0:00:02 > 0:00:05No matter how well we think we know our planet, the natural world still
0:00:05 > 0:00:07has the ability to surprise us,
0:00:07 > 0:00:09to shock us and maybe sometimes even
0:00:09 > 0:00:14to scare us with its extraordinary events and bizarre behaviour.
0:00:14 > 0:00:18And new technology means that nature's weirdest phenomena
0:00:18 > 0:00:21are being caught ever more readily on camera.
0:00:21 > 0:00:26So, we're going to bring you the strangest stories our world has to offer.
0:00:30 > 0:00:35From the biblical swarm that took Lake Erie by storm...
0:00:35 > 0:00:37That is really creepy.
0:00:37 > 0:00:40..and the bears with a taste for the poolside...
0:00:40 > 0:00:42There is a bear in my hot tub!
0:00:42 > 0:00:45With the help of scientists, experts and eyewitnesses,
0:00:45 > 0:00:50we're going to try and unravel exactly what on earth is going on.
0:01:11 > 0:01:14First we're heading to America's Great lakes where some
0:01:14 > 0:01:20very bizarre romantics are dying to find love, before it's too late.
0:01:21 > 0:01:26The shores of Lake Erie on America's beautiful border with Canada
0:01:26 > 0:01:31have always been a tranquil place of peace and quiet.
0:01:31 > 0:01:34Until, early in the summer of 2010,
0:01:34 > 0:01:39it became the setting for a swarm of phenomenal proportions.
0:01:39 > 0:01:45This gas station is being attacked by...something.
0:01:45 > 0:01:48And that lady won't even get out of her car.
0:01:48 > 0:01:49It's like it's snowing.
0:01:49 > 0:01:53A swarm of literally billions stretched over a mile inland
0:01:53 > 0:01:56and for miles along the western shore.
0:01:57 > 0:02:02Every surface, every inch of air was filled with winged insects.
0:02:02 > 0:02:05That is really creepy.
0:02:05 > 0:02:10Local resident Greg Stewart recalls the experience.
0:02:10 > 0:02:16They were all over the wall of the city and I didn't know if I should even
0:02:16 > 0:02:18get out of my car, it was that bad.
0:02:18 > 0:02:21And as I got out, they started crunching under my feet.
0:02:21 > 0:02:28Then, within days, they spontaneously started to die in their billions.
0:02:29 > 0:02:31Seriously, a pile of bugs.
0:02:36 > 0:02:40The drifts of dead bodies got so deep that the local authorities
0:02:40 > 0:02:44had to use snow ploughs to unblock the roads.
0:02:51 > 0:02:55And as they started to break down, they left another treat, too.
0:02:58 > 0:03:03It smelled of motor oil and vomit.
0:03:05 > 0:03:11So what were these insects, and what could have caused such an extraordinary plague?
0:03:18 > 0:03:22Don Schloesser is an expert in the wildlife of Lake Erie
0:03:22 > 0:03:28The big swarms are really the result of the life history pattern of the western Lake Erie mayflies.
0:03:30 > 0:03:34They live in the mud for about two years and they grow and they moult.
0:03:34 > 0:03:36About the middle of May, the first of June,
0:03:36 > 0:03:39they all come out of the water at one time.
0:03:39 > 0:03:43They mate, and then the females go back out into the water to lay the eggs.
0:03:43 > 0:03:47And then the whole process starts all over again.
0:03:47 > 0:03:50Mayfly spend about 99% of their lives
0:03:50 > 0:03:53as aquatic larvae at the bottom of ponds and rivers.
0:03:55 > 0:03:58They spend their time feeding and growing
0:03:58 > 0:04:01until, in a cunning plan to avoid getting eaten,
0:04:01 > 0:04:04they all emerge en masse to mate.
0:04:04 > 0:04:07The first few are easy pickings.
0:04:14 > 0:04:18But soon the sheer numbers overwhelm predators -
0:04:18 > 0:04:22they simply can't make a dent in the overall population.
0:04:33 > 0:04:36After about two days, there's a swarm,
0:04:36 > 0:04:41a swirling swarm like a little funnel cloud that's formed by the mayflies.
0:04:41 > 0:04:46And what happens is the females jump into that swarm, they are fertilized in the air.
0:04:48 > 0:04:53Once they have mated, the male dies and the female heads out
0:04:53 > 0:04:56over the water to release her fertilised eggs
0:04:56 > 0:04:59before she too passes away.
0:04:59 > 0:05:03The entire process takes just a matter of days.
0:05:06 > 0:05:10Each year as the event comes to an abrupt end,
0:05:10 > 0:05:13it's all hands on deck for the task of clearing up the dead.
0:05:13 > 0:05:18But there is still a lot of questions surrounding their mass emergence.
0:05:18 > 0:05:21When they come out is still a mystery to us.
0:05:21 > 0:05:24We can't predict very well in that two- or three-week period
0:05:24 > 0:05:27when they are actually going to be coming out.
0:05:27 > 0:05:29Sometimes it is related to storm events,
0:05:29 > 0:05:31sometimes it is related to rain events, but somehow
0:05:31 > 0:05:35the mayflies all get a cue when they are down in the bottom of the lake.
0:05:37 > 0:05:40But why are there so many in Lake Erie?
0:05:41 > 0:05:46Lake Erie supplies the types of sediment that this critter likes to burrow into.
0:05:46 > 0:05:50It used to have mayflies many years ago, then they went away for many years due to pollution.
0:05:50 > 0:05:53Now they're back and they've come back with sort of a vengeance
0:05:53 > 0:05:56in terms of the numbers and the abundances that we see come out of the water.
0:05:56 > 0:06:00So this almighty insect orgy is all down
0:06:00 > 0:06:04to a particularly perfect set of conditions.
0:06:04 > 0:06:09The enormous size of the lake and its newly clean waters contribute to
0:06:09 > 0:06:14a swarm so large that it can bring a whole city to a grinding halt.
0:06:17 > 0:06:21Even though you might be able to choose your lover,
0:06:21 > 0:06:25who you end up living next to is an entirely different matter.
0:06:25 > 0:06:30Coming up next, we look at some stories where neighbourly understanding is essential.
0:06:31 > 0:06:34We'll investigate the curious events that could lead you
0:06:34 > 0:06:36to sharing your favourite spot in the garden.
0:06:37 > 0:06:43But first, one incredible encounter that has led to a surprising
0:06:43 > 0:06:45and beautiful Platonic relationship.
0:06:47 > 0:06:52Churchill, on the shores of the Hudson Bay in the Canadian sub-arctic.
0:06:55 > 0:06:58Each year, starving polar bears roam around town
0:06:58 > 0:07:01waiting for the sea to freeze so they can hunt seals.
0:07:04 > 0:07:06Dog breeder and Churchill resident
0:07:06 > 0:07:10Brian Ladoon keeps 150 sled dogs on the shores of Hudson Bay.
0:07:14 > 0:07:18Just a complete city of dogs.
0:07:18 > 0:07:22Brian keeps his dogs on a spit of land jutting out into the sea.
0:07:25 > 0:07:32It's isolated and the best place to keep Eskimo dogs on earth.
0:07:32 > 0:07:37It's isolated and it's controllable, except for the other locals.
0:07:41 > 0:07:47You see, one day in 1992, Brian watched helplessly as a starving
0:07:47 > 0:07:49polar bear strolled onto his land
0:07:49 > 0:07:53and headed straight for his dogs.
0:07:53 > 0:07:55He knew all too well that bears
0:07:55 > 0:07:58regularly kill and eat dogs when they come into contact.
0:07:58 > 0:08:03When I first seen things playing out, I did have great concerns.
0:08:03 > 0:08:07I was frightened, and I wasn't sure what to do.
0:08:07 > 0:08:11He was unable to move a muscle as half a tonne of malnourished
0:08:11 > 0:08:16mega-predator closed in on his faithful companions.
0:08:16 > 0:08:20Then, as these photos show,
0:08:20 > 0:08:23something truly unbelievable happened.
0:08:25 > 0:08:27The pair began to play.
0:08:31 > 0:08:34It is extraordinary to see them play together.
0:08:34 > 0:08:35Actually you got a privileged position
0:08:35 > 0:08:38when you are right in the front row seat and you're watching them
0:08:38 > 0:08:41and they are only, like, metres away from you.
0:08:42 > 0:08:47Amazingly this particular bear started an annual ritual,
0:08:47 > 0:08:52returning to visit the dogs each year just before the sea freezes.
0:08:54 > 0:08:58So why on earth did this hungry polar bear feel that
0:08:58 > 0:09:00playing with its potential dinner
0:09:00 > 0:09:03was better than satisfying its aching hunger?
0:09:05 > 0:09:10Clinical psychiatrist Dr Stuart Brown has analysed these incredible photos.
0:09:11 > 0:09:13What was amazing to me
0:09:13 > 0:09:17was that the polar bear, as he approached this female sled dog
0:09:17 > 0:09:21that was tethered, was in a predatory gait,
0:09:21 > 0:09:24with fixed eyes, headed toward that sled dog.
0:09:24 > 0:09:28Which anyone who's ever seen a predatory animal
0:09:28 > 0:09:32recognises as a very powerful signal that says, "I'm going to kill you."
0:09:32 > 0:09:38The dog went down into a play bow, and the bear immediately
0:09:38 > 0:09:42picked this up, changed his gait and started dancing.
0:09:42 > 0:09:46And was gambolling. The hair went flat, the eyes went soft,
0:09:46 > 0:09:51and in a moment the bear was standing upright over the sled dog.
0:09:51 > 0:09:54The sled dog was staying there wagging her tail.
0:09:54 > 0:09:55They looked up at each other
0:09:55 > 0:09:59and they started into this wonderful ballet of rough-and-tumble play
0:09:59 > 0:10:02which went on for 20 minutes. It was magical.
0:10:04 > 0:10:07Dr Brown is a world authority on play,
0:10:07 > 0:10:12and has been studying its effects and benefits for over 20 years.
0:10:12 > 0:10:16The smarter the animal, the more they play.
0:10:16 > 0:10:17It's very important for survival
0:10:17 > 0:10:23and for adaptation in a constantly changing environment and world.
0:10:23 > 0:10:27Animals that are capable of play are also capable of innovation
0:10:27 > 0:10:30and flexibility under unexpected circumstances.
0:10:32 > 0:10:36Rough-and-tumble play, which is universal among social mammals,
0:10:36 > 0:10:40is extremely beneficial, complex and very, very important.
0:10:40 > 0:10:42What does it do?
0:10:42 > 0:10:46It teaches the animal their own strength, speed, capabilities.
0:10:46 > 0:10:49It puts them in competition with other animals,
0:10:49 > 0:10:53tells them where they fit in the hierarchy of the pack.
0:10:53 > 0:10:54It also teaches them empathy.
0:10:56 > 0:10:59So that makes sense for animals of the same species,
0:10:59 > 0:11:03but bears and dogs are competitors at best.
0:11:03 > 0:11:08At worst, Brian's dogs are a tasty snack-sized mouthful for a hungry bear.
0:11:09 > 0:11:12So there must be something more to it,
0:11:12 > 0:11:15but what need could be more urgent than hunger?
0:11:16 > 0:11:19I think the power of play signals is so intense
0:11:19 > 0:11:24and so important for survival, of both birds and mammals
0:11:24 > 0:11:29and human beings, that the signals that herald play are capable
0:11:29 > 0:11:33of being interpreted across species, which is quite remarkable.
0:11:33 > 0:11:38I've seen a magpie play with a bear.
0:11:38 > 0:11:41And they each were able to interpret the signals between each other
0:11:41 > 0:11:44that this was play, and they frolicked like crazy.
0:11:44 > 0:11:47Well, that's really quite significant, and when you look
0:11:47 > 0:11:52at that more deeply, you'll find that the survival drive that is a part
0:11:52 > 0:11:56of each of those animals' survival drive, is linked to play behaviour.
0:11:56 > 0:12:00So it seems that when the signals are strong enough,
0:12:00 > 0:12:04the urge to play can become irresistible.
0:12:04 > 0:12:08What's really incredible, though, is that this one exceptional bear
0:12:08 > 0:12:11started to bring its mates back with it.
0:12:12 > 0:12:15So what started out with just one rogue
0:12:15 > 0:12:20doing something out of the ordinary, is now an annual social event.
0:12:20 > 0:12:25Up to seven bears from the Churchill population have all
0:12:25 > 0:12:29built relationships with Brian's dogs.
0:12:29 > 0:12:33And over the years they have become local celebrities.
0:12:33 > 0:12:36First you think that the dogs are being attacked, and then you realise
0:12:36 > 0:12:40that, you know, he's holding his head in his mouth because he wants to.
0:12:40 > 0:12:43You'd think the bear would be right in there eating the dog
0:12:43 > 0:12:46straight away, but they have some kind of companionship going on,
0:12:46 > 0:12:48and it's amazing. It beautiful.
0:12:48 > 0:12:52They look like they are having a great time.
0:12:52 > 0:12:55They are happy to see their buddy, you know?
0:12:55 > 0:12:58DOG WHINES AND BARKS
0:13:01 > 0:13:05I think the dogs get sad when they see the bears go in the fall.
0:13:05 > 0:13:07They miss them.
0:13:07 > 0:13:11But, you know, come a certain day, the polar bears leave on the ice.
0:13:11 > 0:13:17Leaving the dogs hopeful that they will return next year to renew their friendship.
0:13:24 > 0:13:26BARKING AND GROWLING
0:13:31 > 0:13:35When you really take a close look at what's happening in something
0:13:35 > 0:13:39just as magical as a polar bear and a sled dog, you begin to get
0:13:39 > 0:13:43an understanding that there is something deeper going on here.
0:13:48 > 0:13:51Incredible stuff. But, you know, in we humans,
0:13:51 > 0:13:55play is far more important than learning how to survive in the wild.
0:13:55 > 0:13:58It's also about learning empathy
0:13:58 > 0:14:00and a great range of other social behaviours.
0:14:00 > 0:14:06So, for we humans at least, play isn't just practice for hunting and fighting.
0:14:09 > 0:14:13For our next story we look at some bizarre neighbourly
0:14:13 > 0:14:17relationships that go way past sharing the odd cup of sugar.
0:14:22 > 0:14:24The American black bear...
0:14:28 > 0:14:32Shy and retiring,
0:14:32 > 0:14:34they prefer their own company...
0:14:36 > 0:14:40..foraging for berries and grubs in their favourite habitats -
0:14:41 > 0:14:44the forests, marshes
0:14:44 > 0:14:47and rugged mountains across North America.
0:14:49 > 0:14:52They're brilliantly adapted to life in the wild.
0:14:55 > 0:15:01However, some US house owners have been witnessing some very peculiar behaviour.
0:15:05 > 0:15:07There's a bear in my hot tub!
0:15:09 > 0:15:10Please don't pee in there.
0:15:13 > 0:15:17Hey, get out of there! Get out of there!
0:15:17 > 0:15:20And it's not just the odd individual taking a dip
0:15:22 > 0:15:26Even fiercely protective mothers with cubs are getting in on the action.
0:15:27 > 0:15:31I got them swimming in my pool. They use the pool more than us.
0:15:31 > 0:15:34- Why didn't they go in Dr Bob's pool? - I don't know.
0:15:37 > 0:15:42But why would such a shy creature decide to party in a human's pool?
0:15:42 > 0:15:46You have to call the cops, Daddy. You have to.
0:15:46 > 0:15:50Bear expert Dr Ted Oakes believes that he might have an explanation.
0:15:52 > 0:15:55Black bears spend all winter in dens, which are often very,
0:15:55 > 0:15:58very cold places, and so they have thick, thick fur.
0:15:58 > 0:16:03But in the summer, because the fur is black, the fur absorbs heat
0:16:03 > 0:16:07almost like no other material, and they really, really heat up.
0:16:07 > 0:16:11I remember somebody I work with stuck a thermometer in the fur
0:16:11 > 0:16:14of a black bear in full sun, and it was just below boiling point.
0:16:14 > 0:16:19It was about 80 or 90 degrees Celsius.
0:16:19 > 0:16:23So, their first line of defence in the heat is to remove themselves from the sun.
0:16:23 > 0:16:27The second line of defence in the heat is to start panting.
0:16:27 > 0:16:31And black bears will pant when they are very, very hot.
0:16:31 > 0:16:34But when a black bear is panting,
0:16:34 > 0:16:37it's really in a situation where it's got to do something else
0:16:37 > 0:16:40to cool down, and that's usually seeking water.
0:16:44 > 0:16:48So, they take the plunge to cool off, but aren't black bears
0:16:48 > 0:16:52shy and elusive animals that stay away from humans?
0:16:54 > 0:16:58There are nearly a million black bears living in North America,
0:16:58 > 0:17:00and 300 million people.
0:17:00 > 0:17:03In fact, I would say now that most people are never more than
0:17:03 > 0:17:07a few miles from a black bear in most parts of North America.
0:17:07 > 0:17:11Black bears are rarely seen and the reason for that is they are quite shy.
0:17:11 > 0:17:17They don't want to be around people. They like to avoid people and usually people are trouble for them.
0:17:17 > 0:17:20But if there is not much food in the forest,
0:17:20 > 0:17:24they will take the opportunity to find food near human habitation.
0:17:24 > 0:17:26If it's a choice between starving to death and finding
0:17:26 > 0:17:29food from humans, bears can sometimes come to town.
0:17:31 > 0:17:35They might not actually come to a house to find water to cool down,
0:17:35 > 0:17:38they might actually come to a house to find a bird feeder.
0:17:38 > 0:17:41But once they are at the house and they see that the house not only has a bird feeder
0:17:41 > 0:17:45but a swimming pool, that's when the party could start for a black bear.
0:17:47 > 0:17:50Put that down! Quit tearing it up!
0:17:50 > 0:17:55But there is something even more amazing about these intriguing beasts.
0:17:55 > 0:17:58In some places where bears make trips into town,
0:17:58 > 0:18:01they make sure they do so on bin collection day,
0:18:01 > 0:18:04making their trips as fruitful as possible.
0:18:06 > 0:18:10Having a caring approach for our wild neighbours isn't something
0:18:10 > 0:18:13that's restricted to people living in far-flung places.
0:18:13 > 0:18:19Yes, they might have bears in hot tubs, but we have foxes on trampolines.
0:18:23 > 0:18:27There are about 250,000 adult red foxes in Britain...
0:18:29 > 0:18:32..and just like black bears they're intelligent,
0:18:32 > 0:18:34opportunistic mammals,
0:18:34 > 0:18:38happy to treat our property as their own.
0:18:38 > 0:18:43And occasionally use our gardens for a little play, too.
0:18:53 > 0:18:57What all these weird relationships show us is that as our population
0:18:57 > 0:19:02expands, it gets ever more important to treat those around us with a bit
0:19:02 > 0:19:04of humility, whoever they are.
0:19:05 > 0:19:09Even if it does mean some of us must accept that man
0:19:09 > 0:19:12might not always be a dog's best friend.
0:19:13 > 0:19:19In nature's weird world, it pays to have a good relationship with your neighbours.
0:19:21 > 0:19:26For nature's next weirdly one-sided union, we look at a hitchhiker
0:19:26 > 0:19:30that's desperate to dive deep into a long-term relationship.
0:19:33 > 0:19:38Back in 2009, climbing expert Tim Fogg arrived back in
0:19:38 > 0:19:42the UK from a trip to the Central African Republic.
0:19:42 > 0:19:47Nothing odd to report, until one day this happened.
0:19:49 > 0:19:54Suddenly my hand swelled up for no apparent reason.
0:19:54 > 0:19:58Then it went down, then about ten days later my arm swelled up
0:19:58 > 0:20:01and then it went down. Just bits of me kept swelling up.
0:20:05 > 0:20:09As a rope access specialist, Tim has travelled to
0:20:09 > 0:20:13some of the world's most bizarre and extreme environments,
0:20:13 > 0:20:18but never before had his body parts randomly swollen
0:20:18 > 0:20:19for no apparent reason.
0:20:21 > 0:20:25This bizarre bodily behaviour continued for two years.
0:20:28 > 0:20:31So what could be causing these spontaneous swellings?
0:20:34 > 0:20:38After several medical tests, Tim was diagnosed as having
0:20:38 > 0:20:42contracted Loa loa, or the African eye worm.
0:20:45 > 0:20:47It gets its gruesome name from
0:20:47 > 0:20:50the only time it becomes visible in infected humans -
0:20:50 > 0:20:55as it passes through its host's eyeballs.
0:20:58 > 0:21:01It's an incredible parasite that's carried by certain types
0:21:01 > 0:21:05of day biting flies in the swamps of west Africa,
0:21:05 > 0:21:10exactly where Tim had returned home from two years earlier.
0:21:10 > 0:21:13I think I got it wading through a load of mud in the forest where
0:21:13 > 0:21:17mango flies live, which is the thing that transmits it.
0:21:17 > 0:21:21Infection occurs when the larvae of the worm
0:21:21 > 0:21:23are passed to a human as the fly bites.
0:21:25 > 0:21:28The larvae then develop under the skin until they become adults
0:21:28 > 0:21:31and start their travels around the body.
0:21:33 > 0:21:38As they move about under the skin, the immune system starts to
0:21:38 > 0:21:41react and it's this that causes the swelling.
0:21:41 > 0:21:43I guess it was in my hand to start with,
0:21:43 > 0:21:46it presumably went up one arm then my other arm swelled up,
0:21:46 > 0:21:50so presumably somehow it got right across my shoulder and down into the other arm.
0:21:50 > 0:21:53Or maybe it was another worm. I have no idea.
0:21:54 > 0:21:59Incredibly, the worm can grow to be seven centimetres long and live
0:21:59 > 0:22:05for 17 years creeping around under the surface of the host's body.
0:22:05 > 0:22:09The worst thing about this thing wandering about under your skin
0:22:09 > 0:22:13is its habit of coming up to your eye
0:22:13 > 0:22:17and wandering across your eye and across the bridge of your nose and into the other eye.
0:22:17 > 0:22:20And that is apparently very, very painful.
0:22:20 > 0:22:24And I did have one incident where the side of my face swelled up
0:22:24 > 0:22:26which meant it was there, it was getting close
0:22:26 > 0:22:28and thinking about going across my eye.
0:22:28 > 0:22:29Luckily it changed its mind.
0:22:31 > 0:22:34The beauty of this parasite is that it doesn't hurt you at all,
0:22:34 > 0:22:36and it didn't make me feel ill.
0:22:36 > 0:22:39It was just the swelling so it's very clever.
0:22:39 > 0:22:41I mean, it just wants to feed off me,
0:22:41 > 0:22:46it doesn't want to give me bother if it can, cos I might get rid of it.
0:22:46 > 0:22:50After he was diagnosed in 2011, Tim's doctor put him
0:22:50 > 0:22:55on an intensive course of drugs, and a year later in June 2012
0:22:55 > 0:23:00he was deemed tentatively clear of his tenacious little body mate.
0:23:05 > 0:23:10Our last story is more body burrowing than bunny boiling,
0:23:10 > 0:23:15a gruesome but truly ingenious example of nature's
0:23:15 > 0:23:16weird relationships gone bad.
0:23:19 > 0:23:22And so to Panama where an innocent traveller has picked up
0:23:22 > 0:23:25a couple of unwanted passengers.
0:23:25 > 0:23:27Do you see it? Right there. SHRIEKING
0:23:27 > 0:23:33What started as two small insect bites has become swollen and angry.
0:23:33 > 0:23:37- SHRIEKING - It's ready to come out.- Yeah, it is.
0:23:37 > 0:23:40And there was something inside.
0:23:40 > 0:23:44Whatever they were simply had to be extracted.
0:23:44 > 0:23:48They are big. I can feel it trying to pull back in. Gross.
0:23:48 > 0:23:51- You mean it's still alive? - GASPS AND LAUGHTER
0:23:52 > 0:23:54That's huge!
0:24:00 > 0:24:02So, what on earth are they?
0:24:04 > 0:24:09Dr Mark Rowland works at the London School Of Hygiene and Tropical Medicine
0:24:09 > 0:24:12and has travelled the world studying parasites.
0:24:12 > 0:24:15Those insects that we are trying to pull out of people's bodies are
0:24:15 > 0:24:21the larvae of the botfly and I have some here, pickled inside this jar.
0:24:21 > 0:24:25They are quite large. They are about one and a half centimetres long.
0:24:25 > 0:24:30But how does something this big get under your skin in the first place?
0:24:30 > 0:24:32The botfly itself is quite large, it's about the size
0:24:32 > 0:24:36of a bumblebee, so if it were to actually land on a host itself
0:24:36 > 0:24:40it would probably be detected by the human or by the cattle or pig
0:24:40 > 0:24:42and be brushed away.
0:24:42 > 0:24:44That makes it less likely for the fly
0:24:44 > 0:24:48to succeed in laying its eggs successfully on the host.
0:24:48 > 0:24:52So the botfly has come up with a very sneaky tactic.
0:24:52 > 0:24:55What the fly has cleverly done is to grab,
0:24:55 > 0:25:00usually an insect like a mosquito or a tick or even a housefly.
0:25:00 > 0:25:04After a quick air ambush, the botfly pins down the fly
0:25:04 > 0:25:06and quickly attaches its eggs.
0:25:09 > 0:25:12And then off it goes to do the botfly's dirty work.
0:25:14 > 0:25:20On contacting the human, or animal host, the small botfly larvae inside the egg will be able
0:25:20 > 0:25:24to detect the warmth of the host, and it will hatch at that point.
0:25:24 > 0:25:26And it does this very quickly indeed.
0:25:26 > 0:25:29The larvae is able to penetrate and embed itself
0:25:29 > 0:25:32in the skin of the host.
0:25:32 > 0:25:35Over the course of several weeks, it will grow
0:25:35 > 0:25:38and eat its way into the flesh.
0:25:38 > 0:25:41And just in case you were thinking of getting rid of it at that stage,
0:25:41 > 0:25:44it has spiny bristles that hold it in
0:25:44 > 0:25:46and make it impossible to pull out.
0:25:48 > 0:25:50Oh, my God! Oh, God!
0:25:50 > 0:25:52That definitely is the trick, man, overnight.
0:25:52 > 0:25:56The only way to win this tug of war is to play dirty.
0:25:57 > 0:26:01One trick that you can do to make it easier is to
0:26:01 > 0:26:06smear a gel or fat over the rear end of the larvae.
0:26:06 > 0:26:09This will block the breathing tubes of the larvae.
0:26:09 > 0:26:13That makes it easier to actually draw the larvae from the body.
0:26:13 > 0:26:15GROANING
0:26:18 > 0:26:20SHOUTS AND GROANS
0:26:20 > 0:26:25Only when you've cut off its air supply will the botfly let go.
0:26:26 > 0:26:30Of course, the other option is to let nature take its course
0:26:30 > 0:26:33and wait six weeks for the larva to become a maggot,
0:26:33 > 0:26:38eat its way out and drop onto the ground before becoming an adult fly.
0:26:40 > 0:26:44It's a nasty business, however they exit.
0:26:44 > 0:26:49But after all of this, you should just end up with a little scar - no problem.
0:26:51 > 0:26:55Amazing that a maggot that size does so little damage in the end.
0:26:57 > 0:27:02From the worm that's just dying to get under your skin
0:27:02 > 0:27:05and the botfly who knows how to play tough,
0:27:05 > 0:27:10it's obvious that the further we travel the more likely we are
0:27:10 > 0:27:14to bring home the unwanted baggage of a holiday romance.
0:27:16 > 0:27:20What all of the stories in this programme seem to illustrate
0:27:20 > 0:27:25is that a bit of understanding and tolerance help in all of our relationships.
0:27:25 > 0:27:30So, if we can implement a bit of love and respect towards all of nature's wonders,
0:27:30 > 0:27:35there's absolutely no doubt that the world would be a richer place.
0:27:35 > 0:27:39And of course, the world is always getting smaller.
0:27:39 > 0:27:44So as we welcome more and more of these bizarre creatures into our own back-yards,
0:27:44 > 0:27:47what we think of as weird now
0:27:47 > 0:27:50might be a lot weirder in the future.
0:27:54 > 0:27:57Next time on Nature's Weirdest Events,
0:27:57 > 0:28:02there's an island awash under a tide of tiny crabs...
0:28:04 > 0:28:07..a town terrorized by rampaging elk,
0:28:07 > 0:28:12and a community primed for an unbelievable invasion of insects.