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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
Scientists Discover 'Octlantis,' a Bustling Octopus City
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Sylke Rohrlach, Wikimedia Commons // CC BY-SA 4.0

Octopuses are insanely talented: They’ve been observed building forts, playing games, and even walking on dry land. But one area where the cephalopods come up short is in the social department. At least that’s what marine biologists used to believe. Now a newly discovered underwater community, dubbed Octlantis, is prompting scientists to call their characterization of octopuses as loners into question.

As Quartz reports, the so-called octopus city is located in Jervis Bay off Australia’s east coast. The patch of seafloor is populated by as many as 15 gloomy octopuses, a.k.a. common Sydney octopuses (octopus tetricus). Previous observations of the creatures led scientists to think they were strictly solitary, not counting their yearly mating rituals. But in Octlantis, octopuses communicate by changing colors, evict each other from dens, and live side by side. In addition to interacting with their neighbors, the gloomy octopuses have helped build the infrastructure of the city itself. On top of the rock formation they call home, they’ve stored mounds of clam and scallop shells and shaped them into shelters.

There is one other known gloomy octopus community similar to this one, and it may help scientists understand how and why they form. The original site, called Octopolis, was discovered in the same bay in 2009. Unlike Octlantis, Octopolis was centered around a manmade object that had sunk to the seabed and provided dens for up to 16 octopuses at a time. The researchers studying it had assumed it was a freak occurrence. But this new city, built around a natural habitat, shows that gloomy octopuses in the area may be evolving to be more social.

If that's the case, it's unclear why such octo-cities are so uncommon. "Relative to the more typical solitary life, the costs and benefits of living in aggregations and investing in interactions remain to be documented," the researchers who discovered the group wrote in a paper published in Marine and Freshwater Behavior and Physiology [PDF].

It’s also possible that for the first time in history humans have the resources to see octopus villages that perhaps have always been bustling beneath the sea surface.

[h/t Quartz]

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Criminal Gangs Are Smuggling Illegal Rhino Horns as Jewelry
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Valuable jewelry isn't always made from precious metals or gems. Wildlife smugglers in Africa are increasingly evading the law by disguising illegally harvested rhinoceros horns as wearable baubles and trinkets, according to a new study conducted by wildlife trade monitoring network TRAFFIC.

As BBC News reports, TRAFFIC analyzed 456 wildlife seizure records—recorded between 2010 and June 2017—to trace illegal rhino horn trade routes and identify smuggling methods. In a report, the organization noted that criminals have disguised rhino horns in the past using all kinds of creative methods, including covering the parts with aluminum foil, coating them in wax, or smearing them with toothpaste or shampoo to mask the scent of decay. But as recent seizures in South Africa suggest, Chinese trafficking networks within the nation are now concealing the coveted product by shaping horns into beads, disks, bangles, necklaces, and other objects, like bowls and cups. The protrusions are also ground into powder and stored in bags along with horn bits and shavings.

"It's very worrying," Julian Rademeyer, a project leader with TRAFFIC, told BBC News. "Because if someone's walking through the airport wearing a necklace made of rhino horn, who is going to stop them? Police are looking for a piece of horn and whole horns."

Rhino horn is a hot commodity in Asia. The keratin parts have traditionally been ground up and used to make medicines for illnesses like rheumatism or cancer, although there's no scientific evidence that these treatments work. And in recent years, horn objects have become status symbols among wealthy men in countries like Vietnam.

"A large number of people prefer the powder, but there are those who use it for lucky charms,” Melville Saayman, a professor at South Africa's North-West University who studies the rhino horn trade, told ABC News. “So they would like a piece of the horn."

According to TRAFFIC, at least 1249 rhino horns—together weighing more than five tons—were seized globally between 2010 and June 2017. The majority of these rhino horn shipments originated in southern Africa, with the greatest demand coming from Vietnam and China. The product is mostly smuggled by air, but routes change and shift depending on border controls and law enforcement resources.

Conservationists warn that this booming illegal trade has led to a precipitous decline in Africa's rhinoceros population: At least 7100 of the nation's rhinos have been killed over the past decade, according to one estimate, and only around 25,000 remain today. Meanwhile, Save the Rhino International, a UK-based conservation charity, told BBC News that if current poaching trends continue, rhinos could go extinct in the wild within the next 10 years.

[h/t BBC News]

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