0:00:02 > 0:00:03No matter how well we think we know our planet,
0:00:03 > 0:00:06the natural world still has the ability to
0:00:06 > 0:00:10surprise us, to shock us, and maybe sometimes even to scare us
0:00:10 > 0:00:14with its extraordinary events and bizarre behaviour.
0:00:14 > 0:00:17And new technology means that nature's weirdest phenomena
0:00:17 > 0:00:21are being caught ever more readily on camera.
0:00:21 > 0:00:25So we're going to bring you the strangest stories our world
0:00:25 > 0:00:26has to offer.
0:00:28 > 0:00:30I've never seen anything like that before.
0:00:30 > 0:00:33From bizarre body snatchers...
0:00:34 > 0:00:37..to some rather surprise guests.
0:00:40 > 0:00:43There's the mystery of oozing ocean slime.
0:00:46 > 0:00:48And a butterfly blizzard.
0:00:48 > 0:00:49Do you see that, guys?
0:00:52 > 0:00:56With the help of scientists, experts and eye witnesses,
0:00:56 > 0:01:00we are going to try and unravel exactly what on Earth is going on.
0:01:23 > 0:01:25So, let's get cracking.
0:01:25 > 0:01:29First up, we reveal some astonishing super powers - specialist
0:01:29 > 0:01:34skills that help animals succeed in the toughest of environments.
0:01:37 > 0:01:41There's a group of insect jet-setters.
0:01:41 > 0:01:44A tiny amphibian so tough, it can cheat death.
0:01:46 > 0:01:49But our first weird event takes us to Zambia.
0:01:49 > 0:01:52and to the South Luanga National Park, where
0:01:52 > 0:01:56the star attraction is undoubtedly the African elephant.
0:01:57 > 0:02:01This charismatic animal is a must see for all of the visitors.
0:02:02 > 0:02:05But this is the largest land mammal
0:02:05 > 0:02:08and it doesn't take kindly to invasion of its private space.
0:02:12 > 0:02:18So, imagine the shock when, in 2009, a luxurious safari lodge received
0:02:18 > 0:02:20some surprise visitors.
0:02:21 > 0:02:25Staff and guests scattered as a herd of elephants
0:02:25 > 0:02:31sauntered straight through reception and out into the central courtyard,
0:02:31 > 0:02:34only stopping for a quick nose around the gift shop.
0:02:37 > 0:02:40What had brought these normally elusive animals straight
0:02:40 > 0:02:43through the lodge without a reservation?
0:02:45 > 0:02:49Elephant specialist Dr Kate Evans was surprised to hear about
0:02:49 > 0:02:52the elephants' sudden appearance.
0:02:52 > 0:02:54These are normally creatures of habit.
0:02:56 > 0:02:58Anywhere you go in Africa you often see
0:02:58 > 0:03:00these animal paths through the bush.
0:03:01 > 0:03:04Elephants do like to stay on these paths.
0:03:06 > 0:03:08It's obviously the route of least resistance.
0:03:08 > 0:03:11Been worn away over thousands of years.
0:03:11 > 0:03:15These paths guide the elephants to favourite food and water spots.
0:03:16 > 0:03:21The older individuals that have been around for 50-60 years potentially
0:03:21 > 0:03:25would have learnt from their mothers a long, long time ago that
0:03:25 > 0:03:29this is the route we need to travel to get to water in time of need.
0:03:29 > 0:03:33And so the youngsters over time will pick up this information.
0:03:34 > 0:03:38And it's this collective memory that keeps the elephants coming back
0:03:38 > 0:03:44to the same water holes year after year, generation after generation.
0:03:45 > 0:03:48So, if elephant movement is predictable,
0:03:48 > 0:03:51why the impromptu check-in at the lodge?
0:03:53 > 0:03:57Well, that's just it, you see, for this elephant herd it was
0:03:57 > 0:04:02the lodge, not themselves, that was the surprise arrival.
0:04:02 > 0:04:06I believe they've built the lodge on old elephant migration paths
0:04:06 > 0:04:10and the migration path went through the middle of the lodge and that's why they're
0:04:10 > 0:04:13choosing to go there rather than around.
0:04:13 > 0:04:16With a memory stretching back this far, it can be hard to adjust
0:04:16 > 0:04:18when suddenly things change.
0:04:19 > 0:04:21So what do you do when a lodge springs up
0:04:21 > 0:04:25right in the way of the route to your favourite mango tree?
0:04:27 > 0:04:30You go straight through it, of course, stairs and all.
0:04:30 > 0:04:34And now the elephants have become seasoned guests.
0:04:34 > 0:04:38It would appear that these elephants have somehow learned that
0:04:38 > 0:04:40they're not threatened here.
0:04:40 > 0:04:42And this small group of elephants have chosen to
0:04:42 > 0:04:45carry on with their migration route and go straight through the lodge.
0:04:48 > 0:04:51So, elephants aren't ones to let obstacles change
0:04:51 > 0:04:53the habits of a lifetime.
0:04:53 > 0:04:56Even the construction of a hydroelectric dam couldn't
0:04:56 > 0:04:58phase them.
0:04:58 > 0:05:01When Lake Kareba was built, in between Zimbabwe
0:05:01 > 0:05:05and Zambia, they found elephants swimming across these vast
0:05:05 > 0:05:07distances to get to the other side.
0:05:07 > 0:05:10And some well meaning people went out to try to bring them
0:05:10 > 0:05:12back with boats, and sort of head them off,
0:05:12 > 0:05:15but the elephant kept trying to get across.
0:05:15 > 0:05:17And eventually got to the other side.
0:05:17 > 0:05:20Discussion started amongst the community and they realised
0:05:20 > 0:05:24they were following their old migration routes to get from A to B.
0:05:29 > 0:05:34Collective memory is essential to the survival of elephants.
0:05:34 > 0:05:36It's been proven that in times of drought,
0:05:36 > 0:05:40an older member of the herd will lead that herd to a waterhole
0:05:40 > 0:05:45that hasn't been visited for years. Perhaps decades.
0:05:45 > 0:05:47And this is why poaching is so devastating.
0:05:47 > 0:05:50It's not only about the loss of the animal,
0:05:50 > 0:05:54it's about the loss of its knowledge, of its memories.
0:05:54 > 0:05:57And this is why elephants as a species have a very healthy
0:05:57 > 0:05:59respect for their elders.
0:06:01 > 0:06:06So the largest land mammal has a suitably super memory.
0:06:06 > 0:06:10But our next group of extreme jet-setters prove that when it comes to
0:06:10 > 0:06:14super powers, size isn't everything.
0:06:16 > 0:06:19In early October 2011, the Denning family
0:06:19 > 0:06:26were hiking through woodland in central Mexico when they became
0:06:26 > 0:06:31part of one of most extraordinary events in the natural world.
0:06:31 > 0:06:33Look at them all. Do you see that, guys?
0:06:35 > 0:06:38Millions of Monarch butterflies.
0:06:38 > 0:06:44- Wow!- A vision in orange, carpeting small stands of pines.
0:06:46 > 0:06:47This is awesome.
0:06:51 > 0:06:54Grant Sonnex found himself at the centre
0:06:54 > 0:06:56of a butterfly blizzard.
0:07:04 > 0:07:08Monarchs in their millions, that descend on very certain areas
0:07:08 > 0:07:12of trees in Mexico and California like clockwork, every year.
0:07:18 > 0:07:21Days before, these trees would have been bare.
0:07:24 > 0:07:28So where have all of these swathes of butterflies come from?
0:07:28 > 0:07:29And why are they here?
0:07:32 > 0:07:35Monarchs can be found throughout the United States,
0:07:35 > 0:07:38wherever their staple food, milkweed, is plentiful.
0:07:41 > 0:07:44This food source can take them as far north as Canada.
0:07:45 > 0:07:50Which, when the seasons change, can be a brutal place for a butterfly.
0:07:53 > 0:07:58Richard Fox has spent years studying the intricacies of butterfly behaviour.
0:07:59 > 0:08:01Basically, it's too cold in the winter time
0:08:01 > 0:08:05across most of the United States and certainly in Canada
0:08:05 > 0:08:08for these butterflies to survive.
0:08:08 > 0:08:11So they've got to move or die.
0:08:11 > 0:08:14The Monarchs are quite literally flying for their lives
0:08:14 > 0:08:15away from the cold north.
0:08:19 > 0:08:21But to reach these warm winter hideouts,
0:08:21 > 0:08:24well, that's a seriously long haul flight.
0:08:27 > 0:08:32These butterflies cover over 2,000 miles,
0:08:32 > 0:08:36and fly for anything up to ten weeks to reach these winter roosts.
0:08:37 > 0:08:41It's the kind of journey usually undertaken by birds or great herds
0:08:41 > 0:08:43of mammals.
0:08:43 > 0:08:46So how does a tiny insect manage it?
0:08:48 > 0:08:51Well, these are butterflies with super powers.
0:08:53 > 0:08:57We tend to think of butterflies as delicate creatures, blown around by the wind.
0:08:57 > 0:09:00But these Monarchs are serious flying machines.
0:09:00 > 0:09:02They have a brain the size of a pin head
0:09:02 > 0:09:05and yet they are able to navigate across a continent
0:09:05 > 0:09:08and they can fly at very high altitude, indeed people have
0:09:08 > 0:09:10seen them from aeroplane windows.
0:09:12 > 0:09:14And they're not flying blind.
0:09:16 > 0:09:19Monarchs come equipped with some serious inbuilt GPS.
0:09:21 > 0:09:26They have a time-compensated sun compass.
0:09:26 > 0:09:30In their brains they have a compass which uses
0:09:30 > 0:09:35sunshine as a way of working out north and south.
0:09:35 > 0:09:42And in their antennae, their feelers, they have a clock which enables them to take account
0:09:42 > 0:09:45for the passage of the sun across the sky.
0:09:46 > 0:09:48As they travel further south,
0:09:48 > 0:09:51these millions of Monarchs from all over the United States
0:09:51 > 0:09:56are funnelled together by the Gulf Coast and the Rocky Mountains.
0:09:56 > 0:10:01In a good year, it might be 150 million Monarchs.
0:10:01 > 0:10:05And rather than spread throughout the forest, they huddle close
0:10:05 > 0:10:09together, warmth in numbers against the cooler nights.
0:10:10 > 0:10:15But as the sun rises, and the day heats up,
0:10:15 > 0:10:19the butterflies leave the branches in an orange explosion!
0:10:31 > 0:10:35Not surprisingly, these winter roosts have become tourist hotspots.
0:10:38 > 0:10:41And for the people that live in these special areas
0:10:41 > 0:10:44the arrival of the Monarchs is cause for celebration.
0:10:46 > 0:10:50Lori Mannel is the director of the Museum of Natural History,
0:10:50 > 0:10:52in Pacific Grove, California.
0:10:54 > 0:10:57Also known as Butterfly Town USA.
0:10:58 > 0:11:02Pacific Grove takes its Monarchs very seriously.
0:11:10 > 0:11:17The first Saturday of October of every year all the school children in Pacific Grove gather together
0:11:17 > 0:11:19to welcome the Monarchs back to the town.
0:11:24 > 0:11:27The butterflies are the cultural icon of this town.
0:11:32 > 0:11:36But just how they find the exact spot that their family member
0:11:36 > 0:11:40travelled to the year before is still not fully understood.
0:11:40 > 0:11:45Nor is why they chose these particular stands of trees.
0:11:47 > 0:11:51When it comes to these extraordinary migrators,
0:11:51 > 0:11:55there are still more super powers left to be discovered.
0:12:01 > 0:12:05That Monarch migration is truly remarkable.
0:12:05 > 0:12:09Did you know that you witness a similarly Herculean butterfly
0:12:09 > 0:12:10effort here in the UK?
0:12:10 > 0:12:14You see, Painted Ladies like these move from Africa up through
0:12:14 > 0:12:16Europe every summer,
0:12:16 > 0:12:17and end up in our gardens.
0:12:17 > 0:12:20And we used to think that they just died here.
0:12:20 > 0:12:24Recently, however, we've spotted them flying back to Africa.
0:12:24 > 0:12:31So when you take in all of the generations, that's a round trip of more than 9,000 miles.
0:12:31 > 0:12:34Not bad for an insect that weighs less than a gram.
0:12:37 > 0:12:40Those butterflies are super migrators.
0:12:41 > 0:12:44But what do you do if you can't escape the cold?
0:12:45 > 0:12:49Let's travel to Canada, where we find an amphibian with
0:12:49 > 0:12:51an incredible survival strategy.
0:12:55 > 0:12:58Winters in the furthest reaches of the northern hemisphere
0:12:58 > 0:13:00are seriously tough.
0:13:01 > 0:13:06Only the hardiest animals can see though a season of snow and ice.
0:13:07 > 0:13:12But in this frozen world, where only the toughest survive, is one
0:13:12 > 0:13:13rather surprising resident.
0:13:17 > 0:13:19Rana Sylvatica, a wood frog.
0:13:19 > 0:13:23The only amphibian to be found north of the Arctic Circle.
0:13:25 > 0:13:29Now, you'd be forgiven for thinking that the idea of an Arctic frog
0:13:29 > 0:13:31is rather absurd.
0:13:33 > 0:13:37Other animals hibernate or migrate to warmer climes,
0:13:37 > 0:13:39but the frog can't do either.
0:13:42 > 0:13:46And being cold-blooded and fundamentally rather wet,
0:13:46 > 0:13:50you'd think that when winter came the frog would freeze.
0:13:53 > 0:13:57And you'd be right. It freezes solid.
0:14:00 > 0:14:08An ice block with no heartbeat or measurable brain activity - for all intents and purposes, it's dead.
0:14:10 > 0:14:13But this frog has a secret super power.
0:14:15 > 0:14:20Come the spring, it will come back to life.
0:14:23 > 0:14:26So, a Frankenstein frog that
0:14:26 > 0:14:30freezes solid in the winter only to come back to life in the spring.
0:14:31 > 0:14:34How on Earth could this be possible?
0:14:36 > 0:14:40For almost any other cold-blooded creature the cold is a killer.
0:14:41 > 0:14:45Their core temperature mimics that of their surroundings
0:14:45 > 0:14:50and if this falls too low, the water inside their blood will freeze.
0:14:52 > 0:14:57Forming ice crystals, daggers that tear cells and tissue apart.
0:15:00 > 0:15:04Some cold-blooded animals have emergency survival methods.
0:15:05 > 0:15:09Take the red-sided garter snake, for example.
0:15:09 > 0:15:12It produces a natural anti-freeze that can protect its major
0:15:12 > 0:15:15organs for several hours at a time.
0:15:16 > 0:15:19It's a lifesaver if it gets caught out in the cold.
0:15:21 > 0:15:24But the wood frog needs to survive freezing
0:15:24 > 0:15:26temperatures for months at a time.
0:15:29 > 0:15:33When winter comes, it must meet it, head on.
0:15:37 > 0:15:42As the first ice crystals begin to form on the frog's damp skin,
0:15:42 > 0:15:44its core temperature plummets.
0:15:49 > 0:15:53But it's at this life-or-death moment that the frog does something
0:15:53 > 0:15:55very clever.
0:15:55 > 0:15:57Firstly, its liver goes into overdrive,
0:15:57 > 0:16:00producing masses of glucose, a type of sugar,
0:16:00 > 0:16:05which it pumps into its cells to act as a type of anti-freeze.
0:16:05 > 0:16:09At the same time, it releases a protein which attaches to
0:16:09 > 0:16:12the water molecules between those cells
0:16:12 > 0:16:18so that when they freeze, ice crystals are too small to do any damage.
0:16:20 > 0:16:27Up to 65% of the frog's body is now ice, and its heart flat-lines.
0:16:29 > 0:16:32For most other animals, this would mean certain death.
0:16:33 > 0:16:35But not the wood frog.
0:16:36 > 0:16:41It can stay in this suspended animation for weeks on end
0:16:41 > 0:16:44until a change in temperature allows it to slowly thaw.
0:16:48 > 0:16:53But there's still no heart beat, no brain activity, it's not breathing.
0:16:54 > 0:16:58For all intents and purposes, this frog is just dead.
0:17:00 > 0:17:03So what will provide the vital spark?
0:17:05 > 0:17:08What's going to fuel its Frankenstein moment?
0:17:12 > 0:17:17The heart muscle, whose cells have been protected by glucose,
0:17:17 > 0:17:18starts to stretch.
0:17:18 > 0:17:25Energy is released, thousands of tiny static sparks that, like
0:17:25 > 0:17:29an internal defibrillator, create enough energy to shock the heart.
0:17:38 > 0:17:41Blood rushes around the frog's body.
0:17:45 > 0:17:48Within minutes, it's moving.
0:17:51 > 0:17:53All of the frog's senses have been
0:17:53 > 0:17:59restored and its time in the freezer is just a very cold dream.
0:18:01 > 0:18:04Now THAT is a super power!
0:18:06 > 0:18:14Clearly an amazing adaptation, which allows this frog to survive in extreme environments.
0:18:14 > 0:18:17Now, we like to complain about the cold, and we should,
0:18:17 > 0:18:21because extreme cold can be very dangerous to us humans.
0:18:21 > 0:18:26You see, our tissue lacks the frog's glucose-producing properties
0:18:26 > 0:18:30so when we get frostbite, the cells in our tissue freeze,
0:18:30 > 0:18:33and then die, and then rot.
0:18:33 > 0:18:36A very good reason to always remember your gloves.
0:18:40 > 0:18:44These stories reveal the extraordinary lengths that animals will go to to survive.
0:18:46 > 0:18:49Whether it's an elephant with food on the brain.
0:18:51 > 0:18:54A sub-zero frog frozen solid.
0:18:55 > 0:18:59Or a Monarch butterfly collecting some serious air miles.
0:19:01 > 0:19:06It just goes to show that sometimes it takes super powers to succeed.
0:19:11 > 0:19:15Although these stories have proved that what's on the inside really
0:19:15 > 0:19:17does count,
0:19:17 > 0:19:19having a super power is not the only way to survive.
0:19:19 > 0:19:24Our next set of stories show that the ability to create
0:19:24 > 0:19:30a super structure can be just as crucial, and just as weird.
0:19:30 > 0:19:33From an oozing slime clogging fishing nets...
0:19:34 > 0:19:38..to the mystery of elaborate works of art appearing on the sea bed.
0:19:40 > 0:19:43But first, to the heart of Pakistan,
0:19:43 > 0:19:47where, during the summer of 2010,
0:19:47 > 0:19:51reports of devastating floods spread throughout the world's media.
0:19:53 > 0:19:56Tens of thousands of people have been forced to leave their homes...
0:19:56 > 0:19:59Today brought new flood warnings in the southern Sindh province...
0:20:01 > 0:20:03But, from amongst all these news reports,
0:20:03 > 0:20:06emerged an altogether different set of images.
0:20:12 > 0:20:16Russell Watkins, from the Department for International Development,
0:20:16 > 0:20:18was travelling to Sindh province
0:20:18 > 0:20:23when he came across a scene so surreal it stopped him
0:20:23 > 0:20:24in his tracks.
0:20:24 > 0:20:28Nothing really prepared us for what we saw when we got there.
0:20:29 > 0:20:32What we were confronted with was quite spectacular.
0:20:32 > 0:20:34Every tree that you could see,
0:20:34 > 0:20:37every piece of vegetation you could see for miles and miles on end,
0:20:37 > 0:20:39was just cloaked in these enormous webs.
0:20:42 > 0:20:46The trees just looked like they were wrapped in candyfloss.
0:20:49 > 0:20:52It was very, very surreal, quite spooky in a way.
0:20:55 > 0:20:59Russell had the photographic evidence, but not the explanation.
0:21:01 > 0:21:05So who, or what, had turned these trees in
0:21:05 > 0:21:09a remote corner of Pakistan into giant, spooky cocoons?
0:21:12 > 0:21:16Silk specialist Chris Holland thinks he has the answer.
0:21:18 > 0:21:20Whilst these trees completely covered in silk may seem
0:21:20 > 0:21:22really unusual to the vast majority of us,
0:21:22 > 0:21:26there's actually a very simple natural process occurring here.
0:21:26 > 0:21:30For Chris, there's only one culprit capable of spinning
0:21:30 > 0:21:34these sinister structures - spiders.
0:21:36 > 0:21:39Just as the human population was forced from their homes
0:21:39 > 0:21:41by rising waters,
0:21:41 > 0:21:46so arachnid refugees were pushed back to the only dry land in sight.
0:21:46 > 0:21:48It just happens to be that when you have flooding events
0:21:48 > 0:21:52they have very few places to go, and they usually go for high ground,
0:21:52 > 0:21:53and in this case, the trees.
0:21:55 > 0:21:57So the types of spiders you see in these trees
0:21:57 > 0:21:59are most likely the sheet web building spiders.
0:21:59 > 0:22:02These are the spiders that you would tend to find
0:22:02 > 0:22:06in the back of your garden, under your shed, or in your kitchen cupboards.
0:22:06 > 0:22:09But these were big enough to entomb your entire kitchen.
0:22:09 > 0:22:13Just how had these webs got so vast?
0:22:14 > 0:22:19Ironically, the answer lay in the very water that trapped the spiders.
0:22:20 > 0:22:23A stagnant breeding ground for mosquitoes.
0:22:26 > 0:22:29So when you get a few spiders confined to this really small space,
0:22:29 > 0:22:33but a lot of food around, for example mosquitoes from these flood waters,
0:22:33 > 0:22:36you suddenly would generate a huge population explosion.
0:22:36 > 0:22:42Where all theses spiders are having babies, these spiderlings are running amok around these trees,
0:22:42 > 0:22:46creating lots and lots of sheet webs, which creates this huge beautiful coverings
0:22:46 > 0:22:48of silk, as we see in these photos.
0:22:50 > 0:22:55So what Russell saw in Pakistan was really just normal spider behaviour
0:22:55 > 0:22:56pushed to extremes.
0:22:57 > 0:23:00And, as it turned out, it wasn't the only example.
0:23:02 > 0:23:05In March 2012, thousands of spiders escaped floods
0:23:05 > 0:23:11in Wagga Wagga, Australia, covering farmland in a creepy-crawly shroud.
0:23:11 > 0:23:16What you're seeing in these photographs aren't actually webs, but millions
0:23:16 > 0:23:18of strands of dragline -
0:23:18 > 0:23:21that's the silk that spiders lay as their safety net.
0:23:21 > 0:23:25It's one of the most remarkable fibres in the natural world.
0:23:27 > 0:23:31Spider silk isn't actually stored already reeled up like a fire hose inside the spider.
0:23:31 > 0:23:34It's actually stored as a gel, and this gel is made up of proteins.
0:23:34 > 0:23:40And as these proteins are pulled, they align into a hard, solid fibre.
0:23:40 > 0:23:44And it's the alignment and how these proteins go together as building blocks that gives
0:23:44 > 0:23:46silk its amazing properties.
0:23:48 > 0:23:52This protein re-shuffle creates one of the toughest
0:23:52 > 0:23:54fibres on the planet.
0:23:54 > 0:23:57A natural material so strong it can outperform steel.
0:24:00 > 0:24:03It saved the spiders from flood water and now scientists
0:24:03 > 0:24:08are working on ways in which it might save the lives of humans too.
0:24:08 > 0:24:11If we really understand how spider silk is spun and processed,
0:24:11 > 0:24:14we may be able to reprocess it into types of shapes
0:24:14 > 0:24:16and structures that we can use inside the body,
0:24:16 > 0:24:21for example, making artificial bone, cartilage, or even trying to regenerate our nerves.
0:24:21 > 0:24:27Silk could act as a kind of scaffold on which new nerves cells can
0:24:27 > 0:24:28grow, bridging damage.
0:24:31 > 0:24:34So the concept of a Spiderman might not be
0:24:34 > 0:24:36so comic after all.
0:24:36 > 0:24:39But whilst this is exciting new science, as usual,
0:24:39 > 0:24:42we are lagging a long way behind nature.
0:24:42 > 0:24:46Birds, for instance, have been using spider silk for millennia
0:24:46 > 0:24:49and one species that you might know of that does is the very pretty
0:24:49 > 0:24:51little long-tailed tit.
0:24:51 > 0:24:55It uses spider silk to makes its fabulous little nest.
0:24:56 > 0:24:57What a thing!
0:25:00 > 0:25:01In the case of these spiders,
0:25:01 > 0:25:05the ability to spin their own safety line proved to be a life-saver.
0:25:06 > 0:25:10But our next super structure has a much more poetic purpose.
0:25:11 > 0:25:14We're travelling to the waters off Japan,
0:25:14 > 0:25:20where, in September 2012, underwater photographer Yoji Ookata
0:25:20 > 0:25:22spotted something remarkable.
0:25:25 > 0:25:29An intricate circular pattern carved into the sand.
0:25:30 > 0:25:34A peaked ring of ridges and waves, perfectly executed.
0:25:36 > 0:25:41In 50 years of diving, Yoji had never seen anything like it.
0:25:43 > 0:25:46But was this a scientific discovery?
0:25:46 > 0:25:48Or some sort of underwater hoax?
0:25:51 > 0:25:55Yoji began a stakeout, hoping to unmask the culprit.
0:25:57 > 0:26:01Who turned out to be more sub-aqua than extraterrestrial.
0:26:02 > 0:26:04The artist responsible is a pufferfish.
0:26:08 > 0:26:12Yoji saw a male work tirelessly - sculpting
0:26:12 > 0:26:15and perfecting his pattern over a number of days.
0:26:18 > 0:26:22No-one in the scientific community had ever seen anything like it.
0:26:22 > 0:26:26Biologists like Dan de Costa were blown away by its behaviour.
0:26:27 > 0:26:31Pufferfish are not known for swimming fast.
0:26:31 > 0:26:35Or moving fast at all. And the way this pufferfish is moving
0:26:35 > 0:26:39and moving his fins to make this nest, is just out of this world.
0:26:41 > 0:26:44But why does the pufferfish go to all this effort?
0:26:47 > 0:26:51Well, the circle acts as a kind of oceanic love token.
0:26:53 > 0:26:56The female is drawn into the patterns
0:26:56 > 0:26:58and lays her eggs in the central depression,
0:26:58 > 0:27:01where they are protected from currents.
0:27:03 > 0:27:07There's fish that do things to attract females, but not a single, tiny fish like that,
0:27:07 > 0:27:10builds a huge nest, just to attract the female.
0:27:10 > 0:27:18And lays little pieces of corals and little pieces of shells in it just to make it more attractive.
0:27:18 > 0:27:21That's quite unique, its incredible.
0:27:22 > 0:27:24Talk about a grand, romantic gesture.
0:27:28 > 0:27:33Even though scientists have discovered more than 120 different types of pufferfish,
0:27:33 > 0:27:39in both tropical and fresh water, they've never seen anything like that sculpturing ever before.
0:27:39 > 0:27:44When you think about it, more than 70% of our planet's surface is covered in water,
0:27:44 > 0:27:50much of it little explored, so there must be many more phenomenal things
0:27:50 > 0:27:52out there to be discovered.
0:27:52 > 0:27:55Whilst the pufferfish nest is a work of art,
0:27:55 > 0:28:00not all super structures are quite so appealing.
0:28:00 > 0:28:02This next strange substance
0:28:02 > 0:28:05is unlikely to win any popularity contests.
0:28:09 > 0:28:13There's a very sticky situation facing fishermen in the Atlantic.
0:28:13 > 0:28:15How do you get rid of all that slime?
0:28:15 > 0:28:17They're pulling up their nets and pots
0:28:17 > 0:28:21only to find them covered in slime.
0:28:21 > 0:28:23So does it ruin your prawns?
0:28:23 > 0:28:26An oceanic ooze is clogging their nets
0:28:26 > 0:28:29and having to be bailed from boats.
0:28:33 > 0:28:36Armfuls of this colourless goop
0:28:36 > 0:28:39is appearing in any one catch.
0:28:40 > 0:28:42With often more slime than fish,
0:28:42 > 0:28:45removing it from the haul is an absolute nightmare.
0:28:49 > 0:28:53It's too common a complaint to be attributed to some freak event,
0:28:53 > 0:28:55or rare natural phenomena.
0:28:55 > 0:28:58Something is creating enough of this substance
0:28:58 > 0:29:00to drive fishermen crazy.
0:29:00 > 0:29:02The question is, what?
0:29:07 > 0:29:09Well, the source of this mystery mucus
0:29:09 > 0:29:12can be found on the deep sea floor.
0:29:14 > 0:29:19The repugnant perpetrator is the hagfish.
0:29:22 > 0:29:27It's the undertaker of the deep, searching the murky bed for corpses.
0:29:30 > 0:29:33It uses a rasping tongue to pull flesh from bone.
0:29:36 > 0:29:39It will even wriggle inside a rotting corpse
0:29:39 > 0:29:42to devour the soft flesh under the skin,
0:29:42 > 0:29:46literally eating the victim inside out.
0:29:48 > 0:29:52But nasty eating habits aside, the question remains -
0:29:52 > 0:29:57why would a creature that lives on the sea bed need to produce slime?
0:29:59 > 0:30:04Well, aside from its willingness to eat sea-floor scraps,
0:30:04 > 0:30:08the hagfish doesn't seem to have very much going for it.
0:30:08 > 0:30:12It's pretty much blind, has no jaws or tough scales.
0:30:12 > 0:30:14It looks vulnerable.
0:30:17 > 0:30:21But in fact, the hagfish really is quite a success story.
0:30:21 > 0:30:25It's been around for a whopping 300 million years,
0:30:25 > 0:30:29which makes it one of the oldest fishes in the sea.
0:30:29 > 0:30:35And the secret to its success is slime.
0:30:37 > 0:30:39It's a defensive strategy so brilliant
0:30:39 > 0:30:43that it makes the hagfish quite literally untouchable.
0:30:46 > 0:30:51Professor Doug Fudge studies these master slimers.
0:30:53 > 0:30:57So the hagfish is essentially covered with slime glands.
0:30:57 > 0:31:00And when an animal is attacked by a predator,
0:31:00 > 0:31:04there's a muscle in the area where it's touched
0:31:04 > 0:31:07that causes those slime glands to release their contents.
0:31:07 > 0:31:10There's actually a little mini volcano of slime
0:31:10 > 0:31:13that comes out of the gland.
0:31:13 > 0:31:15It's reinforced with tens of thousands
0:31:15 > 0:31:19of silk-like protein fibres that we call slime threads
0:31:19 > 0:31:21and it mixes with seawater
0:31:21 > 0:31:24and it forms this large volume
0:31:24 > 0:31:27of very unusual fibre-reinforced slime.
0:31:28 > 0:31:34A single hagfish can turn a bucket of water into slime in seconds.
0:31:34 > 0:31:37Eww, that is so gross.
0:31:38 > 0:31:42Which proves to be a pretty fantastic underwater weapon.
0:31:42 > 0:31:46In a recent study that was published by a group in New Zealand
0:31:46 > 0:31:51they showed hagfish using their slime in a wild situation.
0:31:52 > 0:31:56The fibrous mucus is designed to choke a predator
0:31:56 > 0:31:58by clogging up its airways.
0:31:58 > 0:32:05The shark is left gagging as its gills fill with mucus.
0:32:06 > 0:32:10Every assailant is repulsed by a wall of slime.
0:32:12 > 0:32:14And the technique is so effective
0:32:14 > 0:32:18that the hagfish seems utterly unperturbed by the assault.
0:32:20 > 0:32:23So both predators and unsuspecting fishermen
0:32:23 > 0:32:25are getting the same treatment.
0:32:25 > 0:32:29But how does the hagfish prevent itself from becoming
0:32:29 > 0:32:32the victim of its own slimy strategy?
0:32:32 > 0:32:36They have an ingenious way of getting out of the slime.
0:32:37 > 0:32:40They'll tie their body in an overhand knot
0:32:40 > 0:32:45and then pass their body through the knot,
0:32:45 > 0:32:49and that'll wipe the slime off their body.
0:32:52 > 0:32:57A necessary skill for the ocean's most slippery character.
0:33:01 > 0:33:06Now you may not like this, but humans produce slime, too.
0:33:06 > 0:33:09In the form of snot.
0:33:09 > 0:33:13And what's remarkable is that hagfish slime and human snot
0:33:13 > 0:33:16are actually composed of very similar proteins.
0:33:16 > 0:33:21Now hagfish use their slime to protect themselves from predators
0:33:21 > 0:33:25and humans use their snot to trap harmful substances
0:33:25 > 0:33:27and then expel them from the body.
0:33:27 > 0:33:31So when you think about it, both hagfish and humans
0:33:31 > 0:33:34are using slime as a front-line defence.
0:33:35 > 0:33:39These animals have proved that in the natural world,
0:33:39 > 0:33:42it pays to be a master craftsman.
0:33:43 > 0:33:47Whether you're a silk spinner escaping the rising tide,
0:33:47 > 0:33:52a slime producer defending yourself from attack,
0:33:52 > 0:33:55or a sand sculptor looking for love,
0:33:58 > 0:34:01a super structure is crucial to success.
0:34:06 > 0:34:10So a specialist skill can help an animal get ahead,
0:34:10 > 0:34:14but what if you just can't survive on your own?
0:34:14 > 0:34:19Rather than admit defeat, this next selection of weirdness
0:34:19 > 0:34:23shows that enlisting some help can hold the key.
0:34:23 > 0:34:27There's a strange subterranean structure
0:34:27 > 0:34:29created by remarkable teamwork.
0:34:31 > 0:34:36But first, a chilling tale of some real-life zombies.
0:34:38 > 0:34:41Eric Williams from Delaware was mopping his kitchen floor
0:34:41 > 0:34:45when a dead beetle began to mutate in front of his eyes.
0:34:49 > 0:34:53From its body, something long and wormlike was emerging.
0:34:57 > 0:35:01And Eric wasn't the only one to witness this miniature horror.
0:35:01 > 0:35:04No idea what those things are.
0:35:04 > 0:35:07I see all these strange hairs moving around.
0:35:07 > 0:35:08What do you think that is?
0:35:08 > 0:35:09It's a cockroach.
0:35:09 > 0:35:11Look at the string coming out of it.
0:35:11 > 0:35:13Oh, my God!
0:35:13 > 0:35:16All of these records had that one thing in common.
0:35:16 > 0:35:19Be it a mopped floor or nearby puddle,
0:35:19 > 0:35:23the presence of water was triggering these writhing worms.
0:35:23 > 0:35:25That's disgusting.
0:35:25 > 0:35:28But what were they,
0:35:28 > 0:35:31and how had they got into the bodies of these insects?
0:35:33 > 0:35:36Biologist Janice Moore has spent a lifetime
0:35:36 > 0:35:39fascinated by this particular weird event.
0:35:42 > 0:35:45Whenever I was a child I used to see these long worms
0:35:45 > 0:35:49sort of squiggling around my grandfather's horse trough.
0:35:49 > 0:35:52And I was told they were horsehair worms,
0:35:52 > 0:35:54and that is their common name
0:35:54 > 0:35:58because legend has it that these worms come from horse hairs.
0:35:58 > 0:36:01Well, in reality, they're parasites, and they're parasites
0:36:01 > 0:36:05of crickets, grasshoppers, that sort of animal.
0:36:05 > 0:36:09These parasites live inside, say, the cricket,
0:36:09 > 0:36:12and grow up to be huge compared to the cricket.
0:36:12 > 0:36:15All coiled up. The cricket is almost total parasite.
0:36:16 > 0:36:21The hairworm larva develops snug inside the host insect's body.
0:36:22 > 0:36:25But to complete the life cycle, it has to breed,
0:36:25 > 0:36:28and to do this it needs to find water.
0:36:29 > 0:36:33And rather than leave the safety of the host,
0:36:33 > 0:36:34the hairworm has no qualms
0:36:34 > 0:36:37with making the poor insect do all of the legwork.
0:36:39 > 0:36:44This fiendish parasite alters the host's behaviour.
0:36:44 > 0:36:46So at that point the cricket
0:36:46 > 0:36:49becomes almost suicidally attracted to water.
0:36:49 > 0:36:52And they've been reported to jump into toilets,
0:36:52 > 0:36:54into dog watering bowls.
0:36:54 > 0:36:56And if the hairworm's big enough,
0:36:56 > 0:37:01the merest hint of moisture can be enough to tempt it out.
0:37:01 > 0:37:05- What is it?- I have never seen anything like that before.
0:37:05 > 0:37:09Keep an eye out for these miniature body snatchers,
0:37:09 > 0:37:12because they're found here in the UK too.
0:37:14 > 0:37:19In fact, in every corner of the globe, super sneaky parasite species
0:37:19 > 0:37:22have found ways to get others to do the hard work for them.
0:37:25 > 0:37:30For example, the mind controller that lurks in German gardens.
0:37:30 > 0:37:32So there's a really fun parasite.
0:37:32 > 0:37:35The scientific name is Leucochloridium.
0:37:35 > 0:37:39And it actually lives in the intestinal tract
0:37:39 > 0:37:41of a variety of songbirds.
0:37:41 > 0:37:44The parasitic flatworm reaches maturity
0:37:44 > 0:37:47inside the digestive system of the bird
0:37:47 > 0:37:51and casts out its eggs in the bird's droppings.
0:37:51 > 0:37:54This would be the end of the cycle for Leucochloridium
0:37:54 > 0:37:56if it weren't for the garden snail
0:37:56 > 0:37:59that finds bird droppings irresistible.
0:37:59 > 0:38:01When they eat these eggs,
0:38:01 > 0:38:05the egg hatches and the little larval parasite,
0:38:05 > 0:38:07a flatworm called a trematode,
0:38:07 > 0:38:10moves into the tentacles of the snail.
0:38:10 > 0:38:15And there it grows up into a kind of striped mass.
0:38:17 > 0:38:20The snail's tentacle is now one enormous,
0:38:20 > 0:38:23pulsating flatworm brood sac.
0:38:25 > 0:38:29But here our parasitic mastermind encounters a problem.
0:38:29 > 0:38:34Just like the hairworm, it can't breed in the snail.
0:38:34 > 0:38:36To lay its eggs, it once again
0:38:36 > 0:38:39needs to be back inside a bird's intestinal tract.
0:38:39 > 0:38:43So how does the fickle flatworm complete the cycle?
0:38:44 > 0:38:45Mind control.
0:38:47 > 0:38:52It forces the usually reclusive snail upward toward the light.
0:38:53 > 0:38:59Once exposed, the snail's tentacle is a pulsating grub on a plate.
0:39:00 > 0:39:03Birds will look at this and say, "A-ha! Good to eat!"
0:39:03 > 0:39:05and they'll eat it.
0:39:07 > 0:39:10And in that way, the lifecycle is complete.
0:39:12 > 0:39:15Now, the poor snail is the middleman,
0:39:15 > 0:39:19it might just get out alive - minus a tentacle.
0:39:19 > 0:39:21But other hosts are not so lucky.
0:39:23 > 0:39:27Our next parasite requires its host to make the ultimate sacrifice.
0:39:29 > 0:39:33So one of the most spectacular examples of zombie behaviour
0:39:33 > 0:39:35is that of ants infected with a fungus.
0:39:37 > 0:39:41If you're battling for space in the rainforest,
0:39:41 > 0:39:45hitching a ride on the back of an ant would seem like a clever tactic.
0:39:45 > 0:39:48But it's not nearly clever enough for the cordyceps fungus,
0:39:48 > 0:39:51which is a bit of a control freak -
0:39:52 > 0:39:54mind control, that is.
0:39:56 > 0:39:59The fungus enters the body through the ant's windpipe
0:39:59 > 0:40:04where it begins to extract nutrients from all but its major organs.
0:40:04 > 0:40:08As the fungus grows, it eats the ant alive,
0:40:08 > 0:40:11whilst leaving it with just enough of its faculties to move.
0:40:14 > 0:40:18And the reason why it does this is brilliantly devious.
0:40:21 > 0:40:25To cast spores, the fungus needs to be high.
0:40:25 > 0:40:28So it floods the ant's brain with chemicals,
0:40:28 > 0:40:30forcing it on an upward march.
0:40:32 > 0:40:34Having reached an optimum height,
0:40:34 > 0:40:39the ant has served its purpose and cordyceps devours its brain.
0:40:41 > 0:40:43Before, with a final flourish,
0:40:43 > 0:40:48it bursts through the exoskeleton and casts spores into the air.
0:40:49 > 0:40:52It's really a wonderful story if you happen to be reading about it
0:40:52 > 0:40:54and a really nasty story if you happen to be an ant.
0:41:00 > 0:41:01One of my favourite types of bodysnatcher
0:41:01 > 0:41:03actually lives in UK waters.
0:41:03 > 0:41:08The larvae of a species of tapeworm inhabits the stickleback.
0:41:08 > 0:41:11And just like all the other parasites we've been looking at,
0:41:11 > 0:41:15when it needs to breed, it needs another host - in this case, birds.
0:41:15 > 0:41:18Quite obviously, it doesn't leap out of the mouth of the stickleback
0:41:18 > 0:41:21into a passing bird. No.
0:41:21 > 0:41:24What it does is very cleverly modify the stickleback's behaviour,
0:41:24 > 0:41:26causing it to flip over onto its back
0:41:26 > 0:41:28and reveal its bright white belly,
0:41:28 > 0:41:33making it far more obvious to predators like herons.
0:41:36 > 0:41:39I know it's a sad end for the old stickleback,
0:41:39 > 0:41:41but you've got to admit that when it comes to parasites,
0:41:41 > 0:41:45mind control is a fiendishly effective survival technique.
0:41:47 > 0:41:50Bending the will of others for your own gain
0:41:50 > 0:41:54is not exactly the most altruistic of survival methods.
0:41:54 > 0:41:58Thankfully, our next story shows you just what can be achieved
0:41:58 > 0:42:00when you choose to work together.
0:42:02 > 0:42:06In May 2004, a group of scientists gathered in South America.
0:42:06 > 0:42:10At a very particular spot in rural Brazil
0:42:10 > 0:42:14they took up tools and began to dig.
0:42:17 > 0:42:22Over the next few days, they painstakingly excavated the area.
0:42:25 > 0:42:29And from the soil, something incredible began to emerge.
0:42:31 > 0:42:34They uncovered a vast network,
0:42:36 > 0:42:39some 50 metres squared,
0:42:40 > 0:42:44an architectural maze of different shapes and structures
0:42:44 > 0:42:47branching out into the ground.
0:42:47 > 0:42:51This subterranean design was precise,
0:42:51 > 0:42:55and too complex to have been created by chance.
0:42:55 > 0:42:57It had been engineered.
0:42:59 > 0:43:00But by what?
0:43:02 > 0:43:05What could have created this underground architecture?
0:43:10 > 0:43:14What the scientists had uncovered was a secret city.
0:43:16 > 0:43:20A giant home created for some of the smallest animals on the planet.
0:43:22 > 0:43:24Ants.
0:43:26 > 0:43:29For ant biologists like Ross Kirby,
0:43:29 > 0:43:32this experiment brought theory to life.
0:43:32 > 0:43:35This is the first time that we can literally
0:43:35 > 0:43:37see the bare bones of what they've actually built.
0:43:37 > 0:43:41They poured ten tonnes of cement into an empty leaf-cutter next
0:43:41 > 0:43:45over the course of three days.
0:43:45 > 0:43:47And once the cement had set,
0:43:47 > 0:43:51the scientists could cut away and reveal the underground metropolis
0:43:51 > 0:43:54of this leaf-cutter ant kingdom.
0:43:54 > 0:43:58This wasn't just your average ant nest.
0:43:58 > 0:44:01This was an entire ant city,
0:44:01 > 0:44:05going as deep as eight metres into the ground
0:44:05 > 0:44:08and masterminded by an estimated population
0:44:08 > 0:44:12of up to seven million leaf-cutter ants.
0:44:13 > 0:44:18But why does an ant need such an impressively complex home?
0:44:18 > 0:44:21There's brood chambers which are important
0:44:21 > 0:44:23because this is where the eggs develop.
0:44:23 > 0:44:24There's waste disposal chambers.
0:44:24 > 0:44:27There's also many different tunnels,
0:44:27 > 0:44:30not just to take the ants from chamber to chamber,
0:44:30 > 0:44:31but also to allow air
0:44:31 > 0:44:34to be completely circulated throughout the nest.
0:44:34 > 0:44:37Ants use pheromones to organise construction work
0:44:37 > 0:44:41and to guide them to and from foraging sites.
0:44:41 > 0:44:44These chemical trails help them work efficiently
0:44:44 > 0:44:47and stop them from getting lost.
0:44:47 > 0:44:51They ensure a steady stream of grass into the nest.
0:44:51 > 0:44:53But it's not to eat.
0:44:54 > 0:44:57The ants can't digest grass.
0:44:58 > 0:45:01Instead, they use the blades to feed a fungus,
0:45:01 > 0:45:04cultivated in special garden chambers.
0:45:06 > 0:45:09This fungus is the ants' preferred main meal,
0:45:09 > 0:45:13and when you've got seven million mouths to feed,
0:45:13 > 0:45:15that's a lot of fungus farming.
0:45:16 > 0:45:22A nest needs to be this size to support such a large colony.
0:45:22 > 0:45:26But it's almost inconceivable that something as small
0:45:26 > 0:45:31and simple as an ant could have created such an amazing structure.
0:45:33 > 0:45:35When looking at an entire ant colony,
0:45:35 > 0:45:39you shouldn't be thinking of it as seven million different individuals,
0:45:39 > 0:45:42it should be thought of as one great collective unit.
0:45:44 > 0:45:47A single ant by itself isn't really up to much.
0:45:47 > 0:45:49However, when you get up to seven million of them,
0:45:49 > 0:45:52interacting together, their behaviour can be quite complex.
0:45:54 > 0:45:58All of these ants working together for the good of the whole colony
0:45:58 > 0:46:03transform from individuals into a single living being.
0:46:04 > 0:46:11A super organism. One brain, seven million ants strong.
0:46:11 > 0:46:16It's this organisation that makes one of the smallest animals
0:46:16 > 0:46:19capable of such incredible engineering.
0:46:23 > 0:46:27So, clearly, being part of a super organism is beneficial.
0:46:27 > 0:46:31But a group mentality can also have its drawbacks.
0:46:32 > 0:46:36Kayla Brown was travelling through Peru in June 2008
0:46:36 > 0:46:39when she came across some ants behaving strangely.
0:46:41 > 0:46:46These army ants were spinning round and round in a constant circle.
0:46:46 > 0:46:48Kayla watched them spiralling for hours.
0:46:49 > 0:46:54Before, one by one, the ants began to collapse and die.
0:46:54 > 0:46:57And she wasn't the only one to have witnessed these peculiar
0:46:57 > 0:46:59death circles.
0:46:59 > 0:47:03But why were the usually organised ants on self-destruct?
0:47:05 > 0:47:08Well, it's most likely that these ants were out foraging
0:47:08 > 0:47:11when they got separated from the rest of their party.
0:47:12 > 0:47:15With the pheromone trail lost, the ants began to panic
0:47:15 > 0:47:17and follow each other's pheromones.
0:47:19 > 0:47:22This confused game of Follow My Leader forced them
0:47:22 > 0:47:24into a never-ending circle.
0:47:26 > 0:47:30And because ants aren't programmed to think like individuals,
0:47:30 > 0:47:33they didn't save themselves.
0:47:33 > 0:47:37Instead, the circle became tighter and faster
0:47:37 > 0:47:40until the ants simply died of exhaustion.
0:47:43 > 0:47:47Thankfully, these ant death circles are relatively rare events.
0:47:47 > 0:47:51Clearly proving that the benefits of teamwork must outweigh
0:47:51 > 0:47:53the potential for disaster.
0:47:53 > 0:47:57And of course, ants aren't the only animals that form super organisms.
0:47:57 > 0:47:59Take bees, for example.
0:47:59 > 0:48:01For a hive to be successful,
0:48:01 > 0:48:06thousands of bee brains must work together tirelessly and selflessly.
0:48:06 > 0:48:09And the benefits are security, bed and board.
0:48:09 > 0:48:11Clearly, when it comes to super organisms,
0:48:11 > 0:48:13great minds must think alike.
0:48:15 > 0:48:20These stories show the importance of enlisting some help.
0:48:20 > 0:48:23Whether it's a devious parasite controlling
0:48:23 > 0:48:25a host against its will...
0:48:25 > 0:48:29or an ant colony combining forces to build
0:48:29 > 0:48:31a subterranean megatropolis.
0:48:33 > 0:48:37Two brains, or seven million if you can manage it, are better than one.
0:48:42 > 0:48:45We've seen that the will to succeed can bring out the most
0:48:45 > 0:48:47ingenious in animal behaviour.
0:48:48 > 0:48:52But our final set of stories show that this survival drive can
0:48:52 > 0:48:55also have unwanted side effects.
0:48:56 > 0:49:00There are some reclusive rainforest residents with a sobering habit.
0:49:00 > 0:49:02But first, to Sweden,
0:49:02 > 0:49:06and an unfortunate case of animal inebriation.
0:49:06 > 0:49:11In September, 2011, local resident Per Johansson went out
0:49:11 > 0:49:16to investigate some unusual noises emanating from next door's garden.
0:49:18 > 0:49:22It was late evening when I came home from work in Gothenburg.
0:49:23 > 0:49:28And it was a very stormy, windy night. Much rain.
0:49:28 > 0:49:35When I heard a scream, it was like "Rrrrr". The sound was spooky.
0:49:35 > 0:49:38So I went in a bit more, I heard the scream again.
0:49:39 > 0:49:42Something was moving in a nearby tree.
0:49:43 > 0:49:47Then I took a few steps more and it was a moose.
0:49:53 > 0:49:55Eurasian elk, to give them their proper name,
0:49:55 > 0:50:00are a common sight in and among the forests that surround Saro.
0:50:00 > 0:50:03To find one lodged in your neighbour's apple tree,
0:50:03 > 0:50:06however, is perhaps less common.
0:50:06 > 0:50:08It was like this, you know.
0:50:08 > 0:50:12and it tried to get free then. "Rrrrrr!"
0:50:17 > 0:50:20So what had happened to this unfortunate elk?
0:50:20 > 0:50:22Per Johansson had his own theory.
0:50:24 > 0:50:26It had walked around the neighbourhood,
0:50:26 > 0:50:32eating a lot of apples. And it fermented in the stomach, you know.
0:50:32 > 0:50:37The elk was accused of being under the influence. And why was that?
0:50:37 > 0:50:40Well, getting stuck in an apple tree was a bit of a giveaway.
0:50:42 > 0:50:47Very red eyes. You know, "Rrrrr". It looks drunk!
0:50:48 > 0:50:52When the inebriated animal had tried to reach for more,
0:50:52 > 0:50:56it had slipped and got itself wedged into the tree.
0:50:56 > 0:51:00The story of a boozy moose was perfect front page fodder.
0:51:00 > 0:51:04But what's the truth behind this headline?
0:51:04 > 0:51:07Could eating fermented fruit make a wild animal drunk enough
0:51:07 > 0:51:11to get itself into such a compromising position?
0:51:12 > 0:51:16Well, fruit is a fantastic source of energy for animals,
0:51:16 > 0:51:18because it's full of sugars.
0:51:18 > 0:51:21But when yeasts, which are found on the skins of these fruits, react
0:51:21 > 0:51:26with all of the sugar, fermentation occurs and alcohol is produced.
0:51:29 > 0:51:32Professor Robert Dudley from Berkeley University studies
0:51:32 > 0:51:36the surprising relationship between animals and alcohol.
0:51:37 > 0:51:42Alcohol is a reliable indicator of the presence of sugar.
0:51:42 > 0:51:44And fruit-eating animals, they need to find sugar
0:51:44 > 0:51:47and if they don't eat over several days, they die.
0:51:47 > 0:51:48It's life or death.
0:51:49 > 0:51:53And if alcohol modules alert them to the presence of sugars,
0:51:53 > 0:51:56they can find it faster and consume it faster.
0:51:56 > 0:51:59Then they don't have to deal with the competition.
0:52:01 > 0:52:05So if alcohol is found in most fruits and nectar,
0:52:05 > 0:52:09then why aren't we seeing drunk animals everywhere?
0:52:09 > 0:52:11They're not drinking liquid alcohol,
0:52:11 > 0:52:14they're eating fruit which also happens to contain alcohol.
0:52:14 > 0:52:18So as they consume more alcohol, they're actually filing their gut
0:52:18 > 0:52:20with carbohydrates and lipids
0:52:20 > 0:52:23and all kinds of structural things associated with fruit.
0:52:23 > 0:52:26So they get full. They probably get full before they can get drunk.
0:52:26 > 0:52:29So, without hitting the bottle, it would be difficult
0:52:29 > 0:52:33for an animal to become drunk on naturally occurring alcohol.
0:52:33 > 0:52:34But it can happen.
0:52:36 > 0:52:40In the United States in 2007, necropsies carried out
0:52:40 > 0:52:45on some cedar waxwings found high levels of alcohol in their blood.
0:52:48 > 0:52:53These birds had gorged themselves on so much food
0:52:53 > 0:52:56that it had begun to ferment inside their bodies.
0:52:58 > 0:53:01The birds were illegally drunk, according to state law.
0:53:01 > 0:53:05There are actually a few cases of documented death by ethanol
0:53:05 > 0:53:08and true drunkenness in the animal kingdom.
0:53:10 > 0:53:13If the apples in that Swedish garden had been fermenting
0:53:13 > 0:53:16for long enough, then they could have produced enough
0:53:16 > 0:53:20alcohol for the unsuspecting elk to feel the effects.
0:53:20 > 0:53:24And its behaviour had all the hallmarks of drunkenness.
0:53:24 > 0:53:29Once stuck in the tree, the elk wasn't coming down quietly.
0:53:29 > 0:53:31It was time to call in reinforcements.
0:53:32 > 0:53:36Urban Bomgren from the fire department assessed the scene.
0:53:36 > 0:53:42- TRANSLATION:- We decided to use our winch at the front of the truck.
0:53:42 > 0:53:47And we tied a big rope around the tree and so we pulled it down.
0:53:47 > 0:53:55The tree was nearly 90 degrees, you know. When the moose fell out, pop.
0:53:55 > 0:53:59And just lay down. It pulled up its head and looked at us.
0:53:59 > 0:54:04It looked very tired and looks maybe a little bit hungover.
0:54:05 > 0:54:08Whilst its exploits became big news,
0:54:08 > 0:54:12the unfortunate elk had no choice but to sleep off the escapade.
0:54:14 > 0:54:18And a few days later, left the village none the worse for wear,
0:54:18 > 0:54:23although presumably it was off the apples for a while.
0:54:24 > 0:54:26Well, it's certainly a fun story.
0:54:26 > 0:54:29But sadly, because no tests were ever done,
0:54:29 > 0:54:32we can't be sure that the apples were to blame.
0:54:32 > 0:54:35And of course, you can't breathalyse an elk.
0:54:35 > 0:54:39But there has been another report recently of more drunken birds.
0:54:39 > 0:54:44This one much closer to home and one that's also been proved.
0:54:44 > 0:54:48A set of blackbirds were picked up in Cumbria in November, 2012.
0:54:48 > 0:54:52and the post-mortem results showed some typical signs.
0:54:52 > 0:54:56A belly full of berries and a high blood alcohol level.
0:54:56 > 0:54:59And what we think happened was, it was winter.
0:54:59 > 0:55:00There was a shortage of food,
0:55:00 > 0:55:03so they gorged on the fermenting berries,
0:55:03 > 0:55:06with no idea of the potential side effects.
0:55:06 > 0:55:09Then, they were killed in mid-air collisions,
0:55:09 > 0:55:13just going to prove that you shouldn't drink and fly!
0:55:16 > 0:55:20In the case of these birds, fermenting berries proved deadly.
0:55:22 > 0:55:25But what if alcohol in your diet is unavoidable?
0:55:27 > 0:55:31Our next story takes us to the rainforests of Malaysia,
0:55:31 > 0:55:36where we find two little mammals who are serious binge drinkers.
0:55:36 > 0:55:39One of the really interesting examples of alcohol exposure
0:55:39 > 0:55:42came out by German researchers working in Malaysia.
0:55:42 > 0:55:45And they described the slow loris.
0:55:45 > 0:55:49As well as pen-tailed tree shrews, these animals drink fermenting
0:55:49 > 0:55:52nectar all night from a certain kind of palm tree.
0:55:52 > 0:55:54So the flowers produce copious nectar
0:55:54 > 0:55:58and it then ferments in the warm, humid tropical environment.
0:55:58 > 0:56:00The animals come in and lap it up all night.
0:56:02 > 0:56:06Scientists studied these tiny mammals consuming the equivalent
0:56:06 > 0:56:10of beer-strength alcohol for hours on end every night.
0:56:11 > 0:56:13And this wasn't accidental.
0:56:13 > 0:56:17These animals were actively seeking alcohol.
0:56:20 > 0:56:24But if the side-effects of alcohol can be deadly, then why would
0:56:24 > 0:56:28wild animals choose such a potentially dangerous food source?
0:56:30 > 0:56:32Well, that's just it.
0:56:32 > 0:56:34Despite the mighty binge,
0:56:34 > 0:56:38the scientists could find no obvious signs of drunkenness.
0:56:38 > 0:56:41No strange behaviour, no dangerous side effects.
0:56:42 > 0:56:46So they tested hair samples, which confirmed that these animals
0:56:46 > 0:56:50had indeed been consuming alcohol long-term.
0:56:50 > 0:56:53In fact, the results drew a surprising parallel.
0:56:53 > 0:56:57There is a biochemical marker for alcoholism in modern humans.
0:56:57 > 0:56:59It's called Ethyl glucuronide
0:56:59 > 0:57:02and it turns up in hair samples of alcoholics.
0:57:02 > 0:57:05Otherwise, nobody exhibits this molecule.
0:57:05 > 0:57:09Except for the pen-tailed tree shrew and the slow loris
0:57:09 > 0:57:13and none of the other mammals in the rainforests have this marker.
0:57:13 > 0:57:17So their genetics confirmed that they were definitely consuming
0:57:17 > 0:57:20alcohol, but showed no signs of getting drunk.
0:57:21 > 0:57:23So what's their secret?
0:57:25 > 0:57:28Well, their bodies have evolved to process alcohol much more
0:57:28 > 0:57:30efficiently than our own.
0:57:30 > 0:57:34Which means that they can make the most of the calorie-rich
0:57:34 > 0:57:37nectar without any drunken side-effects.
0:57:41 > 0:57:43So the tree shrew could drink you under the table
0:57:43 > 0:57:45and never get a hangover.
0:57:46 > 0:57:49Whether you're an unfortunate elk, a boozy blackbird,
0:57:49 > 0:57:54or a sozzled cedar waxwing, the desire to fill your belly
0:57:54 > 0:57:57can have some very dangerous side-effects.
0:57:59 > 0:58:02Unless, of course, you're lucky enough to be a tree shrew.
0:58:06 > 0:58:07So there we are.
0:58:07 > 0:58:11We've delved into a catalogue of the most fun, the most foul,
0:58:11 > 0:58:13the most morbid and marvellous stories
0:58:13 > 0:58:15that our planet has to offer.
0:58:15 > 0:58:18And whether it's been bizarre animal behaviour
0:58:18 > 0:58:20or weird natural phenomena,
0:58:20 > 0:58:25it's had the very best of our brains completely baffled.
0:58:25 > 0:58:28But then, given the natural world's ability to astound,
0:58:28 > 0:58:33this only really leaves us with one final and inevitable question.
0:58:33 > 0:58:34What next?
0:58:37 > 0:58:39Subtitles by Red Bee Media Ltd