Commissioners today gave final approval to add to the state’s endangered species list the northern flying squirrel, which is the larger and rarest of Pennsylvania’s two flying squirrel species.
“Our field survey work has shown that the northern flying squirrel’s population has been in decline for some time and is in need of our assistance,” said Greg Turner, Game Commission biologist. “They have very specific habitat preferences and their existence in Pennsylvania is threatened by a parasite carried by southern flying squirrels and by forest pests that destroy their preferred habitat. Adding this species to the state’s endangered species list will allow us to ratchet up the management attention we provide these squirrels. Also, their eligibility for federal funding will improve.”
Northerns were once found across Pennsylvania’s northern tier. The major reason for their decline is the loss and fragmentation of older-growth coniferous forest in Pennsylvania. Now their small local populations are threatened by additional limiting factors
The northern flying squirrel is common in the boreal forests of states along the Canadian border and Canada. In Pennsylvania, however, its distribution is limited to less than a half-dozen known sites in old-growth forests with a large percentage of conifers. All are in northeastern Pennsylvania, with the exception of one in Warren County and one in Potter County. It’s possible there are more local populations, but they haven’t been uncovered yet. Identification isn’t easy either, because they are very similar to southern flying squirrels.
Northern flying squirrels have been identified as a species of greatest conservation in Pennsylvania’s Wildlife Action Plan, which was adopted by the agency and approved by the U.S. Fish and Wildlife Service in 2006. Their plight is considered a “high-level concern.” The Game Commission several years ago also approved a project through the State Wildlife Grant Program that focused on developing an annual statewide nest box survey and identifying the habitat preferences of northerns through telemetry. It was carried out by Wilkes University and Penn State University.
The parasite carried by southern flying squirrels and lethal to northerns is called Strongyloides robustus. The parasite poses no threat to southerns, but it seems to suppress the northerns’ ability to put on winter fat, and to even maintain its existing weight. Since northerns and southerns will share living quarters where their ranges overlap, there is substantial concern for the already rare northerns.
Further complicating the northerns’ existence is the wooly adelgid, a European insect that strips and frequently kills hemlock trees, which northerns prefer as habitat. The forest pest has devastated and continues to ravage huge chunks of hemlock forestland throughout eastern Pennsylvania.