0:00:02 > 0:00:05We live in a very weird world.
0:00:09 > 0:00:13And the more we discover about our planet, the stranger it gets.
0:00:14 > 0:00:20Every day, new stories reach us, stories that surprise us...
0:00:20 > 0:00:22What is that?
0:00:22 > 0:00:23..shock us...
0:00:23 > 0:00:25- Whoa! That is so cool.- Oh, my God!
0:00:25 > 0:00:29..and sometimes, even scare us.
0:00:29 > 0:00:30Argh!
0:00:30 > 0:00:32Oh, my God.
0:00:32 > 0:00:37We'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 > 0:00:55Using eyewitness accounts and expert opinion to explore a weird world
0:00:55 > 0:00:59of unexplained underwater blobs,
0:00:59 > 0:01:02flying goats
0:01:02 > 0:01:04and glow-in-the-dark fish.
0:01:06 > 0:01:12We examine the evidence, test the theories,
0:01:12 > 0:01:15to work out what on earth is going on.
0:01:34 > 0:01:37In this episode - discover what made a monster wave
0:01:37 > 0:01:40appear out of nowhere.
0:01:40 > 0:01:43Oh, she's going.
0:01:43 > 0:01:48How vampires suddenly appeared in America's Great Lakes.
0:01:48 > 0:01:50There's nothing that can be done to stop these.
0:01:50 > 0:01:53And your way of life is in danger as well.
0:01:53 > 0:01:57And whether great white sharks really enjoy a bit of head-banging.
0:02:01 > 0:02:04And for our first dip into the world of weirdness,
0:02:04 > 0:02:05we head in to the seaside.
0:02:09 > 0:02:12Australia, 2015.
0:02:12 > 0:02:16A group of friends decide to pack their swimming gear and head to some
0:02:16 > 0:02:20rock pools on the picturesque coast 50km south of Sydney.
0:02:22 > 0:02:26It was quite a nice day, probably high 20s, very clear,
0:02:26 > 0:02:28sunny, warm day.
0:02:32 > 0:02:35Nothing out of the ordinary, so it wasn't wild weather or anything like
0:02:35 > 0:02:38that, so it was quite a nice day to go for a walk and then a swim.
0:02:38 > 0:02:43Sun, warm seas and calm, crystal clear water.
0:02:43 > 0:02:45What could possibly go wrong?
0:02:47 > 0:02:50We put our things down and decided that we'd go in one at a time,
0:02:50 > 0:02:53so Mika went in first.
0:02:55 > 0:02:58We were watching, Alex and I were watching him in the distance.
0:02:58 > 0:03:00And then,
0:03:00 > 0:03:03all of a sudden, we saw a really,
0:03:03 > 0:03:06really big wave coming from the background...
0:03:06 > 0:03:08Oh, get out!
0:03:08 > 0:03:11..which completely shocked us and we were standing there
0:03:11 > 0:03:14screaming out to Mika.
0:03:16 > 0:03:18Before we knew it,
0:03:18 > 0:03:24he and countless other people were being dragged along the rocks.
0:03:24 > 0:03:29I have never seen anything like that first hand and the force of it...
0:03:29 > 0:03:33The water reached us and we were metres and metres inland.
0:03:34 > 0:03:39I'd say it was probably two or three times higher than what I would have
0:03:39 > 0:03:42considered a big wave previously.
0:03:42 > 0:03:44The wave had taken everyone by surprise.
0:03:44 > 0:03:49And as the injured clambered their way back to the shore,
0:03:49 > 0:03:51the questions started flying.
0:03:52 > 0:03:56Everyone wanted to know where this freak wave had come from.
0:03:56 > 0:03:59And how could something like this appear from nowhere.
0:04:05 > 0:04:10Most of the waves that we see are either caused by swell or by wind
0:04:10 > 0:04:12blowing on the surface of the oceans.
0:04:12 > 0:04:16It's a bit like when I blow on this water, making the ripples.
0:04:18 > 0:04:21And of course, the stronger the wind, the bigger the waves.
0:04:25 > 0:04:27But here's the weird thing -
0:04:27 > 0:04:29on that day that Lisa and her friends
0:04:29 > 0:04:33decided to take a dip in the rock pools, there was no wind.
0:04:33 > 0:04:35It was perfectly calm.
0:04:35 > 0:04:38And weather can't change on a whim.
0:04:40 > 0:04:43On a calm day, all the waves would be small.
0:04:46 > 0:04:49And on a windy day, all the waves would be big.
0:04:49 > 0:04:51Not just one of them.
0:04:51 > 0:04:56So, if wind alone can't explain a single giant wave,
0:04:56 > 0:04:59did the blame lie with another force of nature altogether?
0:05:04 > 0:05:08When earthquakes happen near or under the sea,
0:05:08 > 0:05:12it triggers the mother of all monster waves - called a tsunami.
0:05:15 > 0:05:18In deep water, they're almost imperceptible.
0:05:18 > 0:05:21But a tsunami can cross entire oceans
0:05:21 > 0:05:24at speeds of up to 600mph.
0:05:27 > 0:05:29When they hit the shore, they slow down,
0:05:29 > 0:05:34allowing the fast-moving water behind to catch up and in this way,
0:05:34 > 0:05:37a huge wave can appear out of the blue.
0:05:43 > 0:05:46So, was this wave a tsunami?
0:05:46 > 0:05:47Well, no, it wasn't.
0:05:47 > 0:05:51You see, tsunamis are typically formed by seismic activity.
0:05:51 > 0:05:56They involve multiple waves and affect many miles of coastline.
0:05:56 > 0:05:58This wave was altogether different.
0:05:58 > 0:06:02It only affected a tiny part of the coast and it came and went very quickly.
0:06:02 > 0:06:06So, was it an anomaly, just a freak?
0:06:06 > 0:06:08Is that possible?
0:06:09 > 0:06:12Rogue waves, they're also called freak waves, extreme waves,
0:06:12 > 0:06:16giant waves. There's lots of different terminology for them
0:06:16 > 0:06:19and essentially, they are waves that appear within a sea state
0:06:19 > 0:06:23unexpectedly, substantially taller than any of the surrounding waves.
0:06:26 > 0:06:27They are quite hard to predict.
0:06:27 > 0:06:30Rogue waves do quite often appear from nowhere.
0:06:30 > 0:06:33There's different causes that can make them appear,
0:06:33 > 0:06:36so they can occur in any sea state, essentially.
0:06:37 > 0:06:40So, the wave at the Rock Falls wasn't unique.
0:06:40 > 0:06:43Giant waves can appear anywhere.
0:06:43 > 0:06:48Understanding how could help prevent a disaster, but then,
0:06:48 > 0:06:53understanding anything called a rogue or a freak is complicated.
0:06:56 > 0:06:58Hmm, yes.
0:06:58 > 0:07:00But why is it so complicated?
0:07:00 > 0:07:05Well, firstly, it's because we are dealing with a liquid and when you
0:07:05 > 0:07:08apply a force to a liquid, it changes shape,
0:07:08 > 0:07:11just like when I drop this marble in here.
0:07:11 > 0:07:13And at the point of the force touching the liquid,
0:07:13 > 0:07:18you can see the shape changing as those ripples radiate away.
0:07:18 > 0:07:22But how about if I apply multiple forces at the same time?
0:07:28 > 0:07:31Then what we've got is, effectively, chaos,
0:07:31 > 0:07:35with the ripples radiating from each one of those marbles,
0:07:35 > 0:07:39but also what we have is an enhanced probability that some of those
0:07:39 > 0:07:41ripples will meet...
0:07:45 > 0:07:50..to form waves, which are double the height of his single ripple.
0:07:50 > 0:07:54And basically, that's how we get rogue waves.
0:07:57 > 0:08:00Only the world isn't a fish tank.
0:08:00 > 0:08:04Our oceans are massive and cover 70% of the planet.
0:08:06 > 0:08:09Instead of lots of marbles, they have storms,
0:08:09 > 0:08:14all happening independently and separated by vast distances.
0:08:17 > 0:08:20Each storm creates waves that can travel for miles.
0:08:23 > 0:08:27When two of these waves meet, they can form a bigger wave,
0:08:27 > 0:08:28but there's more.
0:08:31 > 0:08:35Surging currents and an undulating sea floor also play a part.
0:08:37 > 0:08:39When all of these elements come together...
0:08:44 > 0:08:45..a rogue wave can form
0:08:45 > 0:08:49and that's what happened at the rock pools that day.
0:08:53 > 0:08:57Scientists know what ingredients are needed to make a rogue wave,
0:08:57 > 0:09:00but they just can't yet predict them.
0:09:01 > 0:09:06To work out the recipe, they need to analyse vast amounts of data,
0:09:06 > 0:09:10but the hope is that one day maths will provide the answer.
0:09:14 > 0:09:19In the meantime, Lisa has developed a new respect for the sea.
0:09:20 > 0:09:24It's definitely changed my relationship to the water.
0:09:24 > 0:09:26I thought I was quite confident swimmer
0:09:26 > 0:09:29and quite confident around the open ocean,
0:09:29 > 0:09:33but it's definitely changed the way I'll interact with
0:09:33 > 0:09:36the water and be wary of where I go to swim.
0:09:39 > 0:09:43Our oceans are phenomenal places.
0:09:43 > 0:09:46The sheer size and power can be intimidating.
0:09:46 > 0:09:48But, that said,
0:09:48 > 0:09:52I wouldn't let a rogue wave put you off from taking a dip in the sea.
0:09:52 > 0:09:55After all, these are rare events.
0:09:55 > 0:09:57The clue is in the name.
0:09:59 > 0:10:03With weather, it's always best to expect the unexpected.
0:10:03 > 0:10:08But sometimes, it can become so weird that it defies imagination.
0:10:11 > 0:10:16And that's what happened in the USA on Lake Michigan in May 2014.
0:10:19 > 0:10:23PhD Student Andrew Ballard has always used any free time
0:10:23 > 0:10:27as an excuse to go fishing with his dad.
0:10:27 > 0:10:30So, we got up really early and we drove here
0:10:30 > 0:10:34and we launched in a river just down the road, called Platte River.
0:10:36 > 0:10:38There's a funny saying in Michigan they say,
0:10:38 > 0:10:41"If you don't like the weather, just wait five minutes
0:10:41 > 0:10:43"and something better will come along."
0:10:43 > 0:10:47But with blue skies on the day in question, there was no need to wait.
0:10:49 > 0:10:53We motored out into the lake and we'd been fishing for a few hours
0:10:53 > 0:10:55and it was slow. The weather was nice, though.
0:10:55 > 0:10:57It was calm, there was not much wind.
0:10:57 > 0:10:59The weather wasn't calling for any storms or anything,
0:10:59 > 0:11:01so we didn't expect anything to happen.
0:11:01 > 0:11:04But we looked out to the west over the lake and we just thought it was
0:11:04 > 0:11:07a sort of cloud formation coming in or, you know,
0:11:07 > 0:11:09some weather front coming in.
0:11:13 > 0:11:16Something truly bizarre had happened to the weather.
0:11:16 > 0:11:21You see, what started out as a beautiful early summer morning
0:11:21 > 0:11:23was very rapidly obliterated.
0:11:26 > 0:11:29So, it wasn't until it was really close,
0:11:29 > 0:11:32we realised it wasn't just normal clouds.
0:11:33 > 0:11:37It was this, kind of, crazy, bizarre fog.
0:11:37 > 0:11:39"Crazy! Bizarre!"
0:11:39 > 0:11:41And hundreds of feet tall.
0:11:41 > 0:11:44A towering edifice of fog was looming over the flabbergasted
0:11:44 > 0:11:46fishermen.
0:11:47 > 0:11:50And it was about to swallow them whole.
0:11:51 > 0:11:54You see sandstorms over the desert
0:11:54 > 0:11:56and that is kind of exactly what it looked like.
0:11:58 > 0:11:59In all their years out fishing,
0:11:59 > 0:12:02they'd encountered fog many times before,
0:12:02 > 0:12:05but it had never looked like this.
0:12:05 > 0:12:07The effect was mesmerising.
0:12:11 > 0:12:14I was shooting the video and my dad was just staring at it,
0:12:14 > 0:12:16because we were just in general awe of it.
0:12:16 > 0:12:21It stretched as far as you could see, up and down the coast.
0:12:23 > 0:12:27The fishermen were about to be engulfed by a tsunami of fog
0:12:27 > 0:12:31that stretched the entire length of the lake.
0:12:31 > 0:12:34But it wasn't a unique case.
0:12:38 > 0:12:42The same freaky phenomenon has previously spooked residents of a
0:12:42 > 0:12:44town on the shore of Lake Huron.
0:12:45 > 0:12:49Looks like a tsunami's coming beside beach, dude.
0:12:52 > 0:12:54And, in San Francisco.
0:12:54 > 0:12:56It's swallowing me up!
0:12:56 > 0:12:59It's swallowing me!
0:12:59 > 0:13:02Even as far away as Taiwan.
0:13:07 > 0:13:10So, what was responsible for this monolithic murk?
0:13:11 > 0:13:14And why had it appeared on an otherwise
0:13:14 > 0:13:16perfect day on Lake Michigan?
0:13:19 > 0:13:25The phenomenon that people have described as a fog tsunami is like
0:13:25 > 0:13:31an enormous wave, but is made out of cloud.
0:13:31 > 0:13:36It can be seen travelling across the water,
0:13:36 > 0:13:39like an inundation, really.
0:13:44 > 0:13:45At the beginning of summer,
0:13:45 > 0:13:49the water in Lake Michigan
0:13:49 > 0:13:51can be cold still,
0:13:51 > 0:13:57whilst the land is being warmed up by the increased sunlight.
0:13:57 > 0:14:00If the water is cold enough,
0:14:00 > 0:14:04then when air blows onto it from the land,
0:14:04 > 0:14:07it can be cooled down to a sufficient degree
0:14:07 > 0:14:10that the moisture in the air turns into the droplets,
0:14:10 > 0:14:12which we see as fog.
0:14:15 > 0:14:19Fog appears when tiny water droplets form in the air
0:14:19 > 0:14:21and it can manifest itself in many ways.
0:14:23 > 0:14:26But Andrew had never seen anything as formidable
0:14:26 > 0:14:29as a fog tsunami before.
0:14:29 > 0:14:33So, what had given this particular fog its precipitous shape?
0:14:36 > 0:14:41When low air that is cold is advancing,
0:14:41 > 0:14:48you find that it can develop this very abrupt front edge,
0:14:48 > 0:14:52like the front bumper of a bumper car.
0:14:52 > 0:14:55This is because the cold air stays
0:14:55 > 0:15:01and sinks low to the surface and as it pushes the air ahead of it,
0:15:01 > 0:15:04it does so like a fist, really.
0:15:05 > 0:15:09A foggy fist of doom, perhaps.
0:15:09 > 0:15:11Well, no, not really.
0:15:13 > 0:15:15We couldn't see into it at all.
0:15:15 > 0:15:18It was really thick and completely opaque.
0:15:18 > 0:15:21Right before it engulfed us, we could feel a bit of cold mist,
0:15:21 > 0:15:23and right as it engulfed us,
0:15:23 > 0:15:26the temperature dropped pretty dramatically and it was misty.
0:15:26 > 0:15:29It didn't feel like rain, but you just felt
0:15:29 > 0:15:33like you were in the middle of a rain cloud, I guess.
0:15:33 > 0:15:37Clouds can often spoil a day out, but for Andrew and his dad,
0:15:37 > 0:15:40it was quite the opposite.
0:15:41 > 0:15:45It was beautiful and amazing
0:15:45 > 0:15:48and if it happened every time I went out fishing, I'd be all right.
0:15:48 > 0:15:52It would be inconvenient, but, you know, it would be pretty fun.
0:15:53 > 0:15:57So, fog can be strange, surprising,
0:15:57 > 0:16:00even surreal. At times irritating, or even dangerous.
0:16:00 > 0:16:03But on this occasion, for Andrew and his father,
0:16:03 > 0:16:05it was a truly remarkable spectacle.
0:16:12 > 0:16:15From stories of weird and wonderful weather,
0:16:15 > 0:16:19we now head off to meet some of nature's ultimate survivors.
0:16:24 > 0:16:27These are North America's Great Lakes.
0:16:29 > 0:16:31It looks placid here,
0:16:31 > 0:16:34but there's something sinister lurking beneath the surface.
0:16:38 > 0:16:42The Great Lakes fish are under attack from an animal that's
0:16:42 > 0:16:45scraping away their flesh to feed on the blood.
0:16:51 > 0:16:55Millions of fish have already died, which in turn,
0:16:55 > 0:16:59has caused panic in the fishing community.
0:16:59 > 0:17:01You'd see warnings from fishermen, say,
0:17:01 > 0:17:04out on Lake Michigan telling the people at Lake Superior,
0:17:04 > 0:17:06"Man, look at what happened to us down here."
0:17:09 > 0:17:13I hate to say it, but there's nothing that can be done to stop
0:17:13 > 0:17:17these and your way of life is in danger as well.
0:17:17 > 0:17:20People were determined to find out what was killing the fish.
0:17:20 > 0:17:23And what they discovered caused alarm.
0:17:26 > 0:17:28They found a bloodsucker
0:17:28 > 0:17:32that's been around since the time of the dinosaurs.
0:17:32 > 0:17:36A fish, albeit a very weird one, called a sea lamprey.
0:17:38 > 0:17:41So, this is a sea lamprey, it looks like an eel.
0:17:41 > 0:17:45They're not eels actually, they're their own family.
0:17:45 > 0:17:50A lamprey has a mouth that's suited to nothing better than feeding.
0:17:50 > 0:17:54It's a suction cup, so it's as strong as a suction cup.
0:17:54 > 0:17:58The mouth is ringed with sharp teeth and the middle of the mouth is a
0:17:58 > 0:18:02file-like tongue that flicks its way through the scales and skin of a
0:18:02 > 0:18:06fish, so that the lamprey is able to feed on the blood and body fluids of
0:18:06 > 0:18:10that fish. It'll go through about 40 pounds of fish during that parasitic
0:18:10 > 0:18:15phase, before it moves into a stream to spawn once and die.
0:18:15 > 0:18:19But why was a prehistoric predator suddenly inflicting its death hickey
0:18:19 > 0:18:21on the Great Lakes' fish?
0:18:26 > 0:18:29Sea lampreys are normally found here,
0:18:29 > 0:18:31down the Atlantic coast of North America.
0:18:31 > 0:18:36So, how on earth did they end up all the way inland over here?
0:18:37 > 0:18:40Well, incredibly, the answer lies with one of America's
0:18:40 > 0:18:42most famous landmarks.
0:18:44 > 0:18:49The Niagara Falls are an impassable natural obstacle.
0:18:49 > 0:18:52And they are the only thing stopping lampreys
0:18:52 > 0:18:54getting beyond Lake Ontario.
0:18:55 > 0:18:58Until we stepped in.
0:18:59 > 0:19:03In the 1920s, engineers opened the Welland Canal,
0:19:03 > 0:19:06linking Lake Ontario to Lake Erie.
0:19:08 > 0:19:11On the one hand, it was a great success -
0:19:11 > 0:19:15allowing ships to bypass the Niagara Falls, but on the other,
0:19:15 > 0:19:20it was a disaster, which opened the floodgates for lampreys.
0:19:23 > 0:19:26Lamprey made it past Niagara Falls in about 1920
0:19:26 > 0:19:30and made it all the way to Lake Superior by about 1939.
0:19:32 > 0:19:35Only 20 years after the new canal was opened,
0:19:35 > 0:19:40the lamprey had successfully invaded the entire Great Lakes basin.
0:19:46 > 0:19:48It was a perfect storm for invasion.
0:19:48 > 0:19:51They had an almost unlimited food supply, because there was abundant,
0:19:51 > 0:19:54succulent, tasty fish for the lamprey in the Lakes
0:19:54 > 0:19:56and there is nothing preying upon lamprey
0:19:56 > 0:19:58or keeping the lamprey in check.
0:19:58 > 0:20:00It was a free, open buffet for the sea lamprey.
0:20:06 > 0:20:10Plenty of food, perfect spawning grounds, no natural predators.
0:20:10 > 0:20:15The lampreys had slithered their way into paradise.
0:20:15 > 0:20:17Yes! Or, no.
0:20:17 > 0:20:20You see, for the people of the Great Lakes, these things were killers.
0:20:20 > 0:20:22A menace that had to be dealt with.
0:20:22 > 0:20:26So, whilst the rest of the world were gearing up for the Cold War,
0:20:26 > 0:20:29these folks were involved in a fishy fracas.
0:20:33 > 0:20:37And to show you how bad it got - prior to the lamprey invasion,
0:20:37 > 0:20:39the harvest of fish in Lake Michigan
0:20:39 > 0:20:42and Huron was about 20 million pounds annually.
0:20:42 > 0:20:44After the lamprey invasion,
0:20:44 > 0:20:47that fell to only a few hundred thousand pounds
0:20:47 > 0:20:49and that happened over the course of a relatively
0:20:49 > 0:20:52short amount of time.
0:20:52 > 0:20:54The lampreys were guzzling fish
0:20:54 > 0:20:57faster than a sea lion at a sushi bar.
0:20:57 > 0:20:59They were that bad.
0:20:59 > 0:21:01They were taking five times the amount of fish that humans
0:21:01 > 0:21:03were harvesting.
0:21:03 > 0:21:05It was make or break time.
0:21:05 > 0:21:09They had to find a way to bring this destructive predator under control.
0:21:10 > 0:21:12So, they threw everything at it.
0:21:13 > 0:21:18Starting with barriers and traps.
0:21:18 > 0:21:20They had to prevent the lampreys reaching
0:21:20 > 0:21:23or leaving their spawning grounds.
0:21:25 > 0:21:30When the traps on their own failed, they tried adding electricity.
0:21:30 > 0:21:34Unfortunately, some of those early attempts at lamprey control
0:21:34 > 0:21:37were quite... They were abject failures, actually.
0:21:37 > 0:21:41And in fact, some of the electrical barriers were very rudimentary,
0:21:41 > 0:21:44not much different, some say, than just throwing your toaster
0:21:44 > 0:21:47in the river and zapping whatever happens to be in there.
0:21:47 > 0:21:50So, the scientists switched to chemical warfare
0:21:50 > 0:21:52and developed a weapon that
0:21:52 > 0:21:56could kill lamprey without harming any other wildlife.
0:22:01 > 0:22:04A chemical called Lamprecide was the biggest breakthrough in the war
0:22:04 > 0:22:06against the lampreys yet.
0:22:06 > 0:22:09But the scientists couldn't rest on their laurels.
0:22:09 > 0:22:13At any point, the lampreys could develop a resistance to it.
0:22:13 > 0:22:16So, they'd won a battle, but to win the war,
0:22:16 > 0:22:20they'd have to exploit the lampreys' natural senses.
0:22:20 > 0:22:24The sea lamprey has a very refined sense of smell. In fact,
0:22:24 > 0:22:27most of their brain is for olfactory purposes.
0:22:27 > 0:22:29We call them swimming noses, because they're, basically,
0:22:29 > 0:22:33they have a very refined sense of smell.
0:22:33 > 0:22:35The scientists found that female lampreys
0:22:35 > 0:22:37are attracted to males by smell.
0:22:39 > 0:22:42So, they isolated the chemical responsible.
0:22:42 > 0:22:44Known as a pheromone,
0:22:44 > 0:22:49it was male lamprey cologne and it drove lady lampreys wild.
0:22:53 > 0:22:56This pheromone could be used to hoodwink the females
0:22:56 > 0:23:00into going into traps on the promise of a bit of hanky-panky.
0:23:00 > 0:23:03But there was even better news.
0:23:03 > 0:23:07You see, the scientist had managed to isolate the polar opposite
0:23:07 > 0:23:09to this attractant.
0:23:09 > 0:23:11A naturally occurring chemical called a necromone,
0:23:11 > 0:23:14a sort of eau de death,
0:23:14 > 0:23:17and the lampreys will do absolutely everything
0:23:17 > 0:23:19to avoid this death smell.
0:23:23 > 0:23:25Using these natural chemicals,
0:23:25 > 0:23:29scientists hope to create a push and pull effect,
0:23:29 > 0:23:31using necromones to push lamprey away from places
0:23:31 > 0:23:34they don't want them to be, like streams,
0:23:34 > 0:23:40with great spawning habitat, and pheromones to pull them into traps.
0:23:44 > 0:23:46That is the future of lamprey control, we think,
0:23:46 > 0:23:48in the Great Lakes basin.
0:23:48 > 0:23:50The use of these natural attractants that lamprey give off
0:23:50 > 0:23:54and we use it against them in their spawning phase.
0:23:54 > 0:23:57By turning their own senses against them,
0:23:57 > 0:24:00scientists finally had this slippery customer under control.
0:24:02 > 0:24:06We've gone from about two million lamprey in the Great Lakes
0:24:06 > 0:24:08to only a few hundred thousand
0:24:08 > 0:24:11and that's a significant drop in the lamprey numbers.
0:24:11 > 0:24:12It certainly is.
0:24:12 > 0:24:15But you have to give respect where it's due.
0:24:15 > 0:24:17This brilliant parasite,
0:24:17 > 0:24:20with its efficient if disturbing means of survival,
0:24:20 > 0:24:23has been giving human beings the run-around
0:24:23 > 0:24:25for almost 100 years.
0:24:25 > 0:24:30Since 1957, we've probably spent about 800 million or 900 million
0:24:30 > 0:24:32to control lamprey. But contrast that to the fact
0:24:32 > 0:24:36that the Great Lakes' fishery is worth 7 billion every year to
0:24:36 > 0:24:39the people of the US and Canada, and you can see it's a small price
0:24:39 > 0:24:42that we pay to have the fishery that we have.
0:24:42 > 0:24:44Without the sea lamprey control programme,
0:24:44 > 0:24:47we have no fishery to speak of.
0:24:52 > 0:24:57Those lampreys almost ruined the Great Lakes fishery.
0:24:57 > 0:25:00I've got to say, they got us out of a bit of a jam.
0:25:00 > 0:25:03You see, there's a long-held tradition in the UK
0:25:03 > 0:25:05that on the occasion of their jubilee,
0:25:05 > 0:25:08the reigning monarch is given a lamprey pie,
0:25:08 > 0:25:13except that here, lampreys are an endangered animal.
0:25:13 > 0:25:17But thankfully, the Canadians sent some over.
0:25:17 > 0:25:20And on the 60th anniversary of her reaching the throne,
0:25:20 > 0:25:24Queen Elizabeth was thus presented with a lamprey pie.
0:25:27 > 0:25:30History does not recount whether she ate it or not.
0:25:33 > 0:25:38Our next event takes place in the marshlands of the Negev desert
0:25:38 > 0:25:42in Israel, where a battle of a different kind is raging.
0:25:44 > 0:25:49Something here has an unhealthy appetite for toads and frogs -
0:25:49 > 0:25:51and not just their legs.
0:25:54 > 0:25:57Half-eaten amphibians are cropping up all over the place.
0:25:59 > 0:26:02But what's causing the slaughter?
0:26:02 > 0:26:08Well, a bizarre clue was discovered by a team of entomologists in 2005.
0:26:10 > 0:26:14What we found first were several toad specimens
0:26:14 > 0:26:17that were carrying larvae on their bodies.
0:26:17 > 0:26:20And because no-one had seen this before,
0:26:20 > 0:26:23at least in Israel,
0:26:23 > 0:26:27we didn't know what they are, so we took them to the lab.
0:26:31 > 0:26:35At first, we thought that this was completely incidental,
0:26:35 > 0:26:42that they were just larvae accidentally attached to the toads
0:26:42 > 0:26:47and we were sure that they would just drop off after a few hours.
0:26:48 > 0:26:52Gil and his team decided to keep the amphibians under observation
0:26:52 > 0:26:54and they didn't have to wait long
0:26:54 > 0:26:57before they made a macabre discovery.
0:27:01 > 0:27:05The researchers couldn't believe their eyes.
0:27:05 > 0:27:08The larvae weren't just hitching a ride,
0:27:08 > 0:27:11they were attacking their amphibian hosts.
0:27:13 > 0:27:17Only after we kept the toads and the larvae in the lab for a while,
0:27:17 > 0:27:19we noticed that the larvae kill the frogs.
0:27:21 > 0:27:25Frog after frog fell foul to their surprising assassin.
0:27:25 > 0:27:28It was clear that this was no accident of fate.
0:27:29 > 0:27:33When we thought that they are actually feeding on the toads,
0:27:33 > 0:27:35and they just didn't drop off, we said,
0:27:35 > 0:27:39"OK, this is something interesting. We should check it out."
0:27:41 > 0:27:43Things just didn't add up.
0:27:46 > 0:27:51Anything that's small and moving is normally fair game to an amphibian.
0:27:56 > 0:28:00The beetle larvae should be an easy meal,
0:28:00 > 0:28:03so how has this grisly grub turned the tables?
0:28:05 > 0:28:08Gil and his team had to find out.
0:28:10 > 0:28:14So, we went back to the field to collect more adults and more frogs
0:28:14 > 0:28:18carrying larvae to bring them back into the lab.
0:28:18 > 0:28:21Eventually, the larvae will complete their life cycle
0:28:21 > 0:28:24or complete the developmental stage.
0:28:24 > 0:28:27They will pupate and become beetles and we wanted to know what
0:28:27 > 0:28:29these beetles were.
0:28:30 > 0:28:35So, would this bizarre larvae emerge from its pupae as a grotesque adult
0:28:35 > 0:28:38beetle? Well, actually, no.
0:28:38 > 0:28:41It hatches out as a rather plain ground beetle.
0:28:41 > 0:28:43It's always the quiet ones, isn't it?
0:28:45 > 0:28:50This unassuming arthropod goes by the name of epomis circumscriptus.
0:28:53 > 0:28:56But why had such ordinary-looking beetles
0:28:56 > 0:28:59produced such diabolical babies?
0:29:00 > 0:29:02Well, Gil has a theory.
0:29:04 > 0:29:10We think that it evolved from some sort of counterattack,
0:29:10 > 0:29:14as some sort of defence.
0:29:14 > 0:29:17And throughout time,
0:29:17 > 0:29:22these larvae learned to utilise amphibians as food
0:29:22 > 0:29:24and started feeding on them and eventually,
0:29:24 > 0:29:28they just stopped feeding on everything else
0:29:28 > 0:29:31and fed exclusively on amphibians.
0:29:33 > 0:29:37The larvae weren't just fighting back any more,
0:29:37 > 0:29:40they were actively inviting the attack
0:29:40 > 0:29:43and in a truly remarkable way.
0:29:45 > 0:29:49It uses very minute behaviour,
0:29:49 > 0:29:52very minute movements to lure amphibians towards it.
0:29:52 > 0:29:57It moves its antennae and mandibles in a repeated cycle
0:29:57 > 0:30:02that entices the amphibians to approach and even to attack.
0:30:02 > 0:30:04By acting like a tasty snack,
0:30:04 > 0:30:08the epomis larvae had managed to turn the amphibian's
0:30:08 > 0:30:10own hunting instincts against them.
0:30:12 > 0:30:16And then it uses its double-hook mandibles to attach
0:30:16 > 0:30:20to the amphibian's body, to lock onto the skin.
0:30:20 > 0:30:22Once it is attached,
0:30:22 > 0:30:25it starts feeding on the amphibian's body fluids.
0:30:25 > 0:30:30And what's absolutely extraordinary is that a single greedy grub can
0:30:30 > 0:30:34chomp its way through nine frogs before it is ready to pupate.
0:30:37 > 0:30:41A dead frog looks like...
0:30:41 > 0:30:43Well, it doesn't look like a frog at all.
0:30:43 > 0:30:46It looks like a pile of bones,
0:30:46 > 0:30:49like someone just ate all the fleshy parts of the frog, the eyes,
0:30:49 > 0:30:54some of the skin and you get this almost perfect skeleton of bones.
0:30:54 > 0:30:57Sometimes it's a complete skeleton, sometimes it's just a pile of bones,
0:30:57 > 0:30:59with no shape at all.
0:31:05 > 0:31:09It's easy for us to see the frogs and toads as the victims here.
0:31:09 > 0:31:11But you've got to remember that
0:31:11 > 0:31:15during the course of their lifetimes, they eat thousands of
0:31:15 > 0:31:18insects without ever thinking about it.
0:31:18 > 0:31:20And the epomis beetle is the only species
0:31:20 > 0:31:26we've seen that completely reverses the predator prey role.
0:31:26 > 0:31:30So, it's unique and extremely weird.
0:31:34 > 0:31:39For our next story, we head north to the Arctic Ocean,
0:31:39 > 0:31:42where there's weirdness in abundance.
0:31:47 > 0:31:52Living amongst the sea ice are some of our planet's strangest animals.
0:31:55 > 0:31:59And perhaps oddest of all is the Greenland shark.
0:32:02 > 0:32:04At up to six metres long,
0:32:04 > 0:32:08Greenland sharks rival great whites in terms of size.
0:32:08 > 0:32:12But in comparison, very little is known about them.
0:32:13 > 0:32:16They live at amazing depths,
0:32:16 > 0:32:19often below the level that light can penetrate.
0:32:21 > 0:32:23So, not only are they hard to find,
0:32:23 > 0:32:26it's also a dangerous place to study them.
0:32:28 > 0:32:32But sometimes, these sharks are accidentally caught by fishermen.
0:32:34 > 0:32:36So, a team of marine biologists
0:32:36 > 0:32:40decided to make the most of a bad situation.
0:32:43 > 0:32:47In 2010, they set off in Denmark to investigate.
0:32:48 > 0:32:50Over the next three years,
0:32:50 > 0:32:54they would study every shark that they could get their hands on.
0:33:06 > 0:33:11Samples were frozen, so they could be examined later, back in the lab.
0:33:13 > 0:33:15The team didn't know it yet,
0:33:15 > 0:33:19but one of their discoveries would change the face of biology.
0:33:25 > 0:33:29No-one knew how long these remarkable animals live.
0:33:30 > 0:33:34Because sharks have a skeleton made of cartilage rather than bone,
0:33:34 > 0:33:37the usual method of carbon dating doesn't work.
0:33:39 > 0:33:42The biologists had to find another way of ageing them
0:33:42 > 0:33:46and they found the answer they were looking for in a remarkable place.
0:33:50 > 0:33:56The shark's eye contains proteins formed when it was an embryo.
0:33:56 > 0:33:59These can be carbon dated,
0:33:59 > 0:34:04so a sample was sent back to the lab and this was the chance to finally
0:34:04 > 0:34:06age these mysterious animals.
0:34:10 > 0:34:11When the results were analysed,
0:34:11 > 0:34:17the oldest shark was shown to be somewhere between 272
0:34:17 > 0:34:21and 512-years-old. Now,
0:34:21 > 0:34:24even if we plumped for somewhere in the middle of that range,
0:34:24 > 0:34:27that means there could be a shark living today
0:34:27 > 0:34:30that was born on the same day as Isaac Newton,
0:34:30 > 0:34:33that lived through the Great Fire of London,
0:34:33 > 0:34:35the English Civil War.
0:34:35 > 0:34:40There could be a shark out there that remembers England winning the
0:34:40 > 0:34:42World Cup!
0:34:42 > 0:34:46A shark hundreds of years old is extraordinary in itself.
0:34:46 > 0:34:50But this miraculous life-span is even more impressive
0:34:50 > 0:34:54when you realise what these deep sea survivors are up against.
0:34:57 > 0:35:01I would say they're living on the edge the whole time,
0:35:01 > 0:35:05in terms of tolerating the extremes of the cold,
0:35:05 > 0:35:09the extremes of pressure that they inhabit and also,
0:35:09 > 0:35:12actually finding the food that they need
0:35:12 > 0:35:15just for their general life and routines.
0:35:19 > 0:35:23So, it's literally a life of searching for food
0:35:23 > 0:35:27in a very hostile environment.
0:35:27 > 0:35:30Surviving in the cold and dark is impressive enough,
0:35:30 > 0:35:33but there's another bizarre twist to this tale.
0:35:36 > 0:35:39If you're searching for food in an environment like this,
0:35:39 > 0:35:42it would pay to have pretty good eyesight and I've got to tell you
0:35:42 > 0:35:45that when Greenland sharks are born they do have
0:35:45 > 0:35:48a perfectly respectable set of peepers.
0:35:48 > 0:35:52In fact, they've got larger eyes than most other species of shark,
0:35:52 > 0:35:57but as they grow up, something very weird happens.
0:36:01 > 0:36:05One of the amazing points of the Greenland shark,
0:36:05 > 0:36:08a very unique characteristic that we don't see
0:36:08 > 0:36:09in any other shark species,
0:36:09 > 0:36:15is a parasitic copepod that is embedded into the eyes
0:36:15 > 0:36:19of this particular species and this is extremely common,
0:36:19 > 0:36:22particularly in the mid to high Arctic.
0:36:22 > 0:36:25All of the Greenland sharks that you'll encounter
0:36:25 > 0:36:31have this particular parasite that's embedded into the eye.
0:36:31 > 0:36:34Copepods are tiny crustaceans.
0:36:34 > 0:36:38Most are drifters and spend their lives hanging out in the plankton.
0:36:38 > 0:36:43But one, called Ommatokoita, has decided to settle down
0:36:43 > 0:36:46on the Greenland shark's eyeball.
0:36:47 > 0:36:53The parasitic copepod actually anchors right inside the central
0:36:53 > 0:36:55part of the eye.
0:36:55 > 0:36:59It's got an anchor system, which is called a bulbar, that locks into
0:36:59 > 0:37:05the eye and the thought is that the parasite actually feeds off the
0:37:05 > 0:37:07surface of the eye itself.
0:37:08 > 0:37:13So, how does a blind shark survive in these Arctic conditions
0:37:13 > 0:37:16for hundreds of years? Well,
0:37:16 > 0:37:20it appears that it might benefit from the misfortune of others.
0:37:22 > 0:37:27We assume the Greenland shark is a scavenger and it is thought that it
0:37:27 > 0:37:30obtains most of the larger prey items from dead animals
0:37:30 > 0:37:33that have fallen to the sea floor.
0:37:33 > 0:37:37And therefore, if you're going to feed in that particular way,
0:37:37 > 0:37:39you obviously need an extraordinarily good
0:37:39 > 0:37:43sense of smell to be able to navigate around
0:37:43 > 0:37:45and locate those food falls.
0:37:45 > 0:37:48Although the Greenland shark has large eyes and they're potentially
0:37:48 > 0:37:52adapted in some way for these very low light levels,
0:37:52 > 0:37:57I think that the Greenland shark is not majorly dependent
0:37:57 > 0:38:00on vision as a cue to locate prey.
0:38:08 > 0:38:12Ladies and gentlemen, I give you the Greenland shark.
0:38:12 > 0:38:15What an animal, what an animal.
0:38:15 > 0:38:19Not only can it lose its vision and live on for hundreds of years,
0:38:19 > 0:38:25it's probably the oldest living vertebrate on planet Earth.
0:38:25 > 0:38:29It has to be nature's greatest survivor.
0:38:33 > 0:38:37We've seen how animals can adapt and survive,
0:38:37 > 0:38:40even in the most extreme situations.
0:38:40 > 0:38:44But next up, we meet a man who has to cope
0:38:44 > 0:38:47with his own rather surreal senses.
0:38:50 > 0:38:54Englishman James Wannerton doesn't just see the world differently
0:38:54 > 0:38:57to most of us, he tastes it.
0:39:01 > 0:39:06What happens is I get one of my senses stimulated, my hearing,
0:39:06 > 0:39:09and that immediately gets translated into a taste for me.
0:39:13 > 0:39:16It's a real mouth thing as well, it's not, not an association.
0:39:16 > 0:39:20It's actually a mouth thing. It's as if I'm actually eating something.
0:39:20 > 0:39:23Yes, James can taste words.
0:39:23 > 0:39:27And what's more, he's had this peculiar ability since childhood.
0:39:30 > 0:39:35I used to go on the tube train with my mum and I used to read off the
0:39:35 > 0:39:37names of the stations as we passed through them
0:39:37 > 0:39:40and each of the stations had a unique
0:39:40 > 0:39:42and distinct taste and texture.
0:39:42 > 0:39:47We used to travel on the Central line which was my tastiest line,
0:39:47 > 0:39:49it was lovely. Not all these tastes are nice,
0:39:49 > 0:39:51there were a few stations that were pretty horrible.
0:39:51 > 0:39:54Bond Street is one. It's got the taste and texture of
0:39:54 > 0:39:56something similar to hair spray.
0:39:56 > 0:39:58Tangy.
0:39:59 > 0:40:01It's horrible.
0:40:02 > 0:40:05Most people's senses work independently,
0:40:05 > 0:40:10so why is James' sense of taste triggered by the sound of a word?
0:40:11 > 0:40:15Could it be something to do with the one organ that has to interpret
0:40:15 > 0:40:19everything that we see, hear, taste, touch and smell?
0:40:21 > 0:40:24Imagine that this is my brain.
0:40:24 > 0:40:29It allows me to get around and make sense of the world and each part of
0:40:29 > 0:40:32that brain is ascribed a specific task
0:40:32 > 0:40:35and you need all of those parts for it to function properly.
0:40:36 > 0:40:40Let's imagine that the lemon is damaged in an accident,
0:40:40 > 0:40:44then I may not be able to recognise myself in a mirror.
0:40:44 > 0:40:47And if the apple becomes diseased,
0:40:47 > 0:40:51I then think that my left hand belongs to someone else.
0:40:51 > 0:40:54Now these are not amusing anecdotes,
0:40:54 > 0:40:56these are neurological conditions
0:40:56 > 0:41:01that have been recorded by doctors and what they tell us is that when
0:41:01 > 0:41:05the brain is damaged, things get taken away.
0:41:05 > 0:41:09But in James' case it's not about being taken away,
0:41:09 > 0:41:13it's that he's got extra perceptions.
0:41:13 > 0:41:17So, is it a case that James' brain, effectively,
0:41:17 > 0:41:19has more fruit not less?
0:41:22 > 0:41:26To the best of our knowledge, there seemed to be perhaps extra or
0:41:26 > 0:41:30strengthened connections between the area of his brain that processes
0:41:30 > 0:41:33words and the area that processes tastes.
0:41:37 > 0:41:42And there are neurons firing from the word portion of his brain to the
0:41:42 > 0:41:43taste portion of his brain
0:41:43 > 0:41:47and that causes him to have this extra perception.
0:41:47 > 0:41:50So, James' brain doesn't have extra fruit,
0:41:50 > 0:41:55just extra connections between the fruit and this allows some of his
0:41:55 > 0:41:57senses to talk to each other.
0:41:57 > 0:42:01It's like an eye dropper of taste, you know, just drops.
0:42:01 > 0:42:03Just drip-drops, one after the other...
0:42:03 > 0:42:06- HE IMITATES EYE DROPS FALLING - ..for every single sound I hear.
0:42:06 > 0:42:12This fantastic neurological phenomenon is called synaesthesia.
0:42:12 > 0:42:16The vast majority of the synaesthetic tastes
0:42:16 > 0:42:20that I experience are from childhood. A lot of them are sweets,
0:42:20 > 0:42:25things like wine gums and sweets you can't buy any more.
0:42:25 > 0:42:29So, does James' childhood offer a clue to where his curious condition
0:42:29 > 0:42:31came from?
0:42:33 > 0:42:38So, the general idea is that perhaps synaesthetes have some
0:42:38 > 0:42:44genetic difference that causes either extra connections
0:42:44 > 0:42:46or a lack of pruning of connections.
0:42:46 > 0:42:51So, when we're born, we have lots of neural connections
0:42:51 > 0:42:55and throughout time, those neural connections get pruned down
0:42:55 > 0:42:58to the ones that are meaningful for us.
0:42:59 > 0:43:02In every newborn baby's brain,
0:43:02 > 0:43:04represented by this bunch of bananas,
0:43:04 > 0:43:07the senses are better connected.
0:43:07 > 0:43:11But we don't need all of these connections to understand the world,
0:43:11 > 0:43:16so gradually, one by one, they are severed.
0:43:16 > 0:43:19The difference, however, with James' brain is that
0:43:19 > 0:43:22one of these connections remains intact,
0:43:22 > 0:43:25the one between the piece that processes words
0:43:25 > 0:43:28and the piece that processes tastes.
0:43:28 > 0:43:30And that is mind-boggling.
0:43:32 > 0:43:37So, what if some brilliant brain surgeon discovered a way of snipping
0:43:37 > 0:43:41James' extra neural connections now,
0:43:41 > 0:43:46freeing him from these strange synaesthetic sensations forever?
0:43:46 > 0:43:48Would he do it?
0:43:48 > 0:43:49I couldn't imagine life without it.
0:43:49 > 0:43:52And I think most synaesthetes would say the same.
0:43:54 > 0:43:59Fantastic. And although this might read as faulty wiring,
0:43:59 > 0:44:02in my opinion, this is as close as a human can come
0:44:02 > 0:44:05to having a proper superpower,
0:44:05 > 0:44:10so I couldn't resist asking James what my name tasted like.
0:44:10 > 0:44:12Do you know what he said?
0:44:13 > 0:44:14Soggy crisps.
0:44:14 > 0:44:16Soggy crisps!
0:44:16 > 0:44:18So much for the superpower.
0:44:22 > 0:44:26We continue our strange journey through the senses in Scotland,
0:44:26 > 0:44:30where the residents of Ayrshire have something very weird
0:44:30 > 0:44:33right on their doorstep.
0:44:33 > 0:44:37Something that seems to defy the laws of physics.
0:44:39 > 0:44:43It's a road called the Electric Brae.
0:44:46 > 0:44:50Ever since it was built, people have been drawn to this road.
0:44:50 > 0:44:55Not for the fresh air and scenery, but because it defies gravity.
0:44:58 > 0:45:03Even the quick-witted youth of the day are completely bamboozled by it.
0:45:03 > 0:45:07- LAUGHTER - Holy- BLEEP!
0:45:07 > 0:45:15And for good reason. After all, how can a car roll uphill without power?
0:45:15 > 0:45:17That has to be impossible.
0:45:17 > 0:45:19Surely it does,
0:45:19 > 0:45:22I mean, you don't have to be Isaac Newton to know a thing or two
0:45:22 > 0:45:24about gravity.
0:45:24 > 0:45:29Gravity pulls everything back down towards Earth.
0:45:29 > 0:45:33So, when we want to go up, we have to use kinetic energy,
0:45:33 > 0:45:37muscles, springs, engines and stuff to help us conquer gravity
0:45:37 > 0:45:38for a short while.
0:45:42 > 0:45:44But on the Electric Brae,
0:45:44 > 0:45:49cars can roll uphill with the engine off.
0:45:49 > 0:45:52And it's not the only road like this.
0:45:52 > 0:45:56These inexplicable inclines are found all over the world.
0:45:56 > 0:45:59Those that have experienced this phenomenon say
0:45:59 > 0:46:03it's like being drawn towards a magnet.
0:46:03 > 0:46:07So, these hills have been dubbed magnetic hills.
0:46:08 > 0:46:12So, could magnetism provide an explanation?
0:46:17 > 0:46:21Basically, we're all living on a massive magnet.
0:46:21 > 0:46:24At the centre of the Earth is a solid iron core,
0:46:24 > 0:46:27about two thirds the size of the moon
0:46:27 > 0:46:30and surrounding that is molten metal,
0:46:30 > 0:46:35which is constantly moving and this movement generates electricity,
0:46:35 > 0:46:40which in turn generates a magnetic field around the Earth.
0:46:44 > 0:46:46Known as the magnetosphere,
0:46:46 > 0:46:51it surrounds the entire planet and it's so huge it can be detected from
0:46:51 > 0:46:5540,000 miles away in space.
0:46:56 > 0:47:00So, if the Earth's magnetic field can be felt in space,
0:47:00 > 0:47:04then surely it's got to be capable of pulling a car on
0:47:04 > 0:47:06the surface of the planet up hill,
0:47:06 > 0:47:08hasn't it?
0:47:10 > 0:47:12Well, let's just see.
0:47:12 > 0:47:18This tiny magnet is powerful enough to pull this toy car up the slope.
0:47:20 > 0:47:22And of course, a little magnet, like this,
0:47:22 > 0:47:27is not going to be anywhere near as powerful as the massive magnet
0:47:27 > 0:47:29that is planet Earth, is it?
0:47:29 > 0:47:30Well, actually, yes.
0:47:30 > 0:47:34I've got to tell you that this is 300 times more powerful
0:47:34 > 0:47:37than the Earth's magnetic field.
0:47:37 > 0:47:41So, unless this can pull a full-size car up the hill,
0:47:41 > 0:47:43we can forget about magnetism.
0:47:46 > 0:47:49So, there must be some other force at work,
0:47:49 > 0:47:53after all, seeing is believing, isn't it?
0:47:53 > 0:47:56Vision scientists over the past 100 years or so
0:47:56 > 0:48:01have really come to recognise that seeing is a very active process.
0:48:04 > 0:48:08It's not just passively sitting back and letting the world impinge itself
0:48:08 > 0:48:10on your eyeballs. You're all the time reconstructing
0:48:10 > 0:48:13and forming guesses and hypotheses about what's out there.
0:48:13 > 0:48:16So, to that extent, seeing isn't believing -
0:48:16 > 0:48:19seeing is your brain's confabulation,
0:48:19 > 0:48:23the story you're telling yourself about what's out there.
0:48:23 > 0:48:28In other words, vision isn't just something we only do with our eyes.
0:48:28 > 0:48:32Light enters the eye, but the image it forms on our retina is both
0:48:32 > 0:48:34two-dimensional and upside down.
0:48:36 > 0:48:40So, why doesn't our world look like a wonky poster?
0:48:42 > 0:48:46Well, that's because our brain has taken this feeble 2-D image and
0:48:46 > 0:48:50re-converted it into a wonderfully complex 3-D world.
0:48:54 > 0:48:57And what's even more amazing is that it does all of this
0:48:57 > 0:48:59in a fraction of a second.
0:48:59 > 0:49:03I think it would be quite challenging for most computer visual
0:49:03 > 0:49:07systems to do as good a job with the information we have available.
0:49:07 > 0:49:12So, how does our brain process so much information so quickly?
0:49:12 > 0:49:14We do know in general,
0:49:14 > 0:49:17the visual system and the brain in general tends to use heuristics,
0:49:17 > 0:49:19rules of thumb.
0:49:21 > 0:49:25In other words, our brain takes short cuts by making assumptions.
0:49:27 > 0:49:31So, when we stand on the Electric Brae and look around,
0:49:31 > 0:49:34our brain assumes we're standing upright.
0:49:36 > 0:49:40It also assumes that the trees and road signs are vertical.
0:49:43 > 0:49:47It assumes that things look smaller the further away they are.
0:49:51 > 0:49:53And that the edges of a road get closer the further down
0:49:53 > 0:49:55it we look.
0:49:59 > 0:50:02Now, these assumptions normally work,
0:50:02 > 0:50:06but the Electric Brae doesn't play by the rules.
0:50:08 > 0:50:12Everything here is on a slope
0:50:12 > 0:50:14and no two gradients are the same.
0:50:15 > 0:50:19Our brain is trying to interpret complex geometry
0:50:19 > 0:50:22in an oddly tilted world.
0:50:23 > 0:50:25So, can it sometimes get it wrong?
0:50:28 > 0:50:31Because of the fact that our brains are having to reconstruct a 3-D
0:50:31 > 0:50:34world from very inadequate two-dimensional information,
0:50:34 > 0:50:38they do occasionally get it wrong and make mistakes and will perceive
0:50:38 > 0:50:40something which isn't really the case.
0:50:42 > 0:50:46So, this car looks like it's rolling uphill,
0:50:46 > 0:50:49but only in relation to the surrounding landscape.
0:50:51 > 0:50:55Just like this ball looks like it's rolling uphill.
0:50:55 > 0:50:59But only in relation to the frame surrounding it.
0:51:01 > 0:51:04It's only when we see the wider perspective
0:51:04 > 0:51:09that we realise this isn't a case of gravity gone mad at all.
0:51:10 > 0:51:13It is in fact a glitch in our perception.
0:51:16 > 0:51:20In other words, this strange phenomenon that's been entertaining
0:51:20 > 0:51:23day-trippers here for generations is just a weird
0:51:23 > 0:51:26and wonderful optical illusion.
0:51:32 > 0:51:34So, when we're fooled by optical illusions,
0:51:34 > 0:51:37it's down to our brain getting things wrong.
0:51:37 > 0:51:40But I am going to stick up for our brain, because it almost
0:51:40 > 0:51:42entirely gets things right.
0:51:42 > 0:51:45That's why we're so surprised when we see something
0:51:45 > 0:51:48that simply can't be true.
0:51:50 > 0:51:52For our next sensational story,
0:51:52 > 0:51:56we head to the coast of south-west Australia.
0:51:56 > 0:52:01This is a favourite spot for shark lovers from all over the world.
0:52:01 > 0:52:06And there is no bigger draw than a great white.
0:52:06 > 0:52:09But the traditional method of baiting them in with a bag of fish
0:52:09 > 0:52:13body parts can put sharks in a bit of a frenzy.
0:52:14 > 0:52:17And with water sports enthusiasts all along the coast,
0:52:17 > 0:52:21the last thing the authorities want to do here is put sharks
0:52:21 > 0:52:23in any kind of frenzy.
0:52:23 > 0:52:27So, when they stopped issuing licences to bait sharks,
0:52:27 > 0:52:31one tour operator had to get creative.
0:52:31 > 0:52:33Necessity is the mother of invention.
0:52:33 > 0:52:35When we started shark cage diving,
0:52:35 > 0:52:39initially we weren't allowed to use blood and bait, so we looked for
0:52:39 > 0:52:45alternatives around other senses that could attract sharks
0:52:45 > 0:52:49and music or acoustics was just an obvious thing to try.
0:52:50 > 0:52:53We may think it's rather quiet underwater,
0:52:53 > 0:52:57but in fact lots of marine animals use sound to communicate.
0:52:58 > 0:53:00But using music to attract sharks,
0:53:00 > 0:53:02where on earth you begin?
0:53:08 > 0:53:12So, when we first trialled this
0:53:12 > 0:53:16we just, we grabbed the speaker off one of my mates and we went down,
0:53:16 > 0:53:18we put it in the water, connected it to the iPod,
0:53:18 > 0:53:21it was my iPod and we just started at A.
0:53:21 > 0:53:24Now, I'm a country Aussie kid,
0:53:24 > 0:53:27I only have one type of music and it's usually Aussie rock,
0:53:27 > 0:53:30so the first album on the list was AC/DC - Back In Black.
0:53:30 > 0:53:33When we turned it on, we had sharks within a minute
0:53:33 > 0:53:34and they hung around for 20 minutes.
0:53:34 > 0:53:37And the sharks were coming up and just rubbing their face on
0:53:37 > 0:53:41the speaker and we were just like, "This is the coolest thing ever."
0:53:44 > 0:53:46Come on, come on.
0:53:46 > 0:53:50Even if we do away with the stereotypes of the long greasy hair,
0:53:50 > 0:53:53the patch-covered denim jackets and the head-banging,
0:53:53 > 0:53:57I just can't see sharks as heavy metal fans.
0:53:57 > 0:54:00So, was Matt's experiment a bit of a freak, a one-off,
0:54:00 > 0:54:05or do these animals truly have an appreciation of music?
0:54:05 > 0:54:07He was about to find out.
0:54:10 > 0:54:13Within days of the story hitting social media,
0:54:13 > 0:54:17Matt was inundated with requests to try other music.
0:54:18 > 0:54:21We started going through the playlist and what we saw is that it
0:54:21 > 0:54:23wasn't just AC/DC that attracts sharks,
0:54:23 > 0:54:24there were other songs as well.
0:54:24 > 0:54:29We got to one particular shark, Bernadette I think her name was,
0:54:29 > 0:54:32that every time we played Talking Heads - Sax And Violins
0:54:32 > 0:54:36she would breach out of the water.
0:54:36 > 0:54:39The only time we'd see this shark is when that song was playing and we
0:54:39 > 0:54:43started to think that maybe sharks had individual preferences.
0:54:43 > 0:54:47Matt now had proof that his experiment worked.
0:54:47 > 0:54:50The one big question remaining was why?
0:54:51 > 0:54:53A lot of species of sharks, like white sharks,
0:54:53 > 0:54:57that live in open ocean, or in the pelagic environment,
0:54:57 > 0:55:02because of the low rate of encounter of prey, potential prey,
0:55:02 > 0:55:06you would expect them to react and to investigate any kind of stimulus.
0:55:06 > 0:55:10So, if there is a sound or a smell that they encounter,
0:55:10 > 0:55:12because they are curious animals,
0:55:12 > 0:55:16they are likely to go and check out what is producing that sound,
0:55:16 > 0:55:19as it could potentially be a prey item.
0:55:21 > 0:55:24The sharks appeared to enjoy a wide musical repertoire,
0:55:24 > 0:55:29but the tracks that worked best had something in common -
0:55:29 > 0:55:32a driving bassline.
0:55:35 > 0:55:38Low-frequency sounds travel a long way underwater
0:55:38 > 0:55:41and it's just possible that sharks can mistake them
0:55:41 > 0:55:44for the death throes of an injured fish.
0:55:46 > 0:55:50That's because they don't just hear sound, they feel it.
0:55:52 > 0:55:53You see, in sharks,
0:55:53 > 0:55:58hearing and vibration detection are fundamentally linked.
0:55:58 > 0:56:04A fluid-filled tube call the lateral line extends along each flank.
0:56:07 > 0:56:10This tube is in direct contact with the water,
0:56:10 > 0:56:12via tiny holes in the skin.
0:56:15 > 0:56:18When sound causes the water to vibrate,
0:56:18 > 0:56:21it moves tiny hairs inside the lateral line
0:56:21 > 0:56:25and this tells the shark which direction it came from.
0:56:28 > 0:56:31Rock and roll, it does have the largest success probably,
0:56:31 > 0:56:35because of the lower down frequency vibrations, the bass beat.
0:56:35 > 0:56:37And even the distortion.
0:56:37 > 0:56:40It might have something to do with replication of a feeding behaviour,
0:56:40 > 0:56:45we don't know, but when a shark comes back to the same song,
0:56:45 > 0:56:48time after time, knowing that there's no food available,
0:56:48 > 0:56:54what is the attraction? Maybe they just think it's cool.
0:56:54 > 0:56:56Sitting underwater,
0:56:56 > 0:56:59listening to your favourite song by Metallica and having a shark just
0:56:59 > 0:57:01cruise past, looks like he's rocking out to the beat,
0:57:01 > 0:57:05letting his hair down and just kicking back with the tunes.
0:57:11 > 0:57:13Shark music.
0:57:13 > 0:57:17I absolutely love it, because it gives us the opportunity
0:57:17 > 0:57:21to redefine the great white as something which isn't a purely
0:57:21 > 0:57:25psychopathic fish and it gives people the ability to engage with
0:57:25 > 0:57:29this animal in a relatively nonintrusive way.
0:57:29 > 0:57:31It's genius. Utter genius.
0:57:31 > 0:57:35There's just one thing, I so wish they'd been into The Ramones.
0:57:40 > 0:57:42From a man with a finger-licking lexicon...
0:57:42 > 0:57:44Tastes horrible.
0:57:44 > 0:57:50..via a topsy-turvy hill, to a shark with an appetite for music,
0:57:50 > 0:57:52we've seen how the senses can perplex
0:57:52 > 0:57:55and please us in equal measure.
0:57:57 > 0:58:03From frogs to fish to beetles to humans, weirdness has no boundaries.
0:58:03 > 0:58:07It comes in all shapes and sizes.
0:58:08 > 0:58:11Next time on Nature's Weirdest Events...
0:58:14 > 0:58:16Weird washed-up blobs...
0:58:18 > 0:58:21..spiders with unfathomable feet...
0:58:24 > 0:58:27..and bizarre lakes the colour of bubble gum.