The study, led by researchers at the University of Michigan and published this month in the journal Communications Earth & Environment, analyzed decades of wildlife tracking data collected by state agencies across the Mountain West.
Researchers examined the movements and habitat use of mule deer, black bears and cougars. They found that severe drought reduced the amount of high-quality habitat available to all three species.
“And it seems like the effect of drought on habitat is actually worse the higher up the food chain that you go," said Neil Carter, an associate professor at the University of Michigan's School for Environment and Sustainability and the study's lead author.
During severe drought conditions, the amount of highly preferred habitat declined by about 10% for mule deer, 14% for black bears and 18% for cougars.
"Cougars lost nearly twice as much suitable habitat as mule deer during those drought years," Carter said.
The findings suggest drought's effects can ripple through entire ecosystems. As vegetation dries out and forage becomes less abundant, herbivores such as mule deer have fewer options for food and water. Those changes can then affect predators that depend on them.
The study also found severe drought can have significant consequences for mule deer populations. During the most extreme drought periods, fawn recruitment — a measure of how many young deer survive and join the population — dropped by more than one-third.
"That's population-level concern," Carter said. "That's alarm-bell-level concern for thinking about the trajectories for deer."
Carter said the project relied on thousands of collared animals and extensive collaboration among wildlife managers and scientists. The findings arrive as much of the West continues to grapple with rising temperatures, changing precipitation patterns and increasing pressure on water resources.
Carter said the results could help wildlife managers better prepare for future droughts by identifying and protecting the habitats animals rely on most when conditions become harsh.
This story was produced by the Mountain West News Bureau, a collaboration between KUNR, Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNC in Northern Colorado, KANW in New Mexico, Colorado Public Radio, KJZZ in Arizona and NPR, with additional support from affiliate newsrooms across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting and Eric and Wendy Schmidt.
