After twenty‐seven years of human absence on Hirta, the St. Kilda field‐mouse population in the Village Glen was numorically unaffected over two years, by a large‐scale military task‐force operation. The movements of field‐mice were experimentally examined. The trap revealed home range of a breeding male was about three‐quarters of an acre. Mice transported distances of up to 1,600 feet were able to return to the trap‐site in probably less than three hours. Fewer were able to do this over 2,800 feet. Mice were able to move up‐and downhill with equal facility. More mice were caught in the hour during and after dusk, than during the remainder of the night. A detailed s