State of the Greater Fundy Ecosystem - Northern Flying Squirrel

GREATER FUNDY ECOSYSTEM RESEARCH PROJECT

UNB Faculty of Forestry and Environmental Management

State of the Greater Fundy Ecosystem

Habitat Characteristics and Home Ranges of Northern Flying Squirrel in
Fundy NP and the GFE

Shawn Gerrow1, Stephen Flemming2, and Tom Herman1
1Acadia University, Wolfeville, N.S. B0P 1X0
2Fundy National Park, P.O. Box 40, Alma, N.B. E0A 1B0

Northern Flying Squirrel
(Photo: B. Townsend)

This study examined the home range, habitat use, nesting ecology, and diet of the Northern Flying Squirrel in and surrounding Fundy National Park (Fundy NP).

GOAL

The study was undertaken to provide baseline data on the habitat used by Northern Flying Squirrel in eastern Canada.

METHODS

The home ranges and habitat use of 15 Northern Flying Squirrels (7 male and 8 female) were examined using radio-telemetry. Comparisons were made of the habitat characteristics of high use and low use areas within the home ranges of these squirrels. High use areas had various levels of observed squirrel activity, whereas low use areas were parts of the home ranges where squirrels were not found.

RESULTS

The home ranges of male squirrels were found to be significantly larger (median 12.49 ha) than that of females (median 2.75 ha). In this study, male home ranges were found to overlap as many as three female home ranges, as well as those of other males. The large size of male home ranges may be related to reproduction, as males with larger home ranges have access to a greater number of females. While female home ranges were considerably smaller, they may occupy the higher quality foraging habitat.This would be beneficial during the breeding season, as it would reduce the energy requirements for foraging, and minimize time spent away from the nest. In this study, female home ranges showed little or no overlap.

Within their home ranges, Northern Flying Squirrels selected areas with the largest trees (³ 4 m height) and snags, more decayed structural components (trees, snags, logs and stumps), highest structural diversity, and lower tree density (Table 1). In addition, they used trees and snags for nesting that were larger than those randomly available (Table 2). This suggests that Northern Flying Squirrels in New Brunswick are dependent upon stands with older forest structural characteristics.

In New Brunswick, Northern Flying Squirrels used four distinct nest types: outside nests, woodpecker cavities, natural cavities and ground nests. Outside nests were constructed of bark, sticks, grass and lichens and were located in witches brooms or in the crotches of trees. The majority of these nests were found in coniferous trees, usually Red Spruce or Balsam Fir. Most were in live trees, although a few were in dead trees which still had branches. The mean dbh of outside nest trees was 28.6 cm (Table 3). Woodpecker-excavated squirrel nests were usually found in the cavities of smaller sized woodpeckers such as the Hairy Woodpecker, Downy Woodpecker, or Black-backed Three Toed Woodpecker. The majority of these nests were in dead trees, both coniferous or deciduous, with a mean dbh of 24.5 cm (Table 3). Natural cavity nests were located in cracks, broken tops and branch holes of hollow deciduous or coniferous trees and snags. The mean dbh of these nest trees was 29.7 (Table 3). Ground nests were constructed of bark, lichens and grass, and were located under rocks, roots, coarse woody debris or snow.

Nest use was found to vary seasonally. Outside nests were not used during the winter but were used throughout the rest of the year. Woodpecker nests were used only during spring and summer. Ground nests were not used during the summer, but were extensively used during the winter, particularly during periods of snow cover. Ground nesting during the winter provides added warmth due to the insulating properties of snow. It also allows immediate access to underground food caches, thus eliminating the need for foraging on cold nights. A major drawback with ground nesting, however, was the increased risk of predation from weasels. Natural cavity nests were the only nest type used consistantly year round. These nests may be most important during the colder months before snow fall, and during winters of intermittent snow cover as they provide greater insulation and are large enough to permit aggregations (nest sharing).

Northern Flying Squirrel using a tree-cavity
(Photo: Fundy NP)

In New Brunswick, Northern Flying Squirrels aggregated throughout the year, however, this behaviour was found to increase with decreasing temperatures. Cavity trees and snags used for aggregating were larger in diameter (mean dbh of 41.5 cm) than those used by single squirrels. Natal nests were also found in large diameter trees and snags (median dbh 41.2 cm) with natural cavities. This nest type may provide greater protection from weather and may therefore increase reproductive success.

The diet of Northern Flying Squirrels was examined through direct observations of foraging behavior, and through faecal analysis. In New Brunswick, flying squirrels were observed foraging on seasonally available food sources, such as lichens, birch seeds, beech nuts, epigeous (above ground fruiting) and hypogeous (underground fruiting) fungi, insects, raspberries, spruce cones, buds and catkins. The results of faecal analysis indicated that hypogeous fungi were important in the diet of northern flying squirrels in New Brunswick. Spores of hypogeous fungi were present in 95% of the 150 samples analysed. Hypogeous fungi are known to form mycorrhizal associations with woody plants that allow the plant to grow. As dispersers of these spores, Northern Flying Squirrels likely contribute to the ecological integrity of eastern forests.

IMPLICATIONS FOR MANAGEMENT

The studies indicate thate Northern Flying Squirrels in New Brunswick may be dependent upon older forest stands. The characteristics of older forests may be important to these squirrels for a number of reasons. In New Brunswick, older stands are more structurally diverse, i.e., they contain both coniferous and deciduous tree species, snags, stumps, and logs in varying sizes and states of decay. These features provide a greater availability of food resources, as well as nesting opportunities for this species. Also larger (taller) trees allow for long glides which may be important for predator escape, and for accessing larger home ranges. Stands with low tree density may be more conducive to gliding.

Further reading:

Gerrow, J.S. 1996. Home range, habitat use, nesting ecology and diet of the Northern Flying Squirrel in southern New Brunswick. M.Sc. thesis. Department of Biology. Acadia University. Wolfeville, N.S.

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