Findings in title derived from the linked summary,^1 with reference to the hyperlinked peer-reviewed article.^2

From the linked summary^1 by Zoe Kean:

>Mammal life is diverse, and so are the poos mammals produce.

>"We understood how [the process] produced the corners that give them the square shape in cross-section," Dr Scott Carver told ABC Hobart's Helen Shield.

>"But not why they fragmented at such regular intervals along the length and came out as perfectly consistent little poos that are about the same length."

>Turning to volcano science and physics to uncover the answer, the researchers have not only discovered why wombats have "perfectly consistent little poos", but also what determines the shape of mammal poo in general.

>It was the cooling process of lava beds that inspired Dr Carver and his collaborators.

>After an eruption, lava beds cool and can solidify into specific and regular shapes.

>Dr Carver believes this research may one day help medical scientists.

>"Colorectal cancer, stress and various other things can influence the kind of faeces that people produce," he said.

From the hyperlinked article:^2

>Inspirational to our work is the formation of hexagonal columnar jointings in cooling lava beds, in which the width L of the hexagon scales as L ∼ J^−1 where J is the heat flux from the bed.

>Across 22 species of mammals, we report a transition from cylindrical to pellet feces if fecal water content drops below 0.65.

>Using a mathematical model that accounts for water intake rate and intestinal dimensions, we show pellet feces length L scales as L ∼ J^−2.08 where J is the flux of water absorbed by the intestines.

>We build a mimic of the mammalian intestine using a corn starch cake drying in an open trough, finding that corn starch pellet length scales with water flux.^−0.46

^1 Cubed wombat poo puzzle completed by researchers with the help of physics, volcanic science, Zoe Kean for ABC Radio Hobart, 21 Feb. 2023, https://www.abc.net.au/news/2023-02-21/wombats-square-poo-research-how-consistent-cubes-made/102000530

^2 Magondu, B. et al. (2023) Drying dynamics of pellet feces. Soft Matter 19 723-732. https://doi.org/10.1039/D2SM00359G