PARENT SESSION

FACTORS AFFECTING THE DISTRIBUTION AND USE OF DUSKY-FOOTED WOODRAT (NEOTOMA FUSCIPES) HOUSES. Robin J. Innes¹, James A. Wilson¹, Dirk H. Van Vuren¹, Douglas A. Kelt¹ and Michael B. Johnson². ¹ Wildlife, Fish and Conservation Biology Department, University of California, Davis, CA, USA; ² John Muir Institute of the Environment, University of California, Davis, CA, USA.

ABSTRACT- The dusky-footed woodrat (Neotoma fuscipes) is an important prey species of the California spotted owl (Strix occidentalis), a species of concern in California. We examined the factors influencing the distribution and use of woodrat houses within mixed-conifer forests of the northwestern Sierra Nevada, California. From July to October 2003, we captured 44 N. fuscipes (23 F, 21 M) and located 60 stick houses. We radio located 20 woodrats (11F, 9 M) and live-trapped at 41 houses to determine the degree of house use. We measured habitat variables in 4 m radius plots centered about houses (n=20) and random locations (n=20). Fifty-four percent of houses were occupied by woodrats, although up to 93% were visited. We used the Mann-Whitney-U test to examine differences among occupied/visited houses and random points. We found that placement of houses was associated with greater percent canopy closure (P<0.02) and greater cover by large (>50 cm dia.) woody debris (P<0.01) compared with random locations, suggesting that woodrats favor shaded houses in and against trees and/or large logs. In addition, woodrats used houses with relatively higher tree species diversity (P< 0.04) than was present at random locations. Houses had fewer total stems <1 m in height (P<0.005), and generally more stems >2m tall/<5 cm dbh (P<0.11). Our data suggest that woodrats evidently favored house locations with greater woody cover over the house and may be responding to habitat variables differently than in other woodrat populations.

KEY WORDS: dusky-footed woodrat, Neotoma fuscipes