FactSentinel

Wombats, the stocky burrowing marsupials native to Australia, are the only known animals that produce cube-shaped droppings. Each pellet is a distinct cube with fairly flat sides and sharp corners, and a wombat may deposit between 80 and 100 of them in a single night. This was documented by researchers who examined the digestive tracts of wombats and published findings, including work presented at the American Physical Society's Division of Fluid Dynamics meeting in 2018 and in the journal Soft Matter in 2021.

The cause lies in the wombat's intestines, not in any molding or shaping at the end of the digestive tract. Research led by Patricia Yang and David Hu at the Georgia Institute of Technology found that the final 8 percent of the intestine has regions of varying stiffness. Along the intestinal wall, two stiffer grooves alternate with two more flexible sections. As the material moves through, the flexible regions stretch more than the stiff ones, and this uneven contraction gradually forms the waste into cubes as it dries and hardens.

A common misconception is that wombats squeeze their droppings into cubes using the anus. The evidence points instead to the elastic properties of the intestinal wall. The shape also has a practical purpose, since the cubes do not roll away. Wombats stack them on logs, rocks, and raised ground to mark territory and communicate with other wombats.