Both species eat pinyon and juniper seeds; since _P. truei_ lives in the forest, it has better access to these foods than does _P. maniculatus_. Mice remove the embryos of juniper seeds by chewing a small hole in the larger end of the seed. The seed coats of juniper are extremely hard, and a considerable amount of effort must be expended to remove the embryo. Captives discarded the resinous and pithy, outer layers of juniper berries. Individuals of _P. truei_ are adept climbers. Since many juniper berries remain on branches throughout the winter, the ability of these mice to forage in the trees would be especially advantageous when snow covers the ground. WATER CONSUMPTION _Peromyscus maniculatus_ is ubiquitous, occurring in habitats ranging from mesic boreal forests to arid southwestern deserts. Most subspecies of _P. maniculatus_ live in moderately mesic or near-mesic environments, but a few have adapted to arid conditions. It has been assumed that the success of _P. maniculatus_ in inhabiting such diverse habitats is associated with its adaptability to different kinds of food and varying amount of available water (Williams, 1959b:606). Throughout its range _P. maniculatus_ coexists with one or more other species of _Peromyscus_ that are more restricted in distribution. _Peromyscus truei_ is one such species. Both species live under xeric or near-xeric conditions, for the climate of Mesa Verde is semi-arid. Other than a few widely-scattered springs, there are no sources of free water on the top of the Mesa Verde land mass; thus animals inhabiting the park must rely upon moisture in the plants and other foods they eat, or upon dew. Several investigators have studied water consumption in mice of the genus _Peromyscus_ (Table 7). Dice (1922) did so for the prairie deer mouse, _P. m. bairdii_, and the forest deer mouse, _P. leucopus noveboracensis_, under varying environmental conditions. He found that both species drank about the same amounts of water per gram of body weight, and that food and water requirements did not differ sufficiently to be the basis for the habitat differences between these species. Neither of his samples was from an arid environment. Chew (1951) studied water consumption in _P. leucopus_, and recently reviewed the literature on water metabolism of mammals (Chew, 1965). In his studies of five subspecies of two species of _Peromyscus_, Ross (1930) found significant differences in water consumption between species but not between subspecies within a species. One of the subspecies of _P. maniculatus_ tested was from a desert region, whereas the other two were from mesic areas along the coast of California.