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.
The contour interval of a contour map is the difference in elevation between successive contour lines. More generally, a contour line for a function of two variables is a curve connecting points where the function has the same particular value. The gradient of the function is always perpendicular to the contour lines.