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Do Larger Animals Take Longer to Pee?

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A rhinoceros has a bigger bladder than a dog, and generates urine by the bucketful. So which animal spends more time peeing? Scientists from Georgia Tech figured that, in general, larger animals would pee for longer. To test their hypothesis, they set up high-speed cameras to record Zoo Atlanta animals as they “did their business,” and supplemented that footage with videos from YouTube. Altogether, they analyzed the urination of 32 different animals ranging in size from mice to jaguars, gorillas, and elephants. 

Surprisingly, it turned out that mammals which weigh more than 6 pounds urinate for roughly the same length of time, regardless of their size. That is, they pee for 21 seconds on average, give or take 13 seconds. “This invariance is noteworthy,” the scientists write in the study, which was published in Proceedings of the National Academy of Science, “considering that an elephant’s bladder, at 18 liters, is nearly 3600 times larger in volume than a cat’s bladder at five milliliters.”

The reason that an elephant can release the equivalent of nine large soda bottles worth of urine in the same amount of time that it takes a cat to lose a spoonful of urine boils down to flow rates. An elephant pees faster than a cat because its urethra—the tube that delivers urine from the bladder and out of the body—is wider. The elephant’s urethra is also longer, allowing the force of gravity to act more strongly on fluid flowing through it.  

Mice and rats and other animals weighing under 6 pounds don’t fit the 21-second rule, however. That’s because their urinary tracts are so small that they have to battle capillary action, which is the tendency for a fluid’s molecules to stick to themselves and to the walls of a container and flow upwards. The pee is more viscous, and moves so slowly that smaller animals can’t generate a jet of urine. Instead, the urine falls out in tiny droplets.

For the rest of the mammals, it’s not clear why the 21-second rule holds across animals with widely varying sizes. The researchers suggest that it is a matter of physics rather than evolutionary adaptation. 

The scientists say their research could be helpful in diagnosing urinary problems in animals. For instance, if a zookeeper notices a gorilla is peeing for a lot more or a lot less than 21 seconds, it could indicate that something is wrong.   

Oddly enough, this weird area of research could also have implications for infrastructure. From the paper:

[B]y providing a water-tight pipe to direct urine downward, the urethra increases the gravitational force acting on urine and therefore, the rate at which urine is expelled from the body.… Engineers may apply this result to design a system of pipes and reservoirs for which the drainage time does not depend on system size. This concept of a scalable hydrodynamic system may be used in the design of portable reservoirs, such as water towers, water backpacks, and storage tanks. 

Who knows, perhaps this research will pave the way for a “bladder” future. 

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Animals
This Beach Bar for Dogs Has Chicken Beer and Doggie Paddle Races
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After a summer spent playing fetch, sniffing butts, and fulfilling his duty as man’s best friend, your dog could probably use a vacation. There are few places where he’ll feel more welcome than at Monty’s Dog Beach Bar in Croatia. As Reuters reports, this canine-friendly oasis is the only bar of its kind in the Eastern European country.

Monty’s opened a year ago in the coastal town of Crikvenica and has been drawing in four-legged patrons and their owners ever since. While lounging on a sun bed with views of the Adriatic Sea, dogs lap up special "beer" brewed from chicken and vegetables. If they’re in need of something more substantial, the menu also includes ice cream made from bananas, peanut butter, yogurt, and soy milk. Senior dogs even have the option to drink medicinal teas that are supposed to boost fur growth. And if their humans get hungry or thirsty, there’s a full selection of people drinks and snacks to choose from, too.

Earlier in August, Monty’s hosted a day full of beach games that dogs and their owners could take part in together. Fifteen human-canine pairs competed in an event that had them running down a pier, leaping into the water, and swimming 100 meters back to shore. The winner, a four-year-old Samoyed mix named Nimbus, was awarded 15 pounds of kibble and a weekend stay at a nearby hotel.

The day also featured beer, ice cream, and cake-eating contests for dogs who preferred consuming calories to burning them off.

Special menu items for dogs have become a more popular sight at mainstream restaurants in recent years. Non-alcoholic beer for dogs, made from everything from dandelion to beef flavoring, is also easy to find if owners know where to look for it. But for a dog-centric bar experience close to the ocean, you may have to book a trip to Croatia. (Fido will thank you.)

[h/t Reuters]

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Microsoft’s Autonomous Gliders Stay in the Air by Mimicking Birds of Prey
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When designing different ways for vehicles to move, engineers will often look to nature. Animals have had millions of years to evolve locomotion methods that get them where they’re going fast without burning a ton of energy. Now, researchers at Microsoft have chosen the hawk, a master of energy-efficient air travel, as the model for their new autonomous gliders.

As Co.Design reports, the tech company’s “infinite soaring machine” can move through the skies without generating its own propulsion. Instead, it seeks out warms streams of air to provide the upward push, much like a hawk does.

While riding air currents doesn't take up a lot of energy, it does require some sophisticated artificial intelligence. As a substitute for millennia of animal instinct, Microsoft “trained” its glider to fly by plugging it into a video game-like simulator that showed hawks in flight. By repeatedly subjecting the technology to these virtual experiments, researchers eventually developed algorithms capable of recreating the scenes in the real world.

Using onboard sensors, the sailplane can independently navigate the skies without a motor. The gliders are no more than a few feet long, which means they don’t serve much of a practical purpose outside of research. But the aircraft’s simple design is exactly what makes them appealing to engineers.

With less hardware to worry about, they can focus on refining AI software which can be used in different types of autonomous vehicles in the future. And by testing AI navigation in the air instead of on the road, Microsoft gives themselves a much bigger test track to work with.

You can watch the infinite soaring machine take to the skies in the video below.

[h/t Co.Design]

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