NARRATOR: IT'S SUMMER IN THE ARCTIC.

THE SEA ICE IS BREAKING UP.

AND AFTER A LONG SWIM, POLAR BEARS ARE EMERGING AT A REMOTE NORTH ALASKAN BEACH.

[GROWLS] AMONG THEM IS A BEAR CALLED ANYU AND HER TWO CUBS.

SOON THEY ARE JOINED BY UPWARDS OF 80 POLAR BEARS.

THEY ARE HERE FOR AN EXTRAORDINARY FEAST.

[GROWLING] MAN: YOU CAN'T LOOK AT THIS AND EVER THINK ABOUT POLAR BEARS IN THE SAME WAY AGAIN.

NARRATOR: THE POLAR BEAR IS A SOLITARY ANIMAL.

FOR IT TO GATHER HERE IN SUCH A LARGE GROUP IS UNPRECEDENTED.

AND EACH YEAR, MORE BEARS ARE ARRIVING, BRINGING HUMANS AND POLAR BEARS INTO INCREASING CONTACT.

WOMAN: THE POLAR BEAR'S JUST A BEAUTIFUL ANIMAL.

VERY SCARY.

[GROWLING] NARRATOR: BY STUDYING THIS GATHERING OF THE BEARS, SCIENTISTS HAVE A UNIQUE OPPORTUNITY TO BETTER UNDERSTAND THIS MYSTERIOUS ANIMAL AND ITS FUTURE.

NARRATOR: IT'S LATE SUMMER ON THE COAST OF NORTHERN ALASKA.

THIS IS THE SOUTHERN BEAUFORT SEA-- HOME TO ONE OF THE WORLD'S 19 POLAR BEAR POPULATIONS.

WHEN THEY WERE LAST COUNTED IN 2006, 1,500 BEARS WERE KNOWN TO LIVE HERE.

BUT THEIR NUMBERS APPEAR TO BE DROPPING.

SCIENTISTS ARE TRYING TO FIND OUT WHY.

ONE OF THE BEARS IS A FEMALE CALLED ANYU.

MAN: TO THE BEST OF OUR KNOWLEDGE, SHE'S PROBABLY A 13-, 14-YEAR-OLD BEAR.

NARRATOR: SHE'S A MOTHER OF TWO 18-MONTH-OLD CUBS-- TIKAANI AND MALINA.

WE KNOW THAT'S SHE HAD TWO SUCCESSFUL LITTERS, SO, SHE APPEARS TO BE A PRETTY GOOD MOM.

NARRATOR: ANYU HAS TRAVELED ACROSS HUNDREDS OF MILES OF SEA ICE AND OPEN WATER TO THIS PLACE-- KAKTOVIK.

A TINY AND REMOTE COASTAL VILLAGE, IT'S OVER 600 MILES NORTH OF ALASKA'S MAIN CITY, ANCHORAGE.

ALONGSIDE ANYU AND HER CUBS, A LARGE CROWD OF BEARS BEGINS TO ASSEMBLE.

IT'S AS IF THEY KNOW SOMETHING IS ABOUT TO HAPPEN.

[CROWD CHEERING] NARRATOR: A JUBILANT CROWD GATHERS ON THE BEACH TO CELEBRATE.

THE CAPTURE OF A BOWHEAD WHALE.

WHALES ARE PROTECTED BY INTERNATIONAL LAW, BUT THE INDIGENOUS INUPIAT PEOPLE OF KAKTOVIK ARE ALLOWED TO LAND 3 EVERY SUMMER.

THE WHOLE TOWN IS OUT.

THIS IS THE EVENT OF THE YEAR.

MAN: I MEAN, EVERYBODY'S JUST HAPPY AND ECSTATIC AND--I MEAN, I GET A LUMP IN MY THROAT EVERY TIME WE BRING IN A WHALE.

NARRATOR: THE POLAR BEARS STARTED GATHERING OVER A WEEK AGO, MAKING A TEMPORARY HOME ON AN ISLAND CLOSE TO THE VILLAGE.

NOW A HUGE CROWD OF THEM IS MILLING AROUND-- ENORMOUS MALES, FEMALES, AND THEIR CUBS.

IT'S A MASSIVE AND STRANGE CHANGE IN POLAR BEAR BEHAVIOR.

MAN: 40 YEARS AGO, TO SEE A BEAR WAS AN EVENT.

IT WAS SOMETHING.

WOW, WE SAW A BEAR.

BUT NOW THERE'S 80 TO 100 HERE RIGHT NOW.

THERE'S PROBABLY MORE COMING.

NARRATOR: WHAT'S BRINGING THEM HERE IS THIS-- THE KAKTOVIK WHALE BONE PILE.

FOR THE PAST 20 YEARS, THE INUPIAT HAVE LEFT REMAINS OF WHALES FOR THE BEARS ON THIS SPOT.

SOON, THIS ONE WILL BE OFFERED UP TO THE BEARS.

IN ACCORDANCE WITH INUPIAT TRADITION, THE WHALE'S SPIRIT IS GIVEN A FINAL DRINK OF WATER AS IT DEPARTS FOR THE AFTERLIFE.

BROWER: WE'RE NOT JUST DOING IT JUST FOR THE THRILL OF THE HUNT, WE'RE DOING IT TO FEED A COMMUNITY AND OUR FAMILIES.

NARRATOR: THE BOWHEAD WHALE CAN GROW UP TO 60 FEET LONG AND REACH AN AGE OF MORE THAN 150 YEARS.

[INDISTINCT CHATTER] IN A WORLD OF DIESEL ENGINES, BROADBAND, AND SATELLITE TV, THIS IS ONE OF THE FEW WAYS THE VILLAGERS CONNECT TO THEIR PAST AS ARCTIC HUNTER-GATHERERS.

FOR A TINY TOWN LIKE KAKTOVIK, SEEMINGLY PERCHED ON THE EDGE OF THE WORLD, THESE TRADITIONS ARE DEEP-ROOTED.

MAN: WE'RE STILL ALMOST STONE AGE UP HERE.

I MEAN, YEAH, WE'VE GOT MODERN TECHNOLOGY, BUT WE USE WHAT'S AVAILABLE TO US.

THAT'S THE WAY WE'VE ALWAYS BEEN.

NARRATOR: HUNTING OF BIG GAME LIKE CARIBOU AND THE TAKING OF MASSIVE WHALES LIKE THE BOWHEAD HAS KEPT THIS TINY COMMUNITY OF JUST OVER 200 CONNECTED TO THE ANCIENT PAST.

BROWER: WHEN A WHALE IS CAUGHT, TO ME IT'S LIKE A SPIRITUAL CONNECTION THAT WE HAVE WITH THE WHALES.

SIMMS: OUR BELIEF IS YOU TAKE WHAT YOU NEED, YOU KNOW.

YOU DON'T GO TAKE 30 CARIBOU IF YOU DON'T NEED 30 CARIBOU, YOU KNOW?

WE ARE THE CARETAKERS OF THIS LAND.

IF YOU TAKE CARE OF THE LAND, THE LAND WILL TAKE CARE BACK.

NARRATOR: FOR LOCAL EDDIE REXFORD, RESPECT FOR THE ANIMALS THAT SHARE THEIR WORLD IS PART OF WHAT IT MEANS TO BE INUPIAT.

BEING RAISED IN THIS, UH, CULTURE, THAT WE RESPECT ALL ANIMALS AND WE CONSIDER THEM OUR RELATIVES, THE POLAR BEARS.

NARRATOR: OFFERING A SHARE OF THE WHALE TO THE POLAR BEAR COMES NATURALLY TO THE INUPIAT.

AS SOON AS THE WHALE IS LANDED, IT'S BUTCHERED ON THE BEACH BEFORE THE MEAT GETS A CHANCE TO SPOIL.

WE DEPEND ON THEM PRETTY MUCH ALL, ALL WINTER LONG.

OK.

I'M JUST GONNA DO IT THIS WAY.

BROWER: IT SUSTAINS US, KEEPS US WARM IN THE COLD, FRIGID WEATHERS.

[INDISTINCT CHATTER] IT HAS A REALLY BIG CULTURAL SIGNIFICANCE IN HOW OUR PEOPLE LIVE TOGETHER.

IT TAKES US ALL TO CATCH ONE AND THERE'S A LOT THAT GOES INTO HOW IT'S DONE, HOW'S ITS DIVIDED, HOW IT'S SHARED OUT.

NARRATOR: COMMUNAL FEASTING BRINGS THE PEOPLE OF KAKTOVIK TOGETHER OVER A HOT PLATE OF BRAISED WHALE BLUBBER.

MEANWHILE, THE REMAINS OF THE WHALE CARCASS ARE DRAGGED TO THE BONE PILE, ONE MILE FROM THE EDGE OF TOWN.

AND THE POLAR BEARS JOIN THE FESTIVITIES.

[GROWLING] FOR THE LOCALS, THE POLAR BEAR FEAST IS SOMETHING TO BE PROUD OF.

WITH MORE POLAR BEARS COMING EACH YEAR, KAKTOVIK IS NOW FIRMLY ON THE MAP.

WOMAN: WHEN YOU FIRST SEE A BUNCH OF BEARS OR THE FIRST POLAR BEAR, IT'S EXCITING AND, YOU KNOW, EVERYBODY WANTS TO COME OUT AND SEE THEM.

WE SIT OUT THERE IN OUR VEHICLES AND JUST WATCH THE BEARS.

THE POLAR BEAR IS JUST SUCH A BEAUTIFUL ANIMAL.

VERY SCARY!

[HORN HONKS] [ENGINE REVVING] [HORN HONKS] [BIRD SQUAWKING] NARRATOR: IT'S AN INCREDIBLE SIGHT, BUT THERE'S MORE TO IT THAN MEETS THE EYE.

WOMAN: WE THINK OF POLAR BEARS AS SOLITARY BECAUSE IN FACT THEY ARE SOLITARY FOR MOST OF THE YEAR, BUT HERE WE SEE THIS INCREDIBLE CONCENTRATION OF POLAR BEARS.

I MEAN, THERE ARE UPWARDS OF PROBABLY 80 BEARS IN THIS INCREDIBLY SMALL AREA, AND THIS IS ALL ABOUT THIS INCREDIBLY CONCENTRATED, HIGH-VALUE FOOD SOURCE.

NARRATOR: AT THE SAN DIEGO ZOO, DR. MEGAN OWEN OVERSEES RESEARCH INTO THE ECOLOGY AND CONSERVATION OF POLAR BEARS.

OWEN: THE ARCTIC IS SUCH AN INCREDIBLY DEMANDING ENVIRONMENT.

IT'S ALWAYS HARSH AND COLD.

SO, POLAR BEARS HAVE REALLY EVOLVED A TREMENDOUS COGNITIVE CAPACITY.

THEIR INTELLIGENCE IS NECESSARY TO SURVIVE IN THAT ENVIRONMENT.

THIS CAPACITY TO NAVIGATE THIS SOCIAL DYNAMIC IS GOING TO BECOME A REALLY IMPORTANT PART OF THEIR SURVIVAL.

ALL OF THE CALORIES THEY'RE GAINING WHILE THEY'RE AT THIS CARCASS ARE GOING TO BE EXTREMELY IMPORTANT FOR THEM AS THE YEAR ROLLS ON.

NARRATOR: FOR MEGAN AND OTHER SCIENTISTS, THE BONE PILE IS A GREAT FOOD SOURCE, BUT IT'S BRINGING POLAR BEARS INTO A STRANGE AND UNPREDICTABLE SITUATION.

THIS IS A CUB THAT'S NURSING WITH HIS MOM.

THE MOM, SHE'S GOT HER HEAD UP, SHE'S SNIFFING AROUND, SHE'S ALWAYS ON THE LOOKOUT, MAKING SURE THERE'S NOT ANOTHER BEAR THAT'S GOING TO THREATEN HER AND HER CUB WHILE SHE'S THERE.

NEVER--NEVER A MOMENT OF DOWNTIME FOR A POLAR BEAR MOM, ESPECIALLY IN A SITUATION LIKE THIS WHERE THERE'S SO MANY POLAR BEARS IN PROXIMITY.

GETTING ENOUGH FOOD IS LIFE OR DEATH FOR A MOTHER AND HER CUBS.

SHE'S BRINGING HER CUBS IN PROXIMITY TO OTHER BEARS, AND SO, IT REQUIRES TREMENDOUS SOCIAL FINESSE.

[BIRDS SQUAWKING] MAN: THIS IS THE EXACT OPPOSITE OF EVERYTHING THAT I'VE EVER KNOWN ABOUT THE BEARS.

[GROWLING] YOU CAN'T LOOK AT THIS AND EVER THINK ABOUT POLAR BEARS THE SAME WAY AGAIN.

NARRATOR: CINEMATOGRAPHER ARTHUR C. SMITH MOVED TO KAKTOVIK IN 2006.

DRAWN HERE BY THEIR INCREASING NUMBERS, ARTHUR HAS BEEN FILMING THE POLAR BEAR FOR ALMOST A DECADE.

FOR HIM, THIS GATHERING CHALLENGES THE ACCEPTED WISDOM ABOUT THE NATURE OF THE POLAR BEAR.

SMITH: IF YOU WERE TO READ AN ACCOUNT OF HOW POLAR BEARS ARE CHARACTERIZED-- SOLITARY, BLOODTHIRSTY KILLERS-- THEN TO WATCH HOW THEY BEHAVE HERE, IT'S LIKE YOU WOULDN'T BELIEVE THAT YOU WERE ON THE SAME PLANET.

AND THAT BECOMES THE QUESTION-- WHERE DID THIS COME FROM?

NARRATOR: EVERY YEAR, MORE AND MORE BEARS LIKE ANYU ARE TURNING UP AT THE BONE PILE IN SEARCH OF FOOD.

FOR MEGAN, THIS COLLISION OF SO MANY POLAR BEARS IN ONE TINY PLACE REVEALS THE TRUE COMPLEXITY OF POLAR BEAR BEHAVIOR.

AT THE BONE PILE, THE SECRET SIGNS OF CONFLICT ARE VISIBLE TO HER TRAINED EYE.

OWEN: SO, HERE COMES A FEMALE WHO'S GOT A TRACKING COLLAR ON.

SHE IMMEDIATELY WENT FOR THE FOOD THAT WAS THERE AND GOT INTO AN AGGRESSIVE BOUT WITH THIS OTHER FEMALE, AND THAT MOUTH SPARRING, WE CALL IT MOUTH FENCING, BACK AND FORTH, MOUTH WIDE OPEN, TEETH DISPLAYED, WHICH REALLY COULD INFLICT DRAMATIC INJURY TO THE OTHER BEAR.

BUT IT'S ALL SORT OF MEASURED, AND THERE'S ONLY A LIMITED AMOUNT OF CONTACT, AND THE HOPE HERE IS THAT THEY CAN BASICALLY SHOW, BY HOW POWERFUL AND AGGRESSIVE THEY ARE, THAT IF THE OTHER BEAR CONTINUES TO FIGHT, THEY'RE GOING TO LOSE.

[GROWLING] BARING TEETH IS A REALLY IMPORTANT PART OF THESE TYPES OF AGGRESSIVE SOCIAL ENCOUNTERS.

WE DO FIND THAT ADULT FEMALES WITH CUBS ARE SOME OF THE MOST AGGRESSIVE BEARS OUT THERE IN THESE SOCIAL GROUPS.

GETTING ENOUGH CALORIES IN IS JUST ESSENTIAL FOR THE SURVIVAL OF THE MOTHER AND PROBABLY MORE IMPORTANT, THE SURVIVAL OF HER CUBS.

NARRATOR: AS MORE BEARS TURN UP YEAR ON YEAR, THE ENIGMA OF THE BONE PILE GROWS.

IT SEEMS THAT POLAR BEARS ARE CREATING A NEW HABITAT HERE ON THE BEACH.

WHY?

AND WHAT WILL IT MEAN FOR THE FUTURE?

TO FIND OUT WHAT IS HAPPENING TO THE BEARS, SCIENTISTS ARE STUDYING POLAR BEARS IN THEIR NATURAL HABITAT OUT ON THE SEA ICE.

IT'S MARCH 2014 AND A RESEARCH TEAM FROM THE U.S. GEOLOGICAL SURVEY, LED BY DR. TODD ATWOOD, IS PREPARING TO FLY OUT OVER THE COASTAL SEA ICE.

NOW, THE HELICOPTER CONTACT NUMBER IS 8816.

ATWOOD: WE ALWAYS HAVE FANTASTIC PILOTS WHO ARE VERY ADEPT AT FLYING LOW AND FLYING SLOW, WHICH IS VERY HARD TO DO.

NARRATOR: THEIR MISSION--TO CAPTURE AND TAG A POLAR BEAR.

WE DON'T WANT TO BE SHOOTING TOO MUCH LATERALLY, YEAH.

AND WE'RE AIMING FOR THE SHOULDERS.

OUR SATELLITE COLLARS WITH ACCELEROMETERS.

[INDISTINCT VOICES ON RADIO] NARRATOR: THE TEAM SCOURS THE COASTAL SEA ICE FOR FRESH BEAR TRACKS.

MAN ON RADIO: THERE WAS A BEAR SPOTTED THERE AROUND MIDNIGHT.

MAN 2 ON RADIO: GONNA SEE IF WE CAN FIND THAT FEMALE.

THERE'S ANOTHER SET OF TRACKS THERE.

THERE SHE IS.

SHE'S THERE.

MAN ON RADIO: NICE.

SHOULD BE A SECOND ONE SOMEWHERE.

NARRATOR: ONCE ON THE TRAIL, TODD MEASURES OUT THE RIGHT DOSE OF TRANQUILIZER TO SAFELY TAKE DOWN A HALF-TON BEAR.

MAN ON RADIO: GONNA HAVE TO TAKE THE DART OUT, GO BACK TO HER AFTER WE MARK HER.

MAN 2: OK.

COPY THAT.

THE HELICOPTER ALMOST WORKS LIKE A HERDING DOG.

IT KEEPS THE BEAR IN A SAFE AREA SO THAT IT GOES DOWN NICE AND EASY IN ICE THAT WE CAN WORK WITH THE BEAR ON.

[INDISTINCT VOICE ON RADIO] MAN ON RADIO: YEAH, SHE'S AT OUR 5:00.

MAN ON RADIO: BEAR'S ABOUT 400-SOMETHING POUNDS.

WE FOUND THEM ON THE FIRST DAY OUT HERE.

ATWOOD: ONCE WE SEE THE HEAD GO DOWN, THEN WE FEEL IT'S SAFE TO LAND.

IF WE'RE NOT SEEING ANY HEAD SWING OR ANY UP AND DOWN HEAD MOVEMENT, THEN WE HAVE A PRETTY GOOD BET THAT THIS BEAR IS, IS IN FACT FULLY IMMOBILIZED.

AT THAT POINT, WE'LL GO AND APPROACH THE BEAR.

NARRATOR: WITH THE BEAR FULLY SEDATED AND HER TWO YOUNG CUBS RETRIEVED AND UNDER CONTROL, THE TEAM GET TO WORK.

ALTHOUGH IT MAY LOOK UNCOMFORTABLE FOR THE BEAR, NO HARM WILL COME TO IT.

SCIENTISTS LIKE TODD HAVE BEEN NOTICING WORRYING TRENDS IN THE BEARS' HEALTH AS CONDITIONS IN THE ARCTIC CHANGE SWIFTLY.

ATWOOD: WE ARE CONCERNED THAT THE RAPID ENVIRONMENTAL CHANGE THAT'S HAPPENING IN THE SOUTHERN BEAUFORT IS CAUSING POLAR BEARS TO SUFFER DECLINING BODY CONDITION, IMPAIRING SURVIVAL.

NARRATOR: WORKING AGAINST THE CLOCK, TODD AND HIS COLLEAGUES COLLECT VITAL BIOLOGICAL INFORMATION FROM THE BEAR.

I'M SORRY, DUDE.

YOU'RE GETTING THE BONUS TREATMENT TODAY, THOUGH.

SO, THE BLOOD THAT WE COLLECT REALLY PROVIDES A LOT OF USEFUL INFORMATION ON WHETHER THESE BEARS HAVE BEEN FASTING FOR EXTENDED PERIODS OF TIME.

MAN: READY?

PERFECT.

[CLICK] [GROWLS] [BEEP] ATWOOD: WHAT WE JUST DID HERE WAS IMPLANT A MICROCHIP IDENTIFICATION DEVICE BEHIND THE EAR OF THE BEAR, SAME TYPE OF THING YOU WOULD DO FOR YOUR PET IN CASE IT GOT LOST, AND THIS WILL SERVE AS A UNIQUE IDENTIFIER FOR THE BEAR, SO, IN CASE WE CAPTURE IT AGAIN, WE'LL BE ABLE TO USE THE SCANNER AND SWIPE BEHIND THE EAR AND KNOW THAT THIS IS A BEAR THAT'S PROBABLY ALREADY IN OUR DATABASE.

NARRATOR: THE FINAL JOB FOR THE TEAM IS TO FIT GPS TRACKING COLLARS.

LIKE THE LOCATION DEVICE IN YOUR CELL PHONE, THIS TECHNOLOGY WILL ALLOW TODD TO ACCURATELY TRACK THE BEARS.

[GROWLING] SOME OF THE COLLARS EVEN HAVE CAMERAS ATTACHED TO THEM.

AND AFTER A YEAR OF SENDING DATA AND FOOTAGE, THE COLLARS WILL AUTOMATICALLY DROP OFF.

[GROWLING] WITHIN 30 MINUTES, THE BEAR WILL BE RECOVERED AND BACK WITH HER CUBS ONCE AGAIN.

[SNUFFLES] MAN: THE CAPTURE WORK WE DO IS REALLY IMPORTANT, REALLY GET AN UNDERSTANDING OF, OF WHAT HABITATS ARE ESSENTIAL FOR THESE ANIMALS.

THE COLLAR WORK THAT WE DO ALLOWS US TO UNDERSTAND HABITAT USE.

THE VIDEO COLLAR WORK THAT WE'RE DOING ALLOWS US TO UNDERSTAND SPECIFICALLY WHAT THE BEARS ARE DOING AT THESE HABITATS, AND WE CAN ALSO LOOK AT WHAT BEARS ARE DOING WHEN THE ICE IS BREAKING UP IN THE SPRING AND SUMMER, WHEN IT'S REACHING ITS MINIMUM IN, IN SEPTEMBER.

NARRATOR: THE COLLAR CAMS CAPTURE REMARKABLE FOOTAGE OF POLAR BEAR BEHAVIOR.

[GROWLING AND SNUFFLING] ATWOOD: THROUGH THAT PARSING OF MOVEMENT DATA AND BEHAVIORAL DATA DETECTED BY THOSE CAMERAS, WE CAN SEE HOW A BEAR IS NAVIGATING THROUGH A LANDSCAPE THAT'S MAYBE MORE FRAGMENTED, HOW MUCH TIME IT'S SPENDING SWIMMING... HOW SUCCESSFUL IT IS HUNTING.

NARRATOR: OVER THE PAST 5 YEARS, TODD'S TEAM HAS TRACKED OVER 60 BEARS.

ATWOOD: SO, THIS IS A MAP THAT SHOWS THE DISTRIBUTION OF OUR RADIO-COLLARED POLAR BEARS.

ALL OF THOSE LITTLE, INDIVIDUAL COLORED ICONS ARE COLLARED BEARS.

NARRATOR: AS WELL AS ANYU, TODD HAD PREVIOUSLY TRACKED A SECOND MOTHER CALLED NANOOK WITH A SINGLE CUB.

THE GPS COLLARS SHOWED THAT NEITHER ANYU NOR NANOOK AND THEIR CUBS HAD STRAYED MORE THAN 40 MILES NORTH OF THE COASTLINE IN THE MONTH OF MAY.

THEY'D STAYED ON THE ICE OVER THE SHALLOW COASTAL WATER FOR A VERY GOOD REASON.

THEY WERE HUNTING.

BEARS NEED AN AVERAGE OF 4 1/2 POUNDS OF BLUBBER PER DAY TO SURVIVE.

AND MOST OF THAT BLUBBER COMES FROM THE RING SEAL.

A RING SEAL, FOR EXAMPLE, CAN BE 50% FAT BY BODY WEIGHT, SO, THAT'S AN INCREDIBLY RICH SOURCE, AND THAT HAS ALLOWED POLAR BEARS TO BECOME THE LARGEST BEARS IN THE WORLD.

NARRATOR: TO FEED THEMSELVES AND THEIR CUBS, THEY MUST CATCH ON AVERAGE ONE SEAL EVERY WEEK.

ONLY BY BEING THE PERFECT AMBUSH PREDATORS COULD ANYU AND NANOOK ACHIEVE THIS FEAT.

TO CONSERVE VALUABLE ENERGY, THEY WAIT BY SEAL BLOW-HOLES FOR UP TO 6 HOURS AT A TIME.

THEY ARE INCREDIBLY POWERFUL PREDATORS.

POLAR BEAR SKULL IS MORE NARROW THIS WAY.

AN ADAPTATION TO STICKING YOUR HEAD INTO A HOLE TO TRY AND PULL THE SEAL OUT.

I'VE SEEN A POLAR BEAR GRAB A SEAL OUT OF A HOLE, LITERALLY BIT THE SEAL BY THE HEAD, AND SWING THE WHOLE SEAL UP OUT OF--IN THE AIR, AND THIS BIG ARC OF BLOOD GOES FLYING.

YOU KNOW, I MEAN, IT'S IT'S A PRETTY VIOLENT ACT.

ATWOOD: WHEN WE SEE POLAR BEAR-KILLED RING SEALS, IN MOST CASES POLAR BEARS ARE HIGH-GRADING THOSE RING SEALS, MEANING THEY'RE EATING MOSTLY THE FAT AND VERY LITTLE MUSCLE.

SO, A HAPPY POLAR BEAR IS A POLAR BEAR THAT'S CONSUMING A LOT OF FAT.

NARRATOR: IN JUNE AND EARLY JULY, THE GPS TRACKS SHOWED THAT NEARLY ALL THE BEARS WERE STILL NEAR THE COAST.

IT'S A TIME OF PLENTY.

AT KAKTOVIK, THE SEA ICE REACHES ALL THE WAY TO THE SHORE AND LIES OVER THE SHALLOW, FISH-PACKED WATERS OF THE COASTAL SHELF.

IT'S SHALLOW WATER, IT'S MORE BIOLOGICALLY PRODUCTIVE.

WHEN THERE'S ICE OVER THE TOP OF IT, POLAR BEARS IN THE SOUTHERN BEAUFORT ARE HAPPY.

NARRATOR: HUNTING IS NOT JUST A WAITING GAME.

OVER A SHORT DISTANCE, A POLAR BEAR CAN OUTRUN USAIN BOLT.

AT THE HEIGHT OF SUMMER, THE SEA ICE THAT THEY HUNT FROM IS STARTING TO MELT.

ATWOOD: JULY IS THE PERIOD OF TIME WHEN WE'RE KIND OF IN THE HEART OF THE BREAKUP SEASON, SO, WE'RE SEEING RAPID BREAKUP OF SEA ICE OVER THE CONTINENTAL SHELF.

IT'S BECOMING HIGHLY FRAGMENTED.

NARRATOR: THE SEA ICE BY THE COAST BEGINS TO MELT FIRST, BREAKING UP AND DISAPPEARING, LEAVING OPEN OCEAN.

POLAR BEARS ARE EXCELLENT SWIMMERS AND VERY ADAPTABLE.

BUT IN THE PAST FEW DECADES, THEY HAVE BEEN OUTPACED BY INCREASINGLY SEVERE SEA ICE LOSS IN THE SUMMER.

SATELLITE IMAGES REVEAL WHAT HAS BEEN HAPPENING TO THE ARCTIC SEA ICE.

THE EARLIEST OF THESE IMAGES TAKEN 35 YEARS AGO SHOWS THAT AT THE HEIGHT OF SUMMER, THE SEA ICE STILL REACHED NEARLY ALL THE WAY TO THE SHORE NEAR TO KAKTOVIK.

DR. STEVEN AMSTRUP HAS SPENT 30 YEARS STUDYING THE POLAR BEARS OF ALASKA.

IN THAT TIME, HE HAS SEEN REMARKABLE CHANGES IN THE ARCTIC SEA ICE.

WHEN I FIRST WENT TO ALASKA IN THE EARLY 1980s, I COULD STAND ON THE BEACH IN THE SUMMERTIME AND SEE THE SEA ICE.

THE SEA ICE RETREATED ONLY A FEW MILES OFFSHORE.

SOMETIMES, IF YOU WERE LUCKY, YOU COULD ACTUALLY SEE A POLAR BEAR OUT ON THE ICE, STANDING ON THE SHORE.

YOU COULD SEE IT ACROSS A LITTLE GAP OF WATER.

NARRATOR: BUT OVER THE DECADES, THIS CONTRACTION OF SUMMER SEA ICE HAS BECOME MUCH MORE PRONOUNCED.

SUMMER SEA ICE IS ON A DOWNWARD TREND.

AMSTRUP: NOW THE SEA ICE IS HUNDREDS OF MILES OFFSHORE IN THE SUMMERTIME.

IT'S BEYOND THE CURVATURE OF THE EARTH.

YOU CAN'T SEE THE ICE.

WE'VE SEEN A GREATER THAN 13% PER DECADE DECLINE IN THE SUMMER SEA ICE DURING MY WORKING CAREER.

THAT'S A HECK OF A LOT OF CHANGE.

NARRATOR: 30 YEARS AGO, WHEN SUMMER SEA ICE WAS CLOSE TO SHORE, IT LAY OVER SHALLOW COASTAL WATER.

THE WATER WAS FULL OF FISH AND THE POLAR BEARS' FAVORITE PREY, THE RING SEAL.

AMSTRUP: WE KNOW THAT POLAR BEARS ONLY PREDICTABLY CATCH SEALS FROM THE SEA ICE.

UH, ALL OF THE INFORMATION WE HAVE SUGGESTS THAT.

AND IF THERE ISN'T SEA ICE AROUND FOR A LONG ENOUGH PERIOD, THEN POLAR BEARS ARE IN TROUBLE.

NARRATOR: IN RECENT YEARS, WHEN SUMMER SEA ICE WAS HUNDREDS OF MILES OFFSHORE, IT WAS OVER DEEP WATER WITH FEWER FISH AND FEWER SEALS.

FOR STEVEN, THE SUSPICION IS THAT THERE ISN'T ENOUGH TO EAT OUT ON THE SUMMER SEA ICE.

AMSTRUP: IN THE BEAUFORT SEA, THE ABSENCE OF SEA ICE NEAR SHORE IS A NEW THING AND THE BEARS HAVE THIS CHOICE OF GOING OFFSHORE OR STAYING ON LAND, BUT THE IMPACT ON THE BEAR IS THE SAME.

IF THE ICE ISN'T THERE FOR THEM TO FEED, THEN THEY CAN'T GAIN ENOUGH WEIGHT.

NARRATOR: THE TRACKING DATA SHOWED THAT IN JULY, ANYU AND HER CUBS HAD BEEN HUGGING THE EDGE OF THE ICE NEAR THE SHORE.

BUT AS THE SUMMER SEA ICE RETREATS FURTHER AND FURTHER FROM THE SHORE EACH YEAR, BEARS LIKE ANYU AND NANOOK ARE FACED WITH A DIFFICULT AND MOMENTOUS CHOICE, FOR THEMSELVES, THEIR CUBS, AND, ULTIMATELY, THEIR SPECIES.

ATWOOD: THIS IS THE DECISION POINT FOR BEARS.

THIS IS WHERE THEY HAVE TO DECIDE THEY'RE EITHER GOING TO COME ASHORE, SPEND THE SUMMER ON SHORE, OR MOVE TO THE ICE AS IT RETRACTS OVER THE BASIN.

NARRATOR: AT FIRST, NANOOK AND HER CUB FOLLOW ANYU'S EXAMPLE AND STAY ON THE MAINLAND AS THE ICE RECEDES.

BUT THEN, SUDDENLY, NANOOK TAKES A DIFFERENT COURSE OF ACTION.

SHE FOLLOWS HER INSTINCTS AND DECIDES TO SWIM FOR THE ICE WITH HER CUB.

BUT SHE DOESN'T KNOW HOW FAR AWAY THE SEA ICE IS.

WHAT SHE'S DOING IS MAKING A LONG DISTANCE SWIM, IN THIS CASE FROM SHORE TO THE PACK ICE.

HERE SHE GOES.

SHE'S SWIMMING, SHE'S PAST THE, THE CONTINENTAL SHELF.

ALL TOLD, SHE'S PROBABLY COVERING ABOUT 600, 650 KILOMETERS.

SHE ALSO HAS A YEARLING IN TOW WITH HER, SO, SHE'S MAKING A SWIM THAT ALL TOLD TOOK ABOUT 10, 11 DAYS TO REACH THE PACK ICE.

SHE TRAVELED OVER 600 KILOMETERS IN THIS CONTINUOUS SWIM.

THESE BEARS WILL COVER ENORMOUS DISTANCES DURING THE COURSE OF A YEAR.

WITHIN THE OPEN WATER SEASON, THEY MIGHT SWIM SEVERAL HUNDRED KILOMETERS.

NARRATOR: FOR NANOOK AND HER CUB, WHAT ONCE WOULD HAVE BEEN A SHORT SWIM TO THE ICE WAS NOW MORE OF AN EPIC SEA CROSSING.

IT'S NOW SEPTEMBER.

WHILE NANOOK AND HER CUB WERE SWIMMING TO THE ICE, ANYU, WITH CUBS IN TOW, WAS CLINGING TO THE SHORELINE.

SHE ROAMED AS FAR EAST AS CANADA, THEN RETURNED TO THE VICINITY OF KAKTOVIK.

ATWOOD: YOU KNOW, WHAT WE'RE SEEING IN THE SOUTHERN BEAUFORT IS THAT THE PROPORTION THAT COMES ASHORE IS PROBABLY SOMEWHERE AROUND 20%, BUT IT'S GROWING, AND IT'S GROWN AN ORDER OF MAGNITUDE IN JUST THE LAST 10 TO 15 YEARS.

OWEN: AS THE SEA ICE CHANGES AND WE'RE SEEING LONGER PERIODS OF OPEN WATER AND LESS PREDICTABLE ACCESS TO THE AREAS WHERE THEY NEED TO BE TO HUNT THE SEALS THAT THEY SO DEPEND ON, BEING ABLE TO TAKE ADVANTAGE OF AN ALTERNATIVE FOOD RESOURCE BECOMES ESPECIALLY IMPORTANT.

NARRATOR: THEN LATER IN THE MONTH, ANYU AND HER CUBS STRUCK IT LUCKY AT THE BONE PILE.

FOR THEM, THE BONE PILE PROVIDED COPIOUS AMOUNTS OF THE POLAR BEARS' PERFECT MEAL--BLUBBER.

ATWOOD: IN OUR GENETIC STUDIES, WE ARE FINDING AN INDICATION THAT THIS BEHAVIOR, COMING TO SHORE, VISITING THE BONE PILES, IS TRANSMITTED FROM MOM TO HER CUBS, AND THIS APPEARS TO BE WHAT, WHAT MOM IS DOING WITH HER TWO YEARLINGS.

SHE'S TELLING THEM THIS IS WHERE YOU COME THIS TIME OF YEAR TO FIND FOOD.

THIS IS A PREDICTABLE RESOURCE FOR YOU TO COME TO.

OWEN: THESE WHALE REMAINS ARE BECOMING A MORE AND MORE IMPORTANT FOOD RESOURCE AS THEY'RE SPENDING LESS TIME ON THE SEA ICE BECAUSE OF CHANGES IN THE SEA ICE.

NARRATOR: WHILE THE POLAR BEARS ON SHORE WERE FILLING THEIR BELLIES, TODD WAS RELIEVED TO SEE THAT NANOOK HAD FINALLY MADE IT TO THE ICE.

YOU CAN SEE THAT THE ICE NOW IS STARTING TO TRICKLE BACK DOWN SOUTH, AND WE SEE THIS COLLARED BEAR JUST KIND OF RIDING THAT LEADING EDGE OF PACK ICE BACK AS IT COMES SOUTH TOWARD SHORE, AND PRETTY SOON HERE, SHE'LL COME TO LAND IN KAKTOVIK.

NARRATOR: IT WASN'T UNTIL LATE OCTOBER THAT NANOOK ARRIVED AT KAKTOVIK.

IT SEEMED THAT HER CHOICE WAS THE RIGHT ONE, BUT TODD SOON REALIZED IT WASN'T.

NANOOK WAS ALONE.

ATWOOD: A 650-KILOMETER SWIM IS, IS JUST AN AMAZING FEAT FOR AN ADULT TO KIND OF UNDERTAKE AND SURVIVE THROUGH.

I THINK IT WOULD BE ESPECIALLY TAXING FOR A YEARLING.

UM, I THINK IT'S PROBABLY LIKELY THAT THE CUB DIDN'T SURVIVE THE SWIM.

NARRATOR: THE DEATH OF NANOOK'S CUB CAN ALMOST CERTAINLY BE BLAMED ON THE LOSS OF SUMMER SEA ICE.

POLAR BEARS ARE FANTASTIC SWIMMERS AND ARE IMMENSELY ADAPTABLE, BUT THESE VAST, OPEN-WATER JOURNEYS CAN SIMPLY BE TOO MUCH FOR CUBS.

NANOOK MAY HAVE LOST HER CUB, BUT ANYU WAS SETTLED IN AROUND KAKTOVIK.

THE WHALE MEAT HERE WAS HELPING HER AND HER CUBS SURVIVE.

[GROWLING] IT'S EARLY OCTOBER IN KAKTOVIK, 2014.

[DOG BARKING] THE FIRST SNOW HAS FALLEN, HERALDING THE ONSET OF WINTER.

ANYU IS STILL GNAWING AT THE REMAINS OF THE WHALE BONE PILE.

BUT THERE IS LITTLE MEAT LEFT FOR HER OR THE CUBS TIKAANI AND MALINA.

SO, LIKE ANY HUNGRY POLAR BEAR, ANYU DECIDES TO HEAD TO A PLACE WHERE SHE MAY BE ABLE TO SCAVENGE FOOD...

THE VILLAGE.

ATWOOD: THE CONCERN IS THAT WHEN FOOD RUNS OUT AT THE BONE PILE, THEIR NOSE IS GOING TO TAKE THEM TO WHERE THERE'S STILL FOOD, AND THAT'S GENERALLY IN THE VILLAGE, AND THAT REALLY IS THREATENING BEHAVIOR TO PEOPLE.

AND SO, THAT HABITUATION THAT COMES WITH FEEDING AT THE BONE PILE DOES RAISE THE RISK OF HUMAN-BEAR CONFLICT AND CONFLICT KILLS THAT RESULT FROM THAT.

NARRATOR: AS THE LONG NIGHTS DRAW IN, THE NOW-MEATLESS BONE PILE HAS STOPPED SUPPORTING THE BEARS.

THINGS ARE ABOUT TO BECOME A LOT MORE COMPLICATED.

THE STREETS OF KAKTOVIK BECOME WILD.

[HORN HONKING] ON ANY GIVEN EVENING, UP TO 10 BEARS COME IN UNDER THE COVER OF DARKNESS.

BEARS LIKE ANYU DRIVEN TO KAKTOVIK BY LACK OF FOOD.

ATWOOD: WE FOLLOWED HER AND SAW HER KIND OF PICKING AROUND THE EDGES OF TOWN.

SHE KNEW HOW TO KIND OF OPERATE IN AREAS WHERE THERE'S A LOT OF HUMAN ACTIVITY.

SHE WAS SMELLING FOOD.

SHE WANTED TO KNOW WHERE IT WAS COMING FROM, WHETHER IT WAS SOMETHING SHE COULD TAKE ADVANTAGE OF.

NARRATOR: HUNGRY POLAR BEARS ARE DANGEROUS, SO, THE TOWN SET UP A POLAR BEAR PATROL.

MAN: I'VE SEEN POLAR BEARS OUTSIDE MY HOUSE FOR MORE THAN 6 HOURS STRAIGHT AND THEY DIDN'T WANT TO LEAVE.

PEOPLE LIKE TO WALK AROUND LATE AT NIGHT AND THEY COULD BE ATTACKED OR MAULED BY A BEAR.

NARRATOR: TO SCARE THEM OFF, THE VILLAGERS PATROL THE STREETS.

[WHISTLES] THERE'S ONE OVER THERE GOING THIS WAY.

[HORN HONKING] [GUNSHOT] [COCKS GUN] ATWOOD: THEY'RE NOT AFRAID OF PEOPLE.

THEY HAVE NO PROBLEMS OF KIND OF TAKING A STROLL THROUGH TOWN.

HE'S STILL THERE.

SO, THEY'RE NOT SCARED.

ATWOOD: THEY DON'T VIEW PEOPLE AS A GENERAL THREAT.

MAN: THAT'S CRAZY.

AND THEN THEY'LL GET INTO TROUBLE.

[GUNSHOT] [DOG BARKING] NARRATOR: TONIGHT, THEY WERE SUCCESSFULLY SCARED OFF.

[GUNSHOT] [DOG BARKING] BUT IT'S AN ISSUE THAT'S NOT SO EASILY SOLVED.

A SHORT WALK FROM HIS HOUSE, EDDIE REXFORD KEEPS AN ICE CELLAR IN THE PERMAFROST.

[WOOF] EDDIE'S ICE CELLAR AND ITS CONTENTS OF WHALE MEAT ONCE PROVED TOO TEMPTING TO A POLAR BEAR AND ITS TWO CUBS.

[DOG BARKING] COUPLE YEARS AGO, WE HAD OUR MUKTUK AND MEAT IN THIS CELLAR.

A MOTHER AND TWO CUBS CAME.

THEY WERE HUNGRY AND STARVING.

AND THEY BROKE DOWN MY DOOR TO THE ICE CELLAR.

AND WE HAD TO CALL THE POLAR BEAR PATROL TO TRY AND HAZE THEM OUT, BUT THAT DIDN'T WORK BECAUSE THEY WERE STARVING.

I HAD TO PUT THEM DOWN TO SAVE OUR MUKTUK AND MEAT FOR THE COMMUNITY.

[GUNSHOT] NARRATOR: FOR EDDIE'S WIFE MARIE, THERE WAS NO CHOICE.

THE BEARS WOULD SIMPLY NOT GIVE UP.

WE HAD TO SHOOT, SHOOT A MOTHER AND HER CUBS READY TO LEAVE.

IT LOOKED LIKE WITHIN THE YEAR, THEY WOULD HAVE BEEN ON THEIR OWN.

NARRATOR: SHOOTING THE CUBS WAS AN ACT OF MERCY, AS WITHOUT THEIR MOTHER, THEY WOULD HAVE STARVED.

[GROWLS] MARIE: THEY WERE EATING THE FLIPPER AND THEY DIDN'T WANT TO LEAVE.

SO, WE SHOOT 'EM.

IT'S FOOD FOR THE VILLAGE.

[GROWLING] NARRATOR: THE BONE PILE MAY BE A SAFETY NET FOR THE POLAR BEARS.

BUT FOR THE BEARS THAT DIED IN EDDIE REXFORD'S CELLAR, IT WAS THE BONE PILE THAT BROUGHT THESE ANIMALS FATALLY CLOSE TO THE WORLD OF HUMANS.

COULD THE SAME FATE AWAIT ANYU AND HER CUBS, ONCE THE FOOD RUNS OUT?

FOLLOWING THE MOVEMENT OF HER GPS TRACKING COLLAR, TODD WATCHED ANYU GET CLOSER AND CLOSER TO KAKTOVIK.

ATWOOD: SHE DID A PRETTY GOOD JOB AVOIDING THE CORE AREA OF THE VILLAGE.

SHE MOVED AROUND THE OUTSKIRTS.

I MEAN, THAT'S PRETTY CAUTIOUS BEHAVIOR, AND IT'S THE TYPE OF BEHAVIOR THAT YOU TEND TO SEE WITH A BEAR THAT HAS DEPENDENT YOUNG AS THEY'RE BEING PROTECTIVE.

UM, THEY'RE LOOKING FOR FOOD BUT THEY'RE NOT TAKING TOO MANY RISKS BECAUSE THEY WANT TO PROTECT THOSE CUBS, AND SHE MADE THE SMART DECISION NOT TO GO INTO TOWN.

NARRATOR: IT'S GOOD NEWS FOR ANYU, BUT WITH LOSSES LIKE THE BEARS IN KAKTOVIK AND NANOOK'S CUB AT SEA, WHAT'S HAPPENING TO THE OVERALL NUMBER OF POLAR BEARS?

TODD HAS A NEW SET OF FIGURES THAT WILL TELL HIM HOW THE BEARS ARE FARING AS THEY CHOOSE BETWEEN A LONG SWIM NORTH OR LIFE SPENT ON THE MAINLAND.

ATWOOD: SO, IN A PERIOD OF 6 YEARS, WE'VE SEEN APPROXIMATELY A 40% DECLINE IN ABUNDANCE.

AND THAT'S LARGELY ATTRIBUTED TO REALLY POOR SURVIVAL FOR CUBS OF THE YEAR AND YEARLINGS, ALTHOUGH ALL AGE CLASSES--ADULTS ALL THE WAY ON DOWN TO CUBS OF THE YEAR HAD POOR SURVIVAL OVER ABOUT A 3-YEAR PERIOD FROM 2004 TO 2007.

NARRATOR: THESE NUMBERS SEEM DRASTIC.

A 40% DECLINE IS A MASSIVE DROP FOR AN ALREADY THREATENED POPULATION.

THE PRESSURE IS NOW ON THE SCIENTISTS TO FIND OUT WHAT LIES BEHIND SUCH A DEVASTATING RESULT.

WHILE TODD AND HIS TEAM HAVE BEEN FOCUSING ON THE ALASKAN COAST, THE FATE OF THE BEARS THAT CHOOSE LIFE ON THE SEA ICE FAR OFF TO THE NORTH HAS LONG BEEN A MYSTERY.

THE BEARS FACE A CHOICE OF EITHER COMING ONTO LAND OR GOING OUT TO SEA FOLLOWING THE ICE AS IT DRIFTS EVER FARTHER AND FARTHER TO THE NORTH.

BUT THERE'S ALWAYS BEEN THIS QUESTION, OK, THEY DON'T HAVE MUCH TO EAT ON LAND--WHAT IS IT LIKE WAY OUT THERE?

NARRATOR: TO ANSWER THE QUESTION, AN ICE BREAKER WAS COMMISSIONED IN THE SUMMER OF 2009.

A TEAM OF SCIENTISTS WOULD CARRY OUT RESEARCH FURTHER INTO THE NORTHERN SEA ICE THAN EVER BEFORE.

DR. JOHN WHITEMAN WAS AMONG THEM.

LIFE ON THE ICE BREAKER WAS, AH, OTHERWORLDLY.

[LAUGHS] YOU FEEL LIKE YOU'RE ON A DIFFERENT PLANET.

NARRATOR: THEY SCOURED THE VAST EXPANSE OF SEA ICE FOR POLAR BEARS.

ONCE THEY HAD CAUGHT A BEAR AND ANESTHETIZED IT, JOHN COULD PERFORM AN EXTRAORDINARY PROCEDURE.

WHITEMAN: WE WOULD DO SURGERY TO IMPLANT TEMPERATURE LOGGERS THAT WOULD RECORD THE BODY TEMPERATURE BECAUSE BODY TEMPERATURE CAN BE AN INDICATOR, UM, FOR METABOLIC RATE, FOR THE AMOUNT OF ENERGY AN ANIMAL IS USING PER UNIT TIME TO STAY ALIVE.

NARRATOR: TRACKING THE METABOLIC RATE WOULD GIVE THE FIRST-EVER HARD EVIDENCE OF HOW MUCH THE BEARS WERE EATING WHILE OUT ON THE SUMMER SEA ICE.

WHITEMAN: THE SENSORS THEMSELVES WERE PRETTY SMALL, ABOUT THE SIZE OF YOUR PINKY FINGERNAIL.

WE WOULD ROLL THE BEAR ONTO ITS BACK, MAKE AN INCISION, AND THEN GO INTO THE ABDOMINAL CAVITY AND SUTURE THIS TEMPERATURE LOGGER INTO PLACE, AND IT WOULD RECORD THE TEMPERATURE ONCE PER HOUR.

NARRATOR: AFTER LEAVING THE RECORDERS RUNNING FOR SEVERAL MONTHS, JOHN HAD TO GO BACK ONTO THE ICE TO RETRIEVE THEM.

WHITEMAN: YOU COULD DOWNLOAD IT TO YOUR LAPTOP AND YOU WOULD INSTANTLY HAVE THIS WHOLE DATA SET TELLING YOU ONCE PER HOUR WHAT WAS THE INTERNAL BODY TEMPERATURE OF THAT BEAR.

NARRATOR: IF THE BEARS WERE EATING ENOUGH, THEIR BODY TEMPERATURES WOULD STAY CONSTANT THROUGHOUT THE SUMMER.

BUT THAT WASN'T WHAT HE FOUND.

WHAT WE ENDED UP SEEING WITH MOST BEARS IN THE STUDY, IS THAT WHEN THEY WERE OUT ON THE SEA ICE IN THE SUMMER, THEY EXHIBITED THIS SLOW, STEADY DECLINE THAT LASTED FOR A COUPLE MONTHS AND THE MAGNITUDE OF IT WAS A LITTLE BIT LESS THAN ONE DEGREE CELSIUS.

NARRATOR: THIS STEADY DECLINE IN BODY TEMPERATURE PROVED THEY WERE NOT GETTING ENOUGH TO EAT.

WHITEMAN: IF YOU OR I WERE TO GO WITHOUT FOOD FOR DAYS TO WEEKS, OUR BODY TEMPERATURE WOULD SLOWLY AND STEADILY DECLINE LIKE THAT.

FOOD DEPRIVATION, FOOD LIMITATION, NOT GETTING ENOUGH TO EAT.

EVERYTHING ELSE YOU DO IS AFFECTED.

YOU KNOW, RISK VERSUS REWARD CALCULATIONS ARE AFFECTED, AND DEFINITELY REPRODUCTION IS AFFECTED.

NARRATOR: LACK OF FOOD IS A PROBLEM FOR ANY BEAR.

BUT IT CAN BE A DISASTER FOR A PROSPECTIVE MOTHER.

[GROWLING] AMSTRUP: THEY BREED IN THE SPRING.

ONCE FERTILIZATION OCCURS, THE CONCEPTUS DEVELOPS ONLY TO A FEW HUNDRED CELLS.

IT WAITS FOR SEVERAL MONTHS, AND THEN IN THE FALL, ABOUT THE TIME THAT FEMALE POLAR BEARS GO INTO THEIR DENS, IS WHEN IMPLANTATION OCCURS AND ACTIVE DEVELOPMENT OCCURS.

NARRATOR: FEW ANIMALS POSSESS THIS EXTRAORDINARY ABILITY TO DELAY THE IMPLANTATION OF THE CONCEPTUS, THE EARLY STAGE OF THE EMBRYO.

AFTER MATING IN SPRING, IMPLANTATION INTO THE WOMB TAKES PLACE MONTHS LATER IN THE AUTUMN, BUT ONLY IF THE BEAR EATS ENOUGH TO STAY IN GOOD BODY CONDITION.

IF SHE GOES HUNGRY, THE EMBRYO MAY BE ABORTED.

IF THEY DON'T ACHIEVE A GOOD ENOUGH BODY CONDITION BY FALL, THEN THE BABIES MAY NOT SURVIVE.

NARRATOR: THE BEARS FACE A HARSH CHOICE.

GO NORTH AND STARVE... OR GO SOUTH AND GET FAT AT THE WHALE BONE PILE.

BUT WITH OVER 80 BEARS FEASTING, THE MEAT CAN RUN OUT QUICKLY, LEAVING THEM HUNGRY, AND HUNGRY BEARS RISK GOING INTO TOWN, WHICH CAN BE DANGEROUS FOR HUMAN AND BEAR.

THE BONE PILE IS CLEARLY NOT A STRAIGHTFORWARD SOLUTION TO THEIR HUNGER.

IT'S NOVEMBER.

KAKTOVIK IS FROZEN.

THE NEAR-SHORE SEA ICE WHICH HAS BEEN ABSENT SINCE SEPTEMBER HAS NOW RETURNED.

THERE ARE A FEW STRAGGLERS LEFT AT THE BONE PILE, BUT MOST BEARS ARE BACK ON THE SEA ICE, HUNTING SEALS ONCE AGAIN.

SCIENTISTS ARE LEFT TRYING TO FIGURE OUT WHAT ULTIMATELY CAUSED THE 40% POPULATION DROP SINCE 2006.

THE PROBLEM APPEARS TO BE FUNDAMENTALLY CONNECTED TO THE DISAPPEARANCE OF NEAR-SHORE SEA ICE FROM JULY TO NOVEMBER.

I THINK THERE ARE MULTIPLE FACTORS AT PLAY, AND IT PROBABLY DEPENDS ON THE AGE CLASS.

SO, FOR CUBS, PERHAPS ITS EXPOSURE TO MORE VOLATILE WEATHER EVENTS, THE OPEN WATER, HIGH SWELLS, HAVING TO SWIM IN THAT AND NOT BEING ABLE TO NEGOTIATE THOSE VERY TENUOUS ENVIRONMENTAL CONDITIONS THAT THEY FIND THEMSELVES IN WHEN THERE'S NO SEA ICE AVAILABLE OVER THE SHELF.

NARRATOR: ON HIS HELICOPTER SURVEYS, TODD AND HIS TEAM WERE FINDING THAT THE BEARS WERE LOSING WEIGHT AND BODY CONDITION.

FACTORS THAT CAN CAUSE FEMALE POLAR BEARS TO MISCARRY THEIR YOUNG.

91.3.

NARRATOR: AND THE PRIMARY CAUSE WAS LACK OF FOOD THAT NOT ONLY AFFECTS BEARS DURING SUMMER, IT CAN AFFECT MOTHERS IN THEIR DENS RIGHT INTO WINTER.

FOR ADULTS, IT'S PROBABLY MORE DRIVEN BY PREY ACCESSIBILITY, THEY'RE NOT ABLE TO ROUTINELY ACCESS PREY.

THE ULTIMATE CAUSE OF POPULATION DECLINES.

IT'S PROBABLY RELATED TO NUTRITIONAL RESTRICTION.

NARRATOR: BUT NOT EVERYONE IS SO SURE THAT THE LOSS OF THE SEA ICE HABITAT AND BEING FORCED ONTO LAND WILL PROVE THE POLAR BEARS' UNDOING.

SMITH: THERE ARE LAND REGIONS ON THE FRINGES OF THE MARINE ECOSYSTEM, WHETHER ON LAND OR ISLANDS, THAT PROVIDE MORE THAN ENOUGH SUSTENANCE FOR POLAR BEARS TO BE ABLE TO SURVIVE ON LAND, AND THAT'S NOT ACCOUNTING FOR THE CHARACTERISTICS THAT THEY ALREADY POSSESS THAT LET THEM UTILIZE LAND AS A RESOURCE.

NARRATOR: ARTHUR C. SMITH HAS BEEN OBSERVING THE POLAR BEARS HERE CLOSELY FOR NEARLY A DECADE.

HE'S CONVINCED THAT THEY'RE MORE RESOURCEFUL THAN THEY MIGHT AT FIRST APPEAR.

SMITH: THEY EAT EGGS, THEY'LL, YOU KNOW, THEY KILL LIVESTOCK WHEN THEY LAND.

I'VE SEEN THEM DIVE AND COME UP WITH DUCKS.

NARRATOR: LAND-BASED POLAR BEARS WILL SCAVENGE WHEN THE NEAR-SHORE SEA ICE HAS VANISHED IN SUMMER AND AUTUMN.

THEY WILL EAT SMALLER ANIMALS, LIKE GEESE AND THEIR EGGS, AND EVEN TAKE ON THE COLOSSUS OF THE ARCTIC, THE WALRUS, TO GET THE CALORIES THAT THEY NEED.

YOU KNOW, PEOPLE HERE HAVE SEEN THEM CHASING CARIBOU, SO, GIVE THEM A CHANCE TO DEMONSTRATE THAT THEY ALREADY KNOW WHAT TO DO AND I THINK THAT WE MAY BE SURPRISED.

NARRATOR: ARTHUR SMITH'S VIEWPOINT IS BASED ON DIRECT OBSERVATION OF THE POLAR BEARS' ABILITY TO SCAVENGE AND HUNT ON LAND.

BUT FOR OTHER POLAR BEAR SPECIALISTS, THE PICTURE IS NOT AS HOPEFUL.

ATWOOD: YOU KNOW, THERE'S EVIDENCE THAT BEARS ARE, ARE FEEDING ON TERRESTRIAL RESOURCES.

BUT THERE'S NO COMPELLING EVIDENCE THAT THEY'RE ABLE TO FEED ON ENOUGH TERRESTRIAL RESOURCES OR THAT THOSE TERRESTRIAL RESOURCES ARE AS ENERGY-RICH AS MARINE PREY TO ALLOW POLAR BEARS TO MAKE THAT ADAPTATION TO LIVING ON LAND.

NARRATOR: FOR TODD, THE POLAR BEAR EVOLVED TO HUNT FAT, RICH SEALS THROUGH SEA ICE.

THEY SIMPLY CANNOT ADAPT FAST ENOUGH TO LIVE SUCCESSFULLY WITHOUT THAT SPECIFIC HABITAT.

ATWOOD: I THINK IN ORDER FOR A SPECIES TO ADAPT, THERE HAS TO BE TIME FOR THE SPECIES TO ADAPT.

AND GIVEN THE SUBSTANTIAL DECLINE IN SEA ICE HABITAT THAT WE'VE SEEN JUST IN THE LAST 15 YEARS, IT WOULD SUGGEST TO ME THAT THE HABITAT IS CHANGING AT A RATE FASTER THAN POLAR BEARS CAN EVOLVE BEHAVIORAL RESPONSES TO COPE WITH THOSE CHANGES.

POLAR BEARS SIMPLY CAN'T MAKE A LIVING WITHOUT SEA ICE HABITAT.

SEA ICE HABITAT IS, IS THE FOUNDATION TO BEING A POLAR BEAR, AND THAT'S THE PLATFORM FOR ACCESSING PREY, FOR ACCESSING VERY FAT-RICH PREY, WHICH POLAR BEARS HAVE EVOLVED TO METABOLIZE.

NARRATOR: MELTING ICE IS NOT THE ONLY THREAT CHALLENGING THE POLAR BEAR.

THERE'S HUGE RESERVES OF OIL AND GAS IN THE OFFSHORE AREAS.

NARRATOR: SHELL HAS ALREADY SPENT $5 BILLION PROSPECTING OFF THE ALASKAN COAST.

AMSTRUP: AS THERE'S LESS AND LESS SEA ICE, THE OBSTACLES TO EXPLORING AND DEVELOPING IN THOSE AREAS ARE REDUCED.

YOU KNOW, WE CAN SEE GREATER AND GREATER PRESSURE.

THE RISKS THAT RESULT, OR THE DAMAGE THAT COULD RESULT FROM AN OFFSHORE SPILL, IS MUCH GREATER.

NARRATOR: AS A MARINE MAMMAL, THE POLAR BEAR WOULD BE VULNERABLE TO EVEN A MINOR SPILL.

NOT ONLY WOULD TOXINS ENTER THE FOOD CHAIN, AS POLAR BEARS REGULARLY CLEAN THEIR FUR WITH THEIR TONGUE, ANY OIL IN THE WATER WOULD RAPIDLY ENTER THE BEARS' DIGESTIVE SYSTEM.

BUT OIL EXPLORATION BRINGS WEALTH.

IN KAKTOVIK, PROFITS FROM LAND-BASED WELLS ARE ALREADY BENEFITING THE COMMUNITY IN THE FORM OF NEW SCHOOLS AND INFRASTRUCTURE.

BUT SOME KAKTOVIK LOCALS LIKE ROBERT THOMPSON ARE CONCERNED ABOUT AN INTENSIFICATION IN OIL EXTRACTION.

THE OIL IN THIS AREA COULD BRING A LOT OF WEALTH TO PEOPLE.

BUT TO SOME PEOPLE, IT'S MORE IMPORTANT TO, TO KEEP THE TRADITIONS GOING, TO KEEP THE LAND CLEAN AND NOT--NOT HAVE TO LIVE IN AN OIL FIELD.

PERSONALLY, I DON'T WANT TO LIVE IN AN OIL FIELD.

NARRATOR: IN SEPTEMBER 2015, SHELL SUSPENDED THEIR PROSPECTING NEAR KAKTOVIK.

BUT THE CHANGES HAPPENING IN THE ARCTIC ARE ABOUT MORE THAN JUST ALASKA.

[BARKS] ATWOOD: POLAR BEARS ARE A SYMBOL OF WHAT CAN HAPPEN IN A SYSTEM WHICH IS CHANGING DRAMATICALLY AND IT'S CHANGING RAPIDLY BECAUSE OF CLIMATE CHANGE.

STOPPING THE LOSS OF SEA ICE HABITAT IS PREDICATED ON MITIGATING GREENHOUSE GAS EMISSIONS, AND IF SOMEBODY HAS A GOOD IDEA FOR HOW WE DO THAT, I'D LOVE TO KNOW WHAT IT IS.

[LAUGHS] NARRATOR: FOR ANYU AND HER CUBS, THE FUTURE IS STILL UNCERTAIN.

AND THE KAKTOVIK BONE PILE THAT SEEMED AT FIRST TO BE A SOLUTION HAS ULTIMATELY REVEALED THE DESPERATION OF THE BEARS OF THE SOUTHERN BEAUFORT SEA.

ALL THE EVIDENCE POINTS TO A POLAR BEAR POPULATION UNDER GREATER THREAT THAN EVER BEFORE.

AMSTRUP: IN 50 YEARS, WE COULD LOSE 2/3 OF THE WORLD'S POLAR BEARS.

IF WE HAVEN'T FIGURED OUT HOW TO DEAL WITH THIS PROBLEM WELL BEFORE WE GET, UH, TO THE MIDDLE OF THIS CENTURY, I DON'T THINK ANYBODY'S GOING TO BE CARING ABOUT POLAR BEARS.

TO SEE THAT COMING TO AN END RIGHT BEFORE OUR EYES IS, UH, KIND OF SOBERING.

I'M SAD ABOUT IT, YES.

NARRATOR: THE BONE PILE CAN NEVER BE A SUBSTITUTE FOR WHAT POLAR BEARS DO BEST--HUNT SEALS ON ICE.

DEPENDING ON HUMANS TO PROVIDE FOOD IS NOT A VIABLE, LONG-TERM SOLUTION.

WITHIN 6 MONTHS, TIKAANI AND MALINA WILL BE ON THEIR OWN, NO LONGER DEPENDENT ON ANYU.

WHAT WILL THE FUTURE HOLD FOR THEM... AND, IN THE LONGER TERM, THEIR CUBS?

THEIRS WILL BE A VASTLY DIFFERENT WORLD THAT MAY NO LONGER HAVE A PLACE FOR THEM.