Northern flying squirrel

Two species of flying squirrels are found in Pennsylvania. The rare northern flying squirrel is limited to northern conifer forests, while the smaller southern flying squirrel is wide- spread. Despite very specific habitat preferences, the northern flying squirrel (Glaucomys sabrinus macrotis) was once found across Pennsylvania's northern tier. An extensive study in Pennsylvania conducted from 2003 through 2007 found only 33 northerns. Most known sites are in the Pocono region, with the exception of one in Warren County and one in Potter County.

Habitat factors influencing the northern flying squirrel's decline in Pennsylvania include loss of older conifer and mixed forest stands to development, especially in the Pocono Region, forest management practices geared towards wood products and early successional forest dwelling species, as well as the declining health of hemlock forest stands due to the hemlock wooly adelgid (an invasive insect). Northern flying squirrels rely on specific fungi that are dependent on hemlock and spruce trees. Although smaller in size, the more numerous southern flying squirrel appears to be an aggressive competitor for tree cavities as well as food resources. It also carries a parasite that may be debilitating or lethal to the northern flying squirrel. Studies in Michigan and Ontario, Canada found evidence that the southern flying squirrel's range is expanding northward while the northern species' range is simultaneously contracting. In both studies, these shifts appear to be related to warming trends. Three subspecies of northern flying squirrel occur in the eastern United States, with two subspecies (Glaucomys sabrinus fuscus and G. s. virginianus) that occur south of Pennsylvania currently listed as federally endangered. The subspecies found in Pennsylvania (G. s. macrotis) is disjunct and our state is the southern end of that subspecies' range. Despite its decline in Pennsylvania, the macrotis subspecies is still a common inhabitant of boreal forests of the Pacific coastal and Rocky Mountain states, states bordering the Great Lakes, and throughout Canada. It is considered rare, but can be found in small isolated pockets of suitable habitat along the Appalachian Mountains from Pennsylvania to Tennessee.

Beginning in 2001, the PGC Board of Commissioners approved a series of three federal State Wildlife Grants Program cooperative projects by Wilkes University and Penn State Altoona that monitored more than 500 nest boxes to gather population and reproduction information and evaluate habitat use. Many of the 33 northern flying squirrels captured were fitted with radio transmitters that allowed research to investigate their habitat which overlapped habitat used by southern flying squirrels. Not only did this research show that the competing squirrels foraged in the same habitat, but they were even documented to use the same nest boxes. The Commissioners granted approval for the northern flying squirrel to be designated as a state endangered species in June 2007. Following a public comment period, final approval was granted in October 2007. Management proposed in Pennsylvania's Wildlife Action Plan for the northern flying squirrel includes determining its precise range, regularly tracking population and reproductive trends, and documenting patterns of habitat and space use by northern flying squirrels, as well as its interactions with southern flying squirrels. Monitoring of statewide nest boxes distributed in both potential and occupied forest stands should continue. Live-trapping is recommended for habitat where populations may occur, but have not been documented in the past 20 years. Intensive study is recommended at sites where local population status, behavior, and ecology can be followed closely. The draft also recommends statewide efforts to protect older hemlock and mixed-stand forests and development of guide-lines for forest protection within a five-mile radius of known northern flying squirrel populations.