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. When the lines are close together the magnitude of the gradient is large: the variation is steep.