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Wild Things

The weird and wonderful in the natural world

Sarah Zielinski

Wild Things


Wild Things

Why create a model of mammal defecation? Because everyone poops

kitten in a litterbox

Mammals with cylindrical feces — like cats and humans — tend to take about the same amount of time to poop, no matter their size, a new study reports.

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An elephant may be hundreds of times larger than a cat, but when it comes to pooping, it doesn’t take the elephant hundreds of times longer to heed nature’s call. In fact, both animals will probably get the job done in less than 30 seconds, a new study finds.

Humans would probably fit in that time frame too, says Patricia Yang, a mechanical engineering graduate student at the Georgia Institute of Technology in Atlanta. That’s because elephants, cats and people all excrete cylindrical poop. The size of all those animals varies, but so does the thickness of the mucus lining in each animal’s large intestine, so no matter the mammal, everything takes about the same time — an average of 12 seconds — to come out, Yang and her colleagues conclude April 25 in Soft Matter.

But the average poop time is not the real takeaway here (though it will make a fabulous answer to a question on Jeopardy one day). Previous studies on defecation have largely come from the world of medical research. “We roughly know how it happened, but not the physics of it,” says Yang.

Looking more closely at those physical properties could prove useful in a number of ways. For example, rats are often good models for humans in disease research, but they aren’t when it comes to pooping because rats are pellet poopers. (They’re not good models for human urination, either, because their pee comes out differently than ours, in high-speed droplets instead of a stream.)

Also, since the thickness of the mucus lining is dependent on animal size, it would be better to find a more human-sized stand-in. Such work could help researchers find new treatments for constipation and diarrhea, in which the mucus lining plays a key role, the researchers note.

Animal defecation may seem like an odd topic for a mechanical engineer to take on, but Yang notes that the principles of fluid dynamics apply inside the body and out. Her previous research includes a study on animal urination, finding that, as with pooping, the time it takes for mammals to pee also falls within a small window. (The research won her group an Ig Nobel Prize in 2015.)

And while many would find this kind of research disgusting, Yang does not. “Working with poop is not that bad, to be honest,” she says. “It’s not that smelly.” Plus, she gets to go to the zoo and aquarium for her research rather than be stuck in the lab.

But the research does involve a lot of poop — and watching it fall. For the study, the researchers timed the how long it took for animals to defecate and calculated the velocity of the feces of 11 species. They filmed dogs at a park and elephants, giant pandas and warthogs at Zoo Atlanta. They also dug up 19 YouTube videos of mammals defecating. Surprisingly, there are a lot of those videos available, though not many were actually good for the research. “We wanted a complete event, from beginning to end,” Yang notes. Apparently not everyone interested in pooping animals bothers to capture a feces’ full fall.

The researchers also examined feces from dozens of mammal species. (They fall into two classes: Carnivores defecate “sinkers,” since their feces are full of heavy indigestible ingredients like fur and bones. Herbivores defecate less-dense “floaters.”) And they considered the thickness and viscosity of the mucus that lines mammals’ intestines and helps everything move along as well the rectal pressure that pushes the material. All this information went into a mathematical model of mammal defecation — which revealed the importance of the mucus lining.

Yang isn’t done with this line of research. The model she and her colleagues created applies only to mammals that poop like we do. There’s still the pellet poopers, like rats and rabbits, and wombats, whose feces look like rounded cubes. “I would like to complete the whole set,” she says. And, “if you’ve got a good team, it’s fun.”

Animals

Why a mountain goat is a better climber than you

By Sarah Zielinski 12:21pm, December 7, 2016
For the first time, scientists have analyzed how a mountain goat climbs a cliff. Big muscles in the shoulder and neck help a lot, they find.
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Now there are two bedbug species in the United States

By Sarah Zielinski 9:00am, November 23, 2016
The tropical bedbug hadn’t been seen in Florida for decades. Now scientists have confirmed it has either resurfaced or returned.
Animals

Old bonobos have bad eyesight — just like us

By Sarah Zielinski 2:22pm, November 8, 2016
As bonobos age, they lose their ability to see things close up, a new study suggests.
Conservation,, Animals

City dolphins get a boost from better protection and cleaner waters

By Sarah Zielinski 11:08am, November 3, 2016
Bottlenose dolphins near Adelaide, Australia, are slowly growing in number due to better environmental conditions and better protection.
Animals

With climate change, grizzly bears may hibernate less

By Sarah Zielinski 1:00pm, October 25, 2016
New research shows that food availability and weather are driving when grizzly bears enter and exit their dens for hibernation.
Animals

Painted lady butterflies’ migration may take them across the Sahara

By Sarah Zielinski 11:32am, October 12, 2016
The migratory patterns of painted lady butterflies are largely unknown. Now scientists have found evidence that some may migrate across the Sahara.
Animals,, Conservation

Nature has a dog problem

By Sarah Zielinski 11:00am, September 30, 2016
Free-roaming dogs spread disease, kill wildlife by the thousands and have even caused extinctions. But their full effect on the environment has been little studied.
Animals,, Evolution,, Conservation

Kauai’s native forest birds are headed toward extinction

By Sarah Zielinski 3:00pm, September 13, 2016
Kauai’s honeycreepers are losing their last refuges from mosquito-borne diseases that are spreading due to climate change. Some could become extinct within a decade.
Animals,, Conservation

As IUCN votes on ivory trade, elephants’ future looks bleak

By Sarah Zielinski 9:34am, September 9, 2016
As the IUCN prepares to debate an end to the ivory trade, two new reports show just how poorly Africa’s elephant species are faring.
Animals,, Evolution

Tail vibrations may have preceded evolution of rattlesnake rattle

By Sarah Zielinski 7:00am, August 31, 2016
The rattle on a rattlesnake evolved just once. A new study contends it may have come out of a common behavior — tail vibration — that snakes use to deter predators.
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