0:00:45 > 0:00:51I am looking at one of the most striking and instantly identifiable animals in the world.
0:00:51 > 0:00:55A single one is worth about a million pounds.
0:00:55 > 0:00:59Famously fussy in their feeding, less than 1,000 survive in the wild.
0:00:59 > 0:01:05Millions are spent conserving them. Yet, increasingly, if you want to see one,
0:01:05 > 0:01:09you have to come to a zoo, like this one in Atlanta.
0:01:09 > 0:01:12It's a giant panda.
0:01:13 > 0:01:15When it comes to food,
0:01:15 > 0:01:18the giant panda is the ultimate specialist.
0:01:18 > 0:01:22It eats bamboo and virtually nothing else.
0:01:27 > 0:01:29Few animals can live on such a diet.
0:01:29 > 0:01:34Bamboo is tough, fibrous and very indigestible.
0:01:35 > 0:01:38With no competition, pandas thrived -
0:01:38 > 0:01:43until the bamboo forests in their native China started to disappear.
0:01:44 > 0:01:49Then, with no other food to fall back on, their population crashed.
0:01:50 > 0:01:55So the giant panda lives its life on the edge.
0:01:55 > 0:01:58But there are other feeding strategies.
0:01:58 > 0:02:03Instead of being a specialist, you can be a generalist, an omnivore,
0:02:03 > 0:02:07prepared to eat pretty well anything you can find - animal or vegetable.
0:02:07 > 0:02:14That strategy has led to some animals that are the most successful and charismatic of all.
0:02:14 > 0:02:18So what does it take to be an omnivore, and who are they?
0:02:24 > 0:02:28Omnivores are the most adaptable animals in the world,
0:02:28 > 0:02:32and there is no better example of this than the North American racoon,
0:02:32 > 0:02:37which is as varied in its diet as the panda is specialised.
0:02:37 > 0:02:44This remarkable mammal has adapted to more types of habitat than almost any other.
0:02:44 > 0:02:48The skills that have enabled it to do so are many,
0:02:48 > 0:02:51but there is one which it shares with all omnivores -
0:02:51 > 0:02:55the ability to make the most of any opportunity.
0:03:05 > 0:03:10The racoon owes much of its success to its inquisitive nature,
0:03:10 > 0:03:14but it also has a special trick up its sleeve -
0:03:14 > 0:03:17extremely sensitive hands.
0:03:22 > 0:03:25Touch is the racoon's most powerful sense.
0:03:27 > 0:03:31To process the information it gets from its hands,
0:03:31 > 0:03:34it uses an unusually large proportion of its brain -
0:03:34 > 0:03:37about the same as humans use for sight.
0:03:37 > 0:03:41Scientists believe that a racoon - through touch -
0:03:41 > 0:03:45can construct a picture of its surroundings
0:03:45 > 0:03:51that is as complex as that which we perceive with our eyes.
0:03:51 > 0:03:54You might say that the racoon sees with its hands.
0:03:54 > 0:04:00It can feel the difference between a rock and a clam in a split second.
0:04:06 > 0:04:10If it touches a crayfish, which is armed with powerful pincers,
0:04:10 > 0:04:13then second sight is very valuable.
0:04:22 > 0:04:27Their extraordinary sense of touch is not even affected by temperature.
0:04:29 > 0:04:31Unlike human beings,
0:04:31 > 0:04:36racoon hands keep their sensitivity even in the coldest water,
0:04:36 > 0:04:41allowing them to forage in rivers and streams whatever the season.
0:04:44 > 0:04:49Racoons have been around for nearly two-and-a-half million years,
0:04:49 > 0:04:53but the first opportunists appeared much earlier than that.
0:04:59 > 0:05:03Being able to eat pretty well anything
0:05:03 > 0:05:07was by no means the basic condition of mammals.
0:05:07 > 0:05:14The very first of them - contemporaries of the dinosaurs, small insignificant creatures -
0:05:14 > 0:05:18had such tiny teeth, they probably ate little but insects.
0:05:18 > 0:05:24But specialist omnivores did eventually appear among the prehistoric mammals.
0:05:29 > 0:05:32One lived here in South Dakota,
0:05:32 > 0:05:36though then, of course, the climate and vegetation was very different.
0:05:36 > 0:05:41It's called Dynohyus, and some experts have likened it
0:05:41 > 0:05:44to a kind of killer warthog.
0:05:46 > 0:05:49This animal was as big as a rhino.
0:05:49 > 0:05:52It had a large hairy crest running down its spine,
0:05:52 > 0:05:56a long snout and a formidable set of teeth.
0:06:03 > 0:06:07Dynohyus died out about 20 million years ago,
0:06:07 > 0:06:11but its teeth can tell us what it ate.
0:06:11 > 0:06:17At the back, it had massive, flat molars that could grind up almost any kind of vegetation.
0:06:18 > 0:06:21But it wasn't a specialised vegetarian
0:06:21 > 0:06:24because the teeth at the front
0:06:24 > 0:06:29didn't have those sharp, chisel-like teeth that an antelope has.
0:06:29 > 0:06:33Neither was it a specialised meat-eater
0:06:33 > 0:06:36because the teeth at its middle jaw
0:06:36 > 0:06:41are not the slicing, sharp teeth of a lion. But they ARE formidable.
0:06:41 > 0:06:44So are the big tusks at the front.
0:06:44 > 0:06:48In fact, what you have here is a generalised tool kit
0:06:48 > 0:06:52that enabled the animal to deal with almost anything.
0:07:03 > 0:07:07Dynohyus may be extinct, but teeth like these
0:07:07 > 0:07:10are typical of all living omnivores today.
0:07:15 > 0:07:19The forests of Sulawesi in Indonesia are haunted
0:07:19 > 0:07:25by a rare, elusive animal that looks almost as prehistoric as Dynohyus.
0:07:26 > 0:07:31To find food here, this animal uses not touch but another super-sense -
0:07:31 > 0:07:34the one possessed by all omnivores.
0:07:37 > 0:07:41The thud of a large pangi fruit hitting the ground
0:07:41 > 0:07:46might attract the attention of an animal nearby,
0:07:46 > 0:07:50but sounds don't travel far in these thick forests.
0:07:50 > 0:07:55Scent, however, can drift on breezes and be detected from great distances
0:07:55 > 0:07:58by an animal with a really sensitive nose.
0:08:05 > 0:08:08And this creature certainly has that.
0:08:12 > 0:08:16It's a babirusa, and its sense of smell
0:08:16 > 0:08:22is probably as good as that of any omnivore, alive or dead.
0:08:25 > 0:08:27There are several of them here,
0:08:27 > 0:08:31attracted by the smell of the ripe pangi.
0:08:32 > 0:08:38Males have teeth in their top jaw that grow up and through its snout.
0:08:38 > 0:08:42The size of these tusks is a good indicator of strength,
0:08:42 > 0:08:47so they determine who gives way to whom.
0:08:49 > 0:08:52The pangi fruit may smell good,
0:08:52 > 0:08:56but there's a problem - it contains a poison.
0:08:56 > 0:09:00The babirusa, however, knows how to deal with that.
0:09:01 > 0:09:04It visits a clay lick.
0:09:07 > 0:09:11Clay containing the right sort of medicine is not common
0:09:11 > 0:09:14and these licks are few and far between.
0:09:14 > 0:09:19A large one like this attracts babirusa from miles around.
0:09:23 > 0:09:28These are the only places where this rare animal is seen in any numbers.
0:09:32 > 0:09:35The clay contains a mineral
0:09:35 > 0:09:40which helps to neutralise the toxins in the pangi.
0:09:40 > 0:09:45Babirusa, like most omnivores, live in relatively small groups,
0:09:45 > 0:09:49for they specialise in picking up odd bits and pieces,
0:09:49 > 0:09:54which seldom occur in sufficient concentration to sustain a herd.
0:09:55 > 0:09:58So the clay lick, for the babirusa,
0:09:58 > 0:10:02is a time when individuals that lead relatively lonely lives
0:10:02 > 0:10:05get to know one another.
0:10:07 > 0:10:11Young males get a chance to test their strength.
0:10:35 > 0:10:40The nose, for any pig, is its greatest asset.
0:10:41 > 0:10:46A multi-purpose tool which not only locates food, but digs it up as well.
0:10:52 > 0:10:56Wild boar, the European cousin of the babirusa,
0:10:56 > 0:10:59are unrivalled foragers.
0:11:02 > 0:11:05They are the least fussy of feeders.
0:11:05 > 0:11:08Worms make a tasty snack,
0:11:08 > 0:11:12but pigs know very well that there's plenty of other food here.
0:11:17 > 0:11:19It's just a question of finding it.
0:11:23 > 0:11:28Their memories carry the smells and images of all sorts of things
0:11:28 > 0:11:32that they've previously eaten and assessed.
0:11:34 > 0:11:40Keeping an open mind means that nothing will be overlooked.
0:11:44 > 0:11:47Certainly not a decaying pigeon.
0:11:50 > 0:11:55Foraging in the woodland is not difficult in summer,
0:11:55 > 0:12:00but what happens when the ground is hidden beneath a blanket of snow?
0:12:03 > 0:12:06Food is now very scarce.
0:12:06 > 0:12:11The carcass of an animal killed by the hard winter is a valuable prize,
0:12:11 > 0:12:15but the pigs must continue foraging in the normal way
0:12:15 > 0:12:18to maintain their strength.
0:12:18 > 0:12:21They are not just ploughing through the snow at random.
0:12:21 > 0:12:26They are still guided by their nose, for smell travels through snow.
0:12:30 > 0:12:35And there's an interesting smell... right here.
0:12:37 > 0:12:40And here.
0:12:42 > 0:12:47By following their noses, pigs can keep active throughout winter.
0:12:50 > 0:12:53Other opportunists use a different tactic.
0:12:53 > 0:12:59They spend the winter asleep in underground dens and appear when the spring brings better weather.
0:12:59 > 0:13:02This is the Asiatic racoon dog.
0:13:02 > 0:13:07Its legs are so short that it has difficulty in moving through snow -
0:13:07 > 0:13:10which may be one reason why it hibernates.
0:13:13 > 0:13:16It, too, eats almost anything.
0:13:16 > 0:13:21The females, in particular, need to do so for they produce large litters
0:13:21 > 0:13:27and supplying all her babies with milk makes great demands on a mother.
0:13:27 > 0:13:29She has produced 15 pups.
0:13:29 > 0:13:34They ALL need to put on considerable weight to survive the winter -
0:13:34 > 0:13:39and they will only be helped by their parents for eight short weeks.
0:13:40 > 0:13:44Their first food is their mother's milk.
0:13:47 > 0:13:51But very soon they need solid food as well
0:13:51 > 0:13:56and that, too, has to be provided by Mother.
0:13:58 > 0:14:03While she goes off to forage, the male stays to look after the pups.
0:14:03 > 0:14:06Surprisingly - given the size of his family -
0:14:06 > 0:14:10he does virtually nothing to help feed them.
0:14:17 > 0:14:21The female is coming back. She has caught a small rodent.
0:14:23 > 0:14:28Unlike many canids, racoon dogs do not regurgitate food for the babies
0:14:28 > 0:14:32and, since mouths hold less than stomachs,
0:14:32 > 0:14:36this limits the amount of food she can bring back.
0:14:36 > 0:14:42As a consequence, she has to provide her cubs with milk for twice as long as any other dog does.
0:14:49 > 0:14:52She'll make a number of journeys every day,
0:14:52 > 0:14:56but most of the things she brings back
0:14:56 > 0:14:59are only enough for a single pup.
0:14:59 > 0:15:01This time she has brought an egg.
0:15:01 > 0:15:05The pups haven't yet learned how to deal with such a strange object.
0:15:05 > 0:15:09Is it worth eating and, if so, how?
0:15:18 > 0:15:22Yes, it is!
0:15:22 > 0:15:25And the pups won't forget.
0:15:30 > 0:15:34Before long, they must start foraging for themselves,
0:15:34 > 0:15:40with their parents alongside to give them some guidance on what is edible.
0:15:41 > 0:15:44They don't always get it right.
0:15:47 > 0:15:53They must learn fast, for each will have to get as fat as its mother
0:15:53 > 0:15:57if it is to survive the long sleep through winter -
0:15:57 > 0:15:59and not all of the litter will do so.
0:15:59 > 0:16:02Racoon dogs store food as fat,
0:16:02 > 0:16:06but another omnivore has a different tactic.
0:16:13 > 0:16:16Chickens - one of mankind's favourite prey,
0:16:16 > 0:16:19which he keeps in unnatural concentrations
0:16:19 > 0:16:24to provide himself with fresh meat and eggs all the year round.
0:16:26 > 0:16:30In farmyards like this, chickens are easy targets
0:16:30 > 0:16:34for any opportunist determined enough to find its way in.
0:16:45 > 0:16:50If there is a weak link in the defences, a fox will find it.
0:17:11 > 0:17:13FRANTIC SQUAWKING AND CLUCKING
0:17:20 > 0:17:24Foxes are frequently blamed for killing more than they need.
0:17:24 > 0:17:29But do they really deserve such a bloodthirsty reputation?
0:17:29 > 0:17:34No. A fox will not waste what it kills -
0:17:34 > 0:17:37providing it's not disturbed.
0:17:40 > 0:17:46But it must act quickly if it's to make the most of such an opportunity.
0:17:47 > 0:17:51Few realise that foxes bury their surplus food.
0:17:53 > 0:17:57They are saving it for when times get tough.
0:18:19 > 0:18:24A vixen will bury carcasses all over her territory.
0:18:24 > 0:18:28Later, she will use her memory and her keen sense of smell
0:18:28 > 0:18:31to find them again and dig them up.
0:18:31 > 0:18:34The fox is not a wanton killer,
0:18:34 > 0:18:38but an intelligent opportunist who thinks ahead.
0:18:45 > 0:18:49Some opportunities are both brief and seasonal.
0:18:50 > 0:18:54There is an abundant source of food in this cave,
0:18:54 > 0:18:59but only for a few weeks and it lies right in its far depths.
0:19:00 > 0:19:03Down here, it is totally dark
0:19:03 > 0:19:07and we can only see what goes on by using infrared cameras.
0:19:09 > 0:19:12Darkness, of course, is not a problem for bats
0:19:12 > 0:19:14who navigate by echolocation.
0:19:14 > 0:19:17But for any other animal, getting around down here
0:19:17 > 0:19:20presents a serious challenge.
0:19:24 > 0:19:27And there's another major obstacle.
0:19:27 > 0:19:31The droppings produced by the vast assemblage of bats
0:19:31 > 0:19:35creates an atmosphere thick with ammonia and fungal spores
0:19:35 > 0:19:39that can be fatal to those that inhale them.
0:19:39 > 0:19:43This guano accumulating on the cave floor sustains more than fungus.
0:19:43 > 0:19:48There is a living carpet of flesh-eating beetles and larvae
0:19:48 > 0:19:52which, together, make short work of anything they can get hold of.
0:19:52 > 0:19:56In fact, this is about as hostile an environment
0:19:56 > 0:20:01as you will find anywhere on the planet.
0:20:01 > 0:20:07Yet that doesn't deter one unfussy, enterprising opportunist - the skunk.
0:20:09 > 0:20:13Indeed, skunks seem almost at home here.
0:20:13 > 0:20:15They even indulge in courtship -
0:20:15 > 0:20:20as can happen when a male blunders into a female in the pitch dark.
0:20:20 > 0:20:25But what is it that tempts them down into this repellent place?
0:20:30 > 0:20:33The answer is baby bats.
0:20:33 > 0:20:36At this age, they are unable to fly
0:20:36 > 0:20:41and, in such a jostling crowd, many lose their footholds and fall.
0:20:46 > 0:20:50On the ground, the babies are in great danger.
0:20:52 > 0:20:54The skunks can see nothing whatever,
0:20:54 > 0:20:57so the fallen bats may survive
0:20:57 > 0:21:03if only they can regain the safety of the rock wall.
0:21:13 > 0:21:18But so many bats fall that the skunks blunder into quite enough
0:21:18 > 0:21:21to make their visit worthwhile.
0:21:25 > 0:21:31In the darkness, the skunks can't be sure which end of the bat is which
0:21:31 > 0:21:34so, to avoid getting bitten,
0:21:34 > 0:21:38they roll the bat on the ground to subdue it.
0:21:43 > 0:21:47It is not just skunks that make the most of this seasonal offering.
0:21:47 > 0:21:51The touchy-feely racoons are here, too.
0:21:51 > 0:21:54In fact, it might seem to be just the place
0:21:54 > 0:21:58for an opportunist that can see with its hands.
0:22:01 > 0:22:09Exactly which sense the skunks and racoons use to find the bats in the pitch-black cave, no-one knows.
0:22:09 > 0:22:14Smell seems unlikely, given the overpowering stench of ammonia here.
0:22:14 > 0:22:19And how could a skunk or a racoon possibly hear the distress calls
0:22:19 > 0:22:24of a single bat above the deafening squeaks of several million others?
0:22:30 > 0:22:35The most likely answer is that they use a combination of touch and luck.
0:22:36 > 0:22:41Both racoons and skunks must rely on, literally, bumping into the bats.
0:22:44 > 0:22:47This bonanza will only last for about a month.
0:22:47 > 0:22:51Then these opportunists will revert to more reliable sources of food.
0:22:55 > 0:22:57Elsewhere in the world, however,
0:22:57 > 0:23:01making the most of seasonal abundancies is a way of life.
0:23:01 > 0:23:08Up here in Alaska during the summer, a whole succession of different food become available.
0:23:08 > 0:23:14And there's a spectacular animal here that's prepared to sample each and every one of them.
0:23:14 > 0:23:19No one dish is available for long, so you have to make the best of it.
0:23:19 > 0:23:22And top of the menu right now is salmon!
0:23:24 > 0:23:29It is the favourite food of the largest and the most formidable
0:23:29 > 0:23:32of all omnivores - grizzly bears.
0:23:32 > 0:23:37Salmon are plentiful now but, six months ago in the middle of winter,
0:23:37 > 0:23:43conditions were so harsh that it was impossible for a large animal to get enough to eat.
0:23:43 > 0:23:50All a bear can do then is to sit it out and try and conserve as much energy as possible.
0:23:50 > 0:23:54To see how they cope with these enormous seasonal changes,
0:23:54 > 0:23:57we must go back six months.
0:23:57 > 0:24:01In October, grizzly bears went into a deep sleep.
0:24:01 > 0:24:04Their temperature drops several degrees
0:24:04 > 0:24:08and their pulse rate decreases to about ten beats a minute.
0:24:08 > 0:24:13They do not eat, drink or defecate, but they do occasionally stir.
0:24:15 > 0:24:20During hibernation, a bear burns up almost a million calories...
0:24:22 > 0:24:26..virtually emptying its energy reserves.
0:24:38 > 0:24:42By spring, the bears have lost nearly a third of their body weight.
0:24:42 > 0:24:47To avoid starvation, they must now find food, and quickly.
0:24:50 > 0:24:55Their diet will be driven by a clearly defined seasonal cycle.
0:24:55 > 0:24:58Now, in April, they eat roots.
0:25:01 > 0:25:04Roots are followed by grass.
0:25:04 > 0:25:07It's easy food,
0:25:07 > 0:25:12but they'll move on to the next course if something big shows up.
0:25:15 > 0:25:20A whale carcass could last a month. By May, fresh meat is on the menu.
0:25:59 > 0:26:03Mid-summer, and they're back on the salmon.
0:26:09 > 0:26:14This bear has been out of hibernation for about four months.
0:26:14 > 0:26:20Surprisingly, it has not gained any weight. It may even have lost weight.
0:26:20 > 0:26:26But if it is to survive the coming winter, now is the time when it really has to pack on the pounds.
0:26:31 > 0:26:34Salmon - one of the most important sources of food for bears -
0:26:34 > 0:26:37is now available in quantity
0:26:37 > 0:26:41as the fish migrate in thousands up the rivers to spawn.
0:27:13 > 0:27:18Chasing them uses a lot of energy, but the rewards are great.
0:27:18 > 0:27:21Salmon are rich in protein and fat.
0:27:28 > 0:27:30So valuable is this source of food
0:27:30 > 0:27:34that a bear that hasn't got a salmon of its own
0:27:34 > 0:27:38will spend considerable energy in trying to steal someone else's.
0:27:50 > 0:27:54In a good salmon year, a bear can catch a dozen a day,
0:27:54 > 0:27:58giving a huge boost to its energy reserves.
0:28:01 > 0:28:06But some parts of a fish are more nourishing than others.
0:28:06 > 0:28:11If there are lots around, the grizzlies will eat only brains...
0:28:11 > 0:28:14and caviar.
0:28:14 > 0:28:18This behaviour piles on even more calories.
0:28:23 > 0:28:25Even when there are no salmon to be caught,
0:28:25 > 0:28:29bears can still find food out on these estuaries.
0:28:29 > 0:28:34Like pigs, they have an extraordinarily acute sense of smell
0:28:34 > 0:28:38and that can guide them to food, even beneath the surface of the sand.
0:28:41 > 0:28:45Clams!
0:28:45 > 0:28:49But how on earth can an animal with massive paws and huge claws
0:28:49 > 0:28:54manage to open and extract meat from a tiny shell like this?
0:28:56 > 0:29:00The answer is... with surprising dexterity.
0:29:01 > 0:29:06Clams may look small in the paws of a grizzly bear,
0:29:06 > 0:29:08but they are still worth the effort.
0:29:15 > 0:29:19Early autumn. Two months to go before hibernation
0:29:19 > 0:29:23and the bear's appetite steps up a gear.
0:29:23 > 0:29:29A seasonal change in the bear's physiology allows them to eat continuously
0:29:29 > 0:29:33without ever feeling full - a huge advantage during the berry season.
0:29:33 > 0:29:38They may eat as many as 200,000 berries a day
0:29:38 > 0:29:43and that gives the next big boost to a bear's energy reserves.
0:29:45 > 0:29:49But at this time of the year, they will eat whatever they find.
0:30:04 > 0:30:07After three months of counting calories, they're back in shape.
0:30:09 > 0:30:15So for these grizzly bears in Alaska, the real test is now about to begin.
0:30:15 > 0:30:18With luck, they will have put on enough weight to enable them to
0:30:18 > 0:30:22survive five to six months of winter.
0:30:22 > 0:30:29But what is for sure is that they will only have done so by being extremely unfussy feeders.
0:30:33 > 0:30:37The lifestyle of a generalist may seem a good strategy,
0:30:37 > 0:30:40but from an evolutionary perspective,
0:30:40 > 0:30:44there is always the temptation to specialise.
0:30:44 > 0:30:47In India, there is another bear
0:30:47 > 0:30:50happy to tackle anything remotely edible.
0:30:50 > 0:30:55But that is only for half the year. This bear - the sloth bear -
0:30:55 > 0:30:59has started down the road to specialisation.
0:31:01 > 0:31:06Inside this mound of clay lies a huge quantity of food
0:31:06 > 0:31:09and the sloth bear has just the right equipment to collect it.
0:31:14 > 0:31:18It has particularly large claws -
0:31:18 > 0:31:21perfect for breaking into these sun-baked termite mounds.
0:31:21 > 0:31:26It's worth the effort - one colony may contain a million individuals.
0:31:31 > 0:31:35The termites' first line of defence has been broken.
0:31:35 > 0:31:38Faced with such a large and destructive predator,
0:31:38 > 0:31:42there is little the soldier termites can do to drive the bear away.
0:31:44 > 0:31:50The bear hoovers the termites up as they swarm over their smashed mound.
0:31:56 > 0:32:01But the greatest prize are the larvae that lie inside the nest.
0:32:05 > 0:32:09The bear has other adaptations as well as big claws.
0:32:09 > 0:32:16It's lost two front teeth so, by pursing its floppy lips into a tube, it can suck insects into its mouth.
0:32:16 > 0:32:21And at the end of its snout, there's a flap that prevents dirt and dust
0:32:21 > 0:32:23going up its nose at the same time.
0:32:27 > 0:32:32But the sloth bear may be heading for danger -
0:32:32 > 0:32:37the same danger that may before long exterminate the giant panda.
0:32:37 > 0:32:41For the moment, however, there is no shortage of termites
0:32:41 > 0:32:47and the sloth bear has still not become wholly reliant on them.
0:32:51 > 0:32:57Just as humans have had an impact on the giant panda and its food,
0:32:57 > 0:33:00so they have on the sloth bear.
0:33:00 > 0:33:04In India, sloth bears live alongside people.
0:33:04 > 0:33:07Conflict between the two is common,
0:33:07 > 0:33:10resulting in hundreds of maulings every year.
0:33:15 > 0:33:20During the day, bears here must take refuge in areas not used by people.
0:33:25 > 0:33:29Sloth bears may not compete with cattle for food,
0:33:29 > 0:33:33but land turned to grazing reduces the bears' termite harvest.
0:33:35 > 0:33:39Loss of natural habitat
0:33:39 > 0:33:43has had a serious impact on wildlife across the globe,
0:33:43 > 0:33:48but man-made habitats have provided new opportunities for many omnivores.
0:33:58 > 0:34:03The modern city. It seems a sterile world of concrete, steel and glass.
0:34:03 > 0:34:08It must surely be one of the most difficult places
0:34:08 > 0:34:11for a wild animal to make a living.
0:34:11 > 0:34:13Well, it would be...
0:34:13 > 0:34:17were it not for the extravagant habits of the people who live here.
0:34:20 > 0:34:24The largest cities may contain more than ten million human inhabitants
0:34:24 > 0:34:30and, where there are people, there is food - lots of it.
0:34:30 > 0:34:36A city this size produces around 10,000 tons of waste a day.
0:34:36 > 0:34:39If the residents are not to drown in leftovers,
0:34:39 > 0:34:42it all needs to be cleaned up - continuously.
0:34:48 > 0:34:53Good hygiene is so important in these crowded conditions
0:34:53 > 0:34:58that much time and money is spent trying to sanitise our cities.
0:35:04 > 0:35:08But it isn't easy to wipe away the evidence of food, not completely.
0:35:08 > 0:35:13To an animal with an acute sense of smell, food stands out.
0:35:13 > 0:35:17Everything else is grey by comparison.
0:35:18 > 0:35:24We may not notice the scraps left behind, but what's not taken away
0:35:24 > 0:35:26can become an opportunity for others.
0:35:28 > 0:35:31Under the partial cover of darkness,
0:35:31 > 0:35:34a familiar face materialises.
0:35:37 > 0:35:42Racoons have found our cities very much to their liking.
0:35:42 > 0:35:44Their great climbing skills
0:35:44 > 0:35:49enable them to find shelter in roofs and chimney breasts during the day
0:35:49 > 0:35:56and to move with ease in all parts of this complex environment - a fact recorded by city security cameras.
0:36:00 > 0:36:03DOG BARKS
0:36:03 > 0:36:08But to find food, racoons must descend to the ground.
0:36:12 > 0:36:14They're bold and intelligent animals
0:36:14 > 0:36:20and negotiate roads as confidently as human pedestrians do.
0:36:20 > 0:36:24Indeed, city racoons are less likely to be hit by a car
0:36:24 > 0:36:27than their country cousins
0:36:27 > 0:36:31who get less experience of judging the speeds of vehicles.
0:36:40 > 0:36:45In an attempt to thwart garbage raiders,
0:36:45 > 0:36:49rubbish collection continues around the clock.
0:36:49 > 0:36:53But racoons are quick to take advantage of any opportunities.
0:36:53 > 0:36:57If there is food around, they will find it.
0:37:01 > 0:37:06The skills that made racoons so successful in their original home
0:37:06 > 0:37:11also serve them well here - in the fast lane.
0:37:17 > 0:37:21The inquisitiveness they showed when looking for food on the forest floor
0:37:21 > 0:37:24now leads them to rich pickings.
0:37:29 > 0:37:34The manual dexterity that enabled them to capture crayfish in streams
0:37:34 > 0:37:39now leads them to take off the lids of dustbins...
0:37:39 > 0:37:44and winkle morsels from jars, boxes and tins.
0:37:51 > 0:37:56Racoons are an American success story.
0:37:56 > 0:38:01Their population has increased 20 times since the 1930s
0:38:01 > 0:38:04and their range has expanded by 30%.
0:38:04 > 0:38:11They are now one of the most successful and widespread mammals on the continent.
0:38:14 > 0:38:19The biggest opportunists of all have a slightly less subtle approach.
0:38:27 > 0:38:32Bears can break into cars as easily as they can open clam shells.
0:38:32 > 0:38:36It takes more effort, but the rewards can be huge.
0:38:43 > 0:38:48Here in Britain, the streets belong to a different urban prowler -
0:38:48 > 0:38:51the red fox.
0:38:51 > 0:38:53Unlike racoons, foxes are territorial,
0:38:53 > 0:38:56but they're also extremely adaptable.
0:38:56 > 0:39:02In one year, a fox can change from being totally rural to totally urban.
0:39:02 > 0:39:04So foxes are always on the move.
0:39:16 > 0:39:21If I were to explore these city streets for just a few hours,
0:39:21 > 0:39:23I'd almost certainly see more foxes
0:39:23 > 0:39:28than I would in a whole year of walking in the countryside.
0:39:28 > 0:39:32Indeed, cities like this can support ten times as many foxes
0:39:32 > 0:39:35as a similar area in the country.
0:39:35 > 0:39:38Foxes have one other thing going for them -
0:39:38 > 0:39:41at least in Britain - their popularity.
0:39:41 > 0:39:48Surveys regularly show that the red fox is among the nation's most favourite mammals.
0:39:48 > 0:39:52That's a fact that foxes have been quick to exploit.
0:40:15 > 0:40:22Many of us encourage our friendly neighbourhood foxes by putting out food for them.
0:40:22 > 0:40:25And the foxes are only too glad to take it.
0:40:25 > 0:40:31Indeed, in this city, some 60% of a fox's diet come from free handouts.
0:40:31 > 0:40:35And the more food there is, the more foxes there are.
0:40:35 > 0:40:40However, there's another kind of urban opportunist
0:40:40 > 0:40:43that is much more successful than the red fox,
0:40:43 > 0:40:46but it's at the opposite end of the popularity scale.
0:40:46 > 0:40:51We don't encourage it in any way and yet it thrives on our leftovers.
0:40:51 > 0:40:58If statistics are anything to go by, you are within five metres of one at all times.
0:40:58 > 0:41:02In fact, there is probably one directly beneath me as I speak.
0:41:16 > 0:41:20Warm water emptying from baths and washing machines
0:41:20 > 0:41:25and sluicing into the network of sewers beneath our homes
0:41:25 > 0:41:29creates a surprisingly stable and temperate environment.
0:41:29 > 0:41:37It's an ideal habitat for one of the most widespread, adaptable mammals on the planet - the brown rat.
0:41:37 > 0:41:41It's not just the steady temperature that the rats like,
0:41:41 > 0:41:45there's a steady supply of food as well.
0:41:46 > 0:41:51Scraps flushed down the sewers allow a rat to spend its entire life here,
0:41:51 > 0:41:54though, contrary to popular belief,
0:41:54 > 0:41:59there is seldom enough food to support swarms of rats.
0:42:06 > 0:42:10The only thing rats need worry about is a sudden rise of water level.
0:42:10 > 0:42:14Sewer rats are particularly sensitised to this -
0:42:14 > 0:42:16often with good reason.
0:42:23 > 0:42:26Her nest is in danger of flooding
0:42:26 > 0:42:31but, fortunately, she knows a safer place to take her babies.
0:43:02 > 0:43:05They're guided very largely by smell
0:43:05 > 0:43:10and follow tried-and-tested routes that they know to be safe.
0:43:19 > 0:43:24Moving six youngsters under such conditions seems a hard task,
0:43:24 > 0:43:27but rats are resilient creatures -
0:43:27 > 0:43:32which makes them well-suited to living in unnatural surroundings.
0:43:43 > 0:43:47In spite of their numbers, we seldom see rats out and about,
0:43:47 > 0:43:53but we know they're there - eating our food, probably spreading disease,
0:43:53 > 0:43:57so we wage war on them with traps and poison.
0:43:57 > 0:44:01But what happens when rats live unchecked in a human society?
0:44:22 > 0:44:27In this temple in northern India, rats are sacred.
0:44:27 > 0:44:33The local people believe that, after death, they return to Earth as rats.
0:44:33 > 0:44:39So rats here are fed and protected and, indeed, worshipped.
0:44:39 > 0:44:43So this is not just a rat haven, it's a rat heaven
0:44:43 > 0:44:47and the rats take full advantage of it.
0:45:08 > 0:45:13In the wild, rats are nocturnal. But not here.
0:45:17 > 0:45:22These rats don't shun the daylight like city rats. Why should they?
0:45:22 > 0:45:25There's nothing to harm them here. And there's plenty of food.
0:45:25 > 0:45:28As a result, they swarm in great numbers.
0:45:32 > 0:45:37Colonies in the wild which grow to be about 600 strong
0:45:37 > 0:45:40normally then break down and divide.
0:45:40 > 0:45:44But here, their population has stabilised at around 6,000.
0:45:50 > 0:45:55The size of the worldwide population of rats is incalculable.
0:45:55 > 0:46:01They inhabit every continent on Earth, including Antarctica.
0:46:01 > 0:46:05Could there be a more successful mammal?
0:46:15 > 0:46:18Well, yes - us.
0:46:18 > 0:46:20The human species.
0:46:20 > 0:46:26We are the ultimate demonstration of just how successful a mammal can be
0:46:26 > 0:46:30that is prepared to eat pretty well anything.
0:46:31 > 0:46:37This is the Kumbh Mela - a spectacular Hindu festival in central India,
0:46:37 > 0:46:39attended by millions of people.
0:46:39 > 0:46:44It is the largest gathering of people for a common cause
0:46:44 > 0:46:47ever seen in the history of the world.
0:46:47 > 0:46:53Over two weeks, this temporary city on the banks of the Ganges
0:46:53 > 0:46:57will shelter a staggering 100 million people.
0:46:57 > 0:47:02Since they are Hindus, most are strictly vegetarian
0:47:02 > 0:47:06but, across the world, we seem to be able to thrive whatever the diet -
0:47:06 > 0:47:12whether it be one dominated by lentils and rice, or by hamburgers.
0:47:12 > 0:47:16We have learned how to create our own food resources
0:47:16 > 0:47:23so that our population is no longer limited by the quantity of food that occurs naturally.
0:47:27 > 0:47:33That development enabled us first to dominate the Earth and, eventually, to over-run it.
0:47:33 > 0:47:36But an essential key to our success
0:47:36 > 0:47:42has been the one that we share with rats, racoons, bears and foxes -
0:47:42 > 0:47:49an adaptable nature and an ability to seize an opportunity when we see it.
0:47:49 > 0:47:56In fact, you might say that it is not the meek that have inherited the Earth...but the opportunists.
0:48:06 > 0:48:11We first went to that cave in Texas to film the bats that roost there
0:48:11 > 0:48:13but, while we were doing so,
0:48:13 > 0:48:18we noticed that skunks were coming in at night to collect the bats that had fallen to the ground.
0:48:18 > 0:48:26If ever there was an example of opportunism among animals, that was it, so we filmed the skunks as well.
0:48:26 > 0:48:34It was behaviour that had never been recorded before, but predicting animal behaviour isn't easy.
0:48:37 > 0:48:40In order to capitalise on the skunks' behaviour,
0:48:40 > 0:48:46cameraman Paul Stewart had to work a quarter of a mile underground in truly horrible conditions.
0:48:46 > 0:48:53It's amazing. There's something like ten million bats in this cave
0:48:53 > 0:48:59as well as the skunks and racoons that we're looking for for the filming.
0:48:59 > 0:49:03There's a lot of ammonia from their droppings
0:49:03 > 0:49:08and, as well as that, we've been warned about the flesh-eating maggots and even a rattlesnake.
0:49:08 > 0:49:11So we need some serious protective gear.
0:49:11 > 0:49:14We need this mask, which will protect me from ammonia.
0:49:14 > 0:49:19I've got wellington boots to stop me sinking into the guano
0:49:19 > 0:49:26and a helmet to stop the ample amounts of urine coming from the bats.
0:49:27 > 0:49:33The camera we're using is infrared. It uses light the bats can't see,
0:49:33 > 0:49:37and nor can we, so we'll be working in total darkness.
0:49:37 > 0:49:45We hope the camera kit will work. What we don't know is whether the behaviour we want will be happening.
0:49:45 > 0:49:51It's time for us to get our kit on and go down into the cave and find out.
0:49:51 > 0:49:54The behaviour I'm here to film
0:49:54 > 0:49:58isn't one that's well known, even scientifically.
0:49:58 > 0:50:02If we're lucky, we'll have the first record
0:50:02 > 0:50:06of a supreme opportunist braving really tough conditions to get food.
0:50:06 > 0:50:11That's one of the reasons I enjoy filming - to produce firsts.
0:50:15 > 0:50:21Conditions here may suit the bats, but they challenge any other mammal, however opportunist.
0:50:22 > 0:50:26The ammonia concentration is the same as in household cleaning fluid.
0:50:28 > 0:50:32The floor of the cave is deep in bat guano,
0:50:32 > 0:50:34yet many insects feed on it,
0:50:34 > 0:50:37and anything else they can catch.
0:50:39 > 0:50:43And the temperature? 45 degrees Celsius.
0:50:59 > 0:51:06Well, that was, um...four fairly intense hours in the cave of nothing...really, turning up.
0:51:06 > 0:51:14It's really hostile down there. The ammonia was starting to get through the mask, making it hard to breathe.
0:51:14 > 0:51:17You start to smell all sorts there.
0:51:17 > 0:51:23At the same time, because of the light from the eyepiece, I was a magnet for biting insects.
0:51:23 > 0:51:26But then something amazing happens.
0:51:26 > 0:51:31The bats, you can hear they're starting to frenzy and to turn.
0:51:31 > 0:51:36Nothing can prepare you for what it's like when they're in the cave.
0:51:36 > 0:51:43Suddenly, this breeze starts up, then dust appears in the air - all the fur from the bats.
0:51:43 > 0:51:50It's like being in a Dyson vortex vacuum cleaner or something. You feel taken up in it.
0:51:50 > 0:51:54And then it starts to rain and that's the bats. When they take off,
0:51:54 > 0:51:57they lighten the load a little bit and urinate.
0:51:57 > 0:52:04I've probably been urinated on by about six million of them. Thank you, bat.
0:52:04 > 0:52:09I came out and, just so annoyingly, there was a skunk on the trail,
0:52:09 > 0:52:12having seen nothing for that whole period.
0:52:12 > 0:52:17So I think it's time for a rest, a drink of water
0:52:17 > 0:52:22and then I go back down there. Better luck next time.
0:52:24 > 0:52:26That persistence paid off.
0:52:26 > 0:52:31Paul became just another opportunist, exploiting the cave.
0:52:31 > 0:52:36The first animal we had some success filming were the opossums.
0:52:36 > 0:52:41They seem to live down here. They must have a bomb-proof constitution.
0:52:41 > 0:52:46We saw very little sign of skunks. Then we had a couple of sightings.
0:52:46 > 0:52:50Day by day, you see a little bit more and you can predict
0:52:50 > 0:52:53where the skunks will be.
0:52:53 > 0:53:00After a while, the priority became not just getting shots of skunks, but getting nice shots of skunks.
0:53:00 > 0:53:05That meant you had to be more careful with the lighting.
0:53:05 > 0:53:08By about the tenth day, we knew we'd got what we most wanted -
0:53:08 > 0:53:11a sequence never filmed or even seen before.
0:53:16 > 0:53:19Tonight, we got some skunks...
0:53:21 > 0:53:24It's quite a climb out... out of that cave.
0:53:26 > 0:53:29Anyway...we got some skunks. It looked...
0:53:29 > 0:53:34It looked good. The skunks move along the edge of the wall.
0:53:34 > 0:53:40It's kind of sad that the baby bats that have made it through the flesh-eating insects,
0:53:40 > 0:53:46they've got to the wall and they've got that tiny chance, then you see this skunk hoovering them.
0:53:48 > 0:53:51That's it. The last day of filming.
0:53:51 > 0:53:55Not the most pleasant location, but the skunks have been amazing.
0:53:55 > 0:54:00It seems that we have a sequence. That's good news.
0:54:03 > 0:54:07When filming some species, the dangers are more obvious.
0:54:07 > 0:54:13Grizzly bears are bigger, stronger, heavier and faster than you are.
0:54:13 > 0:54:16They have huge teeth and huge claws.
0:54:16 > 0:54:23In short, if they want to make a meal of you, there's little you can do to stop them.
0:54:23 > 0:54:27Yet some people specialise in getting close to grizzly bears,
0:54:27 > 0:54:32as you need to do in order to film them. How do they do it?
0:54:43 > 0:54:50Filming wildlife, you rely on experts all the time, often heavily.
0:54:50 > 0:54:57But even though you're under the guidance of an expert, you don't take your thinking cap off.
0:55:00 > 0:55:06That was great. He turned towards camera and just grabbed it. It's a shame he's behind the grass.
0:55:06 > 0:55:10Working with the grizzly bears in Alaska
0:55:10 > 0:55:14with an expert called Buck Wild, we had three close encounters
0:55:14 > 0:55:17where the bears came within six or eight feet.
0:55:20 > 0:55:27In each of those situations, Buck Wild stopped the animal by holding his hands up.
0:55:27 > 0:55:31But I would say that I never felt comfortable
0:55:31 > 0:55:36and, although he did stop the bears, one day the bears won't stop.
0:55:36 > 0:55:40I wouldn't want to be in that situation.
0:55:40 > 0:55:44One film maker has spent more time than anyone else with bears
0:55:44 > 0:55:50and has had close encounters that would terrify the bravest of men -
0:55:50 > 0:55:52Canadian, Jeff Turner.
0:55:52 > 0:55:55I've always been drawn to bears.
0:55:55 > 0:56:00I have a connection, a feeling for them that's always been there.
0:56:00 > 0:56:07I've only been charged by a bear once in the last 15 years, and that was early on.
0:56:07 > 0:56:11I think I was charged because I didn't have enough experience.
0:56:11 > 0:56:14That's all part of getting close to them -
0:56:14 > 0:56:19being able to understand when enough is enough.
0:56:19 > 0:56:26You have to understand that with an animal like a bear because if they're really not happy, they...
0:56:26 > 0:56:29they can quickly...kill you.
0:56:29 > 0:56:34The number one rule when you're working with bears
0:56:34 > 0:56:38is you don't want to surprise them. You always want them to know that you're there.
0:56:38 > 0:56:45Rule number two is, to close the distance, you've got to be unaggressive, unthreatening.
0:56:45 > 0:56:49Keep your eyes down. As they get closer, talk to them.
0:56:49 > 0:56:53It's about tone of voice. It's how you say it.
0:56:54 > 0:56:59It's about putting the bear at ease. You can communicate that easily.
0:57:02 > 0:57:06In the past, many scientists regarded animals as machines, driven by base instincts,
0:57:06 > 0:57:12and tried to classify their behaviour in simple terms.
0:57:12 > 0:57:17For these opportunist mammals, that approach is doomed to fail.
0:57:17 > 0:57:22Predicting THEIR behaviour is one of the great challenges in understanding animals.