PHOENIX — Arizona’s fourth-hottest summer on record is proving fatal for even the most resilient desert species, as saguaros and rattlesnakes are dying in alarming numbers amid prolonged and extreme heat.
The saguaro cactus, a symbol of the Southwest and found only in the Sonoran Desert, is showing signs of stress and sharp population decline. Researchers at the Desert Botanical Garden say mortality rates have jumped from 1 to 2 percent annually to nearly 7 percent in recent years, due in large part to extended heat waves and high nighttime temperatures that interfere with many plants’ natural respiration.
Rattlesnakes are also facing conditions that may exceed their physical limits. Mike Cardwell, a consulting wildlife biologist who has tracked rattlesnakes in Arizona for more than 25 years, said two adult Western diamondbacks failed to emerge after the record heat in July 2023 — a first in his decades of study.
“Those snakes stayed underground during the hottest stretch and never came back up,” Cardwell said. “If it’s happening to rattlesnakes, it’s hard to imagine it’s not happening to other species as well.”
Rattlesnakes are ectothermic, meaning they depend on environmental temperatures to regulate their body heat. Their ideal temperature range is between 80-85 degrees Fahrenheit. Hence, they stay in burrows during the day and hunt at night.
Elijah, a venom keeper at the Phoenix Herpetological Sanctuary, said extreme nighttime temperatures prevent snakes from hunting safely, leading some to die from starvation rather than heat exposure.
“When it stays hot for days on end, they just don’t move. And if they don’t move, they don’t eat,” he said.
Cardwell added that during the July 2023 heat wave, ground temperatures remained dangerously high for extended periods, in some cases reaching lethal thresholds for snakes buried underground.
Biologists warn that the decline of one species can disrupt an entire ecosystem. Snakes help control rodent populations, while saguaros provide food and shelter for birds, insects and pollinators. The loss of either could set off a chain reaction throughout the desert food web.
Cardwell said the signs of ecosystem stress are accelerating and may already be past a tipping point.
“The process has been slow, but it’s speeding up,” he said. “I think we’ve been at the tipping point for several years.”
With rattlesnakes increasingly seeking water and cooler shelter in residential areas, Elijah urged residents to remain calm and call wildlife professionals for relocation.
“Even the little guys play a big role in keeping everything around us in balance,” he said.
