The Tasmanian wombat is the only animal in the world capable of producing cube-shaped feces. But what are the reasons and mechanisms? Now scientists have found the initial answer.
Written by: TIK ROOT
Pictured here is a Tasmanian wombat at Heathville Wildlife Sanctuary. The shape of this animal feces is the strangest in the animal kingdom.
摄影：JOEL SARTORE，NATIONAL GEOGRAPHIC PHOTO ARK
Tasmanian wombats are a burrowing animal native to Australia, and perhaps best known for their stocky stature and cute appearance. Still, these cute marsupials may have some secrets you don't know: Tasmanian wombats are the only animals in the world capable of producing cubic-shaped feces.
Although this trait has attracted a lot of interest and discussion, in fact research on Tasmanian wombat droppings is very rare. As a result, scientists know almost nothing about this phenomenon, and until recently all changes have occurred.
Earlier this year, Patricia Yang, a researcher at Georgia Tech who specializes in bodily fluids, heard about the above at a conference and immediately began to study the topic.
"I didn't believe it at first," Yang said. However, after confirming, she began experimenting with the causes and mechanisms by which Tasmanian wombats produce cubic-shaped feces.
"People have come up with all sorts of theories," says Mike Swinbourne, a Tasmanian wombat expert at the University of Adelaide. One of the popular assumptions is that Tasmanian wombats produce cubic-shaped feces in order to stack them up to mark territory and prevent the feces from rolling away. But Swinbourne called it a false view.
While Tasmanian wombats do use feces to mark territory, "they're not likely to build fecal pyramids, they defecate haphazardly," he said.
In fact, Swinbourne said the shape of the cube may be related to the dry environment in which most Tasmanian wombats live. "They have to squeeze out every drop of water in the food," he said. Sometimes, in zoos where water is more accessible, Swinbourne says their droppings are less square. Drying helps the stool form a fixed shape with sharper angles.
Moisture plays a role, but "the main digestive tract is also a factor," added Bill Zeigler, senior vice president of the Brookfield Zoo's Animal Program, which has been keeping Tasmanian wombats in captivity since 1969. Peter Clements, chairman of the South Australian Tasmanian Wombat Organization, agreed, speculating that it was the result of a combination of the two factors.
Finding specific answers, though, is not easy. It took Yang and colleagues months to find the entrails of The Tasmanian wombats for research. No zoo in North America has preserved the guts of Tasmanian wombats, so Yang found the guts of two road-dead Tasmanian wombats in Australia. When these intestines arrived, she wasn't sure what the results would be.
The dung of The Tasmanian wombats is cube-shaped and can be used to mark territory, but no one knows how the dung changes into a cube shape. #advancedwombattechnology pic.twitter.com/fIvMhyRoWS
— Diana S. Fleischman (@sentientist)
"At first I thought their anus might be square, or that square feces formed in the stomach," she says. However, neither hypothesis is realistic. What she found was more important than how the intestines of Tasmanian wombats extended.
When food is absorbed, it moves through the gut, and pressure from the gut promotes stool formation, which means that the shape of the gut will affect the shape of the stool. So Yang and the research team used balloons to expand the intestines of Tasmanian wombats and pigs in order to measure and compare their elasticity.
The elasticity of the pig's intestines is relatively balanced, which explains why its feces are round. However, the intestinal shape of Tasmanian wombats is even more irregular. Yang observed two unique grooves that resembled ravines, and this section of the intestine was more malleable, which she believed helped turn feces into a cube shape.
Tasmanian Wombats
Species: Mammals
Diet: Herbivores
Group name: Population, population
Body length: 71-119 cm
Weight: 14.5-36.3 kg
Population trends: stable
IUCN Red List Status: Non-Threatened Species
"This is the first time I've seen someone come up with a plausible biological and physiological explanation," said Swinbourne, who reviewed the first draft. Clements, who also read the study, added, "I think it's a helpful explanation, but we need more explanations about the mechanisms of formation." ”
Yang acknowledges that there are still many issues that need to be explained, while saying her research is continuing. Her next goal is to figure out why it only takes two grooves to produce a cube instead of four. But even the preliminary findings mean it will have more far-reaching implications for certain industries, such as manufacturing.
Yang says cubes are very rare in nature. "At the moment we only have two ways to make cubes," she says, adding that humans either mold cubes plastically from softer materials or cut cubes from harder objects.
"Apparently The Tasmanian Wombats are using the third method."
(Translator: Stray Dog)