We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What Surprising Bodily Function Do Most Mammals Have in Common?

Updated May 16, 2024
Our promise to you
WiseGeek is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WiseGeek, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Bodily functions may not be the most comfortable topic to read or talk about, but nevertheless, they are an important aspect of life. Although there are many differences in bodily functions among living creatures, when it comes to mammals, there is a surprising feature that most of them share – the amount of time it takes to empty their bladder. In fact, despite vast differences in size and anatomy, most mammals larger than a rat take around 21 seconds to empty their bladders.

The relative length of the urethra (the tube through which urine leaves the body) is the key to this common bodily function. According to David Hu, an assistant professor of mechanical engineering at the Georgia Institute of Technology, "all animals have urethras of the same aspect ratio: a length-to-width ratio of 18.” This means that animals with larger bodies have longer urethras, which increases the force of gravity, creating more pressure in the bladder and causing urine to push out faster. This is why an elephant can empty its bladder just as quickly as a cat.

Hu and a team of researchers studied the urination patterns of 34 different species via YouTube and at Zoo Atlanta, where they also collected 16 bottles of urine. They found that in small mammals like rats, the urination process occurs in a series of quick drops. By contrast, larger mammals all released jets and sheets of urine in a process that took approximately 21 seconds, regardless of the creature's size.

The science of urination:

  • The urethra is a flow-enhancing device. As urinary systems evolved, the urethra scaled up without its function being compromised.

  • Hu’s study could prove helpful for a range of applications, such as diagnosing urinary problems in animals and inspiring the design of hydrodynamic systems based on those in nature.

  • An elephant's bladder can hold up to 5 gallons (18 liters) of fluid.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Link to Sources
Discussion Comments
WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.