THE NORTHERN FLYING SQUIRREL AS AN INDICATOR SPECIES OF TEMPERATE RAIN FOREST: TEST OF AN HYPOTHESIS

Abstract

Management indicator species (MIS) often are selected because their life history and demographics are thought to reflect a suite of ecosystem conditions that are too difficult or costly to measure directly. The northern flying squirrel (Glaucomys sabrinus) has been proposed as an MIS of temperate rain forest of southeastern Alaska based on previous studies in the Pacific Northwest that demonstrated its habitat is multi‐factorial, i.e., an emergent property of old‐growth forest. We evaluated the suitability of flying squirrels as MIS in temperate rain forests of Alaska by modeling seasonal (spring, autumn) microhabitat use with stepwise logistic regression (SLR) using either individual habitat variables (n = 26) or multivariate habitat “factors,” which were linear combinations of individual habitat variables generated from factor analysis. We compared the efficacy of single variable vs. multivariate factor models in explaining variation in microhabitat use to test the hypothesis that the habitat of flying squirrels in southeastern Alaska was an emergent property of old‐growth rain forest. The underlying premise was that if factors were more thorough in explaining microhabitat use, the habitat of flying squirrels was multifactorial; that is, it consisted of multiple late‐seral forest attributes occurring coincidentally at usable spatial scales (e.g., home range). SLR models with multivariate factors performed poorer in predicting capture sites than models of individual habitat variables. Two variables, density of large (>74 cm dbh) trees and understory cover of Vaccinium, explained much of the variation in microhabitat use. We conclude that the habitat of G. sabrinus in southeastern Alaska does not reflect emergent properties of old‐growth forest in southeastern Alaska and hypothesize that this pattern may be related to regional ecological differences that facilitate a more general lifestyle than populations in the Pacific Northwest. Furthermore, the effectiveness of Glaucomys sabrinus as an MIS in north temperate rain forest is suspect, illustrating that regional differences in ecology of a species warrant caution when considering the suitability of MIS among geographic areas.