Optimum habitats for _P. maniculatus_ were on Navajo Hill, in the burned areas on Morfield Ridge, on the northern end of Wetherill Mesa, and in the grassy areas near the entrance of the park. The trapping areas in the first three mentioned had heavy growths of grass and an overstory of shrubs. Some individuals of _P. maniculatus_ ventured into pinyon-juniper woodland and entered traps. Such animals usually were found in places having a heavy understory of sagebrush, or in disturbed places within the woodland. _P. maniculatus_, but not _P. truei_, was taken in the arid pinyon-juniper-bitterbrush stand on the southern end of Wetherill Mesa. _P. maniculatus_ also was present, in about equal numbers with _P. truei_, in a pinyon-juniper-muttongrass stand north of Long House. Both of these localities supported only a few mice. _P. maniculatus_ is found more frequently in pinyon-juniper woodland when the population density is high, and when such woodlands adjoin grasslands or sagebrush areas. As mentioned earlier, _P. truei_ and _P. maniculatus_ occur together in ecotonal areas between the forest and grassy or brushy areas. In Mesa Verde the deer mouse inhabits exposed grassy areas that have mostly shrubs in the open canopy. _P. maniculatus_ is the first to colonize areas that have been burned; this species invades such areas as soon as primary successional vegetation becomes established. It can be stated that in general, _P. maniculatus_ will be found in the harsher, more arid habitats. If the habitat is so inhospitable that only a few mice can survive there, _P. maniculatus_ will be present. _P. truei_ apparently requires the more moderate conditions found in the pinyon-juniper forest, and this species does not venture far from the edge of the forest. NESTING AND NEST CONSTRUCTION Ten individuals of _P. truei_ and three of _P. maniculatus_ were followed to their nesting places. Photographs were taken of the nesting sites before and after uncovering. Plants or other materials used in their construction and any commensal arthropods present were saved and later identified.