Mystery solved: this is how wombats do cube-shaped poo

By Australian Geographic 19 November 2018
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A great Australian mystery has been put to rest.

ONE OF AUSTRALIA’S most beloved animals, the wombat, has been at the centre of a great biological mystery: no one could quite work out how their poo becomes cube-shaped.

That was until now. Researchers from the Georgia Institute of Technology in the United States have uncovered the digestive processes they believe gives wombat poo its shape – and the findings may transform the way cube-shaped items are manufactured in the future.

Previously, researchers assumed wombats’ cube-shaped poo had something to do with the animals’ intestines, not their rectum (as had been wrongly assumed for years), and now they have evidence to back that up.

Postdoctoral fellow in mechanical engineering, Patricia Yang and her co-authors were determined to solve the mystery, and explain the mechanism behind the cube-shaped poo, which Patricia initially believed was some sort of joke.

“I have never seen anything this weird in biology,” she said. “I didn’t even believe it was true at the beginning. I Googled it and saw a lot about cube-shaped wombat poo, but I was skeptical.”

The team of researchers studied the digestive tracts of wombat roadkill sourced from Tasmania, as well as donated intestines from their Australian counterparts at the University of Tasmania.

By emptying the intestines and inflating them with long balloons, they revealed that the intestine stretches ‘preferentially’ at the walls, meaning the elastic properties within the intestinal walls were responsible for the shape.

Wombats are the only known animals to produce cube-shaped poo, and the researchers hope that a better understanding of this method will help in the manufacturing of goods – from confectionary to construction.

“We currently have only two methods to manufacture cubes: We mold it, or we cut it. Now we have this third method,” Yang said. “It would be a cool method to apply to the manufacturing process – how to make a cube with soft tissue instead of just molding it.”

In the wild, a wombat’s cubed poo helps them mark their territory: often bundles of it can be seen close to their burrows, but a wombat also wants a strong scent that will capture the attention of potential mates.

This November, Yang and her team will discuss their findings at the American Physical Society’s Division of Fluid Dynamics 71st Annual Meeting in Atlanta.