A team of scientists claims to have unraveled one of the animal kingdom's more peculiar mysteries: why wombat poop is cube-shaped.
The wombat, native to Australia, produces about 80 to 100 cubes of poop each night. It is known to deposit piles of dung outside burrows and on top of rocks and logs, most likely to communicate with other wombats, researchers believe.
"Wombats have really strong sense of smell that they use probably for communication," said University of Tasmania wildlife ecologist Scott Carver, who co-authored the study. "We don't know what that information they're sharing is, but it might be something about mating, it might be something about general advertising about who's in the area."
It is thought that the cubed shape of the poop means it is less likely that it will roll away, and is prominent for other individuals to notice and smell, Carver added.
But how the wombat produces the cubed shapes is a phenomenon that has puzzled many observers of the furry marsupial.
Researchers, led by the Georgia Institute of Technology's Patricia Yang, said they have uncovered the digestive processes behind the mystery and presented their findings at the 71st Annual Meeting of the American Physical Society's Division of Fluid Dynamics in Atlanta on Sunday.
The wombat's cubed faeces is a trait that's unique in the animal world, the researchers said, as cubes are usually created by cutting or molding.
"In the built world, cubic structures are created by extrusion or injection molding, but there are few examples of this feat in nature," authors of the project said in the study's abstract.
To solve the puzzle, the team examined the digestive tracts of wombats that had to be euthanized following vehicle collisions in Tasmania, Australia.
The wombat takes about two weeks to digest its food and researchers found that as faeces move into the final 8% of the intestine, it changes from a liquid-like state into solid matter. At that stage the dung takes on the shape of separated cubes measuring about two centimeters in length.
"The weird thing is that if you open up a wombat you actually find that the cubes become formed in the lower part of the intestine, before they exit the body," Carver said.
By inflating the intestine with a long balloon, the researchers found that the wombats' intestine walls stretch unevenly, allowing for the formation of the cube shapes.
"The local strain varies from 20% at the cube's corners to 75% at its edges," the team said.
"Basically around the circumference [of the intestine], there are some parts that are more stretchy and some parts that are more stiff," Carver said. "And that is what creates the edges and the cubing."
The study's authors said the findings could have implications beyond the natural world, by helping to provide insight into new manufacturing techniques.
"There is a long history of people looking to the natural world for innovations in human society," Carver said. "This potentially reveals another mechanism of producing cubed-shaped objects and in that sense it could contribute to thinking about manufacturing these sorts of objects in different ways."