Outdoors, rats are found nesting outside in trees, woodpiles, under decks and foundations, along the banks of rivers and ponds, and in areas of dense vegetation or debris while mice are more commonly found nesting in tree stumps, woodpiles, in dense vegetation, or in the abandoned nests of birds or other small animals. When invading homes, these rodents often nest behind walls, in attics or basements, in crawl spaces, behind appliances, or underneath sinks.