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 > 0:00:17Every day, news stories reach us.
0:00:17 > 0:00:19Stories that surprise us.
0:00:19 > 0:00:22What is that?
0:00:22 > 0:00:24- Shock us. - Wow.
0:00:26 > 0:00:29Sometimes, even scare us.
0:00:29 > 0:00:31Oh, my God.
0:00:32 > 0:00:38We've scoured the globe to bring you the most curious creatures,
0:00:38 > 0:00:40the 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 > 0:00:57of unexplained underwater blobs...
0:00:59 > 0:01:00..flying goats...
0:01:02 > 0:01:03and glow-in-the-dark fish,
0:01:06 > 0:01:10we examine the evidence, test the theories...
0:01:11 > 0:01:15..to work out what on earth is going on.
0:01:33 > 0:01:35In this episode,
0:01:35 > 0:01:40we lift the lid on some of nature's most confounding conundrums.
0:01:40 > 0:01:42We discover holes ripped out of the sky...
0:01:42 > 0:01:44Oh, Jeez.
0:01:44 > 0:01:47..see all that glitters is not gold,
0:01:47 > 0:01:50before finding out why these weird rock formations
0:01:50 > 0:01:54might just hold the key to finding alien life.
0:01:55 > 0:02:00But first, we're delving into the complex world of conspiracies,
0:02:00 > 0:02:03where weird events bring bizarre theories.
0:02:08 > 0:02:10May 2015.
0:02:10 > 0:02:15A television crew from the UK are in Kazakhstan expecting to film a
0:02:15 > 0:02:17gathering on an epic scale.
0:02:19 > 0:02:26The annual breeding congregation of a herd of 250,000 saiga antelope.
0:02:31 > 0:02:34With their distinctive bulbous noses,
0:02:34 > 0:02:36this grassland grazer might look like
0:02:36 > 0:02:39it's walked off the set of Star Wars,
0:02:39 > 0:02:43but it once roamed in vast herds all the way from Europe to Mongolia.
0:02:48 > 0:02:52This was supposed to be the story of the incredible survival of this
0:02:52 > 0:02:53ancient species.
0:02:58 > 0:03:01Now, on our first morning we went out.
0:03:01 > 0:03:03We dug a deep hole in the ground
0:03:03 > 0:03:06and camouflaged our cameraman and then backed off
0:03:06 > 0:03:08and waited for the sun to come up.
0:03:14 > 0:03:17But as the light fell across the plain,
0:03:17 > 0:03:21the sight that awaited them
0:03:21 > 0:03:23was truly shocking.
0:03:23 > 0:03:28What we started seeing was more and more dead saiga on the horizon.
0:03:29 > 0:03:32We went up and had a look at a few of the bodies,
0:03:32 > 0:03:35and we noticed some were frothing at the mouth,
0:03:35 > 0:03:37some of them had diarrhoea.
0:03:37 > 0:03:39Most of them were fully dead,
0:03:39 > 0:03:42so whatever had killed them had happened really, really quick.
0:03:43 > 0:03:44Over just three days,
0:03:44 > 0:03:47what started as a few dead individuals
0:03:47 > 0:03:52quickly turned into hundreds and then thousands.
0:03:52 > 0:03:54We were a bit concerned for our safety.
0:03:54 > 0:03:57We're in the middle of nowhere with no medical help,
0:03:57 > 0:04:00and you're looking at these large mammals that are dying on the spot,
0:04:00 > 0:04:03going from healthy to dead within hours.
0:04:03 > 0:04:04And of course nobody knew what it was,
0:04:04 > 0:04:07so everybody's looking at each other thinking, "Are we diseased?
0:04:07 > 0:04:10"Are we infected? Is this something from the X-Files?
0:04:10 > 0:04:12"Can we get out of here?"
0:04:14 > 0:04:17So what on earth was going on?
0:04:17 > 0:04:20What could explain the sudden death
0:04:20 > 0:04:23of hundreds of thousands of these animals?
0:04:24 > 0:04:27Getting answers was proving increasingly difficult.
0:04:28 > 0:04:29The authorities came in.
0:04:29 > 0:04:32At first, it was completely shut down.
0:04:32 > 0:04:33Nobody wanted the media to know.
0:04:33 > 0:04:35Nobody wanted us to film it.
0:04:35 > 0:04:39We basically were told to keep our mouths shut and not report this.
0:04:43 > 0:04:46Well, this is the scene that the Kazakhstan government
0:04:46 > 0:04:48didn't want us to see, or film.
0:04:50 > 0:04:52We felt very tortured.
0:04:52 > 0:04:54You almost felt like a war journalist on the front line,
0:04:54 > 0:04:58watching genocide before your very eyes.
0:04:58 > 0:04:59But we weren't really allowed to cover it.
0:05:01 > 0:05:06So was there something sinister the authorities were trying to cover up?
0:05:06 > 0:05:08We talked to the scientists,
0:05:08 > 0:05:11the researchers all had different theories.
0:05:11 > 0:05:14Some people thought that it might have been nuclear testing
0:05:14 > 0:05:16that had been done in the area.
0:05:20 > 0:05:23Other people started talking about diseases like anthrax.
0:05:23 > 0:05:24None of us had answers.
0:05:24 > 0:05:27None of us had any idea what was going on.
0:05:27 > 0:05:30As the Kazak government turned to the rest of the world for help,
0:05:30 > 0:05:33news teams were finally allowed in,
0:05:33 > 0:05:37and the true scale of the event started to become apparent.
0:05:37 > 0:05:39Scientists are not sure exactly why
0:05:39 > 0:05:42the species is dying off in such huge numbers.
0:05:43 > 0:05:48The saiga have been dying out in large numbers and nobody knows why.
0:05:50 > 0:05:53Entire herds have been found dead.
0:05:53 > 0:05:57About 135,000 animals in total,
0:05:57 > 0:06:01or 40% of a species that was already critically endangered.
0:06:03 > 0:06:05And as the journalists arrived,
0:06:05 > 0:06:07other evidence started coming to light.
0:06:08 > 0:06:12Many locals believe the mystery disease has fallen from the sky,
0:06:12 > 0:06:15linking it with failed launches of
0:06:15 > 0:06:19Russia's Proton-M rocket at Kazakhstan's Baikonur Cosmodrome.
0:06:30 > 0:06:33So could a rocket fuel leak really be to blame?
0:06:36 > 0:06:38Baikonur space station is right in the steppe,
0:06:38 > 0:06:40quite close to where the saigas give birth,
0:06:40 > 0:06:43and that's where the Russian space launches happen.
0:06:50 > 0:06:52When a space launch happens,
0:06:52 > 0:06:55then sometimes you can have a discharge of really,
0:06:55 > 0:06:56really toxic rocket fuel called heptyl.
0:06:56 > 0:06:59And if that goes on the grass, that could poison the animals.
0:06:59 > 0:07:04But sifting through the evidence, EJ began to see flaws in the timeline.
0:07:07 > 0:07:09Firstly, the timing was wrong.
0:07:09 > 0:07:11So they started dying before the space launch,
0:07:11 > 0:07:12a couple of days beforehand.
0:07:12 > 0:07:15And secondly, it would be quite a constrained area.
0:07:15 > 0:07:16Because it was such a large area,
0:07:16 > 0:07:20what we need is something that acts over that kind of landscape scale.
0:07:22 > 0:07:24To put this into perspective,
0:07:24 > 0:07:27the saiga apocalypse was taking place
0:07:27 > 0:07:31over an area of land the same as England and Wales combined.
0:07:31 > 0:07:35So it's highly unlikely that a single external factor
0:07:35 > 0:07:39could have been killing these animals over such a large area.
0:07:39 > 0:07:43The obvious next step was to examine the antelope internally.
0:07:46 > 0:07:48We could tell that this was really nasty.
0:07:48 > 0:07:52And so when we saw these vets arrive covered in biohazard suits,
0:07:52 > 0:07:56and masks and rubber gloves, taking very careful samples,
0:07:56 > 0:07:59most of the team were fairly freaked out.
0:07:59 > 0:08:04Dozens of postmortems all revealed the same gruesome cause of death.
0:08:04 > 0:08:06What actually happened was that there was internal bleeding,
0:08:06 > 0:08:08so they were bleeding everywhere inside,
0:08:08 > 0:08:10which is what caused them to die.
0:08:11 > 0:08:14But it couldn't be a contagious disease.
0:08:14 > 0:08:16There simply wasn't time for one to spread
0:08:16 > 0:08:18from individual to individual.
0:08:20 > 0:08:22After months of tests,
0:08:22 > 0:08:24scientists were finally confident
0:08:24 > 0:08:27they'd identified the cause of death.
0:08:27 > 0:08:29What we found was it's a bacterium
0:08:29 > 0:08:33which is called Pasteurella multocida.
0:08:33 > 0:08:35It seems that within hours
0:08:35 > 0:08:38the whole herd had contracted a deadly infection.
0:08:38 > 0:08:42Something happened to trigger that bacterium
0:08:42 > 0:08:44to suddenly become virulent,
0:08:44 > 0:08:48so produce these toxins and kill the animals very, very quickly.
0:08:48 > 0:08:51But how on earth did this happen?
0:08:51 > 0:08:54Well, this is where it gets very weird.
0:08:55 > 0:08:59You see, this bacteria wasn't a new threat.
0:08:59 > 0:09:02Just like in many ruminants, it occurs naturally,
0:09:02 > 0:09:06normally residing harmlessly in the saigas' lungs
0:09:06 > 0:09:09and those massive bulbous noses.
0:09:09 > 0:09:13But something had caused its population to explode,
0:09:13 > 0:09:16leading to septicaemia, internal bleeding,
0:09:16 > 0:09:20respiratory complications and rapidly death.
0:09:20 > 0:09:25So the thought is it would've had to be a short-term drop in temperature.
0:09:25 > 0:09:28Or a short-term change in, for example, wind chill.
0:09:29 > 0:09:32That would compromise their immune system and made them weaker,
0:09:32 > 0:09:36that might have allowed the bacterium to take hold.
0:09:36 > 0:09:39If EJ is right and there was a severe temperature drop
0:09:39 > 0:09:44at the beginning of May, after a month of unseasonably wet weather,
0:09:44 > 0:09:47it was the worst possible moment.
0:09:47 > 0:09:50You see, the saiga had just shed their winter coats.
0:09:50 > 0:09:53Mothers were weakened from giving birth.
0:09:53 > 0:09:56Combined, it was a perfect storm,
0:09:56 > 0:10:01turning the normally harmless bacteria into lethal pathogens.
0:10:01 > 0:10:03But there is some hope.
0:10:04 > 0:10:08When our colleagues went out and did an expedition after the deaths
0:10:08 > 0:10:10to see what they could find,
0:10:10 > 0:10:14they found a few herds of partially-grown babies,
0:10:14 > 0:10:20and it seems like perhaps they had managed to get independent
0:10:20 > 0:10:21before their mothers died,
0:10:21 > 0:10:24so miraculously some babies survived.
0:10:24 > 0:10:29In total, more than 88% of the herd's population,
0:10:29 > 0:10:33200,000 animals have been lost.
0:10:33 > 0:10:36But it's not the end for this extraordinary animal.
0:10:37 > 0:10:39The saiga population is remarkable
0:10:39 > 0:10:41in that, if weather conditions are right,
0:10:41 > 0:10:45it can increase by 60% in a single year.
0:10:45 > 0:10:50So these saiga survivors may well live to fight another day.
0:10:53 > 0:10:56From one conspiracy theory to another.
0:11:01 > 0:11:05Throughout history, man has looked up to the skies for answers.
0:11:07 > 0:11:08But in November 2010,
0:11:08 > 0:11:14a strange shape in the sky left onlookers with only questions.
0:11:16 > 0:11:17Look at this. What the hell?
0:11:19 > 0:11:20Look at that sky.
0:11:21 > 0:11:24What looked like a perfect hole,
0:11:24 > 0:11:27punched out of the clouds above Arizona.
0:11:27 > 0:11:32- Look at that. That is freaking bizarre.- Very weird.
0:11:32 > 0:11:35But this wasn't a one-off.
0:11:38 > 0:11:42In September 2012, this one was filmed above Moscow.
0:11:45 > 0:11:47And this one showed up in Ontario, Canada.
0:11:47 > 0:11:51That's weird.
0:11:51 > 0:11:54But what are these bizarre clouds?
0:11:54 > 0:11:56What could be causing these perfect patterns?
0:11:58 > 0:12:02Well, the internet, of course, is awash with strange theories.
0:12:02 > 0:12:07I've seen people speculate that it's UFOs,
0:12:07 > 0:12:12or perhaps some covert government operation that's given rise to these
0:12:12 > 0:12:16strange, you know, holes punched out of the cloud.
0:12:20 > 0:12:24OK, so these cloud formations might seem utterly bizarre
0:12:24 > 0:12:26but they are known to science.
0:12:28 > 0:12:32They're called fallstreak holes, and their existence has
0:12:32 > 0:12:36generated one particularly out-there conspiracy.
0:12:38 > 0:12:42To believers, their existence is connected to a US Air Force and Navy
0:12:42 > 0:12:46research facility known as Haarp.
0:12:48 > 0:12:50Set up to study the upper atmosphere
0:12:50 > 0:12:52for communication and surveillance purposes,
0:12:52 > 0:12:58the rumour goes that the site's real aim is to control catastrophic
0:12:58 > 0:13:00weather events,
0:13:00 > 0:13:04turning everything from earthquakes to hurricanes into weapons.
0:13:06 > 0:13:08And the fallstreak holes?
0:13:08 > 0:13:11Well, some believe they are evidence of these experiments at work.
0:13:14 > 0:13:15Sound unlikely?
0:13:15 > 0:13:17I think so.
0:13:17 > 0:13:21Here's another more logical and scientific explanation.
0:13:21 > 0:13:24A fallstreak hole is a dramatic cloud feature
0:13:24 > 0:13:29and it looks like a layer of cloud has had a hole cut out of it,
0:13:29 > 0:13:33almost like a cookie cutter has been placed on it.
0:13:33 > 0:13:37And below this hole is a streak,
0:13:37 > 0:13:41rather like the tendrils of a jellyfish,
0:13:41 > 0:13:44hanging down below and petering out into the blue.
0:13:44 > 0:13:49Whilst the clouds around these weird holes may look fairly normal,
0:13:49 > 0:13:51your average white fluffy kind,
0:13:51 > 0:13:55there is actually far more to them than meets the eye.
0:13:55 > 0:14:00You see, the water droplets suspended in them have a superpower.
0:14:00 > 0:14:02One of these formations can form
0:14:02 > 0:14:05when a layer of cloud is made of droplets,
0:14:05 > 0:14:07but droplets that are very, very cold,
0:14:07 > 0:14:10and they're known as supercooled droplets of water.
0:14:12 > 0:14:15The key to understanding this supercooling superpower
0:14:15 > 0:14:19is to realise that one of the most basic scientific experiments
0:14:19 > 0:14:22that we are taught is actually wrong.
0:14:22 > 0:14:26You see, at school, we are told that water freezes
0:14:26 > 0:14:28at zero degrees centigrade.
0:14:28 > 0:14:30But it's simply not true.
0:14:30 > 0:14:35Only impure water freezes at zero degrees centigrade.
0:14:35 > 0:14:38Pure water, like that found in these clouds,
0:14:38 > 0:14:41freezes much lower - much, much lower.
0:14:42 > 0:14:48The tiny droplets can actually go down to -15 degrees Celsius, -20.
0:14:48 > 0:14:53In fact, they can go down as cold as -40 degrees Celsius without starting
0:14:53 > 0:14:58to freeze, unless there's something for them to get started on.
0:14:59 > 0:15:04This supercooled water can remain suspended in the cloud indefinitely,
0:15:04 > 0:15:09until a tiny speck of dirt or a shard of impure ice
0:15:09 > 0:15:11falls from a cloud above...
0:15:13 > 0:15:14..and boom!
0:15:14 > 0:15:18One particle triggers the freeze in a chain reaction that
0:15:18 > 0:15:21spreads out in a perfect circle.
0:15:21 > 0:15:22And the streak below?
0:15:22 > 0:15:25Well, that's just the ice crystals falling,
0:15:25 > 0:15:28leaving a beautiful rainbow tendril beneath.
0:15:30 > 0:15:31Absolutely bizarre.
0:15:33 > 0:15:35That's way cool.
0:15:35 > 0:15:38So, if it's not a government conspiracy,
0:15:38 > 0:15:42why exactly have we been seeing more and more of these strange holes
0:15:42 > 0:15:45appearing in recent decades?
0:15:45 > 0:15:48Well, there's a logical explanation for that, too.
0:15:48 > 0:15:52One thing that can set off the freezing is,
0:15:52 > 0:15:54surprisingly, an aeroplane.
0:15:57 > 0:16:02When an aircraft flies up through a layer of supercooled droplets,
0:16:02 > 0:16:06it can be just the trigger needed to start the freezing.
0:16:07 > 0:16:12Many fallstreak holes are in fact caused by polluting particles from
0:16:12 > 0:16:13the aircraft's exhaust,
0:16:13 > 0:16:17or by a rapid drop in temperature around the wing,
0:16:17 > 0:16:20acting as a trigger for the freeze.
0:16:22 > 0:16:26So this is not a case of UFOs, it's a case of EFOs,
0:16:26 > 0:16:28explained flying objects,
0:16:28 > 0:16:30in the form of planes,
0:16:30 > 0:16:34which are producing these bizarre clouds all over the world.
0:16:37 > 0:16:40From one set of bizarre theories to another.
0:16:40 > 0:16:43Only these are so extraordinary
0:16:43 > 0:16:46they are verging on the extra-terrestrial.
0:16:50 > 0:16:52The Peruvian desert,
0:16:52 > 0:16:57with vast swathes of arid scrub and massive sand dunes,
0:16:57 > 0:16:58it might look like a barren,
0:16:58 > 0:17:04uninspiring place, but this is a land rich in ancient oddities.
0:17:04 > 0:17:10From strange skulls found in nearby Paracas, resembling alien coneheads,
0:17:10 > 0:17:11to the Nazca Lines,
0:17:11 > 0:17:16bizarre drawings hundreds of metres long carved out of the desert scrub.
0:17:18 > 0:17:22But one curious construction, first recorded in 1931,
0:17:22 > 0:17:25has baffled visitors ever since.
0:17:27 > 0:17:28As you can see,
0:17:28 > 0:17:34this is the most amazing discovery in the history of mankind.
0:17:34 > 0:17:38I don't know what it is, the scientists don't know what it is.
0:17:38 > 0:17:40It's just an amazing, amazing thing.
0:17:43 > 0:17:45Known as the Band Of Holes,
0:17:45 > 0:17:49these 7,000 two-meter wide pits
0:17:49 > 0:17:52carved out of the barren rock stretch along
0:17:52 > 0:17:55a ridge for more than one-and-a-half kilometres.
0:17:55 > 0:17:58And their purpose has been linked to everything,
0:17:58 > 0:18:02from alien hatching pods to UFO launchpads.
0:18:02 > 0:18:05Well, there are a lot of crazy theories in archaeology
0:18:05 > 0:18:06about just about everything.
0:18:12 > 0:18:15Maybe some of the craziest are that these are some kind of
0:18:15 > 0:18:18constructions by aliens as guideposts.
0:18:19 > 0:18:20It's kind of silly.
0:18:21 > 0:18:24Probably, if you can fly from Alpha Centauri to Earth,
0:18:24 > 0:18:26you probably don't need a guidepost.
0:18:27 > 0:18:32All those nonmainstream theories really don't stand up to any kind of
0:18:32 > 0:18:34serious scientific scrutiny.
0:18:34 > 0:18:37For over 80 years,
0:18:37 > 0:18:41visitor after visitor has tried to work out just what these strange,
0:18:41 > 0:18:45now partially collapsed holes could possibly have been used for.
0:18:45 > 0:18:48Look at that. That's a skull right there.
0:18:49 > 0:18:50Unreal, man.
0:18:51 > 0:18:54It's, like, an Inca burial site?
0:18:54 > 0:18:55No!
0:18:56 > 0:18:58Hm...
0:18:58 > 0:18:59So, had our enthusiastic tourists
0:18:59 > 0:19:02stumbled across the missing evidence?
0:19:02 > 0:19:05Were they a long line of graves?
0:19:06 > 0:19:10Well, ancient Peruvians did bury their dead in a crouched,
0:19:10 > 0:19:13sitting position, facing the rising sun.
0:19:15 > 0:19:17But the theory just didn't stand up.
0:19:17 > 0:19:20Only a handful of bones had been found,
0:19:20 > 0:19:24certainly not enough to justify 7,000 graves.
0:19:25 > 0:19:29So if it's not graves, what could it be?
0:19:29 > 0:19:32In 2015, archaeologist Charles Stanish
0:19:32 > 0:19:35went to investigate for himself.
0:19:35 > 0:19:37Well, it's a fascinating site.
0:19:37 > 0:19:39It really... It's what we live for as archaeologists.
0:19:39 > 0:19:41We find a mystery, we love mysteries.
0:19:42 > 0:19:44We started to look around
0:19:44 > 0:19:48and we noticed that the holes look very similar
0:19:48 > 0:19:51to storage pit constructions
0:19:51 > 0:19:54that were typical of the Inca and pre-Inca times.
0:19:54 > 0:19:59With an encyclopaedic knowledge of prehistoric Peruvian culture,
0:19:59 > 0:20:01Charles started to see clues all around him.
0:20:02 > 0:20:04And then below we found a road,
0:20:04 > 0:20:06an Inca road, classic Inca road construction.
0:20:06 > 0:20:10They are very like Roman roads, you can pick them up right away.
0:20:10 > 0:20:12And they're 5km from
0:20:12 > 0:20:15the major Inca administrative site of Tambo Colorado.
0:20:15 > 0:20:19And it's right up valley from one of the richest agricultural areas
0:20:19 > 0:20:21in the world, for that matter.
0:20:21 > 0:20:26Charles had spotted an ancient road running right alongside the holes,
0:20:26 > 0:20:29leading to the main road below.
0:20:29 > 0:20:33With the Incan administrative site of Tambo Colorado
0:20:33 > 0:20:37just 5km to the east and rich farmlands to the west,
0:20:37 > 0:20:39Charles was onto something.
0:20:39 > 0:20:41But he still needed to explain
0:20:41 > 0:20:43exactly what the holes were used for.
0:20:43 > 0:20:47And the answer to this complex conundrum
0:20:47 > 0:20:50was to be found in the pattern of the pits.
0:20:52 > 0:20:57The thing that really intrigued us was that the holes were in lines,
0:20:57 > 0:21:00and there appeared to be numerical patterning of the holes,
0:21:00 > 0:21:03so we started to count them and it was like,
0:21:03 > 0:21:05"One, two, three, four, five, six, seven.
0:21:05 > 0:21:07"Seven, eight, eight, nine, nine."
0:21:07 > 0:21:10And at that point we said, "OK, something much
0:21:10 > 0:21:12"more interesting is going on."
0:21:14 > 0:21:18One, two, three, four.
0:21:18 > 0:21:21What we've got here is a very precise pattern
0:21:21 > 0:21:24of numerically ordered holes.
0:21:24 > 0:21:28So we have to suppose that the Inca were counting.
0:21:30 > 0:21:32But what exactly where they counting?
0:21:33 > 0:21:36Well, it wasn't money, that's for sure.
0:21:38 > 0:21:43Well, in the Inca Empire, people paid tribute in commodities.
0:21:43 > 0:21:46There was no money. So people had to pay with labour
0:21:46 > 0:21:47and with commodities.
0:21:47 > 0:21:52And so every village or every kin group, or every taxpaying unit was
0:21:52 > 0:21:57required to pay with labour or in kind.
0:21:57 > 0:22:00And the holes would fit that model of a
0:22:00 > 0:22:03non-monetary Inca tribute system.
0:22:03 > 0:22:09And once Charles had all of his clues lined up in a row, the answer,
0:22:09 > 0:22:11to him at least, was obvious.
0:22:11 > 0:22:17The Pisco holes are most likely an accounting device
0:22:17 > 0:22:19devised by the Inca state.
0:22:19 > 0:22:21You come up the valley,
0:22:21 > 0:22:24you stop right before you get to the last big Inca site before you go up
0:22:24 > 0:22:26into the highlands.
0:22:26 > 0:22:29And this is where you would leave your materials.
0:22:29 > 0:22:31So every community,
0:22:31 > 0:22:33every taxpaying group, would be responsible
0:22:33 > 0:22:35to fill up so many of these holes.
0:22:35 > 0:22:39And once your block was filled, then you would move on.
0:22:42 > 0:22:45So the Pisco holes were not evidence of an alien invasion
0:22:45 > 0:22:47or a ceremonial burial site.
0:22:47 > 0:22:50They were a method of paying taxes.
0:22:50 > 0:22:53Yes, as the farmers passed by,
0:22:53 > 0:22:58they would deposit a percentage of their produce in each of the holes
0:22:58 > 0:23:02as a means of paying their annual tax to the state.
0:23:02 > 0:23:06What about that? It's accountancy but without the paperwork.
0:23:06 > 0:23:08And that's got to be a good idea.
0:23:13 > 0:23:16From a saiga apocalypse in Kazakhstan,
0:23:16 > 0:23:18weird holes punched in the sky,
0:23:18 > 0:23:21to bizarre pits carved in the Peruvian desert,
0:23:21 > 0:23:24a potential conspiracy can pop up anywhere.
0:23:24 > 0:23:29And strange theories often lead to stranger explanations.
0:23:31 > 0:23:32Coming up...
0:23:32 > 0:23:35a selection of bizarre invasions,
0:23:35 > 0:23:38from glowing, glittering, scary spiders,
0:23:38 > 0:23:42to a mystery threat terrorising sea birds.
0:23:43 > 0:23:47But first, we're investigating the last invasion force
0:23:47 > 0:23:49from a very Cold War indeed.
0:23:53 > 0:23:552016, Norway.
0:23:57 > 0:24:01A beautiful landscape of dramatic fjords and majestic coastlines.
0:24:03 > 0:24:06But under the waves, all is not well.
0:24:09 > 0:24:12You see, Norwegian waters are under attack.
0:24:14 > 0:24:17It's a voracious animal, it spreads far and fast.
0:24:19 > 0:24:24An army over 20 million strong has invaded this stretch of coastline.
0:24:27 > 0:24:30These are red king crabs.
0:24:32 > 0:24:34And they're on the rampage.
0:24:44 > 0:24:46What a leg.
0:24:46 > 0:24:49What an extraordinary appendage this is.
0:24:51 > 0:24:54You know, these crabs can grow to 10kg in weight
0:24:54 > 0:24:58and their leg span can be 1.8 metres across.
0:24:58 > 0:25:01They are monstrous, monstrous.
0:25:01 > 0:25:03But unfortunately,
0:25:03 > 0:25:07they're equally having a monstrous effect beneath the waves.
0:25:07 > 0:25:11Now, you've heard the phrase, "an army marches on its stomach".
0:25:11 > 0:25:16Well, the red king crab is far from a picky eater.
0:25:16 > 0:25:18It eats pretty much everything.
0:25:23 > 0:25:29So it can eat worms, slugs, sea urchins, starfish, which means that,
0:25:29 > 0:25:32you know, anywhere it goes it will
0:25:32 > 0:25:36find a type of food source that it can eat.
0:25:36 > 0:25:39And fuelled by their insatiable appetites,
0:25:39 > 0:25:41this invasion force is growing.
0:25:43 > 0:25:49One female red king crab can lay over half a million eggs every year.
0:25:51 > 0:25:55And this has allowed this army to triple its numbers
0:25:55 > 0:25:56in the last ten years.
0:25:58 > 0:26:02It's very bad news for Norway's marine life.
0:26:02 > 0:26:04It can be quite disastrous.
0:26:04 > 0:26:07It has had huge impacts on the ecosystem.
0:26:09 > 0:26:13Just how have these massive marauders got so out of hand?
0:26:18 > 0:26:20Well, the weird thing is
0:26:20 > 0:26:24these crabs, they haven't always been here.
0:26:24 > 0:26:27The story goes that in the sleepy village of Burgoynes,
0:26:27 > 0:26:29in northern Norway,
0:26:29 > 0:26:34the first crabs were pulled from the depths in 1977.
0:26:34 > 0:26:36So where had they come from?
0:26:39 > 0:26:44The thing is, these king crabs didn't come from Norway.
0:26:44 > 0:26:49In fact, they didn't even originate in Scandinavia or indeed Europe.
0:26:49 > 0:26:54No, no, no. They came from all the way over here - Alaska.
0:26:54 > 0:26:57That's 6,000km away.
0:26:57 > 0:27:00It seems like an impossible journey.
0:27:00 > 0:27:02But it obviously wasn't.
0:27:02 > 0:27:04So how did the crabs get there?
0:27:06 > 0:27:10Back in the 1930s, with Russians around the Barents Sea starving,
0:27:10 > 0:27:15Soviet dictator Joseph Stalin was on the lookout for a transportable,
0:27:15 > 0:27:18quick-growing, nourishing food source
0:27:18 > 0:27:21and the red king crab fitted the bill perfectly.
0:27:23 > 0:27:27But it wasn't as easy as just shipping them across the country.
0:27:27 > 0:27:28Several attempts failed.
0:27:32 > 0:27:34But the scientists weren't about to give up.
0:27:37 > 0:27:41It took 30 years for Stalin's plan to be implemented.
0:27:41 > 0:27:46Crabs finally making the journey from Alaska to Murmansk by plane.
0:27:46 > 0:27:47But once there,
0:27:47 > 0:27:51with predators like the sea otter left far behind in Alaska,
0:27:51 > 0:27:53they thrived.
0:27:53 > 0:28:00And in 1977, when those crabs washed up in Bargoynes, 170 miles away,
0:28:00 > 0:28:04the Norwegians knew that Stalin's Red Army had spread,
0:28:04 > 0:28:06and their waters were now under attack.
0:28:09 > 0:28:1340 years on, and the battle is still raging.
0:28:17 > 0:28:20The problem with the king crab is, once they're first established,
0:28:20 > 0:28:23it becomes really, really difficult to remove them.
0:28:25 > 0:28:29Even if we were able to virtually decimate them from Norwegian waters,
0:28:29 > 0:28:33the challenge would be that the Russians still want to keep them,
0:28:33 > 0:28:36so we would still have a constant influx of crabs
0:28:36 > 0:28:38coming in from Russia,
0:28:38 > 0:28:43and it's not like we can establish any borders underneath the ocean.
0:28:43 > 0:28:49So it's going to be really, really hard to ever get rid of this animal.
0:28:49 > 0:28:54Maybe, but the Norwegians are very practical people.
0:28:54 > 0:28:57They may not been able to win the war,
0:28:57 > 0:29:00but luckily this enemy is delicious.
0:29:01 > 0:29:07Yes, those huge legs are considered a delicacy, and fetch top dollar in
0:29:07 > 0:29:08Japan and America.
0:29:10 > 0:29:13The best thing that we can do is to intensify the fishing,
0:29:13 > 0:29:16and just allow open access to the resource,
0:29:16 > 0:29:20to allow as many people as possible to fish for the crab,
0:29:20 > 0:29:22and then restrict its further spread.
0:29:28 > 0:29:32So it seems that Stalin's last Red Army, the red king crabs,
0:29:32 > 0:29:36are about to do something that the Soviet Union could never do -
0:29:36 > 0:29:39invade Western Europe.
0:29:39 > 0:29:40What a terrible thought.
0:29:40 > 0:29:44And the only thing we can do to stop them is to carry on fishing,
0:29:44 > 0:29:47which means, in turn, that we've got to carry on eating them.
0:29:47 > 0:29:50It is a seafood lover's dream.
0:29:50 > 0:29:53It's an invasion we've really got to get our teeth into...
0:29:56 > 0:30:01From a giant, armoured intruder taking over Norwegian waters,
0:30:01 > 0:30:05to a chilling encounter with the creepiest of crawlies...
0:30:08 > 0:30:09Spiders.
0:30:09 > 0:30:11Now, I love them, of course, but let's be honest,
0:30:11 > 0:30:14they do have a serious image problem.
0:30:15 > 0:30:18Arachnophobia is common the world over.
0:30:18 > 0:30:22Almost a third of Americans claim to suffer from it.
0:30:22 > 0:30:24And the reason?
0:30:24 > 0:30:25Well, depending on who you ask,
0:30:25 > 0:30:29is down to a few million years of evolution,
0:30:29 > 0:30:35a terrifying personal experience, or to a barrage of cultural references
0:30:35 > 0:30:38telling us that spiders are scary.
0:30:38 > 0:30:42For shocking, skin-crawling excitement,
0:30:42 > 0:30:49meet, face to face, 50 creeping tonnes of black horror.
0:30:49 > 0:30:54See...The Spider.
0:30:54 > 0:30:57But when this weird intruder comes knocking,
0:30:57 > 0:31:01you've got every right to take fright.
0:31:01 > 0:31:03Oh, my. Jeez. Look at that.
0:31:03 > 0:31:05In summer 2016,
0:31:05 > 0:31:08police detective Jared Marshall's Louisiana home
0:31:08 > 0:31:13was invaded by one particularly arresting arachnid.
0:31:13 > 0:31:15Oh, my Lord. What the heck?
0:31:16 > 0:31:17It's so strange.
0:31:19 > 0:31:22So just what had invaded Jared's privacy?
0:31:25 > 0:31:29Had he stumbled upon Peter Parker's radioactive spider?
0:31:29 > 0:31:31Well, clearly not.
0:31:31 > 0:31:33But Jared had his own theory.
0:31:34 > 0:31:36What the heck is that lighting up?
0:31:36 > 0:31:39What is that?
0:31:41 > 0:31:46- Holy- BLEEP.- It's like it's bioluminescent or something.
0:31:46 > 0:31:47Oh, my gosh.
0:31:49 > 0:31:50Oh, that is freaky.
0:31:57 > 0:31:59Glowing, glittering green spiders.
0:31:59 > 0:32:02It doesn't get much freakier than that, does it?
0:32:02 > 0:32:04But is our American friend right?
0:32:04 > 0:32:06Is this down to bioluminescence?
0:32:09 > 0:32:12From the night sky to the ocean's depths,
0:32:12 > 0:32:15animals are using a light-emitting compound called luciferin,
0:32:15 > 0:32:19combined with an enzyme catalyst to illuminate the darkness.
0:32:21 > 0:32:23Some do it to attract mates,
0:32:23 > 0:32:26whilst for others it's to entice prey.
0:32:32 > 0:32:37So could this footage be the first-ever documented case
0:32:37 > 0:32:39of arachnid bioluminescence?
0:32:40 > 0:32:42Well, no.
0:32:42 > 0:32:44So the spider's not glowing.
0:32:44 > 0:32:45It's not producing its own light.
0:32:45 > 0:32:49If you look very carefully here you can see what it's doing is actually
0:32:49 > 0:32:51reflecting light.
0:32:54 > 0:32:59You can see the reflection changing as the light source moves.
0:32:59 > 0:33:01They are beautifully weird, aren't they?
0:33:01 > 0:33:03But could the clue to this dazzling display
0:33:03 > 0:33:07be found in another spider species?
0:33:07 > 0:33:12We know spiders from the coastlines up to 7,000 metres in the Himalayas.
0:33:17 > 0:33:20You have lots of spiders with these guanine crystals in the abdomen,
0:33:20 > 0:33:25and you can call them mirror spiders because they reflect the light.
0:33:25 > 0:33:30So these guanine crystals are firstly good for making a pattern.
0:33:30 > 0:33:32This could be good for camouflaging.
0:33:32 > 0:33:36And then it is also good for preventing the spiders
0:33:36 > 0:33:38from overheating in the sun,
0:33:38 > 0:33:41when they sit during the daytime in their web.
0:33:42 > 0:33:44A mirror spider with his own mirrors.
0:33:44 > 0:33:45What a thing.
0:33:47 > 0:33:49But is this sequinned stunner
0:33:49 > 0:33:51related to our mystery sparkling spider?
0:33:53 > 0:33:58Well, the answer to this reflecting riddle isn't quite that simple.
0:33:58 > 0:34:01You see, the spider in Jared's film is a wolf spider,
0:34:01 > 0:34:05a nomadic night hunter constantly on the move,
0:34:05 > 0:34:10with no need for protection from the sun nor this kind of camouflage.
0:34:10 > 0:34:13But Jared's film wasn't a one-off.
0:34:13 > 0:34:14Take a look at this.
0:34:16 > 0:34:18What in the heck is that?
0:34:18 > 0:34:22And as you look closely at these films you may start to notice some
0:34:22 > 0:34:23similarities.
0:34:23 > 0:34:26All of them have been filmed in the dark
0:34:26 > 0:34:28with the camera's flashlight on,
0:34:28 > 0:34:31and in these conditions our eyes struggle
0:34:31 > 0:34:34but the spiders have evolved a solution.
0:34:34 > 0:34:38Many spiders have a reflecting layer in their eyes.
0:34:38 > 0:34:43Spiders have usually eight eyes, two eyes in the front, the main eyes,
0:34:43 > 0:34:49and all the other six are secondary eyes and these eyes may have these
0:34:49 > 0:34:53tapetum, a so-called tapetum, which reflects the light,
0:34:53 > 0:34:56which makes them like shining diamonds in the night.
0:34:59 > 0:35:02Yes, just like many nocturnal animals,
0:35:02 > 0:35:05these spiders have a group of reflective cells
0:35:05 > 0:35:07in their eyes behind the retina,
0:35:07 > 0:35:09that do something incredible.
0:35:16 > 0:35:18Light enters the eye,
0:35:18 > 0:35:22passes over the retina and hits this reflective layer
0:35:22 > 0:35:24known as the tapetum.
0:35:24 > 0:35:27It then concentrates what little light there is,
0:35:27 > 0:35:29and reflects it back,
0:35:29 > 0:35:33allowing the spider's retina a second chance to process
0:35:33 > 0:35:35any light it missed the first time,
0:35:35 > 0:35:39enabling it to see in near darkness.
0:35:39 > 0:35:42Quite useful for a nocturnal hunter.
0:35:43 > 0:35:46So that explains why the spider's eyes are glowing.
0:35:46 > 0:35:48But the mystery remains.
0:35:48 > 0:35:50Why are their bodies ablaze, too?
0:35:52 > 0:35:57Well, this piece of footage might just unravel that mystery.
0:36:00 > 0:36:01SCREAMS AND LAUGHTER
0:36:01 > 0:36:02Oh!
0:36:05 > 0:36:06Oh, my God...
0:36:08 > 0:36:10So what on earth is going on?
0:36:10 > 0:36:14Well, the truth is just about as weird as it looks.
0:36:16 > 0:36:18SCREAMS AND LAUGHTER
0:36:25 > 0:36:28Wolf spiders are distributed around the world,
0:36:28 > 0:36:30and they have special brood care behaviours,
0:36:30 > 0:36:34and the mother is carrying them around and taking care of them.
0:36:34 > 0:36:37It can be ten spiderlings or probably hundreds of spiderlings.
0:36:38 > 0:36:40And it's this special brood care,
0:36:40 > 0:36:43combined with their remarkable eye design,
0:36:43 > 0:36:47that holds the key to understanding this strange event.
0:36:49 > 0:36:52When we know the fact that we have six eyes
0:36:52 > 0:36:54with these reflecting layers,
0:36:54 > 0:36:57then it's just a matter of likelihood
0:36:57 > 0:37:01that we get one eye particularly in this right angle
0:37:01 > 0:37:03to see the eye shine.
0:37:03 > 0:37:07And if you have then more spiderlings on the mother's back,
0:37:07 > 0:37:09then the likelihood is quite high
0:37:09 > 0:37:12to see some of the eyes shining the light back.
0:37:15 > 0:37:18All her eyes are, like, glowing.
0:37:18 > 0:37:23Her eyes are shining and all the little baby eyes
0:37:23 > 0:37:27are shining, too, like looking in the mirror.
0:37:27 > 0:37:29So there you have it.
0:37:29 > 0:37:31The glitter spider is in fact just a
0:37:31 > 0:37:35mother carrying her babies on her back and it's their eyes
0:37:35 > 0:37:37you see glittering back at you.
0:37:37 > 0:37:38How sweet.
0:37:41 > 0:37:43Well, no, not entirely.
0:37:46 > 0:37:48So the wolf spider mother is caring for their brood
0:37:48 > 0:37:50probably for a few weeks.
0:37:50 > 0:37:53Then the mother will die
0:37:53 > 0:37:58and the brood, in a positive case, will eat her.
0:37:59 > 0:38:03Or feed on her. So the nutrition is not wasted.
0:38:05 > 0:38:08Yes, the mother spider is about to make
0:38:08 > 0:38:12the ultimate sacrifice to ensure that her young survive.
0:38:12 > 0:38:14But they'd better move on quickly before
0:38:14 > 0:38:18these siblings start seeing each other as their next course.
0:38:23 > 0:38:26Spiders, they'll explode like a firework.
0:38:26 > 0:38:31The explanation may be simple but the result is truly spectacular.
0:38:34 > 0:38:37From a scary invasion in the American suburbs,
0:38:37 > 0:38:41to a far more sinister one miles from home.
0:38:48 > 0:38:52Two islands far from the coast of South Africa, Gough and Marion,
0:38:52 > 0:38:55are home to millions of nesting sea birds,
0:38:55 > 0:38:58but they share a sinister bond.
0:39:00 > 0:39:02Something truly terrifying.
0:39:05 > 0:39:10We thought it was a safe haven but something drastically wrong was
0:39:10 > 0:39:11happening on the island.
0:39:19 > 0:39:21In September 2000,
0:39:21 > 0:39:24ornithologists Richard and Erica Cuthbert's dream placement
0:39:24 > 0:39:26quickly became a nightmare.
0:39:30 > 0:39:32So we're on the island really to set up
0:39:32 > 0:39:35monitoring protocols for these birds.
0:39:37 > 0:39:42And during the year we started finding some very strange signs.
0:39:42 > 0:39:44A lot of the eggs had been successfully incubated,
0:39:44 > 0:39:47but when they hatched they just disappeared overnight.
0:39:47 > 0:39:49And then we started finding carcasses,
0:39:49 > 0:39:52chicks that had been healthy the day before were just dead.
0:39:54 > 0:39:56We were walking around,
0:39:56 > 0:39:59and nest after nest had a dead chick or the remains of a
0:39:59 > 0:40:03dead chick in and we realised right then that, actually,
0:40:03 > 0:40:06there's something really bad going on on this island.
0:40:07 > 0:40:11On both islands, scientists were finding young chicks with horrific
0:40:11 > 0:40:16injuries, wounds all over the body and most disturbingly, to the head.
0:40:19 > 0:40:23Richard needed to find out what was doing this, and fast.
0:40:23 > 0:40:27And his biggest clue was to be found in one particularly gruesome detail.
0:40:28 > 0:40:31It's quite hard to see what might have done this,
0:40:31 > 0:40:34but looking at some of them carefully we could also see these
0:40:34 > 0:40:36bite marks, little nibble marks.
0:40:37 > 0:40:40So what was eating the sea birds?
0:40:40 > 0:40:43Richard scoured the island for culprits.
0:40:44 > 0:40:47We knew the animals that were on the island.
0:40:47 > 0:40:50Other birds, subantarctic skuas and giant petrels,
0:40:50 > 0:40:53which will occasionally take a chick,
0:40:53 > 0:40:55but not to the extent that we were seeing.
0:40:55 > 0:41:01So, if it wasn't one of the usual suspects, who else could it be?
0:41:01 > 0:41:04We were scratching our heads as to what was going on.
0:41:04 > 0:41:08We were looking around and wondering whether rats or cats had come in on
0:41:08 > 0:41:11the island, but couldn't find any trace of those.
0:41:13 > 0:41:17But there was one resident that had previously been ignored.
0:41:17 > 0:41:21One that arrived with sailors less than 200 years ago.
0:41:24 > 0:41:27During the summer there are mice everywhere.
0:41:27 > 0:41:31We'd have mice burrowing into the tent at night after the food,
0:41:31 > 0:41:33mice in your pots and pans in the morning.
0:41:33 > 0:41:34I mean, it's horrific.
0:41:34 > 0:41:38A few breeding pairs had become thousands.
0:41:38 > 0:41:44But surely the common house mouse couldn't be responsible, could it?
0:41:44 > 0:41:46Typically, mice eat seeds, they eat insects,
0:41:46 > 0:41:48they eat bits of vegetation.
0:41:48 > 0:41:50They don't eat sea birds.
0:41:51 > 0:41:53A sweet little mouse eating a bird?
0:41:53 > 0:41:55Oh, come on.
0:41:55 > 0:41:58Nowhere on Earth had anyone witnessed anything like this.
0:41:58 > 0:42:02And yet all the evidence seemed to point right at them.
0:42:06 > 0:42:09Richard's theory was way too radical for some.
0:42:09 > 0:42:12As ornithologist Ross Wanless could well understand.
0:42:14 > 0:42:16Mice are probably the most widespread mammal on earth
0:42:16 > 0:42:17after human beings.
0:42:17 > 0:42:21They've co-existed with humans on islands all over the place.
0:42:21 > 0:42:24How come, after all of these years, someone pitches up and says,
0:42:24 > 0:42:27"Oh, by the way, mice are eating their way through
0:42:27 > 0:42:28"these giant sea birds"?
0:42:28 > 0:42:31No. That's not going to be a plausible situation.
0:42:31 > 0:42:33Surely, we would have figured that out long ago.
0:42:38 > 0:42:41Ross had to find out for himself.
0:42:41 > 0:42:44Writing his PhD thesis on invasive species,
0:42:44 > 0:42:46he travelled to Gough Island,
0:42:46 > 0:42:49determined to gather evidence to prove their suspicions.
0:42:51 > 0:42:54So he set up night-vision cameras and waited.
0:42:56 > 0:42:59At first, all was well.
0:42:59 > 0:43:00But then...
0:43:00 > 0:43:02As the night fell,
0:43:02 > 0:43:05the first mouse came out and started running around,
0:43:05 > 0:43:07and then more mice came and they started
0:43:07 > 0:43:09climbing all over the chick and eating it.
0:43:09 > 0:43:12It just... It was a scene from a horror movie.
0:43:12 > 0:43:17To witness this really gruesome brutal death is gut-wrenching.
0:43:17 > 0:43:19It's really, really difficult.
0:43:20 > 0:43:22This footage was irrefutable proof
0:43:22 > 0:43:27that the mice where eating these poor chicks alive.
0:43:27 > 0:43:29Feasting on the most accessible parts,
0:43:29 > 0:43:33the rump, the body and the head.
0:43:40 > 0:43:45So how did these islands become overrun with bird-eating mice?
0:43:45 > 0:43:50Typically, you see, the size of a mouse is controlled by its diet.
0:43:50 > 0:43:54So if it's eating seeds and grain you get a mouse-sized mouse.
0:43:54 > 0:43:56But here on these islands,
0:43:56 > 0:44:00they switched their diet to feed on birds, full of proteins and fats
0:44:00 > 0:44:04and, as a consequence, they got bigger and bigger.
0:44:04 > 0:44:06In fact, some of them even doubled their size.
0:44:08 > 0:44:11The reason we don't see mice attacks of this nature elsewhere
0:44:11 > 0:44:14is because mice are not alone on the islands.
0:44:14 > 0:44:16They are with rats or cats or other things which keep
0:44:16 > 0:44:18their numbers down,
0:44:18 > 0:44:20and keep their behaviour really quite subdued
0:44:20 > 0:44:22and wary of these other bigger things.
0:44:22 > 0:44:24On Gough, one of the few islands where
0:44:24 > 0:44:27mice are the only introduced mammal,
0:44:27 > 0:44:28under those circumstances, they can...
0:44:28 > 0:44:31Well, cat's away, mice will play.
0:44:31 > 0:44:33And play they did.
0:44:33 > 0:44:36Wiping out well over one million chicks
0:44:36 > 0:44:38every year on Gough Island alone.
0:44:40 > 0:44:44The scale of the carnage was really pretty phenomenal.
0:44:44 > 0:44:45Beyond a shade of a doubt,
0:44:45 > 0:44:48the mice are doing enough damage to drive both the
0:44:48 > 0:44:51albatross and the Atlantic petrel extinct.
0:44:51 > 0:44:55There are so few chicks fledged from either species in a year that
0:44:55 > 0:44:57the populations are not sustained on their own.
0:44:57 > 0:44:59There are other sources of mortality,
0:44:59 > 0:45:03but even if we fixed those the mice alone are driving them extinct.
0:45:03 > 0:45:05But there is one thing we can do.
0:45:07 > 0:45:10Wipe out the mice entirely,
0:45:10 > 0:45:13by dropping poisoned pellets from the air.
0:45:13 > 0:45:17With 10 million needed to clear just one island,
0:45:17 > 0:45:20intense fundraising is in full swing.
0:45:20 > 0:45:23But it will be worth it to stop these rare birds
0:45:23 > 0:45:25going the way of the dodo.
0:45:27 > 0:45:30Now, don't get me wrong. I like mice very much indeed.
0:45:30 > 0:45:34But the only way to deal with this savage,
0:45:34 > 0:45:37bird-eating strain is to poison them.
0:45:37 > 0:45:39And the hope is that, by doing so,
0:45:39 > 0:45:42we can finally bring this horror story to an end.
0:45:43 > 0:45:46From giant crabs in Norwegian waters,
0:45:46 > 0:45:50spiderlings clinging to their mothers' backs,
0:45:50 > 0:45:52to killer mice,
0:45:52 > 0:45:56when animals invade, the results can be truly terrifying.
0:45:58 > 0:45:59Coming up...
0:45:59 > 0:46:02a bizarre discovery deep underground.
0:46:05 > 0:46:07But first...
0:46:11 > 0:46:12Uganda.
0:46:14 > 0:46:16Kibale National Park...
0:46:18 > 0:46:21..and a group of our closest relatives
0:46:21 > 0:46:24have been caught doing something very strange.
0:46:28 > 0:46:33Researchers have been studying this one troop since the early '90s.
0:46:33 > 0:46:37After about 20 minutes of being with chimpanzees you realise that you're
0:46:37 > 0:46:41in the presence of something that is different from other animals.
0:46:47 > 0:46:50As Richard got to know the chimpanzees,
0:46:50 > 0:46:52he began to notice that certain members
0:46:52 > 0:46:56were doing something very subtle but very strange.
0:46:58 > 0:47:01There's lots and lots of play going on,
0:47:01 > 0:47:04and then all of a sudden what you will see is that somebody is just
0:47:04 > 0:47:08sitting there with a rock on his back.
0:47:11 > 0:47:14And you say, "Oh, what's going on there?"
0:47:18 > 0:47:22Certain individuals seem to have taken a bit of a shine to, well...
0:47:22 > 0:47:24rocks.
0:47:24 > 0:47:29They will pick up one of these objects and then keep it with them.
0:47:29 > 0:47:32And this wasn't just a quirk or a one-off.
0:47:33 > 0:47:35Over 15 years,
0:47:35 > 0:47:37Richard saw more and more chimpanzees
0:47:37 > 0:47:40indulging in this strange behaviour.
0:47:42 > 0:47:48They don't do anything with it other than keep it with them and make
0:47:48 > 0:47:51it sometimes seem comfortable.
0:47:52 > 0:47:53Just look at this.
0:47:53 > 0:47:57This young chimp has a rock carefully balanced on its back.
0:47:59 > 0:48:02Then it rolls off and it hurries to find it.
0:48:04 > 0:48:09And this one puts the rock very carefully in the crook of its leg.
0:48:10 > 0:48:12But it wasn't just rocks.
0:48:12 > 0:48:15Sometimes twigs and logs were treated in the same way.
0:48:15 > 0:48:19These objects were very clearly special.
0:48:19 > 0:48:20But why?
0:48:22 > 0:48:27Well, there's plenty of evidence that chimps are tool users.
0:48:27 > 0:48:30Rocks and twigs create perfect food-finding utensils.
0:48:32 > 0:48:37But these special objects weren't being used to get a snack.
0:48:37 > 0:48:41No. Their use pointed to something much stranger.
0:48:42 > 0:48:45I was following a mother and her son.
0:48:45 > 0:48:49He was eight years old and she was pregnant...
0:48:51 > 0:48:54..and as we went through the forest,
0:48:54 > 0:48:56he fell on a log deliberately and then kept it.
0:48:56 > 0:48:59Sometimes he'd put it on his back,
0:48:59 > 0:49:01sometimes he dragged it along
0:49:01 > 0:49:04like Christopher Robin carrying Winnie the Pooh.
0:49:04 > 0:49:07After a couple of hours his mother went up a tree.
0:49:07 > 0:49:10She relaxed by making a nest in the canopy,
0:49:10 > 0:49:14and he relaxed by making his own nest in the canopy.
0:49:14 > 0:49:15And then, a few minutes later,
0:49:15 > 0:49:18what he did was to make a new nest which was really,
0:49:18 > 0:49:22really small and then he went and got the log
0:49:22 > 0:49:24and brought it to the new nest and put it in the nest,
0:49:24 > 0:49:27and then he went back to his nest and went to sleep.
0:49:27 > 0:49:29There was a very, very striking example
0:49:29 > 0:49:32of how much attention they pay to an object
0:49:32 > 0:49:35when they picked one up like this.
0:49:35 > 0:49:37But the impression was that he was
0:49:37 > 0:49:41substituting an object for an infant.
0:49:45 > 0:49:50Yes, Richard believes that this is evidence that these chimps play with
0:49:50 > 0:49:55rocks and sticks like children play with dolls.
0:49:56 > 0:49:58It's absolutely incredible.
0:49:58 > 0:49:59But could it possibly be true?
0:50:01 > 0:50:03Well, for over a decade, Richard watched out
0:50:03 > 0:50:05for this extraordinary behaviour
0:50:05 > 0:50:08and began to notice a pattern.
0:50:10 > 0:50:15Firstly, it was only ever seen in young chimps.
0:50:15 > 0:50:17But that wasn't all.
0:50:17 > 0:50:20So as the observations mounted over the years,
0:50:20 > 0:50:21what we came to realise is that the
0:50:21 > 0:50:24females are doing this a lot more than the males.
0:50:24 > 0:50:25About three times as often.
0:50:29 > 0:50:33And the males will be rougher and the females will be more caring.
0:50:35 > 0:50:38They were carrying the rock dolls on their backs
0:50:38 > 0:50:41just as they would a chimpanzee baby.
0:50:44 > 0:50:48Like it or not, the types of toys that children are typically drawn to
0:50:48 > 0:50:51is dependent upon that child's gender.
0:50:51 > 0:50:57And now it seems that the same can be said for our chimpanzee cousins.
0:50:59 > 0:51:04Just like other youngsters, the girls play with rock dolls.
0:51:06 > 0:51:10And the boys, well, they're less interested in playing mum.
0:51:10 > 0:51:12But it's what this behaviour tells us
0:51:12 > 0:51:16about chimpanzee intelligence that is truly mind-blowing.
0:51:17 > 0:51:23It's a behaviour that the juveniles are copying from each other.
0:51:23 > 0:51:26It's a bit like, you know, conkers or something, or some of these
0:51:26 > 0:51:30children's games that can go on for generations
0:51:30 > 0:51:33without adults remembering how to do it,
0:51:33 > 0:51:37but the kids are passing it on to each other while they are kids.
0:51:45 > 0:51:49What this tells us about chimpanzees is that they share an enormously
0:51:49 > 0:51:52important trait with us humans.
0:51:52 > 0:51:54And that is imagination.
0:51:54 > 0:51:59You see, these chimps are pretending that a rock is a baby and that
0:51:59 > 0:52:02pretence wouldn't work without imagination.
0:52:02 > 0:52:05And when it comes to the study of animal cognition,
0:52:05 > 0:52:09this is a massive leap forward in terms of our understanding
0:52:09 > 0:52:13of just how intelligent chimpanzees really are.
0:52:16 > 0:52:19From proof that chimpanzees have imaginations...
0:52:21 > 0:52:23..to an unimaginable alien discovery.
0:52:29 > 0:52:31Caves.
0:52:31 > 0:52:33The Earth's crust is riddled with them.
0:52:33 > 0:52:37From tiny cracks to great caverns,
0:52:37 > 0:52:40some extending for hundreds of miles into the darkness.
0:52:42 > 0:52:47In these dark, dank places the weird thrives.
0:52:47 > 0:52:51Bizarre rock formations and extraordinary species.
0:52:51 > 0:52:54The darkness is alive with strange sights.
0:52:58 > 0:52:59But in September 2014,
0:52:59 > 0:53:04a research team delved deep under southern France and
0:53:04 > 0:53:07found a piece of pure science fiction.
0:53:10 > 0:53:15It was really like being in a Jules Verne book or something,
0:53:15 > 0:53:20that you arrive in this room and you find this fully unexpected
0:53:20 > 0:53:21spectacular thing.
0:53:27 > 0:53:32I'm not an experienced caver and so already to get there it was quite an
0:53:32 > 0:53:34adventure for me.
0:53:34 > 0:53:36It's hard. It's not, like, easy,
0:53:36 > 0:53:38you can't just walk in and get to the room.
0:53:38 > 0:53:40I was almost scared.
0:53:40 > 0:53:44It was a kind of an inhospitable environment.
0:53:44 > 0:53:48But it was exactly these harsh, inhospitable conditions
0:53:48 > 0:53:50that inspired Tomaso
0:53:50 > 0:53:54to spend two long hours squeezing through the gloom.
0:53:55 > 0:53:57I'm a geo-biologist.
0:53:57 > 0:54:02The main goal of my research is that of looking or studying the earliest
0:54:02 > 0:54:04evidence of life on Earth.
0:54:04 > 0:54:07Caves are a very good analogue for early Earth,
0:54:07 > 0:54:13because the conditions are very extreme, very inhospitable.
0:54:13 > 0:54:18Tomaso wasn't just looking for a new species deep underground.
0:54:18 > 0:54:20He was searching for a life form
0:54:20 > 0:54:25that might have existed at the beginning of life on Earth.
0:54:25 > 0:54:29And what he found blew him away.
0:54:29 > 0:54:31When I saw it, I really had the feeling
0:54:31 > 0:54:34that I was seeing a new creature like in
0:54:34 > 0:54:38one of these movies of Cronenberg, this horror movie from the '80s.
0:54:38 > 0:54:40It's really like if you find
0:54:40 > 0:54:42a mysterious creature.
0:54:46 > 0:54:51What they discovered were thousands of bizarrely beautiful mineral
0:54:51 > 0:54:56deposits called speleothems - strange, sparkling structures.
0:54:58 > 0:55:00I realised that some of these speleothems,
0:55:00 > 0:55:04some of the stalactites had very unusual shapes that are very
0:55:04 > 0:55:06difficult to explain. Very weird shapes.
0:55:08 > 0:55:10So what were they?
0:55:10 > 0:55:15First, he had to disprove the more simple explanations.
0:55:15 > 0:55:18A colleague proposed to me that these may have been roots
0:55:18 > 0:55:23because, in fact, they looked like roots coming from above,
0:55:23 > 0:55:25from the soil on top of the cave.
0:55:25 > 0:55:28And that maybe they were just encrusted
0:55:28 > 0:55:31by this calcium carbonate.
0:55:31 > 0:55:34But it was impossible because
0:55:34 > 0:55:35the surface is so far away
0:55:35 > 0:55:39that it was very unlikely that you would have roots
0:55:39 > 0:55:41that go so deep into the ground.
0:55:45 > 0:55:49So, if they weren't roots, what else could they be?
0:55:49 > 0:55:53Well, it wasn't just the shape that was mystifying.
0:55:53 > 0:55:55Then there was the other thing that, to me,
0:55:55 > 0:55:57was simply impossible to explain.
0:55:57 > 0:56:02In some cases you could see two of these branches merging in the
0:56:02 > 0:56:06middle of the room and this cannot be a coincidence.
0:56:06 > 0:56:10These weird things weren't just hanging from the roof,
0:56:10 > 0:56:13they seemed to be defying gravity.
0:56:13 > 0:56:17Tomaso was convinced they were growing towards each other.
0:56:18 > 0:56:23These weren't just rock formations, they were alive.
0:56:26 > 0:56:30But it was such a bizarre theory he needed to prove it.
0:56:31 > 0:56:35So Tomaso took a sample back to his lab at ETH, Zurich,
0:56:35 > 0:56:38and examined them at the molecular level.
0:56:39 > 0:56:41It was really possible
0:56:41 > 0:56:45to see that within this apparently completely dead
0:56:45 > 0:56:48abiotic branch or piece of speleothem
0:56:48 > 0:56:52there was some biomass, some organic material.
0:56:54 > 0:57:00Yes, organic material means living material.
0:57:00 > 0:57:05These deposits were created by tiny micro-organisms,
0:57:05 > 0:57:08the kind that could have once existed
0:57:08 > 0:57:10when life first evolved on Earth.
0:57:10 > 0:57:15Now, that's pretty exciting, but the scope of this discovery is huge.
0:57:15 > 0:57:19In fact, you could say that it's out of this world.
0:57:19 > 0:57:22You could imagine that something similar
0:57:22 > 0:57:25may exist or may form in another planet.
0:57:25 > 0:57:29Maybe it will not be so complete a structure,
0:57:29 > 0:57:33but when we find a tube on Mars we may say,
0:57:33 > 0:57:35"We know, we recognise that.
0:57:35 > 0:57:38"It's similar to what we've seen in the cave."
0:57:38 > 0:57:43Yes, with life on other planets likely to exist underground,
0:57:43 > 0:57:47protected from the sun's intense UV radiation,
0:57:47 > 0:57:49Tomaso might just have found a clue
0:57:49 > 0:57:54that could lead to the discovery of extra-terrestrial life.
0:57:54 > 0:57:55Amazing.
0:58:00 > 0:58:02From chimps with stone dolls,
0:58:02 > 0:58:06to rocks alive with intergalactic possibilities,
0:58:06 > 0:58:10we've discovered that imagination really is the key
0:58:10 > 0:58:12to all great discoveries.
0:58:14 > 0:58:18What a catalogue of the bizarre we've now enjoyed.
0:58:18 > 0:58:21And with strange tales and bemusing events
0:58:21 > 0:58:24coming from every corner of our planet,
0:58:24 > 0:58:27I think you've got to agree - the natural world, well,
0:58:27 > 0:58:29it's just plain weird.