By 6:35 a.m., Ryan Vittetoe has already laid eyes on 75 of the 90 birds in his care. In the early August heat, already 95 degrees at this hour, starting the morning with a quick round of wellness checks is critical to making sure each of the 30 avian species housed along the Phoenix Zoo's Tropics Trail are thriving, not just surviving.

As he walks briskly between lofted enclosures, the zookeeper looks for signs of heat stress in his winged charges: open-mouth breathing, tucking down into the shade too early or acting in ways atypical to the behaviors he closely observes each week.

Birds, like dogs and many other animals, can't sweat, so they must rely on panting or seeking out water, mud or shelter to stay cool. Compared to the leafy, rainy forests these birds hail from, the natural desert environments surrounding Phoenix offer few of these three resources. So the zoo supplies them, plus more technological interventions to manage the escalating challenges of extreme heat.

That can mean the zookeepers take on a little more stress to reduce the heat stress of their animals. Vittetoe can now check temperature readings along the Tropics Trail from his phone. It allows him to monitor the conditions his birds are exposed to around the clock — including, sometimes, in the middle of the night when he jolts awake concerned about being too slow to react to out-of-whack temperatures, especially overnight lows that increasingly fail to drop as a result of atmospheric warming and urban development.

"This is what I wanted to do to help undo some of the damage that humans have done in the world," he says. "Humans have been able to adjust to climate change by going inside."

Outside the fencing of the Phoenix Zoo, 98% of human enclosures in the metro area have an air conditioning unit installed, allowing people who can afford to stay inside and keep it running to exist in a reality divorced from the high temperatures and heat waves that have been trending more intense and frequent over recent decades.

But for low-income or unhoused people and the animals and plants living in the wild, the challenges to cope have become difficult to ignore. Already this year, at least 150 people in Maricopa County have died from causes related to heat. And the skeletons of long-lived saguaros, many still propped up by two-by-fours across the Valley, that failed to outlast a record-breaking hot July 2023, are reminders that nature is not immune. Many desert landscapers are still scrambling to stem losses and devise better protections against the future heat extremes climate change has guaranteed.

Scientists say solutions include preserving more habitat and shifting from burning fossil fuels for energy, which emits heat-trapping greenhouse gases into the atmosphere, to running those air conditioners and other human inventions off renewable sources like solar and wind. That energy transition is underway, albeit slower than scientists advise is necessary. But with human expansion, pollution and extreme conditions also causing unprecedented biodiversity losses, these big-picture course corrections will come too late for species unable to adapt to the pace of change in their environments.

At the Phoenix Zoo and the Desert Botanical Garden, zookeepers and botanists who were already experts on heat are now figuring out responses to new levels of thermal stress to keep the animals and plants in front of them healthy day by day. In some cases, what they've learned is already benefitting conservation efforts near and far.

One week in the Phoenix heat:Living and dying in America’s hottest big city

Wednesday Adams: It's too hot to go outside

At 7:05 a.m., it's 97 degrees on the Tropics Trail despite the uncommon relief of scattered cloud cover. Vittetoe wedges his hand between fencing to double check that the misters and swamp cooler fans are working in the enclosures of his two most heat-sensitive species: the rhinoceros hornbill and the wrinkled hornbill. Sylvester, the zoo's sole rhinoceros hornbill, flies over to greet him.

When Vittetoe approaches the wrinkled hornbills, the nesting female, Wednesday Adams, stays true to her namesake and is less gregarious. Her beak barely pokes out from the insulated barrel the zoo team created to keep her and her chicks buffered from Phoenix's summer heat. As global average temperatures have soared in response to human-caused climate change, this barrel design has also been deployed in this endangered species' natural habitat in the tropical forests of Southeast Asia in a successful attempt to address the impact of heat stress on reproduction.

"A lot of bird species can be the first ones to experience the effects of climate change because their eggs are very sensitive to temperature," Vittetoe says. "They're also just not going to breed in high stress situations, they'll just sit there like a potato."

Standing about two feet tall with black and white feathers and a seemingly cumbersome bright orange casque — a French word for helmet that in avian terms refers to a dramatic beak ornament — these birds are especially vulnerable to heat because, as far as anyone knows, they don't drink water, a main method for mammals to regulate body temperature. Instead they get hydration from the fruit and small insects in their diet. Still, Vittetoe is careful to make sure these breeding birds have access to fresh water, just in case.

Seymour the Naughty Goat: Heat will make anyone misbehave

To cater to the dietary needs that keep animals hydrated and cool, the zoo has an $80,000-per-month nutrition services operation that works hard to pivot to the nuanced needs of animals existing in extreme heat. That team, run by Dustin Kinsman, arrives at the zoo each morning by 4:30 a.m. so crews can wheel out the carts of chopped fruit, vegetables, meat and frozen treats for zookeepers to pick up and start distributing at 5 a.m.

They prepare 700 different meals daily for the zoo's 3,000 animals, and are constantly adjusting protocols and inventory to respond to changing behaviors as temperatures rise. Kinsman recently ordered a second walk-in freezer to accommodate the need to have more options like frozen chicken broth and "bloodsickles" on hand for animals increasingly struggling to cool down.

"Currently, I think there's a goat or a sheep that's not doing well with the heat, so we've been cycling out more frozen buckets in here," Kinsman says on an early August morning, gesturing at an array of white plastic containers filled with frozen blood, broth and diluted Gatorade.

The goat struggling with Phoenix's midsummer heat is named Seymour, the very same bearded LaMancha once featured in a children's book sold in the zoo gift shop called "Seymour The Naughty Goat." At 8:20 a.m., zookeeper Amy Dannis leads Seymour from a sunny plat of the Red Barn petting zoo registering at 99 degrees into a shaded pen with its own fan, and pours him a dish of water mixed with red Gatorade. The animals like the red flavor best and purple least, she says.

At the ripe old goat age of 17, Seymour, like elderly humans, is more sensitive to the health toll of extreme heat. He also seems to be more vulnerable as a matter of individual variation, Dannis says. The keepers at the petting zoo check the air temperature once an hour and watch for signs the animals are trying to self-regulate, like when they start avoiding the visiting children. Research has linked heat to increased irritability in humans, and the petting zoo makes it clear this applies to nonhumans as well. To help the fuzzy friends reset, keepers bring them inside for frozen treats from Kinsman's kitchen.

Zebus get especially excited about this daily summer ritual. Dannis retrieves a frozen block of Gatorade and carrots from the Red Barn's freezer and throws it into the air in the zebu enclosure, where it shatters on the concrete and is descended upon by the humped cattle from Southeast Asia.

In addition to intervening when they seem to be struggling, Dannis says the zoo also tries to help its residents acclimatize slowly at the beginning of each summer. The importance of this practice was underscored recently when several mass howler monkey die-offs in Mexico were attributed to the formation of a heat dome made more likely by a warmed, chaotic atmosphere increasingly dishing out unpredictable and unseasonable weather extremes.

The zoo offers an opportunity for humans to manage more of these variables while studying how different species respond. The keepers set season-specific schedules for when to turn on fans and swamp coolers that help expose animals to warming conditions gradually, and they avoid introducing new animals to Phoenix during summer extremes.

"It's super important that, as we transition from spring to summer, that it's a slow transition," Dannis says. "Unexpected changes in the weather are hard to keep up with."

Chutti and Indu: Ready for their close-ups

By 9:10 a.m., temperatures at the Phoenix Zoo have crested into triple digits and Chutti the greater one-horned rhino is ready for his daily shower. Zookeeper Stevie Merner distracts all 5,500 pounds of the 9-year-old animal with fruit and vegetables prepared by Kinsman's team while keeper Leslie Lindholm hoses him off through thick metal bars.

"The unpredictability of the heat has definitely forced us to just be more creative," Merner says, offering a handful of food to the rhino's slobbery but gentle mouth. These days Chutti spends most of his time outdoors submerged in his enclosure's pool. The keepers monitor him for signs of additional heat stress, like panting or attempting to cover himself in mud, which Merner says can also act as a natural sunscreen and bug repellant.

Lindholm slides her hand into a 6-inch fold of Chutti's thick skin along his side as she looks for additional spots in need of cleaning. In the winter, the zookeepers tuck their hands into the rhino's tough, insulating flesh to warm their fingers, she says. It's harder to help Chutti keep these areas cool.

With this seemingly impenetrable skin, it's easy to see why greater-one horned rhinos have no natural predators in the wild. Humans hunting them for unproven medicinal properties of their horns or to keep them out of agricultural fields, however, landed them on the International Union for Conservation of Nature's Red List as a vulnerable species after their numbers dropped to around 200 at the start of the 20th century. Increased protections in India and captive breeding efforts in zoos helped bring the species back up to a current count of about 4,000.

But now the animals must contend with climate change. A 2020 study reviewing available evidence about the vulnerability of this species to warming temperatures concluded that conservation efforts for the greater one-horned rhino have not adequately incorporated risks posed by a changing atmosphere.

Recent research suggests that Asian elephants, which are endangered across their ranges in naturally-hot India and Southeast Asia, may also be susceptible to human-caused climate change. A 2022 study linked warming air temperatures to this species shifting north into cooler regions densely populated by people, introducing new conflicts and conservation management issues.

"Human-dominated areas became preferred habitats for elephants," the scientists concluded, noting that climate change is shrinking habitable space on the globe.

The Phoenix Zoo's resident Asian elephant is a 58-year-old flirt named Indu. Merner, who grew up in the West Valley visiting the Wildlife World Zoo in Litchfield Park before starting her keeper career, has developed such a close relationship with Indu that she tattooed the gentle giant's likeness on her forearm.

"It doesn't go unnoticed, climate change," Merner says. She hands Indu a last treat, then shows the elephant her bucket is empty. "It requires us to get creative. We have very opinionated and intelligent animals here and they will let you know what they want and need."

With the elephant already past her life expectancy, Merner is careful to make sure Indu has access to all summer heat precautions, including showers on demand, a new shade structure, constant access to a pool and Gatorade and an indoor enclosure kept at 80 degrees. She says Indu will sometimes go bang on the gate of that space, asking to be let back inside.

Undeterred by Merner's display that treat time is over, Indu uses her trunk to pick up a rock and offer it to another zookeeper standing nearby in hopes of a trade.

Operation Oryx: Reviving desert life

At 10:15 a.m., it's 102 degrees at the Phoenix Zoo. Drew Foster, director of living collections, drives a golf cart between exhibits, checking on his staff. During the extreme temperatures of July 2023, the zoo considered having workers start their days even earlier to ease heat pressure on both animals and humans, igniting debates about the definition of "civil twilight," when there's just enough daylight for keepers to see their wards.

The Phoenix Zoo also scaled back the hours it was open to the public, closing at 11 a.m. for several weeks last July, until pushback from members caused them to extend hours back to 1 p.m.

This year, zoo staff are closely monitoring both the timing and medical heat incidences of visitors, said Linda Hardwick, the zoo's director of communications. Park rangers hand out bottled Gatorade to weary humans, while Kinsman mixes up Gatorade concoctions for the animals and Foster makes the rounds ensuring everyone is functional.

Foster has worked at zoos in a variety of climates, including Santa Barbara, Chicago and the Bronx, each with their own obstacles to ensuring a good experience for all life forms involved. He started working at the Phoenix Zoo 13 years ago, in part because of the facility's pioneering work in desert wildlife conservation.

Operation Oryx was a 1962 international expedition to capture, breed and then reintroduce some of Arabia's few remaining wild oryx that had been threatened by trophy hunting, habitat destruction and the expansion of the oil industry. The success of the program, based at the Phoenix Zoo, was part of what drew Foster to the Sonoran Desert. The first generation of zoos in Arizona decades earlier, a recent article published in the Journal of Arizona History explains, featured mainstay animals of the region. Later, the state's zoos expanded to try to be a refuge for more unusual animals pushed out of their original habitats.

The Phoenix Zoo's current program for Mount Graham red squirrels, led by Director of Conservation Science Tara Harris, is an example of both. Native to a peak in southern Arizona that has experienced severe disruptions related to climate change, these shy rodents have been critically imperiled as warming temperatures push them higher up the mountain and stress the trees they nest in. The zoo studies these animals in captivity, helps track their numbers in the wild and maintains a special focus on species native to Arizona's diverse habitats.

"We try to house animals at the zoo that will thrive here. We would never acquire a snow leopard or polar bears," Foster says in response to a question about criticism Tucson's Reed Park Zoo once faced for hosting arctic animals.

Zoos have made mistakes as they attempt to balance serving the public interest with the best interests of individual animals and conservation overall, he says. But zoos also have a rich history of contributing unique intel on how to keep wildlife safe in environmental extremes. That role at America's hottest big-city zoo has never been more critical.

Cactus and agave: Don't forget the sunblock

Just after noon in early August, it's 103 degrees at the Desert Botanical Garden, a stone's throw across Papago Park from the Phoenix Zoo. It's time to take the daily surface temperature readings on the tops of saguaro cactuses botanists have covered in four different colors of shade cloth as part of a heat mitigation experiment.

Cactus specialist Noemi Hernandez points to several examples of succulents showing the yellowing, shriveled signs of "sun scorch" on the way to the newly-transplanted saguaros covered in black, green, tan or white landscaping cloth. Cactus can get sunburned too, it turns out. But visitors usually don't see it on display at curated botanical gardens, where protective tending and careful pruning prevent unsightly damage.

"Wild plants are constantly stressed, which is why they have that rough look to them," Hernandez says.

In July 2023, a record-breaking heatwave overwhelmed the botanists' ability to outsmart wild forces. The Phoenix facility lost at least 200 more plants than normal that summer, including many older, established saguaros that don't typically falter during extreme temperatures. The garden responded by creating a new heat mitigation group and launching this research on whether a lighter color shade cloth might be more protective. They also take care to not water midday, lest the liquid overheat in the soil and boil plant roots alive.

Now, each day when the sun is highest in the sky, Hernandez uses an infrared camera to capture pixelated thermal data from the surface of each experimental cactus as well as several control specimens nearby.

Starr Urbatsch, the garden's agave specialist, is testing the same theory on five agave species. She walks through the air-conditioned research lab to a gravel area behind the garden's public spaces where two dozen potted individuals from the group that includes the long-lived "century plant" sit covered by black, green, tan and white shade cloths. Mostly native to cooler, high altitude regions of Mexico, Urbatsch witnessed many of the garden's agaves seem to "melt" last summer, a first in her 23 years of experience.

"It's almost like their core just overheated, and oh my gosh, they just go" she says, imitating a limp plant arm drooping by flopping down her own limbs, before reaching down to right a pot that had fallen on its side. "That's something I really hadn't seen before."

Heat stress also took a visible toll on the garden's newest exhibit, which opened in April. Standing at the base of a 14-foot-tall tipuana tree planted in January, trail horticulture supervisor Tracy Rhodes says they had to take a "hail Mary" measure of draping the whole plant in shade cloth after it put out its first leaves in June, then lost all that growth when the greenery crisped up and dropped off after an inopportune heat wave the next week.

She's now experimenting with watering schedules and adding water-retaining mulch at the base of two of the four new tipuana trees to help them recover. But she didn't expect to have to worry about this species. After 11 years at the garden, she notices how worsening summer extremes are changing the desert horticulture game.

"The lengths plants have to go to avoid more water loss in the desert with increasing temps, over time that can really reduce the hardiness of the plant and its ability to take care of itself," Rhodes says. "We're now seeing cactus that we haven't typically seen showing signs of heat stress, like golden barrels. So that's definitely a bellwether of change."

'People think it's hard to kill a cactus. The truth is very different'

Back in the air-conditioned labs of the Desert Botanical Garden, Raul Puente-Martinez sits in his office surrounded by spines of dead cactuses that poke out from newspaper pages stacked between pieces of cardboard as a makeshift plant press.

As the curator of living collections at the garden, much of Puente-Martinez's research involves collecting cactus specimens to document their existing biodiversity, ranges and habitats in desert regions, so future botanists can have a better idea how this has shifted as a result of climatic change.

"People think its hard to kill a cactus," Puente-Martinez says. "The truth is very different."

Defying their reputation for hardiness, cactuses are actually particularly susceptible to increasing temperatures and drought, he explains, gesturing at nearby stacks of academic research papers on prickly pear. That's because they are old and slow — these plants first appeared in desert habitats 30 million years ago and, as species that go dormant during much of the year when resources are few and conditions harsh, their rates of evolution have not been able to keep up with that of the changes all around them.

"With certain cactuses, to go from a seed to full grown, you're talking probably 100 years," he says. "That's why desert plants are going to be the ones that are suffering most."

But Puente-Martinez is far from having given up hope. He oversees about two dozen other scientists in the garden's research department and herbarium. Part of this team's work involves maintaining a seed bank with a diversity of cactus embryos preserved at minus 20 degrees Celsius, for replanting in the wild in the event that future solutions to climate change allow for the eventual recolonization of lost habitats.

Puente-Martinez is also involved in an active project to reintroduce an endangered species, the Arizona hedgehog cactus, to its native habitat near Globe. The population was damaged by recent wildfires and has struggled to reclaim those rocky slopes in the midst of record-breaking temperatures and drought. The researchers have spent two years hiking plants they started from seed in the garden's greenhouse in to remote habitats in June, then hauling in 5-gallon jugs of water the young plants will need to develop lasting roots when summer monsoon storms fail to appear.

So far, they've planted 300 new Arizona hedgehog cactus plants in the wild and have a 90% success rate of keeping them alive. Last month, the botanists visited to find one had even sprouted seven new flowers.

"These are all the little things we can tell people about," he says, his voice quickening with enthusiasm. "And if we create this critical mass in the desert, that will be the response to climate change and the heat that we need."

Puente-Martinez pauses a moment in remembrance of this singular success story, the promise of seven endangered cactus blooms. Then he leans back in his chair and cracks a huge smile.

Joan Meiners is the climate news and storytelling reporter at The Arizona Republic and azcentral.com. Before becoming a journalist, she completed a doctorate in ecology. Follow Joan on Twitter at @beecycles or email her at [email protected].

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