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  The Mammals of Texas - Online Edition

Brush Mouse
Order Rodentia : Family Muridae : Peromyscus boylii (Baird)

Description. A medium-sized, long-tailed, white-footed mouse; tail equal to or longer than head and body, sparsely haired, slightly tufted and indistinctly bicolor, darker above; ankles dusky, the feet white; ears moderately long (19-22 mm from notch); proximal two-fifths of sole of hind foot hairy; upperparts pale cinnamon or hair brown to sepia; sides with narrow ochraceous buff lateral line; underparts white. External measurements average: total length, 197 mm; tail, 103 mm; hind foot, 22 mm. Weight, 22-36 g. Distinguished from P. difficilis chiefly by smaller ears and shorter fur; from P. pectoralis by dusky instead of white ankles.

Species distribution mapDistribution in Texas. Trans-Pecos region and along escarpment of Llano Estacado and in adjacent parts of Panhandle.

Habits. These mice are usually associated with brush and trees, but they have been trapped in a number of habitats including stream banks, rock walls, talus slopes, and cabins. In the Guadalupe Mountains of western Texas, they are common in the open pine-fir forest at 2,400 m where they show a decided preference for areas of down logs and brush piles. Vernon Bailey remarks that they seldom burrow into the ground but rather utilize any natural cavity that offers concealment and protection. The nest is a globular structure of dry plant fibers, mostly grasses.

They are adept at climbing. Victor Cahalane observed that several mice, upon escaping from his live traps, fled into trees in preference to running on the ground. They climbed easily, but not fast, and seemed to be at home off the ground. Without doubt they garner much of their food in trees and utilize hollows in them for dens. They are almost entirely nocturnal in habit and are active the year round.

They feed on a variety of plant items. In the Guadalupe Mountains, they feed extensively on pine nuts and Douglas fir seeds; in the oak belt, acorns are a favorite item. They also feed on hackberries, juniper berries, and cactus fruits.

The breeding season extends through most of the year. Gravid females have been taken from May to December, but the presence of half-grown young in May indicates that breeding begins as early as March or April. Several litters of two to five (average three) young may be reared in a year, but the peak of production is in spring and early summer. The young are blind and hairless and weigh about 2 g at birth.

Usually these mice are of little or no economic importance except in instances where they occur in numbers around and in cabins and granaries in wooded areas. In such instances they can be removed readily by trapping.