OK, I won’t keep you in suspense because I know you don’t trust me when I say it’s not gross. According to a new study, all mammals that weigh over 6.6 pounds, no matter what their bladder size is, can relieve themselves in about 20 seconds. I’ll wait until you run to the bathroom for verification.
Done? Was I right? Researchers at Georgia Institute of Technology observed 32 animals in a wide range of sizes urinating either live or on YouTube (who makes these videos?) and were surprised at the results. A cat’s bladder holds about 5 milliliters while an elephant’s holds 18 liters, yet both went approximately 20 seconds before saying “Ahh!”
Up until now, it was believed that muscle contraction on the bladder created pressure to force the flow of urine. David Hu, the Georgia Tech assistant professor who led the study, says it’s not pressure but gravity that causes the flow and the urethra’s length that gives the speed.
The study, just published in the Proceedings of the National Academy of Sciences, explains how an elephant can be finished so fast. An elephant’s urethra is one meter in length. The weight of the fluid pushes the urine out at four meters per second, or the same volume per second as five shower heads. Why is this a big deal? David Hu has the answer.
If its urethra were shorter, the elephant would urinate for a longer time and be more susceptible to predators. It turns out that you don't need external pressure to get rid of fluids quickly. Nature has designed a way to use gravity instead of wasting the animal's energy.
Applying this knowledge, Hu's students found that altering the length of hoses can make water tanks, water-carrying backpacks and fire trucks more efficient. The longer the hose, the faster it empties. Or as Hu puts it:
Nature has shown us that no matter how big the fire truck, water can still come out in the same time as a tiny truck.
Are you thinking about a “length of the hose” joke? Now THAT’S gross!