Episode 1

MAN: YELLOWSTONE, HIGH IN THE ROCKY MOUNTAINS.

FREEZING TEMPERATURES AND UNPREDICTABLE WEATHER MAKE WINTER HERE ONE OF THE TOUGHEST ON EARTH.

EACH YEAR, LIFE-AND-DEATH DRAMAS PLAY OUT AGAIN AND AGAIN, BUT THIS YEAR, THERE'S A TWIST.

[ELK BUGLES] THIS GRIZZLY BEAR SHOULD BE HIBERNATING, BUT WARM WEATHER WOKE HIM UP EARLY.

THE QUESTION IS, CAN HE FIND ENOUGH FOOD TO MAKE IT THROUGH UNTIL SPRING?

HIS SURVIVAL DEPENDS ON A BATTLE THAT HAS JUST BEGUN BETWEEN THE FORCES OF WINTER AND THE FORCES OF SPRING.

IT'S THE EXTREME CHANGES IN WEATHER THAT MAKE YELLOWSTONE SUCH A CHALLENGING PLACE TO LIVE.

I'M KIRK JOHNSON, AND I'VE COME HERE TO FIND OUT HOW WILDLIFE COPES WITH ONE OF THE GREATEST SEASONAL CHANGES ON THE PLANET.

WHAT HAPPENS HERE IS REALLY UNIQUE.

THE WILDLIFE IS ABOUT TO ENDURE A TRANSITION FROM A FRIGID WINTER TO A SMOLDERING SUMMER AND RIGHT IN THE MIDDLE OF IT, A DELUGE OF WATER.

THIS GREAT YELLOWSTONE THAW WILL TAKE 4 MONTHS, STARTING IN THE VALLEYS AND ENDING IN THE PEAKS.

TO MAKE IT THROUGH THIS INCREDIBLE TRANSFORMATION, WILDLIFE WILL HAVE TO FEND OFF FLOODS, STARVATION, COLD... [THUNDER] AND EVEN FIRE.

[SCREECH] THE CHANGE IN SEASONS IS DRAMATIC.

WE WILL FOLLOW A NUMBER OF ANIMALS TO SEE THIS COMPELLING DRAMA UNFOLD THROUGH THEIR EYES.

A GROUP OF FILMMAKERS AND SCIENTISTS... OH, MY.

THIS ACTUALLY QUALIFIES AS WORK.

I'M TAKING MY COAT OFF.

YEAH.

JOHNSON: WILL SHED NEW LIGHT ON THIS UNIQUE AND ICONIC ECOSYSTEM AS THEY REVEAL THE STORY OF THE GREAT YELLOWSTONE THAW.

MAN: THEY MAKE A MISTAKE, THEY'RE KILLED.

JOHNSON: IT'S EARLY MARCH.

FOR 4 MONTHS, YELLOWSTONE'S WILDLIFE HAS BATTLED BRUTAL COLD... [BUGLING] AND A LANDSCAPE LOCKED IN SNOW.

GREATER YELLOWSTONE COVERS OVER 34,000 SQUARE MILES OF WILDERNESS, INCLUDING THE GRAND TETONS IN THE SOUTH AND AT ITS CORE, YELLOWSTONE.

THE WHOLE ECOSYSTEM IS DOMINATED BY MOUNTAINS.

ITS EXTREME WEATHER IS DUE TO ITS EXTREME GEOLOGY.

YELLOWSTONE SITS ON TOP OF ONE OF THE WORLD'S LARGEST VOLCANOES.

3 TIMES IN THE LAST TWO MILLION YEARS, THIS PLACE HAS ERUPTED VIOLENTLY, COVERING MUCH OF THE CONTINENT WITH VOLCANIC ASH.

INTERESTINGLY, THE HEAT BENEATH HAS ALSO PUSHED UP THE YELLOWSTONE PLATEAU, CREATING THE HIGH ELEVATIONS THAT MAKE THE WINTERS HERE SO SEVERE AND COLD.

OVER 8,000 FEET UP IN THE PARK'S PLATEAU, ANIMALS HAVE TO TOUGH OUT BITTER CONDITIONS.

I'VE BEEN COMING TO YELLOWSTONE SINCE I WAS A KID.

IT'S A TRULY UNIQUE PLACE.

I'M FASCINATED BY ITS GEOLOGY AND ITS INCREDIBLE WILDLIFE.

THIS AREA IN THE NORTH IS HOME TO AROUND 200 SLUMBERING GRIZZLIES WHO HIBERNATE THROUGH THE WINTER DUE TO LACK OF FOOD...

BUT THIS BEAR IS ALREADY OUT, AND IT'S ONLY EARLY MARCH.

HIS NORMAL FOOD SOURCES AREN'T YET READILY AVAILABLE, SO HE'LL HAVE TO IMPROVISE TO SURVIVE.

OUR CAMERA TEAM HAS BEEN TRACKING HIM CLOSELY AND HAS FOLLOWED HIM DOWN TO THE VALLEY FLOOR.

YOU'D THINK BISON WOULD BE A PERFECT MEAL...

BUT THEY'RE TOO BIG TO TAKE DOWN ON HIS OWN, EVEN FOR A STARVING GRIZZLY BEAR OF HIS GREAT SIZE.

INSTEAD, HE'S FOLLOWING HIS NOSE.

IT'S HIS SUPER SENSE, BRISTLING WITH OVER A BILLION NERVE CELLS... AND IT'S LED HIM TO THIS POND.

COULD THERE BE FISH HERE?

SOAKING WET IN FREEZING WATER?

I DON'T THINK THAT WAS HIS PLAN...

BUT HE'S NOT HERE BY CHANCE.

HIS AMAZING SENSE OF SMELL HAS LED HIM TO A ROTTING BISON UNDER THE ICE.

IT'S MOST LIKELY HIS FIRST FOOD IN 4 MONTHS.

THAT'S ONE BIG PROTEIN HIT...

BUT THE SMELL IS ATTRACTING COMPETITION.

NO COYOTES WOULD CHALLENGE A HUNGRY BEAR FOR FOOD, ESPECIALLY ONE 15 TIMES THEIR WEIGHT...

BUT THEY WILL HARASS HIM FOR SCRAPS.

TO PUT THEM OFF THE SCENT, HE COVERS THE CARCASS, WHICH ALSO KEEPS IT FRESHER FOR LONGER.

HIBERNATION IS LIKE GOING ON A CRASH DIET.

HE'S LOST A THIRD OF HIS BODY WEIGHT AND NOW NEEDS TO PILE THE POUNDS BACK ON... [BIRD SCREECHING] AND THAT MEANS MAKING SURE THAT EVERY MOUTHFUL IS HIS ALONE.

CONSIDERING HOW SCARCE FOOD CAN BE BY THE END WINTER, THIS BEAR REALLY HAS HIT THE JACKPOT.

IT'S RISKY FOR A LONE MALE TO EMERGE EARLY, BUT FOR A FEMALE WITH CUBS, THE STAKES WOULD BE MUCH HIGHER.

I'M HEADING NORTHWEST TO THE GALLATIN MOUNTAINS TO MEET BEAR EXPERT CASEY ANDERSON, WHO'S BEEN STUDYING THE GRIZZLIES HERE FOR DECADES.

GIVEN THE UNSEASONABLY WARM TEMPERATURES IN THE LAST FEW WEEKS, CASEY'S KEEN TO SEE IF ANY MORE BEARS ARE EMERGING EARLY.

ANDERSON: SO WHAT WE'RE GOING TO DO TODAY IS GO UP AND REALLY KIND OF JUST LOOK AROUND, LOOK IN THE SPOTS WHERE, YOU KNOW-- WHERE I KNOW THERE IS A LOT OF DENNING BEARS AND LOOK FOR SIGN, AND THEY COULD BE COMING OUT MORE AND MORE EVERY DAY AS THIS CONTINUES TO GET WARMER AND WARMER.

JOHNSON, VOICE-OVER: IT'S IMPOSSIBLE FOR CASEY TO MONITOR DENS ON A DAILY BASIS, SO HE GETS A LITTLE HELP BY USING CAMERA TRAPS, A SPY NETWORK SPREAD ACROSS THE SLOPES.

CREEPING UP ON BEAR DENS IS NOT FOR THE FAINT-HEARTED.

ANY GRIZZLY THAT EMERGES NOW WILL HAVE SPENT SEVERAL MONTHS FASTING.

IF WE'RE GONNA SEE ANY BEAR AT ALL, IT'S LIKELY TO BE A BIG, HUNGRY MALE.

EXACTLY.

PERFECT.

HA HA!

HA HA!

JOHNSON, VOICE-OVER: MALES ARE THE FIRST TO COME OUT OF HIBERNATION.

FEMALES WITH CUBS EMERGE LAST, USUALLY TIMING THEIR EXIT IN MAY.

WITH THE NEW SPRING VEGETATION, THEIR TABLE WILL BE SET.

[WIND WHISTLING] AS WE CLIMB HIGHER, THE WEATHER GETS WORSE.

IT MUST BE TOUGH FOR BEARS WHO COME OUT EARLY.

I'VE SEEN A 90-DEGREE TEMPERATURE CHANGE THIS TIME OF THE YEAR...

IN ONE DAY?

IN ONE DAY.

YOU'D THINK IT-- 90 DEGREES?

YOU CAN THINK IT'S SUMMER...

RIGHT.

AND ALL OF A SUDDEN, IT'S THE DEAD OF WINTER AGAIN.

I'VE SEEN FROM 70, ALMOST 80, ALL THE WAY DOWN TO BELOW ZERO.

JOHNSON, VOICE-OVER: PERIODS OF FLUCTUATING TEMPERATURES ARE GETTING MORE COMMON IN YELLOWSTONE, AND THIS COULD BE A PROBLEM FOR OUR BEARS BECAUSE RIGHT AFTER A WARM SPELL, TEMPERATURES CAN PLUMMET RIGHT BACK DOWN AGAIN, AND THERE ISN'T MUCH, IF ANY, FOOD AROUND.

9,000 FEET UP, WE'RE IN THE ZONE FOR DENS.

SEE THIS ROCK RIGHT OVER HERE?

YEAH.

SO JUST ON THIS SIDE IS WHERE I FOUND THIS DEN SITE.

I'VE SNUCK UP ON A FEW DENS OVER THE YEARS, AND YOU JUST HEAR THIS, "GRRR..." AND THAT MEANS-- OH, JUST A LITTLE BIT LIKE, "I HEAR YOU MOVING OUT THERE."

"IT'S TIME TO LEAVE, TIME TO BACK OFF."

"BACK AWAY."

GOOD TO GO.

JOHNSON, VOICE-OVER: AT LEAST I KNOW WHAT TO LISTEN FOR.

OK. CAN'T BELIEVE I'M SNEAKING UP ON A GRIZZLY BEAR DEN.

JOHNSON, VOICE-OVER: WHOEVER'S INSIDE HAS SHUT THE DEN WITH ROCKS AND TWIGS TO KEEP IT WARM.

A QUICK CHANGE OF CAMERA, AND OUR JOB'S DONE.

THAT IS CLOSE ENOUGH FOR MY LIKING.

THERE'S NO SIGN OF ACTIVITY OUTSIDE THIS DEN.

CASEY'S SURE THAT A FEMALE WITH CUBS ARE IN RESIDENCE.

YOU KNOW, THAT WAS SOMETHING.

HOLY COW, MAN.

I JUST LOVE THINKING ABOUT IT.

THOSE LITTLE CUBS WOULD BE THAT BIG RIGHT NOW.

WHEN THEY WERE BORN, THAT WAS THEIR WORLD, AND YOU COULD IMAGINE THE REALITY CHECK THAT THEY'RE GONNA HAVE WHEN THEY POP THEIR HEAD OUT AND THIS IS THEIR WORLD ALL OF A SUDDEN.

OH, IT IS JUST REMARKABLE.

YOU'VE TOTALLY CHANGED THE WAY I THINK ABOUT WALKING AROUND THIS LANDSCAPE, I'LL TELL YOU THAT MUCH.

COULD BE MORE AROUND HERE RIGHT NOW.

YEAH.

WELL, THEY'RE RIGHT BEHIND ME, CHECKING MY BACK.

JOHNSON, VOICE-OVER: LIFE HERE IN WINTER IS TOUGH, AND THAT GOES FOR EVERY HABITAT FROM THE MOUNTAINS AND FORESTS TO THE WATERWAYS, INCLUDING THE SNAKE RIVER.

IT FLOWS THROUGH THE GRAND TETON NATIONAL PARK, AND IT'S CRITICALLY IMPORTANT FOR THE ANIMALS THAT LIVE HERE.

FOR MUCH OF THE WINTER, THIS RIVER IS FROZEN FROM BANK TO BANK.

NOW, THE ICE HAS JUST GONE OUT, BUT THE RIVER IS STILL REALLY COLD.

A WARM SNAP IN LATE FEBRUARY AND EARLY MARCH MELTED THE ICE ON MANY OF YELLOWSTONE'S RIVERS.

IT'S THE MOMENT SOME ANIMALS HAD BEEN WAITING FOR.

PLANTS UNDER WATER ARE MORE NUTRITIOUS THAN THOSE UNDER SNOW, AND THAT'S IMPORTANT FOR THIS MOOSE, WHO'S LOST A QUARTER OF ITS BODY MASS OVER WINTER... AND THEY'RE EQUALLY IMPORTANT FOR THE MUSKRATS.

AS HE DIVES FOR FOOD, HIS LIPS SEAL SHUT BEHIND HIS BIG INCISOR TEETH SO HE DOESN'T SWALLOW ANY WATER WHEN HE'S GATHERING PLANTS.

DESPITE THE FREEZING-COLD WATER, HE STAYS WARM AND DRY, THANKS TO HIS WATERPROOF, DOUBLE-LAYERED FUR COAT...

BUT THE WARM SPELL, AS FEARED, DOESN'T LAST.

IN MID MARCH, WINTER RETURNS WITH A VENGEANCE.

CAMERAMAN AND "NATIONAL GEOGRAPHIC" PHOTOGRAPHER CHARLIE HAMILTON JAMES IS OUT ON THE SNAKE RIVER.

HE'S TRACKING AN ELUSIVE MAMMAL THAT NEEDS TO HUNT WHATEVER THE WEATHER--THE OTTER.

JAMES: WE'VE HAD, I'D SAY, TWO OR 3 WEEKS OF MILD WEATHER, AND NOW TODAY, IT'S JUST PLUMMETED.

JOHNSON, VOICE-OVER: IT'S MINUS 20 DEGREES FAHRENHEIT.

IT'S NOT JUST COLD.

IT'S REALLY COLD TODAY.

JOHNSON, VOICE-OVER: CHARLIE WANTS TO SEE HOW THESE BITTER TEMPERATURES ARE AFFECTING THE OTTERS.

THERE'S AN OTTER.

THAT'S COMPLETELY OUT OF NOWHERE.

WHERE ARE MY WADERS?

COME ON.

COME ON.

COME ON.

JOHNSON, VOICE-OVER: HE COUNTS NOT ONE, BUT 5 MALE RIVER OTTERS ON THIS TWO-MILE STRETCH.

EACH NEEDS TO EAT AROUND 4 POUNDS OF FISH A DAY, SO CHARLIE'S GOING TO CHECK THEIR SUPPLY WITH HIS CAMERA.

JAMES: AND HOLD THERE, BIT MORE THAT WAY, BIT MORE BACKWARDS.

OH, THERE'S FISH EVERYWHERE, ACTUALLY.

JOHNSON, VOICE-OVER: SO THERE'S PLENTY OF FOOD, BUT CHARLIE'S NOTICED A PROBLEM.

THERE'S A SIXTH OTTER, AND HE'S NOT IN GREAT SHAPE.

OK, LITTLE GUY.

JOHNSON, VOICE-OVER: HE DOESN'T BELONG TO A GROUP, SO HE HAS TO FEND FOR HIMSELF.

JAMES: THE LITTLE MALE OTTER'S NOT REALLY STOCKED WITH FAT, AND I SUSPECT THAT'S A RESULT OF NOT LIVING IN A GROUP.

IT'S HARDER TO FISH.

IT'S LESS SAFE, AND YOU CAN SEE THAT IN HIM PHYSICALLY.

JOHNSON, VOICE-OVER: COMPETITION FOR FOOD IS SO FIERCE THAT IT'S PUSHED SOME OF YELLOWSTONE'S PREDATORS INTO PIRACY.

THIS BALD EAGLE HERE, HE'S SPOTTED THE OTTER, AND HE'S COME IN.

JOHNSON, VOICE-OVER: USUALLY, THESE BALD EAGLES SCOOP FISH FROM THE SURFACE OF THE WATER, BUT WHEN IT'S THIS COLD, FISH HEAD TO THE BOTTOM, SO THE BEST WAY FOR THE EAGLES TO GET THEM... IS THEFT.

JAMES: THE EAGLES HERE ARE COMPLETELY TUNED IN TO THE OTTERS.

[EAGLES SCREECHING] I'M SURE THESE BALD EAGLES PUT A HUGE AMOUNT OF PRESSURE ON THE OTTERS AND PARTICULARLY ON A SINGLE OTTER.

IF THERE'S 5 OTTERS, THERE'S 5 PAIRS OF EYES ALL LOOKING OUT FOR THAT EAGLE, AND THEY DO.

THEY ARE CONSTANTLY LOOKING OUT FOR THE EAGLE.

IF YOU'RE ONE OTTER, YOUR CHANCES OF BEING ROBBED ARE MUCH HIGHER, BASICALLY.

JOHNSON, VOICE-OVER: OVER THE NEXT SEVERAL DAYS, THE OTTER LONER IS NOWHERE TO BE SEEN.

CHARLIE HAS A THEORY.

HE THINKS IT MIGHT HAVE SHIFTED TO NIGHT HUNTING TO AVOID THE EAGLE EYES ON HIS MEALS.

JAMES: I'LL BE HONEST.

THESE AREN'T GREAT CONDITIONS FOR FINDING AN OTTER.

AH, A SORT OF TITANIC MOMENT HAS OCCURRED.

HA HA!

WE'VE HIT-- APPEAR TO HAVE HIT AN ICEBERG IN THE DARK.

JOHNSON, VOICE-OVER: IN WARMER MONTHS, IT'S NORMAL FOR OTTERS TO HUNT AT NIGHT, BUT NOT WHEN IT'S AS COLD AS THIS.

I'M KIND OF LOSING ALL HOPE NOW.

THERE'S AN OTTER.

THAT'S AN OTTER.

THAT'S LOVELY.

THIS HAS DEFINITELY PROVED MY THEORY THAT THE OTTER'S COMING OUT AT NIGHT.

JOHNSON, VOICE-OVER: THESE BITTER TEMPERATURES MAY HAVE FORCED OUR SOLO OTTER TO ADOPT A DIFFERENT STRATEGY FROM THE GROUP-LIVING OTTERS AND TO USE THE COVER OF DARKNESS TO EAT IN PEACE.

ALL ACROSS YELLOWSTONE, THE CHALLENGE IN WINTER IS TO HANG ON AND FIND A WAY TO SURVIVE UNTIL THE WARMER TEMPERATURES OF SPRING.

[GRUNTING] 3 TIMES IN THE PAST TWO MILLION YEARS, THE YELLOWSTONE SUPER VOLCANO HAS ERUPTED, PUSHING UP THE PLATEAU.

THIS HIGH ELEVATION IS THE REASON IT'S SO COLD...

BUT FOR SOME, THE VOLCANIC ACTIVITY OFFERS AN OPPORTUNITY.

BISON ARE ONE OF THE FEW SPECIES THAT DON'T SEEM BOTHERED BY THE BITTERNESS OF WINTER...

BUT THEY STILL NEED TO EAT.

OVER 5,000 OF THESE MASSIVE ANIMALS LIVE IN YELLOWSTONE, SOME OF WHOM MIGRATE IN WINTER TO THE GEOTHERMAL REGION ON THE WEST SIDE OF THE PARK.

200 BISON GRAZE HERE THROUGH WINTER.

THE WARM EARTH MEANS LESS SNOW AND EASY ACCESS TO VEGETATION...

BUT THERE'S NO SUCH THING AS A FREE LUNCH.

TWO CHEMICALS OCCUR HERE IN HIGH CONCENTRATIONS-- SILICA AND FLUORIDE.

THE HOT WATER PUSHING UP FROM DEEP UNDERGROUND DISSOLVES SILICA FROM THE VOLCANIC ROCK AND DEPOSITS IT ON THE VEGETATION.

EATING SILICA-COATED GRASS IS A BIT LIKE EATING SOMETHING COVERED IN A FINE DUSTING OF GROUND GLASS.

IT'S ABRASIVE AND VERY TOUGH ON THE TEETH.

THE WATER HERE ALSO CONTAINS FLUORIDE.

IN LOW DOSES, LIKE IN TOOTHPASTE, IT'S GOOD FOR TEETH, BUT HERE, IT'S SO CONCENTRATED, IT ACTUALLY SOFTENS, RATHER THAN STRENGTHENS, THE BISON'S BONES.

EXPOSURE TO SILICA AND EXCESS FLUORIDE IS A HEAVY PRICE TO PAY, COSTING THEM THEIR TEETH AT AN EARLY AGE.

LIFE EXPECTANCY FOR THE BISON THAT GRAZE HERE IS 5 YEARS LESS THAN FOR BISON ELSEWHERE IN THE PARK.

ONES THAT STAY IN SNOWY REGIONS MAY BE COLDER, BUT THEY LIVE LONGER.

IT'S NOT JUST EXTREME COLD THAT MAKES WINTER IN YELLOWSTONE SO CHALLENGING.

IT'S THE FACT THAT THE WEATHER IS SO UNPREDICTABLE, AND THIS YEAR'S BEEN MORE VARIABLE THAN MOST.

TEMPERATURES IN JANUARY AND EARLY FEBRUARY WERE PRETTY STANDARD.

THEN THEY ROSE SHARPLY AND PLUMMETED AGAIN.

IT MIGHT NOT LOOK DRAMATIC, BUT FOR ONE BIRD IN PARTICULAR, THE CHANGE IN TEMPERATURE COULD BE LIFE-THREATENING.

THE FORESTED SLOPES OF THE TETON MOUNTAINS ARE HOME TO A TRUE WINTER SPECIALIST-- THE GREAT GRAY OWL...

THE LARGEST OWL IN NORTH AMERICA WITH A WINGSPAN OF UP TO 5 FEET.

IT SURVIVES IN FREEZING FORESTS FROM SIBERIA TO SCANDINAVIA TO HERE IN YELLOWSTONE.

RESEARCHERS BELIEVE SEVERAL HUNDRED GREAT GRAY OWLS LIVE IN A 150-SQUARE-MILE PATCH OF MIXED FOREST AT THE BASE OF THE TETONS.

CAMERAMAN JEFF HOGAN HAS HAD A LIFELONG LOVE AFFAIR WITH THIS MYSTERIOUS BIRD AND HAS BEEN SCOURING THEIR FOREST HABITAT FOR WEEKS HOPING FOR A SIGHTING.

HOGAN: I'VE BEEN FOLLOWING AND FILMING THE GREAT GRAY OWLS FOR JUST ABOUT 30 YEARS NOW, AND IT'S STILL JUST AS EXCITING AND CHALLENGING AS IT WAS THE VERY FIRST DAY.

SO THIS IS A FANTASTIC PLACE FOR OWLS TO BE HANGING OUT.

I MEAN, IT'S MIXED ASPENS AND CONIFER FOREST, ALONG WITH THESE MEADOWS PROVIDE AN INCREDIBLE HABITAT FOR THE PREY THAT THE OWL FEEDS UPON.

JOHNSON, VOICE-OVER: GREAT GRAYS FEED ON RODENTS BURROWING UNDER THE SNOW.

THEIR HUGE FACES ACT LIKE SATELLITE DISHES, DIRECTING SOUND TO THEIR EARS.

THEIR HEARING IS EXCEPTIONAL.

THEY CAN DETECT PREY FROM MORE THAN 300 FEET AWAY THROUGH SNOW ALMOST ONE AND A HALF FEET DEEP.

IT'S ONE THING TO KNOW WHERE TO POUNCE.

IT'S ANOTHER TO BREAK THROUGH.

THE FLUCTUATING WEATHER CONDITIONS AND THOSE DENSE LAYERS IN THE SNOWPACK MAKE HUNTING TRICKY.

HOGAN: EARLIER THIS WEEK, WE GOT A LOT OF SNOW, AND THEN THE SKIES CLEARED, SO YOU CAN LOOK AROUND HERE AND SEE WHERE THE SUN IS BEATING DOWN ON THE SURFACE OF THIS SNOWPACK, AND IT REALLY SOFTENS IT UP.

IT DOESN'T MELT IT COMPLETELY, BUT IT MAKES IT REALLY SOFT AND WET, AND THEN AT NIGHT WHEN THE TEMPERATURES PLUMMET, IT'LL FREEZE HARD, LIKE, AND TURN IT TO ICE, AND YOU CAN ACTUALLY SEE THIS LAYER OF CRUST.

BOY, YOU CAN REALLY FEEL THAT.

I MEAN, OUCH, THIS IS HARD... AND AS THE TEMPERATURES DROP AS NIGHT APPROACHES, THIS IS GOING TO GET HARDER AND HARDER, AND THESE OWLS HAVE TO BUST THROUGH THIS CRUST AND THEN MAYBE ANOTHER FOOT OF SNOW TO GET AT THEIR PREY.

JOHNSON, VOICE-OVER: JEFF'S WORRIED.

HE HASN'T SEEN ANY GREAT GRAYS SO FAR THIS SEASON.

THEY COULD HAVE BEEN FORCED TO HUNT ELSEWHERE.

SO I GUESS I'M GOING TO HAVE TO JUST KEEP ON LOOKING.

AH.

WE HAVE AN OWL.

JOHNSON, VOICE-OVER: JEFF'S PERSISTENCE PAYS OFF.

WE'RE GONNA SET UP HERE.

[CLICK] THERE'S SOMETHING RIGHT HERE UNDERNEATH HIM.

JOHNSON, VOICE-OVER: THE OWL'S GETTING READY TO HUNT, BUT HE'S GOT TO GET THROUGH THAT ICY CRUST.

HOGAN: OH, HE JUMPED.

OH, HE'S ON THE GROUND NOW.

I DON'T THINK HE GOT ANYTHING.

HE JUST FLEW UP WITH NOTHING.

JOHNSON, VOICE-OVER: IF THEY CAN'T HUNT, THEY WON'T NEST OR LAY EGGS THIS SEASON.

THE POPULATION IS ALREADY SMALL.

THEIR FUTURE IS WRITTEN IN THE SNOW.

AS WE MOVE THROUGH MARCH, THE SNOW SHOWS NO SIGN OF LETTING UP.

IT'S FORMED BY THE COMBINATION OF COLD AIR FROM THE NORTH AND MOISTURE FROM THE PACIFIC OCEAN, AND THIS GETS TRAPPED IN THE HORSESHOE OF MOUNTAINS HERE.

UP TO 10 FEET OF SNOW CAN FALL.

THE RESULTING BLANKET OF WHITE IS ONE OF THE REGION'S MOST IMPORTANT RESOURCES.

WHEN IT MELTS, THE RUNOFF SUPPLIES WATER BOTH TO THE PACIFIC NORTHWEST AND THE AMERICAN HEARTLAND.

THE SNOWPACK IS SO CRUCIAL TO ANIMALS AND HUMANS THAT IT'S MONITORED ALL THROUGH WINTER.

I'M JOINING SCIENTISTS IN THE BEARTOOTH MOUNTAINS TO THE NORTHEAST ON THEIR COOL COMMUTE TO WORK.

LUCAS ZUKIEWICZ IS A HYDROLOGIST.

HE SPENDS WINTER CARRYING OUT HEALTH CHECKS ON THE SNOWPACK.

WHERE DO YOU DIG IT?

WE'RE GONNA PROBE AND SEE HOW MUCH WE HAVE HERE.

SO WHAT'S THAT?

ALMOST TWO METERS, 6 FEET SOMETHING LIKE THAT.

YEAH, ABOUT 70 INCHES, ALL RIGHT.

GIVE OR TAKE, SO-- HOW BIG OF A HOLE DO YOU DIG?

DEEP ENOUGH THAT THE TWO OF US CAN GET IN THERE.

SHOULDN'T TAKE US TOO LONG.

ALL RIGHT.

JOHNSON, VOICE-OVER: THERE'S NOTHING LIKE A GOOD DIG.

THIS ACTUALLY QUALIFIES AS WORK.

I'M TAKING MY COAT OFF.

YEAH.

JOHNSON: SO AS WE DIG, WE'RE GOING BACK IN TIME?

WE ARE.

WE HAVE A WORD FOR THAT IN PALEONTOLOGY.

WE CALL IT TIME TRAVEL WITH A SHOVEL.

I USUALLY GO BACK TO THE JURASSIC.

WE'RE ACTUALLY JUST GOING BACK TO OCTOBER.

NICE.

HA HA HA!

WELL, THE GOOD NEWS IS, THE GROUND'S RIGHT THERE.

SUBALPINE FIR.

JOHNSON, VOICE-OVER: TIME TO SEE WHAT THE SNOWPACK CAN TELL US.

THIS IS THE STORY OF OUR WINTER.

WE CAN SEE ALL OF OUR STORM EVENTS, STARTING OCTOBER WHEN WE FIRST STARTED GETTING SNOW HERE.

WE'RE GOING INTO NOVEMBER, THANKSGIVING, CHRISTMAS, JANUARY, FEBRUARY, MARCH.

SO THIS IS BASICALLY LIKE A 6-MONTH SNOW CALENDAR THEN?

THIS IS.

YEP.

JOHNSON, VOICE-OVER: VARIOUS MEASUREMENTS TELL LUCAS ABOUT THE SNOW THAT'S BUILDING UP.

JOHNSON: MIGHT BE ONE THERE.

NO.

IT'S JUST DENSER.

JOHNSON, VOICE-OVER: SOME ARE SOFT, AND SOME ARE HARD.

AND THERE'S ANOTHER ONE RIGHT THERE AND THEN ANOTHER ONE THERE, SO 3 IN A ROW RIGHT THERE.

YEP.

SO WE GOT SORT OF 1, 2, 3, 4, 5, 6, 7 SPOTS WHERE THERE ARE LITTLE ZONES OF FREEZING ON THE WAY DOWN HERE.

YEAH.

JOHNSON, VOICE-OVER: NEXT, TEMPERATURE.

AND MOST PEOPLE WOULD THINK THAT SNOW IS THE TEMPERATURE OF SNOW... YEAH.

BUT YOU'RE TELLING ME, THERE'S DIFFERENT TEMPERATURES OF SNOW.

JOHNSON, VOICE-OVER: ONE OF THE KEY REASONS FOR STUDYING THE ICE IS TO FIND OUT WHEN THE MELT IS ABOUT TO BEGIN.

WE'RE LOOKING FOR THE SNOWPACK TO BE ONE TEMPERATURE ALL THE WAY THROUGHOUT BEFORE IT REALLY STARTS TO DISCHARGE WATER.

YOU CAN GO RIGHT AT THE SNOW SURFACE FOR THE FIRST ONE.

OK. JUST, LIKE, WHAT, AND DRIVE IT ALL THE WAY IN?

YEP, ALL THE WAY IN.

OK.

PERFECT.

JOHNSON, VOICE-OVER: ONE MORE IN THE MIDDLE AND ONE AT THE BOTTOM.

THAT ONE'S ABOUT MINUS ONE, SO ONE DEGREE BELOW FREEZING.

THAT MAKES SENSE BECAUSE IT'S SORT OF A WARMISH DAY, AND THEN WE GET DOWN HERE, AND WE ARE MINUS MAYBE 4... MM-HMM.

AND THEN THIS GUY IS, LIKE, JUST RIGHT BACK AT FREEZING AGAIN, SO THE COLDEST IS IN THE MIDDLE.

YEP.

SO IT'S WARMER AT THE BOTTOM.

EXACTLY.

JOHNSON, VOICE-OVER: IN WINTER, HOWEVER COLD THE AIR TEMPERATURE, THE GROUND STAYS CLOSE TO ZERO DEGREES CELSIUS, OR 32 DEGREES FAHRENHEIT.

JOHNSON: SO THIS IS WHY BEARS DEN IN SNOW, BECAUSE THE SNOW IS ACTUALLY AN INSULATING BLANKET.

IT DOESN'T GET MUCH BELOW FREEZING.

EXACTLY.

IT KEEPS ALL THAT ENERGY IN, SO GENERALLY, IT'LL STAY AT FREEZING.

EVEN WHEN IT'S REALLY COLD OUTSIDE, IT'LL STAY PRETTY WARM AND KEEP THEM INSULATED.

THE WINTER'S HAPPENING OUT THERE, AND DOWN HERE, IT'S A NICE, WARM DEN.

EXACTLY.

JOHNSON, VOICE-OVER: THIS INSULATING EFFECT ALLOWS BEARS TO HIBERNATE AND KEEPS THE GRASS ALIVE FOR HERBIVORES.

THE DEEP SNOW THAT BLANKETS YELLOWSTONE IN WINTER BRINGS MIXED FORTUNES.

[WIND WHISTLING] IT MAKES LIFE TOUGH FOR SOME BUT EASIER FOR OTHERS.

[HOWLING] WOLVES LOVE DEEP SNOW.

IT'S THE REASON YELLOWSTONE'S NUMBER-ONE PREDATOR DOES SO WELL IN WINTER.

[BUGLING] THEY HAVE BIG, PADDED FEET THAT ACT LIKE SNOWSHOES THAT HELP THEM MOVE FAST ACROSS SNOW, WHILE THE ELK'S POINTY HOOVES BOG THEM DOWN.

SNOW IS THE WOLVES' BEST FRIEND... [GROWLING] AND WINTER GIVES WOLVES ANOTHER ADVANTAGE BECAUSE BY THE END OF IT, PREY ARE USUALLY WEAK AND HUNGRY, BUT THIS YEAR IS DIFFERENT.

ALTHOUGH STILL FREEZING BY MOST STANDARDS, 2016 HAS BEEN ONE OF THE MILDEST WINTERS ON RECORD.

TEMPERATURES HAVE HOVERED ALMOST 5 DEGREES FAHRENHEIT ABOVE AVERAGE.

OVERALL, IT'S MEANT LESS SNOW AND FEWER DEATHS FROM EXTREME COLD, GOOD NEWS FOR HERBIVORES BUT BAD NEWS FOR THE WOLVES.

AS MARCH PROGRESSES, IT BECOMES CLEAR THAT KILL RATES ARE DOWN.

HOW'S THAT AFFECTED THE WILDLIFE HERE?

WELL, IT'S BEEN OUR SECOND MILD WINTER IN A ROW.

JOHNSON, VOICE-OVER: DOUG SMITH IS A WOLF BIOLOGIST.

I WANT TO KNOW HOW HE THINKS THIS MILD WINTER IS AFFECTING THESE PACK-HUNTING PREDATORS.

SMITH: WINTER SEVERITY IS A VERY IMPORTANT FACTOR IN WOLF/PREY RELATIONSHIPS, AND CLIMATE CHANGE IS CHANGING THAT RELATIONSHIP.

JOHNSON, VOICE-OVER: BY TIPPING THE BALANCE OF PREDATOR AND PREY, ANY FLUCTUATIONS IN TEMPERATURE CAN, IN FACT, IMPACT THE WHOLE ECOSYSTEM.

OUR CAMERA TEAMS HAVE TRACKED WOLVES RIGHT ACROSS THE NORTHERN RANGE TO SEE HOW THE MILD WINTER IS AFFECTING THEIR HUNTS.

SO WE'VE GOT THIS GREAT CAMERA RIG ON THE TRUCK THAT LET'S US GET THESE INCREDIBLE SHOTS FROM GREAT DISTANCES OF WOLVES AND THEIR PREY, SO I WANT TO ASK YOU ABOUT A FEW OF THE BEHAVIORS THAT ARE SHOWING UP HERE.

JOHNSON, VOICE-OVER: FIRST, AN ELK HUNT.

[BUGLING] SMITH: IN GENERAL, A HEALTHY ELK WILL ALWAYS BE ABLE TO OUTRUN A HEALTHY WOLF.

PEOPLE THINK WOLVES CHASE, THEN WOLVES KILL.

IT'S TYPICALLY WOLVES CHASE, FAIL, FIND ANOTHER ELK TO ATTACK.

THEY'RE ONLY SUCCESSFUL 10% TO 15% OF THE TIME.

I'M INSPIRED BY THIS BECAUSE FAILURE IS PART OF LIFE.

YOU JUST GOT TO KEEP GOING... FAIL AND FAIL AGAIN.

AND KEEP TRYING, OR YOU DIE.

SO THEY'RE REALLY LOOKING FOR THE ONE ELK THAT'S GOT A GAME LEG OR SOMETHING LIKE THAT.

ABSOLUTELY.

I MEAN, YOUR AVERAGE WOLF IS ABOUT 100 POUNDS, YOUR AVERAGE BULL ELK 700.

THEY MAKE A MISTAKE, THEY'RE INJURED OR KILLED.

JOHNSON, VOICE-OVER: EVEN SO, ELK ARE THE EASY TARGET COMPARED TO BISON.

SO THESE WOLVES ARE JUST CREEPING IN RIGHT HERE.

WELL, THESE ARE WOLVES TESTING BISON.

WOLVES CAN'T JUST MOVE IN AND KILL SOMETHING AS LARGE AS A BISON, SO WHAT THEY HAVE TO DO IS POKE AND PROD, SO THEIR ATTACK STRATEGY IS JUST TO BE LIKE A MOSQUITO AND BOTHER THESE BISON.

JOHNSON, VOICE-OVER: THE EFFECTS OF THE MILD WINTER ARE NOW CLEAR.

SMITH: LOOK WHERE THE BISON ARE ENDING UP.

THEY'RE ENDING UP ON SNOW-FREE PATCHES SO THEY HAVE GOOD FOOTING, THEY CAN REBUFF THE WOLVES, BUT THE WOLVES WANT TO GET THEM INTO DEEP SNOW WHERE THEY CAN'T FIGHT BACK, AND THAT'S A BIG STRATEGY WE'VE SEEN TIME AND TIME AGAIN FOR WOLVES WITH BISON-- GET THEM IN A BAD SPOT.

JOHNSON, VOICE-OVER: BUT IF THERE'S NOT ENOUGH SNOW, THERE IS NO BAD SPOT.

SMITH: WHEN WE GET THESE MILD WINTERS STACKED UP, IT MAKES IT HARDER FOR WOLVES TO MAKE A KILL.

THAT COULD AFFECT THEIR REPRODUCTION, THEIR PUP SURVIVAL, AND THAT'S EXACTLY WHAT WE'RE STUDYING.

JOHNSON, VOICE-OVER: WITH SO FEW SUCCESSFUL HUNTS, SOME OF THE WOLVES WE'VE BEEN FOLLOWING HAVE TURNED TO A SUMMER FEEDING STRATEGY.

THEY'RE HUNTING ALONE, DIGGING IN THE SNOW TO CATCH SMALL MAMMALS.

IT'S HARDER WORK, LESS REWARDING, AND FOR THIS TIME OF YEAR, VERY UNUSUAL.

THERE COULDN'T BE A WORSE TIME FOR THE WOLVES TO GO HUNGRY BECAUSE NOW THE FEMALES ARE PREGNANT.

WE'LL ONLY KNOW THE EFFECT ON THE CUBS WHEN THEY START TO APPEAR IN EARLY SUMMER.

[WIND WHISTLING] IT'S THE END OF MARCH.

THE SNOW IS FINALLY STARTING TO MELT FASTER THAN IT'S FALLING.

WARMER AIR FROM THE SOUTH HAS PUSHED OUT THE COLD FRONT.

DAYTIME TEMPERATURES ARE NOW ABOVE FREEZING.

MORE AND MORE GRIZZLIES ARE EMERGING FROM HIBERNATION...

SO BEAR EXPERT CASEY ANDERSON IS HEADING UP TO THE GALLATIN MOUNTAINS TO SEE WHO HE CAN FIND.

[CREAK] GUESS I WEIGH MORE THAN A COYOTE.

JOHNSON, VOICE-OVER: IT'S NOT TOO HARD TO WORK OUT WHERE THEY'VE BEEN.

LOOK.

YOU CAN SEE HERE, IT'S ALL KIND OF WORE OUT.

YOU SEE THESE LITTLE CLAW MARKS?

WELL, SOMETIMES WHEN THE BEARS COME OUT OF THE DEN, THEY CAN BE A LITTLE MISCHIEVOUS, AND IF YOU LOOK RIGHT HERE, ONE OF THE FIRST STOPS A BEAR HAD MADE WAS THIS SNOWMOBILE SEAT, JUST RIPPING, CLAWING, BITING, JUST PLAYING, REALLY.

IT'S PART OF LIVING IN GRIZZLY COUNTRY.

JOHNSON, VOICE-OVER: YOU CAN NEVER TELL EXACTLY WHEN BEARS WILL EMERGE, AND THIS YEAR IS MORE UNPREDICTABLE THAN EVER.

YOU KNOW, IT'S BEEN REALLY A STRANGE YEAR SO FAR.

THOSE SPRING TEMPERATURES DEFINITELY HAS GOTTEN A FEW BEARS OUT EARLY, AND WE KNOW THAT ONE BEAR HAS GONE DOWN, PULLED THAT BISON CARCASS OUT OF THE POND.

THAT WAS A RISK WORTH TAKING.

JOHNSON, VOICE-OVER: BUT IT WAS A RISK.

OTHER EARLY GRIZZLIES MAY NOT HAVE BEEN SO LUCKY.

THE DAYS MAY BE WARMER, BUT IT'S NOT SPRING YET.

RIGHT UP HERE, THERE'S A LONG-TAILED WEASEL.

HE'S RUNNING AROUND RIGHT UP HERE.

SO THESE LONG-TAILED WEASELS, AS SOON AS SPRING ACTUALLY IS HERE, THEY WILL TURN BROWN, AND THEY'LL BE CAMOUFLAGED FOR THE SPRING, SUMMER, AND FALL, AND WINTER COMES AGAIN, AND THEY TURN WHITE JUST LIKE THIS.

THE FACT THAT HE'S STILL COMPLETELY WHITE SHOWS THAT IT'S VERY MUCH WINTER.

JOHNSON, VOICE-OVER: THE CHANGE IN COLOR IS TRIGGERED BY LENGTH OF DAY, NOT TEMPERATURE.

HE WON'T TURN BROWN UNTIL NEXT MONTH.

AND JUST LIKE THE FOX AND THE COYOTES, HE'S LOOKING FOR ALL THE RODENTS THAT LIVE UNDERNEATH THE SNOW COVER.

HE'S JUST TUNNELING DOWN, GOING AND GRABBING THESE THINGS, AND POPPING UP AND EATING THEM.

JOHNSON, VOICE-OVER: YELLOWSTONE'S SMALLER PREDATORS GRAB THEIR MEALS FROM UNDER THE SNOW.

EACH HAS ITS OWN TECHNIQUE.

YOU CAN SEE THIS, LIKE, LITTLE STORY UNFOLDING HERE.

THIS IS A FOX DOING WHAT THEY'RE SO GOOD AT IN THE WINTERTIME.

A BEAR'S GREATEST SENSE IS THEIR SENSE OF SMELL, WHEREAS A FOX'S GREATEST SENSE IS THEIR SENSE OF HEARING, AND THEY LITERALLY HEAR A LITTLE RODENT WAY DOWN IN THE SNOW.

THEY'LL STOP, AND--YOU'LL SEE THEM--THEY'LL DO THIS THING WHERE THEY PITCH THEIR HEADS SIDE TO SIDE, AND WHAT THEY'RE DOING IS REALLY TRIANGULATING AND ZONING IN AT THE EXACT LOCATION OF THAT RODENT, AND THEN THEY JUST DO THIS GIANT LEAP UP IN THE AIR AND GET THIS MOMENTUM WITH GRAVITY, AND JUST, POOF, RIGHT DOWN THROUGH THE SNOW AND GRAB THAT LITTLE GUY.

HE DOESN'T EVEN KNOW IT'S COMING.

A LITTLE VOLE IS A PRETTY GOOD SNACK FOR A FOX, WHEREAS FOR A BEAR, IT'S NOTHING, AND THERE'S NO WAY IT COULD JUST SURVIVE ON VOLES ALONE THROUGH THE WINTER, SO THAT'S WHY THEY CHOOSE TO HIBERNATE.

THERE'S JUST NOTHING OUT THERE TO EAT IF YOU'RE A BIG, OLD, BUMBLING-AROUND BEAR.

JOHNSON, VOICE-OVER: DOWN IN THE SOUTH, THERE'S STILL PLENTY OF SNOW IN THE FORESTS THAT ARE HOME TO THE GREAT GRAY OWLS.

CAMERAMAN JEFF HOGAN HAS BEEN TRACKING THE BIRDS HERE DAY AND NIGHT.

HOGAN: I CAN SEE HIM LISTENING.

I LOVE THAT.

JOHNSON, VOICE-OVER: HE'S BEEN HEARING AND SEEING THE MALE OWLS CONSISTENTLY, WHICH IS REASSURING, BUT HUNTING STILL APPEARS TO BE PROBLEMATIC.

HE DIDN'T CATCH ANYTHING.

I'VE BEEN HERE SINCE DAWN, AND HE HASN'T CAUGHT ANYTHING YET TODAY.

JOHNSON, VOICE-OVER: THIS YEAR, ICY SNOW HAS BEEN AN ISSUE.

IT'S PREVENTED THE GREAT GRAYS FROM PLUNGING DEEP ENOUGH IN THE SNOW TO CATCH PREY.

EACH OWL NEEDS AT LEAST ONE RODENT A DAY, AND IF THEY DON'T GET ENOUGH TO EAT, THEY WON'T BREED.

THEN, AT LAST, JEFF SPOTS A FEMALE.

IT'S A GREAT SIGN.

IT MEANS OUR OWL'S LUCK MIGHT BE CHANGING.

THIS COULD GET EXCITING.

WE'VE GOT TWO GREAT GRAYS RIGHT HERE.

FOLLOWING ONE BIRD IS PRETTY EXCITING, BUT TO HAVE TWO BIRDS, IT'S AMAZING.

IT REALLY IS AMAZING.

MATING.

MATING.

OH, MY.

[CAMERA SHUTTER CLICKS] THIS IS GREAT NEWS.

IT'S INCREDIBLE, ABSOLUTELY INCREDIBLE.

NEXT STEP IS NESTING.

JOHNSON, VOICE-OVER: AT LAST, APRIL HAS ARRIVED... AND TEMPERATURES ARE ON THE RISE.

[WATER FLOWING] JACKSON LAKE, STRETCHING 15 MILES, IS GRAND TETON'S LARGEST LAKE.

IT SHOULD STILL BE FROZEN, BUT THIS IS AN EXCEPTIONAL YEAR.

THE THAW HAS BEGUN 3 WEEKS EARLY.

THE MELT HAS STARTED IN THE VALLEYS, AND OVER THE NEXT FEW MONTHS, IT WILL GRADUALLY MOVE UP TO THE PEAKS.

SOON, ALL THIS SNOW WILL TRANSFORM INTO MILLIONS OF TONS OF WATER THAT WILL FLOOD INTO THE SURROUNDING LAKES AND RIVERS.

THE WARMER TEMPERATURES ARE LURING GRIZZLIES OUT OF HIBERNATION.

THEIR EMERGENCE IS PERFECTLY TIMED TO COINCIDE WITH THE NEW SPRING PLANTS.

THESE GREAT, HULKING BEARS DON'T JUST EAT MEAT, BUT INCLUDE SEEDS, BERRIES, INSECTS, FUNGI, AND PLANTS IN THEIR DIET.

ONE OF THE FIRST TO APPEAR IS A STAPLE OF THEIRS--BISCUITROOT, A RELATIVE OF THE CARROT AND EQUALLY NUTRITIOUS.

MAKE YOURSELF LOOK FEROCIOUS... JOHNSON, VOICE-OVER: I'M BACK IN THE NORTH WITH CASEY ANDERSON TO FIND OUT MORE ABOUT THE GRIZZLY'S VEGETARIAN OPTIONS.

THIS IS WHAT THE BEARS ARE LOOKING FOR IMMEDIATELY WHEN THEY COME OUT OF THE DEN, AND OBVIOUSLY THEY HAVEN'T BEEN EATING FOR UP TO 6 MONTHS.

THEY'RE LOOKING FOR THIS LITTLE, YELLOW FLOWER?

WELL, NOT EXACTLY THE FLOWER.

IN FACT, THIS IS WHERE THEY UTILIZE THOSE BIG, SHOVEL-LIKE CLAWS BECAUSE THEY'LL JUST GET IN THERE AND DIG.

THIS IS CALLED BISCUITROOT... NICE.

AND THEY'LL JUST GO AND EAT HUNDREDS, IF NOT THOUSANDS, OF THESE ROOTS EVERY DAY, PACKS A LOT OF ENERGY.

THAT'S REALLY GOOD.

LET'S DIG UP ANOTHER ONE.

THESE ARE REALLY NICE, ACTUALLY.

THEY ARE REALLY GOOD.

IT'S LIKE A SLIGHTLY COOKED TURNIP OR SOMETHING LIKE THAT.

IT WAS ACTUALLY QUITE LOVELY.

I'M PART BEAR.

LIFE IS GOOD.

JOHNSON, VOICE-OVER: WHEN THIS FLOWER IS OUT, THE BEARS ARE OUT, TOO.

THE RANGE OF EACH MALE CAN BE SEVERAL HUNDRED SQUARE MILES, SO THEY NEED TO WORK OUT WHO ELSE IS ON THEIR PATCH.

CASEY'S SET UP CAMERAS TO CATCH THEM IN ACTION.

WE GOT THEM SPREAD EVERYWHERE, BUT I'VE SET ONE UP ON THIS TREE FOR A REASON.

JOHNSON, VOICE-OVER: THIS IS A WELL-KNOWN RUB TREE, A SPOT WHERE BEARS LEAVE THEIR SCENT TO ANNOUNCE THEIR PRESENCE.

ANDERSON: NOW I'M STARTING TO GET SOME ACTION ON HERE.

JOHNSON: A WHITE RABBIT.

HA HA!

BOBCAT.

WOW, THAT IS REALLY COOL.

SO COOL.

YOU GET ALL THESE VISITORS, AND THEY SHOW OFF THEIR PERSONALITY.

OH!

HA HA HA!

HA HA HA!

YOU CAN SEE THAT THIS ELK IS BEING MISCHIEVOUS.

EVERY TIME I GO GRAB A CAMERA TRAP, IT'S LIKE OPENING A PRESENT.

JOHNSON, VOICE-OVER: THE GIFT CASEY REALLY WANTS IS A BEAR.

AND YOU'LL SEE HERE... WHOA!

THIS GUY JUST GOT OUT OF A DEN, AND YOU CAN TELL JUST BY HIS HAIR COAT.

IT'S JUST COMPLETELY FULL, STILL LOOKS REALLY GOOD, AND THIS IS WHAT I EXPECT-- A BIG MALE COMING DOWN, MARKING HIS TERRITORY.

THAT IS A HUGE BOAR, MAN.

JOHNSON, VOICE-OVER: RUBBING THEIR BACKS AGAINST THE TREE SPREADS THEIR SCENT ALL OVER IT.

HA HA HA!

THAT'S AWESOME.

HA HA!

BEAR HUG.

HA HA HA!

HA HA HA!

IF THERE'S ANY LITTLE TREES OFF TO THE SIDE, OFTEN THEY'LL JUST, LIKE, PLOW THROUGH THEM AND KNOCK THEM DOWN, EVEN THE LITTLE SAPLINGS LIKE, THIS BIG AND URINATE ALL OVER THEM, AND THEY JUST MAKE A MESS, REALLY, AND MARK IT UP, REALLY, SO THERE'S NO DOUBT, ESPECIALLY WHEN THEY'RE A BIG BOAR LIKE THAT, THAT, "HEY, I'VE BEEN HERE."

"LET IT BE KNOWN, I HAVE WOKEN UP."

JOHNSON, VOICE-OVER: A BEAR AS HUGE AS THIS IS, NO DOUBT, THE BIGGEST IN THIS AREA.

YOU SEE HE'S DOING THIS KIND OF STIFF-LEGGED WALK--WE CALL IT THE COWBOY WALK-- WHERE THEY KIND OF GET BOWLEGGED AND THEY STOMP THEIR FEET IN GROUND, LEAVE THESE DIVOTS, SO THE LITTLER BEAR WILL COME ALONG AND GO, "OOH, THAT'S A LITTLE FARTHER "THAN IT NEEDS TO BE, AND MAYBE "I'M NOT THE BIGGEST BEAR HERE.

A BIG GUY'S ALREADY CHECKED IN."

THE FIRST SIGNS OF SPRING, HUH?

YEP.

THIS IS THE FIRST SIGN OF SPRING.

I WOULD NEVER HAVE THOUGHT THAT.

WAKE UP, SCRATCH YOUR BACK, AND GET MOVING.

JOHNSON, VOICE-OVER: SPRING IS IN THE AIR.

THE UNUSUAL WEATHER BROUGHT SOME BEARS OUT OF THEIR DENS EARLY, BUT THEY'RE BACK ON TRACK.

GRIZZLIES AREN'T THE ONLY MALES SIZING EACH OTHER UP.

THE ELK ARE SHEDDING THEIR ANTLERS SO THAT THEY CAN GROW NEW ONES IN TIME FOR THE AUTUMN RUT.

[CHIRPING] THE MALE SAGE GROUSE ARE SHOWING OFF THEIR MATING MOVES.

THE BEST PERFORMANCE WINS THE FEMALE.

[CHIRPING] IT'S OFFICIAL.

SPRING IS FINALLY HERE.

EARLIER IN MARCH, THE GREAT GRAY OWLS WERE SEEN MATING, DESPITE THE POOR HUNTING CONDITIONS.

THE QUESTION NOW IS, HAVE THEY NESTED?

I'M HEADED BACK WITH OWL EXPERT BRYAN BEDROSIAN TO FIND OUT.

THERE WOULD HAVE BEEN A TON OF SNOW HERE A COUPLE OF WEEKS AGO.

YEAH.

SNOW WAS 3, 4 FEET UP THESE TREES.

SAGEBRUSH WAS COMPLETELY COVERED.

JOHNSON, VOICE-OVER: CAMERAMAN JEFF HOGAN HAS BEEN KEEPING AN EYE ON THE OWLS SINCE THEY MATED... AND...

SUCCESS.

JOHNSON: IS SHE IN THE NEST?

SHE'S IN THE NEST ON EGGS.

OH, VERY COOL.

SHE'S HAVING A LOOK AT US RIGHT NOW, TOO.

THAT'S VERY COOL.

YOU CAN SEE HER HEAD RIGHT HERE.

YEAH.

YOU CAN SEE HER EYES.

WOW.

THAT'S MY FIRST GREAT GRAY OWL, MAN.

THANK YOU.

THAT'S AWESOME.

ISN'T THAT GREAT?

WOW.

SUCH A UNIQUE EXPERIENCE, TO SEE THESE GUYS.

SHE JUST KEEPS LOOKING OVER AT US GOING, "WHAT ARE THOSE GUYS DOING OUT THERE?"

JOHNSON, VOICE-OVER: BRYAN RECOGNIZES THIS NEST.

IT WAS USED BY GREAT GRAYS LAST YEAR, TOO.

NO OWL BUILDS A NEST, SO THEY HAVE TO USE WHAT'S AVAILABLE, AND HERE, YOU KNOW, THIS BIRD'S USING AN OLD REDTAIL NEST.

SHE BARELY FITS IN IT.

SHE'S, LIKE, HALF STICKING OUT OF THE NEST.

JOHNSON, VOICE-OVER: THIS MOTHER LIKELY HAS TWO OR 3 EGGS TUCKED BENEATH HER.

SHE CAN'T LEAVE THIS SPOT FOR 30 DAYS.

SO THE MALE RIGHT NOW IS PROBABLY ROOSTING NEARBY IN ONE OF THESE TREES.

HOGAN: HE'LL SUPPLY HER WITH FOOD THROUGHOUT HER WHOLE INCUBATION PERIOD.

JOHNSON: SHE KEEPS DOING THIS WHOLE ROTATION OF HER HEAD, LOOKING BACK AT US, WATCHING US WITH MALICE.

YEAH, YEAH, JUST MAKING SURE WE DON'T GET TOO CLOSE.

YEAH, YEAH.

OH, MAN, IT'S A BEAUTIFUL BIRD, MAN.

JOHNSON, VOICE-OVER: JEFF CONTINUES TO FILM THE GREAT GRAYS OVER THE COMING WEEKS.

SOON, HE COMES ACROSS HIS FIRST CHICKS.

IT SEEMS, THIS PAIR HAS WEATHERED WINTER'S CHALLENGES.

[CHIRPS] WE'LL BE FOLLOWING THESE CHICKS TO SEE IF THEY SURVIVE THE SPRING.

SO FAR DURING THE THAW, WE'VE SEEN WILDLIFE WINNERS AND LOSERS.

THE TEMPERATURE SPIKE AT THE END OF WINTER CONFUSED THE BEARS... AND MADE LIFE DIFFICULT FOR THE OWLS.

A MILD WINTER AND A LACK OF SNOW LEFT THE WOLVES HUNGRY...

BUT THE ELK AND BISON CAME OUT OF THE WINTER IN GREAT SHAPE.

SOON, THIS LANDSCAPE WILL BE TRANSFORMED.

SPRING WILL MEAN RELIEF FOR SOME BUT CHALLENGES FOR OTHERS.