Movement behaviour of woodland rodents: looking from beyond small trapping grids

Live-trapping of rodents was conducted over a 12-ha plot on unevenly spaced trap lines, with inner lines forming a 3.5-ha grid of closely spaced traps. This design was used to estimate the probability that bank volesClethrionomys glareolus (Schreber, 1780) and yellow-necked miceApodemus flavicollis (Melchior, 1834) trapped in small grids are true residents rather than visitors from the surrounding area. On average, 12% of the voles and 19% of the mice were trapped within and beyond the grid in the same trapping sessions. As these were mainly wide-ranging males moving over the plot, home ranges of males may be underestimated on small grids. In total, 36% of voles and 39% of mice that were marked in spring-summer were trapped at least once in their life beyond the grid. Typically, these were individuals shifting home ranges and migrating to or from the grid. The size of lifetime ranges of rodents was significantly larger than temporary home ranges and may therefore be underestimated on small grids. “Single--capture” individuals were mainly true transients rather than visitors. Only 12% of voles and 15% of mice resided on the plot for longer time than in the grid.