Within the woodland the population of woodrats was not evenly distributed even at its maximum density; only those situations that provided sufficient overhead shelter were occupied by woodrats. The hilltop limestone outcrop, which was the refugium of the survivors when the population was at low ebb, also supported the greatest concentration when the population was high. The number of individuals living along any particular stretch of ledge could be determined only by intensive live-trapping, whereas residences of individuals could be more readily identified in most other situations away from the ledge. Stick houses of woodrats are, characteristically, large and dome-shaped in woodland, but along the ledges they usually lacked this typical form and consisted of a much smaller accumulation of sticks, often merely filling a small crevice. Sticks carried into such places where they were partly or wholly protected from moisture and sunshine were much less subject to decay than those in more open situations, and remained long after the rats themselves were gone. Accumulations of droppings in depressions in rock surfaces beneath overhanging ledges likewise have lasted for many years. The rock outcrop provided a continuous travelway along the hilltops, and even parts that were not permanently occupied usually had some sign. The following types of situations were found to be especially favorable for occupancy: deep crevices beneath overhanging projections of the ledge; large flat boulders broken away from the main ledge; thick clumps of brush (usually fragrant sumac, _Rhus trilobata_) providing shelter and support for the house; logs fallen across the ledge providing support and protection for the house structure. A second outcropping limestone stratum approximately 20 feet below the level of the hilltop was just as extensive as the upper outcrop, but it was little used by the rats because the exposed rock surface was more regular, lacking the jagged cracks and deep fissures of the hilltop outcrop; and it lacked the overhanging projections which provided overhead shelter for the rats along the upper outcrop. More than ninety per cent of the rats that were recorded as associated with the outcrops were at the hilltop stratum. Second in preference to the hilltop outcrop as a house site was the base of an osage orange tree in thick woods. This tree occurs throughout the woodland of the Reservation, having become established when the leaf canopy was more open, and the whole area was subject to grazing, with less development of the understory vegetation in the woodland. Houses were most often situated in those osage orange trees that had been cut one or more times, and had regenerated with spreading growth form, the multiple branching stems offering substantial support. Occasionally houses were built in crotches from two to six feet above ground.