Studies of ecological factors that affect the population and distribution of the western gray squirrel in northcentral Oregon

Foster, Susan Ann

doi:10.15760/etd.2380

Cited by 5 publications

(7 citation statements)

References 22 publications

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“…Throughout most of its range, the western gray squirrel inhabits conifer-hardwood forests (Ingles 1947, Carraway andVerts 1994). In the southern Puget Trough and Southeastern Cascades of Washington, the western gray squirrel is described as an oak-obligate species that depends on a diverse mixture of oak and conifer trees (Dalquest 1948, Rodrick 1986, Foster 1992, Linders 2000, Bayrakçi et al 2001. When oak is present, western gray squirrels harvest acorns for food and use oak cavities almost exclusively for natal dens (Cross 1969, Linders 2000.…”

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confidence: 99%

“…When oak is present, western gray squirrels harvest acorns for food and use oak cavities almost exclusively for natal dens (Cross 1969, Linders 2000. As observed in other sciurid species, large trees that form a well-connected canopy are an important habitat component for western gray squirrels, providing arboreal escape routes (Ingles 1947, Rice 1977, Gilman 1986, Foster 1992, Ryan and Carey 1995.…”

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Nest Site Selection by Western Gray Squirrels at Their Northern Range Terminus

et al. 2010

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The western gray squirrel (Sciurus griseus) in Washington, USA, is limited to 3 disjunct areas and is a state threatened species.Information is lacking for the North Cascades population, which is the northernmost population for the species. Squirrels in this population exist without oaks (Quercus spp.) that provide forage and cavities for maternal nests elsewhere in their range. During May 2003 to August 2005, we studied selection of nest sites and nest trees by 18 radiocollared squirrels in Okanogan County, Washington. Without oak cavities, females reared their young in dreys. General nest-tree characteristics were similar to characteristics of western gray squirrel nest trees in Southeastern Cascades: relatively tall ponderosa pines (Pinus ponderosa) L 40 cm diameter at breast height. Results from conditional logistic models determined that the odds of a squirrel selecting a tree for nesting increased with greater diameter at breast height and with infection by dwarf mistletoe (Arceuthobium spp.). Nest sites with high selection probability by squirrels had greater basal area and number of tree species than available unselected sites. Retention of forest patches that include a mix of conifer species or conifer and deciduous trees and moderate to high basal area could promote nesting opportunities, connectivity for arboreal travel, as well as abundance and diversity of hypogeous fungi. Experiments to test the efficacy of retaining untreated patches of varying size (including trees infected with mistletoe) on nesting by western gray squirrels within stands managed for fire suppression and forest health would provide important information about the effects of forest fuel management on arboreal wildlife.

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confidence: 99%

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Nest Site Selection by Western Gray Squirrels at Their Northern Range Terminus

et al. 2010

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“…Eastern gray squirrels likely prefer tree seeds over truffles but will eat truffles when hardwood tree seeds are lacking. In contrast, truffles have been a major dietary component for western gray squirrels in all regions regardless of season or the availability of mast producing trees (Stienecker and Browning 1970, Stienecker 1977, Byrne 1979, Foster 1992, Stuart 2012, this study).…”

Section: Discussionmentioning

confidence: 75%

“…Melanogaster, Hysterangium, and Gautiera also were relatively common genera consumed by western gray squirrels in other regions (Stienecker andBrowning 1970, Stuart 2012). Spores of the Geopora complex (Geopora, Barssia, and Balsamia) occurred most frequently in our samples from the Base and were common food for western gray squirrels in the North Cascades (Stuart 2012) and in Oregon (Foster 1992) and for northern flying squirrels (Lehmkuhl et al 2004). A previous study on the Base (Colgan et al 1997, Carey et al 2002 examined availability of truffle genera and frequency in the diet of 2 other sciurids, sampling a site 20 km from our study area in uplands dominated by Douglas-fir with little oak and no pine.…”

Section: Discussionmentioning

confidence: 89%

“…Truffles commonly eaten by western gray squirrels on the Base were similar to those in squirrel diets from other regions. Rhizopogon spores occurred in most fecal samples from the Base and were the most common spores found in feces of western gray squirrels in North Cascades (Stuart ), Oregon (Maser and Maser , Foster ), and California, USA (Stienecker and Browning ). Melanogaster , Hysterangium , and Gautiera also were relatively common genera consumed by western gray squirrels in other regions (Stienecker and Browning , Stuart ).…”

Section: Discussionmentioning

confidence: 99%

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Diets of native and introduced tree squirrels in Washington

Johnston

West²,

Haegen

2019

J Wildl Manag

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Competition for food resources can be a primary mechanism for displacement of native species by introduced species. Investigation of dietary partitioning between potential competitors and spatiotemporal variability in food resources can reveal contested food items and intensity of competition. Introduced eastern gray squirrels (Sciurus carolinensis) have been implicated as competitors with western gray squirrels (S. griseus) and Douglas’ squirrels (Tamiasciurus douglasii), but little is known about interactions among these species. We collected foraging observations and fecal pellets of sympatric gray and Douglas’ squirrels trapped and radio‐tracked in western Washington, USA, from 2007 to 2012. We compared food resources consumed across species, seasons, and years to evaluate dietary overlap and the potential for competitive interactions. All squirrel species ate hypogeous fungi throughout all seasons; spores of several genera were present in 272 of 275 fecal samples and observed in all months. Rhizopogon, Geopora, and Melanogaster spp. occurred in most fecal pellets for all squirrels, but the diet of the Douglas’ squirrels had slightly lower richness of hypogeous fungi than gray squirrels. Although foraging observations suggest that eastern and western gray squirrels shared important dietary items such as acorns, strong differences in consumption of seeds of a common conifer may facilitate their coexistence. Our results suggest that dietary overlap among arboreal squirrels could lead to competitive interactions during periods of food scarcity, but subtle differences may be sufficient to permit long‐term coexistence. Tree squirrels in Washington would likely benefit from forest management practices that promote or sustain robust crops of hypogeous fungi. © 2019 The Wildlife Society.

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Seasonal changes in home ranges of Abert's squirrels: impact of mating season

Edelman

Koprowski²

2006

Can. J. Zool.

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We compared home ranges of introduced Abert's squirrels (Sciurus aberti Woodhouse, 1853) in mixed-conifer forests of Arizona during non-mating and mating seasons. Because Abert's squirrels are reported to depend on ponderosa pine (Pinus ponderosa P. & C. Lawson) forests, the mixed-conifer forest in our study represented a novel habitat. Home-range size, home-range overlap with females, and movement distances increased for males from non-mating to mating seasons. Home-range size and overlap characteristics of females remained consistent between seasons, but movement distances were reduced during the mating season. Males probably increased home-range size, home-range overlap with females, and movement distances during the mating season to maximize contact with scarce females. Home-range size and overlap characteristics of female Abert's squirrels likely remained stable between seasons because females do not search for mates. Restricted movements by females during the mating season may be due to changes in resource use in preparation for reproduction. Non-mating season home ranges in our study were smaller than home ranges observed in ponderosa pine forest. Abert's squirrels in mixed-conifer forest may have small home ranges because resource quality is higher than in ponderosa pine forest or competition for space with co-occurring Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis (J.A. Allen, 1894)).

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Studies of ecological factors that affect the population and distribution of the western gray squirrel in northcentral Oregon

Cited by 5 publications

References 22 publications

Nest Site Selection by Western Gray Squirrels at Their Northern Range Terminus

Nest Site Selection by Western Gray Squirrels at Their Northern Range Terminus

Diets of native and introduced tree squirrels in Washington

Seasonal changes in home ranges of Abert's squirrels: impact of mating season

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