0:00:02 > 0:00:05We live in a very weird world.
0:00:09 > 0:00:11And the more we discover about our planet,
0:00:11 > 0:00:13the stranger it gets.
0:00:14 > 0:00:17Every day, new stories reach us,
0:00:17 > 0:00:20stories that surprise us...
0:00:20 > 0:00:22What is that?!
0:00:22 > 0:00:24'..shock us...'
0:00:24 > 0:00:26PEOPLE EXCLAIM
0:00:26 > 0:00:29..sometimes even scare us.
0:00:29 > 0:00:30SCREAMING
0:00:30 > 0:00:32Oh, my God!
0:00:32 > 0:00:36We've scoured the globe to bring you the most curious creatures...
0:00:38 > 0:00:40..the most extraordinary people...
0:00:40 > 0:00:44I can stick almost anything to my skin without no glue.
0:00:44 > 0:00:46..and the most bizarre behaviour...
0:00:49 > 0:00:52..using eyewitness accounts and expert opinion
0:00:52 > 0:00:54to explore a weird world...
0:00:55 > 0:00:57..of unexplained underwater blobs...
0:00:59 > 0:01:01..flying goats...
0:01:02 > 0:01:03..and glow-in-the-dark fish.
0:01:06 > 0:01:09We examine the evidence,
0:01:09 > 0:01:10test the theories...
0:01:12 > 0:01:15..to work out what on earth is going on.
0:01:34 > 0:01:36In this episode,
0:01:36 > 0:01:40we'll discover some real-life cave-dwelling dragons...
0:01:42 > 0:01:44..unravel a shocking reindeer tragedy...
0:01:47 > 0:01:53..and encounter mysterious blood-red rain in Spain.
0:01:53 > 0:01:57- TRANSLATION:- We were scared because we didn't know what was happening.
0:01:59 > 0:02:00But first up,
0:02:00 > 0:02:02a collection of the world's sweetest
0:02:02 > 0:02:05and strangest love stories.
0:02:11 > 0:02:13Meet Klepetan,
0:02:13 > 0:02:15a male white stork.
0:02:16 > 0:02:19Every year, he flies from Africa
0:02:19 > 0:02:22to spend six months on this rooftop in east Croatia...
0:02:26 > 0:02:31..a journey of over 13,000km.
0:02:33 > 0:02:37Now of course, this in itself is not unique.
0:02:38 > 0:02:41Millions of bird species all around the world
0:02:41 > 0:02:42migrate with the warm weather,
0:02:42 > 0:02:45but you see, it's not why
0:02:45 > 0:02:48but who Klepetan makes this trip for
0:02:48 > 0:02:51that makes this stork story so special.
0:02:56 > 0:02:58This is Malena.
0:02:59 > 0:03:02Klepetan's mate.
0:03:02 > 0:03:04And every year, she waits patiently
0:03:04 > 0:03:06on their rooftop for him to arrive.
0:03:08 > 0:03:11It's a long-distance relationship
0:03:11 > 0:03:14that's lasted for 14 years
0:03:14 > 0:03:16and it's made them
0:03:16 > 0:03:18THE most famous couple in Croatia.
0:03:20 > 0:03:22- TRANSLATION:- Nothing bothers them,
0:03:22 > 0:03:24even the cameras,
0:03:24 > 0:03:27which have been recording this phenomenon of animal love.
0:03:27 > 0:03:30Their story has spread around the world.
0:03:30 > 0:03:32Look at this.
0:03:32 > 0:03:35The whole country is absolutely gripped
0:03:35 > 0:03:37by this tale of avian adoration.
0:03:37 > 0:03:39Who says romance is dead, eh?
0:03:42 > 0:03:45But there's something strange going on here...
0:03:46 > 0:03:48..because, well, our heroine
0:03:48 > 0:03:51isn't the classic choice for a mate.
0:03:51 > 0:03:56She's not able to do the one thing expected of a stork.
0:03:56 > 0:03:58She can't fly.
0:04:04 > 0:04:07The story starts back in 1993
0:04:07 > 0:04:10when school caretaker Stjepan Vokic
0:04:10 > 0:04:14found a female white stork on the side of the road.
0:04:14 > 0:04:16She'd been shot by a hunter
0:04:16 > 0:04:18and her wing was badly injured.
0:04:19 > 0:04:21Stjepan named her Malena,
0:04:21 > 0:04:22meaning "little one"
0:04:22 > 0:04:25and although he nursed her back to health,
0:04:25 > 0:04:27her wing never mended enough for her to fly.
0:04:27 > 0:04:32And so Stjepan decided to take Malena under his wing, permanently.
0:04:34 > 0:04:37Now, Stjepan didn't want Malena to miss out on motherhood
0:04:37 > 0:04:39because of her disability,
0:04:39 > 0:04:42so he built her a nest on his roof -
0:04:42 > 0:04:45and it was here that she was spotted by Klepetan.
0:04:50 > 0:04:53It was love at first sight.
0:04:55 > 0:04:57STORKS CHITTER
0:04:58 > 0:05:00And for 14 years,
0:05:00 > 0:05:03Klepetan has arrived on March the 24th,
0:05:03 > 0:05:06and he leaves six months later
0:05:06 > 0:05:08to fly off with the other storks back to Africa.
0:05:11 > 0:05:13- TRANSLATION:- To cover all that distance,
0:05:13 > 0:05:14and to come to the same place,
0:05:14 > 0:05:17that's quite something for our brains to comprehend.
0:05:17 > 0:05:19I'd get lost just trying to get to the nearby village.
0:05:22 > 0:05:23But poor old Malena,
0:05:23 > 0:05:25abandoned by her love?
0:05:25 > 0:05:28Well, actually, she's not alone for long.
0:05:30 > 0:05:31No. Whilst her mate's away,
0:05:31 > 0:05:34Malena moves back in with Stjepan.
0:05:37 > 0:05:39He catches her fresh fish,
0:05:39 > 0:05:42and she stays nice and warm in his house,
0:05:42 > 0:05:45watching stork documentaries.
0:05:45 > 0:05:47She's taken into care every winter,
0:05:47 > 0:05:52and stays at home whilst her partner migrates to Africa for the winter.
0:05:56 > 0:05:58And then put back on the nest
0:05:58 > 0:06:00every spring,
0:06:00 > 0:06:01and then the male comes back and...
0:06:01 > 0:06:05usually up to the hour of the arrival time of the previous year,
0:06:05 > 0:06:06and there she is to welcome him.
0:06:09 > 0:06:11- TRANSLATION:- When he landed, it was pure joy.
0:06:11 > 0:06:14I was relieved not to have to think about where he was.
0:06:14 > 0:06:16I immediately took him some fresh fish.
0:06:22 > 0:06:25So, why is Klepetan so devoted?
0:06:25 > 0:06:29What keeps him coming back to this one particular female?
0:06:29 > 0:06:33Well, it's all to do with Malena's alternative lifestyle.
0:06:36 > 0:06:37The fact that she's been resting
0:06:37 > 0:06:39and putting her feet up indoors all winter,
0:06:39 > 0:06:41and being fed, probably means
0:06:41 > 0:06:44she's in very, very good breeding condition compared to other birds
0:06:44 > 0:06:46who have made a long and risky migration.
0:06:46 > 0:06:50Whilst an average stork mother might hatch three or four chicks,
0:06:50 > 0:06:52Malena raises a full nest -
0:06:52 > 0:06:55at least five chicks every year.
0:06:57 > 0:06:59Even though, to you and I, she looks a bit damaged
0:06:59 > 0:07:00because she can't fly,
0:07:00 > 0:07:02to him, she's in fine form for breeding.
0:07:04 > 0:07:08And it's not just Malena that Klepetan's returning for.
0:07:08 > 0:07:11Stjepan is also a bit of a catch.
0:07:11 > 0:07:14He's built them their own shelter,
0:07:14 > 0:07:18to protect the eggs that Malena can't protect with her broken wing.
0:07:18 > 0:07:23He even travels over 30km to fish for food for the stork family.
0:07:24 > 0:07:28In fact, Klepetan has stopped going out to hunt.
0:07:28 > 0:07:31Instead, he prefers to have full board at Hotel Stjepan.
0:07:32 > 0:07:37Yes, Klepetan might have to fly 13,000km to get here,
0:07:37 > 0:07:40but life on this Croatian rooftop -
0:07:40 > 0:07:42well, it's pretty sweet.
0:07:50 > 0:07:52What a lovely story.
0:07:52 > 0:07:55Thanks to one man's care and kindness,
0:07:55 > 0:07:59this stork couple have produced chicks for the last 14 years.
0:07:59 > 0:08:01Top work.
0:08:03 > 0:08:07But whilst this love story played out in Croatia,
0:08:07 > 0:08:10a love triangle was uncovered
0:08:10 > 0:08:12in a South American forest.
0:08:15 > 0:08:182014, the Amazon.
0:08:18 > 0:08:21There is an insane amount of diversity out there -
0:08:21 > 0:08:23there's butterflies and beetles and spiders and ants -
0:08:23 > 0:08:26and you can't take two steps without, like, finding something.
0:08:30 > 0:08:32Aaron was conducting biological surveys
0:08:32 > 0:08:34when he stumbled across something
0:08:34 > 0:08:36he'd never seen before.
0:08:36 > 0:08:39I just sort of casually walked past this tree,
0:08:39 > 0:08:44and this tree had these yellow, bulby things popping out of the bark...
0:08:44 > 0:08:46And I don't know if it's a fungus
0:08:46 > 0:08:48or if it's a fruit produced by the tree.
0:08:48 > 0:08:52One tree was covered in small, yellow balls -
0:08:52 > 0:08:54each one the size of a pea.
0:08:56 > 0:08:58I thought at first, "This is just some fungus,
0:08:58 > 0:09:01"it's some weird fungus growing on the side of a tree,
0:09:01 > 0:09:02"probably nothing more."
0:09:02 > 0:09:03That was my first impression,
0:09:03 > 0:09:07"It's just some sort of weird-looking mushroom."
0:09:07 > 0:09:09To help him identify these strange spheres,
0:09:09 > 0:09:12Aaron sent photos to a number of botanists.
0:09:12 > 0:09:14Most were flummoxed,
0:09:14 > 0:09:17but one recognised the weird, yellow structures.
0:09:20 > 0:09:23I got this one e-mail back, and it was this botany professor,
0:09:23 > 0:09:26and he said, "Oh, I saw this for the first time
0:09:26 > 0:09:28"when I was a grad student working in South America.
0:09:28 > 0:09:32"It is actually a rare, parasitic plant."
0:09:32 > 0:09:34So, not a fungus at all,
0:09:34 > 0:09:37but something much stranger.
0:09:42 > 0:09:44Most of the world's plants get their energy
0:09:44 > 0:09:47from a process called photosynthesis.
0:09:47 > 0:09:50They produce sugars in the presence of sunlight,
0:09:50 > 0:09:52but this thing's different.
0:09:52 > 0:09:55It doesn't need to do that because it's a parasite.
0:09:55 > 0:09:56It gets its energy
0:09:56 > 0:09:58from the tree itself.
0:09:58 > 0:10:00But then, every now and again,
0:10:00 > 0:10:02it's got to burst out and reproduce.
0:10:03 > 0:10:07It only bursts out through the bark of its host plant about once a year,
0:10:07 > 0:10:10and that's when it flowers.
0:10:10 > 0:10:11So these odd, yellow bulbs
0:10:11 > 0:10:15are actually the flowers of this rare, parasitic plant.
0:10:15 > 0:10:17But that was just the beginning
0:10:17 > 0:10:19of some truly bizarre biology.
0:10:22 > 0:10:26When Aaron went back to the tree at night...
0:10:26 > 0:10:28he discovered small caterpillars
0:10:28 > 0:10:31munching on the yellow buds...
0:10:32 > 0:10:33..and they weren't alone.
0:10:41 > 0:10:43Every caterpillar you find on this tree,
0:10:43 > 0:10:45you'll find its own, like, designated ant.
0:10:47 > 0:10:53Each caterpillar had an ant companion drumming on its back.
0:10:56 > 0:11:00So what's going on here? Is this some sort of crazy ant orchestra?
0:11:00 > 0:11:03Is this a caterpillar massage parlour?
0:11:03 > 0:11:04Well, obviously not,
0:11:04 > 0:11:06but watch very closely
0:11:06 > 0:11:09because this is supremely interesting.
0:11:13 > 0:11:16After playing percussion on the caterpillar's back,
0:11:16 > 0:11:18a small drop of liquid emerges
0:11:18 > 0:11:20and the ant drinks it up.
0:11:20 > 0:11:23So, what's going on?
0:11:24 > 0:11:26The caterpillars have special organs
0:11:26 > 0:11:29that actually secrete, like, sugar water almost.
0:11:29 > 0:11:31It has sugars, it has amino acids -
0:11:31 > 0:11:33it's this really nice cocktail
0:11:33 > 0:11:34that they produce just for the ants.
0:11:40 > 0:11:42So, why are these caterpillars
0:11:42 > 0:11:45providing the ants with this sweet syrup?
0:11:45 > 0:11:46What's in it for the caterpillars?
0:11:46 > 0:11:48Well, the ants, you see,
0:11:48 > 0:11:50are the caterpillars' bodyguards.
0:11:50 > 0:11:52They're paying for protection,
0:11:52 > 0:11:54they're protecting them from parasites,
0:11:54 > 0:11:55hungry wasps,
0:11:55 > 0:11:57spiders, that kind of thing.
0:11:57 > 0:11:59This is an example of a relationship
0:11:59 > 0:12:02that we call myrmecophily.
0:12:02 > 0:12:03Myrmecophily -
0:12:03 > 0:12:05it means "ant lover".
0:12:09 > 0:12:13And Aaron just happened to be in the right place at the right time
0:12:13 > 0:12:15to stumble across this bizarre threesome.
0:12:17 > 0:12:19What's unusual about this
0:12:19 > 0:12:21is there are so many layers
0:12:21 > 0:12:23to this biological scenario.
0:12:23 > 0:12:24You have a tree,
0:12:24 > 0:12:27you have a parasite that lives inside of the tree,
0:12:27 > 0:12:30then you have a caterpillar that comes along to feed on these bulbs,
0:12:30 > 0:12:32and you have ants that take care of the caterpillars.
0:12:32 > 0:12:34Like, that's insane, right?
0:12:34 > 0:12:37So, there's this entire ecosystem going on in just this one tree.
0:12:39 > 0:12:44But there's one final, weird twist in this interconnected tale.
0:12:44 > 0:12:46While I was just watching
0:12:46 > 0:12:49this caterpillar-ant relationship going on,
0:12:49 > 0:12:51something happened that just blew my mind.
0:12:53 > 0:12:55There was a butterfly that landed on the tree.
0:12:55 > 0:12:58I realised that it had this wing marking,
0:12:58 > 0:13:00this yellow spot on its hind wing
0:13:00 > 0:13:03that looked exactly like this parasitic plant.
0:13:05 > 0:13:07Yes...
0:13:07 > 0:13:09The adult butterfly of the caterpillars
0:13:09 > 0:13:11that eat the parasitic, yellow bulbs
0:13:11 > 0:13:15have their image emblazoned on their wings.
0:13:18 > 0:13:21Now, it might just be a happy coincidence or camouflage,
0:13:21 > 0:13:23but, come on,
0:13:23 > 0:13:24it is totally weird.
0:13:29 > 0:13:31Incredible.
0:13:31 > 0:13:32Absolutely incredible.
0:13:32 > 0:13:35What an amazing collection
0:13:35 > 0:13:37of interconnected relationships.
0:13:37 > 0:13:39You know, I always say that science
0:13:39 > 0:13:43is the art of understanding truth and beauty,
0:13:43 > 0:13:45and the truth about this beauty
0:13:45 > 0:13:48is absolutely phenomenal.
0:13:50 > 0:13:53And clearly South America is a hotspot
0:13:53 > 0:13:55for stories of unusual ardour,
0:13:55 > 0:13:57because here we're staying,
0:13:57 > 0:14:00to listen out for a very peculiar serenade.
0:14:04 > 0:14:06Deep in the cloud forest of Ecuador...
0:14:07 > 0:14:09..at the foothills of the Andes,
0:14:09 > 0:14:13a strange sound rings out through the mist...
0:14:13 > 0:14:14TICKING
0:14:14 > 0:14:18INTERMITTENT, MONOTONOUS BEEPING
0:14:18 > 0:14:21And the animal responsible for this unusual call
0:14:21 > 0:14:23is not what you might expect.
0:14:26 > 0:14:30This is the club-winged manakin,
0:14:30 > 0:14:33and there's something seriously strange about its song.
0:14:35 > 0:14:37I saw the thing, I say,
0:14:37 > 0:14:38"Really? Is that really happening
0:14:38 > 0:14:41"or is it just my brain playing a trick on me?"
0:14:46 > 0:14:50There is nothing like it in the whole natural world.
0:14:50 > 0:14:53Joao had always been fascinated by the manakin's song
0:14:53 > 0:14:57and, in 2011, he trekked deep into the forest to capture it on camera.
0:15:01 > 0:15:03Every day, 4am in the morning,
0:15:03 > 0:15:05we used to walk about 3km,
0:15:05 > 0:15:07but it's like that,
0:15:07 > 0:15:10so it took us a few hours to get there.
0:15:10 > 0:15:12'I recognised the sound.'
0:15:12 > 0:15:14I said, "OK, it's the bird."
0:15:14 > 0:15:17He could hear the bird,
0:15:17 > 0:15:18but filming it sing -
0:15:18 > 0:15:21well, that was much more of a challenge.
0:15:21 > 0:15:23It was very frustrating at the beginning,
0:15:23 > 0:15:25because they move a lot,
0:15:25 > 0:15:27they never stay, for more than a couple of seconds,
0:15:27 > 0:15:29in the same place.
0:15:29 > 0:15:31But then...
0:15:31 > 0:15:32Bingo!
0:15:32 > 0:15:35The bird just landed in a perfect place.
0:15:37 > 0:15:39Now, watch this.
0:15:42 > 0:15:44TICKING, MONOTONOUS BEEP
0:15:44 > 0:15:46That sound...
0:15:46 > 0:15:49isn't coming from its throat.
0:15:49 > 0:15:51This bird sings
0:15:51 > 0:15:54with its wings.
0:15:54 > 0:15:55It's really hard to believe,
0:15:55 > 0:15:57when you see the bird lifting its wings
0:15:57 > 0:15:59and that thing happening,
0:15:59 > 0:16:01it's...nothing like it,
0:16:01 > 0:16:04there's nothing like it in the whole natural world.
0:16:04 > 0:16:07So, just how does it produce a note from its feathers?
0:16:09 > 0:16:12It's just a fantastic and fascinating sound.
0:16:15 > 0:16:17They hit their wings together,
0:16:17 > 0:16:18first, very briefly,
0:16:18 > 0:16:20so they make a tick -
0:16:20 > 0:16:22then they hit their wings together for a longer time period
0:16:22 > 0:16:24to make this drawn-out...
0:16:24 > 0:16:26toot.
0:16:26 > 0:16:27TICKING, BEEP
0:16:29 > 0:16:32Joao captured this movement in slow motion...
0:16:34 > 0:16:36..and you can clearly see the wings
0:16:36 > 0:16:39vibrate incredibly quickly.
0:16:40 > 0:16:44This bird is doing something called stridulating.
0:16:46 > 0:16:47On each wing,
0:16:47 > 0:16:51the club-winged manakin has one special feather,
0:16:51 > 0:16:53with a set of ridges along its central vein,
0:16:53 > 0:16:55and next to it another feather
0:16:55 > 0:16:58that acts like a pick.
0:16:58 > 0:16:59As the bird shakes the wing,
0:16:59 > 0:17:03these feathers rub against each other to make that sound.
0:17:08 > 0:17:11The pick feather hits a whole series of knobs on the file
0:17:11 > 0:17:14and rubs one way and then back again 100 times a second,
0:17:14 > 0:17:17and it hits 14 bumps each way as it goes.
0:17:17 > 0:17:20And so what this does, in combination,
0:17:20 > 0:17:23is it makes a pure tone - a 1.4 kilohertz tone.
0:17:26 > 0:17:28The club-winged manakin
0:17:28 > 0:17:32is the only species of bird, that we know, that stridulates.
0:17:35 > 0:17:36It's a very similar system
0:17:36 > 0:17:39to that used by grasshoppers and crickets.
0:17:39 > 0:17:42These insects rub their legs together
0:17:42 > 0:17:45to create that familiar chirping sound -
0:17:45 > 0:17:48and, just like these noisy neighbours,
0:17:48 > 0:17:50the manakin's display
0:17:50 > 0:17:53is all about impressing the ladies.
0:17:53 > 0:17:55To send a message to the female that they are there
0:17:55 > 0:17:58and they're a good mate.
0:17:58 > 0:18:02But why would a bird sing with its wings...
0:18:02 > 0:18:05rather than its voice box?
0:18:05 > 0:18:09Well, because that's what the female manakins like.
0:18:09 > 0:18:10It has to do with evolution.
0:18:10 > 0:18:14The females, for some reason,
0:18:14 > 0:18:16they choose to mate with males that produce that specific kind of sound.
0:18:16 > 0:18:19So, basically males that have that ability,
0:18:19 > 0:18:21they reproduce disproportionally more
0:18:21 > 0:18:25and, through their genes, they spread that trait in the population.
0:18:25 > 0:18:31I mean, imagine trying to vibrate your wings at 100 times a second.
0:18:31 > 0:18:33It would be exhausting.
0:18:34 > 0:18:38So, a female manakin can safely assume that, the better the song,
0:18:38 > 0:18:41the fitter and stronger the male.
0:18:46 > 0:18:50And Joao was certainly impressed.
0:18:50 > 0:18:53To be honest, I'm not a female manakin,
0:18:53 > 0:18:55but I was in love with that display.
0:18:55 > 0:18:58It was, like, the best day of my life.
0:18:58 > 0:19:02I couldn't believe that I saw and filmed that bird.
0:19:02 > 0:19:04Top bloke, and top bird.
0:19:08 > 0:19:11So, a mind-boggling love triangle...
0:19:13 > 0:19:15..the strangest serenade...
0:19:15 > 0:19:18and a long-distance avian relationship,
0:19:18 > 0:19:21supported by Stjepan.
0:19:21 > 0:19:22The course of true love,
0:19:22 > 0:19:25well, it's unbelievably weird.
0:19:28 > 0:19:30Next up -
0:19:30 > 0:19:33a collection of super-strange powers,
0:19:33 > 0:19:38a woman who could quite literally hear herself think
0:19:38 > 0:19:43and an animal with a secret, life-saving skill.
0:19:47 > 0:19:48But first,
0:19:48 > 0:19:50we head to Slovenia...
0:19:51 > 0:19:54..and a Postojna Cave park.
0:19:56 > 0:19:59Now, since 1823,
0:19:59 > 0:20:01tourists have flocked here
0:20:01 > 0:20:05to explore the park's eerie caverns.
0:20:05 > 0:20:08And for centuries, there have been tales of dragons
0:20:08 > 0:20:11living amongst the stalactites and stalagmites.
0:20:12 > 0:20:15And hiding out in the depths of the cave,
0:20:15 > 0:20:18this creature was believed to have been
0:20:18 > 0:20:20the dragons' spawn.
0:20:21 > 0:20:23In complete darkness,
0:20:23 > 0:20:25hidden between the rocks,
0:20:25 > 0:20:27lives the world's largest cave-dwelling animal.
0:20:31 > 0:20:34It's also the cave's top predator.
0:20:35 > 0:20:37Meet the olm,
0:20:37 > 0:20:41a type of amphibian called a salamander,
0:20:41 > 0:20:43peculiar, pale animals
0:20:43 > 0:20:46that live in the deepest, darkest depths of the caves.
0:20:48 > 0:20:52There were thought to be less than 100 wild olms in these caverns.
0:20:52 > 0:20:56They're so rare that few people have ever got a glimpse of one.
0:21:00 > 0:21:03I'm very sorry to say I don't have an olm -
0:21:03 > 0:21:05they're way too rare -
0:21:05 > 0:21:09but what I have got here is a creature called an axolotl
0:21:09 > 0:21:10and, just like olms,
0:21:10 > 0:21:11they're salamanders -
0:21:11 > 0:21:15and the two species share something else in common,
0:21:15 > 0:21:17they spent all of their lives in water.
0:21:17 > 0:21:21Of course, other species of salamander do leave the water
0:21:21 > 0:21:23and, over hundreds of years,
0:21:23 > 0:21:25they've given rise to all sorts of myths,
0:21:25 > 0:21:27some of them surrounding fire.
0:21:27 > 0:21:31It's said that they can resist the flames.
0:21:31 > 0:21:32Perhaps it's that
0:21:32 > 0:21:35that's given rise to those ideas of them being dragons.
0:21:41 > 0:21:44No-one knew much about these funny, little amphibians
0:21:44 > 0:21:46and so Saso and his team
0:21:46 > 0:21:48moved some wild individuals
0:21:48 > 0:21:50into an aquarium
0:21:50 > 0:21:52to learn more about their fantastic physiology.
0:21:55 > 0:21:57Olms don't have lungs.
0:21:57 > 0:22:02Instead, they absorb oxygen from the water through those feathery gills.
0:22:02 > 0:22:04They are completely blind.
0:22:04 > 0:22:06They use sensors around their mouth
0:22:06 > 0:22:08to pick up electrical impulses
0:22:08 > 0:22:09and track down their prey.
0:22:11 > 0:22:14The life of an olm is really a simple life.
0:22:14 > 0:22:17Try to find food, eat, conserve energy.
0:22:17 > 0:22:20Try to find a partner, mate.
0:22:20 > 0:22:22Conserve energy.
0:22:24 > 0:22:26And if they can't find food,
0:22:26 > 0:22:31olms are able to digest some of their own body.
0:22:31 > 0:22:34It can reach an age of around 100 years,
0:22:34 > 0:22:37survive without eating anything for ten years.
0:22:37 > 0:22:40And their unusual abilities don't stop there.
0:22:44 > 0:22:46Like the axolotl here,
0:22:46 > 0:22:49if the olm loses one of its legs,
0:22:49 > 0:22:52it can regrow it again from scratch.
0:22:52 > 0:22:53And this,
0:22:53 > 0:22:56coupled with the fact that no-one had ever seen one hatch
0:22:56 > 0:22:57or a young one,
0:22:57 > 0:23:01gave rise to the idea that olms were in fact immortal.
0:23:04 > 0:23:08Now, of course, Saso knew this couldn't be true
0:23:08 > 0:23:10but, in over 300 years,
0:23:10 > 0:23:13no-one had ever seen a baby olm.
0:23:15 > 0:23:18That was until 2016
0:23:18 > 0:23:21when Saso discovered this...
0:23:22 > 0:23:23..in his aquarium.
0:23:28 > 0:23:31I never thought I would see the egg of the olm.
0:23:32 > 0:23:35This little egg was big news...
0:23:37 > 0:23:39..a once-in-a-lifetime opportunity
0:23:39 > 0:23:42for Saso and his fellow biologists.
0:23:43 > 0:23:48It took the female 60 days to lay 52 eggs.
0:23:48 > 0:23:53Saso carefully transferred his precious clutch into a special tank.
0:23:55 > 0:23:59It was a moment where your hand was not allowed to shake.
0:23:59 > 0:24:01And four months later...
0:24:04 > 0:24:06..success.
0:24:13 > 0:24:16These are the first baby olms
0:24:16 > 0:24:18ever captured on camera...
0:24:22 > 0:24:25..and the Slovenians are so proud of their new discovery
0:24:25 > 0:24:29that they've taken these tiny dragons to their hearts.
0:24:29 > 0:24:32Yes, they've gone olm crazy.
0:24:37 > 0:24:40You know, I've always wanted to see an olm
0:24:40 > 0:24:43since I was a kid and I had them in my childhood encyclopaedias.
0:24:43 > 0:24:46Highly specialised animals, dead weird.
0:24:46 > 0:24:49It's a weekend in Slovenia for me.
0:24:53 > 0:24:55From tales of dragons,
0:24:55 > 0:24:59next up is a far more familiar animal -
0:24:59 > 0:25:01but one with a super-weird superpower.
0:25:05 > 0:25:07Back in 2009,
0:25:07 > 0:25:10Claire Guest was taking her dog for a walk.
0:25:10 > 0:25:12Something she did every day.
0:25:12 > 0:25:15I've had Daisy since she was a puppy and we're very, very close.
0:25:18 > 0:25:19But on this day,
0:25:19 > 0:25:21Daisy behaved very strangely.
0:25:24 > 0:25:27One day, we went out for a walk together, I had other dogs with me,
0:25:27 > 0:25:29and lifted the dogs out of the back of the car
0:25:29 > 0:25:32and they went off to run around the field, but Daisy wouldn't go.
0:25:32 > 0:25:34And she kept staring at me
0:25:34 > 0:25:36and then nudging at me, and nudging into my chest.
0:25:38 > 0:25:43Daisy was repeatedly sniffing and pawing at Claire's chest.
0:25:43 > 0:25:45Could she be trying to tell her something?
0:25:48 > 0:25:51The incident played on Claire's mind,
0:25:51 > 0:25:53so she decided to go and see a doctor
0:25:53 > 0:25:57and that was to be a life-changing decision.
0:25:57 > 0:26:01I was diagnosed with a very, very deep-seated breast cancer -
0:26:01 > 0:26:04which, if Daisy hadn't drawn my attention to it,
0:26:04 > 0:26:06would have almost certainly been life-threatening
0:26:06 > 0:26:08because it was so deep-seated
0:26:08 > 0:26:12that I wouldn't have felt it for a long time.
0:26:12 > 0:26:16Clever Daisy had sniffed out Claire's tumour,
0:26:16 > 0:26:17saving her life -
0:26:17 > 0:26:20which, in itself, is quite extraordinary.
0:26:22 > 0:26:24But it gets even weirder
0:26:24 > 0:26:27when you discover what Claire does for a living.
0:26:33 > 0:26:36The almost unbelievable irony here
0:26:36 > 0:26:38is that, just a few years earlier,
0:26:38 > 0:26:40Claire had set up a charity,
0:26:40 > 0:26:41Medical Detection Dogs,
0:26:41 > 0:26:44to train dogs to sniff out cancer.
0:26:47 > 0:26:48Claire has always been interested
0:26:48 > 0:26:51in training dogs for tasks involving scent.
0:26:55 > 0:27:00She was convinced that they could be used to sense human diseases.
0:27:02 > 0:27:05And now, she'd become part of her own story.
0:27:08 > 0:27:10When Daisy sniffed out Claire's tumour,
0:27:10 > 0:27:13it came at a crucial time.
0:27:13 > 0:27:14She was facing a lot of doubt
0:27:14 > 0:27:16from the medical profession.
0:27:17 > 0:27:19Following the early work that we'd done,
0:27:19 > 0:27:21there was a lot of scepticism
0:27:21 > 0:27:22and I could have given it up,
0:27:22 > 0:27:25but Daisy saving my life changed things again for me.
0:27:25 > 0:27:29It made me realise that, without the science of Daisy's nose,
0:27:29 > 0:27:31I may well not be here today -
0:27:31 > 0:27:33and it inspired me to keep going.
0:27:37 > 0:27:40Of course, we all love our canine companions -
0:27:40 > 0:27:43here are my two, what a couple of beauties -
0:27:43 > 0:27:46but how do we get dogs to diagnose cancer?
0:27:51 > 0:27:55Well, we already exploit the dog's amazing sense of smell,
0:27:55 > 0:27:57sniffer dogs at airports...
0:27:59 > 0:28:01..rescue dogs in disaster zones...
0:28:03 > 0:28:05..but medical detection dogs
0:28:05 > 0:28:09don't directly sniff out disease on human scent.
0:28:09 > 0:28:13They're trained to smell urine samples.
0:28:13 > 0:28:15We have a training area,
0:28:15 > 0:28:18and the training area has a surgical steel carousel,
0:28:18 > 0:28:20and this is where we put the samples onto.
0:28:22 > 0:28:24So, here are the eight samples.
0:28:24 > 0:28:27Only one of them indicates cancer.
0:28:29 > 0:28:32This clever canine sniffs each sample in turn,
0:28:32 > 0:28:35only stopping when she detects a positive result.
0:28:37 > 0:28:40It takes an amazingly short amount of time to screen the sample.
0:28:40 > 0:28:42In fact, if a sample is a negative sample,
0:28:42 > 0:28:44it takes under half a second.
0:28:44 > 0:28:47If it's a positive, it takes just under a second.
0:28:51 > 0:28:54Good girl. Good girl.
0:28:54 > 0:28:57Yay, good girl! Come on, then, Kiwi.
0:28:57 > 0:28:59Good girl.
0:28:59 > 0:29:02'Here, they are sniffing for prostate cancer
0:29:02 > 0:29:04'and the data is exciting.
0:29:04 > 0:29:08'These super sniffers are accurate over 90% of the time.'
0:29:15 > 0:29:19So, why do dogs have the ability to sniff out cancers?
0:29:19 > 0:29:22Perhaps, deep in their evolutionary past when they were hunting,
0:29:22 > 0:29:26it allowed them to sniff out the weak and the ill amongst their prey.
0:29:26 > 0:29:28Or perhaps, within the pack,
0:29:28 > 0:29:32it allowed them to sense any weakness in the alpha members.
0:29:32 > 0:29:35These days, of course, we are still a pack, we are the alpha members,
0:29:35 > 0:29:37and it's that
0:29:37 > 0:29:39that makes them unsettled.
0:29:40 > 0:29:44Now, training a dog to smell urine samples is one thing
0:29:44 > 0:29:45but, in Claire's case,
0:29:45 > 0:29:48where the cancer was hidden deep in the body,
0:29:48 > 0:29:50there's no physical sample to test.
0:29:52 > 0:29:54So, what was it that Daisy detected?
0:29:56 > 0:29:58Well, the team are still unsure
0:29:58 > 0:30:02but they think that it's most likely she smelt it on Claire's breath.
0:30:07 > 0:30:09And it is possible.
0:30:09 > 0:30:10A dog's nose, after all,
0:30:10 > 0:30:13is so much more sensitive than ours.
0:30:13 > 0:30:18We can detect the equivalent of a teaspoon of sugar in a cup of tea.
0:30:18 > 0:30:20But a dog, well,
0:30:20 > 0:30:22it can sniff out the same amount
0:30:22 > 0:30:24in two Olympic-sized swimming pools.
0:30:28 > 0:30:32And Claire is convinced that this extraordinary sense
0:30:32 > 0:30:33could be the answer
0:30:33 > 0:30:35to a faster diagnosis.
0:30:37 > 0:30:39If we can show that dogs can do that
0:30:39 > 0:30:41over a large sample size
0:30:41 > 0:30:42with a large number of patients,
0:30:42 > 0:30:45this could be something we could offer,
0:30:45 > 0:30:47a service that we could offer in the future.
0:30:51 > 0:30:53Why not use the power of a dog's nose,
0:30:53 > 0:30:55provided the dog's enjoying his work
0:30:55 > 0:30:57and he's giving a reliable answer?
0:31:00 > 0:31:04Dogs have the most remarkable biosensor,
0:31:04 > 0:31:06their nose,
0:31:06 > 0:31:09and sometimes you just can't improve on nature.
0:31:12 > 0:31:16Next up, a much more unwelcome super sense.
0:31:19 > 0:31:21March 2014.
0:31:22 > 0:31:24Indiana, America.
0:31:25 > 0:31:27Photographer Rachel Pyne
0:31:27 > 0:31:29was relaxing, watching TV,
0:31:29 > 0:31:33when she suddenly noticed something very strange.
0:31:35 > 0:31:37I could hear my eyeballs moving every now and then.
0:31:39 > 0:31:41I was just watching a TV show
0:31:41 > 0:31:43and I wasn't even moving my eyes
0:31:43 > 0:31:45but I heard them, like, screeching around
0:31:45 > 0:31:47and I'm like, "Mom, like, I don't know what...
0:31:47 > 0:31:50"I don't know what this is."
0:31:53 > 0:31:55Yes, that's right.
0:31:55 > 0:31:59Rachel could hear her eyeballs moving.
0:32:01 > 0:32:04And she was also troubled by other weird body sounds.
0:32:06 > 0:32:08My heartbeat
0:32:08 > 0:32:09I could hear constantly.
0:32:09 > 0:32:13It was like a "boom, boom, boom" all the time in my ears.
0:32:13 > 0:32:16I could hear my food going down my throat.
0:32:16 > 0:32:19I had some kind of ringing in my ears.
0:32:22 > 0:32:23Just imagine.
0:32:23 > 0:32:28Imagine hearing your eyeballs constantly moving in their sockets,
0:32:28 > 0:32:32your neck muscles creaking every time you move your head,
0:32:32 > 0:32:36your heart booming in your chest incessantly.
0:32:36 > 0:32:37It would be horrific.
0:32:40 > 0:32:43For Rachel, this wasn't just disconcerting,
0:32:43 > 0:32:45it was debilitating.
0:32:45 > 0:32:47As well as internal noises,
0:32:47 > 0:32:49Rachel also became super-sensitive
0:32:49 > 0:32:51to external sounds.
0:32:51 > 0:32:54Some would make her so dizzy she would pass out.
0:32:57 > 0:32:59Taking a shower, I'd fall almost every time
0:32:59 > 0:33:02cos the water hitting the floor
0:33:02 > 0:33:04just was really loud in my ears.
0:33:04 > 0:33:07Just going out to a store, I couldn't push a shopping cart -
0:33:07 > 0:33:09it was too loud, the wheels on it.
0:33:09 > 0:33:13It was a very worrying time for Rachel and her family.
0:33:13 > 0:33:15I actually ended up in the emergency room
0:33:15 > 0:33:18and they did a bunch of tests and said everything was normal,
0:33:18 > 0:33:19"Everything's OK, you can go back home,"
0:33:19 > 0:33:22but, to me, I knew my body and I knew that something was different.
0:33:22 > 0:33:25You know, something was wrong.
0:33:25 > 0:33:27The dizziness and super-sensitive hearing
0:33:27 > 0:33:29were taking over Rachel's life,
0:33:29 > 0:33:31so she consulted other doctors.
0:33:33 > 0:33:36Some doctors thought that it was some kind of inner ear...
0:33:36 > 0:33:39Just like an infection, maybe.
0:33:39 > 0:33:42And then it kind of went on to maybe it was migraines,
0:33:42 > 0:33:45even though I had no headaches.
0:33:45 > 0:33:47And a lot of doctors just said, "We don't know,
0:33:47 > 0:33:50"you might have to live with it."
0:33:50 > 0:33:54But Rachel couldn't just live with this mysterious affliction,
0:33:54 > 0:33:55its effects were overwhelming.
0:33:55 > 0:33:58I couldn't work as much as I used to
0:33:58 > 0:34:01and I couldn't hang out with family as much as I used to.
0:34:01 > 0:34:03I couldn't go out to eat, I couldn't go to the movies,
0:34:03 > 0:34:05I couldn't really do a whole lot.
0:34:05 > 0:34:06I couldn't even go to the mall.
0:34:06 > 0:34:09'Rachel was finally diagnosed with a rare condition
0:34:09 > 0:34:14'known as superior semi-circular canal dehiscence,
0:34:14 > 0:34:15'or SSCD.'
0:34:17 > 0:34:20SSCD is an extremely rare disease.
0:34:20 > 0:34:22In about 100,000 people,
0:34:22 > 0:34:23one person will have it.
0:34:28 > 0:34:32A lot of patients get told it's just in their head.
0:34:32 > 0:34:35The irony is that it truly is in their head,
0:34:35 > 0:34:37there's a small, tiny hole in the inner ear,
0:34:37 > 0:34:40between the inner ear and the brain...
0:34:40 > 0:34:44and if you stuck your finger in your ear, you would be in this space.
0:34:44 > 0:34:48That leads to the eardrum, the middle ear, and the inner ear -
0:34:48 > 0:34:50and the inner ear structures are the cochlea
0:34:50 > 0:34:52and your semi-circular canals.
0:34:52 > 0:34:55And if you look at your superior semi-circular canal,
0:34:55 > 0:34:56here,
0:34:56 > 0:34:58you can see that there's a clear hole.
0:34:58 > 0:35:01It wasn't until the year 2000
0:35:01 > 0:35:04that medical equipment, in the form of CT scanners,
0:35:04 > 0:35:06became sensitive enough
0:35:06 > 0:35:07to find these tiny holes
0:35:07 > 0:35:11between the inner ear and the brain.
0:35:11 > 0:35:13And up until that point, sufferers simply weren't believed.
0:35:13 > 0:35:16There was no name for this condition,
0:35:16 > 0:35:18and there was certainly not a cure.
0:35:20 > 0:35:22You'd go around telling people,
0:35:22 > 0:35:25"I have this disease, and I can hear my eyeballs move."
0:35:25 > 0:35:28A, if they don't believe you, they think you're crazy,
0:35:28 > 0:35:30and, B, once they believe you, they can't see it.
0:35:30 > 0:35:33You look perfectly normal,
0:35:33 > 0:35:35and yet you're suffering immensely.
0:35:35 > 0:35:37And do you know what? First of all,
0:35:37 > 0:35:40she had this incredibly rare condition.
0:35:40 > 0:35:44Secondly, the hole between her ears and her brain
0:35:44 > 0:35:48was much narrower than most people who suffer from SSCD.
0:35:48 > 0:35:50And thirdly,
0:35:50 > 0:35:53she had the condition in both of her ears.
0:35:54 > 0:35:57Rachel underwent pioneering brain surgery
0:35:57 > 0:36:00to close up the holes in her inner ears.
0:36:00 > 0:36:03Dr Yang operated on each ear separately,
0:36:03 > 0:36:06so Rachel endured two surgeries.
0:36:07 > 0:36:10I'm inside her skull, and I'll come down to this point,
0:36:10 > 0:36:13and I know that her hole is right there.
0:36:13 > 0:36:15'We do this small, dime-sized hole'
0:36:15 > 0:36:19to get down to the tiny hole between the inner ear and the brain.
0:36:19 > 0:36:21We fill it with a little bit of bone wax,
0:36:21 > 0:36:24we take a small piece of muscle as we're going in,
0:36:24 > 0:36:28and we take a small piece of bone that we fracture from the skull,
0:36:28 > 0:36:29and we cover this hole.
0:36:35 > 0:36:36- Hello.- Hi.
0:36:36 > 0:36:39- How are you doing?- Good. - Good to see you, how are you?
0:36:39 > 0:36:40Hello. I'm good.
0:36:40 > 0:36:42'After Rachel's operations,
0:36:42 > 0:36:45'she immediately noticed a difference.'
0:36:45 > 0:36:47'As soon as I woke up, I knew the dizziness was gone.
0:36:47 > 0:36:50'The second surgery actually cleared up all of,
0:36:50 > 0:36:52'like, the internal noises,
0:36:52 > 0:36:54'so that one actually took a couple of weeks'
0:36:54 > 0:36:57for me to start realising that those were gone
0:36:57 > 0:37:00and it was starting to be quiet in my head.
0:37:00 > 0:37:03Rachel is expected to make a full recovery.
0:37:03 > 0:37:05Life is really good now.
0:37:05 > 0:37:06I'm back to my usual things -
0:37:06 > 0:37:08I work my full-time job,
0:37:08 > 0:37:09I play with the nieces and nephews,
0:37:09 > 0:37:11I can do things with my family,
0:37:11 > 0:37:13go shopping, go out with my friends,
0:37:13 > 0:37:16so it's, like, completely back to how it used to be.
0:37:19 > 0:37:21It's incredible to think, isn't it,
0:37:21 > 0:37:23that such a small defect -
0:37:23 > 0:37:26one tiny, tiny little hole
0:37:26 > 0:37:27in someone's inner ear -
0:37:27 > 0:37:30could lead to such a massive amount of suffering?
0:37:35 > 0:37:37Immortal dragons,
0:37:37 > 0:37:39super sniffers and super hearing,
0:37:39 > 0:37:42all wonderfully weird superpowers...
0:37:45 > 0:37:47..but to finish,
0:37:47 > 0:37:50a collection of horror stories.
0:37:50 > 0:37:52Blood rain falling in Spain...
0:37:54 > 0:37:57..and a shocking tragedy in Norway.
0:37:59 > 0:38:03But first, a curious tale from Peru.
0:38:07 > 0:38:10The heart of the ancient Inca Empire,
0:38:10 > 0:38:14and home to a myriad of magical myths and mysterious legends.
0:38:16 > 0:38:20My grandfather tells me the story of Paititi.
0:38:23 > 0:38:25The Spaniards went into the Amazon,
0:38:25 > 0:38:27looking for the lost City of Gold.
0:38:28 > 0:38:32They come back with these stories of giant spiders that ate birds,
0:38:32 > 0:38:34trees so tall they blotted out the sun,
0:38:34 > 0:38:37and one of the details in this legend of Paititi
0:38:37 > 0:38:40was a river that boiled.
0:38:40 > 0:38:43Bird-eating spiders sound pretty exciting,
0:38:43 > 0:38:45but it was the boiling river
0:38:45 > 0:38:49that really captured young Andres's imagination.
0:38:50 > 0:38:53You know, at its widest, it gets to be at least eight metres wide.
0:38:53 > 0:38:55That caught my attention.
0:38:55 > 0:38:57It's probably about 90 degrees C.
0:38:57 > 0:38:59That caught my attention, too.
0:38:59 > 0:39:03Now, Andres grew up to be a geologist
0:39:03 > 0:39:06and, with this mythical river never far from his mind,
0:39:06 > 0:39:07he began to ask around.
0:39:09 > 0:39:11So, I started asking colleagues,
0:39:11 > 0:39:13people who should have known
0:39:13 > 0:39:16if there was a boiling river in the middle of the Amazon,
0:39:16 > 0:39:18and everyone said, overwhelmingly,
0:39:18 > 0:39:22"Very unlikely. No, man, sorry."
0:39:22 > 0:39:25But Andres refused to give up on the legend,
0:39:25 > 0:39:27so he went back to his family to ask for help.
0:39:30 > 0:39:34So, we're at a family dinner, and my aunt asks me about my research,
0:39:34 > 0:39:37and how it's going, and I tell her, "Hey, you know,
0:39:37 > 0:39:41"this river that boiled would have been cool, but it doesn't exist,"
0:39:41 > 0:39:43and she goes, "No, that's not true.
0:39:43 > 0:39:45"I've been there."
0:39:45 > 0:39:47So, in 2011,
0:39:47 > 0:39:51Andres and his aunt set out on an expedition
0:39:51 > 0:39:53to find the mythical river.
0:39:57 > 0:40:00Legend had it that the secret of its location
0:40:00 > 0:40:01is guarded by the Shaman,
0:40:01 > 0:40:03a Peruvian mystic.
0:40:05 > 0:40:08Andres would need to seek his permission.
0:40:08 > 0:40:11Ultimately, it was my aunt who led me into the jungle
0:40:11 > 0:40:14to go seek the blessing of the Shaman,
0:40:14 > 0:40:17so that I could go study their sacred river.
0:40:17 > 0:40:20Hours of trekking led them deep into the heart
0:40:20 > 0:40:22of the Peruvian Amazon.
0:40:22 > 0:40:24They crossed plenty of rivers,
0:40:24 > 0:40:25but none that boiled.
0:40:29 > 0:40:31Andres was about to give up on his boyhood dream...
0:40:33 > 0:40:35..when he turned a bend in the river
0:40:35 > 0:40:37to find something extraordinary.
0:40:42 > 0:40:45That much steam, at those high air temperatures,
0:40:45 > 0:40:47could only mean one thing.
0:40:47 > 0:40:49And all along the river bank,
0:40:49 > 0:40:52more, rather gruesome, evidence.
0:40:54 > 0:40:56Bodies.
0:40:56 > 0:40:58You're walking around and you'll see, you know,
0:40:58 > 0:41:01frogs, mammals, amphibians, birds, reptiles, whatever,
0:41:01 > 0:41:03that has fallen in and has not made it out.
0:41:05 > 0:41:07Had these animals boiled alive?
0:41:10 > 0:41:13Andres immediately took readings,
0:41:13 > 0:41:17and the temperature hit over 90 degrees centigrade.
0:41:25 > 0:41:28Yes, a boiling river.
0:41:28 > 0:41:29Not a legend, after all...
0:41:31 > 0:41:33..but an extraordinary discovery.
0:41:36 > 0:41:38But where had this super-strange,
0:41:38 > 0:41:40superheated river come from?
0:41:41 > 0:41:45Well, we do know that there are other hot bodies of water
0:41:45 > 0:41:48on our planet.
0:41:48 > 0:41:50Tourists relax in bath-like
0:41:50 > 0:41:5239-degree pools in Iceland.
0:41:54 > 0:41:57Monkeys in Japan enjoy a 40-degree soak
0:41:57 > 0:41:59during the freezing winter.
0:42:00 > 0:42:04But what these two hot bodies of water both have in common
0:42:04 > 0:42:06is their source.
0:42:09 > 0:42:11You see, most hot springs
0:42:11 > 0:42:13are the result of volcanoes.
0:42:16 > 0:42:21Magma, spewing from the centre of the Earth, superheats nearby water,
0:42:21 > 0:42:24creating hot pools and bubbling rivers...
0:42:27 > 0:42:29..but the nearest volcanic activity
0:42:29 > 0:42:32to the boiling river in Peru...
0:42:32 > 0:42:35Well, it's more than 700km away.
0:42:38 > 0:42:40So, where does the heat come from
0:42:40 > 0:42:43to boil all of this water?
0:42:43 > 0:42:44Well, it's easy to forget that -
0:42:44 > 0:42:48deep beneath our feet, at the core of the Earth -
0:42:48 > 0:42:52the temperature is 6,000 degrees centigrade.
0:42:52 > 0:42:54That's about the same temperature
0:42:54 > 0:42:56as it is on the surface of the sun.
0:43:01 > 0:43:04Water deep within the Earth's core -
0:43:04 > 0:43:05or in this case, a flask -
0:43:05 > 0:43:08is so hot that it rises.
0:43:09 > 0:43:12Like blood running through human arteries,
0:43:12 > 0:43:15it pushes its way through fault lines and cracks...
0:43:16 > 0:43:19..eventually emerging onto the surface of the Earth...
0:43:21 > 0:43:24..giving Andres his boiling river.
0:43:26 > 0:43:28And this Amazonian wonder
0:43:28 > 0:43:30flows hot for over 6km.
0:43:33 > 0:43:35It's up to 25 metres wide
0:43:35 > 0:43:38and five metres deep.
0:43:38 > 0:43:40It's simply huge,
0:43:40 > 0:43:42the world's largest thermal river.
0:43:48 > 0:43:50The local indigenous people
0:43:50 > 0:43:54have always known of the existence of this sacred river.
0:43:54 > 0:43:56They've called it the Shanay-timpishka
0:43:56 > 0:43:58which, in their language, means
0:43:58 > 0:44:00"Boiled by the heat of the sun."
0:44:00 > 0:44:02Although, perhaps it should be better called
0:44:02 > 0:44:04"Boiled by the heat of the Earth."
0:44:06 > 0:44:07But why here?
0:44:07 > 0:44:11Why has all of this superheated water surfaced in this spot?
0:44:15 > 0:44:20Well, Andres has made it his mission to find the answer,
0:44:20 > 0:44:24to finally discover the science behind the legend.
0:44:26 > 0:44:27It's amazing, you know,
0:44:27 > 0:44:29as you breathe in this hot vapour,
0:44:29 > 0:44:31you feel it going into your body
0:44:31 > 0:44:33and filling up your lungs.
0:44:33 > 0:44:36It is one of the most immersive experiences
0:44:36 > 0:44:40that I have ever been a part of.
0:44:51 > 0:44:55With a mythical mystery still under investigation in Peru,
0:44:55 > 0:44:57we head to Norway
0:44:57 > 0:44:59and a startling discovery.
0:45:01 > 0:45:04The Hardangervidda National Park,
0:45:04 > 0:45:07the largest high mountain plateau in northern Europe -
0:45:07 > 0:45:123,500 square kilometres of wilderness...
0:45:13 > 0:45:18..and home to over 10,000 wild reindeer.
0:45:18 > 0:45:20But, in August 2016,
0:45:20 > 0:45:22this remote moorland
0:45:22 > 0:45:24became the scene of a shocking event.
0:45:27 > 0:45:29More than 320 reindeer
0:45:29 > 0:45:33have been killed on a mountain range in the south of the country.
0:45:33 > 0:45:36A ranger found the dead animals on a hillside.
0:45:37 > 0:45:41323 reindeer, a whole herd...
0:45:43 > 0:45:46..including 70 calves, dead.
0:45:47 > 0:45:49It was a horrifying scene.
0:45:52 > 0:45:55The Norwegian nature inspectorate rushed to the park
0:45:55 > 0:45:58and took tissue samples.
0:45:58 > 0:46:02Earlier in the year, the first case of CWD,
0:46:02 > 0:46:04chronic wasting disease,
0:46:04 > 0:46:06a lethal illness that affects the brain,
0:46:06 > 0:46:09had been found in Norwegian reindeer.
0:46:09 > 0:46:13Could this new affliction be to blame?
0:46:13 > 0:46:15Well, the thing is, CWD
0:46:15 > 0:46:17doesn't affect calves
0:46:17 > 0:46:19and, in this mass event,
0:46:19 > 0:46:23both calves and adults were struck down.
0:46:23 > 0:46:24CWD?
0:46:24 > 0:46:26Definitely not.
0:46:26 > 0:46:29So how about hunting?
0:46:29 > 0:46:30GUNSHOT
0:46:30 > 0:46:33It is legal to hunt in this part of Norway,
0:46:33 > 0:46:35but scientists at the scene
0:46:35 > 0:46:37couldn't find a single gunshot wound.
0:46:38 > 0:46:40So, no wounds,
0:46:40 > 0:46:42no sign of disease.
0:46:42 > 0:46:46What on earth could have caused this sudden die-off?
0:46:46 > 0:46:49Well, there is one possible culprit.
0:46:49 > 0:46:53Something that's to blame for mass tragedies every year...
0:46:58 > 0:47:00..from thousands of fish in China,
0:47:00 > 0:47:03poisoned by a change in water quality,
0:47:03 > 0:47:07to vultures, maliciously targeted in South Africa.
0:47:08 > 0:47:11Poisoning, accidental or otherwise,
0:47:11 > 0:47:13kills hundreds of thousands
0:47:13 > 0:47:15of animals every year.
0:47:15 > 0:47:18But in the bodies of the reindeer...
0:47:18 > 0:47:19not a trace.
0:47:21 > 0:47:24So, if it wasn't down to disease
0:47:24 > 0:47:26or poisoning,
0:47:26 > 0:47:29what could have caused this mysterious mass death?
0:47:31 > 0:47:34When scientists examined the reindeer,
0:47:34 > 0:47:37they discovered something extraordinary.
0:47:40 > 0:47:42Each and every one
0:47:42 > 0:47:46had suffered from a sudden cardiac arrest.
0:47:46 > 0:47:49But what could stop 300 hearts simultaneously?
0:47:51 > 0:47:53Well, there is one thing powerful enough...
0:47:53 > 0:47:55THUNDER CRACKS
0:47:55 > 0:47:57..to cause this type of destruction.
0:48:00 > 0:48:03And days before the reindeer were found,
0:48:03 > 0:48:06the skies above Hardangervidda had been electrified.
0:48:08 > 0:48:12Lightning storms produce up to a billion volts,
0:48:12 > 0:48:14easily enough to stop a heart.
0:48:17 > 0:48:20Combining weather reports with the necropsy results,
0:48:20 > 0:48:21scientists concluded
0:48:21 > 0:48:23that this natural phenomena
0:48:23 > 0:48:25had to be the cause of death.
0:48:28 > 0:48:30But there's a problem.
0:48:30 > 0:48:34You see, these supercharged strikes leave their mark.
0:48:35 > 0:48:37But on the reindeer,
0:48:37 > 0:48:38not a single scratch.
0:48:40 > 0:48:43And we're not just talking about one animal here.
0:48:46 > 0:48:47How could lightning strike
0:48:47 > 0:48:50and kill quite so many animals at the same time?
0:48:54 > 0:48:57Well, the lightning didn't hit the animals directly,
0:48:57 > 0:49:02it hit the ground and radiated through the top layers of the Earth
0:49:02 > 0:49:04as a deadly ground current.
0:49:04 > 0:49:08Now, electricity likes to take the easiest path
0:49:08 > 0:49:11so, if a human had come into contact with this current,
0:49:11 > 0:49:15it would move up one leg and then back down the other,
0:49:15 > 0:49:16passing through the groin
0:49:16 > 0:49:18and most likely missing the heart.
0:49:20 > 0:49:22But having four legs -
0:49:22 > 0:49:23well, that's a different story.
0:49:23 > 0:49:27that gives the electricity more routes into the body,
0:49:27 > 0:49:29and, worse, the reindeer's hearts
0:49:29 > 0:49:32are also much closer to their legs,
0:49:32 > 0:49:35increasing the chance of the charge reaching the muscle
0:49:35 > 0:49:37and causing a cardiac arrest.
0:49:44 > 0:49:48The animals most likely huddled together for safety from the storm,
0:49:48 > 0:49:51tragically making the deadly ground current
0:49:51 > 0:49:53all the more effective,
0:49:53 > 0:49:56reaching all 323 reindeer
0:49:56 > 0:49:58in a matter of seconds.
0:50:00 > 0:50:02Of course, no-one likes to see
0:50:02 > 0:50:04hundreds of perfectly healthy animals
0:50:04 > 0:50:06cut down in their prime,
0:50:06 > 0:50:08but I can assure you of one thing,
0:50:08 > 0:50:10the electric shock that came from that lightning
0:50:10 > 0:50:14would have stopped their hearts beating in just a few moments,
0:50:14 > 0:50:16none of them would have suffered,
0:50:16 > 0:50:18and it does display the fact
0:50:18 > 0:50:20that the awesome power of nature
0:50:20 > 0:50:22can be devastatingly destructive.
0:50:26 > 0:50:29Yes, Mother Nature can surprise us
0:50:29 > 0:50:32with some pretty horrifying results,
0:50:32 > 0:50:34as our final story shows.
0:50:37 > 0:50:39Fuente Encalada,
0:50:39 > 0:50:41a sleepy Spanish village.
0:50:44 > 0:50:47Residents here live a traditional way of life...
0:50:48 > 0:50:50..and this is the water fountain,
0:50:50 > 0:50:52the heart of the community,
0:50:52 > 0:50:54where everyone gathers for a gossip.
0:50:55 > 0:50:57But, in November 2014,
0:50:57 > 0:50:59local residents woke up
0:50:59 > 0:51:01to something truly horrifying.
0:51:03 > 0:51:04Overnight,
0:51:04 > 0:51:06water in the fountain
0:51:06 > 0:51:08had turned blood red.
0:51:10 > 0:51:14- TRANSLATION:- We were scared because we didn't know what was happening.
0:51:16 > 0:51:20'At first, the villagers thought it might be secret sabotage.'
0:51:24 > 0:51:27- TRANSLATION:- We thought it was one lady in particular
0:51:27 > 0:51:30using a chemical to deter the kids, to stop them bathing.
0:51:34 > 0:51:36But one villager, Joaquin,
0:51:36 > 0:51:39noticed it had appeared after rainfall.
0:51:43 > 0:51:45- TRANSLATION:- I use buckets on my roof
0:51:45 > 0:51:49to catch the rainwater for watering the plants,
0:51:49 > 0:51:51but I realised that the water was red.
0:52:00 > 0:52:03Red rains have been documented for centuries.
0:52:03 > 0:52:06The Romans thought they were such an ill omen,
0:52:06 > 0:52:08they took a really drastic response.
0:52:08 > 0:52:11In 191 BC,
0:52:11 > 0:52:12the historian Livy
0:52:12 > 0:52:16writes that, after such a shower had drenched the Roman Senate,
0:52:16 > 0:52:19"the Fathers decreed that the consuls
0:52:19 > 0:52:21"should sacrifice full-grown victims
0:52:21 > 0:52:23"to whatever gods it seemed proper".
0:52:25 > 0:52:26Well,
0:52:26 > 0:52:28human sacrifice seems a bit extreme,
0:52:28 > 0:52:30doesn't it, really?
0:52:30 > 0:52:32And it's not very scientific either.
0:52:35 > 0:52:39But what does make the rain fall red?
0:52:40 > 0:52:42Well, we do know that dust from deserts
0:52:42 > 0:52:44can be whipped up into the atmosphere
0:52:44 > 0:52:46and carried thousands of miles.
0:52:57 > 0:53:00If there's enough iron oxide in the dust particles,
0:53:00 > 0:53:02it can fall as red rain,
0:53:02 > 0:53:05leaving a rusty residue in its wake.
0:53:07 > 0:53:09But in Spain,
0:53:09 > 0:53:12there was no dusty residue.
0:53:12 > 0:53:15The red water only appeared in puddles and pools.
0:53:16 > 0:53:18So, what was it?
0:53:21 > 0:53:23Joaquin had his own theories.
0:53:26 > 0:53:30- TRANSLATION:- At first, I thought it was from the paint on the building,
0:53:30 > 0:53:33but then I thought it might be chemicals from the local farmers.
0:53:35 > 0:53:37He collected some of the water
0:53:37 > 0:53:38and sent it off to be tested.
0:53:40 > 0:53:42I was completely astonished...
0:53:43 > 0:53:46..because I never saw something like that.
0:53:54 > 0:53:57When Javier looked at the samples under the microscope,
0:53:57 > 0:53:59he noticed something very strange.
0:54:01 > 0:54:03Some of them were moving.
0:54:03 > 0:54:05They are actually alive.
0:54:05 > 0:54:08Yes, these tiny cells
0:54:08 > 0:54:10are a freshwater microalgae
0:54:10 > 0:54:13called Haematococcus pluvialis
0:54:13 > 0:54:15and, when conditions are good,
0:54:15 > 0:54:16the algae is green.
0:54:16 > 0:54:18But when it becomes stressed
0:54:18 > 0:54:20by strong sunlight...
0:54:20 > 0:54:22it turns red.
0:54:22 > 0:54:25The sunlight and the UV rays
0:54:25 > 0:54:28are dangerous for this type of algae,
0:54:28 > 0:54:31so the algae produces pigment,
0:54:31 > 0:54:32astaxanthin,
0:54:32 > 0:54:35in order to protect itself
0:54:35 > 0:54:37from the sunlight.
0:54:38 > 0:54:41And here it is, Spain's blood rain,
0:54:41 > 0:54:44and you can see why people were concerned.
0:54:44 > 0:54:47Except that it's not blood at all, of course.
0:54:47 > 0:54:51This red colour is produced by a pigment called astaxanthin,
0:54:51 > 0:54:54and it's used by the algae
0:54:54 > 0:54:56to protect them from UV light.
0:54:56 > 0:54:57So, I know what you're thinking,
0:54:57 > 0:55:00"Hmm, it's pretty much sunny in Spain all the time,
0:55:00 > 0:55:04"so why haven't people seen this red algae before?"
0:55:07 > 0:55:09Well, here's the weird thing,
0:55:09 > 0:55:13this algae isn't normally found in Spain at all.
0:55:13 > 0:55:16In fact, Javier thinks it originated in America,
0:55:16 > 0:55:19some 6,000km away.
0:55:19 > 0:55:23So, how had it travelled so far?
0:55:23 > 0:55:28These algae are transported by the winds and dropped with the rain.
0:55:28 > 0:55:30Evaporation from lakes
0:55:30 > 0:55:34can allow the algae to get into the air,
0:55:34 > 0:55:40and then transport through thousands of kilometres by the winds,
0:55:40 > 0:55:44until it arrives here in Spain.
0:55:44 > 0:55:46Javier analysed the weather
0:55:46 > 0:55:47and the wind directions,
0:55:47 > 0:55:51and he thinks the algae came all the way across the Atlantic.
0:55:51 > 0:55:54So, the villagers' fountains hadn't been contaminated,
0:55:54 > 0:55:59they'd been transformed by a stressed-out American algae.
0:55:59 > 0:56:01But there's one final twist,
0:56:01 > 0:56:03this aggravated alga
0:56:03 > 0:56:04harbours a secret superpower.
0:56:06 > 0:56:09You know when you cut an apple in half,
0:56:09 > 0:56:11the flesh on the inside goes brown.
0:56:11 > 0:56:13Well, that's because it's oxidised
0:56:13 > 0:56:15when it comes into contact with the air.
0:56:15 > 0:56:18But look what happens if you put the other half of the apple
0:56:18 > 0:56:21into a solution of astaxanthin.
0:56:22 > 0:56:24It doesn't oxidise,
0:56:24 > 0:56:26for the very simple reason
0:56:26 > 0:56:28that astaxanthin is a powerful antioxidant.
0:56:28 > 0:56:31And we know the value of these antioxidants
0:56:31 > 0:56:34because we take them, typically in the form of vitamin C,
0:56:34 > 0:56:36to protect cells in our body,
0:56:36 > 0:56:38and that's exactly what's happening here.
0:56:38 > 0:56:42The algae is producing its own antioxidant,
0:56:42 > 0:56:44in the form of astaxanthin,
0:56:44 > 0:56:46to protect itself.
0:56:47 > 0:56:51And astaxanthin is a particularly strong antioxidant.
0:56:53 > 0:56:58It's more than 60 times stronger than vitamin C.
0:56:59 > 0:57:02In fact, the algae that fell in Spain
0:57:02 > 0:57:04is grown commercially
0:57:04 > 0:57:06and stressed on an industrial scale
0:57:06 > 0:57:09to harvest astaxanthin,
0:57:09 > 0:57:12which is then used in food supplements and cosmetics.
0:57:18 > 0:57:20So, far from being a bad omen,
0:57:20 > 0:57:23the red rain in Spain
0:57:23 > 0:57:24could actually...
0:57:25 > 0:57:29..contain the ingredients for a much longer and healthier life.
0:57:35 > 0:57:37Blood rain.
0:57:37 > 0:57:38Mass deaths.
0:57:38 > 0:57:40Boiling rivers.
0:57:40 > 0:57:41Horrifying tales
0:57:41 > 0:57:43with simple, scientific explanations.
0:57:50 > 0:57:51So, there you go.
0:57:51 > 0:57:53It seems there's almost no end
0:57:53 > 0:57:56to the baffling and bewildering array of events
0:57:56 > 0:57:58that our planet can throw at us.
0:57:58 > 0:58:02There's a cornucopia of the confusing and the crazy,
0:58:02 > 0:58:04a bounty of the bizarre
0:58:04 > 0:58:06and a profusion of the puzzling.
0:58:06 > 0:58:08You get my gist.
0:58:08 > 0:58:11The natural world is just plain weird.
0:58:12 > 0:58:13That's weird.
0:58:13 > 0:58:16Next time, we discover holes punched out of the sky...
0:58:18 > 0:58:21Oh, my jeez, look at that.
0:58:21 > 0:58:23..see that all that glitters isn't gold...
0:58:24 > 0:58:28..and find out why these chimps are cuddling up to rocks.