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  • Blue whales are the largest animals

  • that have ever roamed the planet.

  • They're at least two times as big as the biggest dinosaurs,

  • "That's big!"

  • the length of a basketball court,

  • and as heavy as 40 African elephants.

  • If that's not enough to make you marvel,

  • here's something that will.

  • They're grown to this enormous size

  • by feeding exclusively on tiny shrimp-like creatures called krill

  • that are no bigger than your little finger.

  • In many ways, the sheer size of krill

  • seems to have driven the evolution of the blue whale.

  • See, krill are so small

  • but are found in dense patches.

  • For increased efficiency,

  • blue whales have evolved

  • to use a feeding strategy

  • called lunge feeding.

  • Basically, the whale accelerates towards a prey patch

  • and opens its mouth wide.

  • To increase the capacity, its mouth expands.

  • The special, accordion-like blubber layer

  • that extends from its snout to its belly button

  • enables the whale to engulf large quantities

  • of prey-laden water.

  • With each giant gulp,

  • the whale takes in 125% of its body weight

  • in water and krill.

  • The whale must then expel the water

  • while retaining the yummy krill.

  • To do this, it uses its baleen,

  • the comb-like structure made of the same stuff

  • our nails and hair are made of,

  • and its tongue.

  • It's pretty crazy that the blue whale's heart

  • is as big as a small car,

  • a child could crawl through its arteries,

  • its tongue weighs as much as an elephant,

  • but its esophagus is so small,

  • the whale could choke on a loaf of bread.

  • These whales are really not designed

  • to feed on anything larger than krill.

  • It's estimated that blue whales eat four tons of krill per day.

  • Because of the incredible design,

  • each dive provides the blue whale

  • with 90 times as much energy as is used.

  • Every mouthful of krill provides almost 480,000 calories,

  • the same amount you get from eating 1,900 hamburgers.

  • But, why are blue whales so big?

  • Blue whales are considerably larger

  • than the largest living land animal, the elephant.

  • The heavier an animal is,

  • the greater its relative surface area.

  • As weight increases,

  • there's a point at which the legs of that animal

  • would simply collapse.

  • That explains why elephants don't stand

  • on the delicate legs of a horse.

  • They need legs shaped like stout pedestals

  • to hold their bodies up against gravity.

  • In water, the situation is quite different.

  • Buoyancy counteracts the gravitational pull on the body

  • and their great bulk is therefore partially supported

  • by the water.

  • So, the ocean is a great place for species

  • that want to grow bigger.

  • The other secret to their size is their diet.

  • By evolving such a huge mouth,

  • the whale's have specialized to catch enormous quantities

  • of highly abundant and nutritious prey,

  • which provides the energy needed to grow so big.

  • But, now maybe you're wondering

  • why blue whales aren't any bigger?

  • After all, the ocean sounds like nirvana

  • for any growing beast.

  • Well, while lunge feeding may have allowed blue whales

  • to become the biggest animal

  • to have ever roamed the planet,

  • by enabling them to feed efficiently in dense prey patches,

  • it isn't cost free.

  • Scientists compared all the costs involved with lunge feeding

  • to the energy gained from the krill they eat.

  • What they found is that when the whale's body increases in size,

  • the energy that body demands rises faster

  • than the extra energy they get from their food.

  • Feeding whales needs 15 times the energy required to remain still

  • and 5 times more energy than used when swimming.

  • Calculations show

  • that the largest a lunge feeder can grow is 33 meters,

  • pretty much blue whale size.

  • Turns out blue whales have a lot to thank krill for:

  • neat, evolutionary adaptations

  • that would not have been possible if krill were not so small.

  • It's incredible that these tiny creatures

  • have allowed blue whales to really push the limits

  • of size on our planet.

  • Makes you wonder if that old adage,

  • "You are what you eat,"

  • really does apply in blue whale world.

Blue whales are the largest animals

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B1 TED-Ed krill whale blue whale feeding lunge

【TED-Ed】Why are blue whales so enormous? - Asha de Vos

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    VoiceTube posted on 2013/09/02
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