From the fly to the whale, the speed is a matter of size

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    Monday, 17 July 2017 12:02

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    Monday, 17 July 2017 12:02

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    They swim, they run, or they fly, the speed of animals depends on their size, but the strongest are not the fastest, according to a study published Monday in Nature Ecology & Evolution.

    “Our model can determine the maximum speeds of the animals with an accuracy of nearly 90%,” explains Myriam Hirt of the German research Centre for integrative biodiversity (iDiv) in Leipzig. It is based only on the size of the animals.

    On earth, cheetahs are the world champions. The marlins, fish of the warm seas, split the waters like no other species. Hawks and buzzards fly at 140km/h … Nevertheless, these animals do not have the muscles, the more robust the animal kingdom in their category.

    “While in theory the larger animals could be the fastest, the energy and the time necessary for their big body provides an acceleration in the hamper,” explains the researcher.

    Because, according to the study, the maximum speed of an animal depends on its ability to increase its speed as quickly as possible. And the acceleration is not the prerogative of the big guys even if they are muscular.

    Moving quickly requires a lot of energy in a short time. In addition, the sprint is anaerobic, that is to say, only from sugars stored in the body, without the energy intake of oxygen. Energy is quickly exhausted.

    According to the model, the researchers have tested on 474 different animal species – a gain of size goes hand in hand with a larger rate for smaller animals, but beyond a certain size, the curve inverts and more animals are growing in volume the more they lose in speed.

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    “If the progression was linear, the elephant is moving at 600 km/h (so that they cannot actually run at only about 34 km/h)”, has fun the researcher.

    One of the big surprises of their discovery, is that the same model applies to all animals, the fly in the shark, passing by mammals and birds.

    The researchers have taken the opportunity to go further and have applied their model to be of extinct species, like dinosaurs for example. “The model predicts maximum speeds rather low for the large dinosaurs such as T. Rex, and even more reduced for the gigantic Triceratops,” says Myriam Hirt. The results, which confirm previous work on the dinosaurs.

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