Like other herbivores, wombats poop a lot, but unlike any other known species, their droppings are almost cubic, the size and shape of dice. Biologists have long had an explanation for why this is, but have now mostly explained the how.
Anything practiced by one animal species alone among all the millions on Earth is interesting, and biologists have long been intrigued by wombats' distinctive droppings. Moreover, even world leaders in animal preservation recognize wombats' special excellence. The shape is thought to help wombats mark their territory, by allowing them to produce tall piles that don't roll down the often steep hillsides of their habitat.
However, many other species use dung to mark their territory, and have never come up with this useful innovation, for the simple reason it isn't easy to construct a digestive system that produces cubic, rather than broadly cylindrical, shapes. Now the wombat's secret has finally been revealed and published in the journal Soft Matter.
The work was led by Dr Patricia Yang of the Georgia Institute of Technology, proving wombat-love is truly a universal language. "The first thing that drove me to this is that I have never seen anything this weird in biology. That was a mystery," Yang said in a statement. "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."
So Yang, who studies fluid dynamics within the body, did the appropriately scientific thing. She obtained digestive systems of wombats tragically killed by cars and inflated their intestines. The widespread assumption wombat anuses must be square has long been debunked, and Yang also contradicted the previous theory that the cubic shape is formed at the top of the intestine.
Instead, the digested wombat food comes down the gut in a semi-liquid state, only to solidify in the last 8 percent of the intestine, something Yang and colleagues attribute to alternating rigid and flexible stretches of the intestine walls. These apply very different strains to the cubes' corners and edges to produce the cubic shapes.
Curiosity-inspired research always attracts allegations of wasting tax-payer funds, but Yang thinks there could be practical outcomes besides the satisfaction the results bring. "We currently have only two methods to manufacture cubes: We mold it, or we cut it. Now we have this third method," she said. Whether replica wombat intestines will prove advantageous in producing industrial parts remains to be seen, but it's possible future manufacturing revolutions could be inspired by the wombat's gut.
One thing Yang hasn't solved, however, is the old question of how painful it is for wombats to be constantly shitting (small) bricks.
A version of this article was first published on 19 November 2018.