Arizona’s Famous Horses Are Overheating

Close your eyes and think of the American West. What do you see? The sandstone towers of Monument Valley. The dusty ruts of a wagon trail leading through a clapboard town. A cowboy on horseback.

Remove the horse and the mythic image of the American frontier collapses. But across the desert states — and in particular, in Arizona, the cinematic ideal of the West — extreme heat is making the land practically uninhabitable for horses. In 2018, nearly 200 mustangs were found dead near a dried-up water hole on the west side of the Navajo Nation, and now, with 18 consecutive 110-plus degree days in Phoenix and counting, longtime equestrians in the state are considering hitching up the trailer and moving to cooler climes.

“Tonight I think it gets down to 87, just for an hour, and then it goes back up,” Quincy Roxburgh, who moved to the region from the Sacramento area and owns four horses, told me late last week. “We don’t get that break from the heat [like you do in California]. I feel so bad for the horses. I’ve never dealt with anything like this.”

With an estimated $1.3 billion local equestrian industry, Phoenix has been described as a “horse mecca,” particularly when it comes to Arabians. Every year the city hosts the biggest Arabian horse gathering in the world, drawing more than 2,400 horses with some $3 million in prize money on the line. WestWorld, the fifth most-popular equestrian facility in the country, is located in nearby Scottsdale — “the West’s Most Western Town” — and has undergone a $56-million renovation that included the addition of climate-controlled stalls. Its outdoor arenas, though, still bake in the heat. You begin to understand why equestrian events don’t typically get scheduled for the Arizona summers.

But that doesn’t mean much for the horses that spend the year in corrals nearby. Like most mammals, horses pant; unlike most mammals, when panting becomes ineffective around 94 degrees, they’ll sweat, similar to humans. And horses are enthusiastic sweaters: A horse can produce a quarter of a liter of sweat per minute in order to cool itself down, Equus reports — that is, about the capacity of one large Nalgene water bottle in the time it takes you to pop a bag of popcorn.

This means horses face the same risk as people when the air is humid and the efficiency of evaporation slows down. “The thing that saves us [in Arizona] is the low humidity, typically,” Roxburgh said.

In addition to being champion sweaters, though, horses are four-legged space heaters. Because they’re so muscular (and muscles produce heat), horses warm up three to 10 times faster than people do, Michael Lindinger, an animal and exercise physiologist at the University of Guelph, has found. According to his research, just 17 minutes of “moderate intensity exercise in hot, humid weather” can put a horse in the danger zone.

Even eating and digesting can warm a horse up. “Arabians, your Spanish-bred horses — heavy, big-boned warmbloods — we call those ‘easy keepers,’” Catherine Enright of Sorum Veterinary Services, in Scottsdale, Arizona, explained to me. “Those have a propensity to have more risk of foundering in this heat than other equine breeds.”

Founder — a heat-related hoof condition that can require euthanasia in extreme cases and that Roxburgh said she’s “scared to death” of — can be induced by something as ordinary and horsey as eating grass. As Enright explained, “if you have grass pastures, which are very hard to come by in Arizona, we recommend that you only graze [your horses] at night or very, very early in the morning, and they come in before noon,” when the sugar in the grass is highest. Because of the way a horse’s metabolism works, “sugar, starch, carbs — those three ingredients are a death sentence to easy keepers in this heat.”

Enright additionally suggested not letting horses out during the day — and indeed many horsemen and women across the Valley of the Sun have been rising pre-dawn to exercise and feed their animals. She also suggested putting up misters to help keep the horses cool. Roxburgh herself has invested in a large, SUV-sized swamp cooler for her horses, which she pointed out has the additional advantage of keeping her cool during barn chores.

But what about horses that don’t have access to tubs of water, misters, and even their own ACs?

The Phoenix area is home to some 430 wild horses that live along a river in the Tonto National Forest, on the northeastern outskirts of the city, beyond Scottsdale. That “wild” moniker is a bit of a contentious issue: The U.S. Forest Service claims the horses are “descended from … trespassing livestock” and thus they are not federally protected as “wild horses,” and the herd is instead overseen by a nonprofit, the Salt River Wild Horse Management Group, which contends the lineage goes back to the 18th century.

When I spoke to Simone Netherlands, the founder and president of the volunteer management group, I braced myself for the worst: horses without access to state-of-the-art barn misters dropping from the heat.

“I would say that the Salt River wild horses are the only ones not affected by the heat,” she told me instead.

In fact, her group is far more worried about keeping the rescue horses at its facilities cool. That’s because the Salt River herd “will stand in the middle of the river to cool off,” giving them enviable relief when the temperatures climb into the triple digits — “and so they’re the lucky ones.”

The way Netherlands tells it, it makes sense; the herd “evolved and learned to deal with the heat,” just like other desert animals do. The horses that can’t take Arizona’s seasonal extremes — like, say, the memorable 120-degree day last year that Netherlands, Roxburgh, and Enright all mentioned to me — are in theory weeded out, although Netherlands says they haven’t had a horse die from the heat since the monitoring group was established in 2015. Any culling was likely done generations ago: “That’s why we actually don’t have black horses in the Salt River herd, because they would not survive the heat,” she said.

Of course, not all horses are lucky enough to have a river flowing through their turf. Netherlands also told me that Arizona doesn’t have a law that specifically requires domestic horses be provided shade.

The heat is part of the myth of the West, too: The heat wave frying Phoneix has been called an endurance test, and it’s one many locals proudly embrace. “National media describe metro Phoenix’s string of 110-degree-plus days as if it were an apocalypse,” one recent editorial in the Arizona Republic boasted. “But we learned long ago how to adapt.” But unlike the wild horses, that adaptation involves easy access to AC, something that isn’t at the disposal of everyone, including outdoor domestic animals and the people who diligently labor — or were hired to labor — to take care of them.

And so, until the heat breaks, there will be more pre-dawn mornings, more calls to the overloaded vets, more barn misters to be installed. When saying farewell to Enright, I wished her, optimistically, cool days ahead. “Yeah,” she replied dryly. “There won’t be.”