Who knew that a “crouching tiger” is not supposed to crouch? Huge tigers walk, crouch, and leap the same way house cats do, and pretty much all other cats of different sizes do. But that is a mystery to scientists, because it’s unique in the animal kingdom. It’s a matter of physics.
Today, cats span a huge range of sizes. The rusty-spotted cat of India and Sri Lanka weighs just one kilogram, while the mighty Siberian tiger is 300 times heavier. And yet, these animals are surprisingly similar. “It's famously said that a lion is just a scaled-up house cat,” says Anjali Goswami from University College London, who works with Hutchinson. “That's very weird.”
Their legs are especially odd. When animals get bigger, their posture changes. Their legs tend to straighten, becoming stiffer and more pillar-like to better support their weight. Not so with cats. When a lion strides across the savannah, it has essentially the same posture as the domesticated tabby that slinks over your lap. Lions, tigers, and leopards—oh my—are, as Hutchinson writes, the only large, crouching mammals.
How do those large cats do it? They don’t have larger muscles to compensate. Scientists have designed experiments to learn more about the physics of big cat legs, but they don’t have any results yet. Oh, it’s not for lack of trying, but another way big cats are like small cats is that they don’t want to cooperate with scientists or anyone. Read about the so-far futile efforts involved in getting cats to measure leg force at the Atlantic.
(Image credit: Dave Pape)