The only animal that poops cubes

The wombat, an Australian marsupial that looks like a grumpy teddy bear, is the only known animal that produces cubic droppings. Actual cubes: about two centimetres across, flat faces, defined edges. And plenty of them — up to a hundred in a single night.

For years it was a genuine scientific mystery. The answer came from a Georgia Tech team led by engineer Patricia Yang, working with researchers in Tasmania: the secret lies not at the exit but in the gut. Its final stretch alternates stiff zones with elastic ones that contract at different rhythms, and that irregularity gradually moulds corners where any other intestine would make spheres. It helps that a wombat's digestion is extraordinarily slow — over two weeks — and squeezes out almost all the water: the mass comes out dry and holds its shape.

And why would anyone want to manufacture cubes? Territory. The wombat leaves its markers in plain sight on rocks and logs, right at neighbour-nose height, and a cube has one virtue no sphere can offer: it doesn't roll away.

The discovery won an Ig Nobel Prize in 2019, the award for science that first makes you laugh and then makes you think. Hard to find a better example.