0:00:05 > 0:00:10There was a time when myths and science were entwined,
0:00:10 > 0:00:16when mermaids and unicorns could mysteriously appear...
0:00:23 > 0:00:28..and devilfish flew the oceans.
0:00:28 > 0:00:31Nature was weird.
0:00:31 > 0:00:36When science revealed the truth behind these imaginary creatures,
0:00:36 > 0:00:41it found REAL animals lay behind the legends.
0:00:45 > 0:00:51Today, science still makes astonishing discoveries.
0:00:53 > 0:00:55But nature seems just as weird.
0:01:01 > 0:01:06It's just that fact has broken free from fiction.
0:01:24 > 0:01:30In Weird Nature, real animal behaviour is set against human backdrops.
0:01:30 > 0:01:33They give astonishing insights.
0:01:36 > 0:01:43The spiral tusk of the unicorn has been traced to a white whale, just as wonderful as the legend.
0:01:47 > 0:01:53The narwhal uses its twisted horns in jousts, like a medieval knight.
0:01:58 > 0:02:03The mermaid's forked tail belongs to the dugong.
0:02:05 > 0:02:10Half-seen, its body and face can appear surprisingly human.
0:02:14 > 0:02:16The devilfish is a manta ray.
0:02:16 > 0:02:21They leap to shed parasites and then briefly glide, like phantom craft.
0:02:24 > 0:02:29Weird nature takes you into a world where imaginary human settings
0:02:29 > 0:02:34showcase animal behaviour that is absolutely real.
0:02:34 > 0:02:40What is weird is best defined when compared to our own lives.
0:02:41 > 0:02:47Our first weird journey shows the wonderful ways that animals move.
0:02:57 > 0:03:01Life began in the oceans.
0:03:03 > 0:03:07This imaginary wreck brings together some early forms of motion.
0:03:11 > 0:03:18Jellyfish are the only animal to move by wafting water through a pulsating skirt,
0:03:18 > 0:03:22but such graceful jet propulsion is no match for the tides.
0:03:30 > 0:03:34A strange ancient mollusc improved the concept.
0:03:36 > 0:03:44The nautilus jets water through a siphon that can move to control direction.
0:03:46 > 0:03:54It controls depth, by regulating gas in a series of buoyancy chambers in its shell.
0:03:57 > 0:04:03Flame scallops jet-propel by clapping their shells like castanets.
0:04:08 > 0:04:12They jet water from either side of their hinge.
0:04:13 > 0:04:18They dance to escape predators or to find new places.
0:04:23 > 0:04:27The Spanish dancer's technique is more elegant.
0:04:27 > 0:04:33It flamencos, by rippling the ribbons along its body.
0:04:33 > 0:04:37The frills of its costume are actually gills,
0:04:37 > 0:04:42and, despite its romantic name, it's really a sea slug.
0:04:59 > 0:05:05The sea horse can't move its armoured body in sinuous waves, like other swimming fish.
0:05:05 > 0:05:11Instead, a fin that quivers 20 times a second whirrs it around.
0:05:14 > 0:05:19Shimmering side fins act as steering propellers.
0:05:35 > 0:05:41Jointed legs were an exciting new movement in evolution.
0:05:41 > 0:05:43Spiny lobsters used them to conga.
0:05:43 > 0:05:50Their procession provides safety in numbers, as they move to deeper water to avoid winter storms.
0:05:55 > 0:06:00The slipstream from the leader cuts drag for those behind.
0:06:09 > 0:06:14Legs helped animals make the next evolutionary step.
0:06:15 > 0:06:18Today, we prefer faster options.
0:06:18 > 0:06:21But legs have been in vogue
0:06:21 > 0:06:25since the first amphibians crawled from the sea.
0:06:25 > 0:06:31They dragged their bodies along, using four legs, splayed to the side.
0:06:31 > 0:06:35The Mount Lyell salamander uses its tail as a fifth leg
0:06:35 > 0:06:40to negotiate the Sierra Nevada mountainside.
0:06:40 > 0:06:44They are also special in more human terms.
0:06:50 > 0:06:54The wheel was hailed as one of our greatest inventions.
0:06:54 > 0:06:58But, as these creatures prove,
0:06:58 > 0:07:00we were simply reinventing it!
0:07:08 > 0:07:14Rolling is the quickest way down a hill,
0:07:14 > 0:07:17as this salamander has discovered.
0:07:32 > 0:07:37It's designed to flex like a rubber tyre, so it doesn't feel the bumps.
0:07:41 > 0:07:45The pearl moth caterpillar is common,
0:07:45 > 0:07:49but its talent for doing "wheelies" is a new discovery.
0:07:55 > 0:08:00It rolls with its caterpillar track on the inside.
0:08:10 > 0:08:15Salamanders and caterpillars were born to rock'n'roll,
0:08:15 > 0:08:18so this behaviour is second nature.
0:08:22 > 0:08:26The salamander's more normal motion
0:08:26 > 0:08:32can cause problems for heavier creatures that move in the same way.
0:08:32 > 0:08:39For the early reptiles, crawling along the ground was literally a drag.
0:08:39 > 0:08:42Crocodiles had an odd solution.
0:08:42 > 0:08:47Walking on stilts cuts friction on rough ground.
0:08:47 > 0:08:52But the splayed feet have to rotate forward to take a step.
0:08:59 > 0:09:03It may be slow, but it saves energy,
0:09:03 > 0:09:08and most crocs use this stiff-legged walk whenever the going gets rough.
0:09:17 > 0:09:23The Australian fresh-water croc shows an even stranger gait,
0:09:23 > 0:09:28when provoked by predators, such as the salt-water croc.
0:09:33 > 0:09:36It gallops...
0:09:36 > 0:09:38but not like any other animal.
0:09:38 > 0:09:43Its front feet work together in opposite motion to the back.
0:09:43 > 0:09:48As the front feet hit the ground, the back swing forward.
0:09:48 > 0:09:52When the back push away, the front reach out.
0:09:57 > 0:10:01Galloping horses were once painted like this.
0:10:01 > 0:10:06In truth, only fresh-water crocs run in this seesaw way.
0:10:06 > 0:10:12It can reach 15mph and easily leap to safety.
0:10:20 > 0:10:24Evolution has taken many weird twists and turns.
0:10:28 > 0:10:33Each year, 20 million leapers of a more playful kind
0:10:33 > 0:10:37arrive in the world's toy shops, from a tiny part of Mexico.
0:10:43 > 0:10:49The jumping bean is really the seed of a desert shrub.
0:10:49 > 0:10:52Only a few show this odd leaping.
0:11:08 > 0:11:12The seeds, imported as novelty toys,
0:11:12 > 0:11:14seem to have a mind of their own.
0:11:22 > 0:11:25There really IS a mind behind the jumping.
0:11:25 > 0:11:30A moth caterpillar lives and feeds inside the seed.
0:11:31 > 0:11:36The caterpillars flip their home to escape.
0:11:36 > 0:11:38They not only feel the heat,
0:11:38 > 0:11:41light makes them jumpy.
0:11:41 > 0:11:44They fuss and fidget into the shade.
0:11:48 > 0:11:53This behaviour is a life-saver in the hot Mexican desert.
0:11:58 > 0:12:02The caterpillar repairs the damage by weaving a silken wall.
0:12:16 > 0:12:21It grips onto the silk wall when it leaps.
0:12:21 > 0:12:23The shape of the bean helps it roll.
0:12:39 > 0:12:45For weirdness, the Mexican jumping bean is hard to beat.
0:12:47 > 0:12:50But Sifaka lemurs from Madagascar
0:12:50 > 0:12:54turn leaping into a surreal ballet.
0:13:00 > 0:13:07The secret of their graceful pogo-ing stems from a life in the trees.
0:13:09 > 0:13:12They can leap 30m with ease.
0:13:14 > 0:13:21These acrobatic skills have to be modified for the challenge of moving over the ground.
0:13:21 > 0:13:25The legs act as springs...
0:13:27 > 0:13:32..and feet curled for gripping become landing pads.
0:13:38 > 0:13:44With no branches to grab, the arms are free to act as stabilisers.
0:13:54 > 0:14:00Every move of the legs is complemented by a matching move of the arms.
0:14:11 > 0:14:16The balletic poses maintain perfect balance.
0:14:27 > 0:14:34Sifakas only show such bizarre and beautiful motion because they evolved for a life in the trees.
0:14:36 > 0:14:40The same is true of the bushbaby.
0:14:45 > 0:14:48This time-slice sequence
0:14:48 > 0:14:52shows the various poses a bushbaby adopts as it jumps.
0:14:52 > 0:14:57It leaps two-and-a-quarter metres in height -
0:14:57 > 0:15:02equivalent to us clearing two stacked double-decker buses.
0:15:04 > 0:15:09To achieve this, the legs and feet act like springs,
0:15:09 > 0:15:14converting the energy of impact back into propulsion.
0:15:14 > 0:15:18It really DOES have a spring in its step.
0:15:21 > 0:15:27It waits until the peak of its jump before reaching out.
0:15:29 > 0:15:32The tail acts as a counterbalance.
0:15:35 > 0:15:40It's like a rubber ball with a brain -
0:15:40 > 0:15:45almost impossible for a predator to catch.
0:16:02 > 0:16:07This sequence freezes a bushbaby as it becomes airborne.
0:16:07 > 0:16:12But gliding animals specialise in prolonging their time in the air.
0:16:17 > 0:16:22The golden tree frog of Malaysia is a treetop acrobat.
0:16:24 > 0:16:27Usually, it hops just a few metres.
0:16:27 > 0:16:30But if it meets a golden tree snake,
0:16:30 > 0:16:34it happily makes a leap into the unknown.
0:16:44 > 0:16:52As it plummets, spread limbs slow its descent, and its webbed feet double up as a parachute.
0:16:58 > 0:17:03The Javan flying frog goes one better.
0:17:03 > 0:17:08Its webbed feet have evolved into miniature wings.
0:17:10 > 0:17:15Instead of parachuting, it paraglides at an angle.
0:17:23 > 0:17:28But it's the Wallace frog that achieves aeronautical perfection.
0:17:34 > 0:17:41Its huge webbed feet become aerofoils that slow and control its descent.
0:17:43 > 0:17:48It glides as far forward as the distance it falls.
0:17:48 > 0:17:54As well as winged feet, its whole body is aerodynamically shaped.
0:17:54 > 0:17:58This is classic evolution.
0:17:58 > 0:18:03One feature progressively improved until perfection is achieved.
0:18:19 > 0:18:22Lizards lack webbed feet,
0:18:22 > 0:18:27so they expand other body features to get their wings.
0:18:28 > 0:18:35The flying gecko's impressive glide angle is due to wing-like fringes on its body.
0:18:37 > 0:18:42Every available edge has an aerodynamic extension.
0:18:47 > 0:18:52But it's the draco lizard whose design really flies.
0:18:55 > 0:18:59A huge aerofoil turns the draco into a living Frisbee,
0:18:59 > 0:19:02while its tail steers like a rudder.
0:19:02 > 0:19:07Foldable ribs act as support struts to create the perfect wing.
0:19:08 > 0:19:16The golden tree snake uses other aeronautical tricks for its leap of faith.
0:19:20 > 0:19:24It loops its body for the ultimate take-off,
0:19:24 > 0:19:29and projects forward to gain a head start.
0:19:29 > 0:19:37It then flattens into a ribbon and swims through the air using S-shaped waves of its body.
0:19:40 > 0:19:47The star of this jungle air show is the owner of the most extravagant wings.
0:19:48 > 0:19:54From 80m up, the Wallace frog glides 80m forward.
0:19:54 > 0:19:57The gecko soars 100m.
0:19:57 > 0:20:01But nothing beats the flying Frisbee.
0:20:01 > 0:20:04The draco reaches a full 200m.
0:20:06 > 0:20:12Even a flying snake makes 150, complete with controlled landing!
0:20:12 > 0:20:18A lack of legs has made snakes devise other weird ways of moving.
0:20:18 > 0:20:21SIREN WAILS
0:20:21 > 0:20:29In the deserts of the American South-West, off-road travelling is notoriously difficult.
0:20:32 > 0:20:37Shifting sand is one of the most challenging surfaces to negotiate.
0:20:48 > 0:20:56The horned rattlesnake's solution is to touch the sand with as little of its body as possible.
0:20:58 > 0:21:03Appropriately, its nickname is the sidewinder.
0:21:04 > 0:21:09Like tyre tread, a snake's scales usually grip the ground as it moves.
0:21:09 > 0:21:12But sand simply gives way.
0:21:14 > 0:21:21So the snake makes an S-shape with its body and lifts the loops in a rolling corkscrew.
0:21:21 > 0:21:28This continually shifts the points of contact to stop that sinking feeling.
0:21:33 > 0:21:39As waves of grip pass down the body, the snake rapidly picks up speed.
0:21:45 > 0:21:49Its hidden prey can also make a surprise move.
0:22:04 > 0:22:09Sidewinders avoid being buried by sand.
0:22:09 > 0:22:13Others welcome its smothering embrace.
0:22:23 > 0:22:29This predator spends much of its life lurking just beneath the surface.
0:22:34 > 0:22:39It can swim through shifting sand, like an eel up a river...
0:22:40 > 0:22:44..because the grains act like liquid rock.
0:22:44 > 0:22:51The sand swimmer's wedge-shaped head parts the grains like the prow of a boat.
0:22:54 > 0:22:59Its over-slung upper jaw stops it swallowing sand,
0:22:59 > 0:23:03and it can close its nostrils to avoid suffocating.
0:23:03 > 0:23:11As the snake submerges, its polished scales slip through the grains as if immersing in water.
0:23:17 > 0:23:21Nature shows many wonderful forms of travelling.
0:23:21 > 0:23:25Those that seem weird are usually the least familiar.
0:23:25 > 0:23:32But although we think we're normal, in nature, it is WE who are peculiar.
0:23:38 > 0:23:43Our two legs place us among the world's oddest animals.
0:23:43 > 0:23:47We are the only mammal to regularly walk like this.
0:23:50 > 0:23:56Sometimes, other primates hint at the origins of our strange bipedal walk.
0:23:56 > 0:24:00Proboscis monkeys use it to cross mangroves.
0:24:02 > 0:24:06A few scientists think we were once semi-aquatic.
0:24:06 > 0:24:10Walking like this kept our heads above water.
0:24:13 > 0:24:18Others believe that freeing the hands for gripping or carrying
0:24:18 > 0:24:22allowed a land ape to bring back food to a family.
0:24:25 > 0:24:29Whatever the reason, animals that walk like us seem strange.
0:24:29 > 0:24:35We find it weird to see our actions mirrored in other animals.
0:24:41 > 0:24:48In the age of the dinosaurs, we might have felt more at home. Many were also bipedal.
0:24:48 > 0:24:53Today, a few unrelated lizards continue in their footsteps.
0:24:56 > 0:24:58Oww!
0:25:01 > 0:25:08Like a miniature tyrannosaur, the collared lizard hunts on two legs.
0:25:10 > 0:25:14But it is more agile than any dinosaur,
0:25:14 > 0:25:17and, size for size, much faster.
0:25:29 > 0:25:34Being smaller gives speed and manoeuvrability.
0:25:35 > 0:25:39Most bipedal lizards live in deserts.
0:25:39 > 0:25:42This kind of running needs space.
0:25:42 > 0:25:47When hunting other lizards, two legs give it the edge.
0:26:05 > 0:26:07The tyrannosaur's modern equivalent.
0:26:09 > 0:26:15But while this lizard uses two legs for speed, we now prefer alternatives.
0:26:18 > 0:26:23The dinosaur's REAL descendants are birds.
0:26:23 > 0:26:28Because they fly, we rarely notice that they walk on two legs like we do.
0:26:28 > 0:26:32But the roadrunner is an exception.
0:26:32 > 0:26:36Its comical, human-like gait made it a cartoon character.
0:26:42 > 0:26:47To save energy for its sprint, the roadrunner exposes a solar panel.
0:26:47 > 0:26:52This dark skin patch raises its body temperature seven degrees.
0:27:00 > 0:27:05It's primed for a super-heated performance.
0:27:18 > 0:27:25To the roadrunner, our open roads are racetracks, good for chasing insects and lizards.
0:27:28 > 0:27:32Its tiny legs take it to 26mph.
0:27:32 > 0:27:36If our legs moved this fast, we would overtake any speeding bike.
0:27:47 > 0:27:51Because two-legged running limits our own speed,
0:27:51 > 0:27:56we use artificial means of travel, such as flying.
0:27:56 > 0:28:03But even though it CAN fly, the strange roadrunner chooses to run on two legs for speed.
0:28:08 > 0:28:11Our machines take us ever-faster...
0:28:11 > 0:28:13and we sometimes pay the price.
0:28:13 > 0:28:18But when we smile at the roadrunner's bipedal running,
0:28:18 > 0:28:23are we recognising our OWN weird nature?
0:28:33 > 0:28:35Our next weird journey looks at
0:28:35 > 0:28:39the strange ways animals defend themselves.