Monday, 1 May 2017

Most mammals big or small take about 12 seconds to defecate

26 April 2017

By Chelsea Whyte

Everyone poops, and it takes them about the same amount of time. A new study of the hydrodynamics of defecation finds that all mammals with faeces like ours take 12 seconds on average to relieve themselves, no matter how large or small the animal.

The research, published in Soft Matter, reveals that the soft matter coming out of the hind ends of elephants, pandas, warthogs and dogs slides out of the rectum on a layer of mucus that keeps toilet time to a minimum.

“The smell of body waste attracts predators, which is dangerous for animals. If they stay longer doing their thing, they’re exposing themselves and risking being discovered,” says Patricia Yang, a mechanical engineer at the Georgia Institute of Technology in Atlanta.

Yang and colleagues filmed elephants, pandas and warthogs at a local zoo, and one team member’s dog in a park, as they defecated. All these animals produce cylindrical faeces, like we do, and this is the most common kind among mammals. Though the animals’ body masses ranged from 4 to 4,000 kilograms, the duration of defecation remained constant.
Slimy Chute

That consistency across animals is down to a few things. First, the length of faecal pieces was 5 times as long as the diameter of the rectum in each of the animals.

Yang also found that the normal, low-level pressure animals apply to push through a bowel movement is constant, and unrelated to a creature’s body mass. This means that, whether it’s a human or a mouse, the pressure used on normal excrement is the same. This is similar to her previous finding that mammals take the same amount of time to empty their bladders.


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