Ecological and statistical analysis of long-term changes in the abundance of small mammals at the northern limit of the range (Northeastern Ladoga region)

Data on the abundance of 11 species of small mammals, which were collected in the northeastern Ladoga region in 1965–2013, were analyzed using harmonic and component tests. In scarce species, mostly random nonperiodic changes in abundance were observed, whereas abundant species showed consistent periodicity of changes at a frequency of 3.6–5.6 years. The sets of spectral-density curves for all species were processed by the component analysis. For rodents, a 3–5-year periodicity was found, whereas shrews showed a long-term trend in abundance with an increase in the 1970s and subsequent decrease. Sufficiently distinct periodicity in the population dynamics of animals was manifested more clearly in the counts performed with break-back traps rather than with pitfall traps.