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.
A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness of slopes. contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value.