Five-legged Kangaroo?

Kangaroos are known for their hopping; big hind legs, tail stretched out, bounding along.
In fact, a classic study showed that the faster they hop the less energy they use, up to a point.
But what happens when they need to move along slowly munching on grass, walking?
Obviously, they do kind of lean on their tail to support their body but when scientists from several universities trained kangaroos to walk on a measuring device called a force plate, what they found was that the tail was doing a lot more than anyone had realized.
It exerted as much force as the four other legs combined.
By a measure commonly used in physics called mechanical work, the kangaroo’s tail is as important when it walks as one of our legs is when we walk.
It makes you think what makes a leg a leg. If the role it plays in walking is the key, then the kangaroo has five.
Source: nytimes

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