How a wombat’s gut makes square-sided droppings
The cube shape forms inside the wombat, not after the droppings hit the ground. As waste moves through the final stretch of its intestine, the gut squeezes and relaxes around it. In wombats, that stretch has regions with different flexibility: some expand more readily, while others stay relatively stiff. Their uneven pressure gradually molds the drying waste into pieces with flat sides and distinct corners.
That makes the process unlike simply pushing soft material through a square opening. The shape emerges from the intestine’s changing contractions and uneven elasticity, as the waste firms up during its slow passage through the gut.
Why the shape may be useful
Wombats leave droppings in conspicuous places, including on rocks and logs. Researchers have proposed that the cubes are useful because they are less likely to roll away than rounded droppings, keeping scent markers where other wombats can encounter them. The shape’s exact role in communication is not fully settled, but it offers a practical advantage for an animal that marks its surroundings this way.
The memorable part is that a natural cube needs no square-shaped outlet: the wombat’s intestine does the shaping from the inside.
