Study: Small mammals are climbing higher in Colorado's Rocky Mountains to flee warming temperatures

Posted at 9:16 AM, Feb 16, 2021

Small mammals in the Rocky Mountains are starting to move uphill to flee warming conditions, according to new research published last week.

Christy McCain, an associate professor in the Department of Ecology and Evolutionary Biology at the University of Colorado Boulder, led the study. The findings were published in the Ecology Society of America's journal, titled "Ecology."

The study spanned more than a decade and included 47 species of Colorado rodents and shrews. It found that the animals are moving uphill to avoid rapidly warming temperatures brought on by climate change.

The team of researchers found on average that the small mammals shifted their homes by more than 400 feet up in elevation since the 1980s. Some moved much higher, such as the golden-mantled ground squirrel, which moved up by 1,100 feet on average, the study found.

These changes, should they continue, may eventually squeeze the animals out of the state entirely. McCain said this is a frightening prospect.

“We’ve been talking about climate change in the Rockies for a long time, but I think we can say that this is a sign that things are now responding and responding quite drastically," she said.

The study began in 2008, when McCain and her team visited several sites around the Front Range and San Juan Mountains to collect records of the ranges of 47 species of small mammals. They compared their findings to about 4,500 historic records from museum collections dating back to the 1880s.

These results varied. Some animals moved farther downhill, others moved up, and some species increased their range when compared to the 1980s data. However, most of the surveyed species had moved uphill.

For example, the pygmy shrew was never spotted above 9,800 feet in elevation before 1980. But today, they're often seen at 11,800 feet, if not beyond.

McCain said this data paints a stark picture.

“It’s a wake-up call,” she said. “We have to start taking this seriously immediately if we want to have healthy mountains and ecosystems.”

Tim Szewczyk, a former graduate student at CU Boulder now at the University of Lausanne, and Sarah King of Colorado State University both contributed to this story.

Click here to read the study in "Ecology."