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  • Pretty much everyone over the age of four has heard that cheetahs are the fastest land animal.

  • These long, lean cats can accelerate from zero to 72 kilometers per hour in 2.5 seconds,

  • which is ridiculously fast. Faster than a lot of cars.

  • But if you stop to think about it, it kind of seems like a /bigger/ animal ought to hold

  • the land speed title.

  • Pit a T. rex against a cheetah, and wouldn't the T. rex leave the cheetah in the dust?

  • The T. rex had longer legs and more muscles than a cheetah, so it seems like the cheetah

  • would lose the race /and/ get devoured at the finish line.

  • But alas, T. rex was probably as useless as a sprinter as it was at playing piano

  • with those tiny little arms.

  • And that has to do with the way muscles work.

  • Skeletal muscles are made of bundles of fibers, and those fibers come in two kinds: slow twitch and fast twitch.

  • Slow twitch muscle fibers contract slowly, and are used by the body for activities that require endurance.

  • Fast twitch muscle fibers contract more quickly, and are good for rapid actions like jumping or sprinting.

  • Slow twitch muscle fibers can keep doing their thing for a long period of time, while fast

  • twitch muscle fibers tend to get fatigued pretty quickly and use up a lot of energy.

  • Big animals have more muscle mass, and therefore more fast twitch fibers.

  • So logically, big animals /should/ be faster than smaller animals, but there's a catch.

  • The fast twitch muscles of larger animals run out of fuel a lot more quickly than

  • muscles of smaller animals.

  • Because their mass makes them heavier, it takes longer for a large animal to accelerate.

  • So some biologists think large animals are simply incapable of reaching their potential

  • top speed -- because they use up all their fuel before they can get there.

  • So in terms of speed, it's not the big animals that rule, and it's not the small ones,

  • it's the medium-sized ones.

  • In fact, in 2017 researchers hoping to answer this question published a model for predicting

  • maximum speed in the journal Nature Ecology & Evolution.

  • The model uses body size alone to make predictions about animal speed, and it's accurate not

  • just for land animals, but for birds, insects, and fish too.

  • They developed this maximum speed model to answer questions about why there seemed to

  • be an upper limit to animal movement, and what the consequences of those limits were

  • for individual species.

  • In other words, the model can help us understand more about why some animals traded speed for size, and vice versa.

  • The relationship between size and speed was so robust, they can even use it to predict the

  • speed of /extinct/ species, even though we'll never see them in motion.

  • Like Velociraptor, which it predicts would have been roughly twice as fast as T. rex.

  • Cheetahs are the clear winners of the modern land speed game, even though they are roughly

  • the same size as some other slower animals, like the leopard.

  • The difference between cheetahs and their slower cousins can be found in certain physical

  • characteristics that give them an edge.

  • For example, the cheetah's spine is longer and more flexible than the leopard's — or

  • any cat specieswhich lets it maximize the length of its stride.

  • Other physical characteristics, like paw pads that provide traction, a large heart, liver,

  • and adrenal gland, an aerodynamic body, and swiveling hips give it the edge it needs to

  • claim thefastest land animaltitle.

  • So a cheetah could definitely outrun a T. rex, but take heart.

  • If you put the two species together in an ultimate fighting ring, the T. rex would win every time.

  • Just as long as it doesn't have to outrun anyone. Or play the piano.

  • Thanks for asking, and thanks to our patrons for bringing you this answer.

  • We are so grateful to have the coolest community of supporters out there.

  • If you'd like to join them, check out patreon.com/scishow.

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Why Are Cheetahs the Fastest Land Animal?

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    joey joey に公開 2021 年 05 月 13 日
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