Whether you are an elephant, a human, a lab mouse or a giant panda, size doesn’t matter when it comes to time taken to use the toilet, because a new study says most of us take around 12 seconds to do the deed.
Researchers from the Georgia Institute of Technology in Atlanta studied the hydrodynamics (a branch of physics dealing with the motion of fluids) of defecation and found that body mass doesn’t play a role when it comes to the duration of excretion.
They filmed animals defecating and collected stool samples from 34 species. In addition, they also looked at a number of YouTube videos of animals such as dogs, cats, pandas and elephants relieving themselves.
Scientists say the main reason why this takes such a short time stems from our primal instinct to protect ourselves from predators – the more time we spend doing our thing, the greater risk of exposure to danger.
Writing in The Conversation, scientists David Hu and Patricia Yang concluded that while duration was constant, volume and speed of defecation varied greatly.
“For instance, an elephant defecates at a speed of six centimetres per second, nearly six times as fast as a dog,” they wrote. “The speed of defecation for humans is in between: two centimetres per second.”
They found that bigger animals defecated at higher speeds – and it was down to the mucus lining in the walls of the large intestine.
“The mucus layer is as thin as human hair, so thin that we could measure it only by weighing faeces as the mucus evaporated,” they continued. “Despite being thin, the mucus is very slippery, more than 100 times less viscous than faeces.
“Bigger animals have longer faeces, but also thicker mucus, enabling them to achieve high speeds with the same pressure. Without this mucus layer, defecation might not be possible.”
The scientists say their observations helped in designing an adult diaper for astronauts to use in space – which was one of the semifinalists in Nasa’s Space Poop Challenge.
The team believes their research could also help in diagnosing problems in the digestive system using non-invasive procedures that do not involve sending cameras down the intestine.
The research is published in Soft Matter.