POPULATION DENSITY OF RESIDENT AND NON-RESIDENT FOREST SMALL MAMMALS

When assessing the abundance of small mammals using traditional methods, an abundance index, the number of individuals per unit of trapping effort, is usually applied. Due to the different relationships of species to various traps and baits, the true ratio of species in nature may not coincide with the estimated one. In most cases, the presence of a non-resident component in the population size remains outside the attention of researchers, while dispersal is a key element for many demographic processes. A method is proposed for calculating the density (individuals per area) of resident and non-resident animals when using mark-recapture live-traps arranged in lines. For three mass species of small forest mammals (red-backed voles, common shrew and masked shrew), the dynamics of the density of the resident and non-resident population were studied over 18 years. In most cases, the red-backed vole dominated the population of small mammals. According to long-term average data, the proportion of non-resident individuals in the population of the three species did not differ, averaging 12.6% of the total density. The dependence of the level of non-resident activity in the red-backed vole on the density of resident animals was shown. In shrews, the density of non-residents did not depend on the density of resident ones. The technique allows for a wide range of ecological problems to be solved and it can be used to monitor the state and structure of communities of small mammals.