>> male narrator: THERE'S SOMETHING LURKING IN THE WATER. >> IT'S A CLEAR DANGER TO US. >> narrator: AND IT KILLS WITH LIGHTNING SPEED. >> THEY HAVE THE RIGHT EQUIPMENT TO DO DAMAGE >> narrator: THE BEAST TEARS THROUGH FLESH AND BONE. >> YEAH, IT WAS THE SCARIEST-LOOKING FISH I'D EVER SEEN. >> narrator: THIS CREATURE HAS TERRIFIED MAN FOR CENTURIES. >> THEY WILL READILY TAKE OVER AN AREA AND BECOME THE DOMINANT SPECIES. >> narrator: NOW THE DEADLY BEAST HAS SET ITS SIGHTS ON AMERICA. >> TOPSIDE, TOPSIDE, GOT A PROBLEM. >> narrator:<i> MONSTER QUEST</i> IS INVESTIGATING PIRANHAS IN AMERICA. >> AH, [bleep]. >> narrator: PEOPLE AROUND THE WORLD REPORT SEEING MONSTERS. ARE THEY REAL OR IMAGINARY? SCIENCE SEARCHES FOR ANSWERS ON<i> MONSTER QUEST.</i> Captioning by<font color="#00FF00"> CaptionMax</font> www.captionmax.com THE SOUTHEAST IS HOME TO THOUSANDS OF LAKES. THESE BEAUTIFUL OASES ARE SUMMER RETREATS FOR FAMILIES WHO COME TO RELAX AND COOL OFF. BUT SOMETHING DEADLY MAY BE LURKING BENEATH THE PLACID WATERS. >> VERY SHARP TEETH, TRIANGLE--TRIANGLE, VERY--RAZOR-SHARP TEETH. >> THEY ARE SOMEWHAT LIKE THE VULTURES OF THE FRESHWATER. >> I DIDN'T KNOW WHAT IT WAS, DIDN'T KNOW EXACTLY WHAT WE'D CAUGHT. >> narrator: EYEWITNESSES REPORT SEEING SWARMS OF VICIOUS PIRANHAS WITH ROWS OF RAZOR-SHARP TEETH. THESE BEASTS OFTEN ATTACK WITHOUT PROVOCATION AND CAN TEAR APART FLESH. THE CARNIVOROUS BEASTS LIVE IN FRESHWATER RIVERS AND LAKES. >> YEAH, ABSOLUTELY, I WAS SHOCKED. >> narrator: ALLEN CARLSON AND HIS BUDDIES WERE HEADED TOWARD A LOCAL RESERVOIR. THE SPOT WAS ALSO A POPULAR PLACE FOR FAMILIES TO SWIM AND FISH. >> IT WAS LABOR DAY WEEKEND. WE WERE FISHING WITH NIGHT CRAWLERS, BOTTOM FISHING FOR CATFISH. AND THEN THE PIRANHA STRUCK. WELL, WHEN IT HIT THE LINE, IT JUST TOOK OFF, AND THE SENSATION WAS OF A BLUEGILL. I THOUGHT IT WAS A BIG BLUEGILL, AND MY BUDDY SAID IT MIGHT BE A RECORD BLUEGILL, THE WAY IT WAS BENDING MY POLE OVER. AND WE FOUGHT ITOR--I FOUGHT IT FOR A FEW MINUTES AND GOT IT IN, AND WHEN I WENT TO LIFT IT UP, WE WAS LOOKING DOWN IN ITS MOUTH, AND WE SEEN ALL THE TEETH. LOOKING DOWN IN ITS MOUTH, YEAH, IT WAS SCARIEST-LOOKING FISH I'D EVER SEEN. I DIDN'T KNOW WHAT IT WAS, DIDN'T KNOW EXACTLY WHAT WE'D CAUGHT. >> narrator: CARLSON SHOWED THE FISH TO A TENNESSEE WILDLIFE OFFICIAL, WHO CONFIRMED IT WAS A PIRANHA. WORD SPREAD QUICKLY. >> THE DAY I CAUGHT THE PIRANHA, THERE WAS LITTLE KIDS OUT THERE ON A BOAT, SWIMMING. NEIGHBORS AROUND THERE ALL CAME OUT TO SEE WHAT WAS GOING ON, AND THE YOUNG KIDS, THEIR PARENTS SAID, THEY DIDN'T KNOW IF THEY'D LET THEM SWIM IN THERE AGAIN FOR FEAR OF THEM BEING BIT BY THE PIRANHA. >> narrator: CARLSON BELIEVES THE FISH MAY BE BREEDING AND SPREADING ACROSS THE COUNTRY. >> PEOPLE THINK THAT THEY MAY BE ADAPTED AND BREEDING IN THESE LAKES. >> narrator: PIRANHAS ARE NATIVE TO SOUTH AMERICAN COUNTRIES LIKE BRAZIL AND VENEZUELA, PLACES WHERE WARM WATER TEMPERATURES ARE NORMAL. THEY ARE NOT KNOWN TO EXIST IN THE U.S. EXCEPT AS PETS. BUT SUDDENLY, REPORTS OF SIGHTINGS ARE EMERGING FROM AROUND THE COUNTRY. SOME QUESTION THEIR LEGITIMACY. >> IF SOMEONE HAD A FEW PIRANHAS IN THEIR AQUARIUM, AND THEY RELEASED THEM INTO A NEARBY LAKE OR POND THAT HAD-- SAY, DURING THE SUMMER WHEN THE WATER TEMPERATURES WERE WARM, THE PIRANHAS WOULD SURVIVE THE SUMMER. WHETHER OR NOT THEY WOULD REPRODUCE IS LESS LIKELY. FISHERMEN ARE PROBABLY DOING A FAIRLY GOOD JOB OF REMOVING MOST OR ALL OF PIRANHAS THAT ARE THERE. I SUSPECT THAT THE PIRANHAS THAT HAVE BEEN RELEASED ARE HUNGRY. THEY'VE BEEN RAISED IN AQUARIA, AND THEY'RE PROBABLY FAIRLY EASY TO TAKE WITH A HOOK AND LINE. MOREOVER, IT'S UNLIKELY, ESPECIALLY IN A PLACE LIKE LAKE OF THE OZARKS, THAT ANY OF THE PIRANHAS WOULD SURVIVE THE WINTER. >> narrator: THE MOST NOTORIOUS LOCATION FOR PIRANHAS IN AMERICA IS HERE AT LAKE OF THE OZARKS NEAR JEFFERSON CITY, MISSOURI. LOCALS HAVE CAUGHT A NUMBER OF PIRANHAS HERE OVER THE LAST FEW YEARS, AND CONSERVATION OFFICIALS CONFIRM THAT THE FISH HAVE BEEN FOUND IN THESE WATERS. >> IF YOU CATCH A PIRANHA EVERY YEAR FOR THREE YEARS, EVENTUALLY YOU NEED TO START CONSIDERING THE POSSIBILITY THAT THERE COULD BE SOMETHING HERE. >> narrator:<i> MONSTER QUEST</i> IS HERE TO INVESTIGATE THE SIGHTINGS AND SEE IF PIRANHAS ARE CAPABLE OF SURVIVING IN THESE COLD CLIMATE LAKES. >> WHAT WE'RE TRYING TO FIGURE OUT WHILE WE'RE HERE IS, WILL LAKE OF THE OZARKS' HABITAT SUPPORT A BREEDING POPULATION OF PIRANHA? >> narrator: DALE PEARSON, A PROFESSIONAL DIVER, WILL LEAD THE EXPEDITION. >> I THINK THE CHANCES THAT THERE'S A BREEDING POPULATION IN THE LAKE ARE ACTUALLY GREATER THAN THE CHANCES OF SOMEONE CATCHING ONE STRAY PIRANHA ON 500 MILES OF COASTLINE. >> narrator: PEARSON HAS ENLISTED LOCAL FISHING GUIDE JACK UXA TO ASSIST HIM. >> WE'RE DOWN HERE TRYING TO FIND EVIDENCE OF PIRANHA HABITAT. >> I KNOW THERE WAS ONE CAUGHT AT THE 5-MILE MARKER. THERE'S SOME CONSERVATION GUYS THAT ARE WORKING UP THE GRAND GLAIZE WITH SOME TRAP NETS FOR FISH. WE'D HAVE TO GO CHECK OUT UP THERE. IT'S A SPRING AREA WITH CONSISTENT WATER TEMPERATURE. >> WE KNOW PIRANHA EXIST. WE KNOW THEY'VE CAUGHT THEM IN THE LAKE. SO NOW IT'S MORE A MATTER OF FINDING THE PIECES OF THE EVIDENCE TO SUPPORT THAT THIS THING CAN LIVE HERE YEAR-ROUND. >> narrator: THE TEAM WILL SUBMERGE A BAITED UNDERWATER SURVEILLANCE SYSTEM IN THE LAKE. THEY WILL ALSO SEARCH FOR WARM WATER INLETS WHERE THE PIRANHAS COULD SURVIVE THE COLD WINTER MONTHS WHEN THE WATER TEMPERATURES DIP INTO THE 30s. AND<i> MONSTER QUEST</i> WILL WORK WITH STATE CONSERVATION CREWS TO SEE IF FISH TRAPS UNCOVER ANY SIGNS OF THE FLESH-EATERS. >> YOU GUYS READY? >> narrator: THE TEAM SETS OUT IN SEARCH OF A LOCATION TO DEPLOY THE SURVEILLANCE EQUIPMENT. >> THE PLAN IS, WE'RE GOING TO GO TO AN AREA WHERE THE DEPARTMENT OF FISH AND GAME DOES TRAP NETTING FOR CRAPPIE. AND IF THERE'S A CHANCE THAT WE'RE GONNA FIND A PIRANHA IN THE LAKE, THAT'S PROBABLY A REALLY GOOD AREA WHERE WE'RE GONNA FIND IT. SO WE'RE GONNA GO THERE, SET UP THE CAMERA TRAP SYSTEM AND SOME BAIT, LEAVE IT THERE OVERNIGHT, AND SEE IF WE CAN BRING SOMETHING IN. THE FACT THAT THEY'VE CAUGHT PIRANHA HERE EVERY YEAR FOR THREE YEARS, SOMETHING THIS BIG TELLS ME THAT IT'S PROBABLY NOT JUST A PET THAT'S LOOSE. >> WHERE WE'RE GOING, IT'S A CLEARER SECTION OF THE LAKE. >> THAT'LL BE GOOD. THAT WAY, WE CAN SET UP THAT CAMERA TRAP AND GET THE BAIT DOWN THERE AND GIVE IT 24 HOURS. COME BACK TOMORROW, YANK IT OUT, SEE WT WE GET. >> narrator: THEY FIND A SPOT ABOUT 50 FEET FROM SHORE... >> WE'RE GOOD. >> narrator: NEAR WHERE A FRESHWATER STREAM FEEDS INTO THE LAKE. >> NO, YOU KNOW WHAT? WE GOT ABOUT 3 FOOT RIGHT HERE, 3 FOOT OF VIS. >> WELL, I'M GONNA TAKE-- TAKE THIS CHICKEN, STICK THIS ROPE THROUGH THE CHICKEN, AND THEN I'M GOING TO TIE IT TO A--BASICALLY JUST A MARKER BUOY, SO WE KNOW EXACTLY WHERE IT IS. >> WE'RE USING A DEAD CHICKEN, BECAUSE PIRANHAS LIKE DEAD STUFF. THEY LIKE TO EAT DEAD STUFF AND OBVIOUSLY, SMALL, LIVE STUFF, BUT YOU KNOW, A DEAD ANIMAL IN THE WATER IS ALWAYS GONNA BRING WHATEVER IS AROUND, ESPECIALLY, LIKE, A NICE GREASY CHICKEN GIVING OFF THE SCENT AND STUFF LIKE THAT. >> A LOT OF FLESH. >> YEAH. AND HE'S GOT US RIGHT HERE BY A STREAM COMING IN, SO THE CURRENT'S GONNA COME THROUGH AND KIND OF PUSH THAT--PUSH THAT SCENT OUT HERE INTO THE MAIN PART OF THE LAKE, SO THAT'S THE THEORY, THAT WHATEVER'S OUT HERE IS GONNA COME IN AND CHECK OUT WHAT WE GOT. THAT'S WHEN WE TAKE THE PICTURE. >> OH, I THINK THIS IS GONNA WORK OUT GOOD. >> I THINK IF THERE'S SOMETHING IN THIS LAKE, IT'S GONNA BE CHEWING ON CHICKEN TONIGHT. >> WE'RE GONNA HAVE IT ANCHORED, AND WE'RE GONNA HAVE IT RIGHT IN FRONT OF THE CAMERA. >> narrator: THE TEAM PREPARES THE CAMERA. >> THIS IS A HARBORTRONICS AQUAPIC 360. AND IT'S BASICALLY AN UNDERWATER SURVEILLANCE CAMERA THAT YOU CAN LEAVE IN ONE AREA FOR EXTENDED PERIODS OF TIME, AND IT SHOOTS A 360-DEGREE--MULTIPLE IMAGES. SO THAT WAY, WHATEVER COMES AROUND YOUR CAMERA FROM ANY DIRECTION, YOU HAVE A WAY BETTER CHANCE OF GETTING A SHOT OF IT. YOU JUST FLICK IT ON HERE. NOW IT TAKES A SHOT. [camera whirs] TURNS. SO EVERY MINUTE, WE'RE TAKING A 360-DEGREE SHOT AROUND OUR BAIT, SO HOPEFULLY, WHATEVER COMES UP, WE'LL BE ABLE TO SEE IT. [buckles clicking] >> narrator: PEARSON GEARS UP TO DIVE INTO THE MURKY LAKE. VISIBILITY IS EXTREMELY LIMITED. >> GOT IT. >> YOU GOT IT? >> WHAT WE NEED TO FIND OUT IS HOW MANY OF THEM ARE HERE AND/OR IF THE HABITAT'S STRONG ENOUGH TO SUPPORT A WHOLE POPULATION OF THESE THINGS. THAT'S THE WHOLE REASON FOR THE DIVES. OKAY, ROGER THAT. WE'RE GONNA GO TO THE BOTTOM NOW. I'LL CONTACT YOU WHEN I HIT THE BOTTOM. [radio crackles] >> COPY. WE GOT A LOT OF SWIMMERS, A LOT OF PEOPLE THAT USE THE LAKE. BUT VERY RARELY DO WE EVER SEE SCUBA DIVERS HERE. WHAT KIND OF VISIBILITY DO YOU HAVE? [radio crackles] >> TOPSIDE, VISIBILITY IS APPROXIMATELY 2 FEET TO 3 FEET. BOTTOM IS A THICK, SILTY MUD IN THE MIDDLE OF THE CHANNEL LEADING UP TO A HARD, ROCKY BOTTOM ON THE OUTSIDES. THERE'S SOME SUBMERGED BRUSH DOWN HERE, AND ACTUALLY, THERE'S A LOT OF FISH. THERE'S FISH COMING UP TO ME ALREADY. OVER. >> narrator: SUDDENLY, SOMETHING STRIKES PEARSON'S LEG. >> TOPSIDE, TOPSIDE, GOT A PROBLEM. OVER. FRICKIN' ELECTRICAL WIRE. THERE'S ELECTRICAL WIRE DOWN HERE. AH, [bleep], THERE'S MORE OF IT. >> narrator:<i> MONSTER QUEST</i> HAS TRAVELED TO MISSOURI'S LAKE OF THE OZARKS, SEARCHING FOR EVIDENCE THAT FLESH-EATING PIRANHAS HAVE INVADED AMERICAN WATERS. NATIVE TO SOUTH AMERICA, PIRANHAS ARE AN ANCIENT SPECIES THAT HAVE BEEN AROUND FOR MORE THAN 8 MILLION YEARS. >> NOT A LOT IS KNOWN ABOUT MANY OF THE SOUTH AMERICAN FISHES. THEY'RE--THE FOSSIL EVIDENCE OF THE FRESHWATER FISHES IS FAIRLY POOR. THERE HAVE BEEN DISCOVERIES IN RECENT YEARS OF BITS OF PIECES OF JAWBONES OF DIFFERENT PIRANHA SPECIES, SOME SUCH AS THIS MEGAPIRANHA. >> narrator: THE MODERN PIRANHA IS THOUGHT TO HAVE EVOLVED FROM THE MEGAPIRANHA PARANENSIS, WHICH WENT EXTINCT 10 MILLION YEARS AGO. THIS PREHISTORIC BEAST DEVELOPED A DISTINCTIVE ROW OF FLESH-SHREDDING TEETH NEARLY AN INCH IN LENGTH. SCIENTISTS BELIEVE THIS EVOLUTION MAY HAVE OCCURRED WHEN FOOD SOURCES BECAME SCARCE. FOUR TIMES AS LARGE AS MODERN PIRANHAS, THESE ANCIENT BEASTS WERE BIG ENOUGH TO KILL AND DEVOUR OTHER ANIMALS ON THEIR OWN INSTEAD OF WORKING AS A GROUP. THE MODERN-DAY PIRANHA WAS UNKNOWN TO MANY AMERICANS UNTIL 1914. >> TEDDY ROOSEVELT, WHEN HE TRAVELED TO BRAZIL ON A EXPEDITION WITH HIS SON, ALSO WROTE ABOUT PIRANHAS. >> narrator: PRESIDENT ROOSEVELT, A WILDLIFE ENTHUSIAST, WROTE REPEATEDLY OF THE WONDROUS NEW SPECIES HE SAW ALONG THE WAY. WHEN HE WITNESSED A COW CARCASS THROWN INTO PIRANHA-INFESTED WATERS, HE MARVELED AT THE WAY IT WAS RIPPED TO SHREDS AND REDUCED TO A SKELETON. MANY AMERICANS LEARNED OF THE FISH FOR THE FIRST TIME BY READING THE PRESIDENT'S IMPRESSIONS IN HIS 1914 ACCOUNT <i>THROUGH THE BRAZILIAN</i> <i>WILDERNESS.</i> THE PRESIDENT DESCRIBED THE FEROCIOUS COORDINATED ATTACKS, REPORTING THAT NO ONE IN HIS GROUP DARED GET TOO CLOSE TO THE PIRANHA-INFESTED WATERS. >> TEDDY ROOSEVELT THOUGHT THAT PIRANHAS WERE ONE OF THE MOST, IN HIS OPINION, FEROCIOUS FISHES. >> narrator: ROOSEVELT HELPED CEMENT THE PIRANHA'S REPUTATION AS A MAN-EATER. HE WROTE THAT IT WOULD SNAP OFF A FINGER THAT SKIMMED THE WATER FROM A BOAT, MUTILATE SWIMMERS, OR DEVOUR ANY INJURED MAN WHO DARED ENTER THE WATER. THE HIGHLY PUBLICIZED TRIP DREW OTHER AMERICAN EXPLORERS TO THE AMAZON. THEY CONFIRMED THE PIRANHAS' APPETITE FOR FLESH, AS EVIDENCED BY THIS PHOTO TAKEN IN THE 1930s NEAR MATO GROSSO, BRAZIL. IT SHOWS A PIRANHA VICTIM WITH THE FLESH STRIPPED FROM HIS BODY. THE PIRANHAS' REPUTATION WOULD BE EXPLOITED FOR THE NEXT CENTURY IN POPULAR CULTURE. SOME FISHERMEN FEAR THESE FEROCIOUS CREATURES MAY BE LIVING AND PERHAPS BREEDING IN U.S. WATERS. HOWEVER, MOST EXPERTS BELIEVE THAT IF THESE BEASTS EXIST IN THE U.S., THEIR RANGE WOULD BE EXTREMELY LIMITED. >> IN NORTH AMERICA, THERE ARE FEW AREAS--OR AT LEAST, IN THE UNITED STATES, THERE ARE FEW AREAS WHERE PIRANHAS COULD LIKELY SURVIVE, POSSIBLY IN SOUTHERN FLORIDA, SOME SOUTHERN EXTREME PARTS OF TEXAS AND CALIFORNIA, ALSO HAWAII, OBVIOUSLY. >> narrator: MISSOURI'S LAKE OF THE OZARKS IS NOT AN AREA THAT FITS THIS DESCRIPTION. THE WATER TEMPERATURE HERE CAN REACH 90 DEGREES IN THE SUMMER, BUT DURING THE WINTER, MUCH OF THE LAKE FREEZES AND HAS AN AVERAGE TEMPERATURE BELOW 32 DEGREES. THE PIRANHAS BEING FOUND HERE ARE ALL PART OF THE RED-BELLIED SUBSPECIES, WHICH MAY BE ABLE TO BETTER TOLERATE TEMPERATURES BELOW 55 DEGREES. >> PIRANHAS ARE A LOT MORE DIVERSE THAN PEOPLE HAD REALIZED. THERE'S OVER 40 DIFFERENT SPECIES. THEY COME IN ALL DIFFERENT SIZES, VARIATION IN SHAPES. THEY FEED ON A LOT OF DIFFERENT THINGS. IT IS POSSIBLE THAT THERE ARE SOME PIRANHA POPULATIONS THAT HAVE GREATER TOLERANCE TO COOLER TEMPERATURES THAN OTHERS. SO IF YOU OBTAIN SOME PIRANHAS FROM, SAY, SOUTHERN BRAZIL-- WHICH IS GETTING MORE INTO SUBTROPICAL, POSSIBLY EVEN INTO TEMPERATE AREAS--THESE PIRANHA SPECIES MAY BE ABLE TO SURVIVE BETTER IN COOLER WATERS IN NORTH AMERICA. >> narrator: IN ORDER TO TEST THE THEORY THAT THE RED-BELLIED PIRANHAS CAN SURVIVE IN A COLD-WATER ENVIRONMENT, THE TEAM HAS SET UP AN EXPERIMENT AT THE AQUATROPICS AQUARIUM CENTER IN MINNEAPOLIS. >> WE'RE GONNA HOOK UP A CHILLER TO THE AQUARIUM. >> narrator: THE SCIENCE TEAM WILL SLOWLY LOWER THE WATER TEMPERATURE TO DETERMINE IF THE FISH CAN SURVIVE SEASONAL TEMPERATURE CHANGES IN THE LAKE OF THE OZARKS. >> WE HAVE A 66-GALLON AQUARIUM WITH FOUR FABULOUS SPECIMENS OF RED-BREASTED PIRANHA. WE'RE GOING TO INCREMENTALLY REDUCE THE TEMPERATURE OF THEIR ENVIRONMENT FROM A MEDIAN TEMPERATURE--RIGHT NOW, IT'S 75 DEGREES--AND BRING THEM DOWN TO ABOUT 50 DEGREES OVER THE COURSE OF FIVE DAYS. >> narrator: THE EXPEDITION TEAM IS SEARCHING THE LAKE FOR EVIDENCE THAT THE PIRANHAS AREN'T JUST SURVIVING HERE BUT BREEDING AS WELL. >> I SWIM WITH THEM ALL THE TIME HERE. >> narrator: THE TEAM LOSES RADIO CONTACT WITH DIVER DALE PEARSON. >> AH, [bleep], THERE'S MORE OF IT. [radio crackles] I'M GONNA TRY TO UNTANGLE MYSELF. I'LL BE FINE. JUST GIVE ME A SECOND. [bleep]. THERE'S A LOT OF THIS [bleep] DOWN HERE. >> narrator: SUDDENLY, HE EMERGES FROM THE MURKY WATER. [air h hsing] >> [gasps] THAT SUCKED. THIS AIN'T NO FISHING STRING. YOU CAN'T CUT THIS WITH A KNIFE. THAT WAS DICEY. IT WAS LIKE SOME DUDE TOOK A BUNCH OF THIS CRAP AND WAS LASHING LOGS OR, LIKE, MADE A RAFT OR SOMETHING. AND THIS STUFF WAS JUST STICKING UP ALL OVER, AND AS I SWAM OVER IT, IT JUST...WHOOP. >> THAT'S PART OF BEING AT A LAKE THAT'S GOT A LOT OF FISHERMEN. WE'VE PUT A LOT OF BRUSH PILES IN THE LAKE, AND SOME FISHERMEN WILL USE ELECTRICAL WIRE TO KEEP EVERYTHING SNUG TO THE BOTTOM, SO THEY KNOW WHERE IT IS. >> narrator: THE TEAM IS LOOKING FOR A CLEARER LOCATION TO PLACE THE UNDERWATER SURVEILLANCE CAMERA. THEY PICK A SPOT WHERE PIRANHAS HAVE BEEN KNOWN TO STRIKE BAIT. >> ALL RIGHT, DALE, THIS IS RIGHT NEAR THE 5-MILE MARKER. THIS IS WHERE A LITTLE GIRL CAUGHT A PIRANHA HERE RECENTLY. >> OKAY. >> AND THIS IS OUR NEXT DIVE SITE. SEE IF YOU CAN FIND ANYTHING. >> ALL RIGHT. WATER LOOKS BETTER HERE, LOOKS MORE CLEAR. >> MM-HMM, IT IS. >> YEAH, THE FIRST DEPLOYMENT OF THE AQUAPICS CAMERA SYSTEM, WE HAD A SEAL RUPTURE. AND WE GOT SOME WATER IN THE SYSTEM. WE WERE ABLE TO TAKE IT APART THAT NIGHT, DRY EVERYTHING OUT, AND LUCKILY, NOT ENOUGH WATER GOT IN THERE TO TOTALLY DESTROY THE SYSTEM. >> narrator: THE SECOND CAMERA SYSTEM WILL BE BAITED WITH CHICKEN TO SEE IF THE MEAT ATTRACTS THE FLESH-EATING PIRANHA. >> YOU KNOW, THE OTHER THING THAT'S PRETTY FREAKY IS, THAT LITTLE GIRL THAT CAUGHT THIS PIRANHA, IT WASN'T A LITTLE PIRANHA. IT WASN'T ONE OF THOSE LITTLE ONES THAT ARE JUST LIKE THE SIZE OF A BLUEGILL. IT WAS ABOUT 12 INCHES LONG. [air hisses] >> WATER TEMPERATURE, 57 DEGREES. >> COPY THAT, 57 DEGREES. >> ALL RIGHT, JACK, CAMERA AND BAIT ARE IN POSITION. I'M RETURNING TO THE DOCK. OVER. I'M KIND OF EXCITED TO SEE WHAT KIND OF VIDEO RESULTS WE GET OUT OF IT. >> narrator:<i> MONSTER QUEST</i> IS EXPLORING U.S. WATERS, SEARCHING FOR DEADLY FLESH-EATING PIRANHAS. THIS SPECIES HAS LONG BEEN KNOWN TO THRIVE IN THE WARMER CLIMATES OF SOUTH AMERICA. >> [speaking native language] >> PEOPLE WERE VERY AFRAID OF GOING INTO THE WATER. >> narrator: EIGHT-YEAR-OLD JACQUILE SABEJO WAS SWIMMING IN THE RIVER WITH A GROUP OF CHILDREN, WHEN SUDDENLY... [children yelling] THERE WAS A CHURNING IN THE WATER. >> THERE WAS A TOURIST BOAT AT THE SIDE OF THE RIVER, AND THE VISITORS THREW SOME FOOD AND STUFF IN THE WATER WHERE THE BOYS WERE SWIMMING. MY BOY GOT BITTEN. >> narrator: THE FOOD HAD ATTRACTED A PACK OF HUNGRY PIRANHAS, AND THE CHILDREN WERE CAUGHT IN THE MIDDLE. >> THE KIDS STARTED RUNNING OUT OF THE WATER. >> narrator: JACQUILE WAS NOT FAST ENOUGH. >> I WAS SHOCKED. MY BOY WAS BLEEDING HEAVILY. I SAW HIS TWO TOES WERE BITTEN OFF. PIECES OF THE TWO TOES WERE GONE. >> narrator: SURINAME LIES ON THE NORTHERN EDGE OF SOUTH AMERICA, JUST NORTH OF BRAZIL. THE SCIENCE TEAM HAS JOURNEYED HERE TO DETERMINE WHAT TRIGGERS THESE DEADLY FISH TO ATTACK. EXPEDITION LEADER LEE HALES MEETS WITH A LOCAL GUIDE WHO WILL TAKE HIM INTO THE REMOTE REACHES OF THE COUNTRY'S WILDERNESS. >> WHERE CAN WE FIND PIRANHAS HERE IN SURINAME? >> OKAY. >> SOME OF THESE TOWNS ARE SO REMOTE; THE ONLY WAY YOU CAN GET TO THEM IS BY BOAT. SO THAT IN ITSELF IS GOING TO BE INTERESTING. BENEATH THESE WATERS THAT ARE DARK AND MURKY, LAYS A CREATURE THAT HAS THE ABILITY TO ATTACK AT ANY POINT IN TIME WITHOUT ANY PROVOCATION. YEAH, IN A LOT OF RESPECTS, I AM SOMEWHAT AFRAID OF THE PIRANHA AND WHAT THEIR CAPABILITIES ARE, 'CAUSE YOU JUST DON'T KNOW. >> narrator: THE TEAM WILL TRAVEL TO SURINAME'S REMOTE INTERIOR, AN EIGHT-HOUR JOURNEY ALONG THE PIRANHA-INFESTED COPPERNAME AND WAYOMBO RIVERS. THE ENTIRE TRIP WILL BE MADE BY DUGOUT CANOE. >> YEAH, THIS IS BY FAR SOME OF THE WILDEST THINGS I'VE SEEN. THIS IS JUST SO FAR REMOVED FROM THE REST OF THE WORLD THAT ANYTHING COULD BE HERE. SO THIS IS IT. >> YEAH. >> OH, THIS IS INCREDIBLE. >> SO THIS IS AN AREA, A LOT OF ATTACKS. >> 32. >> narrator: THE TEAM ARRIVES IN THE REMOTE VILLAGE OF DONDERSKAMP, WHERE THE LOCALS LIVE IN FEAR OF THE FLESH-EATERS. >> HELLO. >> NICE TO MEET YOU. >> [speaking native language] >> THE BITES WERE FROM VERY LIGHT BITES TO VERY BAD BITES. THEY WERE MISSING FINGER PIECES, TOE PIECES. THE WOUNDS WERE SEVERE. >> narrator: JAN MANDE, A LOCAL DOCTOR, HAS TREATED MOST OF THE PIRANHA BITE VICTIMS. >> WOW, THIS IS--THIS-- ALL OF THESE PEOPLE HERE. THIS IS A LONG LIST OF PEOPLE. IT'S SOMETHING. >> THIS ONE? MM. >> THIS PERIOD WAS VERY BAD, BECAUSE YOU'D ONLY HAVE TO ENTER THE WATER OR SPLASH WITH YOUR FINGERS OR FEET, AND YOU WOULD GET BITTEN. THERE WERE MANY PEOPLE MISSING FINGERTIPS OR PARTS OF THEIR TOES. PEOPLE WERE VERY AFRAID. THEY WERE SCARED. THEY WERE VERY AFRAID OF GOING INTO THE WATER. >> narrator: THEN THERE IS A SUDDEN COMMOTION ON A NEARBY DOCK. A FISHERMAN HAS CAUGHT A LARGE BLACK PIRANHA. >> PULL BACK THE LIPS TO SEE... >> IT'S A...[grunts] WHEN THEY'RE CAUGHT. SEE THE TEETH? >> NASTY. WOW. >> YEAH. >> I MEAN, THAT IS TRULY PREDATOR TEETH. THAT IS SOMETHING. WOW. [kids talking excitedly] [camera clicks] HOW MANY? >> SEE THE TEETH? >> narrator: THE DOCTOR HAS TOLD THE TEAM ABOUT A NEARBY LAKE THAT HAS ONE OF THE LARGEST POPULATIONS OF PIRANHA IN THE COUNTRY, AN IDEAL LOCATION FOR TESTING ATTACK TRIGGERS. WOW, THIS IS-- LARGE RESERVOIR. LOOK AT THIS. ABSOLUTELY BEAUTIFUL. YEAH. ALL RIGHT. SAFETY FIRST. >> YEAH. [mot whirring] >> SO THIS IS, MORE OR LESS, A MAN-MADE LAKE. AND NOW BECAUSE OF THAT, THERE'S A LOT OF PIRANHA IN THIS AREA. HOW MUCH DO YOU THINK? >> DO SOME OF THE PEOPLE LIVE ALONG THE EDGE OF THIS RESERVOIR? >> SO THEY HAVE TO--THEY COME DOWN AND BATHE IN THE WATER, AS WE'RE SEEING IN THESE OTHER LOCATIONS. >> YEAH, THEY BATHE IN THE WATER. >> DO THEIR LAUNDRY, WASH THEIR DISHES RIGHT IN THE RESERVOIR. WELL, IT'S KIND OF A HOT DAY TODAY, AND NORMALLY I WOULDN'T MIND GOING SWIMMING, BUT I FEEL A LITTLE APPREHENSIVE IN THIS AREA. >> narrator: THE TEAM HAS FOUND A GOOD PLACE FOR THEIR TEST. FIRST, THEY'LL TRY TO DETERMINE WHAT TYPE OF PREY IS MOST LIKELY TO TRIGGER THE PIRANHAS TO ATTACK. [speaking indistinctly] >> ALL RIGHT, WE'RE IN AN AREA WHERE THERE'S A LOT OF PIRANHA. AND WE SEE A LOT OF LITTLE BAITFISH RIGHT THROUGH HERE, AND WE HAVE THE ADVANTAGE OF ALL OF THESE DEAD TREES. SO WE'RE GOING TO USE THESE TO RUN A LINE ACROSS AND HANG THIS CHICKEN JUST BENEATH THE SURFACE, AND WE'RE GONNA SEE EXACTLY HOW FEROCIOUS THESE GUYS ARE AND HOW MUCH DAMAGE IT'S GONNA DO TO THIS CHICKEN IN A SHORT PERIOD OF TIME. MAKE SURE WE USE EVERY LITTLE BIT, PUT A LITTLE BLOOD RIGHT THERE IN THE WATER. THEY ARE ATTRACTED TO BLOOD MUCH LIKE SHARKS ARE. [water splashing] CALLING THEM, DINNERTIME. >> narrator: THE TEAM SETS SEVERAL NETS WITH RAW CHICKEN BAIT. >> ALL RIGHT, WE'RE HOPING WE'RE GONNA COME BACK, AND WE'RE GONNA GET A FIRSTHAND EXAMPLE OF WHAT A PIRANHA IS CAPABLE OF. >> narrator: THE TEAM ALSO SETS UP A NET DESIGNED TO SNAG FISH AS THEY SWIM BY. >> AND I WANT TO SET A GILL NET OUT HERE JUST SO WE HAVE A COUPLE OF DIFFERENT THINGS WE CAN TRY TO SEE WHAT TYPE OF PIRANHA LIVE IN THIS AREA, HOW MANY, HOW BIG. >> narrator: THE TEAM CHECKS THEIR TRAPS THROUGHOUT THE DAY. >> SEE WHAT WE GOT HERE. ALL RIGHT, COME ON. WELL, IT'S STILL INTACT. MAYBE WE HAVEN'T LEFT IT HERE LONG ENOUGH. >> narrator: THERE IS NO EVIDENCE THAT PIRANHAS ARE DRAWN TO THE CHICKEN. BUT A CHECK OF THE GILL NETS PROVES THERE ARE PIRANHAS IN THE AREA. >> I SEE ONE. >> OH, THERE'S ANOTHER. ONE PIRANHA. >> YEAH. >> AND HE'S BEEN IN THERE AWHILE. JUST LOOK AT HIM SNAPPING. >> YEAH. >> NICE, LOOK AT THAT. >> YEAH, STILL. >> TWO GOOD-SIZE PIRANHA RIGHT NEXT TO ONE ANOTHER. >> YEAH, HE'S BITING ON IT. >> OH, YEAH, LOOK AT THAT. JUST ABOUT EVERY FISH WE'VE CAUGHT HAS BITES RIGHT OUT OF THE FIN, SO THAT'S TELLING ME THAT THE PIRANHA, AS THEY'RE FEEDING, ARE EVEN NIPPING ON ONE ANOTHER. >> narrator: THE TEAM DECIDES THAT A LIVE TRIGGER MIGHT BE MORE ATTRACTIVE TO THE PIRANHA. THEY SET THE TRAP WITH NEW BAIT. >> WELL, IT'S GETTING KIND OF LATE. WE'RE LOSING LIGHT. BUT IT'S WORTH A TRY HERE. MAYBE THEY'RE GONNA COME OUT AND BE A LITTLE MORE AGGRESSIVE AS IT STARTS TO GET DARK. SOME OTHER FISH ARE COMING IN, SO WE'LL SEE IF WE CAN END THE DAY ON A GOOD NOTE AND CATCH A FEW PIRANHA HERE. >> narrator: THE RESULTS ARE IMMEDIATE. [reel whirs] >> VERY NICE ONE. NICE. HERE WE GO. HERE WE GO. OH, YEAH. LOOK AT THAT. LET'S SEE. OH, YEAH. LISTEN TO THAT. HE'S EVEN MAKING, LIKE, A LITTLE VOCALIZATION TOO. OH, HE'S GOT A HOLD OF THAT KNIFE. >> narrator: THE MOVEMENT SEEMS TO BE THE KEY THAT TRIGGERS THE PIRANHAS TO ATTACK, PUNCTURE, AND SHRED. >> SEE IF WE... PIRANHA. I GOT IT. THEY'RE DOING LAUNDRY RIGHT OVER THERE. AT ABOUT THE THIRD OR FOURTH CAST WITH THIS LURE, OUT COMES THIS PIRANHA. WOW. >> narrator:<i> MONSTER QUEST</i> HAS TRAVELED TO MISSOURI TO DETERMINE WHETHER PIRANHAS HAVE INVADED THE LAKE OF THE OZARKS AND ARE BREEDING HERE. PARTS OF THIS LAKE FREEZE EVERY WINTER, WITH THE WATER TEMPERATURES DROPPING INTO THE 30s. THE SCIENCE TEAM HAS THEORIZED THAT THE RED-BELLIED PIRANHA MIGHT BE ABLE TO SURVIVE IN LOW WATER TEMPERATURES. >> OVER THE COURSE OF THESE FOUR DAYS, WE'VE NOW DROPPED THE TEMPERATURE DOWN TO 60 DEGREES FAHRENHEIT. I WOULD SAY, UNTIL WE REACHED THE POINT OF 65 DEGREES, THE BEHAVIOR WAS VERY NATURAL, VERY NORMAL. WHEN I GOT TO 65 DEGREES, I NOTICED ONE DRAMATIC CHANGE IN BEHAVIOR. THEY BECAME VERY TERRITORIAL, ALMOST AGGRESSIVE TOWARDS EACH OTHER. WE HAD SEPARATION OF THE FISH RATHER THAN SCHOOLING. NOW TODAY, PROBABLY THE MOST SIGNIFICANT CHANGE I'VE SEEN, WE JUST WENT FROM 65 DEGREES DOWN TO 60 DEGREES. THESE FISH HAVE COMPLETELY CHANGED THEIR TEMPERAMENT. WE HAVE MUCH LESS ACTIVITY, ALMOST SLUGGISH. COLORATION IS STILL GOOD, BUT THESE FISH ARE NOT AGGRESSIVE TOWARDS EACH OTHER. >> narrator: OVER THE NEXT 24 HOURS, THE TEAM WILL TEST THEIR THEORY BY DROPPING THE WATER TEMPERATURE TO 55 DEGREES AND BELOW. >> OF COURSE, WE DON'T WANT TO HARM THE FISH, BUT WE DO WANT TO SEE WHERE THE THRESHOLD IS. WHERE DO THESE FISH TEND TO SHUT DOWN? WHERE DO THEY BECOME SO LETHARGIC THAT WE KNOW THEY JUST COULDN'T SURVIVE ANY COOLER? I THINK THESE FISH ARE GOING TO TRIP INTO A SURVIVAL MODE RATHER THAN, "I'M GONNA PROSPER" MODE. TIME WILL TELL. >> narrator: DESPITE THE EVIDENCE, SOME SCIENTISTS ARE SKEPTICAL THAT PIRANHAS COULD SURVIVE IN THE U.S. >> I'VE BEEN A BIOLOGIST HERE AT LAKE OF THE OZARKS SINCE 1991, AND DURING THAT TIME, I HAVE HEARD OF PROBABLY THREE, FOUR, MAYBE FIVE PEOPLE CATCHING PIRANHA. I'VE HAD A COUPLE OF THEM SEND PICTURES TO ME, AND THEY WERE THE RED-BELLIED PIRANHA. MORE THAN LIKELY, THESE FISH WERE PEOPLE--YOU KNOW, THEY ORIGINATED FROM PEOPLE. THEY HAD THEM IN AN AQUARIUM, AND THEY EITHER GOT TIRED OF THEM AND LET THEM GO, YOU KNOW, INTO THE LAKE. >> narrator: THE FACT REMAINS THAT A NUMBER OF PIRANHAS HAVE BEEN CAUGHT IN THE LAKE OF THE OZARKS OVER CONSECUTIVE YEARS, LEADING SOME TO SUSPECT THE BEASTS MAY BE BREEDING. [electronic beep] >> THIS IS A HUGE LAKE, DUDE. THE CHANCES OF ONE PERSON LETTING A PIRANHA GO AND THEN SOMEONE ELSE CATCHING IT-- THERE'S GOT TO BE A POPULATION OF PIRANHAS IN HERE. >> narrator: THE EXPEDITION TEAM IS TRYING TO DETERMINE IF THE PIRANHAS ARE SURVIVING THE WINTERS HERE. >> WHAT WE'RE TRYING TO ACCOMPLISH IS TO PROVE THAT THE HABITAT EXISTS TO MAINTAIN A POPULATION OF PIRANHAS. >> narrator: THE TEAM IS JOINED BY THE MISSOURI DEPARTMENT OF CONSERVATION. >> SO WE'RE COMING UP RIGHT NOW. THIS IS THE MISSOURI DEPARTMENT OF CONSERVATION. THEY'RE DOING TRAPS-- TRAP NETS OUT HERE. AND WE'RE GONNA GET A CHANCE TO WORK WITH THEM TODAY AND SEE WHAT KIND OF STUFF THAT THEY'RE GETTING WHEN THEY PULL THESE NETS UP. >> narrator: THE DEPARTMENT OF CONSERVATION HAS BEEN MONITORING FISH POPULATIONS CAREFULLY, LOOKING FOR SIGNS OF THESE KILLER FISH. >> WHAT WE'RE DOING TODAY IS RUNNING TRAP NETS FOR CRAPPIE. WE DO AN ANNUAL SURVEY. ON A GIVEN DAY, WE'LL CATCH ANYWHERE FROM 200 TO MAYBE 500 CRAPPIE. >> narrator: THE TEAM WILL CHECK THE NETS TO SEE IF THEY SNAG ANY OF THE INVADING PIRANHAS. >> SO HOW MANY OF THESE NETS DO YOU GUYS PUT OUT? >> WE RUN 15 NETS. >> WHITE CRAPPIE. 8.9. >> narrator: BUT SO FAR, THERE IS NO SIGN OF THE MONSTER. >> BLACK, 8.4. >> narrator: WHILE THE WATER TEMPERATURE HERE IS COLD, THERE ARE PARTS OF THE LAKE OF THE OZARKS THAT ARE FED YEAR-ROUND BY UNDERWATER SPRINGS. THIS MEANS, PARTS MAY REMAIN WARM ENOUGH FOR THE FLESH-EATERS TO SURVIVE YEAR-ROUND. >> ALL RIGHT, DALE. THIS IS THE SPOT I WAS TALKING ABOUT. THIS IS THE SPRING WHERE IT ENTERS INTO THE LAKE. RIGHT OVER HERE, ABOUT 1/4 MILE, IS WHERE IT COMES OUT OF THE CAVE. >> ALL RIGHT. >> THIS IS 48 MILLION GALLONS OF WATER A DAY. >> 48 MILLION GALLONS A DAY POURING OUT OF HERE? >> COMES RIGHT THROUGH HERE. >> SO WHERE CAN I GET IN THE WATER? THAT--I AIN'T GETTING IN RIGHT THERE. >> YEAH, THERE'S NO ACCESS BEYOND THIS POINT. >> narrator: THE TEAM HAS A THEORY THAT PIRANHAS MIGHT BE ABLE TO SURVIVE IN 55-DEGREE WATER, AND THIS AREA MIGHT BE JUST WARM ENOUGH. >> THIS IS THE KEY PART. I BELIEVE THIS WATER TEMPERATURE DOES NOT FLUCTUATE LIKE THE REST OF THE LAKE DOES. >> OKAY. >> THIS WATER TEMPERATURE SHOULD STAY SOMEWHERE AROUND MID-50s TO UPPER 50s. AND IF THERE'S GONNA BE A SPOT-- IF THERE'S GONNA BE PIRANHAS IN THIS LAKE, THEY SHOULD BE ABLE TO COME HERE IN THE WINTERTIME, AND THEY SHOULD BE FINE. >> I'LL GET IN RIGHT THERE WHERE THAT CURRENT IS. >> BE REAL CAREFUL. THERE'S LOTS OF SNAGS DOWN HERE. I'VE FISHED DOWN HERE. >> narrator: THEY ATTEMPT TO MANEUVER TO A LOCATION WHERE THEY CAN TAKE THE NECESSARY READINGS. >> THIS IS THE ACCESS? OKAY, SO YOU WANT TEMPERATURE READINGS, DEPTH OBSERVATION, STRUCTURE OBSERVATION. >> narrator: IF THEY CAN PROVE THE WATER TEMPERATURE STAYS WELL ABOVE FREEZING, IT WOULD MEAN THE LAKE IS A VIABLE HABITAT FOR THE FISH. [radio crackles and beeps] >> narrator: PEARSON DIVES TO THE SOURCE OF THE SPRING WHILE FIGHTING A STRONG CURRENT. >> 59 DEGREES. >> COPY, DIVER. >> AND THIS WATER IS STABLE. THIS WATER TEMPERATURE DOESN'T CHANGE BECAUSE IT COMES STRAIGHT OUT OF THE EARTH. >> WHY, THANK YOU. THAT'S WHAT WE WANTED TO FIND OUT, IS WHAT THE BOTTOM TEMPERATURE IS, WHAT'S THE LOWEST THIS LAKE GETS, AND IT LOOKS LIKE 57 DEGREES IS IT IN THIS SPRING AREA. >> narrator: THE WATER TEMPERATURE ALSO RISES TO BETWEEN 70 AND 90 DEGREES IN THE SUMMER MONTHS, WHICH IS IDEAL FOR PIRANHA BREEDING. >> SO NOW YOU'VE GOT A CONSISTENT WATER TEMPERATURE THAT CAN KEEP THEM ALIVE. YOU HAVE A BREEDING TEMPERATURE IN THE SUMMERTIME, WHERE THEY CAN BREED, AND YOU HAVE A LAKE WITH AS MUCH COASTLINE AS THE STATE OF CALIFORNIA. SO HUGE BODY OF WATER. THE TEMPERATURES ARE LIVABLE. THERE'S PLENTY OF FOOD IN THE LAKE. THERE'S SHAD AND ALL KINDS OF STUFF ALL OVER. SO I DON'T SEE--I'M TRYING TO FIND REASONS WHY THEY COULDN'T BE HERE. >> narrator: THE EXPEDITION TEAM RETURNS TO A POSITION ON LAKE OF THE OZARKS CALLED 5-MILE MARKER. A FLESH-EATING PIRANHA WAS RECENTLY CAUGHT IN THE AREA. EARLIER, THE TEAM SET A TRAP HERE, HOPING TO GET EVIDENCE OF A PIRANHA. >> HE SAID, "IT'S ACTUALLY A LITTLE SHREDDED UP." PRETTY SURPRISED. >> PULL IT UP. >> OH, WOW. WOW, LOOK AT THAT. IT'S ACTUALLY BEEN CHEWED UP QUITE A BIT. >> narrator:<i> MONSTER QUEST</i> IS IN MISSOURI ON LAKE OF THE OZARKS, SEARCHING FOR EVIDENCE THAT FLESH-EATING PIRANHAS MAY BE SURVIVING AND BREEDING IN THESE WATERS. THIS MAN CAUGHT A PIRANHA IN A TENNESSEE LAKE. THIS RESEARCHER IS STUDYING HOW MUCH COLD PIRANHAS CAN TOLERATE. AND THIS RESEARCHER IS TESTING PIRANHAS IN THEIR NATURAL HABITAT TO SEE WHAT TRIGGERS THEM TO ATTACK. THE EXPEDITION TEAM IS EXAMINING THE BAITED CAMERA TRAPS. SOMETHING HAS CLEARLY ATTACKED THE BAIT. >> DEFINITELY--DEFINITELY SOME CHEWING GOING ON HERE. THIS HAS BEEN PULLED AT. >> I THINK SOMETHING CAME IN FROM THE SCENT OF IT THAT WAS A LARGER PREDATOR. >> WELL, DID YOU SEE ANY MORE FISH DOWN THERE? >> ACTUALLY, NO. I WAS SURPRISED. I WENT DOWN. I LOOKED, FOUND THE CHICKEN. IT WAS SHREDDED UP FOR REAL, AND THERE WAS NOTHING AROUND. >> narrator: THE TEAM CHECKS THE UNDERWATER FOOTAGE, BUT NONE OF THE CAMERAS SHOW PIRANHAS, ONLY NATIVE FISH. IT'S POSSIBLE THE MURKY CONDITIONS OBSCURED SOMETHING ELSE FEEDING ON THE BAIT. >> YEAH, IT'S--IT'S KIND OF FUNKY BEING IN THIS LAKE, HONESTLY, BECAUSE THE LIGHT DROPS EXTREMELY FAST. LIKE, WHEN YOU GO DOWN THERE, YOU LOSE LIGHT PRETTY MUCH IMMEDIATELY. IF THERE'S A SCHOOL OF PIRANHA IN HERE, YOU'RE NOT GONNA FIND THEM. THE VISIBILITY IN HERE IS TO THE POINT TO WHERE ANY FISH, IT'S JUST GONNA DISAPPEAR. >> narrator: THE EXPEDITION TEAM HAS DETERMINED THAT THERE ARE PARTS OF THE LAKE THAT REMAIN AT 57 DEGREES EVEN IN WINTER. AND THE SCIENCE TEAM IS TESTING TO SEE IF THE RED-BELLIED PIRANHA CAN SURVIVE AT THAT TEMPERATURE. THEY'VE REDUCED THE TEMPERATURE AROUND THE TEST SUBJECTS OVER THE COURSE OF SEVERAL DAYS. >> OF COURSE, WE DON'T WANT TO HARM THE FISH, BUT WE DO WANT TO SEE WHERE THE THRESHOLD IS. WHERE DO THESE FISH TEND TO SHUT DOWN? WHERE DO THEY BECOME SO LETHARGIC THAT WE KNOW THEY JUST COULDN'T SURVIVE ANY COOLER? >> narrator: ON DAY FIVE, THERE ARE PROFOUND CHANGES. >> WE GET DOWN TO 53 DEGREES, AND THESE FISH STARTED TO HUDDLE TOGETHER. THEY LITERALLY LINED UP IN A ROW AS THOUGH THEY WERE ALMOST ABSORBING EACH OTHER'S BODY HEAT, THE LITTLE THAT THERE WAS. BUT AS WE CONTINUED TO DROP DOWN TO 52, YOU COULD TELL THE DISORIENTATION BECAME EVIDENT. THE FISH WOULD SWIM AWKWARDLY, ALMOST LABORED. THEY WOULD HUDDLE TOGETHER AT ONE POINT, AND THEN ALMOST AS THOUGH THE INSTINCT OF SURVIVAL WERE TRYING TO STEP IN, THEY WOULD TAKE OFF AND TRY TO SWIM FOR ACTIVITY, ALMOST TO WARM UP. >> narrator: CONDENSATION COVERS THE NOW FRIGID TEST TANK. >> THE DROP IN TEMPERATURE FROM 55 DOWN TO 50 DEGREES WAS THE BIG ONE. WE SAW THE GREATEST AMOUNT OF CHANGE. >> narrator: THE PIRANHAS LOSE THEIR ABILITY TO STAY UPRIGHT AT TEMPERATURES OF 50 DEGREES. THEIR EQUILIBRIUM IS GONE. >> THE FISH, I DO BELIEVE, WOULD SURVIVE FAIRLY COMFORTABLY IN THE MID TO UPPER 50s. >> narrator: THIS<i> MONSTER QUEST</i> EXPEDITION HAS TURNED UP SOME INTERESTING RESULTS. THE SCIENCE TEAM HAS DETERMINED THAT RED-BELLIED PIRANHAS WILL ADAPT AND HUDDLE TOGETHER TO SURVIVE AT COOLER TEMPERATURES. IT WILL TAKE WATER TEMPERATURES BELOW 50 DEGREES TO KILL THEM. AND THE EXPEDITION TEAM HAS IDENTIFIED SPRING-FED WATERS IN LAKE OF THE OZARKS THAT STAY IN THE HIGH 50s YEAR-ROUND. >> MY GUT TELLS ME, THERE'S VERY FEW PIRANHAS IN THIS LAKE. THERE IS PROBABLY A HANDFUL OUT THERE. >> IT WOULD EASILY BECOME AN A-LIST PREDATOR AND ACTUALLY HAVE VERY DEVASTATING EFFECTS ON THE NATIVE FISH SPECIES, NOT TO MENTION THE ENCOUNTERS THAT YOU'RE GOING TO HAVE WITH HUMANS AND OTHER ANIMALS THAT MIGHT VENTURE INTO THE WATER. >> STOP, PLEASE, STOP. >> SO THE SCARY THING IS, IS THAT ON A BODY OF WATER THE SIZE OF LAKE OF THE OZARKS, IF YOU GET A PIRANHA BREEDING POPULATION IN HERE, YOU'RE NEVER GONNA GET IT OUT. IT'S JUST GONNA GET BIGGER AND BIGGER AND BIGGER.
