Science often has a knack for asking the questions you didn’t know you wanted answered.
From the same team that brought you the knowledge that the majority of mammals pee for around 21 seconds, the researchers turned their attention to the other scatological habit. It turns out that the time it takes for most mammals to pinch one off is also strangely conserved across species. Whether it’s a human or a panda, most mammals spend roughly 12 seconds evacuating their bowels.
The fluid dynamicists joined forces with a colorectal surgeon to conduct an in-depth analysis of exactly how mammals manage to defecate. To do this, they collected evidence from the local zoo, not only filming 34 mammals as they relieved themselves, but also hand-picking the end products. The feces were then measured and tested for how the varying poop responded to applied force. From this, they were able to construct a mathematical model of the duration of defecation. Their results are published in the aptly named journal Soft Matter.
What they found was oddly fascinating. Despite elephant poop having a volume nearly a thousand times greater than that of a dog’s (20 liters versus 10 milliliters, in case you wondered), they still take around the same time to make the deposit, around 12 seconds plus or minus 7 seconds. The results are a bell curve, in that 66 percent of animals studied took between 5 and 19 seconds to defecate.
While bigger animals have correspondingly longer feces, the larger the creature the faster it shits. It turns out that an elephant poops at a speed of six centimeters a second, while a human takes things a little slower at two centimeters a second. There’s something you didn’t think you’d learn.
Regardless of size, all mammals take the same time to drop the kids off at the pool. Yang et al. 2017
This then raises the question of why. You see, despite the range in the size of the species, the researchers had previously discovered that the pressures exerted by different mammals while peeing is actually the same, and this holds true for pooping too. So the pressure a cat uses to defecate is roughly the same as that for a rhino, meaning that the speed they coil one out is not related to force.
The main reason for this is the mucus. Every mammal has a thin layer of mucus lining the large intestine, and this helps the feces evacuate the bowls with relative ease. The poop moves like a solid plug through the intestines, extending half way up the length of the colon. Larger animals simply have a thicker layer of mucus, allowing them to produce higher speeds of pooping, while exerting the same force.
The more you know.