0:00:08 > 0:00:11The modern world is connected like never before -
0:00:11 > 0:00:14the very instant that something new, unexpected
0:00:14 > 0:00:17or downright strange happens,
0:00:17 > 0:00:19it's captured, uploaded
0:00:19 > 0:00:21and shared around the planet.
0:00:22 > 0:00:26That means that natural events that would've been dismissed as hearsay,
0:00:26 > 0:00:31urban legend or simply flights of fancy just a few years ago
0:00:31 > 0:00:36now come with good, first hand documentary evidence.
0:00:36 > 0:00:38From a mystery giant,
0:00:38 > 0:00:41terrorising the residents of an Australian neighbourhood...
0:00:41 > 0:00:43Oh, my goodness.
0:00:43 > 0:00:44SHRIEK
0:00:44 > 0:00:48..to a sea of green gunge along the Chinese coast...
0:00:49 > 0:00:53..and something strange in the Caribbean.
0:00:53 > 0:00:54Can you see them?
0:00:54 > 0:00:57Whoa!
0:00:57 > 0:00:59Using eyewitness testimony,
0:00:59 > 0:01:03leading experts and the top scientific brains,
0:01:03 > 0:01:06we are going to try to explain what on earth is going on
0:01:06 > 0:01:09with these weird natural events.
0:01:33 > 0:01:35Right, to kick off...
0:01:35 > 0:01:39..we start by taking the plunge, with some marine mysteries.
0:01:41 > 0:01:44There's danger lurking in the fish tank...
0:01:47 > 0:01:49..and a predator making a big splash.
0:01:49 > 0:01:52My wife was just screaming at the top of her lungs.
0:01:53 > 0:01:57But first, we head to the Caribbean.
0:02:01 > 0:02:04With perfect beaches and idyllic waters...
0:02:08 > 0:02:12..the islands of the Bahamas are a dream destination.
0:02:12 > 0:02:16But something unexpected is taking to the water.
0:02:26 > 0:02:28All of a sudden, these things
0:02:28 > 0:02:30were beginning to swim towards the boat.
0:02:30 > 0:02:31Which way are they?
0:02:31 > 0:02:33And I don't know what they are.
0:02:33 > 0:02:35Why are they in the water?
0:02:35 > 0:02:36Oh, my God!
0:02:36 > 0:02:38You guys, help us out - which way?
0:02:39 > 0:02:41I was trying to swim around them quickly
0:02:41 > 0:02:44and they were...faster than me.
0:02:44 > 0:02:45Can you see them?
0:02:45 > 0:02:47They were shooting every direction, these legs.
0:02:47 > 0:02:49SHOUTING
0:02:49 > 0:02:50But they were swimming fast.
0:02:54 > 0:02:57It was one of the most unusual things I've seen in my entire life.
0:03:02 > 0:03:04So here in paradise,
0:03:04 > 0:03:07just what is stalking these swimmers?
0:03:12 > 0:03:14Mike Corey is a film-maker from Canada
0:03:14 > 0:03:17and in 2011, he was working in the Caribbean.
0:03:19 > 0:03:24And he headed out to the tiny uninhabited island of Big Major Cay.
0:03:24 > 0:03:27That day, I was getting really excited to see sharks.
0:03:27 > 0:03:29We stopped for a lunch break
0:03:29 > 0:03:33and the boat operator got this big bag of...
0:03:33 > 0:03:36It was lettuce heads, French fries, just food scraps.
0:03:36 > 0:03:40And they were starting to dump it in the water, next to the boat.
0:03:40 > 0:03:42All of a sudden, these...things
0:03:42 > 0:03:45started bolting out of the woods.
0:03:45 > 0:03:47They were black, they were white, they were brown,
0:03:47 > 0:03:49I almost thought they were dogs...
0:03:49 > 0:03:50DOG BARKS
0:03:50 > 0:03:52Goats... GOAT BLEATS
0:03:52 > 0:03:53..I didn't really know.
0:03:53 > 0:03:56I didn't expect them to go into the water next.
0:03:56 > 0:03:58Mike couldn't work out what they were.
0:03:58 > 0:04:00But as they got closer,
0:04:00 > 0:04:04he realised, that gliding through the waves towards him...
0:04:04 > 0:04:07were swimming pigs.
0:04:07 > 0:04:08PIG WHINES
0:04:15 > 0:04:17- The world's a crazy place. - Look at it!
0:04:23 > 0:04:24I didn't know pigs could swim.
0:04:26 > 0:04:29We swam with them - I had my camera.
0:04:29 > 0:04:33Their feet were going crazy karate chops, every single direction.
0:04:34 > 0:04:36There were stingrays underneath, fish all around us -
0:04:36 > 0:04:38it was a beautiful day.
0:04:44 > 0:04:47One of the best days of my life, I'd say.
0:04:47 > 0:04:49Now, pigs may not be able to fly,
0:04:49 > 0:04:51but why do they need to swim?
0:04:52 > 0:04:56Well, in fact, paddling pigs have been known for some time
0:04:56 > 0:04:58and they're actually pretty good at it -
0:04:58 > 0:05:02as this footage of the late great Ralph the swimming pig shows.
0:05:03 > 0:05:06In his heyday, in 1970s Texas,
0:05:06 > 0:05:10he would enthral up to 350,000 visitors
0:05:10 > 0:05:11at Aquarena Springs.
0:05:13 > 0:05:14And pigs are one of the few animals
0:05:14 > 0:05:17that don't have functional sweat glands,
0:05:17 > 0:05:18so to cool themselves down,
0:05:18 > 0:05:21they need to wallow in mud or water.
0:05:21 > 0:05:25So it makes sense for them to know how to swim.
0:05:25 > 0:05:27They were better swimmers than we were.
0:05:27 > 0:05:29I was trying to swim around them quickly and they were...
0:05:29 > 0:05:31faster than me.
0:05:31 > 0:05:35The pigs were flailing their little pool cue hooves every direction.
0:05:35 > 0:05:37We had to kind of dodge around those, they were sharp.
0:05:37 > 0:05:39Well, I guess if you're a big animal like that
0:05:39 > 0:05:42and you've got some body fat, you'd float quite well.
0:05:43 > 0:05:45But pigs aren't usually found
0:05:45 > 0:05:48living on deserted islands in the Caribbean.
0:05:48 > 0:05:49So the big question is,
0:05:49 > 0:05:53how did these porcine paddlers end up in paradise?
0:05:54 > 0:05:58The theories about how they got here have become local legends.
0:05:58 > 0:06:03Could they have swum from another inhabited island?
0:06:03 > 0:06:05Well, in Scotland,
0:06:05 > 0:06:09two baby boar have recently been spotted making the 1.5 km swim
0:06:09 > 0:06:12from the Isle of Longa back to the mainland,
0:06:12 > 0:06:14so it's a possibility.
0:06:14 > 0:06:16Or perhaps these Caribbean pigs
0:06:16 > 0:06:20are descendants of a few that were once shipwrecked.
0:06:21 > 0:06:24Mike has found out about yet another story.
0:06:24 > 0:06:27From what I heard, there was a boy with a pig
0:06:27 > 0:06:30and he was scared his pig was going to get eaten
0:06:30 > 0:06:32by his family and his father.
0:06:32 > 0:06:35So he stole the pig away, put it on this island
0:06:35 > 0:06:37and would go every day to feed the pig.
0:06:37 > 0:06:39And after a while, more pigs arrived
0:06:39 > 0:06:42and he would still go and feed these animals.
0:06:44 > 0:06:47No-one knows exactly what happened,
0:06:47 > 0:06:49but the most likely explanation
0:06:49 > 0:06:51is that they were introduced by locals.
0:06:53 > 0:06:54But what's in no doubt
0:06:54 > 0:06:58is that once they got to the island, they thrived.
0:06:58 > 0:07:02And now, there are around 40 pigs that call this place home.
0:07:02 > 0:07:05So how have they been so successful?
0:07:05 > 0:07:08Well, I've got to tell you - pigs are clever.
0:07:08 > 0:07:13In fact, they're sometimes described as the world's 4th smartest animal.
0:07:13 > 0:07:15And they use this brain power
0:07:15 > 0:07:18to find food in the wild.
0:07:18 > 0:07:20So, stranded on a Caribbean island,
0:07:20 > 0:07:24they've learned a new way to get a free and nutritious meal.
0:07:24 > 0:07:28Rather than spend hours digging and searching for food,
0:07:28 > 0:07:32they've realised they can get hand-outs from passing boats.
0:07:33 > 0:07:34If I was a pig
0:07:34 > 0:07:37and I was stranded on a desert island and I saw a boat,
0:07:37 > 0:07:41I don't know if I would have the brains to just jump in the water,
0:07:41 > 0:07:43dodge the sharks, the stingrays -
0:07:43 > 0:07:47all of those things to go out and see if I could get lunch.
0:07:48 > 0:07:52But that's exactly what they've learned to do.
0:07:52 > 0:07:56The pigs have claimed this piece of paradise for themselves.
0:07:56 > 0:08:00And Pig Island really is a testament to the tenacity,
0:08:00 > 0:08:02the resourcefulness
0:08:02 > 0:08:05and the pioneering spirit of the not-so-humble pig.
0:08:11 > 0:08:14Now, from the bliss of the Caribbean
0:08:14 > 0:08:15to a hidden danger
0:08:15 > 0:08:18that could be lurking in your own home.
0:08:20 > 0:08:22Miami, in the USA.
0:08:22 > 0:08:25Life is usually pretty laid back in this sun-drenched city.
0:08:25 > 0:08:27But away from the beach,
0:08:27 > 0:08:29an invisible killer is on the loose.
0:08:30 > 0:08:33Bryan Kutcher is the owner of an aquarium shop,
0:08:33 > 0:08:36specialising in tropical fish and living coral.
0:08:36 > 0:08:40And he has seen a lot of strange things in his time.
0:08:40 > 0:08:44We've had fish give birth, a shark hatch out of an egg,
0:08:44 > 0:08:46um, blue-ringed octopus...
0:08:46 > 0:08:49But I've never seen anything mind-blowing as this.
0:08:49 > 0:08:51In January of 2013,
0:08:51 > 0:08:54Bryan noticed something pretty unusual.
0:08:54 > 0:08:57Everyday we come in the shop and we go through all our corals
0:08:57 > 0:09:00and make sure nothing has fallen, everything looks healthy
0:09:00 > 0:09:02and I noticed when I came in in the morning,
0:09:02 > 0:09:05all the corals were pulled to the middle of the rocks.
0:09:05 > 0:09:07So I pulled them all back out and I explain to everybody,
0:09:07 > 0:09:09if you're going to clean the glass,
0:09:09 > 0:09:12to please move the corals back when you're done.
0:09:12 > 0:09:15Everybody kind of denied it and said they didn't do it.
0:09:15 > 0:09:19The finger of blame pointed at some of Bryan's colleagues.
0:09:19 > 0:09:22So he really wasn't happy when it happened again.
0:09:24 > 0:09:26I was starting to get upset with everybody, cos I thought
0:09:26 > 0:09:28that they were actually just not bringing them back
0:09:28 > 0:09:30to where they were supposed to be.
0:09:30 > 0:09:32The following day, we got a coral shipment in.
0:09:32 > 0:09:35There's a coral called the "finger leather", which is a soft coral.
0:09:35 > 0:09:37I put it in, came back next morning
0:09:37 > 0:09:40and it was only about a half inch on each tentacle.
0:09:40 > 0:09:43Something had eaten about three to four inches.
0:09:43 > 0:09:45This was extremely odd.
0:09:45 > 0:09:47But what Bryan didn't know
0:09:47 > 0:09:51was that similar reports were coming in from all around the world.
0:09:51 > 0:09:53And the victims weren't just corals...
0:09:56 > 0:09:59..but entire fish, eaten alive.
0:10:05 > 0:10:07So who - or what -
0:10:07 > 0:10:11was responsible for this aquarium atrocity?
0:10:11 > 0:10:13Bryan wanted to investigate.
0:10:14 > 0:10:17I decided to take all the rock out of the aquarium
0:10:17 > 0:10:20and at that point, the aquarium was extremely murky, it was cloudy
0:10:20 > 0:10:22and out of nowhere,
0:10:22 > 0:10:24this giant thing just started swimming around the tank.
0:10:24 > 0:10:27It was like mayhem, we were in the tank, trying to go everywhere,
0:10:27 > 0:10:30trying to catch this thing, that we didn't really know what it was...
0:10:30 > 0:10:33The reaction was crazy. "Oh, my God, get a net - what is that?"
0:10:35 > 0:10:38And this is what Bryan caught -
0:10:38 > 0:10:40It's a bobbit worm.
0:10:40 > 0:10:42This bizarre looking creature
0:10:42 > 0:10:46usually lives in the waters of the Indo-Pacific ocean.
0:10:46 > 0:10:48But that's not the half of it.
0:10:49 > 0:10:53Because this turned out to be the size of a snake!
0:10:54 > 0:10:56And shockingly,
0:10:56 > 0:10:59other people are finding them lurking in their tanks too.
0:11:00 > 0:11:02Wow, that thing is massive!
0:11:02 > 0:11:03It is quite revolting.
0:11:03 > 0:11:05Oh, it's huge, Goops...
0:11:05 > 0:11:08I can't believe I've never seen him, though.
0:11:08 > 0:11:13This mega-worm can grow up to three metres in length..
0:11:13 > 0:11:16In the wild, they hide in the sediment on the ocean floor,
0:11:16 > 0:11:20using their highly tuned antennae to sense prey.
0:11:21 > 0:11:24When an unfortunate fish comes by,
0:11:24 > 0:11:27it strikes in a split second,
0:11:27 > 0:11:29as if from nowhere.
0:11:38 > 0:11:41Someone who can vouch for the worm's deadly bite
0:11:41 > 0:11:42is Emma Sherlock,
0:11:42 > 0:11:46the curator of invertebrates at the Natural History Museum in London.
0:11:47 > 0:11:50They are really, really powerful animals.
0:11:50 > 0:11:52They will attack with their jaws
0:11:52 > 0:11:55and it can be so fast and so vicious,
0:11:55 > 0:11:57they can actually snap fish in two.
0:11:58 > 0:12:02Definitely wouldn't want to get your fingers too close to these guys,
0:12:02 > 0:12:04because they've got really muscular pharynx
0:12:04 > 0:12:07and definitely give you a nasty nip.
0:12:07 > 0:12:09This is a highly weaponised worm,
0:12:09 > 0:12:12not to be messed with.
0:12:12 > 0:12:14But there's still one thing that doesn't add up.
0:12:14 > 0:12:17It's something that's been in this aquarium for a very long time,
0:12:17 > 0:12:19that we never noticed
0:12:19 > 0:12:21and we're in and out of the aquarium probably...
0:12:21 > 0:12:2330 times a day, 20 times a day.
0:12:23 > 0:12:28So how can a giant worm stay hidden in a fish tank?
0:12:29 > 0:12:31It seems staggering to people.
0:12:31 > 0:12:32But actually,
0:12:32 > 0:12:36what's happening is that when these animals are very small,
0:12:36 > 0:12:39they can fit very easily into little crevices
0:12:39 > 0:12:41in rocks and corals
0:12:41 > 0:12:43and when you're making up your aquarium,
0:12:43 > 0:12:46you put in these bits of coral,
0:12:46 > 0:12:48unknowing of what's lurking inside.
0:12:49 > 0:12:51As the bobbit worm grows,
0:12:51 > 0:12:54it hides under the sand and rocks.
0:12:54 > 0:12:55The only sign of its presence
0:12:55 > 0:12:59is the ever-increasing list of missing aquarium animals.
0:13:02 > 0:13:06And it's fantastic at basically playing a big game of hide and seek
0:13:06 > 0:13:09and so people don't actually know they're there,
0:13:09 > 0:13:13until they see the damage that they cause.
0:13:13 > 0:13:14Now, when we build aquariums,
0:13:14 > 0:13:17I'm always wondering what I'm going to find in the rocks.
0:13:17 > 0:13:19I'm wondering what I grab. Sometimes I wear gloves.
0:13:19 > 0:13:21I always wonder if something's going to pop out...
0:13:21 > 0:13:24As far as a four foot worm would be amazing,
0:13:24 > 0:13:26but it's always on my mind now.
0:13:26 > 0:13:28Who ever would have thought
0:13:28 > 0:13:32that there would be an organism as monstrous as the bobbit worm
0:13:32 > 0:13:34living in a fish tank?
0:13:34 > 0:13:36But you know, it does go to prove that in nature,
0:13:36 > 0:13:39if ever there's an opportunity,
0:13:39 > 0:13:40if ever there's a resource,
0:13:40 > 0:13:43something will evolve to exploit it.
0:13:47 > 0:13:49For our next event,
0:13:49 > 0:13:51we go to the west coast of Mexico
0:13:51 > 0:13:55and to an ocean predator on a completely different scale.
0:13:57 > 0:13:58In 2011,
0:13:58 > 0:14:02keen scuba divers Laura Howard and her husband, Richard
0:14:02 > 0:14:04decided to celebrate their 20th anniversary
0:14:04 > 0:14:06by doing something special.
0:14:08 > 0:14:11So they headed down to Baja in Mexico,
0:14:11 > 0:14:13for the holiday of a lifetime.
0:14:13 > 0:14:17This is the view from our beautiful, beautiful room.
0:14:17 > 0:14:19My husband loves underwater photography.
0:14:19 > 0:14:22We were scuba diving for the week - so excited about that.
0:14:24 > 0:14:29This part of the world is known for its magnificent underwater life
0:14:29 > 0:14:32and it wasn't long before they were meeting the locals.
0:14:37 > 0:14:40But on the second day, their dive was cut short,
0:14:40 > 0:14:42when the boat's captain reported
0:14:42 > 0:14:44seeing something strange off the boat.
0:14:46 > 0:14:49The couple went for a closer look.
0:14:49 > 0:14:51Out at the front, everything was calm.
0:14:53 > 0:14:56But out back, it was about to kick off.
0:15:01 > 0:15:04Whoo! Whoo!
0:15:04 > 0:15:07You got to be kidding me! 'Oh, my goodness...'
0:15:07 > 0:15:09These are killer whales. These are orca!
0:15:09 > 0:15:11Oh, my God!
0:15:11 > 0:15:14'I mean, there we have these enormous animals...'
0:15:14 > 0:15:17I mean, they're at the top of the food chain.
0:15:17 > 0:15:20And they're inches off the back of our boat.
0:15:20 > 0:15:24Whale breath just sprayed in my face, sprayed on the camera.
0:15:24 > 0:15:27They were huge, they were massive, they were bigger than the boat.
0:15:27 > 0:15:30And as we're looking around, there's not just one or two,
0:15:30 > 0:15:33there's about 20 in this pod.
0:15:36 > 0:15:41So why were these killer whales chasing the boat that day?
0:15:41 > 0:15:43And what were they after?
0:15:44 > 0:15:46Killer whales, or orca,
0:15:46 > 0:15:50are some of the ocean's largest and most powerful predators.
0:15:50 > 0:15:53They're intelligent, organised and ruthless.
0:15:53 > 0:15:57They're a true force to be reckoned with.
0:15:57 > 0:15:59The two types of killer whale that we know best know
0:15:59 > 0:16:02are resident and transient killer whales.
0:16:02 > 0:16:05Now, the resident groups tend to stay around coastlines
0:16:05 > 0:16:07and predominantly feed on fish,
0:16:07 > 0:16:12whereas the transient killer whales are fearsome hunters,
0:16:12 > 0:16:15roaming the oceans, looking for seals, sea lions
0:16:15 > 0:16:18and even whales to prey upon.
0:16:24 > 0:16:26So if we know they're capable of that...
0:16:26 > 0:16:27Right here, right here.
0:16:27 > 0:16:31..perhaps the killer whales saw Richard and Laura as lunch?
0:16:35 > 0:16:39Even being on a boat doesn't necessarily mean you're safe.
0:16:41 > 0:16:45When Weddell seals are found resting out of the water in Antarctica,
0:16:45 > 0:16:47it's no problem for the orca.
0:16:47 > 0:16:51The pod swim towards the iceberg in unison,
0:16:51 > 0:16:54to create a wave that topples the seal into the water.
0:16:54 > 0:16:57And I'm afraid there's only one winner.
0:17:02 > 0:17:06So have these Mexican killers learned a similar trick?
0:17:06 > 0:17:10Well, perhaps the answer lies with some of their relatives?
0:17:11 > 0:17:14Despite the name, killer whales, are in fact,
0:17:14 > 0:17:16the largest member of the dolphin family.
0:17:19 > 0:17:23And smaller dolphins are known for surfing waves
0:17:23 > 0:17:25and riding the bows of boats.
0:17:25 > 0:17:27So is there a link?
0:17:27 > 0:17:31The one man who can help shed some light on this mystery
0:17:31 > 0:17:34is zoologist Mark Cawardine.
0:17:34 > 0:17:36It's amazing how many times I've been on a boat,
0:17:36 > 0:17:38travelling in one direction
0:17:38 > 0:17:40and you're passing a school of dolphins
0:17:40 > 0:17:44and they will turn around 180 degrees
0:17:44 > 0:17:47to come up to the boat and play with it.
0:17:47 > 0:17:49And they've obviously realised over the years
0:17:49 > 0:17:52that boats just mean fun.
0:17:52 > 0:17:54This behaviour, though, actually evolved
0:17:54 > 0:17:58long before the dolphins had boats to create the perfect ride.
0:17:58 > 0:18:00You get a big whale like a blue whale,
0:18:00 > 0:18:02like the size of a Boeing 737,
0:18:02 > 0:18:06these little tiddly dolphins will race around the blue whale
0:18:06 > 0:18:09and annoy it and the whale will surge, you know?
0:18:09 > 0:18:12Just out of frustration and anger maybe
0:18:12 > 0:18:14and create a bow wave in front of it
0:18:14 > 0:18:16and the dolphin would get a few seconds of just
0:18:16 > 0:18:18playing in the bow wave.
0:18:18 > 0:18:20When boats and ships came along,
0:18:20 > 0:18:22they couldn't have believed their luck,
0:18:22 > 0:18:24because there are these things that are creating bow waves
0:18:24 > 0:18:28all day long, all night long and they can play as much as they want.
0:18:28 > 0:18:30There is still one crucial difference, though.
0:18:30 > 0:18:33The dolphins are being pushed along at the front of boat.
0:18:33 > 0:18:35But on this day in Mexico,
0:18:35 > 0:18:37the killers were at the back,
0:18:37 > 0:18:39in the boat's wake.
0:18:39 > 0:18:41So can this really be the same thing?
0:18:41 > 0:18:44Well, there's no doubt the whales will have gone to the boat
0:18:44 > 0:18:47because they just wanted to have a good time.
0:18:47 > 0:18:51But this type of play behaviour isn't exclusively for fun.
0:18:52 > 0:18:56Swimming close together, they're actually learning to hunt.
0:18:57 > 0:19:00It's quite a useful technique to develop and learn,
0:19:00 > 0:19:02because it's useful in hunting, you know?
0:19:02 > 0:19:04They'll be working as a team when they're hunting
0:19:04 > 0:19:07and they'll instinctively know when to take over,
0:19:07 > 0:19:09when to move position.
0:19:10 > 0:19:12This orchestrated training session
0:19:12 > 0:19:16gives the killer whales an advantage when it comes to a real hunt.
0:19:16 > 0:19:19Building stamina and developing teamwork
0:19:19 > 0:19:21in this man-made surf school.
0:19:24 > 0:19:25So, although it looks like
0:19:25 > 0:19:28Richard and Laura weren't on the menu that day,
0:19:28 > 0:19:31it is entirely possible that the killer whales
0:19:31 > 0:19:36were using the boat to fine-tune their hunting skills -
0:19:36 > 0:19:39the skills that make killer whales
0:19:39 > 0:19:42one of the most feared predators in the ocean.
0:19:46 > 0:19:48What all these events show
0:19:48 > 0:19:53is that ocean is a fascinating source of weird surprises,
0:19:53 > 0:19:56whether it's pigs in paradise,
0:19:56 > 0:19:58a worm the size of snake...
0:19:59 > 0:20:02..or a killer whale academy.
0:20:02 > 0:20:06With the ocean covering 71% of the earth's surface,
0:20:06 > 0:20:09it makes you wonder what else is out there.
0:20:11 > 0:20:13Whilst it's easy to be impressed
0:20:13 > 0:20:16by big, bold and brazen displays of behaviour,
0:20:16 > 0:20:20our next set of stories is no less astonishing
0:20:20 > 0:20:23and it pits the small against the mighty.
0:20:25 > 0:20:28Coming up, a wasp that seems to have a death wish...
0:20:29 > 0:20:33..and a stoat that appears to have lost its mind.
0:20:36 > 0:20:39But first, to North America and to the United States...
0:20:40 > 0:20:43..famous for fast food
0:20:43 > 0:20:45and dedicated meat-eaters.
0:20:47 > 0:20:51On average, Americans eat 125 kg of meat
0:20:51 > 0:20:53every single year -
0:20:53 > 0:20:57if any nation could be said to be built on the stuff,
0:20:57 > 0:20:59this is it.
0:20:59 > 0:21:01But the burgers have gone bad.
0:21:02 > 0:21:05Almost overnight, people have started to suffer
0:21:05 > 0:21:08life-threatening allergic reactions to meat...
0:21:08 > 0:21:11I was fighting for air and I was having difficulty breathing.
0:21:11 > 0:21:13I was going to pass out on my feet.
0:21:13 > 0:21:15..and it's spreading,
0:21:15 > 0:21:18taking down even the most devoted carnivores.
0:21:19 > 0:21:22Hamburger, ribs, meatloaf, meatballs, bacon -
0:21:22 > 0:21:23all off my list.
0:21:23 > 0:21:26Never in my life did I imagine something like this
0:21:26 > 0:21:28would change my life so drastically.
0:21:31 > 0:21:35Fred Marienfeld is a physical education coach from Long Island.
0:21:36 > 0:21:38In August 2011,
0:21:38 > 0:21:41his world collapsed.
0:21:41 > 0:21:43I was out playing softball one evening and I came home
0:21:43 > 0:21:46and had a normal meal - threw a couple of hamburgers on the grill
0:21:46 > 0:21:47and cooked them up had some dinner
0:21:47 > 0:21:50and watched the ball game for a little while and went to bed.
0:21:50 > 0:21:52About four o'clock in the morning,
0:21:52 > 0:21:55I woke up and I was covered in hives, from head to toe.
0:21:55 > 0:21:58Itching, scratching - I couldn't get any relief -
0:21:58 > 0:21:59it just came out of nowhere
0:21:59 > 0:22:02and I knew I was having a reaction, but to what, I didn't know.
0:22:02 > 0:22:04It was extremely serious.
0:22:04 > 0:22:05I couldn't breath,
0:22:05 > 0:22:08I couldn't get enough air, I was actually gasping for air,
0:22:08 > 0:22:10thinking I had a blockage in my airway.
0:22:10 > 0:22:13My wife got me in the car and took me to the emergency room.
0:22:13 > 0:22:18But being rushed to hospital was just the start of Fred's ordeal.
0:22:18 > 0:22:20After leaving the emergency room,
0:22:20 > 0:22:22I made an appointment to see an allergist, just to kind of...
0:22:22 > 0:22:25To figure what exactly was causing this reaction in me.
0:22:25 > 0:22:27After a series of tests,
0:22:27 > 0:22:31Fred was told he was allergic to red meat.
0:22:31 > 0:22:32Completely off my diet -
0:22:32 > 0:22:37bacon, cheeseburgers, meatballs, meatloaf, ribs - no more.
0:22:37 > 0:22:38It was crushing.
0:22:40 > 0:22:44So who or what had caused this terrible reaction?
0:22:44 > 0:22:47And would Fred ever be able to eat meat again?
0:22:49 > 0:22:52Dr Erin McGintee is Fred's allergist
0:22:52 > 0:22:56and she was instrumental in unravelling this meaty mystery.
0:22:57 > 0:23:00So the first patient I ended up diagnosing with this allergy
0:23:00 > 0:23:02was in 2010.
0:23:02 > 0:23:04It was one of those things where you think,
0:23:04 > 0:23:07"Oh, that's crazy, nobody's allergic to meat."
0:23:07 > 0:23:08But they were.
0:23:08 > 0:23:11And it only got crazier.
0:23:11 > 0:23:14Erin started to see an increase in these meat allergies,
0:23:14 > 0:23:17but doctors in other parts of the states
0:23:17 > 0:23:19weren't seeing the same pattern.
0:23:19 > 0:23:21So what was going on?
0:23:21 > 0:23:23Perhaps the meat was contaminated -
0:23:23 > 0:23:26or was it something else entirely?
0:23:26 > 0:23:31One of my patients suspected he was allergic to shellfish,
0:23:31 > 0:23:34because he had a couple of episodes hours after eating shellfish.
0:23:34 > 0:23:36But then he said, but the most recent time it happened,
0:23:36 > 0:23:38I hadn't even eaten shellfish.
0:23:38 > 0:23:40One by one,
0:23:40 > 0:23:43all the usual suspects were ruled out.
0:23:43 > 0:23:46But finally, Erin had a breakthrough.
0:23:46 > 0:23:49It wasn't that the meat had changed -
0:23:49 > 0:23:50it was Fred.
0:23:50 > 0:23:53And the culprit was lurking in the grass.
0:23:58 > 0:24:00The Lone Star Tick.
0:24:02 > 0:24:04But what was the connection?
0:24:06 > 0:24:08Now, ticks are small parasites,
0:24:08 > 0:24:11that specialise in sucking the blood of vertebrates.
0:24:11 > 0:24:14They're the sort of vampires of the parasite world.
0:24:16 > 0:24:20They lie in wait, often in long grass
0:24:20 > 0:24:24and use special sensory organs at the tip of their front legs
0:24:24 > 0:24:27to detect the presence of a host.
0:24:28 > 0:24:30When a target comes by,
0:24:30 > 0:24:31they make their move.
0:24:32 > 0:24:35And the victim doesn't feel a thing.
0:24:35 > 0:24:38The tick saliva contains anaesthetic properties.
0:24:40 > 0:24:43By the time Fred realised he'd been bitten,
0:24:43 > 0:24:45it was too late.
0:24:46 > 0:24:49OK, so we know who dunnit,
0:24:49 > 0:24:51but how on earth is this tiny tick
0:24:51 > 0:24:54forcing people to become vegetarian?
0:24:54 > 0:25:00All non-primate mammals express a carbohydrate called alpha-gal
0:25:00 > 0:25:02throughout all the cells in their body.
0:25:02 > 0:25:05When we eat it normally, it doesn't cause us a problem,
0:25:05 > 0:25:07it's not dangerous to people.
0:25:07 > 0:25:10We've been eating meat our whole life - it's not a problem.
0:25:10 > 0:25:14But ticks can pick up this alpha-gal when they feed from mammals
0:25:14 > 0:25:16and it stays inside them.
0:25:16 > 0:25:18When a tick bites a human,
0:25:18 > 0:25:20a small amount of this alpha-gal
0:25:20 > 0:25:23gets transferred into the bloodstream.
0:25:23 > 0:25:26And this is when it becomes a problem.
0:25:28 > 0:25:31So what happens when alpha-gal gets into the body?
0:25:31 > 0:25:35Well, let's imagine that this row of sweets here is your bloodstream.
0:25:35 > 0:25:38These are all of the red blood corpuscles.
0:25:38 > 0:25:41What scientists think is that when the tick bites you,
0:25:41 > 0:25:46it introduces a small amount of alpha-gal that's been left there
0:25:46 > 0:25:50from its last meal - maybe when it bit a deer, or something like that.
0:25:50 > 0:25:52Now, the body doesn't like this,
0:25:52 > 0:25:56so it produces proteins called antibodies
0:25:56 > 0:26:01and these attach themselves to the outside of any toxin or bacteria
0:26:01 > 0:26:03and render it harmless.
0:26:03 > 0:26:04Job done.
0:26:04 > 0:26:08But, of course, the body keeps a template of these antibodies,
0:26:08 > 0:26:12so that if the toxin appears again, it can react immediately.
0:26:12 > 0:26:16But then what happens is that you have a massive meal of meat
0:26:16 > 0:26:18and when it's digested,
0:26:18 > 0:26:22more of the alpha-gal is introduced into your bloodstream -
0:26:22 > 0:26:25this time, in much larger amounts.
0:26:25 > 0:26:27So the body reacts accordingly.
0:26:27 > 0:26:32It produces vast quantities of the antibodies
0:26:32 > 0:26:33and...
0:26:35 > 0:26:37..it swamps your bloodstream.
0:26:37 > 0:26:42And it's this which causes the massive allergic reaction.
0:26:44 > 0:26:47And the allergy is spreading.
0:26:47 > 0:26:52Cases have been reported all over the eastern and southeastern USA
0:26:52 > 0:26:53and across the world,
0:26:53 > 0:26:57there are reports of other tick-induced meat allergies.
0:26:59 > 0:27:01The ticks are on the march.
0:27:03 > 0:27:06But what does the future hold for those affected?
0:27:06 > 0:27:10Well, studies suggest that alpha-gal allergy recedes over time,
0:27:10 > 0:27:13as the antibody levels fall.
0:27:13 > 0:27:15So after a while,
0:27:15 > 0:27:18those with the condition can eventually eat meat again.
0:27:20 > 0:27:23As for Fred, he's still waiting for the all clear.
0:27:23 > 0:27:25And whilst he waits,
0:27:25 > 0:27:28he dreams of a return to some meaty morsels.
0:27:29 > 0:27:32Well, I'm looking forward to coming home
0:27:32 > 0:27:34and my wife saying she prepared my favourite meal.
0:27:34 > 0:27:37Having a nice steak on the grill. Having meatloaf and mashed potatoes,
0:27:37 > 0:27:39corn on the cob, a couple cheeseburgers.
0:27:39 > 0:27:41Any of the above, I would be thrilled with getting
0:27:41 > 0:27:44the OK from my doctor to sit down and have.
0:27:45 > 0:27:46So there we have it.
0:27:46 > 0:27:48It's almost unbelievable
0:27:48 > 0:27:50to think that a tiny tick
0:27:50 > 0:27:54can make a confirmed carnivore allergic to meat.
0:27:54 > 0:27:57It does prove you don't have to be big
0:27:57 > 0:27:58to have a big impact.
0:28:02 > 0:28:05And now, from one tiny terror in the USA
0:28:05 > 0:28:09to one other animal that punches above its weight
0:28:09 > 0:28:12on the grasslands of the UK.
0:28:15 > 0:28:19It involves this small, feisty animal -
0:28:19 > 0:28:21the stoat.
0:28:22 > 0:28:27The stoat is one of the UK's most secretive and elusive animals.
0:28:27 > 0:28:28But in some places,
0:28:28 > 0:28:33they're being spotted acting very strangely indeed.
0:28:35 > 0:28:39- There it is, there it is.- So fast!
0:28:39 > 0:28:43Adam Lee managed to film one of these peculiar incidents.
0:28:43 > 0:28:45I was out on a walk with my son,
0:28:45 > 0:28:48when I suddenly noticed a flash of white -
0:28:48 > 0:28:51the white underbelly of a stoat.
0:28:51 > 0:28:53It was doing lots and lots of different moves
0:28:53 > 0:28:55and lots and lots of rolls.
0:28:55 > 0:28:58I got my camera out as quickly as possible and videoed it,
0:28:58 > 0:29:00but we had no plausible explanation
0:29:00 > 0:29:04as to why the stoat would display this kind of mad behaviour
0:29:04 > 0:29:07in the middle of nowhere, in the middle of the day.
0:29:07 > 0:29:10Other footage shows similar behaviour -
0:29:10 > 0:29:13out in the open, oblivious to danger,
0:29:13 > 0:29:16stoats manically leaping and dancing,
0:29:16 > 0:29:18even attacking vegetation.
0:29:18 > 0:29:22It's almost as if they've gone completely mad.
0:29:24 > 0:29:28So why are Britain's stoats acting so bizarrely?
0:29:30 > 0:29:33Well, maybe there's a clue closer to home.
0:29:34 > 0:29:36Anyone who's owned a cat or a dog
0:29:36 > 0:29:40knows how crazy they go when they've got fleas.
0:29:40 > 0:29:43This behaviour looks similar and in fact,
0:29:43 > 0:29:46stoats are infested by something much worse than fleas.
0:29:48 > 0:29:50This is the skull of a stoat
0:29:50 > 0:29:52and if you look closely,
0:29:52 > 0:29:55you can see that it's pitted with tiny holes.
0:29:56 > 0:29:58The culprit is this -
0:29:58 > 0:30:02a parasitic worm, just 20mm long,
0:30:02 > 0:30:04that lives in the stoat's nasal cavity.
0:30:04 > 0:30:10Now, a heavy infestation causes this characteristic pitting...
0:30:10 > 0:30:15but can it also be blamed for stoats throwing shapes on the lawn?
0:30:16 > 0:30:20Well, weasels, polecats and other members of the same family
0:30:20 > 0:30:23also get infected with this parasite.
0:30:24 > 0:30:28But they have never been seen dancing like this.
0:30:28 > 0:30:33So if they're not being driven crackers by a head full of worms,
0:30:33 > 0:30:36could they be behaving like this on purpose?
0:30:38 > 0:30:39Despite their small size,
0:30:39 > 0:30:42stoats are efficient and deadly hunters...
0:30:45 > 0:30:49..and they'll kill anything they can get their paws on,
0:30:49 > 0:30:51but rabbits are top of their wish list.
0:30:53 > 0:30:55With adult rabbits weighing at least
0:30:55 > 0:30:58three times as much as these little predators,
0:30:58 > 0:31:02it's clear that they need another weapon in their hunting arsenal
0:31:02 > 0:31:05to guarantee success.
0:31:05 > 0:31:09And some people think that the stoat's dance is exactly that -
0:31:09 > 0:31:14not madness, but a carefully devised hunting strategy.
0:31:14 > 0:31:18The theory is that this dance is a form of hypnosis -
0:31:18 > 0:31:22the crazed moves send a rabbit into a trance,
0:31:22 > 0:31:24freezing on the spot,
0:31:24 > 0:31:26making it easier to catch.
0:31:29 > 0:31:32And as far-fetched as it seems,
0:31:32 > 0:31:36other predators also appear to use hypnosis to catch their prey.
0:31:40 > 0:31:44Cuttlefish send ripples of colour across their skin
0:31:44 > 0:31:46as they draw close to their prey,
0:31:46 > 0:31:49which scientists think might distract it
0:31:49 > 0:31:51in the last few seconds before a strike.
0:31:53 > 0:31:55But there is a problem with this theory.
0:31:55 > 0:31:59Rabbits do freeze when they see a stoat, or any predator.
0:31:59 > 0:32:01But a stoat's killing reaction
0:32:01 > 0:32:05is actually triggered by a moving rabbit.
0:32:05 > 0:32:08So making them stop simply wouldn't make sense.
0:32:09 > 0:32:11And that's not the only reason
0:32:11 > 0:32:15that we can cross hypnosis off the list of explanations.
0:32:15 > 0:32:17In most of the footage,
0:32:17 > 0:32:22the stoats don't seem to be performing to an audience at all.
0:32:22 > 0:32:26Well, there weren't any other rabbits in the vicinity,
0:32:26 > 0:32:27that we could see that day -
0:32:27 > 0:32:29in fact, there weren't any other animals.
0:32:29 > 0:32:32So with the stoats dancing like no-one's watching,
0:32:32 > 0:32:36the evidence suggests that they're making these mad moves
0:32:36 > 0:32:38purely for their own amusement.
0:32:38 > 0:32:42But no - everything in the natural world happens for a reason.
0:32:44 > 0:32:47What you're really seeing here isn't play -
0:32:47 > 0:32:50it's one half of a fight to the death.
0:32:51 > 0:32:54Just like a kung fu master practising his moves,
0:32:54 > 0:32:57the stoat is honing his attack skills,
0:32:57 > 0:32:59ready for the next hunt.
0:33:00 > 0:33:03After all, it could be a matter of survival.
0:33:05 > 0:33:09And of course, moments like this, captured on video,
0:33:09 > 0:33:11give us a unique opportunity
0:33:11 > 0:33:16to enjoy the stoat's delightful yet deadly dancing.
0:33:18 > 0:33:22And it's not just stoats that are doing things differently.
0:33:22 > 0:33:26Next up is a creature whose behaviour is so unexpected,
0:33:26 > 0:33:29it's verging on the suicidal.
0:33:31 > 0:33:35Now, I think that tarantulas like this are really rather beautiful,
0:33:35 > 0:33:39but of course, for many people, they're the stuff of nightmares.
0:33:39 > 0:33:41Nevertheless, we have to admit that they are
0:33:41 > 0:33:44one of nature's most respected and feared killers
0:33:44 > 0:33:46and their technique is simple.
0:33:46 > 0:33:49They remain stock still, just like this,
0:33:49 > 0:33:53camouflaging themselves to avoid the attention of any predators
0:33:53 > 0:33:56and so they can ambush their prey,
0:33:56 > 0:33:58which they then envenomate,
0:33:58 > 0:34:01using these massive fangs,
0:34:01 > 0:34:03or chelicerae, here.
0:34:03 > 0:34:06And you can see hers are quite literally
0:34:06 > 0:34:08dripping with venom.
0:34:09 > 0:34:13And that venom really does pack a punch.
0:34:13 > 0:34:15It easily overcomes any invertebrates
0:34:15 > 0:34:18and it's powerful enough to kill lizards,
0:34:18 > 0:34:21mice and even small birds.
0:34:21 > 0:34:23So we head to Texas,
0:34:23 > 0:34:26for an alarming encounter with these arachnids.
0:34:28 > 0:34:33In 2010, when a man filmed a wasp and a tarantula in his yard,
0:34:33 > 0:34:35the outcome seemed a forgone conclusion.
0:34:37 > 0:34:40Uh-oh, we might have a little war here.
0:34:40 > 0:34:42- Oh, that's crazy.- Yeah.
0:34:42 > 0:34:45That's the first time I've actually even seen this.
0:34:45 > 0:34:49But incredibly, this wasn't a one-off event.
0:34:49 > 0:34:52Others were seeing the same thing happen elsewhere.
0:34:52 > 0:34:54- That's amazing, he's...- Oh, sweet!
0:34:54 > 0:34:56- You're getting this, right? - Oh, yeah.
0:34:56 > 0:35:00- No way...- Yeah.- Sweet.- That is amazing.- You're kidding me?
0:35:02 > 0:35:05So what is this massive flying insect
0:35:05 > 0:35:08and why is it taking on a tarantula?
0:35:11 > 0:35:13It's a clash of the titans.
0:35:15 > 0:35:18One of the largest spiders in the world
0:35:18 > 0:35:21against one of the biggest wasps.
0:35:21 > 0:35:23In the midst of this frenzy,
0:35:23 > 0:35:25it's hard to tell who's the victim
0:35:25 > 0:35:27and who's the attacker.
0:35:28 > 0:35:32But surely, the sheer size
0:35:32 > 0:35:34and powerful venom of the tarantula
0:35:34 > 0:35:36will give it the upper hand?
0:35:36 > 0:35:38Well, actually, no -
0:35:38 > 0:35:41because this is not any wasp.
0:35:41 > 0:35:45This is the tarantula hawk wasp
0:35:45 > 0:35:51and it has one of the most painful stings of any insect in the world.
0:35:53 > 0:35:55Biologist Dr Justin Schmidt
0:35:55 > 0:36:00has felt the sharp end of a tarantula hawk wasp for himself.
0:36:00 > 0:36:04It just sends this electric shock just totally through your body,
0:36:04 > 0:36:07just paralyses you, you sit there and scream.
0:36:07 > 0:36:10You're just...just overwhelmed with pain.
0:36:10 > 0:36:12With such a powerful venom,
0:36:12 > 0:36:16the wasp is more than a match for the tarantula.
0:36:16 > 0:36:18But why would a flying insect
0:36:18 > 0:36:22risk putting itself in harm's way in the first place?
0:36:22 > 0:36:24Well, a closer look
0:36:24 > 0:36:27reveals that this isn't self-defence by the wasp -
0:36:27 > 0:36:30it's naked aggression.
0:36:30 > 0:36:33This wasp is looking for trouble.
0:36:33 > 0:36:35But why?
0:36:35 > 0:36:38Well, often, when small animals spot predators,
0:36:38 > 0:36:40such as birds of prey or foxes,
0:36:40 > 0:36:44they mob and harass them until they move away.
0:36:44 > 0:36:47So perhaps the wasp's nest or its young are nearby
0:36:47 > 0:36:51and it's desperately trying to keep the tarantula away?
0:36:52 > 0:36:55But then, the wasp isn't chasing off the spider.
0:37:00 > 0:37:02In a sinister twist,
0:37:02 > 0:37:05the predatory spider has become the prey.
0:37:07 > 0:37:10The spider appears to be lifeless,
0:37:10 > 0:37:13but in fact, it's just paralysed.
0:37:13 > 0:37:15The wasp is keeping it alive
0:37:15 > 0:37:17and storing the body.
0:37:19 > 0:37:23And she's not feeding herself, either.
0:37:23 > 0:37:28Tarantula hawk wasps are actually largely vegetarian.
0:37:28 > 0:37:31So if the wasp isn't going to eat the spider,
0:37:31 > 0:37:33why risk injury or worse
0:37:33 > 0:37:37to tackle a tarantula and then bury it alive?
0:37:37 > 0:37:41Well, she's tracking them down for her offspring.
0:37:41 > 0:37:44It's kind of curious - they're good moms.
0:37:44 > 0:37:47You know, rather than eating the dinner, you keep it for your young.
0:37:47 > 0:37:49Her babies eat tarantulas.
0:37:49 > 0:37:54That's right - young hawk wasps eat tarantulas.
0:37:54 > 0:37:58She doesn't kill it, she just paralyses it and puts it in a cell,
0:37:58 > 0:38:01where she makes a little burrow, lays an egg on it,
0:38:01 > 0:38:03seals it up and goes away - mother's job is done.
0:38:03 > 0:38:05She doesn't eat any of the tarantula.
0:38:05 > 0:38:07It's her baby that eats it.
0:38:07 > 0:38:11One baby to one tarantula, which explains why they're so big.
0:38:13 > 0:38:16The tarantula isn't a meal for mum,
0:38:16 > 0:38:19it's a living larder for her larvae.
0:38:19 > 0:38:22And over the next 10-14 days,
0:38:22 > 0:38:25they eat it alive.
0:38:25 > 0:38:27They choose the non-essential organs first,
0:38:27 > 0:38:32so they eat the blood, the muscles, the fat, the reproductive organs.
0:38:32 > 0:38:36Only then do they turn to the heart and the brain.
0:38:36 > 0:38:38And after pupating,
0:38:38 > 0:38:40they finally emerge as an adult.
0:38:41 > 0:38:45It's a pretty gruesome process for the tarantula,
0:38:45 > 0:38:48but of course, the wasp isn't being sadistic -
0:38:48 > 0:38:49she's a caring mother,
0:38:49 > 0:38:54making sure that her young have fresh food.
0:38:54 > 0:38:57And the wasp's supermum skills don't stop there -
0:38:57 > 0:39:02she can actually choose which offspring to lay in each spider.
0:39:02 > 0:39:04And so she does that by...
0:39:04 > 0:39:07A boy is unfertilised eggs.
0:39:07 > 0:39:10And if it gets fertilised, it becomes a female,
0:39:10 > 0:39:13so what she does is get a nice, big, juicy tarantula.
0:39:13 > 0:39:15Wow. We want to make a girl out of this,
0:39:15 > 0:39:18because she's got to be strong and tough,
0:39:18 > 0:39:20to overcome her tarantulas when she's an adult.
0:39:21 > 0:39:24While if it's a small tarantula,
0:39:24 > 0:39:26then she'll lay an egg that becomes a male.
0:39:26 > 0:39:29Because a male, all he has to do is fly around and find females.
0:39:29 > 0:39:33He doesn't have to fight with tarantulas - he can be a little runt.
0:39:33 > 0:39:38By matching the gender of her larvae to each tarantula that she tackles,
0:39:38 > 0:39:41the wasp makes the most of every spider she finds.
0:39:42 > 0:39:47This is one mother that you wouldn't mess with.
0:39:47 > 0:39:48She's not only caring,
0:39:48 > 0:39:51but clever, strategic and brave,
0:39:51 > 0:39:53putting her own life at risk
0:39:53 > 0:39:57to place her young inside a deadly predator.
0:40:02 > 0:40:06So whether it's ticks turning carnivores vegetarian,
0:40:06 > 0:40:08stoats rehearsing for a hunt
0:40:08 > 0:40:10or wasps turning the tables...
0:40:12 > 0:40:14..what these encounters show
0:40:14 > 0:40:18is that although natural behaviours may seem strange at first,
0:40:18 > 0:40:21there's always a method in the madness.
0:40:24 > 0:40:27Our final set of weird happenings
0:40:27 > 0:40:29sees nature taking over our lives.
0:40:31 > 0:40:34From an unstoppable tide of green slime in China...
0:40:36 > 0:40:40..to a deserted shopping mall with some unusual tenants.
0:40:40 > 0:40:42Oh, this is cool.
0:40:42 > 0:40:45But first, we head to Australia,
0:40:45 > 0:40:48where something big has emerged from the forest.
0:40:50 > 0:40:53The north eastern coast of Queensland.
0:40:53 > 0:40:56People come here for the relaxing lifestyle
0:40:56 > 0:40:59and a chance to live amongst the beautiful beaches
0:40:59 > 0:41:01and pristine rainforest.
0:41:01 > 0:41:03But lately,
0:41:03 > 0:41:07local gardens have become the scene of some very alarming encounters.
0:41:07 > 0:41:10It is the 16th of June 2012,
0:41:10 > 0:41:12it's just me and Jonah here.
0:41:13 > 0:41:15Oh, my goodness.
0:41:15 > 0:41:17No, you do not go out there.
0:41:19 > 0:41:21Even a simple car journey
0:41:21 > 0:41:24is more like living in a scene from Jurassic Park.
0:41:26 > 0:41:29SQUAWK
0:41:31 > 0:41:34Wait, let him come, let him come.
0:41:34 > 0:41:36SHE WHIMPERS
0:41:39 > 0:41:41It's big, it looks threatening
0:41:41 > 0:41:42and up close,
0:41:42 > 0:41:44it's even more startling.
0:41:52 > 0:41:56So what are these velociraptor-like visitors?
0:41:56 > 0:41:58And why are they turning up in town?
0:42:07 > 0:42:10Well, the creature is in fact a southern cassowary -
0:42:10 > 0:42:13a usually shy, rarely seen bird
0:42:13 > 0:42:16that roams these ancient rainforests.
0:42:16 > 0:42:18It's as tall as a man
0:42:18 > 0:42:20and along with emus and ostriches,
0:42:20 > 0:42:24it's the closest thing that we have to a living dinosaur.
0:42:24 > 0:42:27It's flamboyant coloured face and wattles
0:42:27 > 0:42:30act like a beacon in the forest gloom.
0:42:30 > 0:42:34It's a gloriously bizarre bird.
0:42:34 > 0:42:36But one rather frightening feature
0:42:36 > 0:42:38makes them stand out.
0:42:39 > 0:42:43This is an old skeleton of a cassowary.
0:42:43 > 0:42:46It's a bit battered, but it does give us the opportunity
0:42:46 > 0:42:48to take a closer look at that part of its anatomy
0:42:48 > 0:42:51that gives the bird its fearsome reputation -
0:42:51 > 0:42:53its foot.
0:42:53 > 0:42:55You can see it's got these three toes here,
0:42:55 > 0:42:58for gripping the rainforest floor as it's running along.
0:42:58 > 0:43:02But it's this interior toe here
0:43:02 > 0:43:04that makes it potentially so dangerous.
0:43:04 > 0:43:09You see, that claw can grow to 12cm in length.
0:43:09 > 0:43:12So a good kick from a cassowary
0:43:12 > 0:43:15could quite literally unzip a human.
0:43:15 > 0:43:19I'm not sure I'd want to play chicken or kung fu with a cassowary.
0:43:21 > 0:43:24Its kick has even been known to kill -
0:43:24 > 0:43:27and that ranks them as the most dangerous bird on earth.
0:43:31 > 0:43:33But what would provoke an attack?
0:43:37 > 0:43:40Cassowaries are fiercely territorial
0:43:40 > 0:43:42and defend their patch of forest from other birds.
0:43:44 > 0:43:47They're also caring parents
0:43:47 > 0:43:49and if they need to, they'll protect their chicks
0:43:49 > 0:43:52by striking out with their fighting feet.
0:43:54 > 0:43:57So no wonder people are a bit concerned
0:43:57 > 0:43:59when they find a bird armed with a flick knife
0:43:59 > 0:44:02next to their barbie.
0:44:02 > 0:44:05I'm standing in my house and there's a cassowary in my yard.
0:44:05 > 0:44:06Ooh, that's a bit freaky.
0:44:08 > 0:44:11Don't...don't go out there.
0:44:11 > 0:44:13But it's very curious.
0:44:13 > 0:44:15- Wow, isn't that amazing, Jonah?- Yeah.
0:44:17 > 0:44:18Extremely...
0:44:18 > 0:44:22Evidence like this suggests that these garden invaders
0:44:22 > 0:44:24are staking a new claim on suburbia.
0:44:24 > 0:44:27But there might be a clue to their takeover
0:44:27 > 0:44:31in a devastating event that happened in 2006.
0:44:33 > 0:44:38Cyclone Larry lashed the coast with devastating effect,
0:44:38 > 0:44:43wrecking property and destroying huge swaths of forest.
0:44:46 > 0:44:49In the coastal community of Mission Beach,
0:44:49 > 0:44:52suddenly cassowaries were everywhere.
0:44:52 > 0:44:56You see, the cassowaries had lost their forest homes -
0:44:56 > 0:44:59and with them, they'd lost their food source.
0:45:00 > 0:45:02Now, cassowaries eat fruit -
0:45:02 > 0:45:06and a lot of it, up to 5kg a day.
0:45:06 > 0:45:11And fruit is something that gardens in Mission Beach have in abundance.
0:45:13 > 0:45:16It's eating the Davidson plums.
0:45:16 > 0:45:17Hello there.
0:45:18 > 0:45:21With the cassowaries' reputation for confrontation
0:45:21 > 0:45:24and their new-found love of grow-your-own,
0:45:24 > 0:45:26there could be trouble ahead.
0:45:26 > 0:45:30But does this bird really merit its bad name?
0:45:31 > 0:45:35The truth is, that left alone and treated with respect,
0:45:35 > 0:45:37cassowaries are actually quite shy
0:45:37 > 0:45:40and not the angry birds we might think.
0:45:41 > 0:45:43But one thing can make them bold
0:45:43 > 0:45:45and even aggressive.
0:45:45 > 0:45:47Because studies have shown
0:45:47 > 0:45:52that feeding cassowaries changes their natural behaviour.
0:45:52 > 0:45:54SQUAWK
0:45:55 > 0:45:58This can make them habituated to people
0:45:58 > 0:46:00and associate us with food.
0:46:01 > 0:46:02And on top of this,
0:46:02 > 0:46:05the coastal towns of Queensland are ever expanding,
0:46:05 > 0:46:09fragmenting the cassowaries' natural habitat
0:46:09 > 0:46:12and bringing birds and people closer together.
0:46:12 > 0:46:15The consequences are potentially deadly.
0:46:15 > 0:46:17CAR HORN
0:46:22 > 0:46:27Luckily, some people have taken this oddball bird to their hearts.
0:46:27 > 0:46:30There are now plans to protect the cassowary.
0:46:30 > 0:46:31So, with luck,
0:46:31 > 0:46:35there may still be some life in the old bird yet.
0:46:39 > 0:46:42From terror in suburban Australia,
0:46:42 > 0:46:45we move on to an invader in the depths of a city.
0:46:46 > 0:46:50Bangkok - the bustling capital of Thailand,
0:46:50 > 0:46:52home to eight million people
0:46:52 > 0:46:55and a well-worn travel destination.
0:46:55 > 0:46:59In 2011, over 12 million tourists and backpackers
0:46:59 > 0:47:01passed through the city.
0:47:01 > 0:47:04And in the ever-popular Khaosan Road area,
0:47:04 > 0:47:08a rumour began to spread of a new, must-see wildlife attraction.
0:47:09 > 0:47:13But this was far away from Thailand's stunning seas
0:47:13 > 0:47:15and fauna-rich forests.
0:47:15 > 0:47:17This was right here,
0:47:17 > 0:47:19in the heart of the city.
0:47:20 > 0:47:21Oh, this is cool.
0:47:24 > 0:47:27Jesse Rockwell was a student living in Bangkok at the time
0:47:27 > 0:47:29and he overheard some locals
0:47:29 > 0:47:32discussing a derelict shopping mall.
0:47:32 > 0:47:34They were a bit mysterious about it -
0:47:34 > 0:47:36they didn't want to tell us exactly where it was.
0:47:36 > 0:47:38But it sounded quite interesting.
0:47:38 > 0:47:41Our level of Thai at that time wasn't outstanding,
0:47:41 > 0:47:44so we just heard "building" and "fish".
0:47:44 > 0:47:45We were thinking aquarium -
0:47:45 > 0:47:48we weren't sure exactly what they were talking about.
0:47:48 > 0:47:52But this was enough to pique the interest of Jesse and his friends.
0:47:52 > 0:47:55We decided to go hunting for it one day
0:47:55 > 0:47:58and we had about a square mile radius to work from,
0:47:58 > 0:48:02that we were pretty sure it was located in.
0:48:02 > 0:48:06And we spent the day walking in circles,
0:48:06 > 0:48:08in and out of small alleys
0:48:08 > 0:48:11and we finally came upon a big iron gate that said,
0:48:11 > 0:48:14"strictly no admittance" in big Thai letters.
0:48:16 > 0:48:19There was actually a policeman on his motorcycle parked outside,
0:48:19 > 0:48:23so we decided to wait about 30 minutes, until he puttered off
0:48:23 > 0:48:25and we opened the door
0:48:25 > 0:48:27and we were just amazed at what we found.
0:48:30 > 0:48:33Jesse, and many other tourists following in his footsteps,
0:48:33 > 0:48:36found thousands and thousands of fish,
0:48:36 > 0:48:39thriving in the ruins of this burned out shopping centre.
0:48:42 > 0:48:46Over a course of minutes, there were just more and more building up
0:48:46 > 0:48:47and they got more and more active
0:48:47 > 0:48:50and there was easily 5,000-6,000 fish, though.
0:48:54 > 0:48:56We decided to go outside and buy some food -
0:48:56 > 0:48:59some bread and some vegetables to feed them.
0:48:59 > 0:49:01Once we started throwing food in,
0:49:01 > 0:49:03it was just amazing how many fish there were.
0:49:03 > 0:49:05Thousands just came right up to us.
0:49:09 > 0:49:12There were more fish than actual water.
0:49:13 > 0:49:15So how did this urban lake form
0:49:15 > 0:49:18in the centre of a city in the first place?
0:49:18 > 0:49:21And how did all of these fish get into it?
0:49:23 > 0:49:26Well, the city of Bangkok was built on marshland
0:49:26 > 0:49:29and many of the buildings are slowly sinking.
0:49:30 > 0:49:34In some areas, the water table has risen so high
0:49:34 > 0:49:37that monsoon rains simply don't drain away.
0:49:39 > 0:49:43Roofless after a fire, the rain gradually accumulated,
0:49:43 > 0:49:46leaving this vast pond in the basement.
0:49:49 > 0:49:53But that still doesn't explain the presence of so many fish.
0:49:54 > 0:49:58Well, fish have been known to colonise new ponds very quickly -
0:49:58 > 0:50:00often birds introduce fish eggs on their feet,
0:50:00 > 0:50:03or drop their dinner by mistake.
0:50:03 > 0:50:07But in fact, there are few water birds in the centre of Bangkok
0:50:07 > 0:50:08and those that do exist
0:50:08 > 0:50:12are unlikely to enter a dilapidated shopping centre.
0:50:12 > 0:50:15So what happened to bring the fish in here?
0:50:17 > 0:50:20The water... It had been flooded for a number of years.
0:50:20 > 0:50:23So people were having quite a few problems with mosquitoes.
0:50:23 > 0:50:26In the general area, there's a lot of food vendors
0:50:26 > 0:50:28and outdoor vendors in the old town.
0:50:28 > 0:50:31And they were being really bothered by the mosquitoes,
0:50:31 > 0:50:34so it's been said that somebody started to introduce the fish
0:50:34 > 0:50:37to control the mosquito population.
0:50:38 > 0:50:41So that could explain how a few of these fish got here,
0:50:41 > 0:50:46but how are they thriving in such huge numbers in this murky water?
0:50:47 > 0:50:50The fish are mostly tilapia, carp and catfish
0:50:50 > 0:50:54and all of them will eat mosquito larvae.
0:50:54 > 0:50:57These species are all hardy and adaptable
0:50:57 > 0:51:01and they can survive in water which has very little oxygen.
0:51:01 > 0:51:02Catfish, for example,
0:51:02 > 0:51:05can even switch to breathing air if necessary,
0:51:05 > 0:51:07taking gulps at the surface
0:51:07 > 0:51:09and absorbing oxygen through their mouth.
0:51:11 > 0:51:13And as well as fewer mosquitoes,
0:51:13 > 0:51:16there's a second benefit for the local residents.
0:51:16 > 0:51:18It's pretty obvious - a new source of food,
0:51:18 > 0:51:20right on their doorstep.
0:51:23 > 0:51:27Catfish is probably the most popular eating fish in Thailand.
0:51:28 > 0:51:31I'm pretty convinced people were going in there
0:51:31 > 0:51:33and you know, getting dinner,
0:51:33 > 0:51:36because people fish in much dirtier water in Bangkok.
0:51:36 > 0:51:40And that's probably the easiest place to fish in the world,
0:51:40 > 0:51:42if I've ever seen it, you know?
0:51:42 > 0:51:43Despite appearances,
0:51:43 > 0:51:46these waters support a unique ecosystem -
0:51:46 > 0:51:51proving that life will take hold, even in the most unlikely places,
0:51:51 > 0:51:54if you give it half a chance.
0:51:54 > 0:51:57In the midst of a teeming metropolis,
0:51:57 > 0:51:58this unpromising building
0:51:58 > 0:52:02provides an oasis of tranquillity.
0:52:03 > 0:52:04Staying in Asia,
0:52:04 > 0:52:07we move from an unexpected oasis
0:52:07 > 0:52:09to the biggest party on Earth.
0:52:11 > 0:52:13May 2008.
0:52:13 > 0:52:16For 12 years, China had been preparing to host
0:52:16 > 0:52:20the largest sporting event the world had ever seen.
0:52:20 > 0:52:23Yes, the Olympics were rolling into town.
0:52:25 > 0:52:29And of course, the organisers had spent billions on the event.
0:52:29 > 0:52:33But there was one thing that no-one had planned for.
0:52:33 > 0:52:35On the coast,
0:52:35 > 0:52:37a headline-hitting invasion was under way.
0:52:41 > 0:52:43It's a state of the art water sports facility -
0:52:43 > 0:52:46everything you'd expect from a modern Olympic games -
0:52:46 > 0:52:48except for one big, green problem.
0:52:50 > 0:52:53Just six weeks before the start of the sailing events,
0:52:53 > 0:52:56a thick green blanket engulfed
0:52:56 > 0:53:01as much as 13,000 square kilometres of the Yellow Sea coast...
0:53:02 > 0:53:04..solidifying the water.
0:53:06 > 0:53:09What was this choking green blanket?
0:53:09 > 0:53:11And where on Earth had it come from?
0:53:14 > 0:53:16The culprit is an alga.
0:53:18 > 0:53:21We know many of them more commonly as seaweeds.
0:53:21 > 0:53:25And they're at the heart of many marine ecosystems.
0:53:26 > 0:53:28In favourable conditions,
0:53:28 > 0:53:30algal seaweeds like giant kelp
0:53:30 > 0:53:33reach incredible sizes,
0:53:33 > 0:53:35providing a home for hundreds of species.
0:53:37 > 0:53:40So what got so out of hand in China?
0:53:40 > 0:53:44Well, a valuable pillar of the ocean community
0:53:44 > 0:53:47had become a relentless coastal invader.
0:53:48 > 0:53:51But this wasn't an attempt to colonise the land,
0:53:51 > 0:53:54or some sort of weird mutation.
0:53:54 > 0:53:58It was actually a natural phenomenon -
0:53:58 > 0:54:00blooming.
0:54:00 > 0:54:04Professor Tim Nelson is an algal bloom expert.
0:54:04 > 0:54:05Algae bloom usually
0:54:05 > 0:54:08when there's the right combination of ideal conditions -
0:54:08 > 0:54:09so plenty of light,
0:54:09 > 0:54:12plenty of nutrients - nitrogen, phosphorus, iron -
0:54:12 > 0:54:14those kinds of things
0:54:14 > 0:54:16and ideally the perfect temperature,
0:54:16 > 0:54:19which is just a bit warmer than the average temperature for the year.
0:54:20 > 0:54:24But this was the biggest algal bloom
0:54:24 > 0:54:26the world had ever seen.
0:54:26 > 0:54:28So what was going on in the Yellow Sea
0:54:28 > 0:54:30to trigger this astonishing event?
0:54:32 > 0:54:35China, the world's fastest-growing economy,
0:54:35 > 0:54:39had seen a huge surge in farming and industry.
0:54:39 > 0:54:42Industrial pollution and raw sewage
0:54:42 > 0:54:45were flowing into the sea at record levels.
0:54:46 > 0:54:51The water was quite simply supercharged with nutrients.
0:54:52 > 0:54:55At any other time of year, that might not have mattered -
0:54:55 > 0:54:58but the Olympics took place at the height of summer.
0:54:58 > 0:55:01In China, you've got the ideal conditions,
0:55:01 > 0:55:05the perfect storm for algae growth and accumulation.
0:55:05 > 0:55:07Into this perfect storm
0:55:07 > 0:55:10drifted a free-floating seaweed -
0:55:10 > 0:55:14the aptly named Ulva prolifera.
0:55:14 > 0:55:16A patch the size of a football field
0:55:16 > 0:55:19could cover a county - a large county in England,
0:55:19 > 0:55:22a small state in the United States within a couple of months
0:55:22 > 0:55:24and within four months,
0:55:24 > 0:55:26could theoretically cover the world.
0:55:27 > 0:55:32Spurred on by a bonanza of nutrients, warmth and sunlight,
0:55:32 > 0:55:34an immense bloom grew rapidly out at sea.
0:55:37 > 0:55:40Scientists and officials were keen to find out
0:55:40 > 0:55:43where this super bloom had originated.
0:55:44 > 0:55:47The answer came from space.
0:55:48 > 0:55:50The bloom was so massive,
0:55:50 > 0:55:53it showed up on satellite images.
0:55:53 > 0:55:56Researchers tracked it back to its source,
0:55:56 > 0:55:59about 240km south,
0:55:59 > 0:56:02just off the coast of Jiangsu province.
0:56:02 > 0:56:04Satellite images also revealed
0:56:04 > 0:56:07vast new seaweed farms nearby,
0:56:07 > 0:56:11stretching 13km out into to the sea.
0:56:11 > 0:56:14A coincidence?
0:56:14 > 0:56:17These seaweed farms are growing this -
0:56:17 > 0:56:18it's called nori
0:56:18 > 0:56:23and it's a type of seaweed that's used in the manufacture of sushi.
0:56:23 > 0:56:26And given the increased global demand for this sushi,
0:56:26 > 0:56:29the farms have sprung up to cater for that.
0:56:29 > 0:56:32But Ulva prolifera also grows there -
0:56:32 > 0:56:33as a pest.
0:56:33 > 0:56:37So in springtime, the farmers go out and scrape it off of the rafts.
0:56:37 > 0:56:40It then drifts into the open ocean,
0:56:40 > 0:56:44where it meets conditions that are absolutely ideal
0:56:44 > 0:56:47for a bloom of Olympic proportions.
0:56:49 > 0:56:53The amazing scenes of 2008 were just the beginning.
0:56:53 > 0:56:56Huge green tides have washed ashore at Qingdao
0:56:56 > 0:56:59every summer since.
0:56:59 > 0:57:00As for the Olympics,
0:57:00 > 0:57:04the Chinese government drafted in 10,000 people
0:57:04 > 0:57:06to clear the beach by hand,
0:57:06 > 0:57:10removing an estimated million tonnes of algae.
0:57:11 > 0:57:14The Games were saved.
0:57:20 > 0:57:22And there we have it.
0:57:22 > 0:57:24From giant birds in your garden,
0:57:24 > 0:57:26fish swarming in a shopping mall
0:57:26 > 0:57:30or green slime taking over the Olympics,
0:57:30 > 0:57:35the resilience of life to survive and thrive in such weird ways
0:57:35 > 0:57:37is truly something to behold.
0:57:40 > 0:57:43What all of these amazing events tell us
0:57:43 > 0:57:47is that nature always has the capacity to surprise us.
0:57:47 > 0:57:49And whether it's bonkers behaviour
0:57:49 > 0:57:53or simply animals in the wrong place at the wrong time,
0:57:53 > 0:57:56the persistence of life impresses us too.
0:57:56 > 0:57:59But sometimes, when our paths collide,
0:57:59 > 0:58:02our reaction is confusion, shock -
0:58:02 > 0:58:05even to be a little scared.
0:58:05 > 0:58:07Only by looking closer
0:58:07 > 0:58:09can we fully comprehend
0:58:09 > 0:58:12who and what we share our planet with.
0:58:15 > 0:58:18Next time on Nature's Weirdest Events...
0:58:18 > 0:58:20Fish out of water...
0:58:23 > 0:58:25That knocked my hat off!
0:58:25 > 0:58:27..slugs get into a tangle...
0:58:27 > 0:58:29What is happening? Augh!
0:58:29 > 0:58:32It's so disturbing...
0:58:32 > 0:58:35..and yes, stampeding rabbits!
0:58:35 > 0:58:37HE LAUGHS
0:58:37 > 0:58:39That tickles!