RENO, Nev. (KOLO) – A newly published study by researchers at the University of Nevada, Reno, sheds light on how bears choose their homes.
As winter inches closer in the Sierra Nevada, black bears are on the move looking for the perfect place to hibernate. And, like their human neighbors, the region’s black bears are searching for winter homes that are safe, warm and good places to get youngsters started in life.
“When they put tracking collars on the bears you get the advantage of a lot more data,” begins Heather Reich, a wildlife biologist with the study.
Reich and Kelly Stewart were two of the researchers on this project. They analyzed data collected since 1997 to give us new insight into these winter rituals. They say the findings are crucial due to our changing climate and evolving urban areas.
“It’s nice to have this baseline data to see what they’re selecting now, and as we get further into the future, seeing how things change,” said Stewart. Not just with the climate, but with expanding human development and how that is impacting where bears sleep for the winter. Eventually, maybe it even gets too warm and they don’t really do that.”
Among the key findings in the study are that female bears den earlier, and stay longer, than the males.
“The females probably came out later because they were waiting for the cubs to be ready to move on,” Stewart explained.
For Stewart, there was one particular habit by males that surprised her in the study. Male black bears apparently begin to stir out of their dens when day and nighttime temperatures remain above freezing, but temperatures don’t appear to be a big factor in female decisions about departure. Den locations aren’t reused from one year to the next. Instead, bears select a new den each year. For both males and females, den types are often similar. Rugged terrain and secluded spaces are preferred with hollowed trees or rock piles serving as shelters. This includes natural bedding the bears would use like pine needles, sagebrush, and leaf litter. But it was the location that the researchers found would sometimes differ.
“Females really liked steeper slopes. Males stayed away from roads to be away from disturbance. It looked like females were avoiding males and tended to stay closer to the road,” Stewart said.
According to Reich, black bears had largely disappeared from our region by the early 1900s after forests were cleared to meet the demands of the mining industry, and bears were hunted aimlessly. Today, black bear populations are being reintroduced, now going as far east as the Hawthorne area. This is something she says will also help to figure out habitat needs.
“With Nevada having so much public land, we have multi-use land sites that bears are using for their dens. So, future management plans may be able to incorporate the data from this publication to help with some of those decisions,” Reich said.
The foundation for the new analysis of bear dens came from data painstakingly collected by the Nevada Department of Wildlife from 2011 to 2022. It identified 116 den sites in the region after putting GPS collars on bears and tracking when they stopped moving about during the winter and stirred again in the spring.
The University researchers visited 26 den sites in the Sierra Nevada, Pine Nut Mountains, and Virginia Range. They carefully detailed the topography, vegetation, and concealment at each location.
Stewart, who also conducts research as part of the university’s Experiment Station, said the ongoing close cooperation between the University’s Department of Natural Resources & Environmental Science and the Nevada Department of Wildlife is among the elements that have built the department’s strong reputation.
“Our students have the opportunity for a lot of hands-on experience that supports what they learn in the classroom from our excellent faculty,” she said. “When our students present at conferences, we often hear that their work is some of best.”
Contributors to the bear-den research included Morgan Long, a graduate student, and Kevin Shoemaker, an associate professor, in the university’s Department of Natural Resources & Environmental Science; Carl Lackey, a bear biologist with the Nevada Department of Wildlife; and Jon Beckman, an adjunct faculty member of the university and a wildlife supervisor with the Kansas Department of Wildlife & Parks.
Funding for the research was provided by a grant from the Nevada Wildlife Record Book Foundation.
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