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Scientists solve a mammal poop mystery: Why do wombats have cube-shaped feces?

Biologists and engineers solve a major marsupial mystery.

Why Wombats Poop Cubes

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Scientists solve a mammal poop mystery: Why do wombats have cube-shaped feces?

Biologists and engineers solve a major marsupial mystery.

Nature

Why Wombats Poop CubesPublished: March 23, 2022NARRATOR: Introducing the cube, the only six sided scat in nature an exceptional excrement direct ♪ ♪ from the bottom of the common wombat. Wombats are Australian marsupials. They graze continuously. It can take up to two weeks for them to digest their food. The process squeezes out every last drop of water. A good strategy in Australia's harsh climate but that doesn't explain how or why the end result is a cube.PATRICIA YANG: From, from my eyes, it looks very artificial. Like is that even a real thing comes out from animal body? For most mammals, including humans, the feces come out like a toothpaste coming out. So when you squeeze it, the shape of feces the same as the the orifice and the solid soft matter comes out slowly and but smoothly as a sausage. But how would wombat has this cubicle shape? Our hypothesis is that it must be the intestine that molded this shape.SCOTT BURNETT: The logical next thing to do for us was to examine microscopically what the tissues looked like. We found thicker and thinner muscle around that circumference. And along the length of the intestine these sort of thicker and thinner regions formed bands.PATRICIA YANG: We have never seen this before in any kind of animals. We are wondering if different thickness, the thicker and thinner bands how would that affect the stretchiness of the wombat intestine? So we put a wombat intestine into this Tensile Test. Tensile test is the way to test how stretchy this material is. And we discovered that the lumping test is stretch but they are not stretch in an even way. For the thicker part they stressed less than the soft part. We were surprised that the stretchiness were four times different among those two bands. With this measurement, we fit in this information to a mathematical model and that it contracts and over several cycles contraction we see a shape with four corners.SCOTT BURNETT: I've got a really simple way of showing pretty much how they form these cubes using this rubber here. And so we can just kind of pinch the sides of the rubber band and kind of simulate those, those more stiff regions of the intestine. And if you just hold it like this you can just give a go like that, and it begins to form a cube. So when the contractions happen it is basically squeezing the feces into this shape and it does this rhythmically over time. And so they eventually get molded into that. And as the moisture is absorbed out of the feces and it starts to fragment along its length and form the distinctive actual cubes that come out at the end.

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Why Wombats Poop Cubes

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Support Provided By

Explore More

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