A new method for marking slugs by ultraviolet-fluorescent dye

We introduce a new, cheap, fast and reliable method for marking slugs, using biologically inert UV-fluorescent dye. The dye remained visible for more than 3 months in all individuals marked. Use of the dye did not affect survival, spatial behaviour or daily activity of the slugs, nor the prey choice of the predatory beetle Pterostichus melanarius, under controlled semi-natural conditions. The new method will enable further investigations of absolute slug densities, diurnal activity, mobility and dispersal, using capture-recapture techniques. The resulting data would allow the construction of more exact forecasting models for the population dynamics of pest slugs, potentially leading to a reduction in the use of control agents, particularly chemical molluscicides.