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MEXICAN WOODRAT
Neotoma mexicana Baird 1855

Order Rodentia : Family Cricetidae

DESCRIPTION. Medium size, about as large as the white-toothed woodrat, but white hairs of entire underparts usually buffy basally, not white to roots; first upper molar with deep antero-internal reentrant angle; upperparts grayish buff, moderately darkened over back by blackish hairs; tail brownish above, white below. Dental formula: I 1/1, C 0/0, Pm 0/0, M 3/3 × 2 = 16. Averages for external measurements: total length, 300 mm; tail, 125 mm; hind foot, 28 mm. Weight, 140–185 g.

Neotoma mexicana

DISTRIBUTION. Known only from rocky areas at mid to high elevations in Trans-Pecos Texas, where it is common in the mountainous regions of Brewster, Culberson, Hudspeth, Jeff Davis, and Presidio counties.

Distribution of Neotoma mexicana

SUBSPECIES. Neotoma m. mexicana.

HABITS. These woodrats frequent rimrocks, canyon walls, and other rocky areas at mid to high elevations, where they establish themselves in cracks and crevices among shrubland or wooded areas. Preferring to construct their dens among the cracks and crevices of boulders and other rocky situations, these woodrats do not build elaborate, aboveground middens as do other woodrats. Instead, they carry considerable quantities of rubbish into the crevices and build their middens accordingly. 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 sticks and cacti 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. In contrast to N. leucodon, N. mexicana exhibits a strong distaste for cactus. Also unlike N. leucodon, N. mexicana regularly stores large quantities of food, presumably for winter consumption. Mexican woodrats typically reside at higher elevations than do white-toothed woodrats and thus face longer, colder winters and possible food shortages during that time.

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 1 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 they are 9 months or so old.

Given that the range of these rats is confined largely to mountainous areas, the rats ordinarily do not conflict seriously with humans, but they may rifle mountain cabins and the camps of vacationers.

POPULATION STATUS. Common. Although somewhat isolated in the mid to high elevations of the major mountainous regions in the Trans-Pecos, the Mexican woodrat is common throughout its range.

CONSERVATION STATUS. The IUCN lists the Mexican woodrat as a species of least concern, and it does not appear on the federal or state lists of concerned species. It does not appear to face any serious threats in our state.

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From The Mammals of Texas, Seventh Edition by David J. Schmidly and Robert D. Bradley, copyright © 1994, 2004, 2016.  Courtesy of the University of Texas Press.

Natural Science Research Laboratory