CHARACTERISTICS OF AMERICAN MARTEN DEN SITES IN WYOMING

We examined characteristics of den structures and den sites used by fe male American marten (Martes americana) for natal and maternal dens in the Sierra Madre Range, Wyoming. During 1988-95, we located 18 natal dens (parturition sites) and 97 maternal dens (sites where kits were p resent exclusive of parturition) used by 10 female marten. Important d en structures included rock crevices (28%), snags (25%), red squirrel (Tamiasciurus hudsonicus) middens (19%), and logs (16%). Resource sele ction function (RSF) analysis showed that an individual selection mode l provided a significantly better fit than a null model or pooled sele ction model, indicating that the sample of marten selected maternal de n sites that differed from random sites, and that individual animals d id not select maternal den sites in the same manner. Six marten indivi dually exhibited significant selection for maternal den sites within h ome ranges. Overall selection coefficients for maternal dens indicated the number of squirrel middens was the most important variable, follo w ed by number of snags 20-40 cm diameter at breast height (dbh), numb er of snags greater than or equal to 41 cm dbh, and number of hard log s greater than or equal to 41 cm in diameter. Selection of natal den s ites was also significant via comparison between selection and no-sele ction models, with number of middens, number of Engelmann spruce (Pice a engelmannii! and subalpine fir (Abies lasiocarpa) >20 cm dbh, and nu mber of hard logs greater than or equal to 41 cm in diameter the most important variables in descending order of importance. Large logs, lar ge snags, and large, live spruce and fir trees are important character istics for marten den sites in the central Rocky Mountains. The promin ence of middens at den sites suggests red squirrels provide important denning structures as well as prey for marten.