Bushy-tailed woodrat abundance in dry forests of eastern Washington

We studied bushy-tailed woodrats (Neotoma cinerea occidentalis) in the eastern Washington Cascade Range to estimate their density and survival in 3 typical dry forest cover types. We predicted woodrat density to be high, moderate, and low in mature mixed-conifer forests, young mixed-conifer forests, and open ponderosa pine forests, respectively. We livetrapped on 8 x 8 grids (280 m) over an 8-day period each autumn for 4 years to obtain Huggins mark-recapture estimates of woodrat density. We captured woodrats 617 times and marked 193 individual woodrats in 12 sample stands during 42,165 trap nights. The sex ratio of captures was 62% female and 38% male. Adults made up 79% of captures. Woodrat density averaged 0.49 animals/ha among all cover types and years; woodrat density did not differ among types. Regardless of cover type, stands fell into 4 woodrat-density groups, with densities ranging from 0.13 to 0.93 woodrats/ha. Classification tree analysis revealed that woodrat-density groups could be predicted well (proportional reduction in error = 0.73 to 0.89) by the type and amount of cover provided by large snags, mistletoe brooms, and soft downed logs. Over the 4-year period, woodrat density ranged from 0.28 animals/ha to 0.87 animals/ha, increasing each year at a rate of lambda = 1.8 consistently among cover types. A moderate (r = 0.55) density-dependent response in per capita rate of increase was detected. The apparent annual survival rate was a low 0.14. Management to reduce woody fuels and to restore low-intensity high-frequency fire regimes in ponderosa pine and dry Douglas-fir forest likely will reduce bushy-tailed woodrat populations unless prescriptions can mitigate the loss of snag, mistletoe, and downed log cover.