Saturday, December 20, 2014

Mammals Pee for about 21 Seconds, Regardless of Volume or Size

Research has revealed that, regardless of the animal's size or the volume being excreted, most mammals take roughly the same amount of time - about 21 seconds - to urinate. Believe me, you've just become the most interesting person at the party. You're welcome.

Just think about that: a cat excretes about 1 teaspoon of urine in roughly the same amount of time as an elephant empties its 18 L (~5 gal) bladder!  How does this happen?  It's all in the urethra.
This research, led by mechanical engineer David Hu from the Georgia Institute of Technology, used high-speed cameras and flow-rate measurements on 34 different animal species at the Atlanta Zoo (and on YouTube).  The researchers found that all mammals that weighed above 3 kg (~6.6 lbs) urinated for 21 ± 13 secs.  This is only possible through the urethra, the tube connecting the bladder to the outside world, which acts as a flow-enhancing device.

All animals have urethras with a length-to-width ratio of 18. That means that larger animals have longer urethras, giving them more gravitational force and a higher flow speed to work with. With a higher gravitational force, this creates more pressure in the bladder, pushing urine out faster.  Meanwhile smaller animals have less gravity to work with, and the challenges of having more viscous urine, since their bladders can't hold as much water as larger animals.

While this may seem like another case of "pointless" research (which we love over here at Science Prose), Hu and his colleagues are planning to use these findings to diagnose urinary problems in animals, and to inspire the design of more efficient systems for draining large areas of water, like swimming pools.

So, will you be timing yourself next time you're in the bathroom?

1 comment:

  1. My cat pees way more than a teaspoon. I wish it was only a teaspoon. He is very old and goes on the kitchen floor.