Spring Populations of Small Mammals in Central Swedish Lapland in 1964-68

During five springs, 1964-68, small mammal populations in the Ammarnds mountain area in northern Sweden were examined for density, reproduction, age, weight and food. Increase, peak and decrease in numbers were observed to be accompanied by a gradual deterioration in physiological condition. The frequencies of food items during the spring, mainly mosses and invertebrates, did not show any pronounced differences between years but differed between species. The barking of trees and bushes during the peak winters was examined regarding plant species and abundance. With the aid of earlier investigations in the same area three cycles of about three years can be established since 1959. The population peaks were terminated, at least indirectly, by food shortage whereas spring declines are best explained by predator influence. Pe3loMe