In 2015, mechanical engineers at Georgia Institute of Technology calculated that all mammals take about the same amount of time to empty their bladders: roughly 21 second of urinating. With the finding, they won an Ig Nobel prize—parody Nobel awards given to comical, yet interesting research.
In pursuit of further toilet tidbits—or perhaps another Ig Nobel—the researchers have now squeezed out a mathematical model of the hydrodynamics of pooping. And they’ve estimated that all mammals, big or small, void their bowels in 12 seconds, plus or minus seven seconds. Their findings were published this week in the aptly titled journal Soft Matter.
To come up with a universal deuce-dropping time, the researchers turned to YouTube, a dog park, and Zoo Atlanta. There, they filmed elephants, giant pandas, and warthogs producing bum brownies. In all, they collected 23 clips of pooping from 11 types of animals—which included cats, a mountain gorilla, lions, a black bear, zebras, a hippopotamus, and white rhinos, in addition to the others listed. It’s unclear if more data would alter their estimate of a universal time. They also eliminated power-poopers from the study, such as rabbits, rodents, and ruminants, which can serve up a bundle of turd pellets in short order.
To come up with a model that explained the evacuation times of the animals they did study, the researchers then collected fecal samples from 34 species at the zoo and other facilities. They dug into dung dimensions and composition, intestinal mucus, and rectal pressure. They also answered the question of “will it float?” Bears, tigers, and lions tend to push out sinkers, the researchers found.
They noted marked similarities between the species. Animals tended to produce two pieces of poo per go. Each piece was about the length of the animal’s rectum. This suggests that the colon stores a rectum-sized turd tube prior to evacuation. And that the turd length was about five times the diameter of an animal’s rectum.
Based on data from experiments involving inflating rectal balloons, the researchers estimated that animals use low-levels of pressure to poop. This suggests that the act of pooping is more like nudging pre-formed turd cylinders down a well-greased chute rather than squeezing amorphous toothpaste out of a tube.
The factor that keeps the poop times quick and relatively similar between species is the mucus, the researchers suggest. This helpful substance lubricates the bowel. And the largest animals, with more doo-doo to dump, have the thickest mucus layers.
With all the data, the researchers assembled a mathematical model to calculate evacuation times. It’s a wee bit crappy: the model estimated that the universal poop time was 5.6 seconds, not 12. But it did hold steady for animals of various sizes.
Patricia Yang, lead author of the study, speculated to New Scientist that the reason animals might have evolved similarly swift defecation times was to avoid lingering over a smelly deuce that could attract predators.