Wombats and the Mystery of Cubed Poop

A wisdom of wombats makes a thousand cubed poops in a day.  Believe it or not, that is a factually and grammatically correct sentence. Yes, a group of wombats is called a wisdom. And yes, they do indeed each poop about 100 distinct cubes each per day. How cube-ish are the cubes? Take a look for yourself!

They are pretty good cubes, right? It would take a significant amount of effort to sculpt cubes that are cube-like out of clay. But wombats are natural sculptors and make the cubes automatically. In fact, wombats are the only animals in the world that poop cubes. Until just a few years ago, scientists had no idea how they made this square scat. 

What Are Wombats?

Wombats are the world’s largest burrowing mammal. Wombats can weigh up to 80 pounds and are about 3 feet long when fully grown. In the wild, these fuzzy creatures can live to be almost 30 years of age! Wombats are herbivores. They eat a relatively mundane diet of grasses and other grass-like plants. Wombats incisors, a type of tooth, never stop growing. This constant growth means they need to chew on plenty of tough stuff every day to shave off their teeth as they grow. 

These burrowing cuties are a type of marsupial, which means they give birth to undeveloped young wombats who grow inside the mother’s pouch. Unlike most marsupials, the wombat’s pouch faces towards its hind legs. This unique evolutionary adaptation prevents the pouch from filling up with dirt while the wombat digs in the soil with its front paws. 

Wombats are productive diggers. A hard-working wombat can excavate three feet of tunnel in a single evening. As you can imagine, these networks of burrows can become extensive. Underground temperatures remain much more stable than air temperatures, so wombats hide in their burrows during the day to escape the searing Australian sun.  

Wombats are mostly nocturnal creatures, making them hard to see in real life.

Where do Wombats Live?

All marsupials, which also include kangaroos, Tasmanian devils, and koalas, are endemic to Australia and the Americas. Wombats can inhabit a wide variety of habitats within Australia, from arid grasslands to cool alpine zones, to eucalypt woodlands. Wombats need a healthy ecosystem of native Australian grasses nearby to thrive. 

The Three Different Kinds of Wombats

There are three species of wombats alive today. Differentiating the three depends on how hairy their nose is and where they live. The most common wombat is the bare-nosed wombat (Vombatus ursinus). The bare-nosed wombat lives near the coast in southeastern Australia in the provinces of New South Wales, Victoria, Tasmania, and southern Queensland. This also happens to be where nearly all the people in Australia live. 

The southern hairy-nosed wombat(Lasiorhinus latifrons) wombat lives in the province of South Australia in south-central Australia. 

Northern hairy-nosed wombat (Lasiorhinus krefftii) only lives in one small area in Queensland, called Epping Forest National Park. 

Unfortunately, These Cute Marsupials Are in Trouble

Wombats were, and in some cases still are, considered agricultural pests across Australia. Being the world’s largest burrowing mammal comes with consequences. These critters stir up substantial amounts of dirt and eat plenty of food, causing farmers and ranchers much frustration. Wombats can also destroy fences, letting invasive rabbits into areas people try to keep them out of. As a result, wombats were routinely killed as vermin across Australia throughout the 1900’s. Still today the common wombat is not protected in the province of Victoria. 

The IUCN lists the northern hairy-nosed wombat is among the most endangered mammals on Earth. At one point in the early 2000’s the population of breeding adults was just over 100. Predation by dingoes (wild dogs), competition for grass forage by non-native rabbits, and overgrazing by cattle and sheep drove this wombat population way down. Drought induced by climate change makes life additionally difficult for not only wombats, but all sorts of wildlife across Australia. 

In 2000 the Australian government installed a dingo-proof fence around the entirety of the northern-hairy-nosed wombat habitat. Their numbers have been slowly improving since then, and are now thought to be over 300 individuals. Still, this wombat remains a critically endangered species at risk of extinction due to wildfire or diseases like mange. 

The southern hairy-nosed wombat isn’t quite as imperiled as its northern neighbor, but is still listed as near-threatened. The common wombat is classified as “least concern.,” but scientists are concerned by that species’s population’s downward trend. 

Why is Wombats’ Poop Cubic?

As with so much in nature, we don’t know for certain why wombats poop cubes. However, we have a better idea now than we did just a few years ago.

One (debunked) folksy theory is that cubed poop is a superior shape to help wombats mark their territories. Why? Because cubes stack and don’t roll off of rocks. Can’t you imagine it? A pudgy wombat meticulously builds a menacing pyramid of cubed poops to alert other wombats to “stay away”. Or a wombat purposefully poops on slick rocks gleefully knowing their poop doesn’t roll right off. These theories aren’t wrong, per se, but there are probably more likely reasons for the evolution of cubed poop. There are so many animals that use their poop to mark their territories, but wombats are to only animals in the world with square poop.

The New Theory of Wombat Poop 

Researchers Patricia Yang and David Hu published a paper that opened the world’s eyes to the inner workings of the wombat. They found that the wombat’s unique intestine was responsible for the cubic wombat poop. Instead of being extruded, like clay from a mold or pasta from a pasta-maker, the poop gets shaped by wombats’ long intestines over the course of days.

Wombat intestines are about 10 times the length of their bodies. These long intestines help the critters extract an impressive amount of water from the food they eat. Wombats can live in incredibly arid environments. In fact, they barely need to consume water because their super intestines can squeeze all the water a wombat needs out of the plants it eats. Other desert mammals, such as the adorable kangaroo rat, have similar adaptations. Some scientists think that the process of forming cubes helps the wombat extract more water from its food.

Yang and Hu took the long intestines of a roadkill wombat and filled the intestines with a long balloon. They then inflated the balloon inside the intestine. By comparing how the balloon stretched the wombat intestines to how balloons stretched other animals’ intestines, the researchers unlocked a crucial aspect of the cubic poop mystery.

Instead of being uniformly tight as other animals’ intestines, wombat intestines have four ‘strips’ that run the length of the organ. Two of these strips contract more vigorously and two of the strips don’t contract less vigorously. These strips alternate, so that a cross-section of the wombat intestine would show vigorous-regular-vigorous-regular strips of the intestine. For some complicated, fluid-dynamics and physics reasons, these contractions turn the cylindrical poop into cubic poop, all within a cylindrical intestine. Apparently, the poop only becomes cubic in the last 20% of the wombat intestine.

The Surprising Implications of Wombat Poop Research

The researchers note that understanding wombat poop can help us in manufacturing and cancer diagnosis. Figuring out new ways of extruding plastics can help manufacturers mold different shapes. Colon cancer has been known to change the interior of intestinal walls. Now that we understand how changes in intestinal walls can change the shape of poops, researchers think they may be able to detect colon cancer earlier by observing human fecal samples. It’s always difficult to see how some research will be used for wildly different purposes!

Wombat poop is a strange wonder of the natural world. If you ever have the opportunity to wander around wombat habitat, keep an eye out for this charming, cubic feces!

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