0:00:10 > 0:00:15Let's face it, our world is downright weird...
0:00:15 > 0:00:16Argh!
0:00:17 > 0:00:20..crawling with creatures you've never heard of.
0:00:20 > 0:00:23I can't believe that's a living thing.
0:00:23 > 0:00:25Full of the unexpected...
0:00:27 > 0:00:31..like freak weather exploding out of the blue...
0:00:31 > 0:00:32I thought I was going to die.
0:00:32 > 0:00:34..monkeys with first-aid skills...
0:00:34 > 0:00:36I sent it to my family.
0:00:36 > 0:00:39I sent it to my friends, said, "Have you seen this?
0:00:39 > 0:00:41..and the unexplained.
0:00:41 > 0:00:46An unborn twin discovered inside a brain.
0:00:46 > 0:00:50There was multiple hair follicles, bone and teeth.
0:00:54 > 0:00:59We've scoured the globe to bring you the very weirdest stories.
0:00:59 > 0:01:01Argh!
0:01:01 > 0:01:03I could feel this intense pain,
0:01:03 > 0:01:07as if you were being stabbed by hundreds of syringes.
0:01:12 > 0:01:15In this series, we're going to examine the evidence,
0:01:15 > 0:01:19test the science, and unravel the mysteries.
0:01:19 > 0:01:24We're going to discover what in the weird world is going on.
0:01:37 > 0:01:39In this episode,
0:01:39 > 0:01:43we'll find the answers to some of the natural world's weirdest questions.
0:01:46 > 0:01:50What's causing these rocks to spontaneously explode?
0:01:51 > 0:01:55Why are bats' brains being removed in a cave in Hungary?
0:01:58 > 0:02:01What on earth are these strange green balls?
0:02:03 > 0:02:07And why are these cats wearing bibs?
0:02:12 > 0:02:17Deserts. Miles and miles of sand.
0:02:23 > 0:02:25But add in the power of a storm...
0:02:28 > 0:02:32..and the result is not exactly a marriage made in heaven.
0:02:35 > 0:02:37Phoenix, Arizona.
0:02:45 > 0:02:49Something strange is building out in the desert.
0:03:00 > 0:03:02Winds are strengthening.
0:03:10 > 0:03:14This is certainly not a nice day for a white wedding.
0:03:18 > 0:03:20ORGAN PLAYS "Here Comes The Bride"
0:03:23 > 0:03:26The day of the wedding itself was relatively calm.
0:03:26 > 0:03:30The weather itself was really great. It was bright and sunny.
0:03:32 > 0:03:33It was the big day
0:03:33 > 0:03:35for one happy couple.
0:03:36 > 0:03:39We came to the venue to get dressed, take pictures.
0:03:42 > 0:03:45Friends and family were still kind of arriving.
0:03:45 > 0:03:48Everything was going smoothly.
0:03:48 > 0:03:52It was a day they would never forget.
0:03:52 > 0:03:57Their dream wedding. Something they'd been planning for months.
0:03:57 > 0:04:00I'm standing at the altar looking for the future bride,
0:04:00 > 0:04:01future wife, coming in.
0:04:01 > 0:04:03That was an awesome sight to see.
0:04:07 > 0:04:10What could possibly go wrong?
0:04:10 > 0:04:13We're here this afternoon to share with Gustavo and Jennifer
0:04:13 > 0:04:15a most important moment in their lives.
0:04:15 > 0:04:19A good, solid ten minutes in, everything was going fine.
0:04:19 > 0:04:23And then, I remember looking at Jenny, and I remember looking up.
0:04:25 > 0:04:29My jaw dropped. My eyes got big.
0:04:29 > 0:04:31I look at Jenny, Jenny's looking at me with this scared face.
0:04:31 > 0:04:34I couldn't help it. I had to turn around to look.
0:04:34 > 0:04:35"What is he looking at?"
0:04:35 > 0:04:41What they saw was an immense wall of dust coming straight towards them.
0:04:41 > 0:04:44We just...pretty much just hold on tight!
0:04:46 > 0:04:49Hurtling towards them was an immense cloud of sand,
0:04:49 > 0:04:52a super-sized dust storm,
0:04:52 > 0:04:55a bizarre phenomenon with an even stranger name -
0:04:55 > 0:04:57haboob.
0:04:59 > 0:05:03Haboobs are amazing, because they're like this impending doom.
0:05:06 > 0:05:07It's just kind of this wall
0:05:07 > 0:05:09that is getting closer,
0:05:09 > 0:05:12like something apocalyptic, something incredible is happening
0:05:12 > 0:05:13and you're just standing there watching it
0:05:13 > 0:05:15and there's nothing you can do about it.
0:05:15 > 0:05:20Haboobs are a desert phenomenon, but they are no ordinary dust storm.
0:05:21 > 0:05:25It's this towering, churning wall of lifted sand and dust
0:05:25 > 0:05:27that sets them apart.
0:05:30 > 0:05:32But what starts them off?
0:05:32 > 0:05:34Haboobs are formed by thunderstorms.
0:05:38 > 0:05:41Out here, at least, when thunderstorms form,
0:05:41 > 0:05:43they just drop the rain straight out the bottom.
0:05:44 > 0:05:47Haboobs usually happen during the rainy season
0:05:47 > 0:05:50in Arizona between June and September,
0:05:50 > 0:05:53when thunderstorms can be particularly heavy.
0:05:54 > 0:05:58These thunderstorms create strong downdraughts of cold air,
0:05:58 > 0:06:01which hit the dry desert floor and spread out,
0:06:01 > 0:06:06kicking the dust up high into the air, creating an imposing wall.
0:06:08 > 0:06:10It's almost like a bomb exploded.
0:06:10 > 0:06:12The dust will start rolling away from the storm,
0:06:12 > 0:06:15and then, a lot of times, that air that's thrown out
0:06:15 > 0:06:18will actually kick up more storms above it
0:06:18 > 0:06:21and those storms will build up and they'll drop downdraughts as well.
0:06:21 > 0:06:24They kind of end up creating this huge wall of dust.
0:06:24 > 0:06:27So, pretty quickly, a few grains of sand
0:06:27 > 0:06:32can be whipped up into a swirling, spiralling wall of dust,
0:06:32 > 0:06:35sweeping across the desert floor,
0:06:35 > 0:06:37engulfing everything in its way.
0:06:40 > 0:06:43Haboobs can be massive.
0:06:43 > 0:06:46The biggest ones that I've seen have been a mile tall
0:06:46 > 0:06:50and 100 miles wide, and have winds packing around 60mph.
0:06:56 > 0:06:58Once the haboob hits,
0:06:58 > 0:07:02visibility can be reduced to near zero in a couple of minutes.
0:07:03 > 0:07:08Planes have to be grounded. There are huge pile-ups on the roads.
0:07:08 > 0:07:11'Let's look at the freeway. The freeway has backed up.
0:07:11 > 0:07:13'It looks like there's an accident over there right now.'
0:07:13 > 0:07:16The high winds tear down trees and pylons...
0:07:17 > 0:07:21..and the whipping dust gets everywhere.
0:07:21 > 0:07:23You don't usually get a lot of warning
0:07:23 > 0:07:24that a dust storm's coming in,
0:07:24 > 0:07:26so they can spring out of nowhere.
0:07:32 > 0:07:33Meanwhile, back at the wedding,
0:07:33 > 0:07:36things were beginning to take a turn for the weird,
0:07:36 > 0:07:40as the winds strengthened and the bridal party was blasted with sand.
0:07:41 > 0:07:45And as if there wasn't already enough dust blowing around,
0:07:45 > 0:07:49Jenny and Gus still had the sand ceremony to do.
0:07:49 > 0:07:52We each have a different colour sand and we pour it into a vase,
0:07:52 > 0:07:57so it creates kind of a swirl as you're pouring it into your vase,
0:07:57 > 0:08:00to symbolise the unity of both of us coming together as one.
0:08:00 > 0:08:02They represent all that you are and all that you will ever be
0:08:02 > 0:08:04as individuals.
0:08:04 > 0:08:08As we were pouring, we were getting pelted with sand left and right.
0:08:10 > 0:08:12My husband here is just, "Let's just stop this.
0:08:12 > 0:08:14"We don't need it. This is ridiculous right now."
0:08:14 > 0:08:17And of course, me being the bride and this is what I want,
0:08:17 > 0:08:21"We're going to continue to pour sand until we are done!"
0:08:23 > 0:08:24And so we got most of it in there,
0:08:24 > 0:08:27then, finally, even I had to concede we needed to stop.
0:08:27 > 0:08:29I'm going to make this quick, OK?
0:08:29 > 0:08:31We should just end it and just get out of here.
0:08:31 > 0:08:34I can't see them, I can't see us.
0:08:34 > 0:08:36Sure enough, the judge kind of skipped a lot of things
0:08:36 > 0:08:40and went to, "I pronounce you husband and wife," and we kissed.
0:08:43 > 0:08:46I present you, Mr and Mrs Gustavo Luna.
0:08:48 > 0:08:51You know, we look back at it now, and kind of laugh at it.
0:08:51 > 0:08:52- Cos it's nobody's fault.- Yeah.
0:08:52 > 0:08:55- Definitely nobody's fault. - We can't control the weather.
0:08:55 > 0:08:56CONGREGATION CHEERS
0:08:56 > 0:09:00Surely one of the weirdest weddings ever witnessed!
0:09:06 > 0:09:08I think it's safe to assume
0:09:08 > 0:09:11that no-one is going to forget that wedding in a hurry.
0:09:11 > 0:09:13But you know, in this weird, weird world,
0:09:13 > 0:09:18it's not just important events that we try to preserve for all eternity.
0:09:18 > 0:09:21No, some people have gone to extraordinary lengths
0:09:21 > 0:09:22to preserve themselves.
0:09:30 > 0:09:35A statue of a Buddha in a museum in Budapest.
0:09:35 > 0:09:38Surely nothing weird here?
0:09:39 > 0:09:43But in fact, this golden statue was hiding a secret.
0:09:44 > 0:09:47Whilst it was undergoing restoration,
0:09:47 > 0:09:50researchers spotted something peculiar...
0:09:53 > 0:09:57..and a CT scan revealed their discovery in full -
0:09:57 > 0:10:00an entire body, hidden inside.
0:10:02 > 0:10:06It had been covered with gold, to look like a Buddhist statue,
0:10:06 > 0:10:10suggesting that the body was most likely that of a Buddhist monk.
0:10:11 > 0:10:14But that wasn't the end of the story.
0:10:14 > 0:10:19It also appeared that before being placed inside the statue,
0:10:19 > 0:10:21the monk had been mummified.
0:10:21 > 0:10:25Mummification is the preservation of dead bodies,
0:10:25 > 0:10:29so that the...significant amount of the soft tissue is preserved.
0:10:33 > 0:10:35Normally, dead bodies decay quite rapidly,
0:10:35 > 0:10:38because of bacteria and enzymes,
0:10:38 > 0:10:42so mummification really involves processes that stop decay.
0:10:44 > 0:10:48We know a lot about mummies through Egyptian mummies, of course -
0:10:48 > 0:10:51the iconic mummies, if you like.
0:10:52 > 0:10:57Many Egyptian mummies were carefully prepared once the person had died.
0:10:57 > 0:10:59The internal organs were removed
0:10:59 > 0:11:02and the body would be treated with natron,
0:11:02 > 0:11:05a type of salt with fantastic drying properties.
0:11:05 > 0:11:09They were then wrapped in hundreds of metres of linen.
0:11:09 > 0:11:13It's the drying out that's key.
0:11:13 > 0:11:17The lack of water prevents bacteria and enzymes from working,
0:11:17 > 0:11:21and this prevents the body from decomposing.
0:11:25 > 0:11:28But in the case of the golden statue mummy,
0:11:28 > 0:11:32it seems that something astonishing could have been going on.
0:11:34 > 0:11:36When you find a mummy like this,
0:11:36 > 0:11:39with that strong Buddhist connection,
0:11:39 > 0:11:40it's actually quite likely
0:11:40 > 0:11:43that there was self-mummification involved in this.
0:11:46 > 0:11:48It might just be that, in this case,
0:11:48 > 0:11:54the monk actually started to mummify himself whilst he was still alive.
0:11:55 > 0:11:59Self-mummification took place in countries like Japan and China
0:11:59 > 0:12:02in areas where Buddhism was practised.
0:12:04 > 0:12:06It started in about the 12th,
0:12:06 > 0:12:09and carried on through to the early 20th century,
0:12:09 > 0:12:12and it was a gruesome undertaking.
0:12:13 > 0:12:16With this process of self-mummification,
0:12:16 > 0:12:19It would be a question of the priest deciding
0:12:19 > 0:12:22they wanted to go on this journey, if you like,
0:12:22 > 0:12:26and so start by restricting their diet significantly.
0:12:27 > 0:12:29By limiting their food and water,
0:12:29 > 0:12:31they were beginning to preserve themselves
0:12:31 > 0:12:34months, even years, before they actually died...
0:12:36 > 0:12:40..and, by surrounding themselves with candles as they meditated,
0:12:40 > 0:12:43their bodies would dry out even further.
0:12:44 > 0:12:48They might also drink the sap from certain plants to poison themselves
0:12:48 > 0:12:52and destroy the bacteria that would decay their body after death.
0:12:54 > 0:12:57And it all took place in a tiny room.
0:12:58 > 0:13:00They would be in these very confined spaces,
0:13:00 > 0:13:03and they would have a bell that they would ring periodically
0:13:03 > 0:13:06to let their colleague priest know that they were still alive.
0:13:08 > 0:13:12When the bell stopped ringing, the monk had died.
0:13:14 > 0:13:16It's thought that by self-mummifying,
0:13:16 > 0:13:20the monks were attempting to become semi-divine beings,
0:13:20 > 0:13:23choosing to live in an in-between world
0:13:23 > 0:13:26between earth and permanent Nirvana,
0:13:26 > 0:13:30to help others become fully enlightened
0:13:30 > 0:13:32and reach Nirvana themselves.
0:13:34 > 0:13:37I think what is interesting about the self-mummifying priests
0:13:37 > 0:13:41is that they clearly understood the materials and methods
0:13:41 > 0:13:44they were using would actually go some significant way
0:13:44 > 0:13:48to preserve them forever, effectively.
0:13:54 > 0:13:58What can I say? I suppose it demonstrates commitment,
0:13:58 > 0:14:01although that's an understatement of enormous magnitude -
0:14:01 > 0:14:07but, over time, people haven't just been keen to mummify themselves -
0:14:07 > 0:14:11the ancient Egyptians liked to preserve their animals, too.
0:14:13 > 0:14:15They were huge cat fans,
0:14:15 > 0:14:18and perhaps, if they were still alive today,
0:14:18 > 0:14:24they'd feel very much at home in the American city of Minneapolis.
0:14:29 > 0:14:32You see, this isn't a music festival...
0:14:32 > 0:14:34or a comedy gig.
0:14:37 > 0:14:43No, this is a gathering of people with only one thing on their minds.
0:14:43 > 0:14:46You look around and there are all these people who are coming together
0:14:46 > 0:14:50to do something unbelievably ridiculous.
0:14:50 > 0:14:55This is the Internet Cat Video Festival.
0:14:55 > 0:14:58Yeah, we're all going to get together and watch videos of cats,
0:14:58 > 0:15:00two-minute videos of cats going like this.
0:15:05 > 0:15:09I am excited to see old ones and new ones, and all sorts of cat videos.
0:15:12 > 0:15:16Every year, over 10,000 feline obsessives turn up to watch
0:15:16 > 0:15:19back-to-back internet cat videos.
0:15:19 > 0:15:23It was nice to know that I'm not the only weirdo
0:15:23 > 0:15:28who sits on the internet and watches animal videos
0:15:28 > 0:15:30to get their animal fix all day.
0:15:30 > 0:15:33Cats are undoubtedly big news online.
0:15:33 > 0:15:38Last year alone, nearly two million cat videos were posted on YouTube.
0:15:38 > 0:15:43And they received a staggering 25 billion views.
0:15:43 > 0:15:47But why? Why are cat videos so popular?
0:15:50 > 0:15:52Cats have become an internet sensation,
0:15:52 > 0:15:55and I think there is probably a couple of reasons for that.
0:15:58 > 0:16:01One is that they are very photogenic.
0:16:01 > 0:16:04They've got these lovely round furry faces,
0:16:04 > 0:16:06which everybody seems to find appealing.
0:16:06 > 0:16:08They're rather like baby faces,
0:16:08 > 0:16:10because they have the forehead like babies do,
0:16:10 > 0:16:13and again, that makes them very appealing to us.
0:16:13 > 0:16:15It makes us want to look after them.
0:16:15 > 0:16:18The second thing is that their faces are not very expressive,
0:16:18 > 0:16:20which you might think is a drawback, but it's not.
0:16:20 > 0:16:23When you take a photograph or make a film of a cat,
0:16:23 > 0:16:25you can kind of put any connotation, any caption,
0:16:25 > 0:16:28you want on it, and it's believable.
0:16:32 > 0:16:34What's surprising is that,
0:16:34 > 0:16:38whilst there are many more dog than cat owners in the UK,
0:16:38 > 0:16:42cat videos are four times more likely to go viral
0:16:42 > 0:16:45than those featuring our canine companions.
0:16:45 > 0:16:47I've watched a lot of cat videos.
0:16:47 > 0:16:48I think the favourite one of mine
0:16:48 > 0:16:51is the cat that tries to get into smaller and smaller boxes.
0:16:54 > 0:16:56That is a very typical piece of cat behaviour.
0:16:56 > 0:16:58Cats love going inside boxes,
0:16:58 > 0:17:00because they like the security of a confined space,
0:17:00 > 0:17:03particularly if they're feeling a little bit nervous.
0:17:03 > 0:17:06This is a cat that has taken that to total extremes.
0:17:06 > 0:17:10But, look, whether you're watching the videos in a field
0:17:10 > 0:17:14with thousands of likeminded cat addicts, or on your own,
0:17:14 > 0:17:19I can't help but feel it's a bit of a waste of time, isn't it?
0:17:22 > 0:17:24Well, no. Apparently it's not.
0:17:25 > 0:17:28At the Indiana University Media School,
0:17:28 > 0:17:32recent research has shown that watching cat videos
0:17:32 > 0:17:35seems to increase your sense of emotional well being.
0:17:35 > 0:17:37Ha!
0:17:37 > 0:17:39I think she's eating it!
0:17:39 > 0:17:42Viewers boost their energy and positive emotions,
0:17:42 > 0:17:45whilst also feeling less anxious,
0:17:45 > 0:17:48annoyed and sad.
0:17:50 > 0:17:54And even if you're watching cat videos instead of working,
0:17:54 > 0:17:59any guilt you might feel seems to be outweighed by the enjoyment...
0:18:01 > 0:18:05..and may even help you to take on tougher tasks afterwards.
0:18:06 > 0:18:10But, whilst cats today are some of the biggest stars of the internet,
0:18:10 > 0:18:14they're not the first felines to be filmed doing something funny.
0:18:17 > 0:18:22The first ever cat film was shot way back in 1894,
0:18:22 > 0:18:24at the very dawn of cinema,
0:18:24 > 0:18:27with two cats having a boxing match.
0:18:28 > 0:18:32The man behind it was none other than Thomas Edison.
0:18:37 > 0:18:39But behind the veneer of the cute,
0:18:39 > 0:18:42the box surfing, the dog barking,
0:18:42 > 0:18:46the millions of adoring fans, I have to tell you,
0:18:46 > 0:18:49there is a darker side to our feline friends.
0:18:51 > 0:18:54Some of them are crack killers.
0:18:56 > 0:19:02Recent estimates suggest that 275 million small animals and birds
0:19:02 > 0:19:06are killed in the UK every year by cats.
0:19:06 > 0:19:09Most people have a cat, they want it to be a pet,
0:19:09 > 0:19:12they want to have a personal relationship with it,
0:19:12 > 0:19:15and they don't want the gory little bit of mouse
0:19:15 > 0:19:18being deposited on the kitchen floor in the morning.
0:19:25 > 0:19:29In Oregon, one such cat owner really had had enough
0:19:29 > 0:19:32of getting these grisly little presents each day.
0:19:34 > 0:19:36My cats killed birds.
0:19:40 > 0:19:41I like wildlife,
0:19:41 > 0:19:43and I like the garden,
0:19:43 > 0:19:45and they were ruining the whole thing.
0:19:45 > 0:19:47I didn't know how to stop them.
0:19:47 > 0:19:51I kept them inside, and they really didn't like it.
0:19:51 > 0:19:56They had cat fights, they sprayed, I would come home from work
0:19:56 > 0:19:59and the place reeked of urine and the cats hated each other.
0:19:59 > 0:20:02It was just horrible, trying to keep them inside.
0:20:02 > 0:20:04To stop cats from catching birds,
0:20:04 > 0:20:09you can get collars complete with bells or sonic deterrents on them,
0:20:09 > 0:20:12but sometimes, these don't work.
0:20:13 > 0:20:17So, Sue had to think outside the box.
0:20:17 > 0:20:18Or not...
0:20:18 > 0:20:23I started to think about, if I could build a wall around the cat,
0:20:23 > 0:20:28and so I envisioned a cardboard box with a hole cut out.
0:20:28 > 0:20:31I think someone's already got that one covered, Sue.
0:20:31 > 0:20:35And then it was, "Well, maybe I could just put a piece of cardboard
0:20:35 > 0:20:36"in front of them."
0:20:36 > 0:20:41Sue started by tying a flap of old boot leather around their necks.
0:20:41 > 0:20:46Whether it would work or not, it was worth a try, you know?
0:20:46 > 0:20:50So I let her out, and she didn't catch a bird for a week.
0:20:50 > 0:20:53And her prototype soon turned into this.
0:20:55 > 0:20:59By interfering with the cat's timing and co-ordination,
0:20:59 > 0:21:04a study has shown that this bib could stop 80% of cats from killing...
0:21:07 > 0:21:09..but then, even if they do manage to catch something,
0:21:09 > 0:21:13at least they won't spill anything down their front.
0:21:16 > 0:21:18So, from the ultimate wedding crashers
0:21:18 > 0:21:20in the arid deserts of Arizona...
0:21:21 > 0:21:23Go, go, go!
0:21:23 > 0:21:26..to monks drying themselves out
0:21:26 > 0:21:28in the hope of achieving immortality...
0:21:29 > 0:21:34..thousands of feline fans watching adorable cats on the internet...
0:21:36 > 0:21:39..and killer cats wearing bibs -
0:21:39 > 0:21:42it really is a weird world out there.
0:21:58 > 0:22:02Our next journey takes us from some unexpected explosions
0:22:02 > 0:22:07via an albeit tortuous route to some insects in disguise.
0:22:07 > 0:22:10Let's head to the golden state of California.
0:22:14 > 0:22:17Twain Harte, on the edge of the Sierra Nevada,
0:22:17 > 0:22:22is a small holiday town popular with families.
0:22:22 > 0:22:24Twain Harte, in the summer,
0:22:24 > 0:22:27for us and our family is a getaway, where we go to relax.
0:22:27 > 0:22:30It's a place we can leave the city behind
0:22:30 > 0:22:31and just have some family time.
0:22:31 > 0:22:35It's crowded, the beach is full, there are kids screaming and running
0:22:35 > 0:22:39and people walking around and walking their dogs.
0:22:42 > 0:22:45But, on the weekend of Twain Harte's annual water carnival,
0:22:45 > 0:22:48something was about to happen
0:22:48 > 0:22:51that would completely shock this close-knit community.
0:22:56 > 0:23:00When I first heard it, I thought it was dynamite going off.
0:23:03 > 0:23:05If it had happened a day earlier,
0:23:05 > 0:23:08there would have been 350 people out on that rock.
0:23:10 > 0:23:13But there was one family on the rock that day.
0:23:14 > 0:23:18We decided to go down to the beach because the weather had turned.
0:23:18 > 0:23:23I was with my in-laws and my kids and my niece and nephew.
0:23:23 > 0:23:26So we were hiking along and decided to go across the dam,
0:23:26 > 0:23:28over to the rock.
0:23:29 > 0:23:32All of a sudden, it was like a bomb went off.
0:23:32 > 0:23:36From the local cafe, the commotion was caught on camera.
0:23:38 > 0:23:40HUGE CRASH
0:23:40 > 0:23:42PEOPLE SHOUT
0:23:45 > 0:23:49The entire rock started to shift and move,
0:23:49 > 0:23:52and I actually thought it was an earthquake.
0:23:52 > 0:23:54California is no stranger to earthquakes.
0:23:56 > 0:23:58They can be completely devastating,
0:23:58 > 0:24:02causing billions of dollars' worth of damage.
0:24:04 > 0:24:06The San Andreas Fault,
0:24:06 > 0:24:10part of a sliding boundary between two of the earth's tectonic plates,
0:24:10 > 0:24:13is responsible for much of this seismic activity.
0:24:14 > 0:24:18But, back on the rock, Steve was beginning to think
0:24:18 > 0:24:22that maybe earthquakes weren't to blame this time.
0:24:22 > 0:24:26As we started to realise that it really wasn't an earthquake,
0:24:26 > 0:24:29because being from the area we had felt earthquakes
0:24:29 > 0:24:31and it was very different...
0:24:33 > 0:24:36..a crack appeared from the back of the rock
0:24:36 > 0:24:38and it started moving towards us.
0:24:40 > 0:24:43Explosions were coming out of the crevice.
0:24:44 > 0:24:47It was terrifying for the kids and for us,
0:24:47 > 0:24:49because we really didn't know what was going on.
0:24:49 > 0:24:52We truly thought that this thing was going to blow.
0:24:58 > 0:25:01Over the next couple of weeks,
0:25:01 > 0:25:04more explosions occurred on the rock.
0:25:05 > 0:25:06Whoa!
0:25:11 > 0:25:14The whole area, including the dam, became unsafe.
0:25:17 > 0:25:20The lake had to be closed.
0:25:23 > 0:25:27Geologists were fascinated by these unusual explosions.
0:25:28 > 0:25:30Rocks are like people.
0:25:30 > 0:25:34They get stressed and they react to stresses in very different ways.
0:25:36 > 0:25:39Rocks can accommodate stress and deal with it,
0:25:39 > 0:25:44or, if the stress is strong enough, they break.
0:25:44 > 0:25:46The question at Twain Harte, really,
0:25:46 > 0:25:48is what actually caused the stress.
0:25:49 > 0:25:52Dr Eppes thinks there's not one simple explanation,
0:25:52 > 0:25:56but a possible combination of three elements.
0:25:58 > 0:26:00As well as being in an earthquake zone,
0:26:00 > 0:26:02at the time, California was suffering
0:26:02 > 0:26:05one of the most severe droughts on record.
0:26:06 > 0:26:08Due to the ongoing drought,
0:26:08 > 0:26:11The water table there has been lowering.
0:26:12 > 0:26:15This could be causing, or could have caused,
0:26:15 > 0:26:17another sort of stress to develop.
0:26:18 > 0:26:21The rock at Twain Harte is a granite dome.
0:26:23 > 0:26:26As the water table lowered during this drought,
0:26:26 > 0:26:30it lightened the load on the dome, allowing it to rise up.
0:26:32 > 0:26:36As the dome lifted, the edges were compressed by surrounding rock...
0:26:38 > 0:26:41..but there was one final stress to add into the mix.
0:26:45 > 0:26:48On the week leading up to August 3rd at Twain Harte,
0:26:48 > 0:26:52you had temperatures that were ten degrees above normal.
0:26:53 > 0:26:55And then, the day that the rock cracked
0:26:55 > 0:26:58was actually ten degrees below normal.
0:26:58 > 0:27:03Dr Eppes believes that the rock cracked on this exact day
0:27:03 > 0:27:06because of simple expansion and contraction
0:27:06 > 0:27:08under huge temperature swings.
0:27:08 > 0:27:11It was the straw that broke the camel's back.
0:27:14 > 0:27:18The pressure builds and the rock cracks open explosively
0:27:18 > 0:27:20to relieve that pressure.
0:27:22 > 0:27:27It's called exfoliation, where the outer layers of the rock split,
0:27:27 > 0:27:29like peeling the rings off an onion.
0:27:33 > 0:27:38But the damage, the chaos caused at Twain Harte by that exfoliation,
0:27:38 > 0:27:43was nothing compared to what happens if you add in much larger rocks,
0:27:43 > 0:27:45and the forces of gravity.
0:27:46 > 0:27:49Just up the road at Yosemite National Park,
0:27:49 > 0:27:51the effect can be breathtaking.
0:27:52 > 0:27:55These rocks may crack at any time, without warning.
0:27:57 > 0:27:59A rockfall, look!
0:28:02 > 0:28:03Look at that piece!
0:28:04 > 0:28:05They may look small,
0:28:05 > 0:28:09but in fact, some are bigger than a double-decker bus...
0:28:16 > 0:28:19..and, in an area with four million visitors a year,
0:28:19 > 0:28:23this is one weird force of nature that has to be reckoned with.
0:28:25 > 0:28:29But the danger of exploding rocks won't put some people off
0:28:29 > 0:28:31from returning to Twain Harte.
0:28:31 > 0:28:33We'll never stop coming back to Twain Harte.
0:28:33 > 0:28:35We're going there this weekend
0:28:35 > 0:28:37and hopefully we'll see the lake filling up
0:28:37 > 0:28:40and we'll get ready to get out on that rock.
0:28:42 > 0:28:44It's a dangerous world out there,
0:28:44 > 0:28:45there's no doubt about it,
0:28:45 > 0:28:49but sometimes the threats come from where you'd least expect it.
0:28:53 > 0:28:57I saw the shadow come up on my left-hand side and go past me.
0:28:59 > 0:29:03I just stopped dead in my tracks and I could feel this intense pain...
0:29:04 > 0:29:08..as if you were being stabbed by hundreds of syringes.
0:29:08 > 0:29:13The lower part of my ear felt like it was on fire.
0:29:13 > 0:29:16It was a pain that I had never felt before.
0:29:20 > 0:29:23Tom Hart Dyke is a plant hunter
0:29:23 > 0:29:25who's travelled all over the world
0:29:25 > 0:29:28in his search for the weird and wonderful.
0:29:31 > 0:29:35He's used to putting himself in some pretty testing situations...
0:29:37 > 0:29:39..and an expedition to the tropical rainforest
0:29:39 > 0:29:43of Queensland in Australia was no exception.
0:29:44 > 0:29:48The conditions on the expedition were pretty tough.
0:29:48 > 0:29:50I was on my own, seeing plants in the wild.
0:29:50 > 0:29:53On the forest floor, it is very dark.
0:29:53 > 0:29:55You can hardly see where you're walking
0:29:55 > 0:29:58and you're always pushing away foliage of various sorts.
0:29:59 > 0:30:02I just stopped dead in my tracks
0:30:02 > 0:30:03and I could just feel
0:30:03 > 0:30:06this extraordinary, intense throbbing pain.
0:30:08 > 0:30:14Now, Australia is renowned for its long list of dangerous wildlife.
0:30:14 > 0:30:17Where Tom was walking there were funnel-web spiders
0:30:17 > 0:30:21and brown tree snakes capable of inflicting a nasty wound
0:30:21 > 0:30:23on the unsuspecting.
0:30:25 > 0:30:29Initially, I assumed it was a massive hornet
0:30:29 > 0:30:31or some insect that had stung me.
0:30:33 > 0:30:38It was unbelievable, intense throbbing pain.
0:30:41 > 0:30:44Tom had stumbled across something he'd heard about
0:30:44 > 0:30:47but never actually experienced before.
0:30:48 > 0:30:51It was the gympie gympie plant,
0:30:51 > 0:30:55otherwise known as the deadly stinger.
0:30:55 > 0:30:59The deadly stinger is known as the world's most dangerous plans.
0:30:59 > 0:31:02It's a very unassuming plant that you wouldn't know, particularly,
0:31:02 > 0:31:03was that poisonous.
0:31:03 > 0:31:05When you look at it, it's not that interesting.
0:31:05 > 0:31:08The berries are quite nice, the leaves have quite nice shapes,
0:31:08 > 0:31:11but it's not a plant that certainly stands out.
0:31:13 > 0:31:19Gympie gympie means stinging tree or bush,
0:31:19 > 0:31:21and it belongs to the same family
0:31:21 > 0:31:24as the familiar stinging nettle in the UK.
0:31:26 > 0:31:28But, whilst nettles can hurt,
0:31:28 > 0:31:33it's nothing in comparison to the agony inflicted by the gympie gympie.
0:31:34 > 0:31:37The sting is extraordinary painful.
0:31:37 > 0:31:39Depending how much you get stung,
0:31:39 > 0:31:42it can cause your immune system to just shut down.
0:31:43 > 0:31:46When you're stung by the deadly stinger, you never forget it.
0:31:46 > 0:31:50Months after you've been stung, the pain can come back.
0:31:50 > 0:31:52There's no other plant in the world
0:31:52 > 0:31:56that causes as much re-occurring pain as the deadly stinger.
0:31:59 > 0:32:01Small red spots can appear
0:32:01 > 0:32:04and form a larger swollen area.
0:32:04 > 0:32:07Pain may spread to other parts of the body
0:32:07 > 0:32:10like the head, limbs or armpits,
0:32:10 > 0:32:13lasting for days.
0:32:13 > 0:32:16And the cause of all of this pain
0:32:16 > 0:32:21can be seen with a closer look at the surface of the leaves.
0:32:21 > 0:32:25They are covered in tiny silica-tipped hairs,
0:32:25 > 0:32:30as many as 15,000 on each side of a single leaf.
0:32:32 > 0:32:36Each hair is like a hollow hypodermic needle.
0:32:38 > 0:32:41As you just lightly brush past it,
0:32:41 > 0:32:45there's a round circular bubble at the apex of each particular hair
0:32:45 > 0:32:49that breaks off and this then penetrates into your skin
0:32:49 > 0:32:52releasing a concoction of acid.
0:32:52 > 0:32:54The top bit of the needle or the whole part
0:32:54 > 0:32:57can break off into the skin so it remains in there.
0:32:57 > 0:33:00That's what causes the reoccurring pain.
0:33:01 > 0:33:05I've heard stories of it recurring for up to two and a half years
0:33:05 > 0:33:07after the initial sting.
0:33:08 > 0:33:10But it gets worse.
0:33:14 > 0:33:18These plants have been known to kill dogs, kill horses,
0:33:18 > 0:33:21even lead to the deaths of humans.
0:33:21 > 0:33:24In World War II, an Australian serviceman was stung
0:33:24 > 0:33:26during his military training.
0:33:26 > 0:33:31He then spent the next three weeks tied to a hospital bed
0:33:31 > 0:33:34because the pain was so intense.
0:33:34 > 0:33:36There's a story, and it may be just a story,
0:33:36 > 0:33:41that an officer mistakenly used one of the leaves as toilet paper
0:33:41 > 0:33:45and then shot himself because he couldn't take the pain.
0:33:47 > 0:33:51The actual chemicals in the plant are not fully understood,
0:33:51 > 0:33:56but it seems like a cocktail of compounds are involved -
0:33:56 > 0:34:00and they're so stable that, even in dried specimens
0:34:00 > 0:34:02where the leaves are more than 100 years old,
0:34:02 > 0:34:06the hairs can still give a horrendous sting.
0:34:09 > 0:34:12But the gympie gympie is not invincible.
0:34:12 > 0:34:16Sometimes, the entire shrub is stripped overnight
0:34:16 > 0:34:19leaving just a chewed-up stem...
0:34:20 > 0:34:23..but which species could possibly eat a plant
0:34:23 > 0:34:26covered in such toxic spines?
0:34:32 > 0:34:38The hardy culprit was a shy, rather harmless-looking rainforest wallaby
0:34:38 > 0:34:40with an equally odd name -
0:34:40 > 0:34:44the red-legged pademelon.
0:34:44 > 0:34:49It usually lives alone, feeding on fallen leaves on the forest floor
0:34:49 > 0:34:52and berries and fruits from shrubs,
0:34:52 > 0:34:54but it can eat the gympie gympie as well,
0:34:54 > 0:34:59and seems simply to have adapted to deal with the sting over time...
0:35:00 > 0:35:02..and it's not the only one.
0:35:02 > 0:35:06A number of species, like this green ringtail possum,
0:35:06 > 0:35:07can eat the plant -
0:35:07 > 0:35:10but they're all native to Australia.
0:35:13 > 0:35:16And you might think that the excruciating pain
0:35:16 > 0:35:19Tom Hart Dyke suffered in the Queensland forest
0:35:19 > 0:35:24would mean he'd never want to see a gympie gympie again -
0:35:24 > 0:35:27but he's actually brought one of them back home
0:35:27 > 0:35:30where it has pride of place in his collection.
0:35:30 > 0:35:32But don't worry,
0:35:32 > 0:35:34it's highly doubtful that the gympie gympie
0:35:34 > 0:35:36would ever grow wild in the UK.
0:35:36 > 0:35:38It's a tropical plant,
0:35:38 > 0:35:42so it would be unlikely to survive outside of Tom's greenhouse.
0:35:48 > 0:35:52But you don't always need spines filled full of vicious toxins
0:35:52 > 0:35:55to deter predators. Oh, no.
0:35:55 > 0:35:58Some species have evolved far less deadly ways
0:35:58 > 0:36:01to avoid being on the menu.
0:36:04 > 0:36:07This is Papilio dardanus,
0:36:07 > 0:36:10the African mocker swallowtail -
0:36:10 > 0:36:12and, although it may not look like it,
0:36:12 > 0:36:17it's been described as the most interesting butterfly in the world.
0:36:17 > 0:36:22For 100 years, collectors only ever found males -
0:36:22 > 0:36:25which is clearly a bit weird -
0:36:25 > 0:36:27and, whilst these collectors were trying to work out
0:36:27 > 0:36:30why they only ever found male mocker swallowtails,
0:36:30 > 0:36:35they came across other strange butterfly conundrums.
0:36:35 > 0:36:39What was equally strange was that, for some of these species,
0:36:39 > 0:36:42they only ever found females.
0:36:42 > 0:36:43No males.
0:36:46 > 0:36:48It was a complete mystery.
0:36:48 > 0:36:50So what on earth was going on?
0:36:52 > 0:36:55Well, to get to the bottom of this mystery,
0:36:55 > 0:36:59scientists took some eggs from one of the female butterflies.
0:36:59 > 0:37:02When the scientists first bred out the butterflies
0:37:02 > 0:37:03from a batch of eggs,
0:37:03 > 0:37:05they assumed that there'd be
0:37:05 > 0:37:07just the one female type and one male type.
0:37:12 > 0:37:14In some species of butterfly,
0:37:14 > 0:37:17the males and females look very different.
0:37:18 > 0:37:21In others, they look pretty much the same.
0:37:23 > 0:37:27Either way, there's usually only one form of the male
0:37:27 > 0:37:30and one form of the female,
0:37:30 > 0:37:32but when the African mocker swallowtails
0:37:32 > 0:37:34emerged from their pupae,
0:37:34 > 0:37:38those scientists discovered something astonishing.
0:37:39 > 0:37:41They were surprised to find
0:37:41 > 0:37:44that there were several different-coloured female forms
0:37:44 > 0:37:46in the same batch.
0:37:46 > 0:37:49So, whilst the males all looked the same,
0:37:49 > 0:37:53the females were a whole range of colours and shapes.
0:37:55 > 0:37:59At last, the collectors had an answer to the mystery.
0:38:00 > 0:38:03All of these different-looking butterflies
0:38:03 > 0:38:06are actually the same species.
0:38:08 > 0:38:13So why did the females come in such a huge variety of colour and design?
0:38:16 > 0:38:20The answer lay in self-defence.
0:38:20 > 0:38:24Some species use camouflage to hide themselves from predators.
0:38:27 > 0:38:33Others taste toxic and are brightly coloured to let predators know that.
0:38:35 > 0:38:38If a young bird eats a distasteful butterfly,
0:38:38 > 0:38:42it learns very quickly that that butterfly is not nice
0:38:42 > 0:38:47and tends to avoid that colour of butterfly for the rest of its life.
0:38:47 > 0:38:50And the female African mocker swallowtail
0:38:50 > 0:38:52has an incredible twist on this tactic.
0:38:55 > 0:38:58The female mocker swallowtail has developed different colour forms
0:38:58 > 0:39:01to match these different poisonous butterflies
0:39:01 > 0:39:03so they don't get predated so much.
0:39:05 > 0:39:07Ingenious.
0:39:09 > 0:39:12It's an extraordinary adaptation.
0:39:12 > 0:39:15Up to a dozen or more different forms of the female
0:39:15 > 0:39:17have been discovered so far.
0:39:20 > 0:39:24Although the mocker swallowtail isn't poisonous,
0:39:24 > 0:39:27they've evolved to look like other species which are.
0:39:36 > 0:39:40OK, but there's one last thing that doesn't seem to make sense.
0:39:40 > 0:39:45I mean, how does a male African mocker swallowtail
0:39:45 > 0:39:48find a female African mocker swallowtail
0:39:48 > 0:39:52if those females look like a great range of other butterflies species?
0:39:56 > 0:39:59The males look for females of the same species -
0:39:59 > 0:40:00first by visual cues,
0:40:00 > 0:40:04but closer to, they use their antennae to sniff them out
0:40:04 > 0:40:06and they use pheromones to make sure it's the right
0:40:06 > 0:40:08species of female before they can mate with them.
0:40:08 > 0:40:13The males can sometimes mistake other butterflies for the female,
0:40:13 > 0:40:16but I've never seen one mate with the wrong species.
0:40:18 > 0:40:21So this mimicry is a brilliant solution
0:40:21 > 0:40:24to the problem of avoiding predators,
0:40:24 > 0:40:28and it's allowed the African Mocker Swallowtail
0:40:28 > 0:40:31to become extremely successful.
0:40:35 > 0:40:39So, exploding rocks in a sleepy holiday town gave tourists
0:40:39 > 0:40:41a nasty surprise...
0:40:43 > 0:40:45..whilst one unsuspecting traveller
0:40:45 > 0:40:49got a sharp shock from a plant with a spiky form of self-defence...
0:40:52 > 0:40:55..and there's an insect which protects itself
0:40:55 > 0:40:57with some incredible impersonations.
0:40:58 > 0:41:02All extraordinary goings-on in our strange world.
0:41:24 > 0:41:27Finally, we start with a monstrous headache
0:41:27 > 0:41:31and end up in a bizarre alien landscape full of green blobs.
0:41:33 > 0:41:38Yamini Karanam was born in Hyderabad in India in 1988.
0:41:39 > 0:41:41At the age of 25,
0:41:41 > 0:41:45she came to the University of Indiana to study for a PhD...
0:41:47 > 0:41:51..and that's when things started to turn a little bit strange.
0:41:54 > 0:41:55For more than six months,
0:41:55 > 0:41:58I just didn't know what it was like to not have a headache.
0:42:01 > 0:42:02I would wake up with a headache
0:42:02 > 0:42:05and I would have headaches through the day,
0:42:05 > 0:42:08and I would have headaches through the night.
0:42:08 > 0:42:09Yamini's life was on hold.
0:42:10 > 0:42:14She had to stop her studies for several months
0:42:14 > 0:42:18until her quest for medical advice led her to a leading surgeon
0:42:18 > 0:42:21at the Skull Base Institute in California.
0:42:25 > 0:42:27When Yamini first came to see me,
0:42:27 > 0:42:32her symptoms were - first, headaches, second, fatigue.
0:42:32 > 0:42:35I would sleep for more than 10-15 hours a day
0:42:35 > 0:42:38and still wake up very, very drowsy.
0:42:38 > 0:42:40What was more concerning to me
0:42:40 > 0:42:43were another set of symptoms that were cognitive symptoms.
0:42:43 > 0:42:45She's a 26-year-old PhD candidate,
0:42:45 > 0:42:48so she's a fairly intelligent human being,
0:42:48 > 0:42:52and she reported that she could not understand what she was reading.
0:42:52 > 0:42:58It went from "I'm not sure what I understand from this text"
0:42:58 > 0:43:01to, "Oh, my God! My head is in the clouds
0:43:01 > 0:43:03"after reading a couple of lines!"
0:43:03 > 0:43:05And that if she was in a room full of people,
0:43:05 > 0:43:08she could not comprehend the conversation.
0:43:11 > 0:43:16An MRI scan revealed a worrying lump right in the middle of her brain.
0:43:20 > 0:43:23My biggest fear was that this was a malignant,
0:43:23 > 0:43:26what we refer to as a cancerous, brain tumour.
0:43:28 > 0:43:31We had to do something because she was literally dying.
0:43:33 > 0:43:37Dr Shahinian specialises in pioneering keyhole surgery
0:43:37 > 0:43:39at the base of the skull.
0:43:40 > 0:43:44We can see this is the upper brain and this is the lower brain,
0:43:44 > 0:43:47and between the two, there is a natural space that you can see.
0:43:47 > 0:43:51So we access this space, the natural space,
0:43:51 > 0:43:54through a tiny opening here, a keyhole approach,
0:43:54 > 0:43:58and use an endoscope to go between the upper brain
0:43:58 > 0:44:01and the lower brain and access this tumour that way.
0:44:05 > 0:44:09But during the surgery, when he saw the exterior of the tumour,
0:44:09 > 0:44:12his worst fears appeared to be confirmed.
0:44:13 > 0:44:17The tumour surface was extremely gritty and hard,
0:44:17 > 0:44:19and normally that is a bad sign,
0:44:19 > 0:44:22because malignant tumours can be that way.
0:44:23 > 0:44:26But when he looked inside the tumour,
0:44:26 > 0:44:31what Dr Shahinian discovered left him truly astonished.
0:44:32 > 0:44:38There was multiple hair follicles, bone and teeth inside the tumour.
0:44:42 > 0:44:43It wasn't cancer -
0:44:43 > 0:44:48but what was this bony, hairy, toothy lump inside her head?
0:44:52 > 0:44:56It was a bizarre benign growth known as a teratoma.
0:45:00 > 0:45:03Teratoma comes from the Greek word "monstrous tumour"
0:45:03 > 0:45:06because, over the ages,
0:45:06 > 0:45:07we have known that these tumours
0:45:07 > 0:45:11can have all kinds of structures in them - sometimes hair,
0:45:11 > 0:45:15sometimes teeth, sometimes bone, sometimes eyes, sometimes limbs.
0:45:17 > 0:45:21And the teratoma had been with her much longer than she'd realised.
0:45:24 > 0:45:26They told me that I was born with it,
0:45:26 > 0:45:29and it's been growing for the past 26 years.
0:45:30 > 0:45:33So Yamini's teratoma had always been there,
0:45:33 > 0:45:37but it was only in recent times that it had created problems -
0:45:37 > 0:45:41but then, the causes of these teratomas in the first place
0:45:41 > 0:45:45is something that's been disputed and debated in medical circles for years.
0:45:51 > 0:45:53There are two competing theories.
0:45:53 > 0:45:57One theory is this is just an embryologic accident...
0:45:57 > 0:45:59When Yamini was in her mother's womb,
0:45:59 > 0:46:03it could have been that some rogue cells in her body
0:46:03 > 0:46:06started to grow in places they shouldn't...
0:46:07 > 0:46:11..but the alternative hypothesis behind teratomas
0:46:11 > 0:46:13is almost too bizarre to be believed.
0:46:15 > 0:46:19..and then the other theory is what we refer to as the foetus in foetu,
0:46:19 > 0:46:21which is the theory of the trapped twin.
0:46:23 > 0:46:27A foetus in foetu is when, during the very early stages of pregnancy,
0:46:27 > 0:46:30one twin doesn't develop normally
0:46:30 > 0:46:33and instead is absorbed into the body of the other.
0:46:35 > 0:46:37When they told me that it could have been my twin,
0:46:37 > 0:46:39I just called it my evil twin sister,
0:46:39 > 0:46:42because it's been putting me through so much trouble!
0:46:43 > 0:46:48About 12,000 sets of twins are born in the UK every year
0:46:48 > 0:46:53and some research has suggested that up to 12% of pregnancies
0:46:53 > 0:46:54may begin as twins,
0:46:54 > 0:46:58but then something changes and only one foetus develops.
0:46:59 > 0:47:04As for Yamini, although having undergone major brain surgery
0:47:04 > 0:47:08to remove what she describes as her evil twin,
0:47:08 > 0:47:10she's made a full recovery.
0:47:10 > 0:47:13All my symptoms have reversed,
0:47:13 > 0:47:16and so I just found this new joy in life.
0:47:19 > 0:47:23I suppose having your head invaded by a monster from within
0:47:23 > 0:47:25is a pretty unthinkable fate -
0:47:25 > 0:47:29but perhaps not nearly as bad as having your brains pecked out
0:47:29 > 0:47:31by an unlikely killer on the rampage.
0:47:34 > 0:47:36The Bukk Mountains in northern Hungary.
0:47:39 > 0:47:43Bats were discovered in a cave with their brains removed.
0:47:47 > 0:47:51Local naturalist Peter Estok had heard a grisly story
0:47:51 > 0:47:55that pointed to an unlikely culprit.
0:47:55 > 0:47:59I was very surprised, and I could not really believe that story.
0:48:05 > 0:48:09So, we came to the cave and see it for ourselves.
0:48:12 > 0:48:17It's usually birds of prey, like hawks and owls, which go for bats.
0:48:20 > 0:48:24But what Peter discovered went against all his expectations.
0:48:26 > 0:48:28I couldn't believe what I saw.
0:48:30 > 0:48:32Peter found a bird in the gloom...
0:48:35 > 0:48:38..but this was no bird of prey.
0:48:38 > 0:48:42Suddenly, a tit, a great tit, entered the cave,
0:48:42 > 0:48:46and it was looking for something near the crevices.
0:48:48 > 0:48:52Great tits? In caves? Surely they couldn't be to blame.
0:48:54 > 0:48:57We're more used to seeing them in our gardens.
0:48:57 > 0:49:01When they're not feeding on nuts and seeds at the bird table,
0:49:01 > 0:49:04the largest prey they are likely to dine out on
0:49:04 > 0:49:06are small insects and spiders...
0:49:09 > 0:49:13..but these great tits weren't searching for creepy crawlies.
0:49:15 > 0:49:18After some several minutes,
0:49:18 > 0:49:23we observed that the tit got a bat in its beak
0:49:23 > 0:49:27and it started to eat the bat.
0:49:30 > 0:49:34And this wasn't just an unfortunate one-off.
0:49:35 > 0:49:40We saw several occasions when great tits managed to get bats.
0:49:46 > 0:49:51When they were eating the bats, some of them were still alive.
0:49:54 > 0:49:57One of our favourite garden birds had gone bad.
0:49:58 > 0:50:01But what could turn a sweet little great tit
0:50:01 > 0:50:04into a vicious bat-hunting killer?
0:50:04 > 0:50:07Great tits aren't the only species
0:50:07 > 0:50:10to track down and eat things out of the ordinary.
0:50:11 > 0:50:16Over in the States, a couple caught this vegetarian on camera.
0:50:17 > 0:50:19It's got a bird.
0:50:19 > 0:50:20On the ground, Michael.
0:50:20 > 0:50:23Yeah, there's a bird on the ground. It's hurt.
0:50:23 > 0:50:27The culprit is a white tailed deer, munching on a chick.
0:50:27 > 0:50:29He's got it in his mouth.
0:50:29 > 0:50:31He's got the bird in his mouth.
0:50:34 > 0:50:36Oh, my goodness! He ate a bird!
0:50:36 > 0:50:39Michael, he ate a bird!
0:50:39 > 0:50:41He ate a bird!
0:50:41 > 0:50:43- Did you see that?- Yeah.
0:50:43 > 0:50:47It's not the kind of thing you see every day.
0:50:47 > 0:50:50Experts think it was either supplementing its diet
0:50:50 > 0:50:53with a quick protein-rich meal,
0:50:53 > 0:50:56or trying to get the calcium it needs to grow strong antlers.
0:50:58 > 0:51:03So, animals will find new sources of food when needs must.
0:51:04 > 0:51:06And with the great tits,
0:51:06 > 0:51:13Peter had a hunch what might be making them search for unusual prey.
0:51:13 > 0:51:14In hard winters,
0:51:14 > 0:51:18it is difficult for the great tits to find food outside,
0:51:18 > 0:51:22especially when the snow cover is significant.
0:51:24 > 0:51:26So the great tits were starving.
0:51:26 > 0:51:30As soon as Peter put out an alternative source of food,
0:51:30 > 0:51:33they stopped hunting the bats straightaway.
0:51:33 > 0:51:36They only did it in times of extreme hardship.
0:51:36 > 0:51:39This is not the first time that we've seen great tits
0:51:39 > 0:51:43finding a different source of food when things get tough.
0:51:46 > 0:51:49Back in the day, when milk was delivered to our doorsteps,
0:51:49 > 0:51:52great tits learned how to peck through the foil
0:51:52 > 0:51:55to get to the rich cream at the top.
0:51:55 > 0:51:57Something completely out of the ordinary,
0:51:57 > 0:51:59in terms of their usual diet.
0:51:59 > 0:52:03This behaviour was then passed from one bird to the next,
0:52:03 > 0:52:06simply by copying one another.
0:52:06 > 0:52:09And then, from one generation to the next,
0:52:09 > 0:52:12as the great tits turned out to be excellent social networkers.
0:52:18 > 0:52:21In the cave, the birds were seen to be attacking the bats over
0:52:21 > 0:52:26a period of ten years, yet great tits only live till they're about two.
0:52:28 > 0:52:31So, scientists think that the birds were passing the behaviour
0:52:31 > 0:52:37on by watching one another, just like the tits and the milk bottle tops,
0:52:39 > 0:52:41only a little bit more gruesome.
0:52:49 > 0:52:54Vampire great tits. Sounds like a cheap sci-fi movie, doesn't it?
0:52:54 > 0:52:58What could we add to the plot to improve it? Um...
0:52:58 > 0:53:02How about...some green balls?
0:53:05 > 0:53:07Australia in 2014.
0:53:10 > 0:53:13Sun, sea, sand, surf,
0:53:17 > 0:53:21and strange sightings on a beach in northern Sydney.
0:53:21 > 0:53:22The sands of Dee Why Beach
0:53:22 > 0:53:26were transformed into something of a Martian landscape today,
0:53:26 > 0:53:28covered in green alien balls.
0:53:31 > 0:53:33I'm not sure what they are.
0:53:33 > 0:53:36I haven't heard anyone who does know what they are, actually.
0:53:36 > 0:53:37They're crazy.
0:53:40 > 0:53:42They could be anything. They could be aliens.
0:53:43 > 0:53:48But could there really be an extraterrestrial connection?
0:53:48 > 0:53:50So, when these strange green furry balls
0:53:50 > 0:53:54washed up on the beach in Australia, lots of people were really confused.
0:53:58 > 0:54:01Bizarre as they may be,
0:54:01 > 0:54:04Mark thinks there's a surprisingly sensible explanation.
0:54:06 > 0:54:09These green balls are basically a type of algae.
0:54:12 > 0:54:17Algae are very simple plants, but they're really important
0:54:17 > 0:54:20and they use sunlight energy, like land plants,
0:54:20 > 0:54:23to photosynthesise to produce food.
0:54:23 > 0:54:26Algae usually grow on rocks or the sea floor,
0:54:26 > 0:54:30but they can grow just as happily drifting in the currents.
0:54:31 > 0:54:36But in this situation, they're doing something rather unusual.
0:54:36 > 0:54:38Each little tiny colony, bit by bit,
0:54:38 > 0:54:41is rolling around on the bottom of the sea
0:54:41 > 0:54:44and as sunlight energy hits the top of the ball,
0:54:44 > 0:54:48it grows a bit, and then it rotates and then it grows a bit -
0:54:48 > 0:54:50and that means the growth is kept even,
0:54:50 > 0:54:55and slowly getting bigger and bigger, as the seasons progress,
0:54:55 > 0:54:57until you get these wonderful green balls.
0:54:59 > 0:55:05But why did these balls suddenly turn up on just one beach in Australia?
0:55:07 > 0:55:11That mystery of their occurrence and then their disappearance
0:55:11 > 0:55:14is something we still don't really understand.
0:55:16 > 0:55:19Maybe in that one bay for a short period of time,
0:55:19 > 0:55:23local environmental conditions were just right
0:55:23 > 0:55:26for this rotation and growth to occur -
0:55:26 > 0:55:29and then maybe something happened.
0:55:29 > 0:55:33The currents shift, the water got colder, the nutrients changed,
0:55:33 > 0:55:35and the phenomenon stops,
0:55:35 > 0:55:38and this is one of the mysteries of these little organisms.
0:55:38 > 0:55:42It can occur in an individual water body, like a lake,
0:55:42 > 0:55:46for several years and then stop and never be known to occur again.
0:55:46 > 0:55:50So, what's seen as a strange anomaly down under...
0:55:50 > 0:55:54Well, take a trip to Japan and it's a different story altogether.
0:55:59 > 0:56:01Here, Lake Akan on the northern island
0:56:01 > 0:56:05has been home to these furry wonders for years.
0:56:12 > 0:56:16THEY SING
0:56:23 > 0:56:25They're so revered that every year,
0:56:25 > 0:56:30the indigenous Ainu people hold a three day festival in their honour.
0:56:33 > 0:56:35They're seen as something of a national treasure.
0:56:41 > 0:56:46The Japanese also keep them as very low-maintenance pets.
0:56:46 > 0:56:51I mean, you'll never need to go out in the rain to take these for a walk.
0:56:51 > 0:56:54And if you haven't got room for an aquarium,
0:56:54 > 0:56:56you could buy the cuddly toy instead.
0:56:58 > 0:57:00TOY LAUGHS
0:57:03 > 0:57:07So, the strange green balls on the beach in Australia
0:57:07 > 0:57:11were green algae rolled in to balls by the movement of water,
0:57:11 > 0:57:15and not unidentified floating objects, after all.
0:57:21 > 0:57:24So, a monstrous tumour caused a major headache
0:57:24 > 0:57:26for one student in America,
0:57:26 > 0:57:30whilst brain-hungry great tits spelled the end
0:57:30 > 0:57:32for some bats in a cave in Hungary...
0:57:35 > 0:57:37..and some strange green balls triggered
0:57:37 > 0:57:40a bit of a commotion on a beach in Australia.
0:57:43 > 0:57:45And if you think that's the end of it
0:57:45 > 0:57:47when it comes to weirdness in our world,
0:57:47 > 0:57:49we're only just getting started.
0:57:53 > 0:57:57Next time, we'll discover what causes a beach combing trip
0:57:57 > 0:58:00to end in disaster...
0:58:00 > 0:58:05As I looked down, there are flames shooting off of my shorts.
0:58:05 > 0:58:08..why a flower chooses to smell like a corpse...
0:58:08 > 0:58:11It's really doing a good job of pretending to be a dead animal.
0:58:11 > 0:58:15..what's causing three suns to miraculously appear in our skies...
0:58:20 > 0:58:23..and why a person with perfectly good eyesight can't even recognise
0:58:23 > 0:58:25her own children.
0:58:25 > 0:58:28It's funny that we have so many pictures of them,
0:58:28 > 0:58:29since I can't tell them apart.