Digestive tracts of 91 northern flying squirrels (Glaucomys sabrinus) were analyzed for food items; 28 were from northwestern Oregon and 63 from northeastern Oregon. Ninety percent or more of the ingested materials were fungi and lichens, including 20 genera of hypogeous fungi. The northern flying squirrel, in using hypogeous fungi as a major food source, is an important nocturnal disperser of the spores. In Oregon coniferous forests, these fungi are obligatory ectomycorrhizal symbionts with the trees in which the squirrels live.
Fecal samples were collected over 27 months from the northern flying squirrel (Glaucomys sabrinus (Shaw)), a mycophagist in the Pacific Northwest portion of its range. Nine genera of hypogeous Basidiomycetes, 10 of hypogeous Ascomycetes, and 1 of hypogeous Zygomycetes were identified from fecal samples (hypogeous fungi fruit underground). The squirrel food habits generally paralleled the seasonal availability of the hypogeous fungi, but with notable exceptions. Our data demonstrate the functional diversity an individual species lends to its habitat when viewed in a functional context.
Most arid and semiarid rangeland plants form a mycorrhizal symbiosis with certain fungi through which the host plants absorb water and nutrients from the soil. Small mammals are known to disperse viable spores of hypogeous, mycorrhixal fungi in forests, but little is known about small mammals as vectors of funpl spores in rangelands. We therefore examined the stomach contents of 575 mammals (16 genera, 26 species) for fungal spores. Spores of hypogeous, mycorrhixal fungi, representing 15 genera, were identified from 21% of the mammals. Although wind and water are thought to be the main means of dispersal for fungal spores in rangelands, a variety of mammals may be locally important in dispersing spores of mycorrhizal fungi.
Of the 10 genera of North American microtines, the molars of 4 become rooted in adults and thus do not grow continuously; the molars of the remaining 6 do not develop true roots and grow throughout the life of the animal. Continuously growing molars lengthen rapidly, but rooted molars do not. We hypothesize that the life of the molars in voles with rooted molars is increased by tooth enamel that is thicker than in voles with continuously growing molars. Measurements of the enamel thickness in Microtus and Clethrionomys support this hypothesis.
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