The shape is not cut at the exit. A wombat’s lower intestine acts as a flexible, unevenly moving forming system.
Quick answer
Research on bare-nosed wombats indicates that cube-like droppings form within the lower intestine. Regions of different stiffness deform differently during contractions, helping create flatter faces and corners as the contents become drier and firmer. The animal does not need a square opening. How the cubes form is better established than why this unusual shape evolved.
A wombat is a rounded, burrowing marsupial with an unexpectedly geometric output. Its droppings can resemble little blocks, complete with flatter surfaces and distinct corners. The contrast makes the question sound like a joke, but solving it required anatomy, measurements and models.
Most familiar ways of making a cube use a rigid mould or a cutting tool. The wombat achieves an approximate version inside soft tissue. The interesting explanation lies in how that tissue varies around the intestine, and what repeated contractions do to the material inside.
What researchers mean by cube-shaped
The droppings are biological objects, not machine-cut dice. “Cube-shaped” refers to their roughly blocklike geometry: flattened regions joined by corners, with natural variation. A particular piece can have rounded edges, unequal dimensions or a less distinct shape.
The research discussed here focused on the bare-nosed, or common, wombat. The University of Tasmania emphasizes that species context. Findings about a studied species and its tissues should not automatically become precise anatomical claims about every wombat. [3]
This matters when comparing photographs online. A representative image can show the phenomenon, but one object is not a statistical description. Researchers need repeated observations and measurements to distinguish a characteristic pattern from an unusually neat example.
The cubes already exist inside the intestine
Dissections found the characteristic shapes forming before the material left the animal. That observation ruled against explanations requiring a square-shaped exit to stamp each piece into its final form. The location of the developing shape was an essential clue. [1]
It is a good example of how locating a process changes the possible explanations. If a shape is present upstream, a mechanism acting only at the end cannot be its sole cause. The researchers could focus on the section of intestine where the contents changed.
The Georgia Tech team’s account also rejects the old idea that the final opening provides a square mould. Their work directed attention to the mechanics of the intestinal wall rather than a geometrical hole. [2]
Why a rounded tube need not squeeze uniformly
A tube’s outline does not tell you whether every part stretches the same amount. Two regions can experience comparable loading while deforming differently because their material stiffness differs. A soft region changes shape more readily than a stiffer neighbour.
Imagine a flexible sleeve assembled from alternating softer and firmer strips. Pressurizing or squeezing it need not produce a perfectly circular deformation. The location of the different materials influences where the sleeve bends and where it resists.
This is a conceptual analogy, not an anatomical model of all the tissue layers. It shows why the phrase “round intestine” does not logically require “round contents” under every combination of material properties and motion.
What was different about the wombat tissue?
Researchers found non-uniform mechanical properties around the circumference of the lower intestine. The University of Tasmania describes two stiffer and two more flexible regions. Those differences, combined with contractions, help explain how flatter faces and corners emerge. [3]
An early research presentation reported measurements of how intestinal tissue stretched using an inflated balloon. Its value was to replace a visual impression with a mechanical comparison: different regions did not simply behave as interchangeable elastic material. [4]
That distinction is central. “Soft tissue” is a broad description, not a single engineering specification. Thickness, fibre organization and other structural features can make biological material respond differently from place to place.
How contractions and drying contribute
The 2021 study combined tissue measurements with mathematical modelling to investigate how non-uniform stiffness and contraction could mould corners. The contents also change consistency along the digestive tract, becoming a material capable of retaining a shape rather than freely flowing away. [1]
Shape formation requires both a forming action and something that can keep the result. Water poured into a block-shaped container becomes liquid with a flat top, then flows away when released. A sufficiently cohesive, deformable material can retain an imposed geometry after the surrounding forces change.
The wombat system is neither a rigid cookie cutter nor a set of tiny blades. It repeatedly deforms the contents through a soft wall. Uneven wall response creates a route to corners without requiring the wall itself to be a permanent square tube.
Why models help test the explanation
The research team describes intestine mimics in which differing stiffness and imitated contractions produced more square-like forms than a more uniform control. Such a comparison tests whether the proposed ingredients can generate the relevant pattern. [2]
A model is not an entire living wombat. It deliberately simplifies the system so investigators can change selected features. If changing wall mechanics changes the outcome in the predicted direction, that supports the proposed role of those mechanics.
It does not mean every biological detail has been captured. The strongest explanation combines observations inside the real animal with measurements and a model that reproduces an important aspect of the result.
Does the shape depend on water content?
The University of Tasmania notes that droppings can appear less cubed in wetter conditions. That observation fits the broader idea that material consistency matters alongside wall mechanics. It does not provide a universal rule for diagnosing an individual animal from a photograph. [3]
In physical terms, a forming process can work differently when the material becomes more fluid or more resistant to deformation. The same moving boundary does not guarantee the same output if the properties of the contents change.
That general lesson applies far beyond digestion. Food processing, ceramics and soft-material manufacturing all have to coordinate the forming motion with the behaviour of the material being shaped.
Why make cubes at all?
Wombats use droppings at shared locations and prominent landmarks, making communication a plausible part of the story. But finding a mechanical route to cubes does not prove which evolutionary pressure produced it. “How” and “why” require different evidence.
A 2025 study investigated olfaction and the use of latrines by bare-nosed wombats. Its subject was the communicative role of scent, rather than another test of how intestinal contractions make corners. These are connected research questions, but the evidence should remain separate. [5]
The University of Georgia’s account reports individually distinct chemical signatures in the droppings, examined using gas chromatography and mass spectrometry. That supports the possibility of individual information in scent. It does not, by itself, establish that the cube shape is essential to recognizing another wombat. [6]
Do cubes stop the droppings rolling away?
A block can behave differently from a sphere on an inclined surface, so resistance to rolling is a plausible idea. Demonstrating that a particular geometry rolls less easily, however, is not the same as proving that natural selection produced the shape for that reason.
Researchers would need to connect shape, placement, persistence and biological consequences. An appealing functional story becomes stronger when those links are measured, rather than assumed because they sound sensible.
The existing work is most compelling when stated at its actual level: material differences in the intestine explain formation, while behavioural and chemical studies investigate what the deposits do. The full evolutionary account remains a broader question.
Frequently asked questions
Does a wombat have a square-shaped exit?
A square opening is not needed. The characteristic shapes were found inside the lower intestine before release. [1]
Are the droppings perfect cubes?
No. They are natural, approximately cuboidal objects with variation in faces, corners and proportions.
Does drying outside turn ordinary round droppings into cubes?
The research found the geometry developing internally. Outside drying is therefore not an adequate explanation for the original formation of the corners. [2]
Has science completely settled why wombats evolved this shape?
No. Mechanical formation and evolutionary function are different questions. Research on scent communication adds evidence without proving that every aspect of the shape has one established purpose.
Keep exploring
Sources and further reading
- Yang and colleagues (2021) — Intestines of non-uniform stiffness mold the corners of wombat feces (paper, PDF)
- Georgia Tech research team — Cubed-poop experiments and findings
- University of Tasmania — Wombat cubed-poo mechanism
- American Physical Society — How wombats make cubed poo, 2018 research abstract
- McMahon and colleagues (2025) — Olfaction in the bare-nosed wombat
- University of Georgia — Research into wombat scent communication
Reference review: November 10, 2026.
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Last updated November 12, 2026.
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