Protected Species in Pennsylvania: Northern Flying Squirrel

Introduction

Flying squirrels are elusive mammals, largely because they are nocturnal (awake at night) and arboreal (living in trees). In fact, their elusiveness has led to some misconceptions, such as believing they don’t exist or that they are a joke. However, in Pennsylvania, the behaviors of the northern flying squirrel (Glaucomys sabrinus) aren’t the only thing making them hard to find. Habitat loss has been difficult for the northern flying squirrel because they don’t easily adapt to new habitats, like the southern flying squirrels. This article will help you get to know your new friend hiding up in the trees and learn about how you may be able to help protect this shy creature.

What Is a Northern Flying Squirrel?

Flying squirrels are known for their ability to glide from tree to tree using the patagia, or skin flaps, that attach to the wrist and ankles. Northern flying squirrels also have large eyes to help with nocturnal activity. Southern flying squirrels are very similar to northern flying squirrels and are also found in Pennsylvania. Northern flying squirrels have an overall body length of 8 to 11 inches, which is slightly larger than the 8 to 10 inches of the southern flying squirrel. The only way to tell the difference between the two species is the belly hair found between the front legs. Southern flying squirrels have hair that is white from the tip to the base, while northern flying squirrels will have a darker lead color at the base of the hair fading to white at the tip.

Northern flying squirrels create dens in tree cavities by lining them with strips of bark. Fungi and lichens are a major food source for northern flying squirrels, with acorns and conifer seeds as another important food source. Northern flying squirrels don’t share the food hoarding trend of other squirrels, instead, they forage in treetops during the winter. Reproduction of the northern flying squirrel is not well known throughout the United States. In Pennsylvania, there is typically one litter born in mid to late May with one to four young per litter. Northern flying squirrels are fast learners and can take their first flight as early as 3 months from birth.

What Is the Habitat of the Northern Flying Squirrel?

Old-growth spruce and conifer stands are the preferred habitat of the northern flying squirrel. Downed woody debris littering the forest floor is also important for the optimal habitat. Pennsylvania doesn’t have a lot of forest that fits the best habitat for the northern flying squirrel. Many of the forests that are old-growth coniferous forests in Pennsylvania are in small, fragmented patches. In Pennsylvania, the northern flying squirrel is only found in the north, predominantly in the northeast.

Why Are They Listed?

In the late 19th and early 20th centuries, widespread clear-cut logging took place in the Appalachian forests. It is strongly believed that these harvesting events caused a great deal of range contraction, disjunction, and population extinction for the northern species. Many types of southern tree species are also moving north into Penn’s woods. These include species such as maples and oaks that provide better habitat for the southern flying squirrel, which could then outcompete the native northerners. Today, the greatest threat to the northern species comes from forest practices and development. Furthermore, the species appears to be most vulnerable in the mountain areas at the southern margins of its range (southern Appalachians, Rocky Mountains, and Sierra Nevada). 

Which Agencies and Organizations are Involved in Their Recovery?

The Pennsylvania Game Commission (PGC) is the primary agency involved in the protection and conservation of the northern flying squirrel. A 2001 decision by the PGC approved a series of cooperative projects that monitored more than 500 nest boxes to gather population and reproduction information. In June 2007, the Commissioner granted approval for the northern flying squirrel to be designated as a state-endangered species. The PGC then listed the squirrel as a priority species in the state’s Wildlife Action Plan. The Wildlife Action Plan for the squirrel involves determining the species’ precise range, regularly tracking its population and reproduction trends, and documenting patterns of habitat and space use. The northern flying squirrel is also protected under the Game and Wildlife Code, which prohibits the hunting of this species. Other agencies, such as the U.S. Fish and Wildlife Service and The National Wildlife Federation, have aided in the conservation of the species as well. A few private non-profit organizations work to increase public knowledge of and understanding of the northern flying squirrel, they include the Cook Forest Conservancy, WeConservePA, and Defenders of Wildlife.

What Is the Recovery Plan?

The recovery plan for the northern flying squirrel depends on protecting current populations by protecting densely forested areas with good canopy cover. Preserving these areas on state land is often the primary focus. Private forest lands can also provide habitat for the northern flying squirrel, but these forests are also important for providing the public with a sustainable supply of wood. One method of harvest that can help prevent complete loss of habitat is doing selective cuts and having designated wildlife trees around nesting areas of the flying squirrel. Other attempts have been made to help create habitat in the form of plantations to help bring back some of the desired tree species and habitat. These efforts will only help bring the flying squirrel populations back over time after the trees mature.

How Could the Recovery Plan Affect Stakeholders?

Compared to protecting wildlife that are more easily seen and heard, the benefits of protecting the northern flying squirrel may be less tangible. Still, the northern flying squirrel contributes to healthy ecosystems through the distribution of seeds, which allow new plant growth, and squirrels can serve as important prey for some predators. The conservation of northern flying squirrels can also help protect forests that contain hemlock and spruce. Conservation may not always result in positive outcomes. Northern flying squirrels are rodents and could potentially make their nests inside houses or barns, but they do not carry rabies. The conservation of northern flying squirrels may also interfere with timber production objectives in some contexts.

What Can Landowners Do to Help?

• Keep old growth if possible. While the northern flying squirrel prefers old-growth forests, much of Pennsylvania’s woods do not contain this ideal habitat. The little that is left consists of many isolated fragments, so the squirrels are forced into using a mix of coniferous and deciduous trees.
• Keep pathways to old growth: If keeping old, large conifers is not possible, then try to keep a continuous habitat between these old-growth conifers and forests with large mature trees. The northern flying squirrel relies on large trees in order to glide from one tree to another.
• Keep an eye on hemlocks: Hemlocks are a favorite home to northern flying squirrels, but recently have been under attack from the invasive hemlock woolly adelgid. This is an insect that is very hard to see but easily identifiable. It forms white woolly masses on the underside of branches at the base of the needles.

Other Information about Northern Flying Squirrels 

Pennsylvania Game Commission: Northern Flying Squirrel

National Wildlife Federation: Flying Squirrels

Pennsylvania Fish and Boat: State Wildlife Action Plan

Animal Diversity: Glaucomys sabrinus

Student Authors

This extension article was written in collaboration with undergraduate students as part of a class assignment at Pennsylvania State University.

References

Butchkoski, Eileen; Turner, Greg. (2010, February 5). Northern Flying Squirrel. Pennsylvania Game Commission.

Haffner, C. D., & Day, D. M. (Eds.). (2015, October 1). Pennsylvania Wildlife Action Plan, 2015-2025. Pennsylvania Game Commission and Pennsylvania Fish & Boat Commission.

Malamuth, E., & Mulheisen, M. (2011). Glaucomys sabrinus northern flying squirrel. Animal Diversity Web. Retrieved April 13, 2021.

Northern Flying Squirrel. (2019, September 1). Kaniksu Land Trust.