:44:58and just as he was lifting his head, he sucked it right back in again.
0:44:58 > 0:45:00It wasn't his nose, but it was his mouth.
0:45:00 > 0:45:03He draws it back in, tasting the fish.
0:45:05 > 0:45:11That's amazing, because you can actually see it happening perfectly.
0:45:11 > 0:45:15'Rudy actively pushes a bubble onto the surface of the fish...
0:45:17 > 0:45:20'..picking up scent molecules before he sucks it back in...
0:45:22 > 0:45:26'..obtaining enough information to determine whether it's something he wants to eat.
0:45:28 > 0:45:32'This footage helps me understand how otters might find food in
0:45:32 > 0:45:37'dark, murky waters where they can't rely on their underwater eyesight.
0:45:38 > 0:45:41'They sniff it out.
0:45:41 > 0:45:44'It's amazing to think that an animal we are so familiar with...
0:45:46 > 0:45:47'..may still hold secrets from us.'
0:45:53 > 0:45:57And good to think that the orphans may have this ability too.
0:45:59 > 0:46:03The cubs are six months old now and autumn is coming.
0:46:03 > 0:46:05It's time for their release.
0:46:06 > 0:46:10With his parenting nearly over, Mark has built a pen...
0:46:11 > 0:46:14..which he'll leave on the shores of an isolated lake.
0:46:16 > 0:46:19'This will give the orphans somewhere familiar to come back to
0:46:19 > 0:46:22'until they're able to fend for themselves.'
0:46:22 > 0:46:23All set?
0:46:23 > 0:46:26Wow, this is the moment, guys.
0:46:26 > 0:46:27MARK WARBLES
0:46:30 > 0:46:34Oh, look at that.
0:46:36 > 0:46:38How amazing.
0:46:38 > 0:46:40You can't imagine what it's like. It's like...
0:46:40 > 0:46:41MARK WARBLES
0:46:41 > 0:46:44..having never been outside in your life, isn't it?
0:46:44 > 0:46:47Exactly. All these new, funny things to explore.
0:46:52 > 0:46:54They're so funny. They're just into everything.
0:46:54 > 0:46:55They run for about ten feet
0:46:55 > 0:46:57and then stop and look around and then they run.
0:46:59 > 0:47:01They're just crazy.
0:47:01 > 0:47:04They're checking everything out.
0:47:04 > 0:47:05Checking my tripod out.
0:47:14 > 0:47:17You know what's lovely is the point where they get to the water...
0:47:18 > 0:47:22..because they're suddenly going to be otters, finally.
0:47:22 > 0:47:25It's all very well looking like an otter,
0:47:25 > 0:47:26but to actually be free and be
0:47:26 > 0:47:29swimming and catching fish, that's the special bit.
0:47:52 > 0:47:56So this is the accumulation of all of our efforts coming to the end
0:47:56 > 0:47:59and this is the kind of moment we've been waiting for since we started.
0:48:03 > 0:48:06And gives you a lot of satisfaction to be able to see them out there,
0:48:06 > 0:48:09swimming and doing what they're doing...
0:48:10 > 0:48:12..knowing that you had a chance to set it right
0:48:12 > 0:48:15for what went wrong in the first place.
0:48:16 > 0:48:19We'll still continue to put food out for them
0:48:19 > 0:48:22but they need to find their independence now.
0:48:22 > 0:48:24And they're smart enough to do it.
0:48:24 > 0:48:26I mean, you're still kind of mum, aren't you?
0:48:26 > 0:48:27But you're a hands-off mum.
0:48:27 > 0:48:29Exactly.
0:48:29 > 0:48:33- Today we cut the apron strings a little bit.- Right.
0:48:33 > 0:48:38'And it's obvious that the orphans are relishing their first real taste of freedom.'
0:48:38 > 0:48:41They'll just keep expanding their range little by little and start
0:48:41 > 0:48:44checking things out and getting more adventurous
0:48:44 > 0:48:47and eventually they'll go probably around the whole lake
0:48:47 > 0:48:49and, not too much longer, they'll probably start heading
0:48:49 > 0:48:51up and down the creeks that are
0:48:51 > 0:48:53coming in and out and seeing what's there.
0:48:58 > 0:49:01'In the same way a mother otter would keep catching fish
0:49:01 > 0:49:03'for her young at this age in the wild...
0:49:04 > 0:49:06'..until Mark is sure that they're using
0:49:06 > 0:49:08'all their learned and innate skills
0:49:08 > 0:49:11'he'll keep putting out food for them.'
0:49:11 > 0:49:14And what happens, do you stop feeding them first and then they go
0:49:14 > 0:49:16or do they generally just move off?
0:49:16 > 0:49:20They generally just move off, so we'll offer food for a while until
0:49:20 > 0:49:22we notice the food's not disappearing any more
0:49:22 > 0:49:24and we don't see them any more.
0:49:25 > 0:49:27So it's their first night alone, now, isn't it?
0:49:27 > 0:49:30Yeah, it'll be the first night alone but I think they'll do just fine.
0:49:30 > 0:49:32They've had a lot of fun today and I think
0:49:32 > 0:49:34they're just going to find a place to go to sleep.
0:49:40 > 0:49:41I think they're going to sleep well.
0:49:41 > 0:49:44- I think so, too.- They got a good supper, they should be good.
0:49:46 > 0:49:50'As night falls, I can't help but worry for them.
0:49:50 > 0:49:53'Although Mark's provided them with food,
0:49:53 > 0:49:55'for the first time in their lives
0:49:55 > 0:49:57'they will have no-one looking out for them.'
0:50:11 > 0:50:14'As soon as it's light I'm keen to check up on the orphans.
0:50:20 > 0:50:25'At first there doesn't seem to be any sign of them.
0:50:32 > 0:50:35'But then I hear some familiar chirps.'
0:50:35 > 0:50:36CHIRPING
0:50:44 > 0:50:47'I'm delighted. All three are foraging together.'
0:50:57 > 0:51:02There's something about when you see a group of otters like this, you know,
0:51:02 > 0:51:05three otters almost like this one animal and three bodies.
0:51:05 > 0:51:10They move so perfectly, so in sync with each other.
0:51:10 > 0:51:12They know where each other is the whole time.
0:51:12 > 0:51:13They know what each other is doing.
0:51:13 > 0:51:15Even though sometimes they can't see each other.
0:51:15 > 0:51:18You know, this is really murky, peaty water.
0:51:18 > 0:51:23They can't see in it, but they always know where each other is.
0:51:30 > 0:51:34For Mark to have got them from three tiny cubs to this state
0:51:34 > 0:51:37and to put them in this place and release them so quickly
0:51:37 > 0:51:41and so effectively is brilliant. I think he's done a great job.
0:51:45 > 0:51:49Just looking at these guys from this canoe,
0:51:49 > 0:51:51it's just like watching a group of wild otters
0:51:51 > 0:51:53and they're doing everything that wild otters do.
0:51:53 > 0:51:55They're behaving like wild otters.
0:51:55 > 0:51:57They're hunting along in the reeds and the lilies
0:51:57 > 0:52:00along the edge of the lake.
0:52:00 > 0:52:03And they're foraging. That's what otters do.
0:52:03 > 0:52:06They're not always out in the middle of the lake speeding after fish.
0:52:06 > 0:52:09Most of the time they spend nosing around in the weeds
0:52:09 > 0:52:13trying to find some food, and that's exactly what these guys are doing.
0:52:13 > 0:52:15So it makes me very hopeful.
0:52:15 > 0:52:19You look at them behaving like real, wild otters and you think, well,
0:52:19 > 0:52:22if you can do that within 24 hours of being released,
0:52:22 > 0:52:25I think the chances of survival for these guys are pretty high.
0:52:31 > 0:52:34'Mark has given the orphans a real second chance at life.
0:52:36 > 0:52:39'And as long as they stick together,
0:52:39 > 0:52:42'harness everything their surrogate mum has taught them...
0:52:43 > 0:52:45'..alongside their own natural instincts,
0:52:45 > 0:52:48'they should be able to cope with most things.'
0:52:58 > 0:53:02I'm reassured that otters have what it takes to survive.
0:53:02 > 0:53:04History has shown this.
0:53:07 > 0:53:09Where otter populations were at record lows...
0:53:10 > 0:53:12..some are now coming back.
0:53:14 > 0:53:1940 years ago, the Eurasian otter was extinct across most of the UK.
0:53:21 > 0:53:23Now it's found in every county.
0:53:27 > 0:53:31And the sea otter numbered just 2,000 individuals a century ago.
0:53:34 > 0:53:39But with the help of protection and reintroduction programmes
0:53:39 > 0:53:43has made a population increase to 125,000.
0:53:48 > 0:53:50We can't get complacent.
0:53:50 > 0:53:54Across the globe otters ARE threatened,
0:53:54 > 0:53:58but where they're given the chance, they can adapt to a changing world.
0:53:58 > 0:53:59CHIRPING
0:53:59 > 0:54:04And there's one place where they've made a very surprising comeback.
0:54:11 > 0:54:13Downtown Singapore.
0:54:24 > 0:54:28Singapore is one of the busiest countries in the world.
0:54:30 > 0:54:34Attracting over 15 million visitors a year,
0:54:34 > 0:54:36it might not seem like a haven for wildlife.
0:54:38 > 0:54:40But despite the hustle and bustle,
0:54:40 > 0:54:44and having been thought extinct here just a few decades ago,
0:54:44 > 0:54:50in 2014, smooth-coated otters moved into the city centre.
0:54:54 > 0:54:57There are now thought to be well over 60 otters
0:54:57 > 0:54:59living inside the city state.
0:55:01 > 0:55:06The reason? Fresh water in Singapore's Marina Bay has,
0:55:06 > 0:55:09for the last nine years, been highly protected.
0:55:11 > 0:55:13There's next to no fishing or pollution.
0:55:16 > 0:55:20The result is a vast reservoir, absolutely full of fish.
0:55:23 > 0:55:24Perfect for otters.
0:55:28 > 0:55:30And now, on a daily basis,
0:55:30 > 0:55:33they demonstrate one of the characteristics I love most.
0:55:36 > 0:55:38Their close family bond.
0:55:43 > 0:55:45What's really freaking me out is that
0:55:45 > 0:55:49the last time I filmed a group of otters this big and this social
0:55:49 > 0:55:52and exciting was in one of the remotest parts of the Amazon.
0:55:52 > 0:55:56That was a group of giant otters, 15 of them.
0:55:56 > 0:56:00Now I've got 13 completely wild otters right in the middle of,
0:56:00 > 0:56:04I guess, one of the most densely populated cities on earth.
0:56:07 > 0:56:11'And this family has just expanded Singapore's population even further.
0:56:14 > 0:56:16'They have four 11-week-old pups.'
0:56:23 > 0:56:26'And just like the orphans in Wisconsin,
0:56:26 > 0:56:28'they, too, are on a journey of survival.'
0:56:47 > 0:56:49Otters are very sensitive animals.
0:56:49 > 0:56:52They've been in trouble across the world for a long time now.
0:56:52 > 0:56:56But, if Singapore proves anything to me, it's that they are adaptable.
0:56:57 > 0:57:00'I've no doubt otters are survivors.
0:57:04 > 0:57:07'For me, it's all about their supercharged nature.
0:57:09 > 0:57:13'And I think it's this that makes me smile every time I see one.
0:57:15 > 0:57:18'And here in Singapore there are plenty of other smiling faces.
0:57:20 > 0:57:25'That's because otters ARE special and, given a chance,
0:57:25 > 0:57:28'will always make the most of what's available to them.'
0:57:29 > 0:57:33They need nice, clean water, a decent supply of food,
0:57:33 > 0:57:36and they need to be free from persecution.
0:57:37 > 0:57:41And clearly, Singapore's provided them the perfect home.
0:57:47 > 0:57:52And that basically proves to me that these shy, nocturnal,
0:57:52 > 0:57:55secretive animals that we kind of all think otters are,
0:57:55 > 0:57:57give them the right ingredients for life...
0:57:59 > 0:58:01..protect them, and they'll thrive.
0:58:19 > 0:58:23And in the weeks and months following their release,
0:58:23 > 0:58:27through autumn and winter, the orphans in Wisconsin
0:58:27 > 0:58:28are also thriving.