DEMOGRAPHY OF TWO ENDEMIC FOREST-FLOOR MAMMALS OF SOUTHEASTERN ALASKAN TEMPERATE RAIN FOREST

Abstract

We studied demography of the Keen’s mouse (Peromyscus keenimacrorhinus) and the Wrangell Island red-backed vole (Clethrionomys gapperi wrangeli) in the Alexander Archipelago during 1998–2000 because of concerns over population viability from extensive clear-cut logging of temperate rain forest in the region. We trapped 1-ha grids and assessment lines with live traps during spring and autumn to compare populations among gap-phase oldgrowth, multicohort old-growth, peatland mixed-conifer, and thinned young-growth (23-year-old) forests. Generally, gap-phase old growth and peatland mixed conifer supported the highest and lowest populations of voles, respectively. One notable exception was during autumn 1998, when vole population levels were highest and density was higher (P , 0.02) in young growth than gap-phase old growth. Mean body mass, minimum summer and overwinter survival, age and sex composition, and percentage reproductive females did not differ among habitats. For Keen’s mouse, density was highest in 1998; overall, populations were highest in young growth and lowest in peatland mixed conifer. Mean body mass and minimum summer and overwinter survival did not differ among habitats, but fewer reproductive females were recorded in multicohort than in gap-phase old growth, peatland mixed conifer, or young growth. Our results suggest that C. gapperi populations in southeastern Alaska are not as sensitive to canopy removal as has been indicated elsewhere in western coniferous forests and that P. keeni populations in southeastern Alaska flourish in a variety of habitats. If the results of our study can be generalized across southeastern Alaska, peatland mixed conifer likely contributes little to breeding populations of C. gapperi and thus is unlikely to mitigate any effects of broad-scale clear-cut logging of old-growth forests.