0:00:04 > 0:00:08There was a time when myths and science were entwined...
0:00:10 > 0:00:15..when mermaids and unicorns could mysteriously appear.
0:00:15 > 0:00:17Nature was weird.
0:00:19 > 0:00:23When science revealed the truth behind these imaginary creatures,
0:00:23 > 0:00:28it found real animals lay behind the legends.
0:00:29 > 0:00:34Today, science still makes astonishing discoveries,
0:00:34 > 0:00:37but nature seems just as weird.
0:00:37 > 0:00:42It's just that fact has broken free from fiction.
0:00:53 > 0:00:56GROWLING
0:01:01 > 0:01:05In nature, a good defence is key to survival.
0:01:06 > 0:01:10But humans have no natural defences at all.
0:01:12 > 0:01:17Even our most magical camouflage is no match for the real thing.
0:01:25 > 0:01:28Vine snakes freeze motionless for hours
0:01:28 > 0:01:31as they mimic the creepers that hide them.
0:01:39 > 0:01:41In turn, snakes are impersonated
0:01:41 > 0:01:44by the snakehead caterpillar.
0:01:52 > 0:01:57Insects become leaves, finessed with details of damage.
0:02:01 > 0:02:04A hunter's spotted coat conjures up dappled shade.
0:02:09 > 0:02:13But in the arms race between predator and prey,
0:02:13 > 0:02:17even the eyes of a killer are mimicked.
0:02:24 > 0:02:28These false faces, complete with eyes and nose,
0:02:28 > 0:02:30belong to eyespot frogs.
0:02:30 > 0:02:33They frighten real predators.
0:02:38 > 0:02:42Poison arrow frogs really are lethal.
0:02:42 > 0:02:45So rather than hide, they use vivid colours
0:02:45 > 0:02:48to warn against being eaten by mistake.
0:02:49 > 0:02:53Their toxic secretions lace tribal darts.
0:02:53 > 0:02:58The poison from just one frog can kill a man.
0:03:02 > 0:03:07Weird Nature uses imaginary settings to showcase real animal behaviour.
0:03:14 > 0:03:16This weird journey reveals
0:03:16 > 0:03:20the strange ways animals protect themselves.
0:03:38 > 0:03:43Full body armour is often the first line of defence.
0:03:44 > 0:03:49The three-banded armadillos of Argentina are the masters.
0:03:49 > 0:03:51Like medieval knights,
0:03:51 > 0:03:53they use articulated armour.
0:03:53 > 0:03:58Their protective shields, made from a double layer of horn and bone,
0:03:58 > 0:04:01are hinged with leathery skin.
0:04:01 > 0:04:05The plates cope with most of what nature throws at them,
0:04:05 > 0:04:08but a polo match is exceptional.
0:04:15 > 0:04:20This imaginary scene showcases the armadillo's extraordinary behaviour.
0:04:30 > 0:04:35Its first defence is to run, but heavy armour slows it down.
0:04:36 > 0:04:39Its second defence is to roll up,
0:04:39 > 0:04:44interlocking its plates into a sealed ball...
0:04:48 > 0:04:51..the strongest shape in nature.
0:04:59 > 0:05:04It can open just a chink to check what's happening.
0:05:13 > 0:05:16Even WE ball up for protection.
0:05:17 > 0:05:22But helmets and padding can't compete with full body armour.
0:05:23 > 0:05:28The only soft part of the armadillo is its face and underbelly.
0:05:29 > 0:05:34Otherwise, it's a walking armoured tank.
0:05:34 > 0:05:39It takes the knocks of real life just as easily in its stride.
0:06:02 > 0:06:07This fantasy wreck displays the inventive defences of sea creatures.
0:06:11 > 0:06:16The puffer fish has its own version of armour.
0:06:20 > 0:06:23Instead of scales,
0:06:23 > 0:06:26its leathery skin is armed with spines.
0:06:29 > 0:06:33The spines erect to form a lethal pincushion
0:06:33 > 0:06:36when the fish sucks in water.
0:06:41 > 0:06:46With elasticated skin and no ribs to stop its body expanding,
0:06:46 > 0:06:51it balloons to five times its normal size -
0:06:51 > 0:06:54too big for most mouths to swallow.
0:06:54 > 0:06:58The puffer's ultimate weapon is poison -
0:06:58 > 0:07:01enough to kill 30 people.
0:07:01 > 0:07:04There is no known antidote.
0:07:14 > 0:07:18This wreck also shows how animal defences can adapt
0:07:18 > 0:07:21to extraordinary circumstances.
0:07:25 > 0:07:30For dresser crabs, the right dress code is everything.
0:07:30 > 0:07:34They decorate their shells to fit in
0:07:34 > 0:07:37wherever they go.
0:07:37 > 0:07:41They select material from whatever is around.
0:07:41 > 0:07:45A dressing room full of treasure is paradise.
0:07:45 > 0:07:50They first chew their finds to make them frayed and fibrous.
0:07:50 > 0:07:56They then attach the prepared fabrics to Velcro-like hooks
0:07:56 > 0:07:59on their legs and shell.
0:08:00 > 0:08:04The dresser crab uses its keen attention to detail
0:08:04 > 0:08:07to fashion a camouflaged suit.
0:08:14 > 0:08:19It usually adorns its costume with sponges and seaweed,
0:08:19 > 0:08:21as these are most often to hand.
0:08:23 > 0:08:26But given the chance, it improvises,
0:08:26 > 0:08:32a trait that helps the dresser crab maintain perfect camouflage.
0:08:51 > 0:08:55Their eclectic dress sense means they blend in anywhere,
0:08:55 > 0:09:00safe from they eyes of predators like puffer fish.
0:09:07 > 0:09:10To vanish, they freeze.
0:09:27 > 0:09:31Making yourself bigger is not only a defence -
0:09:31 > 0:09:33it can also send a message.
0:09:38 > 0:09:44The spotted skunk is famed for its offensive body odour.
0:09:49 > 0:09:52TECHNO MUSIC
0:09:52 > 0:09:57Bold markings warn that it carries a concealed weapon.
0:10:10 > 0:10:15If the skunk isn't shown respect, it ups the ante.
0:10:20 > 0:10:26Handstanding exaggerates its size and shows off its markings.
0:10:31 > 0:10:33It's a dance of defiance.
0:10:36 > 0:10:40Foot-stomping drives home the threat.
0:10:45 > 0:10:49If the message is missed, the skunk reveals its weapon.
0:10:52 > 0:10:57Like an aerosol, anal glands spray sulphurous chemicals
0:10:57 > 0:11:00through nozzles aimed at the eyes.
0:11:00 > 0:11:04They cause temporary blindness and nausea.
0:11:16 > 0:11:19Some defensive sprays are even deadlier.
0:11:30 > 0:11:32Most give cobras
0:11:32 > 0:11:34a wide berth.
0:11:35 > 0:11:40But they say curiosity killed the cat.
0:11:50 > 0:11:54Snakes prefer to conserve their venom.
0:12:02 > 0:12:05So it spreads its hood as a warning.
0:12:11 > 0:12:14The spitting cobra aims for the eyes.
0:12:18 > 0:12:22Glands squeeze venom through hypodermic fangs.
0:12:27 > 0:12:30The spray jets 3m.
0:12:31 > 0:12:36A direct hit could have blinded for life.
0:12:39 > 0:12:42Most animals fear snakes.
0:12:42 > 0:12:47The horned frog of Central America is no exception.
0:12:51 > 0:12:55A lookalike snake provokes the same bizarre reaction.
0:12:55 > 0:12:58LOUD SCREECH
0:13:06 > 0:13:11If puffing up and screaming like a banshee fails, it fights back.
0:13:19 > 0:13:24It pays to have a wide repertoire. Danger is never far away.
0:13:29 > 0:13:33A horned owl would soon make a meal of a frog,
0:13:33 > 0:13:35even one with an inflated ego.
0:14:01 > 0:14:06But owls are equally fooled by a snake in the grass.
0:14:09 > 0:14:12They click their beaks and hiss and arch their wings
0:14:12 > 0:14:14to puff themselves up.
0:14:17 > 0:14:20If this bluff fails, they turn tail.
0:14:40 > 0:14:44Changing shape has been perfected by many sea creatures.
0:15:05 > 0:15:11The octopus's soft, malleable body helps it change shape easily,
0:15:11 > 0:15:16but the price of having no skeleton is vulnerability.
0:15:19 > 0:15:24One defence is to change texture to mimic its surroundings.
0:15:28 > 0:15:30Another is reactive camouflage.
0:15:32 > 0:15:37Its near-instantaneous colour change is under nervous control.
0:15:37 > 0:15:41Pigment cells expand and contract
0:15:41 > 0:15:43in waves of emotion.
0:15:48 > 0:15:54The colour cells react quicker than those of any other animal.
0:15:59 > 0:16:04But this quick-change artist has a rival.
0:16:17 > 0:16:19The peacock flounder's skin
0:16:19 > 0:16:23can make a near perfect facsimile of its surroundings.
0:16:33 > 0:16:38A paper-thin profile helps its vanishing trick.
0:16:43 > 0:16:47But how does it fare on a less familiar background?
0:16:51 > 0:16:55Its stalked eyes have feature detectors,
0:16:55 > 0:16:59primed to pick out patterns. It does a quick survey
0:16:59 > 0:17:02and then it makes a match.
0:17:10 > 0:17:13The eyes pass data to the brain
0:17:13 > 0:17:17which adjusts the size and contrast of pigment cells
0:17:17 > 0:17:18for the best possible copy.
0:17:24 > 0:17:28Incredibly, it has to assume how the pattern would continue
0:17:28 > 0:17:30if its body wasn't there.
0:17:32 > 0:17:37On familiar ground the match is perfect.
0:17:40 > 0:17:44If the octopus' camouflage fails, it has other tactics.
0:17:47 > 0:17:50Throwing sand in the face is one.
0:17:50 > 0:17:53So is whipping up a smokescreen.
0:17:53 > 0:17:58The ink is made of the black pigment, melanin.
0:18:03 > 0:18:06It escapes under the cover of darkness.
0:18:11 > 0:18:17The octopus's last trick is that of a contortionist.
0:18:18 > 0:18:23It can squeeze through a hole one tenth its body width.
0:18:25 > 0:18:31Its shrink-to-fit routine is limited only by the size of its beak.
0:18:31 > 0:18:34Once these hard mouth parts are through,
0:18:34 > 0:18:36the rest is easy.
0:18:55 > 0:18:59But the best shape-shifting act belongs to another of its kind.
0:19:13 > 0:19:16This is the amazing vampire squid.
0:19:18 > 0:19:23This rare, deep-sea octopus has an equally rare defence.
0:19:23 > 0:19:26It turns itself inside-out.
0:19:30 > 0:19:34The armoury of spines makes it seem impregnable.
0:19:36 > 0:19:38But its spines are soft as jelly.
0:19:38 > 0:19:43It seems this is just an amazing bluff.
0:19:45 > 0:19:50Other creatures of the depths have equally odd defences.
0:19:55 > 0:19:56In the cold fjords of Sweden,
0:19:56 > 0:20:01crab fishermen occasionally dredge up more than they bargained for.
0:20:10 > 0:20:12These are hagfish,
0:20:12 > 0:20:16relics from before the age of dinosaurs.
0:20:18 > 0:20:23Their peculiar miracle is turning seawater into slime.
0:20:25 > 0:20:29Glands that line their body fire out protein pellets
0:20:29 > 0:20:33that swell on contact with water.
0:20:33 > 0:20:36Other glands fire explosive threads.
0:20:36 > 0:20:40Together, they form an impenetrable slime barrier
0:20:40 > 0:20:42that suffocates predators.
0:20:45 > 0:20:47To avoid the same vile fate,
0:20:47 > 0:20:51the hagfish can slip off its slimy coat
0:20:51 > 0:20:54by passing a knot down its body.
0:20:59 > 0:21:02One hagfish oozes enough gunge
0:21:02 > 0:21:06to turn a whole bucket of water into slime.
0:21:06 > 0:21:09As well as deterring predators,
0:21:09 > 0:21:13this gloopy mucus keeps rival hagfish away,
0:21:13 > 0:21:16as they scavenge on rotted carcasses.
0:21:33 > 0:21:38Even hungry birds find this slippery fish too slimy to swallow.
0:22:01 > 0:22:07In Scandinavia, fieldfares use equally foul play on intruders.
0:22:12 > 0:22:17Fieldfares nest together, so one alarm call rallies the whole colony.
0:22:17 > 0:22:20LOW-PITCHED CHIRPING
0:22:20 > 0:22:24All who trespass are dealt the same dirty trick.
0:22:44 > 0:22:48Even though humans have little natural protection,
0:22:48 > 0:22:52we've made up for it with some deadly inventions.
0:22:56 > 0:23:01But these birds have their own fire power.
0:23:10 > 0:23:13GUNSHOT
0:23:13 > 0:23:16The whole squadron is scrambled.
0:23:23 > 0:23:28The hunter gets his comeuppance. On birds of prey the droppings
0:23:28 > 0:23:33can be fatal, destroying the waterproofing of their plumage.
0:23:33 > 0:23:38The fulmar's defence tactics are even more repulsive.
0:23:40 > 0:23:43Its frontline defence is a mountain fortress
0:23:43 > 0:23:46that keeps land predators from the breeding colony.
0:23:50 > 0:23:53The young are left for hours on these sea stacks
0:23:53 > 0:23:58as their parents make long fishing trips far offshore.
0:24:01 > 0:24:04Wise climbers avoid nesting cliffs.
0:24:04 > 0:24:08They know that chicks left home alone have a secret weapon.
0:24:10 > 0:24:15But what happens if a climber takes the wrong route?
0:24:15 > 0:24:20Chicks brew up an oily concoction in their stomachs from fish they eat.
0:24:24 > 0:24:29They save this vile soup for the times they're left alone.
0:24:29 > 0:24:33The chicks' usual threat is predatory birds,
0:24:33 > 0:24:37but anything within spitting distance becomes a target.
0:24:37 > 0:24:41It fires a warning shot, followed by a blast.
0:24:54 > 0:24:56The vomit is made from fish oils,
0:24:56 > 0:24:59separated in the stomach from other food.
0:25:00 > 0:25:06What repels a climber could kill a bird. The vomit also damages plumage,
0:25:06 > 0:25:09causing hypothermia or drowning.
0:25:12 > 0:25:16Birds that use projectile vomiting may seem bizarre.
0:25:19 > 0:25:25But humans are weirder. We evolved to have no natural defences at all.
0:25:35 > 0:25:38Our safety net is our technology
0:25:38 > 0:25:42and a brain that quickly learns from mistakes.
0:25:49 > 0:25:54Few animals are so poorly equipped to defend themselves.
0:25:54 > 0:25:58In nature's terms, it is WE who are weird.
0:26:18 > 0:26:23Other animals even employ acting skills as a defence.
0:26:28 > 0:26:31This is not what it seems.
0:26:31 > 0:26:33These animals are far from dead.
0:26:41 > 0:26:45They are putting on a remarkable performance.
0:26:51 > 0:26:55Only a hint of movement gives the game away.
0:27:00 > 0:27:04Birds enter this trance-like state quite readily.
0:27:07 > 0:27:12Frogs appear to die if turned on their backs,
0:27:12 > 0:27:15but it's just a bluff.
0:27:18 > 0:27:23The hognose snake lolls its tongue to fake death throes
0:27:23 > 0:27:26and gives off the stench of decay.
0:27:27 > 0:27:32The opossum gave death-feigning a name.
0:27:32 > 0:27:33As it plays possum,
0:27:33 > 0:27:38anal secretions make it smell like a rotten corpse.
0:27:38 > 0:27:41This behaviour is easily triggered
0:27:41 > 0:27:44by harmless hypnosis techniques.
0:27:44 > 0:27:48Strangely, the animals often wake up together.
0:27:53 > 0:27:58Playing dead works because most predators won't touch carrion.
0:28:03 > 0:28:07Danger gone, they quietly leave the stage.
0:28:14 > 0:28:18Among nature's devious feats of deception,
0:28:18 > 0:28:22playing possum must be as weird as it gets.
0:28:33 > 0:28:39Our next weird journey looks at the bizarre ways animals breed.