The woodmouse is primarily a woodland species but it also occurs on maritime sand-dunes. The home ranges of mice living on the sand-dunes are much larger than those of animals living in woodlands. Here we test the hypothesis that this difference is due to the fact that woodland provides substantially more food than do sand-dunes. Our experimental approach was to provide supplementary food in the form of wheatgrain to a sand-dune population and to compare range sizes with a control population. Range sizes on the supplemented area were significantly smaller than the controls and essentially similar to those of woodmice living in deciduous woodland.