Northern flying squirrels are the primary prey of northern spotted owls and are important dispersers of fungal spores in Pacific Northwest forests. Despite the importance of these squirrels in forest ecosystems, information is lacking on life history and methods for determining age and reproductive condition. In the laboratory, we measured epiphyseal notch, femur length, rostrum length, least interorbital breadth, rump pelage length and color, and tail width of dead squirrels. We analyzed weight, pelage color, and reproduction for field-collected data from live squirrels. We also described age-class differences in facial features and tail size and shape in the Puget Trough. A birth-year-based age-class system had several advantages over the traditional juvenile-subadult-adult class system. Three age classes can be distinguished in the field, each with varying degrees of accuracy. Reproduction of northern flying squirrels can be reliably determined in live-trapping studies. Enlargement, turgidity, and redness of genitalia are detectable signs of reproductive activity, whereas reduction, flaccidity, and paleness signal inactivity for both males and females. Nipple length is the best indicator for distinguishing sexual maturity of inactive females. The most effective way to avoid mistakes and ambiguity about age and reproductive status in the field is to take descriptive notes. Maturation and reproductive patterns were similar among the Puget Trough, Olympic Peninsula, and northern Cascade studies in Washington. Squirrels in the Coast Range of Oregon, however, displayed different patterns. Regional populations differed in proportion of females reproductively active, the reproductive maturity of yearling females, and survivorship across age classes. Regional variations suggest accurate assessment of age and reproduction is a prerequisite for understanding flying squirrel ecology.Keywords: Northern flying squirrel, maturation, reproductive biology, Oregon, Washington, live-trapping, necropsy. AbstractThere has been substantial research on old-growth Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) forests and wildlife that depend on them (Ruggiero and others 1991). Northern flying squirrels (Glaucomys sabrinus [Shaw 1801]) have been of particular interest because they seem to be keystone species in late-seral forests-a main prey of strigids and mustelids on one trophic level, and a consumer and disseminator of fungal spores on another. Through its mission to develop forest management practices that steward biodiversity, the Ecological Foundations of Biodiversity Research Team has focused research on the relation between northern flying squirrels and forest health.Despite the importance of northern flying squirrels in Pacific Northwest forest ecosystems, information is lacking on life history and methods for determining age and reproductive condition. We began studying flying squirrel populations in 1985 in Douglas-fir forests of the Coast Ranges physiographic province in southwestern Oregon (Franklin and Dyrness 19...
In the Pacific Northwest, the northern flying squirrel, Glaucomys sabrinus, consumes sporocarps of a wide variety of hypogeous mycorrhizal fungi (truffles). Numerous other foods are also consumed but are not well characterized by fecal pellet analysis either because they are more fully digested (seeds, nuts, fruits, vegetation) or because of the similarity among spore types (lichen photobionts, epigeous fungi). Thus, observations of squirrel foraging are important in characterizing non-truffle dietary components. As part of a trapping and telemetry study, we observed G. sabrinus foraging on 63 occasions; 34 were observations of non-truffle consumption. These foods included epigeous fungi, fruits and seeds, and conifer seedlings. We hypothesize G. sabrinus may consume more non-truffle foods than is indicated by fecal pellet analysis, and that such foods may be important nutritional supplements to a low-quality diet as well as substitutes for truffles in times or places of low truffle abundance. By availing themselves of other food sources, G. sabrinus may persist in otherwise marginal habitats, while also contributing to the dispersal of a wide diversity of fungi and increasing genetic diversity of fungal and microbial species.
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