Depends on what kind of mouse though. Woodmice are normally tolerated as they're quite cute and live mostly outdoors. But infestations of house mice are something that local authorities/pest control are regularly called out to deal with in the UK. If they can get in and get a toe-hold, especially where they've found a good food source, then they can run riot.
INDEX CONTOUR LINE A bolder/wider brown line that has the elevation value marked at various intervals as a part of the line. These contours typically occur every fifth line. Use an index contour near the point for which you are trying to find the elevation as a first step to determining the elevation of that point. Example of an index contour. This is the basic symbol that you will use to determine the elevation of a feature or location. It is a brown line on a topographic map and represents a line of equal elevation. All locations that a contour lines crosses have the same elevation at that point.
Contour lines are lines drawn on a map connecting points of equal elevation. If you walk along a contour line you neither gain or lose elevation. Picture walking along a beach exactly where the water meets the land (ignoring tides and waves for this example).he example at right is a section of a topographic map. The brown lines are the contour lines. The thin lines are the normal contours, the thick brown lines are the index contours. Notice that elevations are only marked on the thick lines.