Aspects of red squirrel (Tamiasciurus Hudsonicus) population ecology in interior Alaska

Abstract

Red squirrel (Tamiasciurus hudsonicus preblei) population ecology was investigated in a field study conducted between 21 September 1967 and 30 October 1968 near College, Alaska. Population density on the 21 ha study area was one squirrel per 1.1 ha during the spring 1968 and one per 1.2 ha during the fall 1968. Territoriality appears to be somewhat relaxed during the spring, and there are non-territorial squirrels present at that time. Young of the year squirrels can be distinguished from adults, at least through October, according to the degree of closure of the epiphyses of the radius and ulna. Immature males can be distinguished from adults on the basis of testis weight during the fall. Immature squirrels constituted 57.1% of the population sample during the fall 1967 and 51.3% during the fall 1968. Males formed 66.7% of the sample of adults and 64.0% of the sample of immature squirrels. Males were not significantly heavier or larger than females. Mean tail length of immature squirrels exceeded that of adults. Fall molt commences for all red squirrels during late August and September. The spring molt commences for females during March, whereas males do not molt until May. Testes measurements and female reproductive condition indicate that there is a single annual reproductive season, from late February through April. Squirrels breed during their first spring at about 10 to 11 months of age. Estimated mean litter size was 4.20 based on embryo counts and 3.92 based on placental scars. The most frequent litter size was four.