Estimation of Absolute Abundance in Small Mammals. Let a Line Has an Area.

Small mammals play an important role in ecosystems. Changes in their numbers make it possible to monitor environmental changes, and robust estimates of population density is crucial. Capture-mark-recapture (CMR) on grid, an established method for estimating small mammal population density, is costly and labor-intensive. The cost of the survey can be reduced by reducing observation time, as well as by increasing sample size by arranging traps in a line. Using our 9-yers data obtained on grid we test whether relative abundance indices calculated over shorter time periods correctly reflect population density. We also propose a method for calculating population density using data obtained by CMR on lines (since the grid can be viewed as a series of independent lines) by estimating the spatial activity of animals. It was found that all the indexes calculated for grid and lines were in good agreement with population density on greed, and the scale of both interspecies and inter-annual differences in indexes and density was similar. Although indexes significantly correlated with population density since 3rd day, reliability of the indexes increased over the time of observations ( R ²  > 0.79 since 7th day). The population density calculated from the lines using the proposed method was in good agreement with the actual density recorded on the grid ( R ²  > 0.9). We could recommend using the indexes to estimate inter-annual changes in population abundance and community structure at the same area under invariant trapping protocol with invariant time of the trapping sessions. Density calculated on lines requires long-term study, but it is a universal estimate, and could be used when rough assessment of absolute abundance is needed.