Why Wombats Make Cube-Shaped Poos

New research shows differences in elasticity in the intestines shapes the poo as it moves through

Wikimedia Commons

As the children’s book Everyone Poos has taught us, creatures of all shapes and sizes create an array of poops, and they are all natural and okay. Well, maybe except for the wombat’s poop; something weird is going on there. The Australian marsupial pushes out little piles of cube-shaped poos, and naturalists and biologists have wondered for years how the round sinuous plumbing found in most animals could produce an end product that looks like it came from a brick factory.

A new study presented at the 71st Annual Meeting of the American Physical Society's Division of Fluid Dynamics in Atlanta over the weekend seems to have finally cracked the case. When Patricia Yang, a mechanical engineer at the Georgia Institute of Technology, learned about cubic wombat poo, she decided to figure out the mystery. She specializes in the hydrodynamics of bodily fluids, including food, urine and blood, but had never come across anything quite like the wombat cubes.

“The first thing that drove me to this is that I have never seen anything this weird in biology. That was a mystery,” she says in a press release. “I didn't even believe it was true at the beginning. I Googled it and saw a lot about cube-shaped wombat poop, but I was skeptical.”

To study the strange process that converts grasses into wombie cubes, Yang and her team acquired wombat intestinal tracts from animals in Tasmania that had to be euthanized after being struck by cars and began studying their unusual digestive systems.

As George Dvorsky at Gizmodo reports, the team found that food moves normally through the wombat’s gut as a liquid slurry during most of its whomping 2.5 week journey through the creature’s system. Toward the end of that long journey, however, things changed. As the poo made its way through the last 8 percent of the intestine, it began to firm up and form a series of cubes. Previous studies came to the opposite conclusion: Some hypothesized that the poo was turned into cubes at the beginning of the small intestine.

By blowing up the intestines like nightmarish balloons and comparing them to pig intestines, Yang and her team determined that the wombat intestine has different elastic properties that put unequal pressure on the turds, creating the unique shape. There are two visible grooves in the wombat intestine where the elasticity is different. Pig intestines, on the other hand, had a uniform elasticity. As the poo moves through the wombat, the differing pressure of the intestines squeezes it into the cube shape, like a Play-Doh Fun Factory.

“It's really the first time I've ever seen anybody come up with a good biological, physiological explanation,” Mike Swinbourne, wombat expert at the University of Adelaide tells Tik Root at National Geographic.

The cubes aren’t just an accident of nature. They are part of the wombat lifestyle. The animals produce between 80 and 100 of the stinky cubes per night, and each individual cube measures almost an inch across each side, reports Dvorsky. Because they have poor eyesight, the animals rely on their stiffers to find mates. They use the stinky cubes to communicate by marking their territory so mates can use to find to track them down with. It's believed their cubic shape prevents the turds from rolling away.

The process could have some non-poop applications as well. Devices designed to function like a wombat poop-shoot with varying elastic pressure could lead to new manufacturing technologies.

“Molding and cutting are current technologies to manufacture cubes,” Yang tells Dvorsky. “But wombats have the third way. They form cubical feces by the properties of intestines…We can learn from wombats and hopefully apply this novel method to our manufacturing process. We can understand how to move this stuff in a very efficient way.”

That means someday we may use artificial wombat intestines to create products like bricks or candy, though that is a factory tour we may decide to skip.

Get the latest stories in your inbox every weekday.