Ocean Blue Blog
By Richard Arterbury
Isolated populations more vulnerable to local extinction | Wildfires Fires
Flying Squirrels are the fungi gods of the forest and by spreading fungi from point a to point b in our forest. After Forest fires the Northern Flying squirrels are vulnerable due to lack of cover trees once provided. Ocean Blue would like to add habitat protection boxes throughout the forest to help protect the flying squirrel. Owls today have an open forest while many animals are now left with out protection of large conifer trees and other hardwood trees.
Many forms of hypogeous fungi rely on small mammals to consume and disperse their spores. It is well documented in the Pacific Northwest that northern flying squirrels (Glaucomys sabrinus) rely on hypogeous fungi as a food resource.
Hypogeous fungi rely on small mammals to consume and disperse spores throughout the Forrest. This is well documented in the Pacific Northwest that the northern flying squirrels rely on hypogeous fungi as a food resource. However with out a tree canopy many mammals are in danger and are being consumed by the predators of the forest. However documentation of the flying squirrel's diet are poorly documented. Using live-capture to obtain fecal samples, are key to documenting what all is being consumed by flying squirrels by collecting fecal samples.
A recent study by Matthew Wheatley examined dietary fungal diversity from the feces of 44 northern flying squirrels inhabiting variable-aged managed forest stands during late summer in the foothills of west-central Alberta, Canada. Fungal material was found in all specimens, and was identified to order, family, or genera via microscopic spore morphological classification. Twenty-six spore morphologies were found; 1 was identified to order, 4 to family, 13 to genus, and 8 remained unidentified. The most frequently consumed fungi were of the hypogeous form of the genera Cortinarius, Gastroboletus, and Hysterangium. Insect material also figured prominently. In contrast to epigeous-dominated winter diets of flying squirrels found elsewhere in Alberta, here, hypogeous species formed almost one-half of those identified. There is evidently notable consistency in species richness of fungi in flying squirrel diets continent-wide but in more northern forests, diets may shift from epigeous species during winter months to hypogeous species in summer.
The primary threats to this species are incompatible forest management practices, large high-severity wildfires, and climate change.
Forest management practices and large high-severity wildfires reduce canopy closure and large conifer and hardwood tree densities, reducing habitat quality and quantity. It has been shown that northern flying squirrel abundance is reduced by forestry practices that influence the structure or age of residual stands, both in the short and the longer term, and abundance has also been shown to be reduced in partially harvested areas compared to uncut stands. Prescribed fire may have short-term (less than 8 years) negative effects on abundance by reducing the frequency and biomass of their primary food source, truffles. Climate-driven changes in fire regimes are projected to include increases in fire frequency, area, and intensity which are expected to result in loss of late-seral habitat. Because northern flying squirrels are thought to be resource and dispersal limited these threats make small and isolated populations more vulnerable to local extinction.
HabitatThe northern flying squirrel is a nocturnal arboreal squirrel occurring throughout the northern latitudes of the United States and Canada. There is considerable evidence that flying squirrels are more abundant in forests with an abundance of large live trees, large dead trees (snags), well-developed understories, and many large logs on the ground. In the Sierra Nevada, where conditions are relatively xeric (dry) compared to elsewhere within the species’ range, higher densities of flying squirrels are often found in relatively close proximity (less than 150 meters) to perennial streams. It is believed that the correlation between this species and perennial streams in the Sierra Nevada is due to higher soil moisture and other microclimate conditions in riparian areas that increases the abundance of the squirrels primary food source, truffles (fruiting body of subterranean fungi).
Mean home range sizes of approximately 9 to 29 hectares (22 to 72 acres) have been recorded in the Sierra Nevada, with individual home ranges overlapping both within and between sexes, suggesting individuals share foraging areas.
On the Sierra National Forest in the central Sierra Nevada, these squirrels were found selecting taller and larger than expected diameter conifers (red firs in particular) and snags for nesting. On the Plumas National Forest in the northern Sierra, one study found that they selected hardwoods (black oaks) more often than expected compared to all other available trees and snags. Larger trees, snags, and hardwoods are more likely to have woodpecker or fungal cavities, or other decay features that allow for internal nesting, and thereby offer protection from predation and environmental extremes.
They do not create their own cavities, relying on naturally created cavities or cavities created and abandoned by woodpeckers. Northern flying squirrels play several important roles in forest ecosystems. In addition to serving as a primary prey for several old forest dependent species, including California spotted owls, Pacific fishers, and American martens, flying squirrels eat, store, and distribute truffle spores throughout the forests they inhabit. Truffles are critical to forest health because these fungi form mycorrhizal relationships with trees, a symbiotic (mutually beneficial) relationship that provides the fungi with carbohydrates and the tree with otherwise unavailable water and nutrients from the soil. Not only do trees with mycorrhizal fungi grow larger and faster, they are less susceptible to drought and disease.
ConservationThe northern flying squirrel is a primary prey species for several rare old forest species and they are a primary vector for distributing the spores of mycorrhizal fungi, which increase tree nutrient and water uptake and forest resilience to climate change; therefore, maintaining, expanding, and increasing habitat quality, quantity, and connectivity for the northern flying squirrel is essential to maintaining diverse, healthy, and resilient forests in the Sierra Nevada.
StatusThe Northern flying squirrel is considered a management indicator species for all ten National Forests in the Sierra Nevada. The species is currently being monitored on the Plumas and Lassen National Forests though a multi-year monitoring effort. It is not considered a game species and it is illegal to kill or capture a Northern flying squirrel.
Research about the flying squirrel:
Carey, A.B., 2000. Effects of New Forest Management Strategies on Squirrel Populations. Ecological Applications 10(1) 248-257. (234KB PDF)
Holloway, G.L., and W.P. Smith. 2011. A meta-analysis of forest age and structure effects on northern flying squirrel densities. Journal of Wildlife Management 75:668-674. (1.7 MB PDF)
Lehmkuhl, J.F., et.al., 2004. Truffle Abundance and Mycophagy by Northern Flying Squirrels in Eastern Washington Forests. Forest Ecology and Management 200, 9-64. (233KB PDF)
Meyer, M.D., et.al., 2005. Nest Trees of Northern Flying Squirrels in the Sierra Nevada. Journal of Mammology, 86(2) 275-280. (157KB PDF)
Meyer, M.D., M.P. North, and D.A. Kelt, 2005. Fungi in the Diets of Northern Flying Squirrels and Lodgepole Chipmunks in the Sierra Nevada. Canadian Journal of Zoology, 83, 1581-1589. (101KB PDF)
Meyer, M.D., D.A. Kelt, and M.P. North. 2007. Microhabitat associations of northern flying squirrels
in burned and thinned forest stands of the Sierra Nevada. American Midland Naturalist 157:202–211.
Meyer, M.D., M.P. North, and S.L Roberts. 2008. Truffle abundance in recently prescribed burned and unburned forests in Yosemite National Park: implications for mycophagous mammals. Fire Ecology Special Issue 4:24-33. (2.4 MB PDF)
North, M. 2002. Seasonality and abundance of truffles from oak woodlands to red fir forests. p 91-98 in Jared Verner (tech. editor). Proceedings of a Symposium on the Kings River Sustainable Forest Ecosystems Project: Progress and Current Status. USDA Forest Service, Pacific Southwest Research Station General Technical Report, PSW-GTR-183. (164 KB PDF)
Pyare, S., and W.S. Longland. 2002. Interrelationships Among Northern Flying Squirrels, Truffles, and Microhabitat Structure in Sierra Nevada Old-growth Habitat. Canadian Journal of Forest Restoration 32, 1016-1024. (78KB PDF)
Rosenberg, D.K., R.G. Anthony, 1992. Characteristics of Northern Flying Squirrel Populations in Young Second and Old-growth Forests in Western Oregon. Canadian Journal of Zoology 70,161-166. (486KB PDF)
Smith, J.R. 2009. Spatial organization, habitat preference, and management of northern flying squirrels, Glaucomys sabrinus, in the northern Sierra Nevada. Thesis, University of California, Davis. 45 Pages (372 KBPDF)
Smith, J.R. et al. 2011. Spatial organization of northern flying squirrels: Glaucomys sabrinus: Territoriality in females? Western North American Naturalist 71(1):44-48. (1.12 MB PDF)
Thysell, D.R., et.al., 1997. Observations of Northern Flying Squirrel Feeding Behaviors: Use of Non-Truffle Food Items. Northwestern Naturalist 78, 87-92. (158KB PDF)
Villa, L.J., et.al., 1999. Maturation and Reproduction of Northern Flying Squirrels in Pacific Northwest Forests. Pacific Northwest Research Station, U.S. Forest Service, GTR-444. (845KB PDF)
Waters, J.R., and C.J. Zabel, 1995. Northern Flying Squirrel Densities in Fir Forests of Northeastern California. Journal of Wildlife Management 59(4) 858-866. (133KB PDF)
Waters, J.R., et.al., 2000. Northern Flying Squirrel Mycophagy and Truffle Production in Fir Forests in Northeastern California. Pacific Southwest Research Station, U.S. Forest Service, GTR-178. (498KB PDF)
Wilson, J.A., D.A. Kelt, and D.H. Van Vuren. 2008. Home range and activity of northern flying squirrels (Glaucomys sabrinus) in the Sierra Nevada. Southwestern Naturalist 53:21-28.
Zabel, C.J., J.R. Waters. 1997. Food Preferences of Captive Northern Flying Squirrels from the Lassen National Forest in Northeastern California. Northwest Science 71(2) 103-107. (420KB PDF)
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