ON THE EFFECTIVENESS OF TRAP-LINE METHOD FOR STUDY OF THE ABUNDANCE AND POPULATION-STRUCTURE OF BANK VOLE (CLETHRIONOMYS-GLAREOLUS)

The estimation of abundance and the structure of population of bank vo le was carried out throughout 6 years in the optimum of the species ra nge. Trap-line (<<relative census>>) and capture-mark-release (CMR, << absolute census>>) methods were used for comparative study. The study showed, that the standard trap-line method enables the estimation of r eal values of the index of dominance and the pattern of population dyn amics. The strict positive correlation between absolute and relative n umbers (number of voles per 1ha and number of voles per 100 trap-night s resp.) was revealed. However, the increase of relative values is con siderably reduced at high population densities (100 and more voles per 1ha). The indices were counted and the regression equations were foun d to transform the relative estimates into the absolute ones for diffe rent demographic situations. Some differences in the age and sex struc ture of populations were observed using both methods only during the p eriod of active breeding. These differences are, probably, caused by d ifferent time of trapping (5 to 6 days in the CMR method, 1 day in tra p-line method). The conclusion is made, that the trap-line method can be used with certain corrections for demographic studies of bank vole.