0:00:02 > 0:00:04No matter how well we think we know our planet,
0:00:04 > 0:00:06the natural world still has the ability to surprise us,
0:00:06 > 0:00:10to 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 evermore readily on camera.
0:00:21 > 0:00:24So, we're going to bring you the strangest stories
0:00:24 > 0:00:26our world has to offer.
0:00:49 > 0:00:52A specialist skill can help an animal get ahead.
0:00:54 > 0:00:58Our stories show that the ability to create a superstructure
0:00:58 > 0:01:00can be crucial...
0:01:02 > 0:01:07..from an oozing slime clogging fishing nets,
0:01:07 > 0:01:09to the mystery of elaborate works of art
0:01:09 > 0:01:11appearing on the seabed.
0:01:13 > 0:01:15But first...
0:01:15 > 0:01:18to the heart of Pakistan,
0:01:18 > 0:01:20where, during the summer of 2010,
0:01:20 > 0:01:24reports of devastating floods spread throughout the world's media.
0:01:26 > 0:01:29Tens of thousands of people are being forced to leave their homes.
0:01:29 > 0:01:33Today brought new flood warnings in the southern Sindh Province.
0:01:34 > 0:01:36But from amongst all these news reports
0:01:36 > 0:01:39emerged an altogether different set of images.
0:01:45 > 0:01:49Russell Watkins, from the Department for International Development,
0:01:49 > 0:01:51was travelling to Sindh Province
0:01:51 > 0:01:55when he came across a scene so surreal
0:01:55 > 0:01:57it stopped him in his tracks.
0:01:57 > 0:02:01Nothing really prepared us for what we saw when we got there.
0:02:02 > 0:02:05What we were confronted with was quite spectacular.
0:02:05 > 0:02:08Every tree you could see, every piece of vegetation that you
0:02:08 > 0:02:12could see, for miles on end, was just cloaked in these enormous webs.
0:02:15 > 0:02:19Russell had the photographic evidence but not the explanation.
0:02:21 > 0:02:24So, who, or what, had turned these trees,
0:02:24 > 0:02:29in a remote corner of Pakistan, into giant, spooky cocoons?
0:02:32 > 0:02:35Silk specialist Chris Holland thinks he has the answer.
0:02:38 > 0:02:40Whilst these trees completely covered in silk may seem
0:02:40 > 0:02:42really unusual to the vast majority of us,
0:02:42 > 0:02:47there's actually a very simple, natural process occurring here.
0:02:47 > 0:02:50For Chris, there's only one culprit capable of spinning these
0:02:50 > 0:02:53sinister structures.
0:02:53 > 0:02:54Spiders.
0:02:55 > 0:02:59Just as the human population was forced from their homes
0:02:59 > 0:03:00by rising waters,
0:03:00 > 0:03:05so arachnid refugees were pushed back to the only dry land in sight.
0:03:05 > 0:03:08It just happens to be that when you have flooding events,
0:03:08 > 0:03:11they have very few places to go, and they usually go for high ground,
0:03:11 > 0:03:14and, in this case, it would be the trees.
0:03:14 > 0:03:17So, the types of spiders that you see in these trees
0:03:17 > 0:03:19are most likely the sheet-web building spiders.
0:03:19 > 0:03:21These are the spiders that you tend to find in the
0:03:21 > 0:03:24back of your garden, under your shed, or in your kitchen cupboards.
0:03:24 > 0:03:29But these were big enough to entomb your entire kitchen.
0:03:29 > 0:03:34Just how had these webs got so vast?
0:03:34 > 0:03:37Ironically, the answer lay in the very water
0:03:37 > 0:03:40that had trapped the spiders.
0:03:40 > 0:03:43A stagnant breeding ground for mosquitoes.
0:03:46 > 0:03:49So, when you get a few spiders confined to this really small space,
0:03:49 > 0:03:50but a lot of food around,
0:03:50 > 0:03:52for example, mosquitoes from these floodwaters,
0:03:52 > 0:03:56you suddenly would generate a huge population explosion,
0:03:56 > 0:03:59where all these spiders are having babies, these spiderlings,
0:03:59 > 0:04:01running amok around these trees,
0:04:01 > 0:04:03creating lots and lots of sheet-webs,
0:04:03 > 0:04:06which creates these huge, beautiful covering of silk,
0:04:06 > 0:04:08as we see in these photos.
0:04:08 > 0:04:11So, what Russell saw in Pakistan
0:04:11 > 0:04:17was really just normal spider behaviour pushed to extremes.
0:04:17 > 0:04:21And, as it turned out, it wasn't the only example.
0:04:21 > 0:04:22In March 2012,
0:04:22 > 0:04:27thousands of spiders escaped floods in Wagga Wagga, Australia,
0:04:27 > 0:04:30covering farmland in a creepy-crawly shroud.
0:04:30 > 0:04:35And what you're seeing in these photographs aren't actually webs,
0:04:35 > 0:04:38but millions of strands of dragline.
0:04:38 > 0:04:41That's the silk that spiders lay as their safety net
0:04:41 > 0:04:46and it's one of the most remarkable fibres in the natural world.
0:04:46 > 0:04:49So, spider silk isn't actually stored already reeled up
0:04:49 > 0:04:50like a fire hose inside the spider.
0:04:50 > 0:04:55It's actually stored as a gel and this gel is made up of proteins.
0:04:55 > 0:04:59As these proteins are pulled, they align into a hard, solid fibre.
0:04:59 > 0:05:02And it's the alignment, and how these proteins go
0:05:02 > 0:05:06together as building blocks, that gives silk it's amazing properties.
0:05:08 > 0:05:11This protein reshuffle creates one of the toughest
0:05:11 > 0:05:13fibres on the planet.
0:05:13 > 0:05:17A natural material so strong it can outperform steel.
0:05:21 > 0:05:22In the case of these spiders,
0:05:22 > 0:05:26the ability to spin their own safety line proved to be a life-saver.
0:05:28 > 0:05:32But our next superstructure has a much more poetic purpose.
0:05:34 > 0:05:35We are travelling to the waters off Japan,
0:05:35 > 0:05:38where, in September 2012,
0:05:38 > 0:05:41underwater photographer Yoji Ookata
0:05:41 > 0:05:43spotted something remarkable.
0:05:46 > 0:05:50An intricate, circular pattern carved into the sand.
0:05:51 > 0:05:56A peaked ring of ridges and waves, perfectly executed.
0:05:57 > 0:06:01Yoji began a stakeout, hoping to unmask the culprit.
0:06:02 > 0:06:06The artist responsible is a pufferfish.
0:06:08 > 0:06:11Yoji saw a male work tirelessly...
0:06:12 > 0:06:16..sculpting and perfecting his pattern over a number of days.
0:06:18 > 0:06:21And no-one in the scientific community had ever seen
0:06:21 > 0:06:23anything like it.
0:06:23 > 0:06:28Biologists like Dan Da Costa were blown away by its behaviour.
0:06:28 > 0:06:31Pufferfish are not well-known for swimming fast,
0:06:31 > 0:06:33or moving fast at all.
0:06:33 > 0:06:35And the way this pufferfish is moving,
0:06:35 > 0:06:38and moving his fins to make this nest,
0:06:38 > 0:06:39is just out of this world.
0:06:41 > 0:06:44But why does the pufferfish go to all of this effort?
0:06:47 > 0:06:51Well, the circle acts as a kind of oceanic love token.
0:06:54 > 0:06:56The female is drawn into the patterns
0:06:56 > 0:06:59and she lays her eggs in the central depression,
0:06:59 > 0:07:01where they're protected from currents.
0:07:03 > 0:07:06There's fish that do things to attract females,
0:07:06 > 0:07:08but not a single tiny fish like that
0:07:08 > 0:07:12builds a huge nest just to attract the female.
0:07:12 > 0:07:15And there's little pieces of corals
0:07:15 > 0:07:19and pieces of shells in it just to make it more attractive.
0:07:19 > 0:07:21That's quite unique. It's incredible.
0:07:21 > 0:07:25Talk about a grand romantic gesture.
0:07:29 > 0:07:31Even though scientists have discovered more
0:07:31 > 0:07:33than 120 different types of pufferfish,
0:07:33 > 0:07:36in both tropical and fresh water,
0:07:36 > 0:07:40they've never seen anything like that sculpturing ever before.
0:07:40 > 0:07:44When you think about it, more than 70% of our planet's surface
0:07:44 > 0:07:47is covered in water, much of it little explored,
0:07:47 > 0:07:50so there must be many more phenomenal things out there
0:07:50 > 0:07:53to be discovered.
0:07:53 > 0:07:56Whilst the pufferfish nest is a work of art,
0:07:56 > 0:08:00not all superstructures are quite so appealing.
0:08:01 > 0:08:04This next strange substance is unlikely to win any
0:08:04 > 0:08:06popularity contests.
0:08:10 > 0:08:14There is a very sticky situation facing fishermen in the Atlantic.
0:08:14 > 0:08:16'So, how do you get rid of all that slime?'
0:08:16 > 0:08:19They are pulling up their nets and pots, only to find them
0:08:19 > 0:08:22covered in slime.
0:08:23 > 0:08:28Armfuls of this colourless gloop is appearing in any one catch.
0:08:30 > 0:08:32With often more slime than fish,
0:08:32 > 0:08:35removing it from a haul is an absolute nightmare.
0:08:39 > 0:08:42Now, it's too common a complaint to be attributed
0:08:42 > 0:08:45to some freak event or rare natural phenomena.
0:08:45 > 0:08:50Something is creating enough of this substance to drive fisherman crazy.
0:08:50 > 0:08:52The question is...
0:08:52 > 0:08:53what?
0:08:57 > 0:09:00Well, the source of this mystery mucus
0:09:00 > 0:09:02can be found on the deep sea floor.
0:09:04 > 0:09:06The repugnant perpetrator...
0:09:08 > 0:09:10..is the hagfish.
0:09:12 > 0:09:17It's the undertaker of the deep, searching the murky bed for corpses.
0:09:20 > 0:09:23It uses a rasping tongue to pull flesh from bone.
0:09:26 > 0:09:29It will even wriggle inside a rotting corpse
0:09:29 > 0:09:32to devour the soft flesh under the skin...
0:09:33 > 0:09:36..literally eating the victim inside out.
0:09:38 > 0:09:42But nasty eating habits aside, the question remains,
0:09:42 > 0:09:47why would a creature that lives on the seabed need to produce slime?
0:09:50 > 0:09:54Well, aside from its willingness to eat sea floor scraps,
0:09:54 > 0:09:58the hagfish doesn't seem to have very much going for it.
0:09:58 > 0:10:02It's pretty much blind, has no jaws or tough scales.
0:10:02 > 0:10:05It looks vulnerable.
0:10:07 > 0:10:11But, in fact, the hagfish really is quite a success story.
0:10:11 > 0:10:15It's been around for a whopping 300 million years,
0:10:15 > 0:10:19which makes it one of the oldest fishes in the sea.
0:10:21 > 0:10:24And the secret to its success is slime.
0:10:26 > 0:10:29It's a defensive strategy so brilliant
0:10:29 > 0:10:33that it makes the hagfish, quite literally, untouchable.
0:10:37 > 0:10:41Professor Doug Fudge studies these master-slimers.
0:10:43 > 0:10:47So, the hagfish is essentially covered with slime glands,
0:10:47 > 0:10:50and when an animal is attacked by a predator...
0:10:50 > 0:10:54there is muscle in the area where it is touched
0:10:54 > 0:10:58that cause those slime glands to release their contents.
0:10:58 > 0:11:00There's actually a little mini-volcano of slime
0:11:00 > 0:11:02that comes out of the gland.
0:11:02 > 0:11:05It's reinforced with tens of thousands
0:11:05 > 0:11:07of silk-like protein fibres
0:11:07 > 0:11:09that we call slime threads.
0:11:09 > 0:11:13And it mixes with seawater, and it forms this large volume
0:11:13 > 0:11:17of very unusual, fibre-reinforced slime.
0:11:17 > 0:11:23A single hagfish can turn a bucket of water into slime in seconds.
0:11:25 > 0:11:27Ew! That is so gross!
0:11:27 > 0:11:32Which proves to be a pretty fantastic underwater weapon.
0:11:32 > 0:11:36In a recent study that was published by a group in New Zealand,
0:11:36 > 0:11:41they showed hagfish using their slime in a wild situation.
0:11:43 > 0:11:46The fibrous mucus is designed to choke a predator
0:11:46 > 0:11:49by clogging up its airways.
0:11:49 > 0:11:54The shark is left gagging as its gills fill with mucus.
0:11:57 > 0:12:00Every assailant is repulsed by a wall of slime.
0:12:02 > 0:12:04And the technique is so effective
0:12:04 > 0:12:08that the hagfish seems utterly unperturbed by the assault.
0:12:10 > 0:12:13So both predators and unsuspecting fishermen
0:12:13 > 0:12:15are getting the same treatment.
0:12:16 > 0:12:19But how does the hagfish prevent itself from becoming
0:12:19 > 0:12:22the victim of its own slimy strategy?
0:12:23 > 0:12:26They have an ingenious way of getting out of the slime.
0:12:27 > 0:12:31They'll tie their body in an overhand knot,
0:12:31 > 0:12:36and then they'll pass their body through the knot,
0:12:36 > 0:12:39and that will wipe the slime off of their body.
0:12:42 > 0:12:45A necessary skill
0:12:45 > 0:12:47for the ocean's most slippery character.
0:12:51 > 0:12:57Now, you may not like this, but humans produce slime too,
0:12:57 > 0:12:59in the form of snot.
0:12:59 > 0:13:02And what's remarkable is that hagfish slime
0:13:02 > 0:13:07and human snot are actually composed of very similar proteins.
0:13:07 > 0:13:09Now, hagfish use their slime
0:13:09 > 0:13:11to protect themselves from predators,
0:13:11 > 0:13:13and humans use their snot to trap
0:13:13 > 0:13:17harmful substances and then expel them from the body,
0:13:17 > 0:13:19so, when you think about it, both hagfish
0:13:19 > 0:13:23and humans are using slime as a front-line defence.
0:13:26 > 0:13:29These animals have proved that, in the natural world,
0:13:29 > 0:13:33it pays to be a master-craftsman.
0:13:33 > 0:13:36Whether you're a silk-spinner escaping the rising tide,
0:13:36 > 0:13:42a slime-producer defending yourself from attack,
0:13:42 > 0:13:45or a sand-sculptor looking for love...
0:13:48 > 0:13:51..a superstructure is crucial to success.