Think there must be a big difference between the urination flow of an elephant and you? Researchers observed dozens of animal species and found regardless of the amount of fluid, it only takes 21 seconds for most mammals to urinate. They’re hopeful it will shed light on the mechanics of the endocrine system, according to the new study, which was published in the journal Proceedings of the National Academy of Sciences.

At the Zoo Atlanta, located in Georgia, researchers videotaped dozens of mammals, from elephants, to cats, cows, and goats. It all started when mechanical engineer David Hu was changing his child’s diaper and began to wonder how other mammals relieve themselves on a daily basis. “I was thinking, ‘How could anything be worse right now?’” Hu said. “And I thought, ‘Well, maybe if I was changing an elephant’s diaper it would be really bad.’”

All animals that weigh more than 6.6 pounds will take 21 seconds to pee, give or take 13 seconds. Smaller animals, such as rats had bladders so small they couldn’t hold a steady stream and instead produced “gumballs” of urine dispenses one by one. Humans and animals as small as cats produced enough urine to create a jet or stream. However, larger animals like elephants were able to fill up a kitchen garbage can with pee; all in the 21-second range. Collecting all of the urine itself in an accurate and measurable manner was no easy feat for researchers.

“We ended up cutting sections of soda bottles, because it has to be something you can hold by hand, and just at a second’s notice go on your hands and knees and hold it in the right position,” Hu said. “Everything else we tried failed. We tried pans — they don’t like pans, they think it’s weird. We tried pads — they don’t like pads, they think it’s weird.”

Researchers watched YouTube videos and reviewed scientific literature on the size of each species’ bladder, along with the length and width of the urethra, which is the tube that allows urine to leave the body. An elephant’s 18-liter bladder is nearly 3,600 times larger than a cat’s bladder, but it doesn’t take much longer than a cat to relieve itself.

Urination duration has an important place for health, Hu explained. Life-threatening illnesses such as prostate cancer, or obesity can put pressure on the urethra. Also, knowing how long animals urinate will give a healthy basis and help alert a problem if the duration goes over the average seconds.  

 

Source: Hu DL, Choo J, Pham J, et al. Duration of urination does not change with body size. Proceedings of the National Academy of Sciences. 2014.