Mystery of cube-shaped wombat poop solved

For many years, scientists have been fascinated by wombats' square poop. Wombats are marsupial animals that live in Australia, and yes, they literally poop out cubes, and lots of them. New research using wombat roadkill and skinny balloons, which clowns shape into animals, brought the world just a little closer to understanding and appreciating their cubed droppings. To better understand these findings, you need to understand a few basic things about digestive systems.

A Digestive System Review

When you eat food, it travels to your stomach. Just so you know, the food does not fall into your stomach. Instead, muscles push the food into your stomach. If you found a reason to eat upside down, the food would still make it to your stomach. Contrary to popular belief, your stomach does very little of the digesting, but it is still a critical part. The stomach uses its muscles and enzymes to break down your solid food into a smoothie-like consistency.

This is where digestion really gets going. Your stomach sends the thick ooze into your small intestines. By the way, this is when your stomach starts growling. The growl is simply your stomach rolling its muscles to make sure there is no food left to send to the intestines. Our brains interpret this as you being hungry. At any rate, small intestines are about 25-feet long and about an inch in diameter. Your small intestine is lined with millions of protruding bumps that increases the surface area of your intestine to the size of a tennis court. The cells lining this giant surface area are extracting about 95 percent of your food’s nutrients and putting it into your body.

Whatever is left is sent to your large intestines, which are about five feet long and three inches in diameter. The large intestines extract water from the leftover matter and squeeze it into tube-shaped waste. That waste comes out of our body, and that’s the end of that.

Back to Wombats

For many years, people have noticed that wombat droppings come out as nice cubes. However, scientists were confused because a wombat’s intestines are round like ours. The opening in which the wombat waste comes out of is round, too. Round intestines and round openings make round droppings — but not in the case of the wombat.

An Australian man had two wombat roadkill specimens in his freezer (for whatever reason) and finally decided it was time to get rid of them. He donated the frozen wombats to scientists. Naturally, the curious scientists opened up the intestines and found lots of cube-shaped poop ready to come out. This was not a surprise, as many before them discovered this.

The new information comes from what the scientists did next. They used long and skinny balloons, like the ones clowns use to make balloon animals, and inflated them inside one of the wombat’s intestines. What they found was, unlike most animals, the entire intestine did not expand the same when the intestine was full. Instead, some parts of the intestine expanded while other parts were more rigid. The alternating elastic and rigid sections break up the wombat waste into cubes, and that solves a very long mystery.

Now What?

As strange as this story may be, it’s not over. At some point in the wombat’s evolutionary history, the wombats began to use their cube-shaped poop to communicate with other wombats. The cubes allow the wombats to stack up their droppings as a way to communicate with others that they are in the area. The wombat may be warning others to stay away or it could stack them to invite others in.

The biology of wombats give them plenty of “material” to communicate with. The adult wombat, which has a length of about three feet, has about 150 feet of intestines wrapped up inside it. That can make a lot of cubes.

If you think this is all a little strange, you are probably right. But it has been a lot stranger. Today, a wombat is the size of a small pig and weighs about 50 pounds. However, just 50,000 years ago (quite recent in geologic time) wombats weighed in at about 7,000 pounds and were the size of a large rhinoceros. That would have made some really large, cubed poop.

Mike Szydlowski is the science coordinator for Columbia Public Schools.