WHY DO SOME SNAKES HAVE INTERNAL BONES
LEFTOVER FROM LEGS?
WHY DOES THE CLOWNFISH CHANGE GENDERS?
HOW COME THE MALE SEAHORSE HAS THE BABIES?
AND WHY DO FEMALE CHEETAHS CHEAT?
THESE CREATURES HAVE INTERNAL ADAPTATIONS
THAT ARE HELPING THEM SURVIVE.
(♪♪♪)
SLITHERING ON THE GROUND, FLICKING THEIR TONGUES,
IT'S EASY TO SEE WHY SNAKES CAN BE SCARY.
ESPECIALLY TO A RAT.
BUT IF YOU CAN GET PAST THE BITING AND THE VENOM,
SNAKES HAVE SOME PRETTY COOL FEATURES.
WHERE DID SNAKES COME FROM IN THE FIRST PLACE?
WHILE MANY POINTS OF THEIR ANCESTRY REMAIN A MYSTERY,
WHAT WE DO KNOW NOW
IS THAT SNAKES ARE VERY SPECIALIZED LIZARDS.
&gt;&gt; WELL, THE EVOLUTION ANCESTRY OF SNAKES
IS NOT TOTALLY RESOLVED,
BUT IT SEEMS THAT THE SNAKES ARE DEEPLY EMBEDDED
WITHIN THE LIZARD TREE.
SO SNAKES ARE JUST A VERY SPECIALIZED LIZARD,
THEY'RE NOT A DIFFERENT GROUP THAN LIZARDS,
THEY'RE REALLY PART OF THE GROUP.
AND THE CLOSEST RELATIVES ARE VARANID LIZARDS,
THERE'S THESE LONG MONITOR LIZARDS
THAT IF YOU LOOK AT THEM, THEY LOOK A BIT LIKE A SNAKE.
THEY HAVE REDUCED LEGS,
THEY SORT OF GLIDE ON THEIR BELLIES A LOT.
AND SO THEY'RE BASICALLY A SISTER
WHO TACKS ON TO VARANID LIZARDS.
&gt;&gt; SO WHEN DID SNAKES EMERGE AS A SEPARATE GROUP?
AND WHY DID THESE LIZARDS LOSE THEIR LEGS?
WHILE FOSSILS OF THE EARLIEST SNAKES ARE RARE,
THERE ARE SOME HINTS IN THEIR EVOLUTIONARY HISTORY
THAT HELP PIECE THE STORY TOGETHER.
ALL MODERN SNAKES DESCENDED
FROM AN ANCIENT ORDER OF REPTILES NAMED THE SQUAMATA,
ALSO KNOWN AS THE SCALY ONES.
THE OLDEST SQUAMATE FOSSILS
DATE BACK ROUGHLY 200 MILLION YEARS,
AROUND THE TIME THAT THE SUPER CONTINENT OF PANGEA DIVIDED.
BUT THESE FOSSILS ALSO SUGGEST
THAT THIS GROUP OF REPTILES HAD BEEN EVOLVING
BEFORE THE CONTINENT WAS SEPARATED.
THE ANCESTOR OF THE SQUAMATES OR THE SQUAMATES THEMSELVES
WERE LIKELY AROUND MILLIONS OF YEARS BEFORE.
NOW, MANY MILLIONS OF YEARS LATER,
WE HAVE SEVEN CONTINENTS
AND THOUSANDS OF SNAKE SPECIES ON THE PLANET.
MODERN SNAKES ARE STILL SQUAMATES,
BUT HAVE EVOLVED IN THEIR OWN SUBORDER.
BUT THE MYSTERY STILL REMAINS
IF SNAKES CAME FROM SQUAMATES, WHO ONCE HAD LEGS,
WHAT ADVANTAGE COULD THEY GAIN FROM LOSING THEM?
IT'S BELIEVED THAT SNAKES LOST THEIR LEGS
THROUGH EVOLUTION,
BECAUSE THE ANCESTRAL SNAKES WERE FOSSORIAL,
WHICH MEANS ADAPTED FOR DIGGING.
&gt;&gt; SO THEY WOULD BURY ON THE GROUND.
AND WHEN YOU'RE USING TUNNELS AND ALL THESE THINGS
AND LEGS JUST GET IN THE WAY,
THEY'RE NOT USED FOR TUNNELING UNDERGROUND.
SO THE EVOLUTION OF SNAKES
WAS PROBABLY THROUGH FOSSORIAL HABITS,
SO LIZARDS THAT WERE HIGHLY FOSSORIAL
GOT REDUCED AND REDUCED LIMBS UNTIL THEY DISAPPEARED.
WHILE SNAKES HAVE COMPLETELY LOST THEIR LIMBS
ON THE OUTSIDE,
THE INTERNAL BONE STRUCTURE OF SOME SPECIES CONTAINS AN ECHO
FROM THE OLD DAYS.
PRIMITIVE SNAKES SPECIES LIKE BOAS AND PYTHONS
STILL HAVE SOMETHING CALLED A PELVIC GIRDLE.
&gt;&gt; THE PELVIC GIRDLE IS BASICALLY THE REMNANTS
OF BACK LEGS OF THE ANCESTRAL LIZARD.
IN THE MOST ANCESTRAL SNAKES,
YOU CAN FIND REMNANTS OF THE PELVIC GIRDLE,
SO YOU CAN SEE BONES INSIDE.
AND IN BOAS AND PYTHONS,
THEY HAVE SPURS ON EACH SIDE OF THEIR CLOACA
THAT ARE DERIVED FROM THE ANCESTRAL PELVIC GIRDLE.
SNAKES THAT DO NOT HAVE THIS PELVIC GIRDLE
IN THEIR SKELETON
ARE FARTHER ALONG ON THE EVOLUTIONARY CONTINUUM
WITHOUT A TRACE OF LEG STRUCTURE ANYWHERE.
(♪♪♪)
SO WHILE THAT PELVIC GIRDLE IS SOMETHING NEAT TO SEE,
YOU MAY WANNA KEEP AN EYE OUT FOR THOSE BIG TEETH,
ESPECIALLY IF YOU'RE A RAT.
(♪♪♪)
AN ANIMATED MOVIE MADE THIS FISH FAMOUS
OUTSIDE THE OCEAN.
BUT AN UNCOMMON OCCURRENCE
INSIDE THAT COLORFUL LITTLE BODY
HELPS THE CLOWNFISH SURVIVE.
CLOWNFISH ARE FUNNY,
BUT NOT FUNNY HAHA,
FUNNY UNUSUAL.
PARTLY BECAUSE OF THEIR SEX.
A MALE CLOWNFISH DOESN'T ALWAYS STAY THE SAME SEX
FOR ITS ENTIRE LIFETIME.
AND WHEN NECESSARY,
IT CAN CHANGE ITS INTERNAL SEXUAL ORGANS
FROM MALE TO FEMALE.
BUT WHY MUST THIS FISH UNDERGO SUCH A TRANSFORMATION?
TO BETTER UNDERSTAND THE CLOWNFISH
WE MUST UNDERSTAND WHERE IT LIVES.
CLOWNFISH HAVE BEEN SWIMMING IN THE SHALLOWS SEAS
OF THE WESTERN INDO-PACIFIC FOR MILLIONS OF YEARS.
THEY SPEND THEIR DAYS AND NIGHTS
IN THE MIDDLE OF A POISONOUS AND PARALYZING SEA ANEMONE.
IT'S A FUNCTIONAL SYMBIOTIC RELATIONSHIP.
(♪♪♪)
&gt;&gt; AN ANEMONE IS A SIMPLE ANIMAL RELATED TO THE POLYPS OF CORALS
OR JELLY FISH THAT HAS LONG STINGING TENTACLES.
&gt;&gt; THE TENTACLES ON THESE ANEMONES HAVE
SPECIALIZED STINGING CELLS CALLED CNIDOBLASTS,
THAT DELIVER A TOXIN THAT MOST FISHES WOULD RATHER AVOID.
BUT CLOWNFISH DON'T SEEM TO MIND.
THEY EVEN PERFORM A DANCE.
LIVING AMONG THE ANEMONE,
CLOWNFISH GENTLY TOUCH THE TENTACLES
WITH DIFFERENT PARTS OF THEIR BODY
UNTIL THEY ARE A CONSTANT TO THEIR NEW HOST.
BUT HOW DID CLOWNFISH EVOLVE
TO LIVE WITH SUCH A TEMPERAMENTAL LANDLORD?
THEY'VE EVOLVED IMMUNITY TO THE TENTACLES OF THE ANEMONE
BY COATING THEIR BODY WITH A MYSTERIOUS MUCOUS.
NO ONE KNOWS WHERE THE MUCOUS COMES FROM,
BUT SCIENTISTS HAVE PROMISING LEADS.
ONE THEORY HOLDS THAT CLOWNFISH PRODUCE THE MUCOUS ON THEIR OWN
AND THAT IT CONTAINS CHEMICALS
THAT PREVENT THE ANEMONE FROM STINGING THEM.
ANOTHER THEORY IS THAT CLOWNFISH
GET THE MUCOUS FROM THE ANEMONES THEMSELVES
WHEN THEY PERFORM THEIR ELABORATE DANCE,
RUBBING THEIR BODY AGAINST THE TENTACLES
AND COATING THEMSELVES WITH MUCOUS IN THE EXCHANGE.
THIS COATING TRICKS THE ANEMONE,
A PHENOMENON CALLED CHEMICAL CAMOUFLAGE.
BUT IS THIS A ONE-SIDED RELATIONSHIP?
WHAT DOES THE SEA ANEMONE GET IN RETURN?
CLOWNFISH ACTUALLY DO A LOT OF THE HOUSE CLEANING
TO SUPPLEMENT THEIR RENT.
THEY PREEN THE TENTACLES OF THE ANEMONE,
REMOVING PARASITES
AND DRIVING OFF POTENTIAL INTRUDERS.
ONE STUDY SUGGESTS
THAT THEY FERTILIZE THE ANEMONE WITH THEIR AMMONIA-RICH WASTE.
BASICALLY, MISSING THE TOILET IS A GOOD THING IN THIS PLACE.
AND ANOTHER THEORY SUGGESTS
THAT CLOWNFISH HELP THE ANEMONE BREATH AT NIGHT
BY SWIMMING AROUND THE TENTACLES
AND FANNING OXYGEN-RICH WATER OVER THE ANEMONE'S BODY.
SO THIS ODD PAIRING APPEARS TO BE WORKING OUT.
CLOWNFISH SEEM TO BE VERY TERRITORIAL OF THEIR ANEMONE
AND NEVER STRAY FAR FROM HOME.
BUT LIVING IN A STINGING HOME
IS NOT THE ONLY THING OFFBEAT ABOUT CLOWNFISH.
THE MALES HAVE A HANDY LITTLE TRICK THEY USE
IF THEY ARE IN A PINCH FOR SOME FEMALE COMPANY.
CLOWNFISH HAVE EVOLVED TO CHANGE GENDERS
WHEN THE DOMINANT BREEDING FEMALE IN A HIERARCHY DIES.
&gt;&gt; CLOWNFISH ARE KNOWN TO HAVE SEQUENTIAL HERMAPHRODITISM.
SO WHAT THAT MEANS IS THAT THEY ARE ONE SEX
AT ONE POINT OF THEIR LIFE AND ANOTHER SEX AT ANOTHER.
THEIR SOCIETIES ARE HIGHLY STRATIFIED,
BEING DOMINATED BY THE DOMINANT FEMALE.
IF A DOMINANT FEMALE DIES, THE NEXT DOMINANT MALE
WILL UNDERGO A SEXUAL TRANSFORMATION
AND BECOME THE FOLLOWING DOMINANT FEMALE.
&gt;&gt; ACCORDING TO ONE THEORY
CLOWNFISH DON'T LEAVE THEIR TERRITORY OFTEN,
BECAUSE THEY ARE WAITING IN LINE TO BE THE NEXT ONES
TO INHERIT THE REPRODUCTIVE THRONE.
SO IT SEEMS THE FUNNY, UNUSUAL CLOWNFISH
REALLY DOESN'T LIKE MOVING.
ON THE INSIDE
THEY ADAPTED THE ABILITY TO CHANGE GENDER.
IN PART, SO THEY CAN JUST STAY HOME
AND MAKE BABY CLOWNFISH.
AND ON THE OUTSIDE,
THEY'VE WORKED OUT A SWEET DEAL WITH THEIR TOUCHY LANDLORD.
JUST SO THEY CAN HAVE A LIFELONG LEASE
ON THE PERFECT PLACE.
THE SEAHORSE LOOKS ELEGANT AND GRACEFUL ON THE OUTSIDE,
BUT IT'S WHAT HAPPENING ON THE INSIDE
OF THE MALE SEAHORSE
THAT SETS IT APART FROM MANY OTHER SPECIES.
THE SEAHORSE IS SHY AND ELUSIVE.
AT HOME IN TROPICAL AND TEMPERATE COASTAL WATERS.
IT IS ALSO NOT NEW TO THIS WORLD
AS THE SEAHORSE SWAM THE OCEAN OVER 20 MILLION YEARS AGO.
BUT WHY DID THIS CURIOUS-LOOKING SPECIES EVOLVE?
AND WHAT INTERNAL ADAPTATION SETS IT APART
FROM EVERY OTHER ANIMAL ORDER IN THE WORLD?
THE ANSWER BEGINS IN THE ANCIENT OCEANS.
(♪♪♪)
SEAHORSES BELONG TO THE GENUS HIPPOCAMPUS,
WHICH LITERALLY TRANSLATES FROM THE GREEK WORDS
HORSE AND SEA MONSTER.
THEY ARE CLOSELY RELATED TO THE WEEDY SEADRAGON,
THE PIPEFISH AND THE PIPEHORSE.
ONE THEORY IS THAT THE VERTICAL SEAHORSE DIVERGED
FROM THE HORIZONTAL PIPEHORSE AROUND 25 MILLION YEARS AGO.
AT THIS TIME, TECTONIC ACTIVITY
BETWEEN THE INDIAN AND PACIFIC OCEANS
CREATED HUGE STRETCHES OF SHALLOW WATER.
SEA GRASSES GREW IN THESE SHALLOW SEAS
AND QUICKLY DIVERSIFIED.
SCIENTISTS THINK THIS NEW GRASSY HOME
RESULTED IN MANY PHYSICAL CHANGES
TO THE ANCESTRAL SEAHORSE.
THEY EVOLVED TO SWIM UPRIGHT,
BLENDING IN WITH THE SEA GRASS AROUND THEM.
THEIR SKIN COLOR ALSO EVOLVED MAKING THEM MASTERS OF MIMICRY,
ABLE TO CRYPTICALLY BLEND IN WITH THEIR SURROUNDINGS.
THEIR EYES EVOLVED TO MOVE INDEPENDENTLY OF ONE ANOTHER
IN ALL DIRECTIONS TO MAXIMIZE THEIR FIELD OF VIEW.
THEIR HORSE-SHAPED HEAD MOVED TO A 90-DEGREE ANGLE
FROM THEIR BODY, UNLIKE ANY OTHER FISH.
AND THEIR TAIL DEVELOPED
INTO A FLEXIBLE YET RELIABLE ANCHOR,
ALLOWING THEM TO CLING TO OBJECTS AROUND THEM
AND ARTICULATE ENOUGH TO UNWIND AND DETACH ITSELF QUICKLY.
BUT WHAT IS MOST FASCINATING ABOUT SEAHORSES
IS SOMETHING THAT HAPPENED INSIDE THEIR BODIES,
SPECIFICALLY IN MALES.
(♪♪♪)
MANY SEAHORSE SPECIES STUDIED IN THE WILD ARE MONOGAMOUS.
THEY MATE WITH ONLY ONE OTHER SEAHORSE
WITHIN A SINGLE BREEDING SEASON.
THE REPRODUCTIVE PROCESS BEGINS
WHEN A MALE AND A FEMALE ENGAGE IN A DAILY PRE-DAWN DANCE,
INTERWEAVING THEIR TAILS AND SWIMMING TOGETHER IN UNISON.
A TRUE COURTSHIP DANCE CAN LAST AS LONG AS EIGHT HOURS
AND IS COMPLETED WHEN THE FEMALE DEPOSITS HER EGGS
IN THE MALE'S POUCH.
HERE IS WHERE THE CHANGE-UP HAPPENS,
THE MALES CARRY THE EGGS.
THEY GET PREGNANT, NOT THE FEMALES.
SEAHORSES ARE AMONG THE FEW ANIMAL SPECIES
WHERE THIS PHENOMENON OCCURS.
&gt;&gt; NOT ONLY DO THE MALES TAKE CARE OF THE OFFSPRING,
BUT HE'S DONE SO BY EVOLVING A PARTICULAR INCUBATION POUCH
IN THE FRONT OF HIS TAIL.
THE FEMALES WILL LAY EGGS INTO HIS POUCH
AND HE WILL FERTILIZE THEM WITH HIS SPERM,
AND THEN CARRY THOSE EGGS INTO THE YOUNG LARVA,
AND INCUBATE THEM IN HIS POUCH,
VERY MUCH LIKE A FORM OF GESTATION.
MALES SEAHORSES CAREFULLY CONTROL THE POUCHES
TO ENSURE THE EMBRYOS SURVIVE.
THESE STAY-AT-HOME DADS ARE HOME IMPROVEMENT GURUS,
THEY BALANCE BLOOD FLOW, CONTROL SALT LEVELS,
AND PROVIDE OXYGEN TO THEIR UNBORN BROODS
THROUGH PLACENTA-LIKE FORMS UNTIL THEY GIVE BIRTH.
THIS GENDER BENDING ISN'T LIMITED
TO BIRTHING THE BABIES THOUGH,
STUDIES HAVE INDICATED THAT MALE PREGNANCY RESULTS
HAD A REVERSAL OF SEX-RELATED BEHAVIORS.
FEMALES EXHIBIT COMPETITIVE BEHAVIOR,
USUALLY EXHIBITED BY MALES.
AND MALES END UP BEING CHOOSY ABOUT THEIR PARTNERS,
BEHAVIOR USUALLY EXHIBITED BY FEMALES.
BUT THE QUESTION STILL REMAINS
WHY HAS THE MALE SEAHORSE EVOLVED THIS WAY?
&gt;&gt; OFTEN WITH REPRODUCTION IN FISH
WHAT WE FIND IS THERE IS A MUCH GREATER INVESTMENT
ON THE FEMALE BEHALF THAN THE MALE,
BECAUSE OF THE GREAT DEGREE OF ENERGY AND NUTRIENTS
THAT HAVE TO GO INTO THEIR LARGE EGGS
COMPARED TO A SMALL AMOUNT OF SPERM
THAT THE MALES NEED TO CONTRIBUTE
TO THE FERTILIZATION PROCESS.
ONE CONSEQUENCE OF THIS THAT WE SEE QUITE REGULARLY
IS THAT TYPICALLY IN FISH IT'S VERY COMMON FOR THE MALE
TO BE THE ONE THAT PROVIDES THE PARENTAL CARE,
RATHER THAN THE FEMALE.
&gt;&gt; IN AN EFFORT TO ALLEVIATE THE ENERGY INVESTMENT
MADE BY FEMALES,
MALE SEAHORSES MIGHT HAVE EVOLVED
TO HELP BEAR THE LOAD OF REPRODUCTION.
A PROCESS THAT TAKES ENERGY
FROM BOTH MALE AND FEMALE PARTNERS.
MALE SEAHORSES HAVE COME A LONG WAY,
IMPROVING THE IMAGE OF STAY-AT-HOME DADS.
THEY ARE TRULY A MODERN FAMILY.
CHEETAHS ARE KNOWN FOR BEING FAST,
BUT THAT SEEMS TO BE TRUE IN MORE WAYS THAN ONE.
FEMALE CHEETAHS, WELL, THEY CHEAT.
BUT WHY?
WHEN IT COMES TO MATING,
THE ANIMAL KINGDOM PROVIDES A LOT OF EXAMPLES.
MOST ANIMALS MATE WITH A PARTNER FROM THE OPPOSITE SEX
AND MANY ARE NOT EXACTLY EXCLUSIVE WITH THEIR CHOICES.
THE QUEST TO MAKE THE BEST BABIES
LEADS SOME ANIMALS TO PLAY THE FIELD.
FOR EXAMPLE, THE FEMALE CHEETAH REALLY IS A CHEATER.
IN SCIENTIFIC TERMS,
SHE'S WHAT'S KNOWN AS POLYANDROUS.
&gt;&gt; POLYANDRY IS ONE OF THE MATING SYSTEMS
THAT IS EXHIBITED BY MANY ANIMAL GROUPS.
IT HAS TO DO WITH FEMALES MATING WITH MULTIPLE MATES
DURING ONE BREEDING PERIOD AS OPPOSED TO A FEMALE
BEING PAIR-BONDED WITH A SINGLE MATE.
IN POLYANDROUS MATING SYSTEMS,
FEMALES HAVE SPERM FROM MULTIPLE MALES
WHICH MEANS THAT THE BROOD OF YOUNG THAT THEY PRODUCE
WILL HAVE DIFFERENT DADDIES.
&gt;&gt; FEMALE INSECTS ARE PARTICULARLY PROMISCUOUS.
WHILE ONLY 2% OF BIRD SPECIES HAVE FEMALES WHO PLAY THE FIELD.
WHAT EVOLUTIONARY FORCE PUSHES ONE FEMALE
TO MATE WITH MORE THAN ONE MALE?
A RECENT STUDY HAS LOOKED AT A WILD CAT
TO LEARN ABOUT CATTING AROUND.
FEMALE CHEETAHS IN THE SERENGETI NATIONAL PARK OF TANZANIA
HAVE PROVEN TO BE POLYANDROUS.
IN THIS STUDY, MANY SINGLE LITTERS
WERE FATHERED BY SEVERAL DIFFERENT MALES,
MAKING MANY OF THE CUBS WITHIN THE SAME LITTER
ONLY HALF SIBLINGS.
AS CHEETAHS ARE RARELY OBSERVED MATING IN THE WILD,
THE PROOF WAS IN THEIR POOP.
SCIENTISTS STUDIED THE FECAL MATTER OF CHEETAHS
TO ANALYZE THE DNA OF MOTHERS, FATHERS, AND CUBS.
BUT WHY HAVE FEMALE CHEETAHS EVOLVED TO PLAY THE FIELD
IN THE FIRST PLACE?
EXPERTS LOOK TO MALE CHEETAHS FOR CLUES.
&gt;&gt; CHEETAHS FORM BROTHER COALITIONS
AND IT'S A VERY EXCITING BEHAVIORAL SITUATION
IN AN OTHERWISE SOLITARY SPECIES.
THEY'LL DEFEND A TERRITORY TOGETHER,
THEY'LL HUNT TOGETHER,
THEY'LL SEARCH FOR MATES TOGETHER.
BROTHER CHEETAHS WILL STAY TOGETHER
FOR THEIR ENTIRE LIFE.
&gt;&gt; LONG-TERM MALE COALITIONS ARE UNUSUAL IN MAMMALS.
IN THE CASE OF CHEETAHS,
THESE PAIR GROUPS ARE ALSO NOT ALWAYS AMONG BROTHERS.
EVEN UNRELATED MALES HAVE BEEN KNOWN
TO HAVE A BROMANCE.
THIS IS BECAUSE INTENSE COMPETITION
FOR TERRITORY AND MATES MEANS MALES HAVE A BETTER CHANCE
AT GETTING ACCESS TO FEMALES IF THEY BAND TOGETHER.
ONCE IN FEMALE TERRITORY,
MALES HAVE A SCHOOLYARD WAY OF FLIRTING.
THEY MANIPULATE FEMALES INTO MATING BY HARASSING THEM.
(♪♪♪)
BUT SEXUAL CONFLICT THEORY EXPLAINS
THAT IF MALE HARASSMENT COMPROMISES FEMALE FITNESS,
THEN FEMALES SHOULD EVOLVE WAYS TO SHUT THEM DOWN AND MOVE ON.
THIS IS WHERE POLYANDRY COMES INTO PLAY.
SCIENTISTS THINK IT EVOLVED TO PROTECT FEMALES
AND ENSURE THE SURVIVAL OF THEIR OFFSPRING.
DIFFERENT THEORIES ON THIS PHENOMENON
HAVE COME ABOUT SINCE ITS DISCOVERY.
&gt;&gt; ONE IS FEMALES WOULD BENEFIT GENETICALLY
FROM MATING WITH DIFFERENT MALES.
SO THE GENETIC BENEFITS
COULD INCLUDE FERTILITY INSURANCE.
SO IF A FEMALE WERE TO MATE WITH A SINGLE MATE,
THE SPERM OF THAT MALE MAY NOT BE VERY VIABLE.
SO SHE WOULD WASTE THAT TIME AND ENERGY
AND PERHAPS EVEN WASTE EGGS BY MATING WITH A BUM MALE.
WHEREAS, IF SHE WERE TO MATE WITH MULTIPLE MALES,
THAT INCREASES THE CHANCES
THAT HER EGGS WILL BE MAXIMALLY FERTILIZED.
&gt;&gt; ANOTHER HYPOTHESIS IS THE GOOD GENE THEORY.
HAVING MULTIPLE PARTNERS GIVES THE FEMALE CHEETAH
THE OPPORTUNITY TO MATE UPWARDS,
MATING WITH THE BEST MALES OF THE HIGHEST GENETIC QUALITY.
YET ANOTHER THEORY
IS THAT FEMALE CHEETAHS CHEAT TO PREVENT INFANTICIDE,
A COMMON PHENOMENON IN OTHER BIG CATS.
&gt;&gt; SO IF A FEMALE MATES WITH MULTIPLE MALES,
THEN THAT COULD CREATE A CONFUSION OVER PATERNITY
MEANING THAT EACH MALE THINKS
THAT THE OFFSPRING MIGHT BE THEIR OWN
THAT WOULD CAUSE A DECREASE IN THE INCIDENCE OF INFANTICIDE,
BECAUSE THEY HAVE THE INCENTIVE TO PROTECT OFFSPRING
THAT THEY THINK ARE THEIRS.
&gt;&gt; BUT ONE OF THE MOST CONVINCING THEORIES LIES
IN ENSURING GENETIC VARIATION BY MATING WITH MULTIPLE MALES.
AS LITTERS BECOME EQUIPPED WITH MORE DIVERSE GENE POOLS,
POLYANDRY HELPS PROTECT THE BROOD
FROM BEING WIPED OUT BY A SINGLE DISEASE.
&gt;&gt; BY MATING WITH MULTIPLE MALES
HER BROOD IS MORE GENETICALLY DIVERSE.
THEY HAVE GENES FROM DIFFERENT MALES,
WHICH MAY BENEFIT HER BROOD OVERALL,
ESPECIALLY IN A VERY VARIABLE ENVIRONMENT.
SO THAT THE YOUNG THEN,
AT LEAST A FEW OF THEM WOULD SURVIVE,
WHICH OTHERWISE THEY MAY ALL DIE
IF THEY WERE MORE GENETICALLY INGENIOUS.
&gt;&gt; SCIENTISTS IN TANZANIA ALSO FOUND
THAT FEMALES SEEM TO MATE WITH MALES FROM FAR FLUNG REGIONS,
GUYS FROM THE OTHER SIDE OF THE TRACKS
AS THIS EXPANDS THE GENE POOL.
FEMALE CHEETAHS DON'T RETURN TO THE SAME MALES
YEAR AFTER YEAR.
CONSECUTIVE LITTERS FROM THE SAME MOTHER IN THE STUDY
ALL HAD DIFFERENT SETS OF DADDIES.
IN AN UNPREDICTABLE ENVIRONMENT LIKE THE SERENGETI,
HAVING CHILDREN WITH DIVERSE GENES
WOULD INCREASE A FEMALE'S LIKELIHOOD
OF PASSING ON HER OWN GENES.
GENETIC DIVERSITY IS ALSO VITAL IN A SPECIES
WHERE POPULATIONS ARE RAPIDLY DECLINING.
THERE IS ONLY A TINY POPULATION REMAINING IN THE MIDDLE EAST.
AS POPULATIONS BECOME SMALLER AND MORE ISOLATED
DIVERSITY BECOMES EVEN MORE IMPORTANT
FOR THIS SPECIES SURVIVAL.
WITH HER CUBS ARMED AGAINST DISEASE AND INFANTICIDE,
THE MOTHER CONTINUES HER SEARCH FOR THE BEST MALE MATES.
FOR CHEETAHS, IT PAYS TO SHOP AROUND.
MANY ANIMALS ARE IMPRESSIVE ON THE OUTSIDE
WITH STRIKING SKIN PATTERNS,
CARTOON-LIKE COLORS,
MINIATURE FIGURINE FEATURES,
AND BEAUTIFUL FUR THAT SUPPORTS A KILLER LOOK.
BUT BEAUTY IS ON THE INSIDE TOO.
AND THESE ANIMALS ARE BEAUTIFULLY ADAPTED
TO SURVIVE.
(♪♪♪)