Northern Flying Squirrel (Glaucomys sabrinus)

County List:

Rule:

Forested or Mixed Forested/Nonforested Landscapes

      (Northern Hardwoods (Sm Saw or Lg Saw or Uneven))
      or (Spruce/Fir (Sm Saw or Lg Saw or Uneven))
      or (Hemlock (Sm Saw or Lg Saw or Uneven))
      or (Jack Pine (Sm Saw or Lg Saw or Uneven))
      or (Mixed Upland Conifer (Sm Saw or Lg Saw or Uneven))
      or (Mixed Northern Hardwoods (Sm Saw or Lg Saw or Uneven))
      or (Northern White Cedar (Sm Saw or Lg Saw or Uneven))
      or (Any Lowland Mixed (Sm Saw or Lg Saw or Uneven))
   containing:
      (Mast and Dead Down Woody Debris and Snags and Living Cavity Trees)

Habitat List:

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Literature:

It is most at home in mixed forests containing mature deciduous and coniferous trees, although it frequents pure stands of either type.

Like many squirrels, the northern flying squirrel builds a sheltered nest inside a tree cavity or a spherical nest in the branches of a tree. An outside nest is typically in a conifer 3-60 feet above the ground, close to the trunk, and fashioned from twigs, bark, and moss. This squirrel is an opportunist and occasionally uses an old bird's nest as a convenient platform on which to construct its own home.

During the winter the northern flying squirrel shuns exposed nests in favor of a tree hollow.

This species relishes the typical squirrel diet of nuts, acorns, and conifer seeds supplemented by fruits, buds, lichens, fungi, and sap. Insects and an occasional bird egg round out the menu.

Habitat: Forests of mixed mature conifer and deciduous trees; less often in purely hardwood forests. Favors cool, heavily wooded areas above 1,000 ft in elevation.

Special Habitat Requirements: Mature trees, cavities for winter dens. Arboreal lichens for winter food.

Habitat Preferences: Habitat associations of the nocturnal northern flying squirrel are less documented than those of diurnal members of the squirrel family, although it is agreed that the species thrives in heavily wooded areas containing mixed conifers and northern hardwoods having mature growth. Preferred environments are moist with a forest floor littered with moss-covered logs. Pure stands of white cedar, spruce, balsam fir or hardwoods are perhaps less productive habitat than mixtures of hemlock-maple or hemlock-birch. In Michigan, northern flying squirrels have been observed in coniferous swamps in Montmorency County and in jack pine and cutover hardwoods and in mixed hardwoods and conifers in the Huron Mountains. In Quebec, Wrigley listed a favorable habitat as a mature mixed forest of yellow birch, sugar maple, hemlock, balsam fir, and white spruce.

Behavior: Northern flying squirrels den in cavities in living or dead trees, and sometimes in houses and other structures; they probably have to compete with the larger tree squirrels, raccoons, and other arboreal animals for hollows with large openings. A favorite northern flying squirrel site is a woodpecker hole, positioned so that rain or snow does not drain in to the denning space. Rotted out areas in snags, topped-off trees, and even cavities in old telephone poles can be enlarged and deepened to provide suitable housing, especially for winter occupancy. In summer, like other tree squirrels, the northern flying squirrel constructs bark and twig nests. These are usually located in young evergreen trees well above the ground and on branches adjacent to sturdy trunks.

Food Habits: Like other squirrels, the northern flying squirrel basically prefers seeds but will also feed on assorted animal and plant foods when seasonally available. In late winter and spring, stored seeds of conifers and hardwoods are the major food supply; tree buds, bark, and lichens provide supplementary nourishment. In summer, insects (especially moths and beetles), birds eggs and nestlings provide animal protein, while fleshy fruits of trees and shrubs supply vegetative bulk. Fungi and maple sap are eaten in spring. The caching of the autumn seed crop is probably the most important requirement for this species survival. Northern flying squirrels consume quantities of conifer seeds which are cached in the cones. Beechnuts, hazelnuts, acorns, and evergreen cones may be piled on the ground or in hollow stumps but are usually stored well above ground in hollow trees. Northern flying squirrels occasionally supplement their own supplies by raiding the stores cached by diurnal tree squirrels.

Distribution: Northern flying squirrels occur in forested regions over most of northern North America. The flora of inhabited areas typically is dominated by conifers, but often is mixed coniferous-deciduous forest and occasionally strictly broadleaf deciduous forest.

Ecology: In the Great Lakes Region, northern flying squirrels were found in beech-maple stands, hemlock forests and also in white cedar swamps, spruce-fir forests, and jack pine barrens.

Southern flying squirrels may have a greater ability to locate and control tree cavities, and to displace northern flying squirrels from hardwood forest, especially if conifers are absent. Also, southern flying squirrels breed earlier than northern flying squirrels and, in areas of sympatry, may usurp the tree cavities as nesting sites.

While live-trapping fishers and martens in the McCormick Wilderness in Marquette and Baraga Counties of the Upper Peninsula of Michigan I captured northern flying squirrels in sets placed in downed hollow logs in mixed lowland conifer swamps. The predominant tree species were northern white cedar, balsam fir, yellow birch, and maple with scattered openings with tag alder and adjacent rock outcrops and northern hardwood forest.