Mexican Woodrat
Order Rodentia : Family Muridae : Neotoma mexicana Baird

Description. Medium-sized, about as large as the white-throated woodrat but white hairs of entire underparts usually buffy basally, not white to roots; first upper molar with deep anterointernal re-entrant angle; upperparts grayish buff, moderately darkened over back by blackish hairs; tail brownish above, white below. External measurements average: total length, 300 mm; tail, 125 mm; hind foot, 28 mm. Weight, 140-185 g.

Distribution in Texas. Known only from Trans-Pecos Texas, where it occurs in mountainous regions of Brewster, Culberson, Hudspeth, Jeff Davis, and Presidio counties.

Habits. These rats frequent rimrocks, canyon walls, and other rocky areas where they establish themselves in cracks and crevices. Into these retreats they carry considerable quantities of rubbish with which to build their nests. Preferring to construct their dens among the cracks and crevices of boulders and other rocky situations, these woodrats do not build elaborate, above ground nests as do other woodrats. Where rocky retreats are not available they construct houses about the roots of trees, in hollow logs, and in piles of logs, or they may take up residence in deserted or little-used cabins. Where they occupy dens among the rocks, their presence is usually evidenced not only by the piles of rubbish at the entrances but also by copious deposits of elongated, capsule-shaped fecal pellets on rocky shelves or in niches in the rocks. Seemingly, they establish regularly used sites for defecation.

Their food consists of a variety of plants, including green vegetation, nuts, berries, acorns, and fungi. Much of their range is above the limits of growth of cactus, so these plants do not figure importantly in their diet although, if available, they are eaten with relish.

The breeding season of this species extends from early spring through summer in the Trans-Pecos. In Colorado, nearly all adult females produce two litters in quick succession. Litter size for adult females is two to five (average 3.4); that for young females averages 2.4. The gestation period ranges from 31 to 34 days. At birth the young rats weigh 9-12 g. Growth is rapid and young females reach sexual maturity in about a month. Females born in April and May often produce litters of their own in June and July while they are still partly or wholly in the gray, juvenile pelage. Young males, however, do not become sexually mature until the following year when they are 8 or 9 months old.

Since the range of these rats is confined largely to mountainous areas, the rats ordinarily do not conflict seriously with man’s economy but they may rifle mountain cabins and the camps of vacationers.