The fact that wombats use their poop to mark their territory isn’t unusual in the animal kingdom. What does separate them from their furry peers is the distinctive shape of their droppings. Wombats are the only animals to poop cubes, according to Science News, and researchers think they have finally figured out how they do it.

Mechanical engineers David Hu and Patricia Yang at the Georgia Institute of Technology received a lovely gift of two frozen wombats—roadkill, mind you—from an Australian colleague. After dissecting the specimens, they analyzed the animals’ intestines and discovered that they’re incredibly stretchy. Wombats' intestines expand to two or three times their original width when feces passes through, the researchers reported at an annual meeting of the American Physical Society's Division of Fluid Dynamics in Atlanta.

Bjørn Christian Tørrissen, Wikimedia Commons // CC BY-SA 3.0

To test the elasticity of different sections of intestine, the researchers took skinny balloons (the kind used to make animal shapes) and inflated them inside the organ. Not all of the sections were stretchy, though, and Yang suggested that the stiffer areas might help form the edges of the poo cubes as waste gets pushed through the last few feet of intestine. (Wombat digestive tracts measure about 30 to 40 feet, according to another study of digestion in wombats.)

The final eight percent of the intestine is also where the feces changes from “a liquid-like state into a solid state composed of separated cubes,” each measuring about three-quarters-of-an-inch in length, according to researchers.

The advantage of wombats' oddly-shaped dung, according to Science News, is that they’re better for stacking and they don’t roll off rocks as easily. Wombats tend to produce 80 to 100 turds per night, and they prefer to deposit them atop rocks, logs, and piles of dirt, where they can easily be seen. The smell also helps them navigate better at night.

Although impressive in their own right, wombats aren’t the only animals whose fecal matter seem to defy physics. Take sloths, for instance: A single bowel movement can weigh up to a third of a sloth’s body weight.

[h/t Science News]