Scientists look into how animals pee and they have a good reason for that


A new study conducted by scientists has found that all animals ranging from as small as cats to elephants, which weigh over 6.6 pounds, take approximately 20 seconds to pee.

The study conducted by Georgia Tech University suggests that a connection exists between gravity and how animals urinate, thanks to the urethra.

The study examined the speed at which 32 animals urinate and discovered that it was the same. Interestingly, even though at 18 liters, an elephant's bladder is 3,600 times bigger than that of a cat's (5 milliliters), both the animals are able to urinate in 20 seconds. Moreover, the study discovered that all animals that weigh more than 6.6 pounds urinate in the same duration.

So how is this possible despite the disparity in size you ask?

"It's possible because larger animals have longer urethras," explains David Hu, assistant professor at Georgia Tech, who led the study. "The weight of the fluid in the urethra is pushing the fluid out. And because the urethra is long, flow rate is increased."

Per researchers, gravity has an effect on the speed of the urine flow in animals. Bigger animals like elephants have longer urethras, which enables them to empty their bladder in jets. An elephant urinates at 4 meters/sec, which is comparable to the volume/sec of five shower heads.

"If its urethra were shorter, the elephant would urinate for a longer time and be more susceptible to predators," says Hu.

On the other hand, the urination of smaller animals is affected marginally by gravity and they urinate in "small drops" owing to "high viscous and capillary forces."

The team of researchers studied 16 animals relieve themselves in a zoo, as well as watched 28 YouTube videos depicting the same. The researchers realized that their findings can help engineers as one does not require external pressure to dispose fluids speedily.

Gravity helps the animals save energy per Hu. The study author also opines that systems for water tanks, fire hoses and backpacks can be built around this correlation to extract maximum efficiency.

The study has been published in the Proceedings of the National Academy of Sciences (PNAS).

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