Why not just open the current images, and in a separate layer, paint the paths they seem to walk alot? Keep in mind things like where wet footprints appear. Then just add a layer between the two, and put your changes (or an entirely new map) on that layer. That way you'll have the original map underneath for reference, and the 'common paths' on top.

Keep in mind that they walk straight-line paths until they hit something - they only use more complex pathing if they encounter an obstacle. For this reason, many paths are not natural. (They will not walk toward the edge of a wall, they'll walk right into it, then start to go around.)