Last month, visitors to Washington’s Olympic National Park were treated to a surreal sight. A helicopter crossed the sky dangling strands of drugged, blindfolded mountain goats—as many as five at a time—like a string of furry pearls. In the end, more than 100 goats were airlifted from the park and shipped to new homes across the state, all because they loved human pee too much.

Lacking the dietary minerals they’d find in their natural range, park officials say some of the goats (which were introduced to the area in the 1920s) have become “quite aggressive” when seeking human sources of salt. Namely, urine.

“They learn that salt comes from people and people pee on trails, so they follow you down the trail and wait until you pee,” said Dr. Patti Happe, the park’s wildlife branch chief. “People think that goats are chasing them when really they’re just following them, waiting for a handout.”

But mountain goats aren’t alone in their quest for liquid gold. A surprising number of creatures—from reindeer to locusts—have a known affinity for human urine. And for some species, this craving for our minerals has dramatically shaped their behavior.

Salty ambrosia

All animals need sodium and chlorine—the chemical components of table salt, which are essential elements that regulate fluids and enable the transfer of energy—to survive. Carnivores and omnivores like humans can often meet this need by eating other animals. And when we have too much, our bodies secrete these elements as waste products: That is, we pee them out.

Plant-eating animals must turn to rougher fare. When the vegetation they live on doesn’t have the minerals they need, their only recourse is to eat dirt. Known as “geophagy,” this takes the familiar form of salt licking in large ungulates like cows and deer. Of course, not all soil is created equal. Wild ungulates are known to travel vast distances to reach naturally occurring mineral licks—and other animals will just as tenaciously seek out less geological sources of salt.

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When moths and butterflies gather to drink dirt through their straw-like proboscises, it’s known as mud-puddling. Some of the most attractive mud puddles are those created by animals seeking relief.

“Urine contains sodium, and sodium is thought to be a limiting ion in the diet of nectar-feeding [moths and butterflies],” said Dr. Michael Bodri, the dean of science and mathematics at the University of North Georgia. “It is primarily males that puddle, and there is evidence that they can transfer sodium to females when they mate, increasing their reproductive success.”

This fact—that gentle butterflies are often gripped by an unquenchable thirst for our whiz—has been a boon to butterfly collectors. But animal attraction to human urine isn’t just a bit of hobbyist trivia. Sometimes, it’s a matter of life or death.

Fatal attraction

According to Dr. Charles Stépanoff, an anthropologist at the École Pratique des Hautes Études in Paris, the Tozhu people of southern Siberia have long used urine to build relationships with the reindeer they rely on for survival. Apparently, by feeding Rudolph a kind of pee-pee popsicle.

“Tozhu men are used to urinating near the house, often on a hollow stump, or even in a urinal specially constructed for reindeer: a tree trunk with a trough carved in it, adapted to height of reindeer mouths,” writes Stépanoff in a 2012 journal article. “In winter, urine freezes immediately and is thus conserved in these urinals, so that when they come to the campsite, reindeer can easily lick it.”

Stépanoff’s paper also quotes Norwegian explorer Ørjan Olsen, who observed this fraternity of pee in 1914: “When they see a man urinating, reindeer come from everywhere to be sure to find their diet. By virtue of [their] intimate relationship with men, they are so gentle that you can often catch them with your hands.”

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In other animals, however, the result of this urine-seeking behavior is conflict, not companionship. In Olympic National Park, the situation better resembles a movie made by Wes Craven than Disney.

“If you get out of your tent in the middle of the night and don’t make it to the outhouse and just kind of step out and urinate, the goats are there all night long,” said Dr. Happe. “Eating down the mineral soil to get the salt that you’ve deposited.”

With stiletto-like horns and a decreased fear of humans, the park’s pee-crazy goats can even be deadly. In 2010, a 63-year-old hiker was fatally gored by a mountain goat in the park. For the goats, it’s more of a mixed bag.

Last year, researchers published a paper studying how mountain goats attracted to human urine in Montana’s Glacier National Park responded to predators. Donning a grizzly bear costume “constructed from a Styrofoam head and a furred fabric cape,” lead author Wesley Sarmento found that pee-licking goats didn’t flee as far from the faux bear as non-pee-licking, backcountry goats—so long as tourists were around.

The study’s results suggested that in addition to providing sweet, delicious urine, the park-goers acted something like a human shield against predators for the goats. For those seeking to maintain the historic distribution of mountain goats in the park, there are no easy solutions.

“[One] tactic could be to reduce benefits that lure wildlife to human locales,” writes Sarmento. “The provisioning of toilets would be a way to reduce human minerals, but it would also be logistically challenging as helicopters are required to remove backcountry waste.”

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When it comes to the urine-loving goats of Olympic National Park, which compete with native species in addition to threatening visitors, wildlife officials have opted for complete eviction and elimination. They say they will relocate as many of the remaining 600 or so goats as possible to their native habitats and remove the rest “by lethal means.”

The golden mean

In a world of almost 8 billion people, human urine is obviously abundant, but do nature’s pee junkies have any preference on how they get their fix?

A 2008 study on yellow-spined bamboo locusts, a major pest (and known pee fan) in China, found the insects strongly preferred human urine that had been incubated for three to six days. Clearly, some animals have a nose for a good vintage.

Dr. Bodri, who says he used to encourage students on study abroad trips to defecate in the forest so they could see how quickly feces were harvested for nutrients, had a different question: Do butterflies prefer the pee of some mammals over others?

“From observations that butterflies were attracted to urine, I became curious as to whether butterflies could discriminate among urine depending upon diet of the animal that urinated,” said Dr. Bodri. “To my surprise, temperate butterflies did discriminate.”

In a study published earlier this year, Dr. Bodri compared the appeal of carnivore, omnivore, and herbivore pee to butterflies in Georgia’s Piedmont region. For herbivores, he used cow urine from a nearby farm. For carnivores, he obtained cougar urine from The Pee Mart (which advertises itself online as “America’s First Discount Urine Store”). And the omnivore urine, well, was sourced locally.

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“I didn’t modify my diet,” said Dr. Bodri. “I eat a balanced diet that I felt was representative of an omnivore.”

The results were stark: 97 out of 117 pee-sipping butterflies chose to quench their thirst with cougar urine. A stunning outcome, given that all samples were expected to have a similar sodium content. By feeding butterflies pee, Dr. Bodri may have only deepened the yellowy mystery.

“The unanswered question is how they find sodium in the first place,” he said, “what attracts them?”

Other researchers have suggested butterflies use both visual and scent clues to locate mud puddles, possibly gaining protection from predators by visiting sites where other butterflies are already slurping. When stopping to drink urine, it seems, it’s safer to join a friend.

Our urine, ourselves

Ultimately, however, the animals that drink the most human pee might be humans themselves. A cursory internet search will turn up countless examples of people consuming urine for, um, recreational purposes, and numerous historical sources describe instances of so-called urine therapy: the medicinal use of pee.

British naturopath John W. Armstrong, who popularized urine therapy in the 20th century, even cited the Bible, which advises readers to “drink waters out of thine own cistern, and running waters out of thine own well.” (Most biblical scholars, it should be noted, find a different metaphor in this passage.)

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While human urine might not always be the drink of choice for salt-seeking animals, our personal stake in the matter makes their attraction to it particularly interesting. A field note from Spain published in Bee World shows how easily this fascination can develop into full-on inquiry:

On 10 December 1986, up to 55 [bumblebees] (queens and workers) congregated simultaneously to feed in a small ground area where human urine had been deposited a few hours before. To ascertain whether urine was actually the attractive agent, further urine was deposited on a second area 2 m away where no bumble bees were feeding at the time. On the next day, a similar concentration of bumble bees was observed feeding at this new spot.

Viewed from afar, the transfer of sodium between animals via urine can look like a shining golden circle, where predators eat herbivores containing salt, and herbivores in turn lick up excess salt urinated by predators. But once humans enter the picture, this somewhat idiosyncratic behavior can become troublingly dominant.

Speaking to the New York Times last year, Sarmento worried that mountain goats habituated to people and their pee could lose knowledge of natural mineral lick sites. “If mother goats aren’t passing that behavior onto their young,” he said, “they might lose a migration that has accrued for thousands of years.”

In urine as in everything else, we must conclude, there can be too much of a good thing.