Zoologger is our weekly pillar highlighting extraordinary animals – and also occasionally other organisms – from approximately the world

by Andy Coghlan

The world’s just pentapedal animal

Species: Macropus rufusHabitat: arid grasslands pretty much all over in Australia

One the the world’s ideal loved and iconic animals has been keeping a secret. It turns out kangaroos may be the world’s only “pentapedal” animals, properly having 5 legs.

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Before you start taking a near look in ~ stills that Skippy the shrub kangaroo, it’s no a secret limb – the 5th “leg” is the animal’s tail. Uneven the tails of various other animals, the kangaroo’s tail functions as a leg, pushing it forward together it walks.


The kangaroos in question are red kangaroos, which are the biggest living marsupials. And their renowned hopping gait, they have actually a hold of other tricks up your sleeves.

For instance, females that loss pregnant while castle still have a young joey in your pouch have the right to halt the embryo’s breakthrough until the joey leaves, which can be 235 job later. They likewise use very tiny energy and also water contrasted with comparable grazing animals like sheep.

Powerful tail

And then there’s the tails. “Animals have actually discovered plenty of uses for your tails but, as much as we know, this is the first use the one as a leg,” states Max Donelan of Simon Fraser university in Burnaby, Canada.

Donelan and also his partner trained five red kangaroos come walk with a chamber led with force plates, which measured the downward forces exerted through the animals as they moved. By combine this with video clip footage, the team calculated how much job-related each body did throughout a walking cycle.

To walk, kangaroos very first lean forward and also plant your forelimbs ~ above the ground. Following they lug forward their bigger hindlimbs, prior to releasing your forelimbs from the ground. It is at this allude that their tail comes into play. Cut up and also in call with the ground, it flexes forward versus the ground and straightens, lifting and speeding up the animal forward. This method the former limbs deserve to make ground call again for the begin of the following cycle (see video).

Donelan found that the propulsive force from the tail was as huge as the from the other limbs combined. “They execute as much mechanical work-related with their tail together we carry out with one of our legs once we walk,” states Donelan.

Not just a crutch

That is a surprise. “The tail is anatomically quite different from person legs,” states Donelan. That is made up of an ext than 20 vertebrae, rather than a few leg bones. It also evolved come swing top top branches fairly than push on the ground, the says.

But in retrospect, there to be clues. The tail muscle are larger than those the the prior limbs. Castle are additionally rich in mitochondria, the power powerhouses the cells.

Most scientists had actually assumed kangaroos only provided their tails for relaxing on and balance, nearly like a crutch, states Donelan. “This is indeed one the its roles, but we also discovered that it was being used to propel and also power motion.” It also serves together a prop to prevent the animal falling backwards as soon as the hind legs room lifted.

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Other big kangaroos, such as the two varieties of grey kangaroo, are probably additionally pentapedal, says Donelan. Yet he says the smaller wallabies most likely aren’t, together they show up to drag their tails. It’s likewise unlikely any type of other animals, either living or extinct, go with five legs. Donelan claims there are numerous fossilised footprints, and also none present signs of a pentapedal gait.