Researchers at the University of New South Wales have determined that kangaroo's tail is used as a fifth leg and is a lot more important than previously believed.

Previous studies showed that a kangaroo's tail serves as a springboard and counter balance when hopping, storing up energy and helping the marsupial transition from bounce to bounce.

Now researchers have determined that its tail is more important than its smaller forelegs, according to a recent study.

Researchers analyzed the mechanics of a kangaroo's stride by training a number of specimens, both male and female, to saunter across a platform that measures pressure. It was during these tests that they determined the tail was just as important as the two hind legs.

"We expected this is because the muscles in the tail and hind legs are highly aerobic, with a lot of mitochondria in them doing a lot of work," said lead researcher Terry Dawson, according to ABC Science.

Mitochondria is a part of the cell that provides energy.

The study published this week in the journal Royal Society Biology Letters. The researchers were the first to show important the tail is to a kangaroo's movement through conclusive evidence.

"The muscle structure of the front legs have little mitochondria and they're not organized for propulsion, so instead of the tail being the strut, the front legs were filling that role," added Dawson. "I can now understand where that energy goes and why if they're going to walk more than five meters they get up and hop instead."

Dawson added that the study confirmed that the researchers expected. Kangaroos become five-legged animals "when they're using their tail."

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