Wombat dung is a cube
Bare-nosed wombats produce roughly cubic feces. The corners are formed by a stiff intestine of uneven elasticity, not by a square hole.
Established2 min read
The feces mark territory on rocks and stay put, which a round pellet would not. Dissection and a materials model showed regions of the intestinal wall that are stiffer than their neighbours. As the pellet dries and is pushed, the stiff bands become the flat faces and the softer bands the corners. About eight to ten cubes a night.
The 2021 Soft Matter paper turned a pub fact into a measured elasticity problem. The cube is not carved. It is extruded by a tube whose stiffness varies around the circumference.
Caveats
- Not every scat is a perfect cube. The habit is cuboid, with rounded edges.
- The adaptive story (stacking, not rolling away) is plausible and less nailed down than the mechanism.
Sources
- 1Yang P. J. et al.. Intestines of Non-uniform Stiffness Mold the Corners of Wombat Feces. Soft Matter 17, 2021.