Evaluating Competition Between Sympatric Flying Squirrels (Glaucomys Spp.) In Northeastern Minnesota

Chapter 1: Climate change is causing unprecedented spatial overlap of previously allopatric species, which can lead to competition between species with similar niches. Northern flying squirrels (Glaucomys sabrinus) and southern flying squirrels (G. volans) have increasingly overlapping ranges due to warming temperatures across eastern North America, including northern Minnesota. We evaluated whether the two species spatially partition their home ranges within this emerging sympatric zone. Using radio telemetry, we tracked 20 individuals (12 northern flying squirrels and 8 southern flying squirrels) and estimated 95% MCP home ranges to compare sizes and overlaps across species, sex, zone of allopatry and sympatry. There were no significant differences in home range size by any metric, although we observed the trend that male home ranges were larger than female home ranges. We did not find evidence for spatial partitioning between species and observed high levels of home range overlap. Interspecific home range overlap was high and exceeded average intraspecific overlap. These patterns suggest substantial potential for hybridization, parasite transmission, and resource competition where the species co-occur. Our results provide new insight into how climate-driven sympatry shapes interactions between closely related mammals and can inform future monitoring and management of this dynamic contact zone. Chapter 2: Climate change affects the spatial distribution of northern flying squirrels (Glaucomys sabrinus or NFS) and southern flying squirrels (G. volans or SFS) across North America, including Minnesota, USA. Warmer winters have facilitated the northward movement of SFSs into areas that were previously occupied solely by NFSs, potentially leading to increased competition between the two species. Understanding how NFSs respond to the presence of SFSs in Minnesota is critical for evaluating their potential for coexistence. In this study, we examined whether sympatry influences nest site selection by comparing nest site characteristics between northern and southern flying squirrels in areas of sympatry and allopatry. We deployed radiocollars on 21 NFSs and 20 SFSs at 7 sites in northeastern Minnesota. We used radiotelemetry to identify inactive locations (nest sites) and recorded habitat characteristics at site, structure, and microsite scales. We identified 192 nest sites used on 230 occasions and found that SFSs used large deciduous trees, while NFSs used smaller trees in more coniferous cover. Differences in nest site use highlight differences in niche between the two species and could indicate competition for nesting resources, although they may also reflect underlying variation in habitat availability between zones of allopatry and sympatry. Chapter 3: Activity patterns of animals represent tradeoffs between competing factors, such as energetic costs, competition, predation risk, and resource availability. Climate change is increasingly altering these tradeoffs by reshaping temperature regimes and seasonal energy demands for many species. Northern flying squirrels (Glaucomys sabrinus or NFS) and southern flying squirrels (G. volans or SFS) now experience greater range overlap as warmer winters allow southern flying squirrels to expand northward into historically allopatric northern flying squirrel habitat. At the northern edge of their range, southern flying squirrels may face novel diel constraints driven by colder temperatures and increased temporal overlap with northern flying squirrels. Our objective was to compare optimal and actual activity patterns as well as identify drivers of activity intensity for northern and southern flying squirrels in allopatric and sympatric zones in Minnesota. Diel niche was dependent on thermal energy requirements and body size. Given small size and nocturnal habits, thermal cost minimization was a major driver of activity intensity. By contrast, timing of activity was not driven by thermal cost because there was limited opportunity to save energy by altering activity timing due to shared nocturnality between the species and high energetic costs due to extreme winters where both species are sympatric.

Author dc:creator

• Pfaff, Katie Grace

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/11299/279196

OAI identifier oai:identifier

oai:conservancy.umn.edu:11299/279196