Minnesota’s southern flying squirrels glide north

Temperatures and habitat changes push species into ‘Zone of Sympatry’ with northern cousins.

If your knowledge of flying squirrels doesn’t extend much beyond Rocky (of the famous Rocky and Bullwinkle cartoon team), you’re not alone.

They’re small, nocturnal creatures that keep mostly to treetops – though they might glide into your backyard bird feeder on occasion. And, at least here in Minnesota, they’re not well studied. Meanwhile, Wisconsin and Michigan have listed flying squirrels as a “species of concern.”

Anna Mangan Headhsot
Anna Mangan

“We want to know the status of flying squirrels here,” explained NRRI Wildlife Ecologist and project lead Anna Mangan. “And we have this interesting situation where two species are overlapping in their range, so we want to understand how they’re competing for resources or if their populations are doing okay.”

Minnesota’s southern flying squirrels – a smaller, “yippier” species – prefer the deciduous forest landscape, especially for the nuts and acorns, fungi and seeds. The northern flying squirrels prefer the state’s boreal forests with spruce, pine and fir trees aplenty. But the Duluth area is within a sympatric zone – extending west toward Bemidji – where the two species are both present in mixed forest habitat. And it appears the southerns are pushing further north as a warming climate creates more favorable conditions.

Advancing Knowledge

Three graduate students are tackling different research angles to help understand these species. Katie Pfaff, in UMD’s Integrated Biosciences Program, is capturing, tagging and attaching tiny radio telemetry tracking collars to the “flyers.” She carefully and quickly handles each squirrel to get their weight and health data. 

[Watch a video of Katie Pfaff collecting flying squirrel data near the UMD campus.]

Working across several sites, the team ear-tagged nearly 100 squirrels and some 44 wearing trackers. Now the team is learning where the squirrels live, what they eat and how far they travel. Camera traps deployed in likely flying squirrel locations, like Jay Cooke Park, are also providing data.

“Katie is gathering data on how both species use their shared spaces,” explained Mangan. “What times of year are they most active? How do they use their habitat?”

Anthony Raona, a graduate student at Grand Valley State University in Allendale, Mich., is basing his master’s research on an intestinal parasite, Strongyloides robustus, found in southern flying squirrels without health impacts. But, studies elsewhere have found it can be detrimental to the northern species.

“It was a study back in the 1960s that found this parasite kills northerns but not southern flyers,” Raona explained. “So I’m interested in knowing if Strongyloides is moving up north with the squirrels and what that impact might be.”

A woman crouches in tall grass wearing a mosquito head net.
Anna Peterson wears insect protection in the field. (Photo: C. Kearns)

Anna Peterson started her second year in UMD’s Integrated Biosciences Program this fall. She’s gathering data on the distribution of flying squirrels statewide using previously gathered acoustic recordings and teasing out the ultrasonic squirrel sounds.

“The recordings were collected to get bat distribution data, but I can adjust the output for squirrels, which also vocalize in the ultrasonic range,” Peterson explained.

And she’s coupling that with finer scale distribution data with 100 acoustic survey sites set up in the Chippewa National Forest. She developed a “habitat suitability index” based on canopy cover, stand type, and stand age to determine low, medium and high quality habitat for each species.

“Previous studies have found that the southerns and northerns can coexist in the sympatric zone, but southerns are more aggressive and can push northerns out,” said Peterson. “But it will be interesting to see if that’s happening here.”

Squirrel in the Coal Mine

Tracking the changing distributions of flying squirrels is one key to unlocking a better understanding of how Minnesota's forests are changing. 

"Both species of flying squirrel are responding to changing conditions," Mangan said. "Understanding their responses gives us clues about what our future forests could look like and how they might function."

And even though flying squirrels are a species not many people see or interact with, they are important to the forest ecosystem. 

Close-up of flying squirrel in trap
Flying squirrel trapped for tagging and/or collaring. (Photo: A. Mangan)

“They’re seed and fungal dispersers, which are both important to forest health. They are also a food source for owls and other wildlife,” Mangan explained. “But biodiversity in general is important. Every species is important and flying squirrels are just fascinating.”

They’re small, fitting in the palm of your hand, with big nocturnal eyes, and use the patagium membrane stretched from hand to foot to glide between branches. Random fun fact: they also fluoresce hot pink in ultraviolet light. 

“And although there are some theories, no one knows why,” Mangan said. “Someone just discovered this five years ago randomly shining a black light around. It’s really fun to study a creature we know so little about.”

Information about how each impacts the forests and how they impact each other will help inform forest and wildlife managers at the Department of Natural Resources to determine best practices for Minnesota’s flying squirrel populations.

This two-year study will continue into summer 2025. It’s funded by the Minnesota Environmental and Natural Resource Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR).

Read about the NRRI-funded pilot study initiated in 2021: Southern flying squirrels are climate migrants.

PHOTO TOP: Anna Mangan checks a trap with flying squirrel. (Photo credit: Charly Kearns)