A sweeping 12-year study of GPS-collared wildlife in Utah and Nevada reveals that drought is shrinking suitable habitat for mule deer, black bears and cougars — with top predators hit hardest. Researchers warn the trend could threaten wildlife persistence as droughts grow more severe.
When drought tightens its grip on the American Southwest, it isn’t just farmers and cities that pay the price. A new study led by researchers from the University of Michigan shows that large mammals — from grass-munching mule deer to apex predators like cougars — are losing significant chunks of their viable habitat as drought conditions intensify, and the animals at the top of the food chain are absorbing the worst of it.
Published May 25 in the journal Communications Earth & Environment, the research draws on 12 years of GPS collar data collected from more than 3,000 animals across nearly 200,000 square miles of Nevada and Utah between 2010 and 2022. The dataset — covering mule deer, black bears and cougars — is what co-lead author Martin Leclerc described as a “painfully massive” amount of information, and it enabled the team to track precisely how much suitable habitat each species occupied as drought conditions shifted over time and space.
What the Data Revealed
During severe drought conditions, every species in the study experienced at least a 10% reduction in the area of highly selected, or highly suitable, habitat. But the losses weren’t distributed evenly across the food chain. Mule deer saw their suitable habitat shrink by roughly 10%, black bears by 14%, and cougars by 18% — an escalating pattern that surprised even the researchers themselves.
Co-lead author Kirby Mills, formerly a postdoctoral researcher at the U-M Institute for Global Change Biology and now with the Institute for Wildlife Studies in California, emphasized the breadth of what the team uncovered.
“The take-home message is that the effects of drought are huge and widespread. These results aren’t just from one small study system,” Mills said in a news release.
The team also documented that, under extreme drought, the number of new fawn mule deer born per doe can drop by more than 30% — a statistic with stark implications for long-term population health.
“We found that drought was negatively impacting life across Utah and Nevada statewide for species that have very different ecologies,” Mills added. “We just looked at these three large mammals, but drought is probably affecting all the wildlife living in this region and could threaten their persistence into the future if droughts get worse.”
Leclerc, who co-led the study as a postdoctoral researcher at the U-M School for Environment and Sustainability and is now an assistant professor at the University of Quebec at Chicoutimi, stressed that the consequences extend beyond where animals choose to roam.
“What we’re seeing is that drought is having a major impact not just on habitat suitability, but also on fitness, on the survival of wildlife,” he said in the news release.
Why Predators Suffer More Than Prey
The counterintuitive finding — that cougars lose more habitat than deer even though drought primarily kills vegetation — comes down to dietary flexibility. As drought dries up plant life, deer can pivot quickly and forage on whatever remains green. Predators don’t have that option.
“Cougars can’t just go and chomp on whatever they find that’s green like deer can,” Mills said. “That means cougars have to work harder for their food and they’re more limited in their opportunities to find food, so their populations can be more sensitive to perturbations.”
Population density compounds the problem. The study tracked more than 2,800 mule deer but only 105 cougars, reflecting the natural reality that predator populations are smaller and less buffered against shocks. When individual cougars struggle, the ripple effects on the broader cougar community are proportionally larger than when an individual deer struggles within a herd of thousands.
Why It Matters for Conservation
The study arrives as Utah is currently among nine states entirely covered by some level of drought — a status that underscores just how immediate these findings are. Senior author Neil Carter, an associate professor at U-M’s School for Environment and Sustainability, emphasized the research demands a rethinking of how wildlife managers approach their work in a warming world.
“The study highlights the growing intersection of climate patterns, including drought and wildfire, with landscape planning and management, natural resource management, vegetation dynamics, wildlife behavior and management—all of these things that are often looked at separately,” Carter said. “Now we’re finding that they’re enmeshed so tightly and that demands different management strategies moving forward.”
One practical implication involves rethinking how game and wildlife agencies set their management priorities. Historically, deer populations have been managed largely in isolation. But if drought hammers cougar habitat 80% harder than deer habitat, managing one species without accounting for the other leaves a critical blind spot.
“People are typically managing deer populations, not deer and cougar simultaneously, so I think there will start to be more conversation and communication around that,” Carter added.
The findings also expose a broader gap in climate planning. Carter pointed out that while there are robust frameworks for helping human communities adapt to drought, no comparable infrastructure exists for wildlife.
“There’s pretty robust planning going on for mitigating human vulnerability to climate change, but we don’t have the same level of planning for mitigating wildlife vulnerability,” he said. “I certainly think there are opportunities to bring those together.”
The Role of Long-Term Data
The study would not have been possible without a coordinated multi-agency data collection effort. Co-senior author David Stoner, an associate professor at Utah State University, was credited with knowing which agencies and researchers to contact in order to stitch together records from many separate sources into a single coherent dataset. That collaboration made the 12-year, multi-species, multi-state analysis possible.
Leclerc reflected on what that kind of data infrastructure makes possible for addressing big-picture environmental questions.
“The study really shows the value and importance of long-term datasets, especially for big questions related to climate change,” he said.
For students studying ecology, environmental science, public policy, or conservation biology, this research illustrates how climate change operates as a multiplier — stressing ecosystems in ways that interact with and amplify one another, from vegetation loss to prey decline to predator vulnerability. Understanding those cascading effects, the authors argue, is essential for building management strategies that can keep pace with a rapidly shifting climate.
Source: University of Michigan