I have always wondered in my shower-time thoughts what it’s like to pee for other animals, and do they feel the same feeling of relief we humans feel after peeing. That question might remain unanswered, but one other mystery has been solved.
Scientists have found out that almost all mammals weighing more than 1 kg take around the same time to urinate: an average of 21 seconds.
David Hu, a mechanical engineer at the Georgia Institute of Technology, was very intrigued by the science of urination and how urine is passed from the bodies of mammals. So he analysed the bladder capacities of different mammals. For example, a dog’s bladder can hold about 1.4 litres (or the size of a large soda bottle) while an elephant’s bladder can hold up to 160 litres (or the size of a large fish tank).
The reason why the duration of the pee is almost the same is because the size of the bladder and the length and width of the urethra increase as the size of the animal increases.
Hu and his group of students used high-speed cameras to shoot and study the footage of some test animals. His studies revealed that the size of the urethra plays a major role in eliminating urine and the force by which it does that. Hence, an elephant will take the same time to pee as a dog, but the force of both will be different. Hu paraphrased this as his Universal Urination Law.
Although Hu’s law does not apply to mammals weighing below 1 kg, he said that his findings can help solve urinary tract issues.
Animals like rats and mice could actually finish peeing in a second, because their bladder sizes are very small. Their amount of urination is merely a few drops. But animals weighing upwards of 1 kg seem to follow the same proportional trend of urinating for an average of 21 seconds, Hu noted.
This finding is a significant step in studying mammal bodies and how waste elimination functions.
Fact source: National Geographic
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