0:00:03 > 0:00:05Planet Earth...
0:00:05 > 0:00:08millions of species...
0:00:11 > 0:00:13..but a few are special...
0:00:16 > 0:00:18..born to thrive.
0:00:19 > 0:00:22ELEPHANT SNORTS
0:00:24 > 0:00:27GORILLA HOOTS AND ROARS
0:00:27 > 0:00:29These are the opportunists.
0:00:29 > 0:00:32TRAFFIC NOISE
0:00:32 > 0:00:33The collaborators.
0:00:37 > 0:00:39The survivors.
0:00:44 > 0:00:47What makes these animals so successful?
0:00:49 > 0:00:53In this series we'll delve deep beneath the skin
0:00:53 > 0:00:57to reveal the unique features that set some species apart.
0:00:57 > 0:01:01BEAR SNIFFS
0:01:01 > 0:01:03New behaviour,
0:01:03 > 0:01:06and the very latest scientific discoveries,
0:01:06 > 0:01:09will offer fresh insight into
0:01:09 > 0:01:11the Wonder of Animals.
0:01:21 > 0:01:24From the North Pole
0:01:24 > 0:01:27to the tropics,
0:01:27 > 0:01:30and everywhere in between...
0:01:33 > 0:01:36..one group of animals
0:01:36 > 0:01:39has mastered practically every environment on earth.
0:01:42 > 0:01:44Rainforests...
0:01:45 > 0:01:47..mountains...
0:01:48 > 0:01:50..and even the open ocean.
0:01:54 > 0:01:59Wherever they live, bears have the supreme ability
0:01:59 > 0:02:02to find the highest quality food
0:02:02 > 0:02:07and this is a skill that depends upon three key factors -
0:02:09 > 0:02:14an extraordinary anatomy,
0:02:14 > 0:02:17incredible intelligence,
0:02:17 > 0:02:20and a truly remarkable physiology.
0:02:31 > 0:02:35Tropical rainforests are amongst the most bio-diverse
0:02:35 > 0:02:36places on Earth.
0:02:38 > 0:02:40Bountiful ecosystems,
0:02:40 > 0:02:42teeming with life.
0:02:46 > 0:02:49But the bears living here, are only interested
0:02:49 > 0:02:52in the most energy-rich food -
0:02:54 > 0:02:56and that is found in the most
0:02:56 > 0:02:59inaccessible places.
0:03:01 > 0:03:05To reach it requires a very specialised anatomy.
0:03:09 > 0:03:11Night-time
0:03:11 > 0:03:14in the Indian jungle.
0:03:18 > 0:03:22A sloth bear is on the hunt for food.
0:03:28 > 0:03:31But the most protein-rich meal for this bear
0:03:31 > 0:03:35is hidden inside a sun-baked fortress.
0:03:45 > 0:03:46With claws up to 8cm long,
0:03:46 > 0:03:50it breaks through the rock-hard structure...
0:03:53 > 0:03:55..to reach the prize -
0:03:55 > 0:03:57termites.
0:03:59 > 0:04:02Sloth bears can sniff out termites
0:04:02 > 0:04:05through a metre of earth.
0:04:07 > 0:04:09But once disturbed,
0:04:09 > 0:04:12the moveable feast rapidly disperses.
0:04:13 > 0:04:18So the bears have evolved a practical solution.
0:04:18 > 0:04:21They've lost their two front teeth
0:04:21 > 0:04:24and by drawing air in through the gap,
0:04:24 > 0:04:26they can suck up the termites.
0:04:27 > 0:04:32This versatile vacuuming snout means that sloth bears
0:04:32 > 0:04:35can consume vast quantities in one sitting.
0:04:38 > 0:04:41And to stop any termites straying up its nose,
0:04:41 > 0:04:45it's adapted a flap to shield its nostrils.
0:04:50 > 0:04:54Sloth bears have specialised to exploit the rich pickings
0:04:54 > 0:04:56at ground level.
0:04:57 > 0:05:00In the lush cloud forests of the Andes,
0:05:00 > 0:05:03the best food is even harder to reach -
0:05:06 > 0:05:10but not for South America's only bear species,
0:05:10 > 0:05:13the spectacled bear.
0:05:13 > 0:05:15They're lured into the trees by these -
0:05:15 > 0:05:17bromeliads.
0:05:19 > 0:05:23The problem is, they are about 15 metres off the ground.
0:05:26 > 0:05:31Taller trees with larger canopies offer more plants,
0:05:31 > 0:05:33so the higher they can climb,
0:05:33 > 0:05:35the better.
0:05:38 > 0:05:40For an animal that weighs 100kg
0:05:40 > 0:05:44this could pose quite a challenge.
0:05:45 > 0:05:49But the bears' anatomy has adapted to overcome this.
0:05:51 > 0:05:54Each front paw has an enlarged wrist bone
0:05:54 > 0:05:57which acts like a rudimentary thumb,
0:05:57 > 0:06:00helping them to grip the branches.
0:06:02 > 0:06:04The rewards for their efforts
0:06:04 > 0:06:07are the sugar rich cores of the bromeliads.
0:06:09 > 0:06:13But to access them, they must chew through the tough exterior.
0:06:16 > 0:06:18Relative to their size,
0:06:18 > 0:06:20spectacled bears have the largest jaw muscles of any bear species...
0:06:26 > 0:06:30..and teeth that are secured into their jaws with three roots,
0:06:30 > 0:06:32instead of two.
0:06:36 > 0:06:40But what if the food you seek is not only in the treetops,
0:06:40 > 0:06:43but also has a built-in deterrent, too?
0:06:48 > 0:06:51In the dense lowland forest of Borneo,
0:06:51 > 0:06:55sun bears are on the hunt for an exceptionally concentrated
0:06:55 > 0:06:57source of calories -
0:06:57 > 0:06:59honey.
0:07:01 > 0:07:05And they use a perfect combination of adaptations to get it.
0:07:08 > 0:07:11Whilst smell is their primary sense,
0:07:11 > 0:07:15as they climb, they tap the tree trunk
0:07:15 > 0:07:18to listen out for hollow cavities
0:07:18 > 0:07:20that might just conceal a beehive.
0:07:20 > 0:07:22BUZZING INSECTS
0:07:22 > 0:07:26Whilst bee stings would harm most animals, sun bears' skin
0:07:26 > 0:07:29is protected by an incredibly thick fur.
0:07:36 > 0:07:41But one of the few places they don't have fur, is on their feet.
0:07:41 > 0:07:44Naked soles give them a better grip as they climb.
0:07:46 > 0:07:50And with an extra long tongue - almost 25 centimetres long -
0:07:50 > 0:07:53they can not only reach the honey,
0:07:53 > 0:07:57but also the protein-rich larvae deep inside the hive.
0:07:58 > 0:08:02The bears in the tropics have a specialised anatomy
0:08:02 > 0:08:05which allows them to reach the richest food
0:08:05 > 0:08:08in the most inaccessible places.
0:08:08 > 0:08:10And although this is a challenge,
0:08:10 > 0:08:13at least their food is available
0:08:13 > 0:08:14all year round.
0:08:19 > 0:08:21North America -
0:08:22 > 0:08:25bountiful summers,
0:08:25 > 0:08:28followed by bleak winters.
0:08:28 > 0:08:33In seasonal climates, food supply is dictated by time of the year,
0:08:33 > 0:08:37so to survive these periods of boom or bust,
0:08:37 > 0:08:40bears need more than physical adaptations.
0:08:40 > 0:08:43What they need is intelligence.
0:08:50 > 0:08:53Grizzly bears have an incredible ability to anticipate
0:08:53 > 0:08:56the changing seasons.
0:08:59 > 0:09:03From fresh grass shoots in spring,
0:09:03 > 0:09:06to clams and berries in summer,
0:09:06 > 0:09:09the bears know exactly where and when
0:09:09 > 0:09:11to find the best food.
0:09:13 > 0:09:18August marks the arrival of one of the year's richest food hauls
0:09:18 > 0:09:22and it can be found in an unexpected location,
0:09:22 > 0:09:25more than 3,000 metres up,
0:09:25 > 0:09:28on the peaks of the Rocky mountains.
0:09:36 > 0:09:40These grizzly bears have come to seek it out.
0:09:44 > 0:09:46It's a long and arduous journey,
0:09:46 > 0:09:49but they make this pilgrimage
0:09:49 > 0:09:51at the same time every year
0:09:51 > 0:09:53for a very good reason.
0:09:57 > 0:10:00Hidden under these barren rocks
0:10:00 > 0:10:03is an abundant supply of food.
0:10:05 > 0:10:08Tiny packets of protein and fat.
0:10:13 > 0:10:15Moths...
0:10:15 > 0:10:17in their millions.
0:10:17 > 0:10:20The bears have learned, and remembered,
0:10:20 > 0:10:23that for a short period of time each year,
0:10:23 > 0:10:26moths roost beneath these boulders.
0:10:28 > 0:10:32During the day, they're less active and easier to catch.
0:10:34 > 0:10:37Whilst they might seem like a tiny meal for such a large animal...
0:10:39 > 0:10:44..a bear can devour up to 40,000 moths in a single day.
0:10:47 > 0:10:51And that's 20,000 calories.
0:10:53 > 0:10:56Their knowledge is passed onto their cubs,
0:10:56 > 0:10:59so generations of grizzlies return to the same spot
0:10:59 > 0:11:02in the same month, year after year.
0:11:04 > 0:11:08Grizzlies anticipate the changing seasons and lean times ahead.
0:11:09 > 0:11:12As summer draws to a close,
0:11:12 > 0:11:14there's one last opportunity
0:11:14 > 0:11:16to stock up before winter.
0:11:29 > 0:11:33They begin to gather near the coast
0:11:33 > 0:11:36searching out a prime position.
0:11:44 > 0:11:50And this is what they've been waiting for - salmon
0:11:50 > 0:11:53returning to spawn in their thousands.
0:11:55 > 0:11:59These bears are first in line for a nutritious catch.
0:12:15 > 0:12:18Triggered by hormonal changes,
0:12:18 > 0:12:21the grizzly bears now enter a phase of hyperphagia.
0:12:23 > 0:12:27This allows them to eat constantly for up to 20 hours a day,
0:12:27 > 0:12:29without ever feeling full.
0:12:30 > 0:12:35They can consume up to 100,000 calories in a single day.
0:12:38 > 0:12:41And given the abundance of salmon,
0:12:41 > 0:12:43they can afford to be picky.
0:12:49 > 0:12:51Just like the bears in the tropics,
0:12:51 > 0:12:55they seek out the highest form of energy,
0:12:55 > 0:12:59selecting only the fat-rich eggs,
0:12:59 > 0:13:01the skin, and brain of the fish.
0:13:02 > 0:13:06In open water, it's not always easy.
0:13:11 > 0:13:14But as the salmon move further upstream...
0:13:15 > 0:13:18..the grizzlies are here, too.
0:13:22 > 0:13:26Where the river narrows it will be easier to land a catch.
0:14:01 > 0:14:05The salmon run is the very last chance to fatten up.
0:14:08 > 0:14:10But only bears that have eaten well enough
0:14:10 > 0:14:12will stand any chance at all
0:14:12 > 0:14:15of surviving the unforgiving winter.
0:14:16 > 0:14:21Up until now, their intelligence has seen them through,
0:14:21 > 0:14:25but at this point, it's imperative that their physiology takes over.
0:14:42 > 0:14:44As winter closes in,
0:14:44 > 0:14:48there are few foraging opportunities left to exploit.
0:14:58 > 0:15:02Now the bears' metabolism transforms
0:15:02 > 0:15:04to survive without food,
0:15:04 > 0:15:08and they enter hibernation.
0:15:12 > 0:15:13By mid-January,
0:15:13 > 0:15:18temperatures can plummet as low as minus 20 degrees centigrade.
0:15:21 > 0:15:25But beneath the frozen surface, in its den,
0:15:25 > 0:15:29a grizzly's body temperature is around 35 degrees.
0:15:30 > 0:15:34The substantial fat reserves built up over the summer
0:15:34 > 0:15:37act as fuel for heat generation.
0:15:39 > 0:15:41As fat is broken down,
0:15:41 > 0:15:44the cholesterol content of the bear's blood surges.
0:15:46 > 0:15:49It's not yet fully understood,
0:15:49 > 0:15:52but somehow the bears' sophisticated physiology
0:15:52 > 0:15:56means that they can withstand high levels of cholesterol
0:15:56 > 0:15:58without any risk of heart disease.
0:16:00 > 0:16:07During its slumber, a bear won't eat, urinate or defecate.
0:16:07 > 0:16:10Instead, it recycles the nitrogen
0:16:10 > 0:16:13that would otherwise be excreted,
0:16:13 > 0:16:16and uses it to rebuild wasting muscles.
0:16:18 > 0:16:23This continual process, over the course of months,
0:16:23 > 0:16:27ensures that they emerge fit, healthy
0:16:27 > 0:16:30and ready to feed again in the springtime.
0:16:47 > 0:16:52Incredibly, some bears will even give birth whilst hibernating.
0:16:57 > 0:17:01These cubs are taking their first steps into the world.
0:17:04 > 0:17:07For the mother, it's a triumph of survival.
0:17:11 > 0:17:15She has starved herself for almost six months,
0:17:15 > 0:17:17and lost a third of her bodyweight.
0:17:19 > 0:17:23The priority now is to find food again.
0:17:28 > 0:17:31Hibernation is a crucial physiological solution
0:17:31 > 0:17:35to surviving the boom and bust of the seasons.
0:17:36 > 0:17:41But one species of bear has a completely different strategy.
0:17:44 > 0:17:48Its physiology has evolved
0:17:48 > 0:17:50so it doesn't need to hibernate, at all.
0:17:52 > 0:17:54The Giant Panda.
0:18:02 > 0:18:05They feed almost exclusively on bamboo.
0:18:10 > 0:18:14The cellulose in bamboo is difficult to break down...
0:18:15 > 0:18:19..but pandas have a unique set of gut bacteria
0:18:19 > 0:18:21which produce the enzymes necessary
0:18:21 > 0:18:24to digest the tough plant matter...
0:18:25 > 0:18:27..and release energy.
0:18:31 > 0:18:35They are the only vegetarian species of bear,
0:18:35 > 0:18:38and have even lost the ability to taste meat.
0:18:40 > 0:18:44The genes for that switched off four million years ago.
0:18:49 > 0:18:54Pandas have evolved to become bamboo specialists.
0:18:57 > 0:19:00In the Qinling mountains of China, food is abundant
0:19:00 > 0:19:03and available all year,
0:19:03 > 0:19:07so the pandas can keep feeding throughout the seasons.
0:19:09 > 0:19:13They are the only temperate bear species
0:19:13 > 0:19:16that doesn't hibernate during cold winters.
0:19:19 > 0:19:20Across the planet,
0:19:20 > 0:19:25bears are able to take advantage of almost any feeding opportunity.
0:19:25 > 0:19:28Specialised anatomy, highly developed intelligence
0:19:28 > 0:19:30and a unique physiology,
0:19:30 > 0:19:32all play their part.
0:19:32 > 0:19:36But how does this superb opportunist cope
0:19:36 > 0:19:39when it's faced with one of the bleakest habitats on Earth?
0:19:47 > 0:19:49The Arctic.
0:19:51 > 0:19:57This vast icy wilderness spans 15 million square kilometres.
0:19:59 > 0:20:03Temperatures can plummet to minus 50 degrees centigrade.
0:20:06 > 0:20:08And for five long months,
0:20:08 > 0:20:10the sun doesn't rise.
0:20:13 > 0:20:17Few mammals can tolerate this winter wasteland.
0:20:21 > 0:20:24But one bear species has the senses,
0:20:24 > 0:20:29physiology and anatomy to reign supreme.
0:20:33 > 0:20:36At up to 700kg, the polar bear
0:20:36 > 0:20:38is the biggest of the bears
0:20:38 > 0:20:41with the highest energy demand.
0:20:41 > 0:20:43For every day it doesn't eat,
0:20:43 > 0:20:46it will lose a kilo in weight.
0:20:49 > 0:20:53Feeding opportunities are so sparsely distributed
0:20:53 > 0:20:55over this vast landscape
0:20:55 > 0:20:58that a single polar bears' range
0:20:58 > 0:21:02can span 300,000 square kilometres.
0:21:06 > 0:21:11Over these distances, with few visual clues,
0:21:11 > 0:21:14the polar bear has an incredible ability to seek out food.
0:21:17 > 0:21:21They have one of the most powerful noses in the animal kingdom...
0:21:21 > 0:21:24THE BEAR SNIFFS
0:21:24 > 0:21:29..able to identify a scent from over 30km away.
0:21:32 > 0:21:37And they can even detect what lies concealed beneath the ice.
0:21:41 > 0:21:43With the sea frozen over,
0:21:43 > 0:21:47ringed seals rely on air holes to breathe.
0:21:49 > 0:21:52But the bears can sniff these out,
0:21:52 > 0:21:55even when they're covered in a metre of snow.
0:22:02 > 0:22:06Polar bears are the most carnivorous of the bears.
0:22:07 > 0:22:11But they aren't interested in devouring the meat.
0:22:11 > 0:22:15Digesting that could lead to a build-up of nitrogen,
0:22:15 > 0:22:18and to excrete the nitrogen the bears would need to drink water.
0:22:20 > 0:22:23But the only fresh water here is the snow,
0:22:23 > 0:22:26and consuming the snow
0:22:26 > 0:22:28would lower the core body temperature of the bear.
0:22:31 > 0:22:36So instead, they concentrate on the energy-rich blubber...
0:22:40 > 0:22:44..absorbing almost 97% of the fat they consume.
0:22:47 > 0:22:53They have evolved to be obese, yet suffer no ill effects.
0:23:00 > 0:23:04But how do polar bears endure the brutal Arctic winter?
0:23:06 > 0:23:09As the days shorten, the weather closes in.
0:23:12 > 0:23:15Just like grizzly bears,
0:23:15 > 0:23:19females with cubs go into hibernation at this time,
0:23:19 > 0:23:22but remarkably the males don't.
0:23:23 > 0:23:27For them, winter offers the best feeding opportunities,
0:23:27 > 0:23:30so in almost total darkness,
0:23:30 > 0:23:33they battle through the bitterly cold winds.
0:23:35 > 0:23:37But without the warmth of the sun,
0:23:37 > 0:23:40it's a challenge to maintain a critical body temperature
0:23:40 > 0:23:42of 37 degrees.
0:23:44 > 0:23:48The polar bears' dense fur certainly plays a part -
0:23:48 > 0:23:52with up to 1,600 hairs per square centimetre,
0:23:52 > 0:23:55it's a fantastic insulating layer.
0:23:55 > 0:23:58But a recent discovery has revealed
0:23:58 > 0:24:02it's actually the fur's colour, or rather the lack of it,
0:24:02 > 0:24:04that keeps the bears warm.
0:24:06 > 0:24:11Appearing white, each hair is actually hollow and transparent.
0:24:12 > 0:24:15With no pigment to absorb colour,
0:24:15 > 0:24:18they reflect back the entire spectrum of light,
0:24:18 > 0:24:21including the invisible wavelengths
0:24:21 > 0:24:24such as infrared radiation, or heat.
0:24:26 > 0:24:30The polar bears' warm body gives off infrared waves,
0:24:30 > 0:24:33which radiate out from the skin's surface.
0:24:33 > 0:24:38This valuable warmth could be lost to the elements,
0:24:38 > 0:24:40but when the waves hit a hair filament,
0:24:40 > 0:24:44they're bounced straight back onto the bears black skin
0:24:44 > 0:24:46to be reabsorbed.
0:24:49 > 0:24:53Trapping and recycling body heat in this way,
0:24:53 > 0:24:56means that the polar bear is able to keep warm
0:24:56 > 0:24:58when there's no sun,
0:24:58 > 0:25:02and hunt for seals throughout the winter.
0:25:12 > 0:25:15By May, days are getting longer.
0:25:15 > 0:25:17Temperatures are rising.
0:25:19 > 0:25:21The sea ice begins to melt.
0:25:25 > 0:25:28For most animals, the change in season is welcome respite
0:25:28 > 0:25:30from the Arctic winter.
0:25:32 > 0:25:35But not the polar bear.
0:25:37 > 0:25:38With the sea ice gone,
0:25:38 > 0:25:41seals are largely out of their reach.
0:25:44 > 0:25:46As the ice breaks up,
0:25:46 > 0:25:50they're forced to take to water more and more often.
0:25:53 > 0:25:56They can be at sea for 10 days...
0:26:01 > 0:26:04..swimming for hundreds of kilometres.
0:26:08 > 0:26:10And when they reach dry land,
0:26:10 > 0:26:13energy-rich food here
0:26:13 > 0:26:15is even scarcer than on the ice.
0:26:17 > 0:26:20So during the summer months,
0:26:20 > 0:26:22their physiology changes.
0:26:24 > 0:26:26Faced with starvation,
0:26:26 > 0:26:30polar bears could reverse the hibernation strategy of their cousins,
0:26:30 > 0:26:34and sleep through the lean summer,
0:26:34 > 0:26:37but that would mean missing out on potential food.
0:26:40 > 0:26:46So instead, they have devised a remarkable alternative -
0:26:46 > 0:26:48they hibernate whilst awake.
0:26:53 > 0:26:55With scant feeding opportunities,
0:26:55 > 0:27:00polar bears start recycling nitrogen to maintain their muscles,
0:27:00 > 0:27:03just as hibernating grizzly bears do.
0:27:06 > 0:27:10The difference is, that during this hibernation
0:27:10 > 0:27:12polar bears remain alert.
0:27:14 > 0:27:17So if they DO happen on a meal,
0:27:17 > 0:27:20however small - like this seaweed -
0:27:20 > 0:27:24they can switch off the recycling process of hibernation
0:27:24 > 0:27:27to take in new nutrients and new energy.
0:27:31 > 0:27:36This process of walking hibernation
0:27:36 > 0:27:39appears to be exclusive to polar bears,
0:27:39 > 0:27:43but its precise mechanism is not yet fully understood.
0:27:52 > 0:27:55In their quest for the finest quality foods,
0:27:55 > 0:27:59bears can reach the most inaccessible places,
0:27:59 > 0:28:02they can survive times of boom and bust,
0:28:02 > 0:28:05and even succeed in some of the planet's
0:28:05 > 0:28:08most inhospitable environments.
0:28:09 > 0:28:12Their extraordinary intelligence,
0:28:12 > 0:28:15anatomy and physiology
0:28:15 > 0:28:19mean they can take advantage of any habitat they find themselves in.
0:28:19 > 0:28:22These animals can thrive
0:28:22 > 0:28:25where few other species can even survive.
0:28:27 > 0:28:30And that is the wonder of bears.