Squaring Up Theories on Wombat Poop

Squaring Up Theories on Wombat Poop


My entire life, I have been squirreling away facts in my brain that will come in handy when I inevitably get on Jeopardy. One of my favourites is a classic tidbit about one of Australia’s less-violent marsupials, the wombat. Specifically, that fact that its scat is cube-shaped!
While theories have abounded as to why wombats poop cubes (They stack them to mark their territory! There’s so little water to drink that they compress it all out in their guts!), no one has tried to find out the how. At least until Patricia Yang, a post-doctoral fellow in Mechanical Engineering at the Georgia Institute of Technology, got interested in the subject after hearing about it at a conference. Yang, who specializes in the movement of fluids in the bodies of animals, dissected the intestines of two roadkilled wombats that took months to acquire. (As a control, she and her team used a pig intestine.)

“As food is digested it moves through the gut, and pressure from the intestine helps sculpt the feces – meaning that the shape of the intestine will affect the shape of a dropping. So Yang and the team expanded both wombat and pig intestines with a balloon to measure and compare their elasticities (or stretchiness).

The pig intestine had a relatively uniform elasticity, which would explain the animal’s rounder poo. The wombat intestines, however, had a much more irregular shape. Yang observed two distinct ravine-like grooves, where the intestine is stretchier, which she believes helps shape wombat feces into cubic scat.”
Yang’s experiment goes a long way toward explaining why wombats’ waste materials conform to a shape that, barring crystals,  is actually pretty rare in nature. That’s a lofty result for a problem most often found in the gutter!
(Speaking of exotic animals and their bathroom habits: did you know that the three-toed sloth only poops once a week? They do so in response to their incredibly slow-moving metabolisms, as well as to minimize time on the ground that could attract predators. Now that’s efficiency…)