Distribution of the White-ankled Mouse (peromyscus Pectoralis) in New Mexico

The white-ankled mouse (Peromyscus pectoralis) was previously known only from Carlsbad Caverns National Park and nearby areas in extreme southeastern New Mexico. I discovered 15 new localities for P. pectoralis, which extend its distribution 225 km north-northwest. This new distribution does not represent a recent northward expansion of P. pectoralis in New Mexico but reflects the lack of mammalian surveys in the region and misidentification of museum specimens from past surveys. At present, the distribution of P. pectoralis in New Mexico includes the Guadalupe Mountains and lowland habitats between the Sacramento Mountains and Pecos River. RESUMEN Previamente, el ratón de tobillo blanco (Peromyscus pectoralis) sólo se conocı́a en el Parque Nacional de las Cavernas de Carlsbad y localidades adyacentes en el extremo sureste de Nuevo México. Descubrı́ 15 localidades nuevas para P. pectoralis que extienden su distribución 225 km hacia el nor-noreste. Esta nueva distribución no representa una expansión reciente de P. pectoralis en Nuevo México sino que refleja la falta de muestreos de mamı́feros en la región y la mala identificación de especimenes en museos de muestreos anteriores. Hoy en dı́a, la distribución de P. pectoralis en Nuevo México incluye las Guadalupe Mountains y los hábitats de tierras bajas entre las Sacramento Mountains y el Pecos River. The white-ankled mouse (Peromyscus pectoralis) occurs from central Mexico north to extreme southern New Mexico and Oklahoma (Hall, 1981). Throughout its range, this mouse is associated with rocky substrates in a variety of habitats, including deserts, grasslands, and woodlands (Schmidly, 1974; Schmidly, 1977; Dalquest and Stangl, 1986; Matson and Baker, 1986; Hanchey and Wilkins, 1998). In New Mexico, P. pectoralis previously was documented only from the southwestern portion of Eddy County (Fig. 1). Here, the rugged and rocky Guadalupe Mountains dominate the landscape with a substrate of exposed limestone and dolomite ( Jagnow and Jagnow, 1992). All previously published records of P. pectoralis in New Mexico are from these mountains and adjacent rocky habitats (Findley et al., 1975; Geluso and Geluso, 2004). Much of our knowledge about the biology of this mouse in New Mexico comes from Carlsbad Caverns National Park (Geluso and Geluso, 2004). Although most of the park lies in the Guadalupe Mountains, a small portion also is located in the lowlands along the base of these mountains. Peromyscus pectoralis occurs in rocky habitats in both regions of the park at elevations of 1,128 to 1,951 m. In the mountainous portion, it is abundant on summits, canyon sides, and canyon floors dominated by junipers (Juniperus), oaks (Quercus), smooth sotol (Dasylirion leiophyllum), lechuguilla (Agave lechuguilla), acacias (Acacia), prickly pear (Opuntia), cane cholla (Opuntia imbricata), agarito (Berberis trifoliolata), and a variety of grasses. In the lowlands, P. pectoralis is common only in rocky arroyos and boulder-strewn draws that originate in the mountains and cross the desert scrubland, arid grasslands, and juniperdominated plains. In southeastern New Mexico, I have observed large areas of rocky habitat similar to those where P. pectoralis previously has been reported (Findley et al., 1975; Geluso and Geluso, 2004), but these areas lie outside the present range of P. pectoralis in Otero, Eddy, and Chaves counties. In fact, Findley et al. (1975) reported no Peromyscus from southeastern Otero County, northwestern Eddy County, southwestern Chaves County, or southeastern Lincoln County. Because I suspected that P. pectoralis might inhabit areas north and west of its 284 vol. 49, no. 2 The Southwestern Naturalist FIG. 1 Distribution of the white-ankled mouse (Peromyscus pectoralis) in New Mexico. Shaded areas refer to limits of mountain ranges, including their foothills. Open circles represent new locality records reported in this study and closed circles represent those published in Findley et al. (1975) and Geluso and Geluso (2004). The northernmost closed circle represents specimens collected at McKittrick Hill, the previous northernmost record in the state (Findley et al., 1975). reported range, I conducted surveys in rocky habitats of 6 counties in southeastern New Mexico. In this study, I report 15 new localities for P. pectoralis in New Mexico and discuss factors that limit the distribution of this species in the state. In 2001, I trapped a total of 13 nights (1,418 trap nights) in Eddy, Otero, Chaves, Lincoln, Guadalupe, and De Baca counties in New Mexico, using Sherman live traps, and, on occasion, Museum Specials and Victor rat traps. Most traps were set on rock outcrops and ledges associated with arroyos, draws, and canyons. I deposited voucher specimens in the United States Geological Survey Biological Survey Collection at the Museum of Southwestern Biology (MSB), University of New Mexico, Albuquerque. Because Geluso and Geluso (2004) discovered that many specimens of P. pectoralis from Carlsbad Caverns National Park previously had been identified as P. boylii, I examined all specimens of Peromyscus at MSB from southeastern New Mexico for other misidentified P. pectoralis. In addition, I examined several specimens of P. boylii and P. eremicus from Lincoln and Eddy counties that were reported by Findley et al. (1975) but housed in the Museum of Vertebrate Zoology, University of California, Berkeley (P. boylii MVZ 76887 and P. eremicus—MVZ 51566 and 76886) and in the National Museum of Natural History, Washington, D. C. (P. boylii USNM 110371, 116052, 119223, and 119224 and P. eremicus USNM 109200, 109202, 109203, 110368, and 110370). Although, specimens of P. pectoralis commonly have been misidentified in the past (Geluso and Geluso, 2004), these mice are relatively