Original subtitles

Narrator: A PANORAMA OF LIFE AND A LANDSCAPE LIKE NO OTHER.

A PLACE WHERE ANCIENT CONFLICTS PLAY OUT IN A FRAGILE BALANCE.

BUT SOMETHING HAS TILTED THAT BALANCE DANGEROUSLY,

AND THE PARK'S MAGNIFICENT ELK ARE DISAPPEARING.

BUT WHO IS THE CULPRIT?

THE WOLF, REINTRODUCED 20 YEARS AGO,

RIGHT WHEN THE ELK NUMBERS CRASHED?

GRIZZLIES, WHO HAVE ALWAYS PREYED

ON THE YOUNGEST AND MOST VULNERABLE ELK?

[THUNDER]

OR IS IT SOMETHING MORE INSIDIOUS AND BAFFLING?

[BANG]

NOW SCIENTISTS ARE RACING TO SOLVE THE MYSTERY

OF THE DISAPPEARING ELK IN...

MYSTERY IN YELLOWSTONE.

♪

[HELICOPTER]

♪

THE SEARCH FOR SUSPECTS IN THIS MYSTERY

BEGINS WITH THE VICTIMS THEMSELVES.

ONLY TWO DECADES AGO, THE PARK WAS THICK WITH THESE ELK...

NEARLY 20,000 OF THEM.

NOW LESS THAN A QUARTER OF THEM REMAIN.

[BANG]

WILDLIFE BIOLOGISTS NEED TO MONITOR THE HERD'S EVERY MOVE

AND THE HEALTH OF ITS MEMBERS...

AND A ROUND-UP BY HELICOPTER

IS THE QUICKEST WAY TO CAPTURE CRITICAL INFORMANTS.

IT LOOKS BRUTAL, BUT THE SCIENTISTS HAVE LEARNED

THAT THIS IS ONE OF THE LEAST TRAUMATIC WAYS

TO RECRUIT VOLUNTEERS FOR THEIR MISSION.

THEY MOVE QUICKLY TO RESTRAIN THE ANIMALS

AND GET THE SAMPLES THEY NEED.

BIOLOGIST ARTHUR MIDDLETON HAS SPENT THE LAST FEW YEARS

WRESTLING WITH THE STRANGE AND UNNERVING ELK DECLINE.

Arthur Middleton: THE QUESTIONS WERE PRESSING,

THE PROJECT WAS ALREADY READY TO GO,

AND SO I CAME ACROSS THE STATE FROM THE UNIVERSITY

UP TO NORTHWEST WYOMING

AND I STARTED MY FIELD WORK.

Narrator: AFTER MAKING SURE THE ELK COW IS SAFELY RESTRAINED,

HE TAKES BLOOD SAMPLES THAT WILL BE CHECKED FOR SIGNS

OF DISEASE, STARVATION, STRESS, AND PREGNANCY.

THEN HE FITS THE COW WITH A GPS COLLAR

THAT WILL TRANSMIT HER POSITION EVERY THREE TO FIVE HOURS.

THE TEAM AIMS TO GET EVERY ANIMAL CAPTURED AND RELEASED

IN LESS THAN 8 MINUTES AND WITHOUT ANY SEDATION.

AND THEN THE NEWLY RECRUITED INFORMANT IS FREE AGAIN...

UNAWARE JUST HOW MUCH VITAL INFORMATION

SHE'LL BE GIVING MIDDLETON AND HIS TEAM...

AND THAT SHE COULD HELP EXPOSE THE KILLER OF HER KIND.

[BUGLING]

THERE ARE MANY POTENTIAL CULPRITS

IN THE DECLINE OF THE HERD,

BUT THE FIRST ONE ON EVERYONE'S MIND IS THE WOLF.

LONG MISSING FROM YELLOWSTONE,

THE WOLF ARRIVED BACK ON THE SCENE

RIGHT WHEN THE ELK NUMBERS BEGAN TO CRASH.

TOO MUCH OF A COINCIDENCE, IN THE MINDS OF MANY.

BUT PINNING THE CRIME ON THE RETURN OF THE WOLF

REQUIRES PROOF.

WOLVES, ONCE CONSIDERED DANGEROUS VERMIN,

WERE SYSTEMATICALLY EXTERMINATED

FROM THE TIME THE PARK WAS FOUNDED IN 1872.

BY THE 1920s, THEY WERE GONE,

AND THE PARK WAS TURNED INTO A SAFER PLAYGROUND FOR TOURISTS.

Film narrator: YOU'VE JUST ENTERED YELLOWSTONE NATIONAL PARK.

YOU'RE A MILE AND A HALF ABOVE SEA LEVEL,

AND THE AIR IS CLEAR AND INVIGORATING.

ALL AROUND US IS THE EVIDENCE OF THE PARK'S VOLCANIC ORIGIN.

ALL THE FLOWERS AND FORESTS AND MOUNTAINS ARE RESERVED FOR YOU.

♪

Narrator: THE YELLOWSTONE NATIONAL PARK STRADDLES THE CONTINENTAL DIVIDE

OF THE NORTHERN ROCKY MOUNTAINS IN WYOMING.

IT'S THE HEART OF THE GREATER YELLOWSTONE ECOSYSTEM...

AN AREA OF ALMOST 30,000 SQUARE MILES.

[ELK BUGLING]

IT LOOKED PRISTINE...

BUT WITHOUT THE WOLF,

YELLOWSTONE WAS AN ECOSYSTEM OUT OF BALANCE.

THE ELK POPULATION EXPLODED TO UNSUSTAINABLE LEVELS.

BUT IN 1995, 70 YEARS AFTER THE LAST WOLF HAD BEEN KILLED,

THE PARK DID SOMETHING RADICAL:

THEY IMPORTED A PACK OF WOLVES FROM CANADA

AND RELEASED THEM INTO YELLOWSTONE.

Middleton: THE WOLF HAD BEEN REINTRODUCED IN THE MID 1990s,

AND IT WAS A HUGE SUCCESS BIOLOGICALLY.

THEIR POPULATION NUMBERS GREW VERY RAPIDLY,

AND THEY EXPANDED FAR OUTSIDE OF YELLOWSTONE PARK

INTO THE SURROUNDING REGION.

Narrator: THE WOLVES IMMEDIATELY SET ABOUT DOING

WHAT THE PARK BIOLOGISTS HAD HOPED...

HUNTING THE OVERPOPULATED ELK WITH A VENGEANCE,

BRINGING DOWN ELK NUMBERS

BUT ACTUALLY IMPROVING THE HEALTH OF THE HERDS.

♪

[ELK BUGLING]

♪

BUT NOT EVERYONE WAS THRILLED.

HUNTERS WHO COMPETE WITH WOLVES FOR ELK

AND RANCHERS WHO FEARED FOR THEIR LIVESTOCK

PREDICTED THE WOLVES WOULD CAUSE A CATASTROPHE.

♪

20 YEARS LATER,

IT WAS BEGINNING TO LOOK LIKE THE WOLF-HATERS WERE RIGHT.

ELK NUMBERS HAD PLUMMETED BY 80%.

AND AS A FEW DOZEN WOLVES BECAME HUNDREDS,

PRESSURE GREW TO SHUT DOWN THE RETURN OF THE WOLF.

Middleton: THE TIME DREW CLOSER AND CLOSER

FOR THEIR PROTECTIONS TO BE LIFTED,

AND THAT MEANS THEIR MANAGEMENT SHIFTS

FROM A PROTECTION POSTURE TO MORE OF A HARVEST POSTURE,

WHERE THE PUBLIC IS PERMITTED TO HUNT WOLVES.

Narrator: THE SITUATION WAS URGENT:

IF WOLVES COULD BE HUNTED AGAIN,

THE WHOLE SUCCESS OF THE PARK'S ATTEMPT

TO RETURN YELLOWSTONE TO ITS ORIGINAL BALANCE

WAS IN DANGER.

ENTER DR. MIDDLETON,

A YOUNG BIOLOGIST SENT TO DETERMINE

WHETHER THE WOLF WAS NOT JUST A SUPREME PREDATOR

BUT A MASS MURDERER.

Middleton: I CAME HERE TO FIND THE ANSWER TO A QUESTION

THAT A LOT OF PEOPLE LOCALLY AND A LOT OF SCIENTISTS

HAD ASKED, WHICH IS:

DOES THE PRESENCE OF WOLVES SCARE ELK SO MUCH

THAT THEY'RE LOSING FAT, THEY'RE STRESSED OUT,

AND THEY'RE NOT REPRODUCING?

SO I HAD TO GO OUT IN THE FIELD AND STARE AT ELK.

Narrator: MONITORING THE HERD THROUGH THE BRUTAL WINTERS

IN THEIR TERRITORY IN THE LOWER NORTHERN RANGES

ISN'T EXACTLY ALL IT'S CRACKED UP TO BE.

Middleton: CONTRARY TO WHAT I WAS LED TO BELIEVE,

ELK DON'T REALLY DO VERY MUCH.

THEY'RE CERTAINLY NOT RUNNING INTO WOLVES ALL THAT MUCH,

AND THEY'RE MOSTLY JUST DIGGING AROUND IN THE SNOW FEEDING

ALL DAY.

Narrator: THE ELK CERTAINLY DON'T LOOK STRESSED,

AND THEY BARELY GLANCE UP

AT ANY WOLF THAT ISN'T WITHIN SPRINTING DISTANCE.

THE RESULT OF THE BLOOD TESTS

CONFIRM WHAT MIDDLETON IS SEEING IN THE FIELD:

THE COW ELK ARE IN EXCELLENT HEALTH,

AND OVER 70% OF THE FEMALES ARE PREGNANT.

STRESS CAN PREVENT PREGNANCY AND CAUSE MISCARRIAGE,

SO THAT DOESN'T SEEM TO BE THE PROBLEM.

BUT ANOTHER RESULT IS DISTURBING:

THE TESTED FEMALES ARE OLDER THAN EXPECTED.

ONLY A HANDFUL IS UNDER 9 YEARS OLD,

FAR PAST AN ELK'S PRIME.

THEY GENERALLY DON'T LIVE PAST 15.

[BUGLING]

THE HERD ISN'T JUST SHRINKING; IT'S BECOMING GERIATRIC.

IN WINTER, THE ELK HERD SEEMS HEALTHY AND RELAXED...

JUST OLD.

SOMETHING MUST BE HAPPENING TO THEM

AT SOME OTHER TIME OF THE YEAR, KILLING OFF THE YOUNG ELK.

SPRING IS COMING,

MEANING THE MASS MIGRATION OF PREY ANIMALS

IN SEARCH OF BETTER GRAZING.

MANY OF MIDDLETON'S COLLARED ELK

ARE HEADED TO THE HIGH PLAINS IN THE INTERIOR OF THE PARK,

WHERE THERE WILL BE RICH PASTURE,

JUST IN TIME FOR CALVING.

COULD SOMETHING BE HAPPENING

DURING THE LONG AND ARDUOUS TREK?

Middleton: ONE OF THE MOST IMPORTANT THINGS

THAT HAPPENS THIS TIME OF YEAR

IS THE MIGRATION OF THE LARGE HERBIVORES...

THE ELK, THE MOOSE, THE PRONGHORN ANTELOPE,

THE MULE DEER, THE BIGHORN SHEEP.

ALL THOSE ANIMALS, THOUSANDS AND THOUSANDS,

TENS OF THOUSANDS OF ANIMALS ARE MOVING TO THEIR SUMMER HABITAT,

NEARER TO THE CORE OF YELLOWSTONE,

AND ELK ARE THE DOMINANT MIGRATORY ANIMAL.

Narrator: AS THE ELK SLOWLY MIGRATE

BACK UP INTO THE YELLOWSTONE NATIONAL PARK,

THEY PASS THROUGH DIFFERENT WOLF TERRITORIES...

WITH MIDDLETON ON THEIR HEELS.

BUT ONCE AGAIN, HE FINDS OUT

THAT ENCOUNTERS BETWEEN ELK AND WOLVES

REMAIN EXTREMELY RARE,

AND THE ELK SHOW NO SIGN OF STRESS.

BY MAY, THEY REACH THE HIGH PLATEAU IN THE INTERIOR,

WHERE NEW, RICH GRASSES AND MILD TEMPERATURES

SET THE STAGE FOR A NEW SEASON...

AND A NEW DRAMA.

[WOLF HOWLING]

AS NIGHT FALLS, THE FEMALES SLIP AWAY FROM THE HERD

AND PREPARE TO WELCOME A SLEW OF NEWCOMERS INTO THE WORLD

AND A WHOLE NEW SET OF VULNERABILITIES.

[HOWLING]

THE NIGHT IS CALM, BUT THE DAWN WILL BRING TROUBLE.

♪

DAYBREAK REVEALS THE YEARLY MIRACLE...

OVERNIGHT, YELLOWSTONE COUNTRY HAS BECOME A MASSIVE NURSERY.

[GEESE HONKING]

♪

THE CALVES CAN STAND WITHIN HOURS,

BUT THEY WON'T BE ABLE TO RUN WITH THE HERD FOR TWO WEEKS.

SO THEIR MOTHERS KEEP THEM APART AND KEEP A CLOSE EYE ON THEM.

♪

THE SHEER NUMBER OF ELK CALVES, ALMOST ALL IN GOOD HEALTH,

CLEARLY SHOWS THAT THE ELK PREGNANCIES

HAVE NOT BEEN AFFECTED BY THE PRESENCE OF WOLVES.

BUT THE PREDATORS SENSE A NEW OPPORTUNITY...

THERE ARE YOUNG PREY ANIMALS EVERYWHERE.

WOLVES ARE DEVOTED PARENTS;

THE WHOLE PACK WILL DO WHAT IT CAN TO FEED THEIR PUPS.

BEAR FAMILIES HAVE EMERGED FROM HIBERNATION,

AND THE MOTHERS HAVEN'T EATEN IN MONTHS.

EVEN SCAVENGERS WILL TURN INTO HUNTERS

WHEN SPRING CALVES ARE EVERYWHERE FOR THE PICKING.

BUT THE HUNTERS NEED TO CHOOSE THE HUNTED CAREFULLY.

BISON CALVES WOULD SEEM RIPE FOR THE PICKING,

BUT THEY'VE ALREADY JOINED THE HERD

AND ARE PROTECTED BY GIANTS.

ELK CALVES ARE SMALLER

AND STILL DON'T HAVE THE PROTECTION OF THE HERD.

ELK MOTHERS, TOO, ARE EXTREMELY PROTECTIVE...

BUT YOUNG MOTHERS CAN MAKE MISTAKES.

MOM KNOWS THAT WATER MEANS SAFETY

FROM ALMOST ALL PREDATORS...

BUT THE LITTLE CALF ALSO KNOWS

THAT HE'S NO MATCH FOR RAGING MELTWATER.

IT COULD BE A COSTLY MISTAKE.

WOLVES ARE ON THE LOOKOUT FOR UNPROTECTED YOUNGSTERS.

[WOLF HOWLING]

BUT MOTHER SOON REALIZES HER MISTAKE;

SHE HEADS BACK ACROSS THE RIVER.

♪

FORTUNATELY FOR HER,

HER CALF HAS HIS OWN DEFENSE THAT FOILS THE WOLF.

♪

HE, LIKE ALL NEWBORN ELK CALVES, HAS ALMOST NO SCENT...

AND EVEN THE KEEN-NOSED CANINE CAN'T SMELL HIM.

IT'S A BRILLIANT DEFENSE,

ALLOWING THE MOTHER TO WANDER AND GRAZE

WHILE HER CAMOUFLAGED BABY HUNKERS DOWN

AND DISAPPEARS INTO THE LANDSCAPE.

AND MEANWHILE MOTHER ISN'T GIVING AWAY WHERE HER BABY IS.

IF WOLVES GET TOO CLOSE FOR COMFORT,

SHE'LL GET RIGHT IN THEIR FACES TO LEAD THEM AWAY FROM HER CALF,

KNOWING SHE'S FAST ENOUGH

TO REACH THE SAVE HAVEN OF WATER...

AND GUTSY ENOUGH TO KEEP THEM AT BAY.

Middleton: ELK ARE VERY SOPHISTICATED ANIMALS,

SO EVEN WHEN WOLVES SHOW UP, THEY CAN RUN AWAY,

THEY CAN STAND THEIR GROUND,

THEY CAN ASSESS HOW VULNERABLE AM I?

HEY, I'M FIVE YEARS OLD; I'M IN TOP SHAPE.

MY LEGS ARE FINE; MY HEALTH IS FINE.

I DON'T HAVE ANYTHING TO WORRY ABOUT.

[BIRDS CHIRPING]

Narrator: AS SUMMER APPROACHES,

THE DECLINE OF THE ELK IS STILL A MYSTERY.

THE INVESTIGATORS ARE ABOUT TO COUNT THE CALVES AGAIN.

AND THE RESULT IS DISTURBING.

Middleton: YOU COULD HAVE AS MANY CALVES AS COWS

BECAUSE EVERY COW CAN HAVE ONE CALF,

SO, IN LATE SUMMER, ONLY A FEW MONTHS AFTER CALVING

WE COUNT HOW MANY CALVES THERE ARE,

AND IF THERE'S VERY FEW CALVES,

THEN SOMETHING DURING THE SUMMER,

UP ON THE SUMMER RANGE,

IS CAUSING THE LOSS OF THOSE CALVES.

Narrator: BY SUMMER'S END,

ONLY A THIRD OF THE CALVES ARE STILL ALIVE.

ARTHUR MIDDLETON NEEDS TO REASSESS.

THE ELK COWS WERE IN GOOD PHYSICAL CONDITION

IN THE WINTER,

WITH MOST OF THEM PREGNANT

AND SHOWING NO SIGNS OF WOLF-INDUCED STRESS.

THE HERD IS OLD, BUT THEY'RE CARRYING THE CALVES TO TERM

AND GIVING BIRTH TO HEALTHY YOUNG.

BUT THEN THEY START TO DISAPPEAR,

AND, EVEN THOUGH THE ELK NUMBERS WENT INTO FREE FALL

AT THE SAME TIME AS THE REINTRODUCTION OF THE WOLF,

THERE'S NO SMOKING GUN HERE...

FOR THE SCIENTISTS REALIZED, THROUGH MONITORING BOTH SPECIES,

THE WOLVES AREN'T TAKING NEARLY ENOUGH OF THEM

TO ACCOUNT FOR THE ELK'S DECLINE.

[HOWLING]

Middleton: WOLVES ARE ONLY ONE OF FIVE PREDATORS...

ACTUALLY SIX IF YOU COUNT HUMANS...

THAT EAT ELK, AND THEY WERE NOT AFFECTING THESE ELK

AS STRONGLY AS EVERYBODY SAID THEY WERE.

AND SO I SPENT A LOT OF TIME

FINDING OUT WHAT WAS NOT GOING ON;

I NEEDED TO FIND OUT WHAT WAS GOING ON.

♪

Narrator: SINCE HUNTING WITHIN THE PARK BOUNDARIES

IS PROHIBITED

AND OTHER PREDATORS

SUCH AS MOUNTAIN LIONS AND WOLVERINES ARE RARE...

♪

BEARS ARE PRIME SUSPECTS.

AND YELLOWSTONE IS HOME TO TWO KINDS...

BLACK AND GRIZZLY BEARS.

IS EITHER OF THESE BEARS TO BLAME FOR THE DISAPPEARING ELK?

♪

Middleton: WOLVES EAT SOME ELK, OF COURSE THEY DO,

BUT GRIZZLY BEARS ARE ESPECIALLY GOOD AT FINDING NEWBORN CALVES.

HUNTING AROUND LIKE BIRD DOGS ON THE LANDSCAPE,

FINDING THEIR SCENT, CATCHING THEM AND EATING THEM,

AND THEY DO IT IN THE FIRST FEW WEEKS OF THE LIFE OF AN ELK CALF

BEFORE IT'S EVEN UP, RUNNING AROUND.

AND THAT'S HOW MOST ELK CALVES THAT DIE FROM PREDATION DIE.

Narrator: THIS CALF, KILLED EARLIER BY A GRIZZLY,

IS STILL GUARDED BY ITS MOTHER.

GRIZZLIES HAVE THE KEENEST SENSE OF SMELL

OF ALL YELLOWSTONE'S PREDATORS.

THEY CAN DETECT THE NEARLY SCENTLESS CALVES

THAT OTHER PREDATORS CANNOT.

[HOWLING]

THE COW ELK TRIES TO DISTRACT THE BEAR

AWAY FROM HER DEAD YOUNGSTER.

BUT SHE'S HELPLESS BEFORE THE MASSIVE GRIZZLY.

♪

[RAVEN SQUAWKING]

♪

[RAVEN SQUAWKING]

♪

BUT IF THE BEAR IS RESPONSIBLE

FOR THE ELK'S PLUMMETING NUMBERS,

THERE MUST BE SOMETHING ELSE AT PLAY HERE.

BEARS WERE AROUND HUNTING ELK CALVES

WHILE THE ELK HERDS WERE STILL ENORMOUS,

EVEN OUT OF CONTROL.

[RAVEN SQUAWKING]

IS SOMETHING TURNING YELLOWSTONE'S GRIZZLY BEARS

INTO ELK MASS MURDERERS?

WITH ELK POPULATION DECIMATED

AND THE GRIZZLIES NOW BECOMING THE LEAD SUSPECT,

IT'S TIME FOR SOME SERIOUS BEAR EXPERTISE.

FRANK VAN MANEN AND HIS COLLEAGUES

FROM THE INTERAGENCY GRIZZLY BEAR STUDY TEAM

KNOW THE BEARS OF YELLOWSTONE COUNTRY

BETTER THAN ANYONE ELSE.

Man: HELLO!

Frank van Manen: GRIZZLY BEARS ARE THE ICONIC SPECIES

IN THIS ECOSYSTEM.

IT'S AN ANIMAL THAT IS VERY POWERFUL.

YOU KNOW WHEN YOU'RE WALKING IN GRIZZLY BEAR COUNTRY

THAT YOU'RE NOT THE MOST POWERFUL CREATURE

IN THAT LANDSCAPE,

AND THAT'S A SENSE OF HUMILITY THAT I ALMOST ENJOY.

HEY, BEAR!

AND IF WE CAN FIND A WAY TO COEXIST WITH ANIMALS LIKE THAT,

I THINK WE'VE ACCOMPLISHED A LOT.

Narrator: THE SCIENTISTS NEVER ENTER GRIZZLY TERRITORY ALONE.

IN TEAMS, THEY SET OUT

TO CHECK ON THEIR SPECIALLY DEVELOPED BEAR TRAPS...

A LITTLE LOW-HANGING BARBED WIRE

SURROUNDING A COCKTAIL OF ANIMAL BLOOD.

THE BARBS SNAG BITS OF BEAR FUR FOR THEM TO ANALYZE,

AND CAMERAS WILL CATCH THEM IN THE ACT.

THE CAMERA TRAP SHOWS A FAMILY OF THREE

PASSING THROUGH JUST 24 HOURS AGO.

AND SURE ENOUGH, THEY'VE LEFT CRUCIAL HAIR SAMPLES

FOR DNA ANALYSIS.

THE RESEARCHERS HOPE TO IDENTIFY EACH AND EVERY BEAR

AND THEIR PREFERRED MENU.

Van Manen: WE CAN GET A LOT OF INFORMATION

FROM THESE, WHAT WE CALL HAIR TRAPS,

BECAUSE WE'RE COLLECTING DNA SAMPLES.

THAT'S BASICALLY LIKE GENETIC FINGERPRINTING.

WE CAN IDENTIFY THE INDIVIDUAL,

AND THERE'S SOME INCREDIBLY INTRIGUING PATTERNS

THAT COME OUT OF THAT.

Narrator: ONCE BEARS ARE IDENTIFIED,

THE SCIENTISTS CAN BEGIN TO FIGURE OUT

WHERE THE BEARS ARE GOING IN SEARCH OF FOOD...

BOTH INSIDE AND OUTSIDE THE PARK.

ANALYSIS OF THE ANIMALS' SCAT

TELLS THEM EXACTLY WHAT THE BEARS ARE EATING.

Van Manen: GRIZZLY BEARS ARE DISTRIBUTED

IN ABOUT 50,000 SQUARE KILOMETERS OF HABITAT,

AND IT IS LISTED AS A THREATENED POPULATION

UNDER THE U.S. ENDANGERED SPECIES ACT.

SO OUR TASK AS A STUDY TEAM

IS TO HELP SPECIES AND POPULATIONS RECOVER.

Narrator: BUT HAIR TRAPS ARE NOT ENOUGH.

TO REALLY FIGURE OUT WHAT'S GOING ON,

THEY NEED TO RECRUIT THE BEARS THEMSELVES AS INFORMANTS.

ONCE A BEAR IS TRAPPED AND SEDATED,

HE GETS A THOROUGH MEDICAL EXAM

BEFORE BEING FITTED WITH A GPS RADIO COLLAR.

AN EXPERIENCED VET FROM THE PARK MANAGEMENT

HELPS WITH MEASURING, WEIGHING AND BLOOD DRAWING.

SO FAR, THE GPS DATA HAS BEEN STARTLING.

Van Manen: WE HAVE SEEN MOVEMENTS

DURING THE MIDDLE OF THE DAY, BASED ON OUR GPS LOCATIONS,

OF TEN KILOMETERS OR MORE,

THROUGH A LOT OF AREAS WHERE THERE WAS A LOT OF HUMAN USE

AND NOBODY EVER REPORTED SEEING HIM,

NOBODY HAD ANY IDEA

THIS ANIMAL WAS CROSSING THIS LANDSCAPE

AMONG ROADS AND PEOPLE, BIKES AND CARS.

IT'S REALLY FASCINATING HOW THESE ANIMALS USE THE LANDSCAPE

AND BASICALLY GO UNDETECTED.

HEY-O!

Narrator: THE COLLARS CONFIRM

WHAT THE SCIENTISTS HAVE ALWAYS SUSPECTED.

BEARS ARE SMART ANIMALS THAT ARE HAPPY TO MAKE USE

OF HUMAN-CREATED SHORTCUTS.

THEY USE THE SWATHS CREATED FOR ELECTRICAL LINES

AS URSINE HIGHWAYS,

PERFECT FOR COVERING LONG DISTANCES WITHOUT BEING SEEN.

AND THEY USE THE TELEPHONE POLES AS SCRATCHING POSTS,

AS WELL AS LEAVING CHEMICAL MESSAGES ON THEM

FOR OTHER BEARS.

THERE WE GO.

[BEEP]

Narrator: THE FINDINGS ARE GREAT NEWS FOR BEARS.

Van Manen: FROM ALL OUR DEMOGRAPHIC ANALYSIS,

WE'VE SEEN THAT THIS POPULATION INCREASED

BY BETWEEN ABOUT 4 TO 7% ANNUALLY

FROM 1983 TO ROUGHLY ABOUT 2000.

AND WHAT WE'VE SEEN SINCE THEN

IS THAT THE POPULATION GROWTH HAS SLOWED DOWN A LITTLE BIT,

BUT THERE'S CERTAINLY NO INDICATION OF DECLINE.

SO WE ARE NOW LOOKING AT A POPULATION

IN MUCH BETTER SHAPE THAN THEY WERE IN THE 1970s.

Narrator: BUT IS GOOD NEWS FOR BEARS

THE CAUSE OF THE TERRIBLE NEWS FOR THE ELK?

WITH THEIR NUMBERS GROWING STEADILY IN THE LAST 30 YEARS,

COULD GRIZZLIES BE OUR KILLERS OF YOUNG ELK CALVES?

CLEARLY THE NUMBER OF MANY MORE GRIZZLIES

WOULD HAVE SOME IMPACT ON THE SURVIVAL OF THE ELK,

ESPECIALLY CALVES.

BUT THERE'S A PROBLEM.

THE MOST DRAMATIC DECLINE OF THE MIGRATING ELK HERD

HAS TAKEN PLACE IN THE LAST 10 YEARS...

AND DURING THAT TIME THE GRIZZLY POPULATION HAS HELD STEADY.

SO NOW IT'S EVEN HARDER TO PIN THE ELK MURDER MYSTERY

ON A SINGLE PREDATOR,

AND THE PROFILES OF OUR POTENTIAL SERIAL KILLERS

GET MURKIER.

[BIRD SQUAWKING]

[BEAR GROWLING]

IN A WOLF-BEAR STANDOFF OVER A CALF KILL,

THE BEAR IS ALMOST ALWAYS GOING TO WIN.

BUT THAT DOESN'T NECESSARILY TRANSLATE

INTO AN ELK-HEAVY, ALL-CARNIVORE DIET

FOR THE BEARS.

THE ANALYSIS OF THEIR HAIR AND SCAT SAMPLES SHOW OTHERWISE.

Van Manen: BASICALLY, WHAT WE FOUND OUT

WAS THAT IT WAS INCREDIBLY DIVERSE.

GRIZZLY BEARS CONSUMED 266 DIFFERENT SPECIES OF ORGANISMS.

PLANTS, A NUMBER OF DIFFERENT MAMMALS, FISH, INSECTS...

IT'S AN INCREDIBLE VARIETY OF SPECIES.

WE CALL THEM OPPORTUNISTIC OMNIVORES FOR A GOOD REASON.

Narrator: AFTER THE 3 TO 5 MONTHS OF HIBERNATION

THEY EVEN EAT DIRT... VOLCANIC SOIL...

TO JUMP-START THEIR DIGESTIVE SYSTEMS.

THE POTASSIUM AND MAGNESIUM

MAY HELP KILL OFF PARASITES THAT CAUSE DIARRHEA.

BUT THEY NEED HUGE AMOUNTS OF PROTEIN AND FAT AS WELL,

AND A SURPRISING AMOUNT OF THESE NUTRIENTS

COMES FROM THE TINIEST OF PREY IN THE STRANGEST OF PLACES.

DURING THE SUMMER MONTHS,

GRIZZLIES CLAMBER UP PAST 9,000 FEET

TO REACH PRECARIOUS SLOPES OF LOOSE ROCK,

OFTEN WITH YOUNG IN TOW.

THEY'RE LOOKING FOR LITTLE PACKETS OF FAT

HIDING FROM THE SUN AMONG THE ROCKS: MOTHS.

ARMY CUTWORM MOTHS...

COMMONLY KNOWN AS MILLER MOTHS.

IN YELLOWSTONE, THE MOTHS CAN MATE AND SPENT THE SUMMER

IN THE SHADE OF THE ROCKY MOUNTAINS.

DURING THEIR STAY THE MOTHS FATTEN UP

ON THE NECTAR OF THE RICH ALPINE MEADOWS...

AND HIDE ON THE SLOPES.

A SINGLE GRIZZLY BEAR CAN EAT OVER 40,000 MOTHS A DAY.

THAT'S ACTUALLY 20,000 CALORIES OF FAT!

HOWEVER, THE LOOSE ROCK CAN MAKE THIS AN UNNERVING FEAST...

♪

BUT GRIZZLIES CANNOT LIVE BY MOTHS ALONE.

Van Manen: WE SEE DIET DIFFERENCES BASED ON INDIVIDUALS.

EACH INDIVIDUAL IS SLIGHTLY DIFFERENT.

WE SEE DIFFERENCES BASED ON WHERE YOU ARE IN THE ECOSYSTEM.

WE SEE DIFFERENCES BASED ON TIME,

SO FROM ONE DAY TO THE NEXT

THEY COULD BE CONSUMING SOMETHING VERY DIFFERENT,

FROM ONE SEASON TO THE NEXT SEASON

AND EVEN FROM ONE YEAR TO THE NEXT YEAR.

Narrator: WITH SO MANY FOOD SOURCES TO CHOOSE FROM,

WHY WOULD GRIZZLIES BE TAKING MORE AND MORE ELK CALVES?

IS SOMETHING IMPORTANT ON THEIR MENU DISAPPEARING?

IN YELLOWSTONE'S WHITEBARK PINE FORESTS,

SQUIRRELS ARE BUSY PREPARING FOR THE LONG WINTER.

AND THE SMART BEARS KNOW IT.

WHILE SQUIRRELS FRENETICALLY COLLECT AND STORE

THE ENERGY-RICH SEEDS OF THE WHITEBARK PINES,

THE GRIZZLIES SIMPLY WAIT

AND THEN DIG UP THEIR BURROWS TO STEAL THE SEEDS.

♪

Van Manen: WHITEBARK PINE IS AN IMPORTANT FOOD SPECIES

FOR GRIZZLY BEARS.

THEY ACTUALLY FEED ON THE BIG SEEDS OF WHITEBARK PINE

THAT ARE VERY RICH IN PROTEINS AND FATS DURING THE FALL TIME,

SO IT'S ALSO A FOOD SOURCE THAT IS AVAILABLE

DURING AN IMPORTANT TIME OF YEAR FOR GRIZZLY BEARS,

BECAUSE THAT'S WHEN THEY PREPARE FOR HIBERNATION.

Narrator: BUT THE WHITEBARK PINE FORESTS ARE DYING.

72% OF THE BIG TREES ARE GONE,

MANY KILLED BY THE VORACIOUS MOUNTAIN PINE BEETLE,

WHICH IS THRIVING BECAUSE OF GLOBAL WARMING.

♪

BUT PINE NUTS ARE IMPORTANT TO THE BEARS ONLY IN THE FALL,

BEFORE HIBERNATION,

AND NOT IN THE SPRING,

WHEN THE ELK CALVES ARE DISAPPEARING.

STILL, THE DECLINE OF THE WHITEBARK PINE

DOES PROVIDE AN IMPORTANT CLUE IN THE PUZZLE:

IT SHOWS HOW GRIZZLIES REACT TO A VANISHING FOOD SOURCE.

Van Manen: WE WERE ABLE TO DEMONSTRATE

THAT THEY'RE NOT USING WHITEBARK PINE HABITATS

AS MUCH AS THEY USED TO.

SO WE HAVE SEEN A RESPONSE TO THAT,

BUT WE HAVEN'T SEEN THAT THEY INCREASED

THEIR HOME RANGES OR THEIR MOVEMENTS,

AND INSTEAD WHAT WE FOUND

WAS THAT THEY SEEM TO BE FINDING ALTERNATIVE FOOD SOURCES

WITHIN THEIR REGULAR HOME RANGES.

Narrator: THE UPSHOT... WHEN FACED WITH A FOOD CRISIS,

BEARS DO NOT CHANGE WHERE THEY EAT...

THEY CHANGE WHAT THEY EAT.

SO THE QUESTION BECOMES: HAS SOMETHING DISAPPEARED

FROM THE BEARS' SPRING AND SUMMER MENU

THAT'S MAKING THEM TURN ELSEWHERE FOR FOOD,

ESPECIALLY AMONG THE BEARS THAT ENCOUNTER THE ELK HERDS

JUST AS THE ELK ARE GIVING BIRTH?

THE ANSWER: A STUNNING YES.

IN THE HAIR SAMPLES,

VAN MANEN FINDS A HUGE CLUE TO THE ELK MYSTERY.

THEY SHOW THAT BEARS AROUND YELLOWSTONE LAKE

AREN'T EATING THE FISH THAT USED TO DOMINATE THESE WATERS

AND THEIR SPRING DIETS.

Van Manen: FOR THOSE BEARS NEAR YELLOWSTONE LAKE,

CUTTHROAT TROUT WERE CERTAINLY A PORTION OF THE DIET.

AND NO DOUBT THAT THAT USE DECLINED SUBSTANTIALLY.

Narrator: IN THE LAST DECADE, IT HAS BECOME CLEAR

THAT SOMETHING HAS GONE TERRIBLY WRONG

IN YELLOWSTONE LAKE.

ROBERT GRESSWELL OF THE U.S. GEOLOGICAL SURVEY

KNOWS THE FISH OF YELLOWSTONE BETTER THAN ANYONE.

AND HE'S BEEN WITNESS TO A TRUE ECOLOGICAL CALAMITY...

THE DISAPPEARANCE OF THE NATIVE CUTTHROAT TROUT.

Robert Gresswell: IN THE 1960s THERE WERE THOUSANDS OF PEOPLE

THAT WOULD SHOW UP TO FISH ON FISHING BRIDGE.

AND IT WAS DANGEROUS.

I REMEMBER IN 1969, WHEN I WORKED HERE,

YOU DIDN'T DRIVE ACROSS THE BRIDGE WITH YOUR WINDOW DOWN,

BECAUSE YOU MIGHT GET HOOKED BY SOMEBODY CASTING.

Narrator: FISHING IS NOW FORBIDDEN AT FISHING BRIDGE...

BUT EVEN IF IT WEREN'T

IT WOULD BE A MIRACLE TO CATCH A CUTTHROAT TROUT.

ISOLATED FROM OTHER CUTTHROAT

WHEN THE LAST ICE AGE CREATED THE IMPASSABLE LOWER FALLS,

YELLOWSTONE'S CUTTHROAT BECAME GENETICALLY DISTINCT

AND THE FOUNDATION OF A THRIVING ECOSYSTEM.

FOR MILLENNIA, MILLIONS OF YELLOWSTONE CUTTHROAT

HAVE MIGRATED UP THE LAKE TRIBUTARIES

TO SPAWN IN LATE SPRING.

AS MEMBERS OF THE SALMON FAMILY,

THEY LIVE AND REPRODUCE IN SHALLOW WATERS,

WHICH MAKE THEM EASY TARGETS NOT ONLY FOR HUNGRY BEARS.

Gresswell: THE YELLOWSTONE CUTTHROAT TROUT

HAS A HUGE ROLE IN THIS ECOSYSTEM

AS A KEYSTONE SPECIES,

AS A KEYSTONE PART OF THE FOOD WEB.

THERE ARE NUMEROUS, IN ONE ESTIMATE 42 ANIMALS,

THAT AT SOME POINT IN THEIR LIFE

MAY FEED ON YELLOWSTONE CUTTHROAT TROUT.

Narrator: SPAWNING TIME IS IN LATE MAY AND EARLY JUNE...

PERFECT FOR THE FAMISHED GRIZZLIES

EMERGING FROM HIBERNATION TO GET SOME PROTEIN.

♪

♪

BUT SOMETHING SIGNIFICANT MUST HAVE CHANGED IN THE LAST YEARS.

BEARS AREN'T EATING

ANYWHERE NEAR THE NUMBER OF FISH THEY USED TO.

WILDLIFE BIOLOGIST TODD KOEL FROM THE NATIONAL PARK SERVICE

HAS BEEN MONITORING THE NATIVE CUTTHROAT TROUT FOR YEARS.

HE TAKES ONE OF HIS SONS WITH HIM

TO VISIT A SPAWNING GROUND NAMED CLEAR CREEK,

WHERE HE'S INSTALLED A COUNTING STATION.

THE CHANGES ARE SIMPLY DEVASTATING.

Todd Koel: A DECADE AGO WHEN I ARRIVED

TO THESE SPAWNING STREAMS HERE AROUND YELLOWSTONE LAKE,

WE WOULD STILL SEE THOUSANDS OF CUTTHROAT TROUT

MIGRATING UP THEM IN THE SPRING TO SPAWN.

AT THAT TIME, YOU'D SEE OSPREYS FLYING BY

WITH CUTTHROAT TROUT IN THEIR TALONS.

IT WAS COMMON, ALL THE TIME.

BUT EACH YEAR WHEN WE WOULD RETURN AND MONITOR THE FISH,

WE WOULD SEE LESS AND LESS AND LESS.

AND SO, DESPITE SPENDING A LOT OF TIME OUT HERE,

I HAVEN'T SEEN AN OSPREY ON YELLOWSTONE LAKE NOW

IN SEVERAL YEARS.

Narrator: THE NUMBERS CONFIRM THE AWFUL TRUTH.

JUST 20 YEARS AGO,

THERE WERE 50,000 CUTTHROAT PASSING THROUGH CLEAR CREEK.

IN 2014, THERE WERE ONLY ABOUT 100 INDIVIDUALS.

AND ROBERT GRESSWELL SAW IT COMING.

Gresswell: IN 1994 ONE OF THE RANGERS CAME UP,

AND HE HAD A LAKE TROUT IN HIS HANDS,

AND HE SAID, "THIS LAKE TROUT WAS JUST BROUGHT TO ME

BY SOME ANGLERS IN YELLOWSTONE LAKE,"

AND I FELT LIKE SOMEBODY HAD JUST PUNCHED ME IN THE STOMACH.

Koel: LAKE TROUT ARE NON-NATIVE TO YELLOWSTONE LAKE,

AND THEY'RE A VERY PREDATORY SPECIES.

THEY'RE SORT OF LIKE WOLVES ON THE LANDSCAPE,

BUT IN A PLACE IN THE WATER

WHERE THEY'RE NOT SUPPOSED TO BE.

Narrator: THE INVADING AMERICAN LAKE TROUT IS HUGE,

MUCH BIGGER THAN THE NATIVE CUTTHROAT,

AND INSATIABLE.

A SINGLE LAKE TROUT CAN EAT MORE THAN 40 CUTTHROAT A YEAR.

AND NOW THEY'VE BROUGHT THE YELLOWSTONE CUTTHROAT

TO THE BRINK OF EXTINCTION.

Koel: IN OTHER LAKES WHERE LAKE TROUT HAVE BEEN INTRODUCED,

THE NATIVE SPECIES CAN BE EXTIRPATED COMPLETELY...

BECOME EXTINCT...

AND SO WHEN THE LAKE TROUT WERE FIRST DISCOVERED HERE

TWO DECADES AGO,

THAT CAUSED HUGE ALARM

BECAUSE OF WHAT WE'VE SEEN HAPPEN AROUND US ALREADY

IN THESE OTHER PLACES.

Narrator: BUT HOW DOES THIS FIT INTO THE MYSTERY?

WHY WOULDN'T BEARS SIMPLY SWITCH FROM ONE TROUT TO ANOTHER?

THE ANSWER, AND THE FINAL CLUE IN OUR MURDER MYSTERY,

WAS WITHIN THE SCIENTISTS' GRASP.

THE TRAIL OF THE ELK KILLERS

HAS LED THE PARK MANAGEMENT

DEEP UNDER THE SURFACE OF YELLOWSTONE LAKE.

THE INVASIVE TROUT LIVE AND REPRODUCE DEEP IN THE LAKE

AND NEVER MIGRATE TO SHALLOW WATERS.

SO BALD EAGLES, OSPREYS, AND BEARS CAN'T GET TO THEM.

BUT IT HAS PROVIDED A VITAL CLUE IN THE ELK MURDER MYSTERY:

IF GRIZZLIES, EMERGING FROM HIBERNATION IN THE SPRING,

FIND THAT THEIR EASIEST AND RICHEST SOURCE

OF FAT AND PROTEIN HAS DISAPPEARED,

WHAT DO THEY DO?

THEY WON'T MIGRATE IN SEARCH OF OTHER FISH.

THE BIOLOGISTS' STUDIES HAVE SHOWN THAT.

INSTEAD THEY'LL STAND THEIR GROUND, ADAPT,

AND FIND ANOTHER RICH FOOD SOURCE ON LAND.

[WOLF HOWLING]

AND WHAT IS HAPPENING AROUND YELLOWSTONE LAKE IN LATE SPRING,

WHEN THE FISH FAIL TO APPEAR?

THE MIGRATORY ELK HERDS HAVE RETURNED

TO THE LUSH HIGH MEADOWS TO GIVE BIRTH.

AND THE GRIZZLIES,

FAR MORE ADEPT AT HUNTING ELK CALVES

THAN WOLVES OR ANY OTHER PREDATOR,

HAVE HAD NO CHOICE BUT TO UP THE ANTE ON THE NEWBORNS...

AND THE ELK POPULATION CRASHED.

♪

♪

♪

AND SO IT APPEARS THAT THE LOWLY LAKE TROUT,

NOT THE GREAT BEARS AND WOLVES, ARE OUR SERIAL KILLERS.

THE PARK MANAGEMENT

HAS BEEN REMOVING THE INVASIVE KILLERS EVER SINCE.

LARGE GILL NETS,

ADJUSTED TO THE SIZE AND BEHAVIOR OF THE LAKE TROUT,

ARE DEPLOYED DEEP IN THE WATER.

THE LARGE MESH SIZES

LET THE SMALLER CUTTHROAT TROUT PASS THROUGH UNHARMED.

♪

EACH YEAR TENS OF THOUSANDS OF LAKE TROUT

HAVE BEEN REMOVED FROM YELLOWSTONE LAKE,

BUT THE CUTTHROAT NUMBERS STILL COLLAPSED.

IN 2007, A SCIENCE PANEL CONVENED,

HOPING TO AVERT DISASTER.

Gresswell: THE PANEL UNANIMOUSLY SUPPORTED THE CONTINUATION OF THE PROGRAM

AND IN FACT RECOMMENDED

THAT THE PARK SERVICE INCREASE THE GILL-NETTING EFFORT.

Koel: WE BEGAN GETTING BIGGER BOATS,

MORE NETS, LARGER CREWS.

IT'S REALLY TURNED INTO QUITE A MASSIVE EFFORT,

AN AGGRESSIVE EFFORT, ACTUALLY, TO BATTLE THESE LAKE TROUT.

♪

Narrator: THE SCIENTISTS NEEDED TO FIND OUT

WHERE THE LAKE TROUT WERE COMING FROM.

SO, THEY SAMPLED THE EAR BONES

FROM THE OLDEST AND BIGGEST OF THE LAKE TROUT.

UNDER THE MICROSCOPE,

THE EAR BONES SHOW GROWTH RINGS, LIKE TREES...

SHOWING HOW OLD THE INVADERS WERE

AND WHERE THEY CAME FROM.

Gresswell: WHAT THEY FOUND

WAS THAT THE CHEMICAL SIGNATURE ACTUALLY CHANGED,

AND THE OLDEST PART WAS SIMILAR TO LEWIS LAKE,

SO THESE FISH WERE ACTUALLY BORN

AND LIVED THEIR EARLY LIFE IN LEWIS LAKE,

AND THEN APPARENTLY WERE MOVED AT SOME POINT IN TIME

INTO YELLOWSTONE LAKE.

Narrator: BECAUSE NO RIVERS CONNECT YELLOWSTONE LAKE

TO LEWIS LAKE,

THE INVASIVE TROUT COULDN'T HAVE GOTTEN THERE ON THEIR OWN.

THE CHEMICAL SIGNATURE SHOWED THAT THEY'D BEEN DUMPED THERE

SOMETIME IN THE MID-1980s.

[THUNDER]

NO ONE KNOWS WHO DUMPED THE FISH IN THE LAKE OR WHY.

IT MAY HAVE BEEN SPORT FISHERMEN,

LOOKING FOR BIGGER FISH TO FRY.

IRONICALLY, THOUGH, THE GUILT REACHES FURTHER BACK...

TO WHEN THE U.S. FISH COMMISSION

FIRST BROUGHT LAKE TROUT INTO LEWIS LAKE

MORE THAN A CENTURY AGO.

Koel: THE FISH COMMISSION SAW IT

AS AN OPPORTUNITY TO BEGIN STOCKING.

AT THE TIME THEY CALLED IT

PLANTING OF FISHES IN THESE FISHLESS WATERS.

AND THIS WAY IS HOW LAKE TROUT WERE INTRODUCED

TO YELLOWSTONE NATIONAL PARK.

Narrator: SO FAR, MORE THAN ONE MILLION

OF THE INVADING TROUT HAVE BEEN NETTED AND KILLED.

FOR DECADES IT HAS SEEMED A LOSING BATTLE...

AND THE CUTTHROAT WERE DECIMATED.

WITH TIME RUNNING OUT, AND THE WHOLE ECOSYSTEM AT RISK,

THE BIOLOGISTS NEEDED A MORE AUDACIOUS PLAN.

SO GRESSWELL AND HIS TEAM TAG LAKE TROUT WITH GPS TRANSMITTERS

AND FOLLOW THEM TO THEIR SPAWNING GROUNDS.

Gresswell: AS WE IDENTIFY WHERE THESE LAKE TROUT ARE SPAWNING

IN YELLOWSTONE LAKE,

THEN WE CAN FOCUS ON THOSE SPAWNERS

DURING THAT PERIOD OF TIME.

Narrator: AFTER ONE YEAR OF TRACKING,

THE RESEARCHERS FINALLY HONE IN ON A MAJOR SPAWNING GROUND

IN THE WATERS OFF CARRINGTON ISLAND.

AND A SPECIALLY DEVELOPED DIVING ROBOT IS SENT IN

TO DRIVE THE YOUNG FISH INTO THE OPEN WATER

USING MILD ELECTRO SHOCKS.

MILLIONS OF NEARLY INVISIBLE HATCHLINGS, WHEN GROWN,

WILL EAT EVERYTHING IN SIGHT,

AND THERE IS NO NATURAL PREDATOR HERE THAT EATS THEM.

Man: STOP.

Gresswell: THIS IS ALL REALLY IMPORTANT RESEARCH,

BECAUSE ALL THE INFORMATION WE HAVE NOW

COMES FROM THE GREAT LAKES,

AND THERE THERE ARE MANY MORE EGG AND LARVAL FISH PREDATORS

IN THE SYSTEM.

AND EVERY INDICATION WE HAVE IS THAT ONE OF THE REASONS

WHY WE UNDERESTIMATED SO GREATLY

THE POTENTIAL FOR THE LAKE TROUT TO AFFECT THE CUTTHROAT TROUT

IS THAT WE JUST HAD NO IDEA

HOW FAST THAT POPULATION WOULD EXPAND

BECAUSE SURVIVAL OF YOUNG

SEEMS TO BE MUCH, MUCH HIGHER IN YELLOWSTONE LAKE

BECAUSE THERE ARE NO OTHER PREDATORS.

Narrator: NOW THAT THEY'VE FOUND THE SPAWNING GROUND,

IT'S TIME TO BRING IN THE HEAVY ARTILLERY:

ELECTRIC PULSES KILL THE FRY,

BEFORE THEY GROW LARGE ENOUGH TO EAT THEIR WAY THROUGH

TO THEIR NATIVE CUTTHROAT COUSINS.

♪

AND NOW, FOR THE FIRST TIME,

THERE MAY BE REAL REASON FOR HOPE ON THE HORIZON.

SLOWLY, THE INVASIVE LAKE TROUT NUMBERS ARE FALLING.

[OSPREY CHIRPING]

♪

AND THIS YEAR, ELK NUMBERS ARE UP SIGNIFICANTLY...

STILL NOWHERE NEAR THE POPULATIONS OF 20 YEARS AGO,

BUT THE HERD IS GROWING.

IT'S TOO EARLY TO SAY IF THE CONNECTION

LEADS DIRECTLY FROM THE FISH TO THE BEARS TO THE ELK MURDERS.

BUT ONE THING IS SURE:

NO SINGLE PREDATOR IS MORE GUILTY IN THIS CURIOUS CASE

THAN HUMANS.

♪

AND PERHAPS, WITH A LITTLE BIT OF HELP,

THE ANCIENT WISDOM OF YELLOWSTONE

IS ALREADY TURNING THE TIDE AGAINST OUR SHORT-SIGHTEDNESS...

AND THE WORLD'S FIRST NATIONAL PARK

WILL RETURN TO ITS PRIMAL RHYTHMS ONCE AGAIN.

♪

♪

♪

♪