What shapes the cube-shaped droppings of the wombat?

Unevenly elastic walls in the final stages of the colon hardening the fecal matter

The distinctive cube shape of wombat droppings is a result of mechanical shaping within the final segment of the large intestine, specifically the colon. This section possesses walls characterized by varying degrees of elasticity. As the fecal matter progresses through this area and begins to dry and harden, the non-uniform elasticity of the colon walls molds the material into the characteristic square blocks. This physical process, rather than the composition of the ingested food itself, dictates the unique geometry. Functionally, this shape is advantageous as it stops the droppings from rolling off elevated surfaces or uneven ground, thus making them effective tools for territorial marking.