Kangaroos may be nature's most elegant hoppers, but their walk is anything but graceful.

When foraging for food, these usually majestic creatures look ungainly and awkward as they attempt to balance their heavy bodies.

But now researchers have discovered that appearances may be deceiving, and there cumbersome movements are in fact helped by a fifth ‘limb’; their tails.

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Scientists from Colorado, Sydney and Burnaby in Canada discovered that a red kangaroo’s tail provide as much driving force as their front and hind legs combined. Pictured is the tail skeletal structures with corresponding photo of a red kangaroo

Scientists from Colorado, Sydney and Burnaby in Canada discovered that a kangaroo’s tail provide as much driving force as their front and hind legs combined.

'We found that when a kangaroo is walking, it uses its tail just like a leg,' said Associate Professor Maxwell Donelan of Simon Fraser University in in Burnaby, Canada.

‘They use it to support, propel and power their motion. In fact, they perform as much mechanical work with their tails as we do with one of our legs.'

The researchers began the study thinking the tail was mainly used like a strut, a balancing pole, or a one-legged milking stool.

Red kangaroos are the largest of the kangaroo species in Australia. When grazing on grass, they move both hind feet forward 'paired limb' style while using their tails and front limbs together to support their bodies

'What we didn't expect to find was how much power the tails of the kangaroos were producing. It was pretty darn surprising,’ said Associate Professor Rodger Kram at the University of Colorado Boulder.

Red kangaroos are the largest of the kangaroo species in Australia.

THE RED KANGAROO: KEY FACTS Red kangaroos are the largest of the kangaroo species in Australia. Their legs work much like a rubber band. The males can leap over 30 ft (9 metres) in one leap. This species is a very large kangaroo with long, pointed ears and a squared-off muzzle. The creatures primarily eat green vegetation, particularly fresh grass, which makes up 75 per cent to 95 per cent of their diet. When grazing on grass, they move both hind feet forward 'paired limb' style while using their tails and front limbs together to support their bodies. A red kangaroo can increase its metabolism by 50 times during exercise. A kangaroo’s tail provide as much driving force as their front and hind legs combined. The kangaroo tail also boosts balance when male kangaroos grab each other by the chests or shoulders to assert dominance. Advertisement

When grazing on grass, they move both hind feet forward 'paired limb' style while using their tails and front limbs together to support their bodies.

'They appear to be awkward and ungainly walkers when one watches them moseying around in their mobs looking for something to eat,' said Professor Kram.

'But it turns out it is not really that awkward, just weird.'

In human movement, the back foot acts as the gas pedal and the front foot acts as a brake, which is not especially efficient, said Professor Kram.

Professor Donelan said no animal other than the kangaroo uses its tail like a leg. ‘Their tails have more than 20 vertebrae, taking on the role of our foot, calf, and thigh bones.'

The research project had its beginnings in 1973 when a Harvard Professor Richard Taylor coaxed a small group of kangaroos to hop and walk on a large motorised treadmill, with a goal of measuring the energy costs of locomotion at varying speeds.

This study showed that a kangaroo can increase its metabolism by 50 times during exercise.

The kangaroo tail also boosts balance when male kangaroos grab each other by the chests or shoulders, then rear back and kick each other in the stomach in an attempt to assert dominance for the purpose of reproduction.

Professor Donelan said no animal other than the kangaroo uses its tail like a leg. ‘Their tails have more than 20 vertebrae, taking on the role of our foot, calf, and thigh bones,' he said

For the study the team videotaped five red kangaroos in Dawson's Sydney lab that had been trained to walk forward on a force-measuring platform with Plexiglas sides.

The platform's sensors measured vertical, backward and forward forces from the legs and tails of the animals.

The kangaroos had been taught that walking forward on the platform resulted in being rewarded with sweet treats.

‘This was a study we just could not let go of,' said Professor Kram. 'It was just too much fun. It's a real wonder of nature, how these kangaroos move about and what they are able to do.'

He likens the evolution of the kangaroo tail to a roll of duct tape in the back of a truck. 'You know you are going to use it, you just don't know when,' he said.

'I'm envious of kangaroos,' said Professor Kram, a competitive master runner in the mile and 1,500 metres.

'When they hop faster, they don't use energy at a faster rate. The have the ability to move faster and not get tired, the ultimate goal of a runner.’