Study: Mammals Big, Small Pee in About 21 Seconds

Above 6.5 pounds, urination duration doesn't scale with size

By Elizabeth Armstrong Moore,  Newser Staff

Posted Jun 26, 2014 8:38 AM CDT

(Newser) – Ever wonder why it doesn't take elephants an hour to pee? Well someone did. After studying mammals of all walks of life at Zoo Atlanta, scientists discovered that, aside from those that weigh 6.5 pounds or less, it takes the rest of us mammals on average 21 seconds to pee, give or take 13 seconds, reports Scientific American. Doesn't matter if it's a newborn human, a gorilla, or a giraffe; urination time is extremely consistent, something fairly remarkable when you consider an elephant's bladder is almost 3,600 times bigger than that of a cat. The reason, they surmise, is that even though bigger mammals tend to have bigger bladders, their urethra is wider and also longer, and thus—thanks to gravity—the flow is faster.

David Hu, the mechanical engineer who filmed the mammals at the zoo, tells the LA Times he got the idea a few years ago when he was changing his young kids' diapers and thought, "How could anything be worse right now?" Which was immediately followed by: "Well, maybe if I was changing an elephant’s diaper." After hours spent at the zoo (during which they collected urine in cut-up soda bottles during the act in order to measure flow rate), the researchers also learned that smaller animals, like rats, don't pee in a jet stream but rather in little "gumballs" of water dispensed one at a time; they lack the amount of liquid needed to create a real flow. It seems that 6.5 pounds is the tipping point, which is why a grown bear takes as long to pee as sweet little Toto. Hu notes that the study could have health implications for humans: If one's urination duration falls outside the norm, it could signal a medical problem. (Speaking of Toto, dogs appear to use Earth's magnetic field to poop.)

In an April 1978 photo, the baby elephant Little Diamond, with her mother, Toto, takes her first trip outside since she was born at the Knoxville, Tenn., zoo. The first African elephant bred and born in captivity in the Western Hemisphere, Little Diamond died Tuesday, June 17, 2014, at the...
In an April 1978 photo, the baby elephant Little Diamond, with her mother, Toto, takes her first trip outside since she was born at the Knoxville, Tenn., zoo. The first African elephant bred and born...   (AP Photo/Knoxville News Sentinel)
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