0:00:04 > 0:00:09Of all the animals in the world,
0:00:09 > 0:00:11there are some that really stand out.
0:00:11 > 0:00:13Look at you.
0:00:13 > 0:00:16'That we think are special.'
0:00:16 > 0:00:22We find them undeniably, almost unbearably cute.
0:00:25 > 0:00:28Millions of us watch these animals online.
0:00:28 > 0:00:33But behind every feature we love so much -
0:00:33 > 0:00:36that big round head...
0:00:36 > 0:00:38PANDA CUB SNEEZES
0:00:38 > 0:00:40FROG SQUEAKS
0:00:40 > 0:00:42..surprising sounds...
0:00:42 > 0:00:45You are super, super cool.
0:00:45 > 0:00:46CHIMPANZEE LAUGHS
0:00:46 > 0:00:49..or those wide eyes -
0:00:49 > 0:00:53is a secret survival strategy.
0:00:53 > 0:00:55CAT PURRS
0:00:56 > 0:00:59I'm Gordon Buchanan.
0:00:59 > 0:01:03I've filmed our favourite animals all over the world.
0:01:03 > 0:01:06Now, I want to discover
0:01:06 > 0:01:09the hidden biology of these animal superstars.
0:01:09 > 0:01:11Whoa.
0:01:11 > 0:01:13HE CHUCKLES
0:01:13 > 0:01:17Why this sweet face hides a deadly secret...
0:01:17 > 0:01:19HUMMINGBIRD SNORES
0:01:19 > 0:01:22..why hummingbirds snore...
0:01:22 > 0:01:24HUMMINGBIRD SNORES
0:01:24 > 0:01:27..and penguins waddle.
0:01:27 > 0:01:29PENGUIN SHRIEKS
0:01:31 > 0:01:34Behind every appealing animal
0:01:34 > 0:01:37is an incredible story.
0:01:38 > 0:01:41And I'm going to reveal their secrets.
0:01:52 > 0:01:55If you took a poll of the top 20 animals on the planet,
0:01:55 > 0:01:58I reckon these guys would be right at the top.
0:01:58 > 0:02:03They are fantastic, those enormous ears, their trunks, beautiful eyes.
0:02:04 > 0:02:06I just love them.
0:02:08 > 0:02:10But we've all got our own favourites,
0:02:10 > 0:02:14animals we find irresistibly appealing.
0:02:14 > 0:02:17Hello. How you doing?
0:02:17 > 0:02:20Sometimes we fall for the sounds they make.
0:02:20 > 0:02:23Is that an invitation for me to tickle you?
0:02:23 > 0:02:25It is, it is.
0:02:25 > 0:02:29Others move in ways that delight us.
0:02:31 > 0:02:35But often it's simply the way an animal looks
0:02:35 > 0:02:38that makes it so compelling.
0:02:40 > 0:02:48And they don't come much better looking than the iconic giant panda.
0:02:51 > 0:02:55Famous as a symbol for conservation...
0:02:55 > 0:02:58and for its sneeze.
0:03:00 > 0:03:01PANDA CUB SNEEZES
0:03:01 > 0:03:04Maybe you were one of the 200 million people
0:03:04 > 0:03:07that watched this online.
0:03:07 > 0:03:08PANDA CUB SNEEZES
0:03:10 > 0:03:14Our monochrome love affair began in the 1970s
0:03:14 > 0:03:19when China gave the first pandas to the Smithsonian Zoo.
0:03:20 > 0:03:22And just last year,
0:03:22 > 0:03:27their newest baby had over two million visitors,
0:03:27 > 0:03:31all desperate to get a glimpse.
0:03:33 > 0:03:37I've come to meet the little crowd-pleaser.
0:03:39 > 0:03:41Hello, Bao Bao.
0:03:42 > 0:03:49You really are the most adorable panda in the world.
0:03:51 > 0:03:55Pandas really have to be one of the most recognisable animals
0:03:55 > 0:03:59on the planet and arguably one of the best-loved.
0:03:59 > 0:04:04They are an extraordinarily good-looking animal.
0:04:06 > 0:04:08Now, pandas aren't the biggest of bears.
0:04:08 > 0:04:10If you want overall size,
0:04:10 > 0:04:14you have to look at brown bears or polar bears,
0:04:14 > 0:04:17but look at the size of that head.
0:04:17 > 0:04:23It is much bigger, much rounder than that of any other bear
0:04:23 > 0:04:26and it's that beautiful big face that really
0:04:26 > 0:04:30stops them looking like a predator.
0:04:30 > 0:04:33Makes them look less threatening
0:04:33 > 0:04:35and when you look into the face of a panda,
0:04:35 > 0:04:38you don't feel any threat at all.
0:04:45 > 0:04:52It's her beautiful face that makes little Bao Bao so appealing.
0:04:52 > 0:04:55But why is it proportionally so much bigger
0:04:55 > 0:04:58and rounder than other bear cubs?
0:05:01 > 0:05:05Pandas are classed as carnivores.
0:05:05 > 0:05:09They have the teeth and claws of meat-eaters
0:05:09 > 0:05:11but they don't act like carnivores.
0:05:14 > 0:05:17Around five million years ago,
0:05:17 > 0:05:20pandas actually lost the taste for meat.
0:05:22 > 0:05:27They switched to the food source that was most abundant.
0:05:30 > 0:05:32A sensible choice you'd think,
0:05:32 > 0:05:38except a stick of bamboo has barely any calories.
0:05:38 > 0:05:42Especially compared with a hunk of red meat.
0:05:48 > 0:05:53So, the panda is a carnivore that has gone vegetarian
0:05:53 > 0:05:56and it has chosen one of THE toughest food sources around,
0:05:56 > 0:05:58this stuff, bamboo.
0:05:58 > 0:06:02They don't just eat these nice leaves,
0:06:02 > 0:06:04which...
0:06:04 > 0:06:06urgh, to me, pretty unappetising.
0:06:06 > 0:06:11They will grind and pulverise even the thickest stems.
0:06:11 > 0:06:13Oh, my goodness.
0:06:13 > 0:06:18You get into this stuff, look at all those splinters.
0:06:18 > 0:06:22A bear like the highly carnivorous polar bear can survive for days
0:06:22 > 0:06:24and days on a single kill, but for a panda,
0:06:24 > 0:06:28to get enough calories to survive just eating this,
0:06:28 > 0:06:33they have to eat for, wait for this, 16 hours a day.
0:06:33 > 0:06:37Breakfast, lunch and dinner is bamboo.
0:06:39 > 0:06:41So to cope with the challenges of a bamboo diet,
0:06:41 > 0:06:46the panda's body has had to change, adapt and evolve to deal with it.
0:06:46 > 0:06:48Their stomach lining has grown thicker
0:06:48 > 0:06:51to deal with all those splinters.
0:06:53 > 0:06:57But it's the skull that has changed most dramatically.
0:06:59 > 0:07:02Just looking at this skull, you can see that it's unlike
0:07:02 > 0:07:04the skull of any other bear.
0:07:04 > 0:07:08The bone itself is much denser, thicker and wider
0:07:08 > 0:07:12and that allows these huge jaw muscles to attach.
0:07:13 > 0:07:19This gives the panda a stronger bite force than a polar bear.
0:07:21 > 0:07:25And it's this bamboo diet that has created this massive head,
0:07:25 > 0:07:31a massive head that has such an extraordinary appeal for us.
0:07:34 > 0:07:39The irony is, when covered with fur,
0:07:39 > 0:07:42this mass of muscle and bone
0:07:42 > 0:07:45looks like a teddy bear.
0:07:49 > 0:07:53And Bao Bao's markings only make her more appealing.
0:08:00 > 0:08:04In the wild, the eye-catching black and white
0:08:04 > 0:08:08actually breaks up the panda's silhouette in the snowy forest...
0:08:09 > 0:08:12..and makes the eyes look bigger,
0:08:12 > 0:08:15more threatening to rivals and predators.
0:08:17 > 0:08:22But the illusion has the complete opposite effect on us.
0:08:25 > 0:08:29So, why have we fallen for these oversized features?
0:08:31 > 0:08:37Well, bizarrely, it's all down to our own biology.
0:08:39 > 0:08:44Big eyes trigger exactly the same emotional response in us
0:08:44 > 0:08:48as when we see the panda's oversized head and that's really
0:08:48 > 0:08:52because of the way that we respond when we see our own babies.
0:08:52 > 0:08:55We're all born with these big heads and big eyes
0:08:55 > 0:08:58and when we see those features,
0:08:58 > 0:09:03our nurturing, caring instincts spring into action.
0:09:04 > 0:09:08At the sight of Bao Bao's big baby-like head,
0:09:08 > 0:09:13blood rushes to our midbrain -
0:09:13 > 0:09:16part of the brain's "pleasure centre".
0:09:18 > 0:09:22A flood of dopamine is released,
0:09:22 > 0:09:26one of the hormones produced when we fall in love.
0:09:27 > 0:09:32This chemical reaction creates emotions,
0:09:32 > 0:09:35it's what makes us go all gooey.
0:09:37 > 0:09:40Psychologists call it the "cute response"
0:09:40 > 0:09:45and the "cute response" is so powerful, primitive and deep-rooted
0:09:45 > 0:09:50that it can be triggered when we see those features in other species,
0:09:50 > 0:09:51in animals.
0:09:51 > 0:09:57Our love of the panda is down to our evolutionary hardwiring.
0:09:57 > 0:10:00We just can't help it.
0:10:14 > 0:10:16The power of the cute response
0:10:16 > 0:10:20was perfectly demonstrated a few years ago...
0:10:21 > 0:10:25..when a funny little creature grabbed global attention.
0:10:27 > 0:10:28But I warn you,
0:10:28 > 0:10:33it's not as sweet a story as it seems.
0:10:35 > 0:10:41A video of a ticklish slow loris took the internet by storm.
0:10:41 > 0:10:44WOMAN LAUGHS
0:10:44 > 0:10:46Six million hits.
0:10:48 > 0:10:54We couldn't get enough of this wide-eyed little gremlin.
0:10:57 > 0:11:00For loris expert Anna Nekaris,
0:11:00 > 0:11:04the overnight celebrity came as a bit of a shock.
0:11:05 > 0:11:08Slow lorises are very rare in the wild and so
0:11:08 > 0:11:11until about ten years ago, hardly anyone had heard of a slow loris
0:11:11 > 0:11:15and then they became one of the most popular animals on the internet.
0:11:15 > 0:11:20For many people, a slow loris is a quintessentially cute animal.
0:11:22 > 0:11:25Its head is like a little round ball on top of a round body
0:11:26 > 0:11:30and it's just got a really, sweet, innocent, cute face.
0:11:32 > 0:11:34But like the panda,
0:11:34 > 0:11:39it's the loris' biggest feature that makes it so appealing.
0:11:41 > 0:11:44Its huge eyes.
0:11:46 > 0:11:52They send our cute response into overdrive.
0:12:01 > 0:12:07But it's in the wild that the true purpose of those incredible eyes
0:12:07 > 0:12:12and the dark side of the sweet little loris is revealed.
0:12:15 > 0:12:18Lorises are nocturnal.
0:12:20 > 0:12:25In the dark, their huge pupils dilate wide.
0:12:26 > 0:12:31This allows all available light to pass straight into the eye.
0:12:33 > 0:12:39It gives them excellent vision even in the faintest of starlight,
0:12:39 > 0:12:42which they use to stalk...
0:12:43 > 0:12:46..and catch prey.
0:12:56 > 0:13:00They may look really cute but when they grab their prey,
0:13:00 > 0:13:04they're very vicious and the first thing they do is shred its head off,
0:13:04 > 0:13:07and very proudly they lick it like a little lollipop
0:13:07 > 0:13:10and eat the entire thing, all the wings, all the bones.
0:13:10 > 0:13:14And their appetite isn't limited to insects.
0:13:18 > 0:13:23This loris has set its sights on a roosting bird.
0:13:28 > 0:13:31If that isn't enough to put you off your dinner,
0:13:31 > 0:13:35they have an even more unsavoury skill.
0:13:38 > 0:13:41What strikes one most if you see a slow loris
0:13:41 > 0:13:44is that they have a long back with a dark stripe
0:13:44 > 0:13:47and when they climb they move like a snake,
0:13:47 > 0:13:50their spine moves in an S-shape, and if you try to catch one,
0:13:50 > 0:13:53they hiss at you just like a snake.
0:13:53 > 0:13:55They raise their arms above their head
0:13:55 > 0:13:58and they form a hood above their head, like a cobra.
0:14:00 > 0:14:03Because the internet cutie
0:14:03 > 0:14:07is the world's only venomous primate.
0:14:12 > 0:14:16Lorises secrete an oil from their elbow which,
0:14:16 > 0:14:19when mixed with their saliva,
0:14:19 > 0:14:22creates a deadly cocktail.
0:14:22 > 0:14:25We know people who've lost half a limb, who've lost fingers,
0:14:25 > 0:14:29people who've nearly died and people who have died from their bite,
0:14:29 > 0:14:32so it's an animal you don't want to mess with despite the fact
0:14:32 > 0:14:34it looks so appealing.
0:14:36 > 0:14:41So, probably best not to tickle one then.
0:14:43 > 0:14:45In the case of the slow loris,
0:14:45 > 0:14:51our instinctive cute response is actually misleading us.
0:14:51 > 0:14:55We see those big eyes, we imagine the loris is completely harmless,
0:14:55 > 0:15:00we want to care for it, we even want to own one as a pet.
0:15:00 > 0:15:04And clearly as the world's only venomous primate,
0:15:04 > 0:15:06it's not the best animal to have around the house.
0:15:06 > 0:15:09It's illegal to buy lorises
0:15:09 > 0:15:13but the demand is so high caused by these videos
0:15:13 > 0:15:17that lorises have become extinct in many of their jungle habitats.
0:15:17 > 0:15:22It's a cautionary tale that cute can be a curse.
0:15:28 > 0:15:33Oversized heads and big round eyes
0:15:33 > 0:15:35push our biological buttons.
0:15:37 > 0:15:41But the power of the cute response doesn't stop there.
0:15:47 > 0:15:53I'm on my way to meet another animal favourite that proves that
0:15:53 > 0:15:58almost any feature can be a trigger as long as it's big enough.
0:16:05 > 0:16:08This is a fennec,
0:16:08 > 0:16:12smallest member of the fox family,
0:16:12 > 0:16:15weighing less than a bag of sugar.
0:16:16 > 0:16:18But it's not its size
0:16:18 > 0:16:21that's made the fennec famous.
0:16:22 > 0:16:24Those are.
0:16:25 > 0:16:32This little guy has the largest ear-to-body ratio of any carnivore.
0:16:35 > 0:16:37Have a look at those ears.
0:16:37 > 0:16:42They are phenomenal, completely over-sized.
0:16:42 > 0:16:45Don't get me wrong, I'm a big fan of all foxes,
0:16:45 > 0:16:50but those ears really are extra special.
0:16:50 > 0:16:53Hello. How you doing?
0:16:55 > 0:17:01And you see, as he's standing there, the ears are constantly rotating.
0:17:01 > 0:17:06Twitching, just drinking up every single sound.
0:17:08 > 0:17:11He's showing off his specialist skill.
0:17:14 > 0:17:18And fennec foxes are incredibly sweet-looking
0:17:18 > 0:17:22but they're also a very efficient hunter
0:17:22 > 0:17:27and those ears are the tools of their trade.
0:17:41 > 0:17:46Fennec foxes live out in the shifting sands of the Sahara.
0:17:48 > 0:17:50In miles of open desert,
0:17:50 > 0:17:54finding anything to eat can be difficult.
0:17:58 > 0:18:01A game of hide and seek.
0:18:04 > 0:18:10But fennecs have two unfair advantages.
0:18:16 > 0:18:19Those huge ears act like amplifiers -
0:18:19 > 0:18:21they gather all the sound
0:18:21 > 0:18:24and channel it towards their inner ear.
0:18:24 > 0:18:27Their hearing is so pin-sharp,
0:18:27 > 0:18:31he can hear things that I can't hear and it's said that they can
0:18:31 > 0:18:35hear a mouse's heartbeat underneath the sand.
0:18:36 > 0:18:38Quite incredible.
0:18:41 > 0:18:45OK, perhaps you might expect excellent hearing
0:18:45 > 0:18:47from a set of ears that big.
0:18:47 > 0:18:52But they have another, even more specialised role.
0:18:54 > 0:19:01It's not unusual for the temperature to reach 50 degrees in the Sahara.
0:19:01 > 0:19:05Too hot for most small mammals.
0:19:07 > 0:19:11But the fennec fox is different, aren't you?
0:19:11 > 0:19:14You can actually see when I hold him against the light,
0:19:14 > 0:19:17you can see the blood vessels through his ear.
0:19:17 > 0:19:21The skin is so thin that the heat from the blood is lost
0:19:21 > 0:19:26into the air, and this cooling of the blood allows him to keep
0:19:26 > 0:19:29his core temperature at a safe level.
0:19:29 > 0:19:31It's what keeps him alive.
0:19:33 > 0:19:37So, in fact, each ear is a radiator,
0:19:37 > 0:19:40which is a critical survival tool
0:19:40 > 0:19:44for this fantastic desert-dwelling animal.
0:19:50 > 0:19:54Facial features are clearly a key factor in
0:19:54 > 0:19:58deciding which animals we find cuter than others.
0:20:01 > 0:20:05But there's one last physical attribute
0:20:05 > 0:20:07that tops them all.
0:20:08 > 0:20:12An animal can have the biggest eyes,
0:20:12 > 0:20:14roundest face,
0:20:14 > 0:20:17but if it's not furry,
0:20:17 > 0:20:19then forget it.
0:20:20 > 0:20:27The word "fluffy" gets over 20,000 hits on search engines every week.
0:20:29 > 0:20:33The furrier the animal, the better.
0:20:34 > 0:20:39Which brings me to America's west coast.
0:20:42 > 0:20:45We associate fur with comfort, softness and warmth
0:20:45 > 0:20:49and it's no surprise really that the animals with most fur
0:20:49 > 0:20:54live in cold places, so why then am I here in California?
0:20:54 > 0:20:55Well, the answer to that is
0:20:55 > 0:21:00that the furriest animal on the planet lives just out there.
0:21:21 > 0:21:22Whoa!
0:21:22 > 0:21:23HE CHUCKLES
0:21:24 > 0:21:27OK, OK, there we go.
0:21:27 > 0:21:33Just in front of me, I can see the faces of what I'm after -
0:21:33 > 0:21:35sea otters.
0:21:38 > 0:21:42They have to be the most charming animal on the water.
0:21:42 > 0:21:45I mean just look at them, see that lovely round face,
0:21:45 > 0:21:48long whiskers.
0:21:48 > 0:21:50That one's looking a bit slick with all the water
0:21:50 > 0:21:56and there's another one that's fluffing itself up a bit.
0:21:56 > 0:22:01I've got round about five million hairs on my body,
0:22:01 > 0:22:07a sea otter has up to 800 million hairs on its body.
0:22:07 > 0:22:11That's round about one million hairs per every square inch.
0:22:11 > 0:22:14That is an astonishing amount of hair
0:22:14 > 0:22:20and that's what makes sea otters the furriest animal on the planet.
0:22:26 > 0:22:31There are 12 other species of otter around the world,
0:22:31 > 0:22:34all with impressive fur.
0:22:34 > 0:22:36OTTERS SQUEAK
0:22:39 > 0:22:42But it's not nearly as dense
0:22:42 > 0:22:46as their Californian cousins.
0:22:46 > 0:22:49So just why is a sea otter
0:22:49 > 0:22:51so furry?
0:22:55 > 0:22:59Sea otters spend 95% of their lives in the water.
0:22:59 > 0:23:01The ambient temperature is really quite warm
0:23:01 > 0:23:06but the water itself, quite chilly, maybe round about 10 degrees.
0:23:06 > 0:23:10If I fell in there, I probably wouldn't last that long.
0:23:10 > 0:23:16Other sea creatures like sea lions, walruses, they've got blubber,
0:23:16 > 0:23:19it's this thermal layer that protects their bodies.
0:23:19 > 0:23:22Sea otters don't have the luxury of blubber,
0:23:22 > 0:23:27but what they do have is fur, lots and lots of fur.
0:23:29 > 0:23:32What we see are the long, tough guard hairs.
0:23:33 > 0:23:38They provide a barrier but aren't completely waterproof.
0:23:40 > 0:23:44Below is the otter's secret weapon.
0:23:44 > 0:23:49A dense, soft underfur.
0:23:50 > 0:23:54By rolling, rubbing and fluffing,
0:23:54 > 0:23:58they push and trap air in between their fur fibres...
0:24:02 > 0:24:07..which stops cold water ever reaching their skin.
0:24:07 > 0:24:11But a sea otter's coat is more than just a dry suit.
0:24:11 > 0:24:17It plays another fundamental role in their survival out at sea.
0:24:19 > 0:24:22Sea otters are the most recently evolved marine mammal
0:24:22 > 0:24:25and so they're not as fast as seals and sea lions
0:24:25 > 0:24:28in terms of their ability to catch, you know, swimming fish.
0:24:28 > 0:24:29Here in California,
0:24:29 > 0:24:33they eat somewhere between 60 and 65 different species of prey items.
0:24:33 > 0:24:39Typically crab, sea urchin, clam, mussel.
0:24:39 > 0:24:41One of the adaptations that sea otters have for eating these
0:24:41 > 0:24:44hard-shelled prey items is that they're tool users.
0:24:44 > 0:24:45In some cases,
0:24:45 > 0:24:48it's as simple as picking a rock up off the bottom of the ocean
0:24:48 > 0:24:50and cracking clams or mussels.
0:24:50 > 0:24:54But in other situations, it can be much more complex, you know,
0:24:54 > 0:24:57we've seen otters that use things like bottles
0:24:57 > 0:24:59as either a hammer or an anvil.
0:24:59 > 0:25:03They might bang hard-shelled items against docks or boats.
0:25:07 > 0:25:09Clever stuff.
0:25:10 > 0:25:14But what's truly ingenious is how the fur comes in to play.
0:25:16 > 0:25:21Using a tool in the middle of the ocean would be almost impossible
0:25:21 > 0:25:25but all that trapped air makes the otter buoyant...
0:25:27 > 0:25:28..and its stomach -
0:25:28 > 0:25:31a floating work surface...
0:25:33 > 0:25:40..from which they can consume up to 25% of their body weight in one day.
0:25:42 > 0:25:46So, keeping this fantastically useful fur in tiptop condition
0:25:46 > 0:25:48is crucial.
0:25:50 > 0:25:53This pup will rely on mum to keep it warm,
0:25:53 > 0:25:59dry and afloat until it learns to groom for itself.
0:26:02 > 0:26:07But sometimes babies are orphaned...
0:26:07 > 0:26:09or abandoned...
0:26:10 > 0:26:15..and Karl and his team are called in.
0:26:19 > 0:26:23At the Monterey Aquarium Sea Otter Programme,
0:26:23 > 0:26:27Karl takes in pups as young as a day old.
0:26:31 > 0:26:34When we get a stranded pup, all we're trying to do is basically
0:26:34 > 0:26:38rehydrate the pups, start them on a bottle-feeding formula.
0:26:42 > 0:26:45I should probably explain Karl's get-up.
0:26:46 > 0:26:47It isn't safety gear,
0:26:47 > 0:26:51this pup is about as dangerous as he looks.
0:26:53 > 0:26:58The mask stops the pup thinking Karl is his mother.
0:27:00 > 0:27:02If he's going to make it in the wild,
0:27:02 > 0:27:05then it's best he doesn't get too attached.
0:27:08 > 0:27:12To mimic the care that a pup would get from mum,
0:27:12 > 0:27:15Karl and his team run an otter salon.
0:27:18 > 0:27:20We start out with big broad towels
0:27:20 > 0:27:23to essentially absorb most of the water.
0:27:23 > 0:27:28And once the fur's sufficiently dry, we'll start incorporating brushes.
0:27:29 > 0:27:31The brushes then allow us to
0:27:31 > 0:27:36separate the fur and get the air flow down into the underfur.
0:27:38 > 0:27:41Might take 10 or 15 minutes at a time.
0:27:41 > 0:27:43That would be one grooming session and we're doing this
0:27:43 > 0:27:47continuously throughout a 24-hour period with the pups.
0:27:47 > 0:27:52It's a tough job, Karl, but someone's got to do it.
0:27:52 > 0:27:55Their fur is so dense that they essentially float
0:27:55 > 0:27:58like little corks at the surface of the water
0:27:58 > 0:28:00and the water itself is not actually contacting the skin.
0:28:00 > 0:28:04OTTER SQUEALS
0:28:08 > 0:28:11By the time he's released back into the wild,
0:28:11 > 0:28:14the pup will have learned all the skills he needs.
0:28:16 > 0:28:19And his incredible fur will help him survive life
0:28:19 > 0:28:23as a wild otter out in the bay.
0:28:24 > 0:28:26For the panda,
0:28:26 > 0:28:28loris,
0:28:28 > 0:28:29fennec,
0:28:29 > 0:28:31and sea otter,
0:28:31 > 0:28:35supersized features are vital.
0:28:37 > 0:28:39They're what allow them to live in very
0:28:39 > 0:28:42different and challenging environments...
0:28:44 > 0:28:47..to find food
0:28:47 > 0:28:49and keep their body temperatures in check.
0:28:51 > 0:28:54But appeal isn't always just about looks.
0:28:54 > 0:28:58Sometimes it's the way an animal behaves
0:28:58 > 0:29:00that makes it a favourite.
0:29:02 > 0:29:05Elephants don't have big, forward-facing eyes,
0:29:05 > 0:29:09they're not furry, they're hairy but not fluffy
0:29:09 > 0:29:13and I'd argue with anyone that says this isn't cute,
0:29:13 > 0:29:16so something else is going on here, something else is triggering
0:29:16 > 0:29:23the cute response and I think a lot of it is to do with that nose.
0:29:31 > 0:29:35Like any newborn, the first few months of an elephant's life
0:29:35 > 0:29:36are a steep learning curve.
0:29:38 > 0:29:41Walking is tricky enough.
0:29:43 > 0:29:48But the extra appendage is even harder to get the hang of.
0:29:51 > 0:29:55Elephants are born with short, stubby trunks.
0:29:55 > 0:29:57But they elongate rapidly
0:29:57 > 0:30:00over the first few weeks.
0:30:03 > 0:30:05Mastering the movement
0:30:05 > 0:30:07can be a minefield.
0:30:15 > 0:30:17Baby elephants aren't born trunk-trained.
0:30:17 > 0:30:19For the first few months,
0:30:19 > 0:30:23an elephant's trunk has a mind all of its own
0:30:23 > 0:30:26and to watch a baby elephant learn to use its trunk
0:30:26 > 0:30:29has to be one of the most endearing things in nature.
0:30:36 > 0:30:40So why is a trunk so hard to get to grips with?
0:30:43 > 0:30:46Although we find the clumsiness endearing,
0:30:46 > 0:30:51for the elephant, this period of development is fundamental
0:30:51 > 0:30:53to their survival.
0:30:55 > 0:31:00Because the trunk isn't just any old nose.
0:31:00 > 0:31:03Elephants don't just use it to smell.
0:31:03 > 0:31:05It's a straw...
0:31:07 > 0:31:08..a hose...
0:31:10 > 0:31:12..a snorkel...
0:31:12 > 0:31:15and utensil.
0:31:23 > 0:31:28While almost every other limb in the animal kingdom uses muscle
0:31:28 > 0:31:31and bone together to create fine movement...
0:31:32 > 0:31:36..an elephant's trunk is different.
0:31:36 > 0:31:38It has no bones.
0:31:40 > 0:31:45Instead muscles alone have to stretch, contract,
0:31:45 > 0:31:49work with and against each other.
0:31:50 > 0:31:53It's called a muscular hydrostat.
0:31:54 > 0:31:56Your tongue is another example.
0:31:58 > 0:32:01Tongues use eight muscles.
0:32:01 > 0:32:06But, for a trunk to perform all the tasks an elephant needs,
0:32:06 > 0:32:10well, it takes just a few more.
0:32:15 > 0:32:20I've got just short of 650 muscles in my entire body.
0:32:20 > 0:32:23An elephant in its trunk alone
0:32:23 > 0:32:27has up to 40,000 different muscles
0:32:27 > 0:32:30and it has to use each of those muscles in different
0:32:30 > 0:32:32combinations for different tasks.
0:32:32 > 0:32:37Makes learning to ride a bike look really rather easy.
0:32:37 > 0:32:43Getting the muscle combination right is all about trial and error.
0:32:44 > 0:32:50It takes practice to master the movement of the most complex
0:32:50 > 0:32:53and useful nose on the planet.
0:32:56 > 0:32:59By the time an elephant is just one year old,
0:32:59 > 0:33:04it can use that trunk for drinking, lifting, pulling, twisting,
0:33:04 > 0:33:07even the most precise of movements
0:33:07 > 0:33:11so they're really not such slow learners after all.
0:33:15 > 0:33:21The way an animal moves can be just as appealing as how it looks.
0:33:23 > 0:33:28Our emotional response is amplified when it's a young animal
0:33:28 > 0:33:32learning how to get this movement just right.
0:33:39 > 0:33:44Clumsiness in babies of all species is another major trigger
0:33:44 > 0:33:46of the cute response.
0:33:55 > 0:34:00Which probably explains why we love penguins.
0:34:04 > 0:34:08That wonderful waddle from side to side
0:34:08 > 0:34:12makes a penguin look just like a toddling baby.
0:34:14 > 0:34:17But unlike our early teetering,
0:34:17 > 0:34:20a waddle isn't part of a learning process.
0:34:23 > 0:34:25It isn't refined or finessed.
0:34:29 > 0:34:32A chick remains Chaplin-esque
0:34:32 > 0:34:34through to adulthood.
0:34:39 > 0:34:42Most animals have evolved to get themselves
0:34:42 > 0:34:44from A to B efficiently.
0:34:45 > 0:34:49So, why do penguins resort to waddling?
0:34:50 > 0:34:54Well, although they breed and bring up their chicks on land,
0:34:54 > 0:34:58most of their lives are spent in the ocean.
0:35:05 > 0:35:09Underwater, they are transformed.
0:35:12 > 0:35:15Penguins are highly adapted to live in the water,
0:35:15 > 0:35:18they have that torpedo-like shape that means
0:35:18 > 0:35:21they can swim very fast and they actually really fly underwater.
0:35:21 > 0:35:26Their chest muscles are very large to drive their wings.
0:35:26 > 0:35:30Their legs are very short, sort of tucked away at the back.
0:35:30 > 0:35:32They act as rudders.
0:35:34 > 0:35:38They can reach bursts of 25mph
0:35:38 > 0:35:40which, compared to, say an Olympic swimmer,
0:35:40 > 0:35:45is about six maximum speed, so they're very agile.
0:35:47 > 0:35:48Emperor penguins,
0:35:48 > 0:35:52the largest penguins, can hold their breath for over half an hour
0:35:52 > 0:35:56and can reach depths of half a kilometre,
0:35:56 > 0:36:00so they're very accomplished divers and very accomplished swimmers.
0:36:02 > 0:36:06Underwater, a penguin is a torpedo in a tuxedo.
0:36:09 > 0:36:13But on land, these fantastic adaptations prove, well,
0:36:13 > 0:36:17to be a bit of a problem.
0:36:20 > 0:36:25Short legs and big feet don't help cover distance.
0:36:26 > 0:36:29PENGUINS SCREECH
0:36:29 > 0:36:35The waddle was written off as an evolutionary handicap.
0:36:35 > 0:36:38Scientists thought that waddling was very inefficient originally
0:36:38 > 0:36:41because if you look at the energy consumption of penguins
0:36:41 > 0:36:44and their walking, it's very high.
0:36:44 > 0:36:48It was thought that the side-to-side motion was wasted energy.
0:36:48 > 0:36:52But then a study of penguin locomotion
0:36:52 > 0:36:54made a surprising discovery.
0:36:59 > 0:37:03By swinging their body weight over one foot,
0:37:03 > 0:37:06then using momentum to pivot onto the next,
0:37:06 > 0:37:10penguins barely use their leg muscles at all.
0:37:13 > 0:37:16So, it looks very inefficient but it can actually
0:37:16 > 0:37:21recover 80% of the energy it's using for each stride for the next one.
0:37:21 > 0:37:25So, it turns out that it's the best way to get about.
0:37:28 > 0:37:34If you aren't built to walk, then waddling isn't a bad solution.
0:37:36 > 0:37:40Imagine this is a penguin waddling.
0:37:40 > 0:37:41METRONOME CLICKS
0:37:41 > 0:37:46Rather than moving forward and using energy to pick up legs and feet,
0:37:46 > 0:37:50the penguin swings from side to side.
0:37:50 > 0:37:54Each swing stores up energy for the next swing.
0:37:54 > 0:38:00That way, a penguin can use momentum and gain ground and waddling
0:38:00 > 0:38:05might not be the most elegant way of moving around but a penguin's
0:38:05 > 0:38:10ability to waddle allows it to survive under the water and on land.
0:38:13 > 0:38:16And penguins aren't the only animal
0:38:16 > 0:38:20whose iconic movement hides a surprising secret.
0:38:33 > 0:38:38Although summer days in the outback can soar past 50 degrees...
0:38:40 > 0:38:45..you'll never see a hot-and-bothered-looking koala.
0:38:46 > 0:38:50Scientists have recently discovered that koalas'
0:38:50 > 0:38:56iconic tree-cuddling holds the key to survival in the baking heat.
0:38:58 > 0:39:00While the air temperature sizzles,
0:39:00 > 0:39:05the bark of a tree can be up to nine degrees cooler.
0:39:07 > 0:39:11By pressing the thinner fur of their bellies against the bark,
0:39:11 > 0:39:14a koala can lose some excess heat
0:39:14 > 0:39:18and keep its core temperature in check.
0:39:29 > 0:39:32We find weird and wonderful movements
0:39:32 > 0:39:35incredibly appealing.
0:39:35 > 0:39:37But for the animals,
0:39:37 > 0:39:40they're perfect adaptations
0:39:40 > 0:39:42to get them around a problem.
0:39:45 > 0:39:48A dexterous trunk...
0:39:50 > 0:39:53..a comic waddle...
0:39:53 > 0:39:59or a cuddle is key to success.
0:40:02 > 0:40:08But it's not just visual clues that trigger our cute response.
0:40:08 > 0:40:12Sounds can be just as powerful.
0:40:14 > 0:40:18This is Eli, he's a five-year-old chimpanzee
0:40:18 > 0:40:22and it is incredibly easy to see why our species
0:40:22 > 0:40:25has such a strong affinity for his species.
0:40:25 > 0:40:27I mean, look, we could be brothers.
0:40:27 > 0:40:29HE IMPERSONATES CHIMPANZEE
0:40:29 > 0:40:32Well, brothers from another mother.
0:40:40 > 0:40:44The mannerisms and expressions of apes
0:40:44 > 0:40:47make them a firm favourite.
0:40:52 > 0:40:54We are so alike.
0:40:56 > 0:40:59And there's one particular behaviour,
0:40:59 > 0:41:01a sound that we share,
0:41:01 > 0:41:05that's recently piqued expert interest.
0:41:10 > 0:41:14A troop of chimpanzees is just like any human family.
0:41:16 > 0:41:17They hang out,
0:41:17 > 0:41:21play and they laugh.
0:41:25 > 0:41:28HE IMPERSONATES CHIMPANZEE
0:41:28 > 0:41:33Eli is still a child and like any child,
0:41:33 > 0:41:37he shows his enjoyment and his personality through laughter.
0:41:40 > 0:41:41Are you tickly?
0:41:41 > 0:41:43Are you tickly? You are.
0:41:43 > 0:41:45ELI LAUGHS
0:41:45 > 0:41:48If you get the right spot, he really, really enjoys it.
0:41:48 > 0:41:50Look at you, look at that face.
0:41:50 > 0:41:55That's good. I've got you, see?
0:41:56 > 0:41:59It's really infectious, you see Eli laughing
0:41:59 > 0:42:01and it makes you want to laugh.
0:42:01 > 0:42:08And recently, scientists started to take laughter seriously...
0:42:12 > 0:42:16..wondering whether the similarity between the sounds we make
0:42:16 > 0:42:20might tell us more about our own evolution.
0:42:20 > 0:42:22We were interested
0:42:22 > 0:42:25whether we share our emotional
0:42:25 > 0:42:28behaviours with apes
0:42:28 > 0:42:33and there were some very interesting cues that indicated that
0:42:33 > 0:42:36laughter may have deep biological roots.
0:42:36 > 0:42:43In the name of science, Marina started tickling.
0:42:43 > 0:42:45She collected footage from chimps,
0:42:45 > 0:42:48orang-utans...
0:42:48 > 0:42:50and gorillas.
0:42:53 > 0:42:58We recorded these sounds and used these sounds in order to
0:42:58 > 0:43:01conduct a systematic acoustic analysis.
0:43:01 > 0:43:05When Marina gathered all the giggles together,
0:43:05 > 0:43:09a pattern began to emerge.
0:43:11 > 0:43:14The apes furthest away from us on the evolutionary tree,
0:43:14 > 0:43:15orang-utans and gorillas,
0:43:15 > 0:43:18made a very simple sound when tickled.
0:43:20 > 0:43:23But tickling our closer cousins, chimps,
0:43:23 > 0:43:27produced a more complex laugh sound.
0:43:28 > 0:43:32Due to this matching, we could conclude that these vocalisations
0:43:32 > 0:43:36that we examined were laugh vocalisations and that apes produced
0:43:36 > 0:43:42laughter and that laughter is at least 13 to 16 million years old.
0:43:45 > 0:43:49Bonobos, who are the most similar to us genetically,
0:43:49 > 0:43:53also had the most human-like laugh.
0:43:55 > 0:44:00Marina's findings show that laughter has evolved with us.
0:44:02 > 0:44:03HE IMPERSONATES CHIMPANZEE
0:44:03 > 0:44:06You can see when Eli laughs, he laughs like this...
0:44:06 > 0:44:07ho-ho-ha-ha...
0:44:07 > 0:44:10so he's using his outward breath and his inward breath.
0:44:12 > 0:44:15ELI LAUGHS
0:44:15 > 0:44:16You see what's happening,
0:44:16 > 0:44:20when I laugh it's on the outward breath - ha, ha, ha, ha.
0:44:20 > 0:44:23And that's something that we do subconsciously,
0:44:23 > 0:44:26but it's because we can control our breathing
0:44:26 > 0:44:28and it's our human ability to control our breathing
0:44:28 > 0:44:31that has led us to develop speech,
0:44:31 > 0:44:33so isn't it fantastic to think
0:44:33 > 0:44:35that we might have laughter to thank for that?
0:44:35 > 0:44:36HE IMPERSONATES CHIMP
0:44:36 > 0:44:39You agree, it is fantastic.
0:44:39 > 0:44:44'We find a chimp's laughter so appealing because we recognise it.
0:44:44 > 0:44:48'It's a sound we associate with pleasure.'
0:44:48 > 0:44:50ELI LAUGHS
0:44:52 > 0:44:57But sometimes more unexpected sounds grab our attention.
0:44:57 > 0:45:00RAIN FROG SQUEAKS
0:45:00 > 0:45:03Like this desert rain frog.
0:45:03 > 0:45:05Squeaking viral sensation.
0:45:05 > 0:45:10RAIN FROG SQUEAKS
0:45:10 > 0:45:1311 million hits and counting.
0:45:13 > 0:45:16It sounds like a dog toy,
0:45:16 > 0:45:17but actually this...
0:45:17 > 0:45:18RAIN FROG SQUEAKS
0:45:18 > 0:45:24..is the sonorous war cry of a very angry frog.
0:45:24 > 0:45:27RAIN FROG SQUEAKS
0:45:27 > 0:45:29Ferocious.
0:45:34 > 0:45:39And there's another animal who became an internet celebrity
0:45:39 > 0:45:42by making an even more surprising sound.
0:45:43 > 0:45:45HUMMINGBIRD SNORES
0:45:45 > 0:45:47A scientist in Peru...
0:45:47 > 0:45:49HUMMINGBIRD SNORES
0:45:49 > 0:45:50..captured this
0:45:50 > 0:45:55escaping from the tiny body of a sleeping hummingbird.
0:45:55 > 0:45:58HUMMINGBIRD SNORES
0:45:58 > 0:45:59A high-pitched...
0:45:59 > 0:46:01HUMMINGBIRD SNORES
0:46:01 > 0:46:04..but unmistakable snore.
0:46:06 > 0:46:10Hummingbirds are loved for their beauty and speed
0:46:10 > 0:46:15but this one was behaving a little bit like a human.
0:46:15 > 0:46:20The perfect cute response trigger.
0:46:20 > 0:46:23But was the online fame deserved?
0:46:23 > 0:46:26Is this bird really snoring?
0:46:34 > 0:46:39Even before the snore, hummingbirds fascinated scientists.
0:46:42 > 0:46:46From the day I first laid eyes on them,
0:46:46 > 0:46:50they appealed to me because they are just such unique creatures.
0:46:52 > 0:46:55They are the only true species of bird
0:46:55 > 0:46:58that actually can hover for sustained amounts of time.
0:46:59 > 0:47:03The smaller species will flap their wings about 60 times a second.
0:47:03 > 0:47:06Try to move your arm that fast, it's pretty difficult.
0:47:08 > 0:47:12The smallest hummingbirds weigh as little as 2g,
0:47:12 > 0:47:13which is less than a paper clip.
0:47:13 > 0:47:17HUMMING
0:47:17 > 0:47:22This rapid movement is a lot to ask for such a tiny body.
0:47:22 > 0:47:25It uses up so much energy,
0:47:25 > 0:47:30that a hummingbird needs to feed almost constantly.
0:47:36 > 0:47:41A sugar-rich hit of nectar every 15 minutes.
0:47:45 > 0:47:48During the day, regularly sipping nectar
0:47:48 > 0:47:52gives a hummingbird enough energy to survive.
0:47:56 > 0:48:00But they can't do this for a full 24 hours.
0:48:00 > 0:48:02They need rest.
0:48:12 > 0:48:15The sun's about to set and fairly soon,
0:48:15 > 0:48:17I'm going to want to go to sleep.
0:48:17 > 0:48:20That's not a problem because through today, I've taken on board
0:48:20 > 0:48:23more than enough calories to see me through the night,
0:48:23 > 0:48:27but a hummingbird has to feed every 30 minutes or so
0:48:27 > 0:48:29even when it's not flying.
0:48:29 > 0:48:32To sleep through the night without feeding
0:48:32 > 0:48:34could be incredibly dangerous,
0:48:34 > 0:48:38so, the hummingbird is left with one drastic option
0:48:38 > 0:48:41and that is to shut down entirely.
0:48:44 > 0:48:50Their heart rate drops from 1,000 beats a minute to just 50.
0:48:51 > 0:48:56Their breathing becomes almost non-existent...
0:48:58 > 0:49:01..using just enough energy to stay alive.
0:49:02 > 0:49:05It's called torpor...
0:49:05 > 0:49:11and scientists like Don are only now beginning to understand it.
0:49:12 > 0:49:16Most of what we know about torpor's been learned in the laboratory.
0:49:16 > 0:49:18We take a hummingbird
0:49:18 > 0:49:23and we will put it in what we call a metabolism chamber.
0:49:23 > 0:49:27We measure the oxygen content of the air.
0:49:29 > 0:49:32If their oxygen consumption gets really, really low
0:49:32 > 0:49:35so that it's even difficult to measure,
0:49:35 > 0:49:38then we know that the bird is in torpor.
0:49:40 > 0:49:42HUMMINGBIRD SNORES
0:49:42 > 0:49:46The internet footage is actually from an experiment
0:49:46 > 0:49:48very similar to Don's.
0:49:50 > 0:49:55The hummingbird has spent the night in torpor to save energy.
0:49:58 > 0:50:01But that doesn't explain the snoring.
0:50:03 > 0:50:05Sleep and torpor are very different.
0:50:05 > 0:50:08When we go to sleep, our lungs are still working,
0:50:08 > 0:50:10our hearts are still beating away
0:50:10 > 0:50:12and we can wake up really quite quickly,
0:50:12 > 0:50:14but for a hummingbird to come round from torpor,
0:50:14 > 0:50:17it has to kick-start its entire body,
0:50:17 > 0:50:20it has to get its breathing and its heart rate back up to speed.
0:50:21 > 0:50:25Which is exactly what this hummingbird's doing.
0:50:26 > 0:50:30The sound is actually a by-product of them gasping for oxygen...
0:50:32 > 0:50:35..much like air rushing across a vocal chord's would.
0:50:36 > 0:50:40Coming to with a snore of sorts.
0:50:41 > 0:50:47The very sweet side-effect of a fascinating survival strategy.
0:50:48 > 0:50:52RAIN FROG SQUEAKS
0:50:52 > 0:50:58We associate high-frequency sounds with surprise, comedy...
0:50:58 > 0:51:00PENGUIN SCREECHES
0:51:00 > 0:51:05..and coming from such unexpected animals, they're pretty funny.
0:51:05 > 0:51:07PENGUIN SCREECHES
0:51:13 > 0:51:20But lower frequencies are proven to be soothing, calming -
0:51:20 > 0:51:24opposite but equally powerful effects.
0:51:24 > 0:51:28CAT PURRS
0:51:28 > 0:51:33And it's this soothing quality that has brought us closer
0:51:33 > 0:51:36to one species than any other.
0:51:36 > 0:51:37CAT PURRS
0:51:39 > 0:51:45This is an animal that we have an especially close relationship with.
0:51:47 > 0:51:49Cats have lived side by side with us,
0:51:49 > 0:51:54sharing our homes for thousands of years.
0:51:54 > 0:52:01There are an estimated 200 million pet cats worldwide
0:52:01 > 0:52:05and over two million internet cat videos.
0:52:05 > 0:52:09I think it's fair to say we're obsessed.
0:52:10 > 0:52:13They tick all the boxes.
0:52:13 > 0:52:16Big forward-facing eyes,
0:52:16 > 0:52:18furry,
0:52:18 > 0:52:21elegant movement...
0:52:21 > 0:52:25but the greatest appeal lies in the noise they make.
0:52:25 > 0:52:29CAT PURRS
0:52:31 > 0:52:34I'm not much of a pet cat person.
0:52:34 > 0:52:38Sahara here is much more my kind of feline.
0:52:38 > 0:52:44She is an eight-year-old cheetah and she is absolutely beautiful,
0:52:44 > 0:52:49but she's also a very powerful predator.
0:52:49 > 0:52:53So, I wouldn't quite want her sitting up on my lap
0:52:53 > 0:52:59but just like a domestic cat, she also purrs.
0:52:59 > 0:53:01SAHARA PURRS
0:53:01 > 0:53:04Purring is a way of communicating.
0:53:04 > 0:53:09It's a way of a cheetah saying, "I'm OK, I'm relaxed."
0:53:12 > 0:53:14And they do it when they're grooming
0:53:14 > 0:53:17and they do it when they're with their cubs.
0:53:20 > 0:53:22SAHARA PURRS
0:53:24 > 0:53:26Many cat species purr,
0:53:26 > 0:53:29cheetah to moggy.
0:53:31 > 0:53:36It's made when the muscles in the throat contract and relax...
0:53:36 > 0:53:38CATS PURR
0:53:38 > 0:53:41..making air vibrate past the voice box.
0:53:44 > 0:53:48A purring cat is a happy cat.
0:53:48 > 0:53:52But they'll also purr when injured or unwell
0:53:52 > 0:53:55and this is where it gets interesting,
0:53:55 > 0:53:59because purring uses energy...
0:54:00 > 0:54:05..and why would a poorly cat waste precious resources?
0:54:05 > 0:54:07SAHARA PURRS
0:54:07 > 0:54:10Her purr really is incredible.
0:54:10 > 0:54:13You can't just hear it, you can actually feel it thrumming
0:54:13 > 0:54:17and vibrating through her whole body
0:54:17 > 0:54:19and new research has suggested that purring
0:54:19 > 0:54:22might have some hidden health benefits.
0:54:24 > 0:54:29The frequency of the purr is very similar to the sound waves
0:54:29 > 0:54:34that doctors use to help repair muscle and bone, so,
0:54:34 > 0:54:39while she's resting, she could very well be giving her body a once-over.
0:54:40 > 0:54:42Restoration.
0:54:42 > 0:54:45SAHARA PURRS
0:54:49 > 0:54:56But, unfortunately for us, a purr is not all positive.
0:54:56 > 0:55:01Cats were first domesticated over 9,000 years ago...
0:55:02 > 0:55:07..which means they've had plenty of time to get to know us.
0:55:07 > 0:55:11Perhaps too much time.
0:55:12 > 0:55:18Recent research discovered a second type of purr that cats use,
0:55:18 > 0:55:23not to heal, but to get their own way.
0:55:27 > 0:55:31It's louder and more urgent
0:55:31 > 0:55:36and the masterstroke is that extra-high pitch...
0:55:36 > 0:55:38CAT PURRS WITH HIGH PITCH
0:55:38 > 0:55:42..a peak of 600 Hz...
0:55:43 > 0:55:49..which mimics the frequency of a human baby's wail.
0:55:49 > 0:55:52CAT PURRS WITH HIGH PITCH
0:55:53 > 0:56:00Cats have perfected a purr that we find impossible to ignore...
0:56:02 > 0:56:07..using it when they want to be fed, or to get a stroke.
0:56:09 > 0:56:12It's psychological manipulation.
0:56:14 > 0:56:18We are powerless to the purr.
0:56:18 > 0:56:21Cunning and incredibly clever.
0:56:21 > 0:56:24SAHARA PURRS
0:56:26 > 0:56:30Whether it's a soothing purr...
0:56:31 > 0:56:33..a massive head...
0:56:33 > 0:56:35HUMMINGBIRD SNORES
0:56:35 > 0:56:38..or a sweet little snore...
0:56:40 > 0:56:47..the reasons we love certain animals are as diverse and different
0:56:47 > 0:56:50as the animals themselves.
0:56:50 > 0:56:53Every comic movement,
0:56:53 > 0:56:55oversized feature,
0:56:55 > 0:56:59and wonderful sound
0:56:59 > 0:57:03tells a story of evolution
0:57:03 > 0:57:08and survival.
0:57:08 > 0:57:11Extraordinary lives need extraordinary features.
0:57:11 > 0:57:14It's what makes these animals successful.
0:57:14 > 0:57:17But the way that we are drawn to them,
0:57:17 > 0:57:22our cute response, really is just a bizarre accident of our biology.
0:57:22 > 0:57:26The way they look, the way they sound, the way they behave,
0:57:26 > 0:57:30their biology, that's what's really interesting.