Density and occupancy results when grey squirrels have been introduced everywhere in Scotland. Here (a) shows the red squirrel density, (b) the grey squirrel density and (c) the occupancy results for (i) the simulation where no grey squirrel trapping was applied and (ii) the simulation where grey squirrel trapping (approx. 18 trap days per year) is applied to each grid square that contains grey squirrels. A grid square is classed as being occupied if there are 2 or more individuals of any species present. The 19 designated strongholds (Scottish Forestry 2020) are outlined in black.