Big or Small, Mammals Take 21 Seconds to Pee

In what at first seems like some pretty pointless research, experts have discovered a surprising fact about urination: no matter the size of body or bladder, all mammals take just about the same time to pee.

That's at least according to a study recently published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), which reveals that housecats, dogs, and even elephants will all take an average of 21 seconds to answer nature's call.

That's a stunning revelation especially considering that a common elephant holds about five gallons (18 L) of urine in its immense bladder. Your average domesticated dog, on the other hand, can hold only about 1.3 tablespoons (20 ml) before it goes looking for the nearest fire hydrant.

Reason would say that it should take far less time to empty a 20 milliliter balloon than an 18 liter one, so what's going on? According to a team of researchers from the Georgia Institute of Technology, it really all comes down to the urethra - the "bendy straw" of the bladder.

According to the researchers, the urethra is much more than a universal means of urine expulsion among animals. It is, in fact flow-regulating and "flow-enhancing, enabling the urinary system to be scaled up by a factor of 3,600 in volume without compromising its function."

In an analysis uniting the results of 41 independent urological and anatomical studies, the researcher found that all mammals that weight more than 6.5 lbs have urethras with a length-to-width ratio of 18. Larger animals have longer and wider urethras, allowing them to take more advantage of gravitational forces to speedily empty their bladders within 21 seconds (give or take 13 seconds). Meanwhile an absence of this force makes it harder for smaller animals to empty their tiny bladders.

So mystery solved! However, one question still remains: why does this even matter? According to the authors of the study, these findings are actually very valuable to professionals in the veterinary world, where urination duration can help identify and diagnose health problems in animals.

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