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Why Don't Blue Whales Eat Fish? - Video học tiếng Anh

Why Don't Blue Whales Eat Fish?

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0:00The most massive land animals in the

0:01world all eat little stuff, grass and

0:04leaves. And almost all of the most

0:06massive aquatic animals also eat

0:08something itty bitty. Tiny crustaceans

0:10called krill. Why do such big things eat

0:12such small things? Hi, I'm David and

0:15this is Minute Earth. The most ginormous

0:17animals all need to eat a huge amount of

0:19calories to fuel their massive bodies,

0:21but there aren't enough big super

0:22calorie dense meals around for them to

0:24eat. And even if there were, the giant's

0:26massive bodies aren't mobile or agile

0:28enough to actually capture that food.

0:30Instead, these mega creatures meet their

0:32mega calorie quota with something that's

0:33super abundant and requires almost no

0:35effort to procure. Little pieces of

0:37grass and leaves. And for our purposes,

0:39we're going to consider leaves to be

0:40little, even if they do come off of

0:42bigger things. And sure, leaves and

0:44grass aren't very calorie dense compared

0:46to things other animals eat, but the

0:47giant's giant digestive tracts can hold

0:49a lot of them at once. We're talking

0:51hundreds of kg. Plus, the bigger an

0:54animal is, the longer the food stays in

0:55its digestive system, and the more

0:57microbes there are in there to break it

0:58down. All of that means that the giants

1:00are able to ring a lot of calories from

1:02grass and leaves, enough to meet their

1:04huge calorie demands. The abundance and

1:06ease of finding leaves and grass and the

1:08specialized digestive systems to deal

1:09with large quantities of them are why,

1:11at least on land, you see the same

1:13pattern in every biome. The very biggest

1:15animals are herbivores. Even back in the

1:17day when dinosaurs roamed the earth, the

1:19biggest animals weren't predators like

1:20T-Rexes. They were lumbering, leap

1:22eatating vegetarians. But what about the

1:24ocean? Like their counterparts on land,

1:26sea giants like blue whales are

1:28relatively unaggile and have giant guts.

1:30So it makes sense that they'd eat the

1:32ocean equivalent of grass. Huge blooms

1:34of tiny plant-like microorganisms called

1:36phytolankton. But these ocean behemoths

1:38need so many calories every day that

1:40phytolants, even lots and lots and lots

1:42of them, just aren't calorie dense

1:44enough to meet the demand. Luckily,

1:46those big phytolankton blooms attract

1:48something else. Billions of

1:49caloriepacked krill that come together

1:51to graze in huge slowmoving easy to find

1:53swarms. A blue whale that lunges back

1:55and forth through a swarm can easily

1:57take in more than enough calories to

1:59power its huge body. The equivalent on

2:01land would be if there were huge

2:02slowmoving swarms of grasshoppers that

2:04elephants could munch on instead of the

2:05grass itself. In that case, the

2:07packaderms could pack in even more

2:09calories and likely get even bigger.

2:10Either way though, the same truth holds

2:13for the biggest animals on Earth. It

2:14turns out food things come in small

2:17packages.