MAMMALS OF THE ~IULESHOE SANDHILLS IN BAILEY, HALE AND LAMB COUNTIES, TEXAS by RUSSELL JOSEPH PESATURO, B.A. A THESIS IN ZOOLOGY Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Approved Accepted December, 1989 ACKNOWLEDGEMENTS I am indebted to Dr. J. Knox Jones, Jr., for his assistance and advice throughout this study. I am also grateful to Dr. Clyde Jones and Dr. Kent Rylander for their aid and willingness to serve as members of my committee. For assistance in the field and laboratory, I would especially like to thank Richard Manning. I wish to thank Robert Owen, Larry Choate, Janie Milner, Beth Henry, and the rest of the NSRL personnel for help during various stages of this project. I am grateful to The Museum of Texas Tech University for logistical support, Dean Clyde Hendrick of the Graduate School for some support for the cost of field work, the Texas Parks and Wildlife Department for issuing scientific collecting permits, and the ranchers and farmers who gave me permission to trap on their property. Finally, my deepest appreciation goes to my wife Milva, for accompanying me on most field trips and for support and encouragement throughout the study. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................. ii LIST OF TABLES ................................................... iv LIST OF FIGURES .................................................. v CHAPTER I. INTRODUCTION 1 II. METHODS AND MATERIALS 3 III. DESCRIPTION OF AREA 6 Geography 6 Geology 6 Soil 11 Climate 16 History and Usage . 19 Vegetation . • . 21 IV. ACCOUNTS OF SPECIES 35 Species of Possible Occurrence .................... 63 V. DISCUSSION 66 LITERATURE CITED 69 iii LIST OF TABLES 1. Climatological summary of the Muleshoe Sandhills 18 2. Cranial measurements of adults of two species of Perognathus from the Muleshoe Sandhills . ... .... .. .... ... ............ ... .. 46 3. Cranial measurements of adults of two species of Reithrodontomvs from the Muleshoe Sandhills, and comparative measurements of specimens from the Trans-Canadian Panhandle of Texas (after Jones et al., 1988) .......................... 53 4. Cranial measurements of adult Peromyscus maniculatus from the Muleshoe Sandhills compared with a sample of adults from the Trans-Canadian Panhandle of Texas (after Jones et al., 1988) . 57 iv LIST OF FIGURES 1. Map of the Muleshoe Sandhills 7 2. Evolution of the physiography of northwest Texas and southeastern New Mexico ...•. .. ..... ... .. ..................... 10 3. General soil associations for Bailey, Lamb, and Hale counties, Texas • . • . 12 4. Sand dunes on the Texas-New Mexico state border, Bailey County 14 5. Sand dune undergoing fixation, western Bailey County......... 15 6. Plant species found in the Muleshoe Sandhills 23 7. Species composition percentages for selected rodent species from the Muleshoe Sandhills ....... ........................... 25 8. Hackberry-shrub series south of Olton, Lamb County........... 27 9. Harvard shin oak-mixed grass series, western Bailey County ... 28 10. Mixed grass-yucca series north of Fieldton, Lamb County 29 11. Sand sage-midgrass series southwest of Muleshoe, Bailey County 30 12. Sand sage-ragweed-yucca disclimax association north of Sudan, Lamb County . 31 13. Tallgrass-ragweed-Russian thistle disclimax association west of Hale Center, Hale County ....... ...................•....... 33 14. Sand sage-shin oak community west of Muleshoe, Bailey County . 34 15. Checklist of mammals of the Muleshoe Sandhills 36 16. Prairie dog town west of Muleshoe, Bailey County............. 41 v CHAPTER I INTRODUCTION A distinct band of concentrated sandy soils, with varying vegetative cover, stretches from western Roosevelt County, New Mexico, to western Hale County, Texas. We refer to this unique physiographic feature as the Muleshoe Sandhills because Muleshoe, Texas, is the only sizeable town in, or in close proximity to, this landform. Our study was concerned primarily with that part of the Muleshoe Sandhills found in Texas, which comprises approximately 60 percent of the entire belt, located in Bailey, Lamb, and Hale counties. The objectives were to document the distribution and natural history of mammals in this region, and, insofar as possible, to correlate such data with existing environmental parameters, such as plant communities and soil types. No previous study has dealt specifically with the Muleshoe Sandhills from a mammalogical perspective, although several studies of broader content have encompassed them (see, for example, Bailey, 1905; Davis, 1974; Jones et al., 1987; Jones et al., 1988). Publications detailing the distribution of particular mammalian taxa on the Llano Estacado include those of Blair (1954), Desha (1967), Judd (1970), Schmidly (1971,1984), Baumgardner and Schmidly (1981), Hollander et al. (1987), and Manning et al. (1988), among others. In addition, we have consulted all such publications and also general references of the vegetation and physical environment of the region, including Sellards and Baker (1934), 1 2 Tanner (1939), Tharp (1939,1952), Blair (1950), Webb (1950), Allred and Mitchell (1955), Gould (1978), Sullivan (1980), Brown (1982), McMahan ~ al. (1984), and the county soil surveys published by the U. S. Department of Agriculture Soil Conservation Service. CHAPTER II METHODS AND MATERIALS This study began in the late autumn of 1987, with actual field work beginning in January of 1988. We made more than 35 field trips to the study site. We trapped and observed mammals in all three counties in every season and both by night and by day. Field studies were terminated in early August 1989. Mammals were collected by various means. Approximately 2600 trap nights were carried out, including use of Sherman live traps, Victor rat traps, Museum Special snap traps, McAbee gopher traps, and commercial steel traps. Specimens also were caught by hand, found dead along roadways, a few were shot, and some crania were obtained by examination of owl pellets (Pesaturo et al., 1989). Eight pitfall traps were set out 4 mi. N and 5.5 mi. W Cotton Center, Hale County on 19 January, 1989. These traps were periodically checked, but no mammals were captured in them. Observations by us and recorded sightings by local landowners, farmers, and ranchers were noted as well. Specimens housed in The Museum of Texas Tech University that were collected by others prior to 1988 were incorporated into our data base, resulting in a total of more than 800 specimens examined. In addition, a study of the New Mexican Llano Estacada (Aday and Gennaro, 1973) provided records of mammals occurring in the Muleshoe Sandhills from Roosevelt County, New Mexico, which was especially helpful in accounting 3 4 for those species of which we had few or no records. All specimens collected in our survey, approximately 600, also were deposited in The Museum at Texas Tech University. Most of these were prepared as standard museum study skins accompanied by skulls. A few were preserved in fluid or as skeletal parts only. Natural history data recorded in the field or laboratory included morphometric measurements, age and seasonal variation in pelage, molt patterns, and reproductive information such as testicular size in males and condition of females (number and size of fetuses, lactation, and the like). When appropriate, standard cranial measurements were recorded. Most were taken using Fowler Ultra-Cal II digital calipers (to the nearest 0.01 millimeter). Some measurements, however (breadth of interparietal bone and length of upper and lower aveolar toothrows in Perognathus, for example), were taken using a compound dissecting microscope fitted with an ocular micrometer (calibrated to 0.1 millimeter). In addition, cranial measurements of three species (Reithrodontomys montanus, R. megalotis, and Peromyscus maniculatus) were compared to specimens from the Trans-Canadian Panhandle of Texas. Dominant plant species were noted at collecting sites, and vegetative communities were categorized. The occurrence of plants was analyzed for ecological correlation with the distribution and relative abundance of selected mammalian species. Geographic localities were identified by use of a United States Geological Survey topographic map, 1:250,000 (Clovis sheet), as well as county maps distributed by the State of Texas Highway Department. United States Department of Agriculture aerial maps 5 aided in delineating the boundaries of the Muleshoe Sandhills and differentiating local soil types found therein. CHAPTER III DESCRIPTION OF AREA Geography The Muleshoe Sandhills are located in the southwestern part of the Panhandle of Texas, on the Staked Plains or Llano Estacado. The area is characterized by small, gently rolling hills and dunes, many of which are covered with wild grasses, shrubs, and yucca. The sandhills are noticeably set apart from other areas of Bailey, Lamb, and Hale counties, the topography of which is nearly flat and under heavy cultivation. They extend from the west in an east-southeasterly direction. Elevation ranges from about 3900 feet above sea level on the New Mexico border to 3500 feet in Hale County. In size, the Muleshoe Sandhills constitute one of the largest contiguous concentrations of sandy-soil habitat found on the Llano. From western Roosevelt County, New Mexico, to Hale County, Texas, they extend approximately 105 miles. In Texas, they measure some 58 miles from west to east, and from north to south