UW Researchers Investigate Impact of Squirrels on Ecosystems, Conservation Strategies

At the University of Wyoming, John Koprowski -- a leading expert on squirrels' ecology, conservation and management -- and his lab group are exploring the impact squirrels have on their environment, as well as approaches to conservation that provide sustainable solutions.

"Everyone knows what squirrels are, and they're a great way to communicate science and connect with everything from little kids and elementary school projects to retired folks in cities and rural areas," Koprowski says. "Pretty much anywhere in the world, someone will have stories about squirrels."

Squirrels can be used as examples of how topics such as urbanization, deforestation, climate challenges and habitat quality are important, he says. And studying squirrels and other animal species as indicators of change and conservation solutions -- in the best locations for specific research both nationally and internationally -- could lead to adoptable conservation strategies.

Koprowski's work with squirrels goes back decades to his time as a student at Ohio State University and continues with his new book "Squirrels of the World 2," publishing soon with Johns Hopkins University Press.

Koprowski also is involved in a long-term project on Mount Graham Red Squirrels that he began working on during his time at the University of Arizona. This research has been using radiotelemetry and long-term, live mark-and-release trapping to monitor the critically endangered squirrel species for the past 26 years. He also has international squirrel research collaborations in Italy, Mongolia, South America, Mexico and South Africa.

Koprowski's lab -- the Koprowski Conservation Research Laboratory -- is part of Help Save Wildlife, his larger conservation group that includes researchers at UW's Haub School of Environment and Natural Resources, and the School of Natural Resources and the Environment at the University of Arizona. The group's interest lies "in conservation approaches that involve local people to find sustainable and durable solutions," says Koprowski, the dean of UW's Haub School.

At UW, two of the major research projects under Koprowski exploring the importance of squirrels in their natural habitat are led by UW graduate students Lindsey Mitchell, a third-year master's student from Colorado Springs, Colo., and Ph.D. student Lauren Wetterau, of Columbus, Ind.

Koprowski, who serves as their adviser, sought funding and matched Mitchell and Wetterau to their projects -- topics he had interest in, he says.

How Squirrels Co-exist and May Indicate Forest Health in Borneo

Mitchell's research, which began in fall 2024 following her time as an undergraduate technician in Koprowski's Lab at UW, is studying how a large number of squirrel species on the island of Borneo co-exist in its remaining forest fragments and their potential as indicators of rainforest health, she says.

Borneo's rainforest is highly threatened, largely because of oil palm expansion, Mitchell says. Her study area -- the Lower Kinabatangan Wildlife Sanctuary -- is a protected area along the Kinabatangan River, and it is surrounded by oil palm plantations.

"This pushes all the amazing wildlife to these protected areas, which now have to support large numbers of species ranging from tiny pygmy squirrels and treeshrews to Bornean orangutans and Bornean elephants," Mitchell says. "Across the Kinabatangan floodplains, over 80 percent of natural forest has been converted to agriculture."

For her research, Mitchell spent a total of eight months in Borneo -- four months in 2025 and four months this year -- studying approximately 15 species, which have limited studies conducted on them. At the Danau Girang Field Centre in the wildlife sanctuary, Mitchell worked with Benoit Goosens, director of the field center and a professor in the Organisms and Environment Division in Cardiff University's School of Biosciences, as well as professional training-year students, volunteers, staff, field assistants and researchers for varying aspects of the project.

Mitchell's research is an example of community-based conservation that involves local people to find sustainable solutions, Koprowski says, also mentioning there are efforts to reforest areas in Borneo.

"Squirrels tell us early indicators of 'Oh, the habitat is changing,' before we can see that as humans, or they can be an indicator of 'Ah, this habitat truly is recovering because this species of squirrel is starting to show up again in the forest,' for instance," Koprowski says. "So, often we're looking at those kinds of questions of change in habitat quality, habitat fragmentation, habitat connectivity and what can animals tell us about how well we're doing as stewards of the land as humans."

There are more than 30 squirrel species on Borneo, and those in Mitchell's studied area ranged in size from the Bornean pygmy squirrel, weighing around 0.525 ounces, to the giant squirrel, weighing around 2.64 pounds, she says.

During the study, data-gathering methods included: camera trapping squirrels; live-trapping squirrels to record body measurements; collaring certain species with very high frequency, trackable radio collars; and conducting habitat assessments to measure things such as canopy cover and understory vegetation density at camera trap locations.

The most useful data gathered -- answering both how squirrel species co-exist with other species in the area and if they could be indicators of rainforest conditions -- were the camera traps, Mitchell explains.

The camera traps, paired with habitat surveys, provided information such as what species are present and where; if any vegetation characteristics are related to the absence or presence of certain species; and when species are active during the day.

The camera data also was examined to see whether a species was associated with measures that indicated forest quality, such as canopy cover or the number and diversity of trees in an area.

Six different species of squirrels were recorded on the camera traps throughout the sanctuary, Mitchell says. One of these species, the Bornean pygmy squirrel, is listed as data-deficient by the International Union for Conservation of Nature, meaning there's not enough existing data to know if the species population is stable, or its current trends, Mitchell explains. An additional part of her research aimed to address some of the knowledge gaps on this species by collecting behavioral data and observing the characteristics of the trees the species used.

Mitchell is now working on data analysis. As results become available, they can be viewed on her research Instagram at lindseys.wildlife where fun facts and pictures of a variety of the species she studied can be found. Publications should be released sometime this spring, she says.

Red Squirrels Aid Biodiversity in Greater Yellowstone Ecosystem

Wetterau's research, which began in January 2024 while she was a master's student at UW, was published as her thesis July 20 and took place in the greater Yellowstone ecosystem.

Wetterau examined how North American red squirrels influence biodiversity in their ecosystem for her thesis, "Effects of red squirrel middens on biodiversity in the Greater Yellowstone Ecosystem."

UW undergraduate students Grace Peters and Jacqueline Hand, both seniors at UW from Rapid City, S.D., served as field technicians on the study. Sophie Nowak, a junior from Hartland, Wis., assisted with sorting camera data.

She found red squirrels' larder hoarding behavior, and the middens they create -- a central location storing conifer cones for the winter -- attracted various species of animals to the middens more often than other forest locations, increasing biodiversity.

Middens -- piles of scale cones built over generations and used to store cones for the winter -- are nutrient hotspots that create higher species richness and evenness than at other forest locations. Species richness is a greater variety of species; species evenness is the number of different species and how evenly they are distributed, Wetterau says.

The species' evenness and richness demonstrate higher biodiversity, "an important metric of ecosystem health and functioning and resilience," Wetterau says.

Wildlife groups found at the 70 studied middens included a high frequency of small rodents, such as Northern flying squirrels, Western deer mice and chipmunks, and predators such as Pacific martens and long-tailed weasels. The presence of these predators likely indicates they are hunting or foraging at these middens, due to the frequency of time they choose to spend there, Wetterau says. These predators also are known to live around middens, using them not only for predation, but also for thermal regulation.

This shows that, through middens, red squirrels contribute to predator-prey interactions and "facilitate the flow of nutrients from cones to rodents to predators," Wetterau says.

Middens also keep the cones cool and moist, allowing them to remain edible in the winter. And when the squirrels are gathering cones, not all the cones make it back to the middens or are eaten, Koprowski says, which can lead to the planting of trees.

The findings -- which are in line with Koprowski's interest in animals as indicators of change and for conservation strategies -- can likely be applied to other systems and wildlife communities where red squirrels are found with different species, with the assumption that similar effects would be observed, Wetterau says. While every species is different in how it moves across the landscape, this information could be useful to demonstrate the effects middens may have across their range.

Squirrels are an easy animal for people to think about as an indicator of change and as a species to co-exist with, Koprowski says.

But they aren't the only indicators of change. Some of his other research includes leopards and tigers in India and Nepal -- which present more challenges than squirrels -- as well as other species that are of conservation concern or can serve as indicators of positive or negative change in ecosystems.

For more information on Koprowski, Mitchell and Wetterau's research on squirrels or on the collaborative research on animals as indicators of change and co-existence/conservation strategies, visit https://helpsavewildlife.org/.

For more information on the Haub School, visit www.uwyo.edu/haub/index.html.