0:00:01 > 0:00:05Our favourite pets are among the most amazing animals on Earth.
0:00:07 > 0:00:11They've taken to a domestic life and become our perfect companions.
0:00:13 > 0:00:16But their natural instincts remain intact.
0:00:19 > 0:00:21They may have been tamed for thousands of years...
0:00:24 > 0:00:28..but they were wild animals for millions more.
0:00:33 > 0:00:35Some were smart and supreme predators.
0:00:37 > 0:00:40Others were alert and fleet-footed prey.
0:00:47 > 0:00:51Whatever their origins, they now live happily among us.
0:00:57 > 0:01:01But behaviour that feels familiar was born in the wild.
0:01:04 > 0:01:09Take a closer look, and discover the true animal sharing your home.
0:01:11 > 0:01:14A creature just a wing-beat from the wild.
0:01:29 > 0:01:31We think we understand our pets.
0:01:31 > 0:01:32Cute and adored,
0:01:32 > 0:01:36they seem far removed from their wild living relatives.
0:01:37 > 0:01:39We love to watch them play.
0:01:45 > 0:01:49But there's more to their games than meets the eye.
0:01:49 > 0:01:52These puppies are still training for life as a predator.
0:01:58 > 0:02:01As they play, they rehearse the same rules
0:02:01 > 0:02:04that enable wolves to hunt as an organised pack.
0:02:10 > 0:02:13They must take care - even at seven weeks,
0:02:13 > 0:02:16these cockerpoos are armed with 28 needle-sharp teeth.
0:02:22 > 0:02:26Dominant puppies choose to fight weaker ones, but no-one gets hurt.
0:02:26 > 0:02:30Puppies that ignore the rules are soon ostracised by the others.
0:02:35 > 0:02:37They must learn to restrain their bite.
0:02:39 > 0:02:41If a puppy shows its vulnerable belly,
0:02:41 > 0:02:43then it's a signal to take time out.
0:02:46 > 0:02:51All else is fair game - a chance to let rip and practice killer holds.
0:02:53 > 0:02:55And death shakes too.
0:02:59 > 0:03:02They need teamwork to bring down large prey,
0:03:02 > 0:03:04even if, for now, it's just a cushion.
0:03:28 > 0:03:31They may have been domesticated for 30,000 years,
0:03:31 > 0:03:34but play still prepares them for life in the wild.
0:03:37 > 0:03:40But their games have modern relevance too.
0:03:42 > 0:03:45HOWLING
0:03:55 > 0:04:01Dogs, more than any of our pets, must learn to rub along together.
0:04:01 > 0:04:05They're often forced into situations no wild animal would tolerate.
0:04:11 > 0:04:16In New York, dog walkers exercise many different breeds at a time.
0:04:16 > 0:04:19It's the closest the dogs get to pack life.
0:04:22 > 0:04:26But, unlike hunting wolves, these dogs are completely unrelated.
0:04:33 > 0:04:36Recent research in a New York dog park
0:04:36 > 0:04:39revealed the full complexity of their social interactions.
0:04:42 > 0:04:46They first become reacquainted using their celebrated sense of smell -
0:04:46 > 0:04:49up to 100,000 times more sensitive than our own.
0:04:57 > 0:05:00By sniffing scent glands on another dog's bottom,
0:05:00 > 0:05:02they check its identity,
0:05:02 > 0:05:05as well as its diet, health and emotional state.
0:05:14 > 0:05:18Once everyone's formally introduced, the play begins.
0:05:21 > 0:05:22It may be boisterous,
0:05:22 > 0:05:25but the wild rules they practised as pups
0:05:25 > 0:05:27stop things getting out of hand.
0:05:33 > 0:05:35Opting out is perfectly acceptable,
0:05:35 > 0:05:38and for small dogs, not unreasonable!
0:05:44 > 0:05:48Toy breeds must feel at a distinct disadvantage.
0:05:52 > 0:05:55But this Boston terrier's up for the challenge,
0:05:55 > 0:05:56no matter how great!
0:05:58 > 0:06:00He knows the rules.
0:06:01 > 0:06:04Exchange doggy bows, and he won't get hurt.
0:06:10 > 0:06:12The "play bow" lets him have fun
0:06:12 > 0:06:14with a Great Dane three times his size.
0:06:25 > 0:06:28It's an invitation every dog understands.
0:06:44 > 0:06:46It's quite OK to refuse, and anyway,
0:06:46 > 0:06:48there are always others up for a game.
0:07:01 > 0:07:03Leaping together establishes who's biggest.
0:07:03 > 0:07:05It's another way to test each other.
0:07:10 > 0:07:12But, size isn't everything -
0:07:12 > 0:07:14it's about confidence and posturing too,
0:07:14 > 0:07:16as this belligerent bulldog knows.
0:07:24 > 0:07:27The young Labrador uses a trick she learnt in play -
0:07:27 > 0:07:30rolling over and exposing her vulnerable belly.
0:07:39 > 0:07:42The bulldog may be pumped up with aggression,
0:07:42 > 0:07:45but the Lab's submissive posture takes the fight right out of him.
0:07:53 > 0:07:55Playing together as puppies
0:07:55 > 0:07:57allows dogs to understand the rules of the park.
0:08:04 > 0:08:07Pets that are prey play different games.
0:08:10 > 0:08:13For Russian hamsters, it's all about running.
0:08:15 > 0:08:18In nature, they cover six miles a night,
0:08:18 > 0:08:21and they often have to outrun predators.
0:08:21 > 0:08:22In captivity,
0:08:22 > 0:08:25they can cover the same distance by running on the spot.
0:08:27 > 0:08:30And it seems they do it for fun!
0:08:30 > 0:08:33When scientists placed a wheel in the wild,
0:08:33 > 0:08:36mice took to it just as keenly as this enthusiastic hamster.
0:08:44 > 0:08:48Like human athletes, exercise creates a rush of endorphins.
0:08:48 > 0:08:50He experiences a runner's high.
0:08:56 > 0:08:59At full pelt he reaches 600 strides a minute -
0:08:59 > 0:09:02four times more than the fastest racehorse.
0:09:10 > 0:09:12Moving X-ray shows that, unlike horses,
0:09:12 > 0:09:16even when flat out he always keeps one foot on the ground.
0:09:20 > 0:09:22He may be fast,
0:09:22 > 0:09:25but nothing improves performance like a bit of competition.
0:10:09 > 0:10:13Hamsters aren't the most sociable of creatures.
0:10:13 > 0:10:15It seems they're bad losers too.
0:10:24 > 0:10:27The loser settles for the consolation prize
0:10:27 > 0:10:29while the winner goes for gold.
0:10:34 > 0:10:38Like wild hamsters, he mostly runs at dawn and dusk.
0:10:38 > 0:10:40But, when the time is right,
0:10:40 > 0:10:42enthusiasm can get the better of him.
0:10:45 > 0:10:49His racing instinct is so engrained, little puts him off.
0:11:06 > 0:11:10The quest for speed, once vital for survival, has become a game.
0:11:17 > 0:11:21One that also tests his acrobatic skills.
0:11:36 > 0:11:39But, perfection is so hard to achieve!
0:11:50 > 0:11:52Time flies when you're having fun!
0:12:18 > 0:12:22And, while he's been enjoying himself, so has the other hamster!
0:12:33 > 0:12:37Kittens also use play to practise their wild skills.
0:12:43 > 0:12:46In nature, they are solitary hunters,
0:12:46 > 0:12:48and their games prepare them for a life alone.
0:12:57 > 0:13:00They have some impressive abilities to perfect.
0:13:12 > 0:13:15Their eyes are already reacting to the slightest movement,
0:13:15 > 0:13:18but their reflexes still need sharpening.
0:13:25 > 0:13:27Leg muscles must be exercised too.
0:13:27 > 0:13:30He'll soon jump seven times his height.
0:13:35 > 0:13:39Claws and paws expand as he practices grasping prey.
0:13:49 > 0:13:55His other qualities include a spine that can twist 180 degrees,
0:13:55 > 0:13:58and a tail that acts as a counterbalance
0:13:58 > 0:14:00so he famously lands on his feet.
0:14:02 > 0:14:04He even has built-in shock absorbers!
0:14:11 > 0:14:16It was these skills that made wild African cats useful pest controllers
0:14:16 > 0:14:19when they moved in with the first farmers 10,000 years ago.
0:14:30 > 0:14:33After all these years, little has changed.
0:14:42 > 0:14:45These two-month old Bengal kittens are still practising
0:14:45 > 0:14:47for a life as independent hunters.
0:14:53 > 0:14:55In the wild, in another three months,
0:14:55 > 0:14:57they would be killing their own food.
0:15:02 > 0:15:06These kittens will soon be separated and begin life in their new homes.
0:15:06 > 0:15:08But, whoever's pet they become,
0:15:08 > 0:15:11they'll already be fully trained as a predator.
0:15:19 > 0:15:22Prey animals, like these five-week-old lop-eared rabbits,
0:15:22 > 0:15:25also practice their survival skills through play.
0:15:29 > 0:15:31For a rabbit, it's all about hopping!
0:15:39 > 0:15:43These leaps may be defensive, but learning is clearly great fun.
0:16:12 > 0:16:14Their mother's natural instincts
0:16:14 > 0:16:17compel her to dig a bolt hole in case of predators.
0:16:26 > 0:16:30Some pet rabbits get the chance to test out these games in the wild.
0:16:30 > 0:16:34To find them, we must go "down the rabbit hole" into another world.
0:16:44 > 0:16:47This rabbit wonderland is on an island in Japan.
0:16:51 > 0:16:53It even has a white rabbit,
0:16:53 > 0:16:57a descendant of pet rabbits released here 40 years ago.
0:17:11 > 0:17:12They still come in many colours,
0:17:12 > 0:17:15though most have reverted to the brown wild form.
0:17:20 > 0:17:25Because they breed like, well, like rabbits, there are hundreds of them.
0:17:39 > 0:17:42They are free to express their wild instincts,
0:17:42 > 0:17:43but they have stayed tame,
0:17:43 > 0:17:46and are treated like pets by adoring visitors.
0:17:52 > 0:17:55By adapting a pose they use to spot predators,
0:17:55 > 0:17:56they've even learnt to beg.
0:18:02 > 0:18:07But no self-respecting wild rabbit would contemplate standing so close.
0:18:13 > 0:18:16While most rush to greet the visitors,
0:18:16 > 0:18:18the white rabbit is always late.
0:18:21 > 0:18:23White rabbits are legendary across Asia,
0:18:23 > 0:18:27and its image is thought to be found on the face of the moon.
0:18:27 > 0:18:30So he always gets special treatment.
0:18:40 > 0:18:42The rabbits may act like pets,
0:18:42 > 0:18:45but their natural instincts have resurfaced.
0:18:50 > 0:18:53As well as living in a warren like wild rabbits,
0:18:53 > 0:18:55some take up sentry duty.
0:19:00 > 0:19:03Her ears turn independently to pinpoint any sounds.
0:19:03 > 0:19:05CROW CAWS
0:19:08 > 0:19:12And she has eyes that can scan nearly 360 degrees.
0:19:17 > 0:19:21Grazing rabbits rely on sentries to warn them of danger.
0:19:27 > 0:19:31The alarm, when it comes, is understood by all...
0:19:34 > 0:19:36..or nearly all!
0:19:40 > 0:19:43Here, bolt holes are used in earnest.
0:19:45 > 0:19:49But this older and wiser rabbit knows to ignore false alarms.
0:19:49 > 0:19:51Foxes or eagles aren't found here,
0:19:51 > 0:19:54and a crow is hardly in their league.
0:19:59 > 0:20:03As life returns to normal, the rabbits do what they do best.
0:20:14 > 0:20:16But this is serious leaping.
0:20:16 > 0:20:19Their back legs are their greatest asset,
0:20:19 > 0:20:22and a target for aggressive rivals.
0:20:33 > 0:20:38As they jump away, their kick packs a defensive punch.
0:20:46 > 0:20:49Females leap to ward off over-amorous males.
0:20:54 > 0:20:58And bucks compete in the high jump to prove who's best.
0:21:01 > 0:21:04On Rabbit Island, the lessons learnt as playful youngsters
0:21:04 > 0:21:06show their true value.
0:21:11 > 0:21:14For all our pets, the time spent with their mother
0:21:14 > 0:21:17is the most important of their lives.
0:21:17 > 0:21:21It's an opportunity to nurture their wilder side before humans intervene.
0:21:24 > 0:21:27Kittens learn to use a designated nipple
0:21:27 > 0:21:30that they mark with their own distinct scent.
0:21:30 > 0:21:32In this way, they keep squabbling to a minimum
0:21:32 > 0:21:34and themselves to themselves.
0:21:42 > 0:21:45They may be showing the first signs of independence,
0:21:45 > 0:21:48but at this age, they depend on their mother for everything.
0:21:54 > 0:21:57Thermal imagery shows that even her body warmth
0:21:57 > 0:21:59is vital for their survival.
0:22:02 > 0:22:0510-day old kittens can't regulate their temperature,
0:22:05 > 0:22:08so she keeps them nestled in her fur.
0:22:14 > 0:22:17Unseen, a kitten starts to stray.
0:22:22 > 0:22:26Although his eyes have only just opened, he still can't see clearly.
0:22:29 > 0:22:32And away from his mother, he's already losing heat.
0:22:45 > 0:22:48KITTEN MEWS
0:22:48 > 0:22:50His instinct is to cry.
0:22:58 > 0:23:02And it's a call no mother can ignore.
0:23:17 > 0:23:19Being carried by the scruff
0:23:19 > 0:23:21triggers an instinct that stops him struggling,
0:23:21 > 0:23:24or making a sound that could attract predators.
0:23:27 > 0:23:29A mother with young kittens
0:23:29 > 0:23:33instinctively uses this technique whenever she changes dens.
0:23:36 > 0:23:40Moving home is one thing, getting enough to eat is quite another.
0:23:42 > 0:23:49She lives on Cat Island in Japan, a moggie paradise full of feral cats.
0:23:59 > 0:24:01They were imported to catch vermin
0:24:01 > 0:24:04when the island was a centre for the silkworm industry.
0:24:04 > 0:24:07They now survive by scavenging from fishermen.
0:24:10 > 0:24:14Their kittens are brought up in the perfect playground.
0:24:43 > 0:24:45But their busy mums have to juggle childcare
0:24:45 > 0:24:48with the important job of getting a meal,
0:24:48 > 0:24:51and their chance comes just once a day.
0:24:54 > 0:24:56The boats are returning, laden with fish.
0:25:04 > 0:25:09Kittens more than a few weeks old can happily be left alone.
0:25:18 > 0:25:21They are old enough to stay warm and keep out of trouble
0:25:21 > 0:25:23as their mother searches for a meal.
0:25:27 > 0:25:30But the mother with the new kitten faces a problem.
0:25:30 > 0:25:33At 10 days old, he's too young to be left on his own.
0:25:38 > 0:25:40So, mum's left holding the baby
0:25:40 > 0:25:43while the other cats enjoy their fish supper.
0:25:48 > 0:25:50Squabbles over food are inevitable.
0:25:58 > 0:26:00But soon, everyone gets a slice of the action,
0:26:00 > 0:26:03except for the new, and now very hungry, mother.
0:26:07 > 0:26:09She looks for a possible solution.
0:26:17 > 0:26:21She squeezes her eyes - a greeting that most cat owners will recognise.
0:26:27 > 0:26:29The new arrival grooms the baby...
0:26:34 > 0:26:37..then turns her attention to the mother.
0:26:37 > 0:26:39It's her way of offering to babysit.
0:26:41 > 0:26:44The mother doesn't wait to see if she'll change her mind!
0:26:50 > 0:26:54Baby-sitting is natural among cats, especially between related females.
0:26:54 > 0:26:56She's probably her sister.
0:26:59 > 0:27:02Meanwhile, mum searches for scraps left by the other cats.
0:27:06 > 0:27:10It's a chance for her childminder to enjoy time with the baby,
0:27:10 > 0:27:12but she's clearly not sure what to do.
0:27:18 > 0:27:21The young kitten has reawakened her urge to play,
0:27:21 > 0:27:23even though he's far too young for games.
0:27:45 > 0:27:48Then every baby-sitter's nightmare!
0:27:57 > 0:27:59She checks she hasn't been seen,
0:27:59 > 0:28:02but the mother's focused on gaining a meal.
0:28:19 > 0:28:21Desperate times call for desperate measures.
0:28:27 > 0:28:30The mother senses something's wrong.
0:28:30 > 0:28:34But then, in the nick of time, success!
0:28:42 > 0:28:46Mum might try a less playful baby-sitter next time!
0:28:52 > 0:28:54It's the cat's playful nature,
0:28:54 > 0:28:57as well as their independence of mind, that helps make them
0:28:57 > 0:29:00the world's most popular pet,
0:29:00 > 0:29:03beating dogs, paws down.
0:29:06 > 0:29:09Our third most cherished pet is equally playful.
0:29:11 > 0:29:14The common parakeet, better known as the budgerigar,
0:29:14 > 0:29:17is found naturally in the outback of Australia.
0:29:20 > 0:29:21They are social birds,
0:29:21 > 0:29:25occurring in huge flocks as they search for both food and water.
0:29:33 > 0:29:36They are highly intelligent and, even in the heart of the flock,
0:29:36 > 0:29:38families stick together.
0:29:45 > 0:29:48It's this friendly nature that, for the last 150 years,
0:29:48 > 0:29:51has made them such perfect human companions.
0:29:53 > 0:29:56In homes, these intensely social birds
0:29:56 > 0:29:58are hard-wired to seek out company.
0:30:03 > 0:30:06BIRD TWEETS AND CHATTERS
0:30:06 > 0:30:11Who's a pretty bird? Disco, who's a pretty bird? Baby.
0:30:11 > 0:30:14A mirror provides a temporary companion -
0:30:14 > 0:30:17he doesn't see it as a reflection of himself,
0:30:17 > 0:30:18more a buddy who comes and goes.
0:30:25 > 0:30:28But, when he wants some real quality time,
0:30:28 > 0:30:30he's learnt some playful tricks to get noticed.
0:30:33 > 0:30:36BIRD WHISTLES
0:30:36 > 0:30:39CUP RATTLES
0:30:46 > 0:30:49BALL CRASHES TO THE FLOOR
0:30:49 > 0:30:52I see you over there! Baby bird, baby bird.
0:30:52 > 0:30:54Come on, baby bird!
0:30:54 > 0:30:56What are you doing, Disco? What did mama say?
0:30:56 > 0:30:59Are you dancing? What is it, Disco?
0:30:59 > 0:31:01Yah? Come on over.
0:31:01 > 0:31:03Come on out.
0:31:03 > 0:31:05Having captured his owner's attention,
0:31:05 > 0:31:07he can practice another skill.
0:31:07 > 0:31:11It's not easy being green.
0:31:11 > 0:31:15BIRD: It's not easy being green. It's not easy being green.
0:31:15 > 0:31:18Mimicry isn't as unnatural as it seems.
0:31:18 > 0:31:20Wild parakeets mimic each other,
0:31:20 > 0:31:24and each family learns their own distinct calls.
0:31:24 > 0:31:26Never shake a baby bird.
0:31:26 > 0:31:28That would surely be absurd.
0:31:28 > 0:31:30Never shake a baby bird.
0:31:30 > 0:31:32That would surely be absurd.
0:31:32 > 0:31:35This budgie is just doing what he would do in the flock.
0:31:39 > 0:31:41Is that a parakeet. What is it?
0:31:41 > 0:31:42A green and yellow bird that talks?
0:31:42 > 0:31:44That's not important right now.
0:31:44 > 0:31:49Even having a name may not be as unnatural as it seems.
0:31:49 > 0:31:51I'm Disco and I know it.
0:31:51 > 0:31:53I'm Disco and I know it.
0:31:53 > 0:31:56I am not a crook. My name is Disco.
0:31:57 > 0:32:00Wild parrots have been shown to assign special calls
0:32:00 > 0:32:04to name their offspring, just as we name our own pet budgies.
0:32:04 > 0:32:07Baby bird. Disco baby bird.
0:32:07 > 0:32:08Keep it bird.
0:32:08 > 0:32:11In turn, young parrots learn these names
0:32:11 > 0:32:14and use them to introduce themselves.
0:32:15 > 0:32:18I am not a crook. My name is Disco.
0:32:18 > 0:32:22This extraordinary ability may mean that Disco
0:32:22 > 0:32:24has a sense of his own identity.
0:32:24 > 0:32:26It certainly seems so at times.
0:32:27 > 0:32:29Disco baby.
0:32:30 > 0:32:32Talking is now a game,
0:32:32 > 0:32:35a way to express wild behaviour in the confines of his home.
0:32:38 > 0:32:40A cat. Meow, meow.
0:32:40 > 0:32:42Give me a kiss.
0:32:43 > 0:32:45I can has cheeseburger.
0:32:47 > 0:32:49Aren't you a little short for a stormtrooper?
0:32:49 > 0:32:50Disco.
0:32:50 > 0:32:53I used to be a spy, then a parakeet.
0:32:53 > 0:32:55Phew, I'm a doctor, not a parakeet!
0:32:55 > 0:32:57I'm a doctor.
0:33:00 > 0:33:04Disco, has memorised over 130 phrases in all.
0:33:06 > 0:33:08My cage is bigger on the inside.
0:33:08 > 0:33:11My cage is bigger on the inside.
0:33:11 > 0:33:14Like learning any new language, practice makes perfect,
0:33:14 > 0:33:17even if it means talking in your sleep.
0:33:17 > 0:33:19Give me free ride. Keep up.
0:33:19 > 0:33:21Give me for free.
0:33:22 > 0:33:24Nobody expects...
0:33:27 > 0:33:28Good night Disco.
0:33:30 > 0:33:33The intimacy between Disco and his owner may be unusual,
0:33:33 > 0:33:37but the desire to play can bring the oddest of couples together.
0:33:59 > 0:34:01The puppy uses play bows to start a game,
0:34:01 > 0:34:04something a cat wouldn't normally understand.
0:34:07 > 0:34:09But, the cat has known the puppy since she was born,
0:34:09 > 0:34:12and he's learnt her playful signals.
0:34:13 > 0:34:17Having agreed to a game, he keeps his claws firmly sheathed.
0:34:36 > 0:34:39Cats and dogs are our most popular pets,
0:34:39 > 0:34:41but we treat them both very differently.
0:34:47 > 0:34:49Cats are the only pets with the freedom
0:34:49 > 0:34:51to come and go as they please.
0:34:59 > 0:35:01With plenty of time to play with,
0:35:01 > 0:35:03this ginger tom has created his own game.
0:35:11 > 0:35:13He free climbs for fun.
0:35:13 > 0:35:15He could have used the cat flap!
0:35:17 > 0:35:21Impressive, but great feats require careful preparation.
0:35:24 > 0:35:27He scratches to make sure his claws are sharp.
0:35:35 > 0:35:38This removes old claw coverings, which break off and fall.
0:35:44 > 0:35:49These sheaths protect the new sharp claw growing underneath.
0:35:54 > 0:35:57They are lost naturally every few weeks.
0:35:58 > 0:36:00But it's better to be safe.
0:36:02 > 0:36:05Climbing demands equipment that can be relied on.
0:36:16 > 0:36:19A loose sheath now could spell disaster.
0:36:30 > 0:36:34When the climb gets challenging, he has a hidden tool.
0:36:36 > 0:36:37It flicks out like a knife.
0:36:39 > 0:36:41This is the dewclaw -
0:36:41 > 0:36:45a claw wild cats use to climb trees while chasing prey.
0:36:56 > 0:36:59This tom needs all the help he can get.
0:37:27 > 0:37:30This is what's commonly called a cliff-hanger.
0:37:35 > 0:37:37Another sheath falls - a close shave.
0:37:43 > 0:37:48With all his proverbial lives intact, he survives another day.
0:37:48 > 0:37:53The black cat was simply expressing his irrepressible urge to play.
0:38:00 > 0:38:03In contrast, playtime for dogs
0:38:03 > 0:38:05is usually at the hands of their owners.
0:38:05 > 0:38:10But in her doggy world, being taken for a walk is seen very differently.
0:38:14 > 0:38:17For her, it's an imaginary hunt.
0:38:25 > 0:38:26She searches for scent trails,
0:38:26 > 0:38:29zigzagging her nose to stay on track.
0:38:29 > 0:38:31She's aware of who passed and when,
0:38:31 > 0:38:35even getting information from trails left several weeks ago.
0:38:37 > 0:38:40She's hypersensitive to every sound and movement,
0:38:40 > 0:38:42hoping for something to chase.
0:38:45 > 0:38:48Throw a ball and she's mentally back pursuing prey.
0:38:53 > 0:38:56And she catches it with instinctive precision.
0:39:03 > 0:39:05With the determination of a wild animal,
0:39:05 > 0:39:07she's always ready to run again.
0:39:28 > 0:39:30In play, fit dogs will run and run.
0:39:30 > 0:39:33Their wild relatives are champion marathon runners,
0:39:33 > 0:39:36exhausting their prey by chasing them down.
0:39:41 > 0:39:46Like a wolf, this German shepherd can reach 35mph,
0:39:46 > 0:39:49and can happily cover 50 miles in a day.
0:39:54 > 0:39:56Blanketed with fur from head to paws,
0:39:56 > 0:39:59he's perfectly insulated against the cold,
0:39:59 > 0:40:01but, when things really hot up,
0:40:01 > 0:40:04he can only sweat through his foot pads.
0:40:10 > 0:40:14Instead, he uses his tongue to lose heat by evaporation -
0:40:14 > 0:40:16as its blood vessels dilate,
0:40:16 > 0:40:19the tongue extends and swells.
0:40:21 > 0:40:24Panting cools the hot blood even faster.
0:40:31 > 0:40:34Thermal imagery shows where all the heat escapes,
0:40:34 > 0:40:38and how no heat is lost through his thick coat of fur.
0:40:52 > 0:40:54With a pet so geared for a life chasing prey,
0:40:54 > 0:40:58it's hardly surprising they're sometimes so difficult to control.
0:41:02 > 0:41:04Let a dog off the leash
0:41:04 > 0:41:06and her natural instincts kick in.
0:41:08 > 0:41:12She's always on the edge of doing something wild and unexpected.
0:41:29 > 0:41:33This playful dog takes the plunge again and again.
0:41:41 > 0:41:43She may enjoy her mischievous game,
0:41:43 > 0:41:45but once it had real survival value.
0:41:50 > 0:41:54Wolves still often use doggy paddle to cross rivers in pursuit of prey.
0:41:57 > 0:42:01When a dog swims, he simply trots as he would on land,
0:42:01 > 0:42:03but makes longer and faster strides.
0:42:03 > 0:42:05This bearded collie
0:42:05 > 0:42:08shows how surprisingly effective this stroke is.
0:42:19 > 0:42:22For maximum efficiency, she spreads her paws on the downstroke.
0:42:46 > 0:42:49Dogs see surprisingly well under water, too.
0:43:16 > 0:43:19As they doggy paddle, they practise skills
0:43:19 > 0:43:22that helped their ancestors become the most widespread
0:43:22 > 0:43:23of all predators.
0:43:35 > 0:43:38Dogs are unusual in having such freedom.
0:43:38 > 0:43:41Most pets have to fulfil their natural urges
0:43:41 > 0:43:43within the confines of their cage.
0:43:51 > 0:43:53All pet golden hamsters
0:43:53 > 0:43:55are descended from just one family
0:43:55 > 0:43:57found in the deserts of Syria
0:43:57 > 0:43:59in the middle of the last century.
0:44:00 > 0:44:02Give them a tunnel system,
0:44:02 > 0:44:03and they are transported
0:44:03 > 0:44:05back to the wild.
0:44:10 > 0:44:13In the desert, they would shelter from the heat and predators
0:44:13 > 0:44:15by hiding in burrows during the day.
0:44:25 > 0:44:29Moving X-rays reveal just how manoeuvrable he is.
0:44:33 > 0:44:37His flexible spine allows him to take sharp turns easily.
0:44:55 > 0:44:59In fact, his spine is so bendy, he can completely turn back on himself.
0:45:02 > 0:45:06Few other animals can perform this complete U-turn.
0:45:32 > 0:45:34Presented with food,
0:45:34 > 0:45:35he acts as if it's his last meal,
0:45:35 > 0:45:39stuffing the surplus into cheek pouches to be eaten later.
0:46:05 > 0:46:07To keep his food fresh and dry,
0:46:07 > 0:46:09he secretes no saliva.
0:46:10 > 0:46:14X-ray shows just how he packs it all in.
0:46:14 > 0:46:17His pouches extend all the way to his hips.
0:46:38 > 0:46:40And when he can't fit in another morsel,
0:46:40 > 0:46:43he carries his favourite treat with him.
0:46:46 > 0:46:48Easier said than done!
0:47:15 > 0:47:18Disgorging his stash is his next challenge.
0:47:23 > 0:47:25The nuts stick to his dry cheek pouches.
0:47:37 > 0:47:39But he has a way to tackle the problem -
0:47:39 > 0:47:42his surprisingly dexterous paws.
0:48:00 > 0:48:03Hamsters make these stores, because in the desert
0:48:03 > 0:48:05they never know where their next meal may come from.
0:48:12 > 0:48:16Here it's a form of play - a way to enjoy wild behaviour
0:48:16 > 0:48:18that in captivity has no real purpose.
0:48:29 > 0:48:32Even a pet that has all the freedom in the world,
0:48:32 > 0:48:33like this Birman cat,
0:48:33 > 0:48:36still spends most of her waking hours hunting
0:48:36 > 0:48:38for no useful reason at all.
0:48:55 > 0:48:58The urge to hunt may be irresistible
0:48:58 > 0:48:59but as she's never hungry
0:48:59 > 0:49:02there's no point killing the vole.
0:49:02 > 0:49:03It's far more fun to release it
0:49:03 > 0:49:05in the confines of her home.
0:49:07 > 0:49:09Hunting is no longer a necessity -
0:49:09 > 0:49:12it too has become a game.
0:49:15 > 0:49:18The point isn't to kill her prey -
0:49:18 > 0:49:19it's all about the chase.
0:49:22 > 0:49:24Even at the risk of losing it completely.
0:49:26 > 0:49:29VOLE SQUEAKS
0:49:36 > 0:49:38VOLE SQUEAKS
0:49:51 > 0:49:53Such cat and mouse games
0:49:53 > 0:49:55are the whole focus of her free time.
0:49:55 > 0:49:57She spent over 20 hours hunting
0:49:57 > 0:49:59just to get this vole.
0:50:16 > 0:50:19Having invested so much time catching it,
0:50:19 > 0:50:21she's not about to let it go easily.
0:50:35 > 0:50:37But then again,
0:50:37 > 0:50:39it's so easy to lose concentration.
0:50:43 > 0:50:45VOLE SQUEAKS
0:50:45 > 0:50:47It may be frustrating,
0:50:47 > 0:50:48but at least she's fulfilled her
0:50:48 > 0:50:50natural urge to hunt.
0:50:53 > 0:50:56Domestic cats rarely eat their kills,
0:50:56 > 0:50:59they have everything they need presented on a plate.
0:51:03 > 0:51:04Cats are unusual among our pets
0:51:04 > 0:51:08as they are free to come and go from our homes as they please.
0:51:12 > 0:51:14But in Cusco in Peru,
0:51:14 > 0:51:16pet dogs traditionally do the same.
0:51:20 > 0:51:23Each day they're let out from their house to do whatever they wish.
0:51:23 > 0:51:25THEY BARK
0:51:36 > 0:51:40To reveal their secret lives, some are carrying mini-cameras.
0:52:00 > 0:52:03Each dog seems to be on its own individual mission.
0:52:11 > 0:52:13But as they travel, numbers build.
0:52:22 > 0:52:25Fortunately, they're streetwise and traffic savvy.
0:52:28 > 0:52:30CARS TOOTING
0:52:42 > 0:52:46Although some of these dogs are strays, most have owners,
0:52:46 > 0:52:50and all know the streets of Cusco as well as any local cab driver.
0:52:55 > 0:52:57They not only have a surprising grasp of road safety,
0:52:57 > 0:53:00but they understand human etiquette, too.
0:53:00 > 0:53:02They're never aggressive to people
0:53:02 > 0:53:04and just step into line as they pass.
0:53:07 > 0:53:09They seem to be converging on the same spot.
0:53:17 > 0:53:22This is their city, and they know every secret gathering place.
0:53:26 > 0:53:30The camera-dog soon finds the gang - a huge pack of 20.
0:53:31 > 0:53:33DOGS BARK UP AHEAD
0:53:37 > 0:53:40This is far bigger than the average wolf pack,
0:53:40 > 0:53:43and, unlike wolves, these dogs are unrelated -
0:53:43 > 0:53:45they are just mutts from all over town.
0:53:50 > 0:53:53The camera-dog takes a closer look.
0:53:56 > 0:53:59The centre of attention is this female on heat.
0:54:02 > 0:54:06The scent enticed the males from three miles away, or more.
0:54:08 > 0:54:11But the camera-dog is pushing his luck -
0:54:11 > 0:54:13she already has a partner.
0:54:13 > 0:54:16VICIOUS SNARLING
0:54:17 > 0:54:20She's chosen a dog with proven tough credentials.
0:54:31 > 0:54:34This canine bruiser holds everyone else at bay.
0:54:34 > 0:54:37SNARLING CONTINUES
0:54:45 > 0:54:49It's only the people who are playing games, now -
0:54:50 > 0:54:53for the dogs, things have just got serious.
0:54:56 > 0:54:58In frustration, fights break out.
0:54:58 > 0:55:01SNARLING AND BARKING
0:55:01 > 0:55:02And this is no dog park,
0:55:02 > 0:55:04this is real street-fighting.
0:55:04 > 0:55:06BARKING AND SNARLING
0:55:10 > 0:55:13But, despite the ferocity,
0:55:13 > 0:55:16the rules they learned as playful puppies govern the encounter -
0:55:16 > 0:55:18the bites rarely make contact,
0:55:18 > 0:55:20and no-one gets seriously hurt.
0:55:26 > 0:55:29Through these fights, everyone gets to know who is top dog.
0:55:30 > 0:55:33He might not be the best-looking mutt in town,
0:55:33 > 0:55:36but he is the one who finally gets the girl.
0:55:45 > 0:55:49Despite the aggression that got these new romantics together,
0:55:49 > 0:55:52there is surprising affection between them.
0:55:55 > 0:55:58And there's something else very special about these dogs -
0:55:58 > 0:56:00at the end of the day, it's their choice
0:56:00 > 0:56:02whether to go home.
0:56:03 > 0:56:06As soon as it's dinner time, they start to peel away.
0:56:10 > 0:56:12Some travel in groups...
0:56:13 > 0:56:17..and others travel alone.
0:56:17 > 0:56:19But they've just one place in mind.
0:56:20 > 0:56:23In a choice between the wild and home comforts -
0:56:23 > 0:56:25they know where their loyalties lie.
0:56:28 > 0:56:31It's their close companionship with us,
0:56:31 > 0:56:33that keeps the wild wolf at bay.
0:56:41 > 0:56:44Cusco dogs may openly lead a double life,
0:56:44 > 0:56:47but all our pets find ways to get in touch with their wild side
0:56:47 > 0:56:49even if it's just through play.
0:56:53 > 0:56:55They may live among us
0:56:55 > 0:56:57and be cared for and adored,
0:56:57 > 0:56:58but their true wild nature
0:56:58 > 0:57:00is just a whisker away.
0:57:02 > 0:57:03Hola!
0:57:05 > 0:57:08Next time, we'll see how the hidden senses
0:57:08 > 0:57:10and secret communications of our pets
0:57:10 > 0:57:12also keeps them wild at heart.
0:57:34 > 0:57:37Subtitles by Red Bee Media Ltd