How a soft material keeps its corners
A wombat’s intestine is not a smooth, uniformly squeezing tube. Its wall has regions that differ in stiffness and flexibility. As the gut contracts, those regions press the contents with unequal force, gradually shaping the material into a form with flatter sides and corners. The shape develops during passage through the intestine—not at the exit.
That distinction matters: a square opening would stamp a shape quickly, like a mold. Wombat feces instead take shape through repeated, uneven contractions over a long journey. By the time they leave the body, they are also dry enough to hold their form rather than slump back into a rounded lump.
Why the shape survives outdoors
The corners make the droppings less likely to roll on uneven ground, including the rocks and slopes wombats use as marking spots. That helps keep a scent marker where another wombat is more likely to encounter it. The shape is therefore useful not just as an oddity, but as a physical feature suited to where the animals leave their signs.
The remarkable part is the combination: a flexible gut can produce a sharply edged object without a square-shaped outlet. The intestine’s changing stiffness does the slow work, and the relatively dry result preserves it afterward.
