Squirrels cannot live by truffles alone: a closer look at a northwest keystone complex.

Abstract

Tree squirrels in the Pacific Northwest are part of a keystone complex that includes ectomycorrhizal fungi, Douglas-fir, and spotted owls. All three squirrel species—the northern flying squirrel, the Douglas' squirrel, and the Townsend’s squirrel—consume truffles produced by fungal partners of important tree species. The squirrels then spread the spores of these fungi throughout the forest in their feces. The fungi are important to the growth and health of many Northwest tree species. Squirrels, in their turn, are major prey for vertebrate predators in the forest, including threatened and sensitive species such as the northern spotted owl. Thus, as an essential link in the web of interdependence, squirrels are good indicators of forest function and can be used to evaluate management effectiveness in promoting biodiversity and sustainability. Management for habitat elements that contribute to truffle production—coarse woody debris, a variety of tree species, and ericaceous shrubs—has been proposed to benefit squirrels and consequently their predators. But there has been little research on the nutritive value of truffles, the relationship between truffle biomass and squirrel biomass, the importance of other food for the squirrels, or effects of management on truffle production. Several research projects out of the Pacific Northwest Research Station’s Olympia, WA, laboratory are beginning to answer preliminary questions in these areas.

Citation

Duncan, Sally. 2004. Squirrels cannot live by truffles alone: a closer look at a northwest keystone complex. Science Findings 60. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 5 p