Carabid movement and vegetation density: Implications for interpreting pitfall trap data from split-field trials

This paper presents data from an extensive study of a carabid beetle, commonly dominant in agricultural habitats, within a split-field trial with different vegetation density in each half-field. Pitfall trapping provided data on activity-density and spatial distributions. Mark–release–recapture data estimated absolute population density and quantified individual movements within and between the two half-fields. The results revealed extensive population exchange between half-fields, both within areas of the same crop and between different crops. Activity was strongly influenced by vegetation density such that pitfall trap activity-density data indicated significant differences between treatments when there were none between absolute population density estimates. Field data and simulation models showed that movements of individuals between treatments differing in vegetation density can be substantial and directionally biased.