Kangaroo’s tail is really a fifth limb

Science : A kangaroo’s tail works as hard to propel the animal forward as all four of its legs combined, according to a recent study published in Biology Letters. Max Donelan of Simon Fraser University in Burnaby, British Columbia, Canada, and colleagues studied five red kangaroos (Macropus rufus) as they walked. The movement of kangaroos has been called pentapedal, or five-footed, because of the way they place their tail on the ground in time with their front legs as they bring their hind legs forward. Through the use of video recordings and force measurements taken from a special plate installed in the laboratory floor, the researchers were able to determine that a kangaroo’s tail not only acts as a support, which had been believed to be its chief function, but also propels and powers the animal forward much like a human leg does. That is because the tail actually has larger muscles than the forelimbs. The researchers propose that it may be this unique combination of shortened forelimbs and more muscular tail that allows the animals to reach speeds of up to 60 km/hour.