ADVANCES IN APPLIED ECOLOGICAL TECHNIQUES A novel mark–recapture technique and its application to monitoring the direction and distance of local movements of rangeland grasshoppers (Orthoptera: Acrididae) in the context of pest management

Abstract

Summary 1. Rangeland grasshopper movement was studied in Wyoming, USA, with respect to the biological and ecological factors (population density, developmental stage and weather) influencing net displacement and directionality. 2. A novel adaptation of the mark–recapture method was developed to monitor grasshopper dispersal. The method used fluorescent powder and resighting marked grasshoppers in the field with ultraviolet light, rather than physical recapturing of individuals. 3. Rangeland grasshoppers exhibited a strong tendency for directional movement. Adult grasshoppers demonstrated a significant tendency for dispersal in a north‐westerly direction across a range of population densities (5–8, 10–15 and ≥ 18 grasshoppers m –2 ). Although not a definitive explanation, weather might have influenced this behaviour, as the grasshoppers consistently moved upwind. 4. The mean displacement of grasshoppers in a 36‐h period ranged from 2·3 m in nymphs to 3·7 m in adults, with the distance of displacement being positively correlated with population density. 5. An understanding of grasshopper movement in terms of directionality and displacement has immediate applicability to reduced agent–area treatments for rangeland grasshopper management.