Demography of the longtail vole Microtus longicaudus in seral stages of coastal coniferous forest, southeast Alaska

Abstract

Microtus longicaudus is atypical of its genus as it most often occupies a shrubby rather than grassy habitat where it exists at low densities. Populations were monitored by biweekly livetrapping in three logged habitats and in an old-growth area during three reproductive seasons in order to investigate the relationship between habitat and demography. The most consistently high population densities were observed on a 7 to 10-year-old clear-cut. Densities were positively correlated with log and shrub cover within and between grids and with herb cover at a between-grid scale only. Habitat selectivity was higher at low densities. Densities declined on all grids during the 3rd year of the study; this resulted from poor overwinter survival on three grids and poor recruitment on one grid. Adult males survived poorly in relation to adult females during the breeding season and over winter. Consistently low overwinter survival and low growth rates of adults and juveniles on the 23 to 26-year-old clear-cut were associated with low nitrogen content of shrub species; dicot leaves constituted 30% of the adult diet. Fruit and seeds comprised 67% of the juvenile diet, and their phenology may be an important determinant of reproductive patterns.