In 2015, Patricia Yang of the Georgia Institute of Technology presented a mathematical model to predict the shape of animal stools. During a presentation lecture, an attendee asked him if his theory worked for wombats too. Yang had never seen wombat droppings, plump, hairy marsupials three feet long, short-legged, and native to Australia. When he looked for photos on the internet, he came face to face with reality, they were cubes. And also science had no idea how they were being produced. Now, five years later, Yang thinks he has the answer to the mystery of the cubic wombat poop. Their findings have just been published in the magazine.

To find out what was going on inside the wombat, Yang and his lab supervisor at Georgia Tech, biomechanical engineer David Hu, examined the dissected intestine of the marsupial. This is how they were able to observe that the stool begins as a shapeless and elongated mass at the beginning of the intestinal route, but that it ends up turning into cubes before exiting the anus, which although it may seem strange, is as round as that of any other species. What happened then?

The secret is in the gut, it turns out, is the gut, the researchers used two new wombat organ dissections and reshaped mathematical models to recreate what happens in the wombat’s ‘pipes’, which are unusually long – up to thirty feet long. It is even longer than the human intestine, reaching up to seven meters. And you have to remember that these creatures are barely one meter tall, so they take ten times longer to absorb all the nutrients and water from their food. This is how single wombat digestion can last up to 15 days.

As a result, the feces of these marsupials are almost twice as dry as that of humans. Although this may sound like constipation, it actually helps wombats survive droughts in the Australian rainforest. And according to Yang it also allows them to “specify” the shape of their stools and make them cubic.Using a balloon to inflate certain parts of the intestine, the researchers noted varying levels of thickness and stiffness in some tissues and muscles. In practice, this means that parts of the intestine’s circumference contracted differently than the rest due to the different thickness of the muscles. The tight parts contracted quickly, pushing the poop harder and creating smooth faces; while the less rigid parts contracted more slowly, shaping the corners.

A hundred cubic poops daily By creating a simple model of the gut, the authors found corners formed in less than 10 contraction cycles. In other words, a cube in less than ten bowels “pushes”. With contractions that occur every couple of seconds in a wombat’s gut, in five days the stool will have undergone 100,000 contractions,” the team wrote in the study.According to the researchers, a sufficient amount of these contractions could form a series of several cubes at the end of the wombat’s intestine when the poop is driest (this would also partly explain why this animal excretes about 100 cubes a day). In fact, the dissections show that the cubes form only in the last 17% of the intestine. “It’s almost like baking a cake,” Hu explains. The dough starts out moist and shapeless, drying out over time as it heats up in the oven. As it hits the edge of the cake pan, it begins to form corners and flat surfaces. Most of the solidification happens right at the end.

And why cubic poops? But even if the biological mechanism has been revealed, what is the reason that it is the only species that has evolved into cube-shaped poop? Wombats don’t have great eyesight, so they often use their droppings to communicate with each other, leaving their “gifts” on rocks, logs, and other high places to make their message more visible.

Then the square shape could help you stack your “messages” more successfully. There is another hypothesis that states that the cubic structure of the feces allows a greater surface to increase the dispersion of the animal’s odor, which can convey social messages or reproductive status. There are also researchers who think that the cubes are just an unexpected consequence of the dehydration to which the feces are subjected in the intestine since in captivity, where they have a diet richer in water, the wombat poop is much less defined. That is why the mystery of wombat depositions continues. For now