Piñon Mouse
Order: Rodentia
Family: Muridae
Peromyscus truei (Shufeldt)
Description. A moderately large, large-eared, white-footed mouse; tail as long as, or slightly longer than, head and body and scantily haired; upper parts ochraceous buff mixed with dusky giving an overall effect of cinnamon or tawny olive in unworn pelage and wood brown in worn pelage; the pronounced lateral line is ochraceous buff; sides of face and nose grayish; ears dusky; feet and underparts white; tail dark above, white below. External measurements average: total length, 204 mm; tail, 100 mm; hind foot, 22.5 mm; ear, 22.2 mm.
Distribution in Texas. In Texas, known from the caprock at the eastern edge of the high plains in Armstrong, Briscoe, and Randall counties and in the Trans-Pecos from the Guadalupe Mountains in Culberson County.
Habits. This species is restricted to rocky situations in cedar forests on the canyon slopes and floors in the Palo Duro Canyon region. Areas in the juniper-mesquite association that have large, massive boulders seem to support the highest populations. Even so, intensive trapping produces few mice. James Tamsitt reported that in 1,803 trap-nights he captured only 25 specimens — a success ratio of 72 trap-nights per mouse caught. In Guadalupe Mountains National Park, the species is rarely found in the juniper and pinyon woodlands.
The food habits of these mice are not well known. In California, specimens examined in midsummer had been eating primarily insects and spiders although by late summer their diet was predominantly acorn mast. In Colorado, the winter diet is primarily juniper berries.
Breeding habits are likewise poorly known. In southwest Colorado, breeding occurs from April through September and in Arizona, from February through November. One specimen captured July 24 in the Guadalupe Mountains of the Trans-Pecos was an adult female pregnant with four embryos. Litter size ranges from three to six, average four. At birth, the young are hairless and the eyes and ears are closed. Between 2 and 3 weeks of age the eyes and ears open. The body is haired by 2 weeks of age.
Remarks. The Texas population of P. truei has had a rather confusing taxonomic history. Frank Blair recognized it as a new species in the P. truei group of mice and in 1943 gave it the name Peromyscus comanche. Donald Hoffmeister in 1951 placed comanche as a subspecies of Peromyscus nasutus and 10 years later he and Luis de Ia Torre transferred both nasutus and comanche to the largely Mexican species Peromyscus difficilis. In 1972 Raymond Lee and associates examined the karyotypes of comanche and found them to be identical with those of Peromyscus truei and markedly different from those of Peromyscus difficilis. Finally, in 1973 one of us (Schmidly) reviewed its systematic status and placed comanche as a subspecies of Peromyscus truei.
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