Bigger isn’t always better — or faster

Cheetahs are the fastest land animal in the world, and can reach speed of up to 112 kilometres per hour. Image: Villiers Steyn/Shutterstock

Lizard study reveals why cheetahs are the world’s fastest animal.

Physiologists at Harvard University studying lizard locomotion have found that running speed peaks in midsize animals, whose bodies hit a “˜sweet spot’ of long legs and low body mass. The cheetah is an almost perfect blend of those two characteristics, and as a result is capable of running at 112 kilometres per hour.

“Typically, bigger animals tend to run faster than smaller animals, because they have longer legs,” said Christofer Clemente of Harvard University’s Propulsion Physiology Lab, who led the research. “But this only works up to a point. The fastest land animal is neither the biggest nor the smallest, but something in between. Think about the size of an elephant, a mouse and a cheetah.”

Clemente’s team studied monitor lizards, which can vary in size as adults, ranging from one to five kilograms.  Testing within a single species helped control for other variables, such as evolutionary adaptations that might make one species purposefully slower than it’s maximum speed, allowing researchers to compare running speed and body size explicitly. Using high-speed cameras, they measured how quickly a lizard crossed a 13.7 metre track. Each lizard had markers on important parts of their body, and by importing the data into a computer, the team could model the lizard’s movement.

They found that medium-sized lizards were the fastest of the lizards tested. “Larger lizards’ legs can no longer support their body weight, and they have to change their style of running, making them slower,” Clemente said in Science Daily. The study suggests that bone and muscles may not be able to support fast speeds on more massive lizards.

In the video, computer capture of a monitor lizard’s running stride.

Source: Science Daily


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