ILLINOIS BIOLOGICAL MONOGRAPHS ILLINOIS BIOLOGICAL MONOGRAPHS Volumes 1 through 24 contained four issues each and were available through subscription. Beginning with number 25 (issued in 1957), each publication is numbered consecutively. No subscriptions are available, but standing orders are accepted for forthcoming numbers. The title listed below is still in print. It may be purchased from the University of Illinois Press, Urbana, Illinois 61801. Out-of-print titles in the Illi- nois Biological Monographs are available from University Microfilms, Inc., 300 North Zeeb Road, Ann Arbor, Michigan 48106. Kocu, STEPHEN D, (1974): The Eragrostis-pectinacea-pilosa Complex in North and Central America (Gramineae: Eragrostoideae). 14 figs. 8 plates. No. 48. $5.95. Kangaroo Rats: Intraspecific Variation in Dipodomys spectabilis Merriam and Dipodomys deserti Stephens Kangaroo Rats: Intraspecific Variation in Dipodomys spectabilis Merriam and Dipodomys deserti Stephens IYAD A. NADER ILLINOIS BIOLOGICAL MONOGRAPHS 49 UNIVERSITY OF ILLINOIS PRESS Urbana Chicago London Board of Editors: ZANE CAROTHERS, GEOKGE GODFREY, DONALD F. HoFFMEISTER, TOM PHILLIPS, AND PETER PRICE. This monograph is a contribution from the Department of Ecology, Ethology, and Evolution, and the Museum of Natural History, University of Illinois, and the College of Education at Abha, University of Riyadh, Saudi Arabia. ©1978 by The Board of Trustees of the University of Ilinois. Manufactured in the United States of America. Nader, Iyad A. 1934— Kangaroo rats. (Illinois biological monographs; 49) Bibliography: p. Includes index. 1. Dipodomys spectabilis. 2. Desert kangaroo rat. 3. Zoology—Variation. I. Title. II. Series QL737.R66N33 599’ 3233 78-9317 ISBN O-252-00658-5 pbk. Contents ACKNOWLEDGMENTS INTRODUCTION MATERIALS AND METHODS DIPODOMYS SPECTABILIS Species Characteristics Reproduction Color Age Variation Dentition Individual Variation Secondary Sexual Dimorphism Geographical Variation SUBSPECIES OF DIPODOMYS SPECTABILIS Dipodomys spectabilis spectabilis Merriam Dipodomys spectabilis perblandus Goldman Dipodomys spectabilis intermedius Nader Dipodomys spectabilis bailey: Goldman Dipodomys spectabilis zygomaticus Goldman Dipodomys spectabilis cratodon Merriam Dipodomys spectabilis nelsoni Merriam DIPODOMYS DESERTI Species Characteristics Reproduction Color Age Variation Dentition Individual Variation Secondary Sexual Dimorphism Geographical Variation Xi 29 40 68 SUBSPECIES OF DIPODOMYS DESERTI 81 Dipodomys deserti deserti Stephens 81 Dipodomys deserti aquilus Nader 9] Dipodomys deserti arizonae Huey 93 Dipodomys deserti sonoriensis Goldman 96 PHYLOGENY OF THE SPECIES D. SPEC TAB/LIS AND D. DESERTI 99 SUMMARY 107 LITERATURE CITED 109 INDEX 115 Figures Fig. 1. Dipodomys spectabilis perblandus: skull measurements. 4 Fig. 2. Distributional range of the subspecies of Dipodomys specta- bilis. 10 Fig. 3. Reproductive activity in the northern and southern popu-. lations of D. spectabilis. 13 Fig. 4. Molariform teeth; different age groups of D. spectabilis in Arizona. 17 Fig. 5. Occurrences and geographic range, subspecies of D. specta- bilts in U.S. 26 Fig. 6. Occurrences and geographic range, subspecies of D. specta- bilis in Mexico. a | Fig. 7. Scatter diagram comparing morphological features, D. S. batleyt and D. s. “clarencet.” 44 Fig. 8. Equation of discriminant function line separating popula- tions of D. s. zygomaticus and D, s. spectabilis. aI Fig. 9. Linear overlap between measurements of D. s. zygomaticus and D. s. nelsoni; zone of intergradation. 59 Fig. 10. D. deserti deserti skull: dorsal and ventral views. 66 Fig. 11. Beaver Dam Wash. Typical habitat of D. d. deserti. 67 Fig. 12. Reproductive activity in D. deserti. 70 Fig. 13. Molariform teeth, different age groups of D. deserti. ff Fig. 14. Occurrences and geographic range, subspecies of D. de- sertt. 82 Fig. 15. Dipodomys deserti arizonae. 93 Tables Table Table Table Table Table Table Table Table Table Table Table Table Table ‘Table Soa a Molting individuals of D. spectabilis. 12 Reproductive activity in females of D. spectabilis. 12 “Young adult” and “old adult” age groups of D. specta- bilts. 19 Coefficients of variation in two grouped Arizona localities of D. spectabilis. 21 Comparison between adult males and females from two grouped Arizona localities of D. spectabilis. 24-25 Measurements of adult specimens of subspecies of D. spec- tabilis. 62-63 Number of molting individuals of D. deserti. 68 Distribution of recorded reproductive activity in D. de- Serit. 69 Coefficients of variation within a grouped Arizona local- ity of D. deserti. 76 Comparisons between adult male and female D. deserti in Arizona. 78-79 Measurements of adult specimens, subspecies of D. de- serti. 84 Indices of specialization in D. spectabilis. 104 Indices of specialization in D. desert. 104 Indices of specialization in four species of Dipodomys. 105 Digitized by the Internet Archive in 2011 with funding from University of Illinois Urbana-Champaign http://www.archive.org/details/kangarooratsintr49nade ABST RACT Twenty morphological characters in addition to color were studied throughout the geographic range of two species of kangaroo rats, the banner-tailed kangaroo rat Dipodomys spectabilis and the desert kan- garoo rat Dipodomys deserti. A total of 2,725 specimens from 689 local- ities was examined in this study: 1,187 specimens from 368 localities for D. spectabilis and 1,538 specimens from 321 localities for D. desertt. The two species are characterized and notes are given concerning their habitat, longevity, predators, parasites, molt, and reproductive activity. There seems to be one adult molt per year in each of the two species. This takes place during every month, but mostly in August for D. spectabilis and in July for D. desert. Color of the pelage is more stable in D. spectabilis and is less influenced by environmental factors than in D. desertt. None of the characters studied shows significant secondary sexual di- morphism in D. spectabilis, whereas nine characters show significant dimorphism in D. deserti. The level of differentiation among the sub- species of D. spectabilis is higher than that of D. deserti. This difter- ence is thought to be the result of a longer period of isolation of some of the populations of D. spectabilis and of the availability of more varied habitat within the range of this species. The low degree of variability throughout the range of D. deserti is probably due to the uniformity of the habitat, the absence of effective geographic barriers, and to the species’ narrow limits of tolerance. Some of the measure- ments of D. deserti show southward clinal changes. Nasal length and rostral depth increase in size in this direction, and this is thought to be directly correlated with an increase in temperature and a decrease in humidity of the environment. Seven subspecies of D. spectabilis and four subspecies of D. deserti are recognized and are formally diagnosed. D. nelsoni, which was for- merly regarded as a full species, is regarded herein as a subspecies of D. spectabilis. D. s. clarencet is regarded as consubspecific with D. s. baileyi. A brief review of the fossil history of the genus Dipodomys is given. It is assumed that D. spectabilis originated in the northern part of the Central Plateau of Mexico and D. deserti in southeastern California. A pattern of dispersal for each of these two species is proposed. Four indices of specialization (bullar, cranial, pedal, and _ total) were calculated for each subspecies of the two species. Within D. spec- tabilis, the most specialized subspecies is D. s. nelsoni, and within D. deserti, the most specialized is D. d. deserti. Also the data from the indices have led to the conclusion that D. desert: is more specialized than D. spectabilis in all the indices calculated, and that it is phyloge- netically far removed from it. Also, it is concluded that D. deserti is the most specialized species of the genus Dipodomys and _ therefore should be retained in a separate desert: Group. Acknowledgments Many individuals have helped in different ways throughout this study. I am greatly indebted to Professor Donald F. Hoffmeister, Director of the Museum of Natural History, University of Illinois, for his help, advice, and valuable suggestions throughout the course of this study. Without his experience and personal guidance this project would not have been possible. I am greatly indebted to M. Raymond Lee of the University of Hlinois, Henry W. Setzer of the United States National Museum, W. Z. Lidicker, Jr., of the University of California, and J. Knox Jones, Jr., then of the University of Kansas, Museum of Natural History, for their valuable suggestions and criticisms. I also would like to thank Woodrow W. Goodpaster for the use of some of his field notes and for the photograph of D. d. arizonae. Numerous individuals helped by lending specimens, and others per- mitted me to study specimens in the collections under their care. I am grateful to S. Anderson and R. G. VanGelder (AMNH,;; see pp. 7-8 for abbreviations of museums) ; R. R. Clothier (ASU) ; R. ‘T. Orr (CAS) ; A. L. Rand (FMNH); E. R. Hall and J. K. Jones, Jr. (KU); C. Mc- Laughlin and K. E. Stager (LACM); R. H. Baker (MSU); S. B. Ben- son, W. Z. Lidicker, Jr.. and A. H. Miller (MVZ); R. C. Banks (SDSNH) ; W. B. Davis and D. C. Carter (TC@WCO) ; G. A. Barthol- omew, Jr. (UCLA); D. F. Hoffmeister (UI) ; W. H. Burt (UM); J. S. Findley (UNM); D. H. Johnson and R. H. Manville (USNM) ; W. H. Behle and S. D. Durrant (UU). I also acknowledge my indebtedness to my wife, Anita, for her encouragement and patience throughout this study and for typing the manuscript. INTRODUCTION For a better understanding of the evolutionary processes that have occurred and are occurring in a species, the infraspecific units should be identified and the relationships among them analyzed. ‘To achieve these aims, the variation of significant characters throughout the en- tire geographic range of the species must be studied and correlated to analyze the whole. Variation within two species of kangaroo rats, Dipodomys spectabilis and Dipodomys deserti, has been so analyzed and life-history data added. Dipodomys spectabilis was described by C. H. Merriam in 1890 from specimens obtained at Dos Cabezas, Cochise County, Arizona, and Dipodomys deserti by F. Stephens in 1887 from specimens from the Mojave River, San Bernardino County, California. Since the original descriptions, no further study of geographic variation throughout the entire range has been conducted in either species. Although they approach each other geographically in south central Arizona, the species are allopatric. Both have been collected near Florence, Pinal County, and also within Organ Pipe Cactus National Monument, Pima County. Dipodomys, the only living genus of the subfamily Dipodomyinae, is one of three subfamilies of the family Heteromyidae. Grinnell’s (1922) study of the kangaroo rats of California was the closest attempt to a revision of the genus Dipodomys. Since then, Hall and Dale (1939) revised D. microps; Setzer (1949) D. ordi; Lidicker (1960) D. merriami, and Alvarez (1960) wrote a synopsis of the Mexican species of Dipodomys. The present paper is a revision of data pertain- ing to the banner-tailed kangaroo rat Dipodomys spectabilis and the desert kangaroo rat Dipodomys desertt. The phylogenetic relationship between D. spectabilis and D. deserti has been discussed by a number of authors using a variety of evidences (Grinnell, 1922; Setzer, 1949; Burt, 1960; Lidicker, 1960; Stock, 1974) . Some of the authors showed the close relationship between the two no KANGAROO RATS species and placed them in one phylogenetic group, while other inves- tigators placed them in two separate groups. Nevertheless, most of these authors agreed that D. desert: is the most specialized species in the genus Dipodomys. The present study discusses the relationship between the two species and arrives at similar conclusions. MATERIALS AND METHODS This study is based on the examination of 1,187 specimens of Dipod- omys spectabilis from 368 localities and of 1,538 specimens of Dipod- omys deserti from 321 localities for a total of 2,725 specimens from 689 localities. Notes were taken on the color of the pelage for all speci- mens. For both species comparisons of color were made with the type- specimen, topotypes, or other specimens previously compared with topotypes. The notes include information on the color of the dorsum, arietiform markings, plantar stripes, dorsal and ventral tail stripes, and the subterminal band of the tail. Capitalized color terms are from Ridgway (1912). To determine the color, a masked area of pure color on the side just above the lateral line was compared with a certain color on Ridgway’s plates in daylight always from the same angle. All information available on the specimen label was utilized. Body length was calculated as the difference between the total length and tail length. Length of the white tip of the tail was measured to the nearest millimeter, from the base of the proximal part of the white tail tip to the approximated tip of the tail vertebrae in the study specimen. For all the specimens the following 14 measurements of the skull were taken with the same pair of dial calipers (Helios), measuring to 0.1 mm and read to the nearest 0.1 mm (Fig. 1) : Greatest length. From the anteriormost tip of the nasals to the pos- teriormost projection of the auditory bullae. Length of nasals. Maximum length of the longest nasal bone. Breadth of rostrum. Width near the anterior tip of the rostrum, across the premaxillae and nasals at the anterior face of the upper incisors. Breadth across maxillary arches. Greatest breadth across the arches in a plane perpendicular to the long axis of the skull. Least interorbital breadth. Least width between the orbits imme- diately posterior to the lacrimal bones. Greatest breadth across bullae. From the most lateral projection of h lateral i dorsal m Cc Cc d’ e’ f’ 4 a, a’ greatest skull length h, h’ depth of rostrum a length of nasals i, i’ bullar depth c, C’ width of rostrum j, J’ basal length d, d’ breadth across maxillary arches __k, k’ alveolar length of maxillary e, e’ least interorbital breadth toothrow f, f’ greatest breadth across bullae |, I’ breadth across exoccipitals g, g’ least width of supraoccipital m,m’ mandibular length Fig. 1. Dipodomys spectabilis perblandus, UI No. 148086, 7 mi NW Nogales, Santa Cruz County, Arizona. Dorsal, ventral, and lateral views showing skull measurements used in this study. MATERIALS AND METHODS 5 the auditory bullae on one side to the corresponding position on the other bulla. Least supraoccipital breadth. Width at narrowest part. Depth of rostrum. Depth of the premaxillae and the nasals taken immediately posterior to the upper incisors. Bullar depth. Greatest depth measured at a right angle to the long axis from across the dorsal surface of the skull to the most ventral sur- face of the bullae. Basal length. From the anterior border of the alveolar ridge anterior to the upper incisors to the anterior border of the foramen magnum, ventrally. Alveolar length of maxillary toothrow. Greatest distance from the anterior edge of the alveolus of PM4 to the posterior edge of the alveolus of M3. Breadth across exoccipitals. Greatest distance from the lateral edge of the exoccipital on one side to the corresponding edge on the other side. Alveolar length of mandibular toothrow. From the anterior edge of the alveolus of pm4 to the posterior edge of the alveolus of m3. Mandibular length (Condyloid). Distance between the anterior lower lip of the incisive alveolus and the posteriormost border of the condyloid process. Little use was made of ear measurement, as it was not available for a large number of the specimens examined, and measurements of dry ears proved to be unsatisfactory. The least supraoccipital breadth and the length of the white tip of the tail were not utilized for D. deserti because these dimensions proved to be highly variable. The coefficients of variation for 16 males and 13 females from the vicinity of Yuma, Yuma County, Arizona, for the least supraoccipital breadth were 124.92 and 83.15, respectively. The coefficients of variation for 18 males and 13 females from the same locality for the length of the white tip of the tail were 48.34 and 30.12, respectively. In analyzing differences among age groups and in analyzing the sec- ondary sexual dimorphism, standard deviation and standard error of the mean were calculated for each measurement. Comparisons of the means were made following the method outlined by Mayr, Linsley, and Usinger (1953:142) . The age of each specimen was determined. Five age-groups are rec- ognized in D. spectabilis: juvenile, immature, subadult, young adult, and old adult. Since no significant differences were found between the 6 KANGAROO RATS young adult and the old adult age-groups, they were subsequently combined and called adults (see Age Variation, p- 16). In D. desert: only four age-groups were recognized: juvenile, immature, subadult, and adult. Only adults were used for taxonomic and statistical pur- poses. Adult males and females were compared, and the differences be- tween the means in D. spectabilis were not statistically significant (see Secondary Sexual Dimorphism under D. spectabilis, p. 22). Thus, data for the two sexes were combined when the measurements were plotted on the working maps. The differences between the means in D. deserti were statistically significant in some measurements (see Secondary Sexual Dimorphism under D. deserti, p. 77) and, accordingly, these measurements were plotted separately on the working maps. Some localities close to each other were grouped in order to obtain larger samples; nevertheless, distance and physiographic features were taken into consideration. T-tests were made for certain localities and scatter diagrams were often used in comparing different populations. Indices used to determine the degree of specialization of each sub- species of D. spectabilis and D. deserti and of each species as a whole were the following (after Lidicker, 1960:129) : Bullar Index: greatest breadth across the bullae/breadth across the maxillary arches. Cranial Index: greatest breadth across the bullae/greatest length of the skull. Pedal Index: length of hind foot/body length. Index of ‘Total Specialization: An average of the three indices com- bined (bullar, cranial, and pedal) x 100. The average for each character at each locality, or group of locali- ties, was plotted on a map on tracing paper, and lines were drawn whenever an appreciable break or shift in the character was noticed. All maps were combined in order to determine the subspecific boun- daries where the largest number of lines fell together. In the account of subspecies, the synonomy consists of all the names which have been used for the subspecies recognized in this study. Per- tinent information about the type-specimen of each recognized sub- species is included within the account of that subspecies under Type. Name combinations recorded in literature for the first time are also included in the synonomy. Under Specimens examined, states are listed in order of occurrence from north to south and from west to east. Counties in each state and localities within the counties follow the MATERIALS AND METHODS 7 same arrangement. Additional records include specimens known but not examined by me. The following abbreviations are used throughout this report in re- ferring to the different collections. AMNH ASU CAS CM DGC FMNH KU LACM LSU MSU MVZ NMSUWC SDSNH SRSC TCWC TMM UA UCLA UI UM UNM American Museum of Natural History, New York, New York Arizona State University, Tempe, Arizona California Academy of Science, San Francisco, California Carnegie Museum, Pittsburg, Pennsylvania Direccién General de Caza de la Secretaria de Agricultura y Ganaderia, México Field Museum of Natural History, Chicago, Illinois Museum of Natural History, University of Kansas, Law- rence, Kansas Los Angeles County Museum, Los Angeles, California, in- cluding the Allan Hancock Collection Louisiana State University, Museum of Zoology, Baton Rouge, Louisiana The Museum, Michigan State University, East Lansing, Michigan Museum of Vertebrate Zoology, University of California, Berkeley, California New Mexico State University, Wildlife Collection, Univer- sity Park, New Mexico San Diego Society of Natural History, San Diego, California Sul Ross State College, Alpine, Texas Texas A&M University, Cooperative Wildlife Collection, College Station, Texas Texas Memorial Museum, Natural History Collection, Aus- tin, Texas Department of Zoology, University of Arizona, ‘Tucson, Arizona University of California at Los Angeles, Los Angeles, Cali- fornia, including the Donald R. Dickey Collection Museum of Natural History, University of Hlinois, Urbana, Illinois Museum of Zoology, University of Michigan, Ann Arbor, Michigan University of New Mexico, Collection of Vertebrates, Albu- querque, New Mexico KANGAROO RATS USNM United States National Museum and _ Biological Surveys Collection, Washington, D.C. UU Museum of Zoology, University of Utah, Salt Lake City, Utah DIPODOMYS SPECTABILIS Species Characteristics The banner-tailed kangaroo rat, with an adult weight range from 77.0 to 171.2 grams, is one of the largest species of the genus Dipodomys. It has four toes on the hind foot. The hind legs and feet are larger and much longer than the fore legs, an adaptation for saltatorial locomo- tion. The tail is long, covered with short hairs on the proximal halt and with long hairs on the distal half. The color of the dorsum, in general, is Light Ochraceous-Buff, mixed with a variable growth of black-tipped hairs, purest on the sides and lightest on the cheeks. The supraorbital and postauricular spots, hip stripes, fore limbs, dorsal sur- face and sides of hind feet, lateral tail stripes, ventral surface, and the distal end of the tail are pure white. The Ochraceous hip patch ex- tends down the leg behind the ankle to form a large dark spot that reaches the heel and leaves a white spot anteriorly. The white ring at the base of the tail is incomplete, with gray to black colored hairs ven- trally. The dorsal and ventral tail stripes, which are grayish black to dusky, unite to form a continuous black or almost black band around the tail subterminally. The white lateral tail stripes narrow gradually beyond the proximal half of the tail and disappear at the subterminal band. The skull is large, with inflated bullae. The interparietal bone is variable in size and shape and sometimes fused with the supraoccipital. The maxillary arches are heavy and their posterolateral edges are slightly slanted or flared out. The dorsal anteromedial edge of the maxillary arch is narrow and extends slightly along the premaxilla. The teeth are medium to massive in size and the molariform teeth are of the opaeodont type (Nader, 1966). The upper incisors are grooved anteriorly. A depression, here called the “ectoglenoid fossa,” for the attachment of the ventral slip of the temporal muscle is present between the glenoid fossa and the posterior end of the zygomatic arch. perblandus intermedius spectabilis baileyi zygomaticus . cratodon nelsoni D D D D D D D Fig. 2. Distributional range of the subspecies of Dipodomys spectabilis. Dipodomys spectabilis 11 The external opening of the auditory meatus varies from round to oval in shape. The hyoid apparatus is composed of only two parts, basihyal and a reduced thyrohyal, and is characterized as follows: the basihyal is medium-sized with a prominent ventral ridge. The anteromedial bor- der of the “shoulders” is somewhat round. The basihyal arch is not so deep as in D. deserti. The thyrohyal is medium in size. D. spectabilis primarily inhabits the upper edges of the Lower So- noran Life-zone, but occasionally is found also in the Upper Sonoran Life-zone (Fig. 2). It prefers open sites with vegetation consisting of mixed grasses and desert shrubs such as mesquite, Prosopis sp., and creosote bush, Larrea sp. Other kangaroo rats that range sympatrically with and share almost the entire range of D. spectabilis are D. merriami and D. ordii. Because it is larger in size, darker in coloration, and has the white tip on the tail, D. spectabilis can be differentiated easily from the other species. Little is known about the longevity of D. spectabilis. Bailey (1931: 254) reported that a captive pair lived several years. A male (USNM No. 246652) kept in captivity for almost three years died presumably of old age. Several species of carnivores, owls, and snakes prey on D. spectabilis. The badger, Taxidea taxus, and the kit fox, Vulpes macrotis, are the most important predators. Others cited by Vorhies and ‘Taylor (1922:35) are the bobcat, Lynx rufus baileyi, the coyote, Canis latrans, skunks, Mephitis sp., the western horned owl, Bubo virginianus, and the barn owl, Tyto alba. Rattlesnakes, Crotalus sp., gopher snakes. Pituophis sp., and racers, Masticophis flagellum, may also be among D. spectabilis predators. Despite all these natural enemies, the number of kangaroo rats taken must be relatively small; the abundance of the species seems little affected, since the reproductive rate is compara- tively low (see Reproduction, p. 12). D. spectabilis is known to be the host for at least one species of flea, Ctenophthalmus sp., and one species of chigger, Trombicula sp. (Vor- hies and Taylor, 1922). No record of endoparasites was found. Of the 1,187 specimens of D. spectabilis examined in this study, only 114 showed any evidence of molting. Patterns of molting in these speci- mens were recorded. No juvenile molt was observed and only two immatures were molting, one in August and the other in September (Table 1) . Subadult molt commences late in the spring and ends early in the winter with a peak in August. Adult molt was observed at least once in every month; however, adults seem to molt once a year—mostly 12 KANGAROO RATS TABLE | Number of molting individuals of Dipodomys spectabilis (by age-groups and month of capture) Month of capture Age-Group J F M A M Joy A Ss O ND Immature -— ] ] a — — Subadult 3 2 6 13 7 = 3 — Adult I ] 2 4 7 8 9 25 12 ] 7 1 in August—as only a single peak in molting was observed. New hair first appears on the snout and cheeks, then proceeds posteriorly to the level of the ears; usually an area of unmolted hair is left between the eyes and this disappears later. Then, a saddle-shaped area of new hair appears in the middorsal region. From this area, molt progresses an- teriorly to meet with the molted area in the head region behind the eyes. Later. molt proceeds laterally to the shoulders and sides, and then posteriorly to the rump and hind limbs. REPRODUCTION In 151 female kangaroo rats examined for pregnancy, placental scars, or lactation, only 45 showed these signs of reproduction (29.8%) . Sexual maturity is attained late in the subadult age range (Table 2). Only five of 34 subadult females examined showed signs of reproduc- tive activity (14.7%) . TABLE 2 Distribution of recorded reproductive activity in females of Dipodomys spectabilis by age-groups Sub- Young Immature adult Adult Adult Total Females examined 5 34 4] 71 151 Females showing reproductive activity 0 5 12 28 45 Reproductive activity takes place almost the year around, except perhaps in October and November. This activity evidently starts and terminates about a month earlier in the northern populations, which include D. s. perblandus, D. s. intermedius, and D. s. spectabilis (none Northern Populations, Dipodomys spectabilis 15 A B C fo) 123 n wn ° WwW > 4 in uJ a ra ‘a i 2 Fs) rt WW uw 5 5 So 4 o 4 wi 4 @ «3 = 3 = 3 m2 m 2 4 2 = | =. | 2 = 4 2 JFMAMJJASOND JFMAMJJASOND 1234 A, A’. Number and percentage B, B’. Number of C, C’. Frequency (above each column) of embryos per month distribution of females showing reproductive litter size activity per month Fig. 3. Reproductive activity in the northern and southern populations of Dipodomys spectabilis. 14 KANGAROO RATS examined for D. s. baileyi), than in the southern populations, which include D. s. zygomaticus, D. s. cratodon, and D. s. nelsoni. In the northern populations, breeding activity starts in December and ends late in September (Fig. 3A). No pregnant temale was recorded in De- cember. The earliest recorded pregnancy was on 10 January and the Jatest on 8 September (3 embryos x 10 mm). No record of pregnancy in August is available, although females were examined during this month. In the southern populations, breeding starts late in November and ends in early September (Fig. 3A’). No pregnancy was recorded in November, but a young adult female collected on 1 December was carrying an embryo 10 mm in length. The latest recorded pregnancy in this group was on 26 August (2 embryos x 21 mm). The fact that, in this southern group, no pregnant females were found in January and February, may possibly indicate that too small a sampling of fe- male rats was taken during these months. One female examined on 1] March was lactating. Although no pregnant female of D. s. baileyi was examined in this study, the data presented by Holdenried (1957) for this subspecies fit well within the present findings. The largest number of pregnant females in the northern popula- tions was in April, when 80% were pregnant (Fig. 3A). All females examined in February were pregnant. In the southern group, the months of December, June, and July showed the largest number of pregnant females (Fig. 3A’). The number of embryos counted was largest in April in the northern group, but in December and July in the southern group (Fig. 3; B, B’). Reproductive activity in D. spectabilis is long, extending over a 10- month period and results in two, and possibly three, litters per year, at least in some subspecies (Holdenried, 1957). For my sample, the number of embryos in a litter ranges from 1 to 3 (mean 2.0) in the northern group and from 1 to 4 (mean 1.87) in the southern group (Fig. 3; C. C’) with a mode of 2 for both. Holdenried (1957:342) re- ported that in 12 females of D. s. baileyi with 33 embryos, the litter size ranged from 2 to 4 with an average of 2.75 per litter. Vorhies and ‘Taylor (1922:18) reported that 67 females of D. s. perblandus had 122 embryos or placental scars, having a mean of 1.82 per female and a mode of 2. The differences in the mean of embryos per litter for north- ern populations as given by Holdenried (2.75) and my study (2.0) are probably accidental because of sample size. There is little information concerning growth and development. ‘The largest embryo recorded had a crown-rump length of 60 mm. Dipodomys spectabilis 15 From Bailey’s (1931) observations of a captive female D. s. spectabilis, the gestation period was found to vary between 22 and 27 days. Bailey also noted that the incisors erupted 11 days after birth and weaning took place between 20 and 25 days of age. Young males grow faster, in terms of weight, than young females (Holdenried, 1957:344) . COLOR Variation in color of the pelage of D. spectabilis throughout its range is not great. The color of the upper parts, in general, is Light Ochra- ceous-Buff mixed with variable numbers of black-tipped hairs, depend- ing on the subspecies. The coloring is purest on the sides and lightest on the cheeks. The black-tipped hairs are longer and coarser than the rest of the hairs of the dorsum. Samples from a given locality are quite uniform in color. Also, color of the upper parts within a given sub- species is stable. The upper parts are thinly mixed with long black-tipped hairs in D. s. perblandus, D. s. intermedius, D. s. nelsoni, and D. s. cratodon, whereas the upper parts are heavily mixed with black-tipped hairs in D. s. spectabilis and D. s. zygomaticus, and moderately in D. s. baileyi. The pure color of the upper parts in D. s. intermedius is lightly mixed with Pinkish Buff which is more evident on the sides, while in D. s. baileyi it is occasionally mixed with Pinkish Buff, especially among the populations in western Texas; in D. s. nelsoni it 1s occasionally mixed with grayish hairs. The different subspecies do not exhibit noticeable variation in the whitish area between the arietiform markings and the eye, the supra- orbital and postauricular spots, hip stripe, color of the ventral surface, fore feet, dorsal surfaces and sides of hind feet, the incomplete ring at the base of the tail, and the lateral tail stripes. Color variation is, how- ever, noticeable in the following: the arietiform markings and the an- terior ear fold are dusky in D. s. perblandus, D. s. intermedius, and D. s. nelsoni; blackish in D. s. baileyi; black in D. s. spectabilis and D. s. zygomaticus. D. s. cratodon has dusky arietiform markings and a black anterior ear fold. The large dark spot behind the ankle varies from dusky to black and occasionally is mixed with gray. The plantar stripe varies from light brown to dark brown to black; the lightest is in D. s. intermedius, the darkest in D. s. spectabilis. The ventral sur- face of the toes is usually washed with yellowish or brownish color. The subterminal band of the tail is blackish in perblandus, inter- medius, nelsoni, and cratodon; black in spectabilis, baileyi, and zygo- maticus. Although the length of the white tip of the tail is variable 16 KANGAROO RATS within the subspecies as well as among the different subspecies, it is long in spectabilis and baileyi; short in intermedius and perblandus; shortest in D. s. nelsoni. Age Variation Five age-groups of D. spectabilis are recognized. Although these divi- sions are arbitrary (as no individual of exactly known age was avail- able) , they nevertheless serve to categorize the available material and facilitate comparisons of individuals of similar ages. Juvenile. Deciduous teeth PM4, pm4 are present and show some or considerable wear. M1-2, ml-2 show some wear. M3, m3 are either just erupted or not yet erupted (Fig. 4; a, a’, b, b’). M3 may show slight wear in the older juveniles, but m3 shows no wear in any of the speci- mens examined. The two lophs on the crown of M3 are still evident in old juveniles (Fig. 4; c, c’). The skull, in general, is fragile and the dorsal surface is convex. The auditory bullae are opaque and rough. ‘The color of the pelage is more grayish than ochraceous and the fur is short, especially on the tail. The dorsal and ventral tail stripes are black in their entire length. The tail is not penicillate. Immature. Deciduous PM4, pm4 have just been shed. M3, m3 show some wear in the youngest animals (Fig. 4; d, d’). In old immatures, the permanent PM4 shows some wear, and pm4 shows slight wear. The two lophs of the permanent PM4 are still evident. The molars are ac- quiring an oval shape on the occlusal surface (Fig. 4; e, e’) . The dor- sal surface of the skull is convex and the auditory bullae are still opaque and rough. The color is slightly more ochraceous, and the fur is slightly longer than in the juveniles. The distal part of the dorsal tail stripe is darker than its proximal part. The tail is becoming peni- cillate. Subadult. Permanent dentition is present and all teeth show some wear. All cheek teeth are acquiring a more oval shape, except M3 which usually appears somewhat “‘triangular’ in shape with its apex pointing posteriorly, and pm4 which is almost rectangular in shape (Fig. 4; f, f, g, g’). Enamel breaks—absence of the enamel from either the lingual side or the labial side or both—appear in this age group and are present in all cheek teeth of older subadults. The auditory bullae are still rough, opaque, and porous. The hair is still grayish, but otherwise assuming adult coloration. The youngest subadult (Fig. 4; f, f’) shows a shallow groove in the a-i = right maxillary toothrow a’-i’ = right mandibular toothrow Juvenile Juvenile No. 14076 ¢ = No. 20135 9 \/ Sabino 1V2 mi S, Canyon, Ya miE Baboquivari Arivaca, Mts., Pima Co. Pima Co. Q’ Juvenile Immature No. 17549 2 No. 17548 3 Se Sells, Sells, < YJ Pima Co. Pima Co. = C’ d’ Immature Subadult No. 20132 2 No. 201293 1% mi S, . Ys mi E fen E Arivaca, Sina Ce Pima Co. ime 0: e e’ f Subadult es No. 4395 J No. 17166 2 4miN, Montezuma 1miE Canyon, Sasabe, Cochise Co. Pima Co. g h h Old adult a No. 4380 @ ‘g A\ av i Fig. 4. Occlusal views of molariform teeth of different age groups of Dipod- omys spectabilis in Arizona. All specimens are from UI Collection. 18 KANGAROO RATS anteromedial surface of PM4. This indicates the remains of the enamel infolding that separates the protoloph from the metaloph (see Denti- tion). In pm4 of the same specimen, a labial and a lingual infolding are still present, and in many cases in other specimens a frontal groove also is present. Enamel breaks first develop in M1 and M2, later in PM4, and lastly in M3. The development of enamel breaks in the mandibular teeth follows the same pattern. In the youngest subadults, enamel breaks are absent in PM4, pm4. In older subadults, two en- amel breaks, a lingual and a labial, are present in each tooth. Some pm4s however, may have three or sometimes four enamel breaks (Fig. 4; g, 9” a5 Young Adult. Cheek teeth have an oval shape, except pm4, which has a rectangular or occasionally a “triangular” shape (Fig. 4; h, h’). Enamel breaks are present in all or any one of the cheek teeth. The auditory bullae are shiny and smoother than those of the subadults. The color of the pelage attains its adult condition in this age-group (see Species Characteristics, p. 9). In younger young adults, all cheek teeth have enamel breaks which tend to get narrower in older specimens and disappear in some teeth in the oldest young adults. Enamel breaks disappear first in M2 and M5, then in M1 and PM4. Lower teeth follow the same general pat- tern. Old Adult. All teeth show much wear and pm4 is more “triangular” than rectangular in shape (Fig. 4; i, i’). The enamel breaks in all cheek teeth have disappeared. The auditory bullae are shinier and are usually translucent. To determine whether differences between means of the young adult and the old adult age-groups were significant, localities from 23 to 35 mi S Tucson and 27 to 30 mi SE Tucson, Pima County, Arizona, were grouped, resulting in a series of 42 specimens; 26 males (9 young adults and 17 old adults), and 16 females (8 young adults and 8 old adults) . The means of 19 measurements of two age-groups within each sex were compared. In both sexes, old adults were slightly larger than the young adults in about half of the measurements (Table 3). The differences between the means were not statistically significant and accordingly these two age-groups were combined for further analysis and were called the adult age-group. DENTITION The sequence of tooth eruption in the upper jaw in D. spectabilis is as ‘TABLE 3 Comparisons between “young adult” and “‘old adult” age-groups of Dipodomys spectabilis@ (The order is mean, number of specimens as a superscript, one standard deviation, and one standard error of mean. Measurements are in mm) Character Males Females “Young “Old “Young “Old adults” adults” adults” adults” Total length 332.88 325.511 323.07 325.58 15.13 + 5.36 13.77 + 4.15 | 635 + 240 11.72 + 4.14 Tail length 195.39 187.911 189.47 193.58 11.28 + 3.76 11.29 + 340 | 666 + 2.52 7.39 + 2.61 Hind foot length 50.19 49.916 49.58 49.18 106 + 353 2.15 + .537 15) + 534 181 + .638 Ear length 15.01 15.510 17.01 16.45 — 71 + 225 — 114 + .509 Body length 135.28 135.915 136.08 132.08 841 + 297 7.02 + 181 | 444 + 157 5.93 + 2.10 Greatest skull 44.38 44.716 44,18 44.06 length 78 + 275 1.03 + .257 Ll] + .391 744 ~~ .30 Basal skull 32.39 32.516 32.37 31.86 length 70 + .235 62 + .155 83 + 313 54 + 218 Length of nasals 15.98 16.317 16.15 16.38 46 + = .162 55 + 134 48 + .169 58 + .204 Breadth across 25.89 26.215 25.88 26.18 max. arches 1.29 + 429 60 + 153 63 + .222 110 + .70 Least interor- 15.07 15.316 14.96 15.58 bital breadth 76 +. .288 50 + .126 28 + 113 83 + 292 Greatest breadth 28.88 28.615 28.38 28.26 across bullae 78 + 276 63 + «161 73 + 258 62 + .254 Rostral breadth 4.57 4.617 4.68 4.58 18 + .066 24 + 057 93 + 079 21 + .073 Rostral depth 8.59 8.517 8.58 8.48 35 + 117 27 + .065 18 + .065 22 + .078 Bullar depth 14.98 15.116 14.98 14.97 16+ .055 43 + .107 42 + 149 34 + 128 Alveolar length of 6.09 6.017 5.98 5.88 max. toothrow 24 + 079 30 + 071 $7 + 13 26 + .092 Least breadth of 2.29 2,116 918 2.26 supraoccipital 48 + 158 30 + 073 45 + .159 38 + 156 Breadth across 14.09 13.915 13.86 13.56 exoccipitals 61 + .204 45 + 112 51 + 211 A4 tb 18 Alveolar length of 5.89 5.817 5.78 5.88 mand. toothrow 22+ 071 20 + .048 34. 191 99 + 077 Mandibular 18.99 19.117 18.78 19.08 length 27 + 091 60 + 145 26 + 09 ADO 16 Length of white 24.76 24.38 22.69 25.77 tip of tail 4.84 + 1976 2.31 + .819 | 4.97 + 2.92 4.63 + 1.75 aFrom 23 to 35 mi S Tucson and 27 to 30 mi SE Tucson, Pima Co., Arizona. 20 KANGAROO RATS follows: ‘The deciduous incisors, although not seen in any of the speci- mens examined, are regarded as the first teeth to erupt from the alveo- lar ridge, and are lost very shortly thereafter. Bailey (1931:256) noted in captive animals that at 11 days of age, the permanent incisors first appeared through the gums as hard points or edges. The deciduous PM4 which shows slight wear in the youngest juvenile is assumed to have erupted shortly after the incisors erupted, probably at 13 or 14 days of age. Deciduous PM4s persist for a short period before being lost. MI evidently erupts at the same time as the deciduous PM4 or shortly thereafter, as it exhibits slight but comparable wear. Both deciduous PM4 and M1 show some wear before the eruption of M2. The latter shows some wear before the eruption of M3 which exhibits some wear before the deciduous PM¢4 is lost. The last tooth to erupt is the permanent PM4 which can be seen between the roots of the deciduous PM4 in older juveniles. The sequence of eruption in the lower jaws follows the same general pattern as that of the upper jaws, except that the permanent incisors and m3 are slower in eruption and development. No wear was ob- served in m3 before the loss of the deciduous pm4. The permanent pm4 is slower in development and wears more slowly than the per- manent PM4. . In the youngest juvenile examined, both deciduous PM4 and pm4 are slightly worn and their cusps are not clearly evident. Deciduous PM4 has an anterior cusp, which has already lost its enamel covering, followed by a transverse protoloph near the middle and a metaloph at the posterior end of the tooth (Fig. 4a). Then the protoloph unites with the metaloph at the middle, forming an H pattern, with a deep lingual and a shallow labial enamel infolding (Fig. 4b). Later, the anterior Cusp unites with the protoloph. The deciduous PM4 shows less wear than that of pm4. In pm4 there is also an anterior cusp and two transverse lophids: a protolophid near the middle and a metalo- phid near the posterior end, At this early stage, the anterior cusp has already united with the protolophid at the middle, leaving a deep lingual and a shallow labial enamel enfolding (Fig. 4a’). Later, the metalophid unites with the protolophid at the middle, resulting in an additional labial and lingual enamel infolding (Fig. 4b’) . All permanent teeth have two lophs or lophids. The lophs of PM4 unite at the labial side, leaving a deep lingual enamel infolding (Fig. 4a), while the lophids of pm4 unite at the middle of the tooth, leaving two deep enamel infoldings, a labial and a lingual (Fig. 4f’). The two lophs and lophids of both upper and lower molars unite lingually Dipodomys spectabilis 21 leaving deep labial enamel infoldings. Moreover, only M3 has a shal- low indentation on the lingual side, and all lower molars have a shal- low lingual infolding. Of the specimens examined, several from discrete parts of the range of the species have lower incisors with a shallow-grooved, anterior face, although there was no uniform pattern or subspecific correlation in their presence. They probably represent independent mutations. Individual Variation In a sexually reproducing population, individual variation is expected, but the twenty measurements studied in D. spectabilis show no great variability for either males or females, except for the least supraoccipi- tal breadth and the length of the white tip of the tail. Table 4 shows ‘TABLE 4 Coefficients of variation in two grouped localities of Dipodomys spectabilis from Arizona D. s. perblandus® | D. s. spectabilis® Character 263 4 169 9 192 8 169 9 Total length 4.3819 2.8715 3.02 3.5815 Tail length 6.0820 3.7215 4.18 6.0715 Hind foot length 3.6225 3.3] 3.27 3.24 Ear length 7.8611 6.626 5.32 7.2115 Body length 5.3228 4.64 3.62 5.8114 Greatest skull length 2.1424 2.1214 2.31 2.55 Basal skull length 1.3525 2.2818 2.52 2.65 Length of nasals 3.3225 3.25 3.40 2.62 Breadth across maxillary arches 3.4524 3:39 2.9318 3.20 Least interorbital breadth 3.8828 4.5514 4.6418 4.95 Greatest breadth across bullae 2.3523 2.3314 2.60 2.9315 Rostral breadth 4.8824 4.59 5.62 6.99 Rostral depth 3.46 2.35 3.14 2.66 Bullar depth 3.7024 2.5215 2.15 2.02 Alveolar length of maxillary toothrow 4.5] 5.18 4.65 4.06 Least breadth supraoccipital 14.0225 18.98 16.38 15.43 Breadth across exoccipital 3.5824 3.6512 3.27 3.03 Alveolar length of mandibular toothrow 3.45 4.97 55 4.05 Mandibular length 2.62 1.97 2.63 3.05 Length of white tip of tail 14.1614 19.8014 | 21.42 12.1115 a23 to 35 mi S Tucson and 27 to 30 mi SE Tucson, Pima County. b5 to 20 mi SE Fort Huachuca, Cochise County. 22 KANGAROO RATS the coefhcients of variation for two grouped localities representing two different subspecies. The high degree of variation in the supraoccipital breadth was also noted by Lidicker (1960:140) in his study of Merriam’s kangaroo rat. I agree with Lidicker in attributing this high variability to the de- pendence of the width of the supraoccipital on bullar inflation. This inflation tends to reduce the size of both the supraoccipital and the interparietal from two directions. The interparietal is also highly vari- able and probably tends to be eliminated inasmuch as the presence of more than one interparietal, its fusion with the supraoccipital, or sometimes its absence, are indications of its instability. More than one interparietal may indicate the presence of more than one center of ossification, and the failure of these centers to coalesce produces the multiplicity of bones. Absence of the bone results from one of two factors: either it is not developed originally, which allows the arms of the supraoccipital to fuse together, or the interparietal is fused indis- tinguishably with the supraoccipital, although its place is still evident. The absence of the interparietal is neither a function of aging since it remains distinct in skulls of aged animals, nor it is a function of hy- pertrophy of the bullae, for they rarely are inflated enough to over- crowd the interparietal as in Dipodomys deserti. Ordinarily the inter- parietal is elongated in shape, except in D. s. perblandus in which it is generally diamond-shaped. The great variation in the measured lengths of the white tip of the tail is partly a result of inaccurate measuring. In general, external measurements vary more than cranial measure- ments, especially tail length and ear length, because different collectors use different techniques in making these measurements. Rostral width and alveolar length of the maxillary toothrow are highly variable cranial dimensions. The mean of the alveolar length of the maxillary toothrow was com- pared with that of the mandibular toothrow in both of the above- mentioned grouped localities. For both males and females in the two groups, the maxillary is longer than the mandibular toothrow. In the first group, the difference is significant in males, but not in females. In the second group, the differences are not significant in either sex. Secondary Sexual Dimorphism Males usually are slightly but not significantly larger than females. ‘To analyze secondary sexual dimorphism, two grouped localities were used. Group A was the same one used in the age-group analysis. Group Dipodomys spectabilis 23 B was from 5 to 20 mi SE Fort Huachuca, Cochise County, Arizona. In Group A the means of 13 of the 20 measurements compared were slightly larger in the males than those of the females (Table 5). In Group B, the means of nine measurements were slightly larger in the males (Table 5). However, none of the means of the 20 measurements of the males was significantly different from those of the females in either group. Accordingly, the two sexes were combined for the analy- sis of differences between the means of the different populations. Geographical Variation Morphological variation among the different populations of D. spec- tabilis throughout the range of the species is evident. This variation is caused partly by some habitat differences in the different parts of the range and partly by geographic isolation and the presence of some partially effective barriers. Geographically, the most variable measurements are total length, tail length, greatest skull length, and, to a lesser degree, basal length, nasal length, greatest breadth across the bullae, bullar depth, and mandibular length. Similarly, the least variable measurements are al- veolar length of the maxillary toothrow, least supraoccipital breadth, greatest breadth of the exoccipitals, and alveolar length of the man- dibular toothrow. There is some pattern in the variation throughout the range of the species. D. s. spectabilis, which is almost in the center of the range, is medium in size in almost all the measurements. The western popula- tions, D. s. perblandus and D. s. intermedius, are smaller in most of the characters than D. s. spectabilis. However, D. s. intermedius is gen- erally smaller than D. s. perblandus. The populations of D. s. baileyi in the northeastern part of the range have the largest measurements of most of the characters. Specimens from some localities in western ‘Texas are in some characters similar to those of D. s. spectabilis. Al- though the populations of D. s. zygomaticus in south central Chihua- hua and north central Durango are sufficiently differentiated from D. s. spectabilis to the north, the differences are not great. The small- est and most distinct populations are those in the east-southeastern part of the range, D. s. nelsoni (see also the account of this subspecies p. 56). The disjunct populations of D. s. cratodon in the southeast- ernmost part of the range are distinct and usually larger than D. s. nelsoni. However, in some characters they are similar to those of D. s. spectabilis. No clinal change throughout the range of the species is clear in any 24 TABLE 5 KANGAROO RATS Comparison between adult males and adult females trom two grouped locali- ties of Dipodomys spectabilis from Arizona (Number of individuals, mean, range, one standard deviation. and one standard error of the mean. Measurements in mm) Character Group Aa Group Bb 263 ¢ 1629 19g ¢ 169 Q Total length 328.5319 324.3315 339.58 338.2715 (312.0-350.0) — (312.0-346.0) | (325.0-358.0) — (317.0-361.0) 14.43 9.369 10.319 12.151 +3.311 +2.419 +2.367 +3.138 Tail length 191.2529 191.615 195.74 196.215 (170.0-212.0) (178.0-203.0) | (178.0-207.0) (175.0-212.0) 11.62 7.119 8.217 11.893 +.447 +1.779 +1.886 +3.071 Hind foot length 49,9825 49.31 53.69 53.0 (45.0-55.0) (47.0-52.0) (51.0-56.0) (50.0-56.0) 1.805 1.629 1.766 1.713 +.361 +.407 +.405 + .428 Ear length 15.4511 16.56 16.84 16.7715 (15.0-19.0) (15.0-18.0) (15.0-19.0) (15.0-19.0) 1.217 1.095 899 1.207° +.367 +.447 +.206 +.312 Body length 135.7428 134.0 143.84 140.9314 (120.0-146.0) (124.0-143.0) | (131.0-151.0) — (125.0-155.0) 7.22 6.218 5.23 8.177 +1.507 +1.554 +1.201 +2.186 Greatest skull length 44.5424 44.0214 45.51 45.38 (42.7-47.3) (42.5-45.9) (43.4-47.1) (42.4-46.7) 959 94 1.048 1.152 +.195 +.251 +.241 +.289 Basal skull length 32.4125 32.0318 33.35 33.36 (31.4-33.2) (31.3-33.7) (32.0-35.0) (31.4-34.5) 436 737 .84 887 +.087 +.204 +.193 + .222 Length of nasals 16.1825 16.19 16.51 16.59 (15.5-17.7) (15.2-17.1) (15.6-17.4) (15.7-17.6) 537 525 561 437 +.107 +.131 +.129 +.109 Breadth across 26.0124 25.9316 26.0218 26.02 maxillary arches (23.3-27.4) (24,2-27.3) (24.8-27.3) (24.4-27.0) 901 878 761 833 +.184 +.219 +.18 +.209 Least interorbital 15.2328 15.2514 14,7318 15.27 breadth (14.0-16.2) (14.0-16.5) (13.4-15.9) (14.1-16.4) 593 694 .686 754 +.123 +.185 +.161 +.189 Dipodomys spectabilis 25 Character Group Aa Group Bb 2638 4 169 9 192 ¢ 169 9 Greatest breadth 28.6423 28.2114 29.09 29.3515 across bullae (27.7-29.7) (27.3-29.4) (27.6-30.6) (27.2-30.5) 671 661 755 866 +.14 +.177 +.173 +.224 Rostral breadth 4.5424 4.53 4.51 4.56 (4.1-5.0) (4.2-4.9) (4.0-5.0) (3.9-5.0) 22 .208 254 317 +.045 +.052 +.058 +.08 Rostral depth 8.52 8.43 8.66 8.61 (8.0-9.1) (8.2-8.8) (8.0-8.9) (8.3-9.1) 294 198 274 231 +.057 +.049 + .062 +.058 Bullar depth 15.0524 14.8915 15.37 15.39 (14.4-16.0) (14.2-15.6) (14.9-15.9) (14.6-15.8) 558 378 33 31 +.114 + .097 +.076 +.078 Alveolar length of 6.02 5.81 6.25 6.23 maxillary toothrow (5.4-6.4) (5.5-6.5) (5.7-6.9) (5.8-6.6) 272 302 292 253 +.053 +.075 + .067 + .063 Least breadth 2.1325 2.1714 1.7 1.8 supraoccipital (1.6-2.8) (1.2-2.6) (1.2-2.2) (1.3-2.3) 297 412 277 .278 +.059 +.11 + .064 +.069 Breadth across 13.9124 13.6512 13.96 13.86 exoccipitals (13.2-15.3) (12.8-14.2) (13.0-14.9) (12.9-14.6) 498 497 454 42 +.101 +.143 +.104 +.106 Alveolar length of 5.81 5.74 6.05 6.01 mandibular toothrow (5.5-6.1) (5.3-6.4) (5.7-6.4) (5.6-6.4) .20 285 213 243 +.039 +.071 +.05 +.061 Mandibular length 19.03 18.83 19.94 19.84 (18.3-20.6) (18.3-19.6) (18.7-20.9) (18.7-20.9) 497 371 527 606 +.097 +.092 +.121 +.151 Length of white tip 24.4314 24.512 40.21 40.9315 of tail (18.0-33.0) (15.0-33.0) (20.0-55.0) (33.0-49.0) 3.46 4.85 8.613 4.963 +.893 +1.4 +1.977 +1.281 aD. s. perblandus from 23 to 35 mi S Tucson and 27 to 30 mi SE Tucson, Pima County. bD. s. spectabilis from 5 to 20 mi SE Fort Huachuca, Cochise County. lity loca e- p ty A | | INN ~ WWy \ ie at AF r yf 1 28 KANGAROO RATS of the measurements studied. However in a small part of the range in Arizona and Sonora, there is a southward clinal variation in some of the characters. The northern populations are usually larger. The two smallest populations of the species are found on opposite sides of the Sierra Madre Occidental: D. s. intermedius on the western side and D. s. nelsoni on the eastern side. D. merriami also occurs on both sides, but Lidicker (1960) mentioned no similar situation in D. merriami. The southernmost populations on the western side of the Sierra, D. m. mayensis, are moderately small (Lidicker, 1960:185) . No correlation between nasal length and either rostral depth or rostral width or both was detected in D. spectabilis; in D. deserti, how- ever, a north-south clinal change and a correlation between longer nasals and greater rostral depth were detected, presumably correlated with higher temperature and lower humidity (see Geographical Varia- tion under D. deserti, p. 80) . SUBSPECIES OF DIPODOMYS SPECTABILIS Dipodomys spectabilis spectabilis Merriam Dipodomys spectabilis Merriam, N. Am. Fauna, 4:46, 8 October 1890, original description. [Dipodomys spectabilis| spectabilis: Merriam, Proc. Biol. Soc. Wash- ington, 20:75, 22 July 1907. Type. Male, young adult, skin and skull; No. 17886/24823, U. S. Biological Surveys Collection; from Dos Cabezos [=Dos Cabezas], Co- chise County, Arizona; obtained by Vernon Bailey, 22 November 1889, original number 695. Range. Southeastern Arizona, northeastern Sonora, southwestern New Mexico, northern and central Chihuahua. More specifically, west from the eastern slopes of the Santa Rita Mountains, the vicinity of Fort Crittenden, Santa Cruz County, Ari- zona, and the vicinity of Cananea in northeastern Sonora, east to the western edge of the Rio Grande Valley in New Mexico and Chihua- hua. Does not extend north beyond the valley south of the Gila River; northernmost known record is Fort Grant, Graham County, Arizona. In Chihuahua, not known from the immediate eastern slopes of the Sierra Madre Occidental but extends south and southeast to the west- ern edge of the Rio Conchos. Limits of range are fairly well known except in the northeastern part in New Mexico, its eastern limit west of the Rio Grande in Chihuahua, the eastern side of the Sierra Madre Occidental, and along the western tributary of the Rio Conchos. Diagnosis. Size: Medium; adult total length 338.0 to 350.0 mm; tail length 197.0 to 206.2 mm; body length 141.0 to 146.3 mm; hind foot length 51.0 to 54.0 mm; ear length 16.8 to 18.0 mm; white tip of tail long, 30.0 to 44.0 mm. Color: In general, Light Ochraceous-Buff, heavily mixed with 30 KANGAROO RATS black tipped hairs on dorsum, purest on sides and lightest on cheeks; arietiform markings black; ear fold anteriorly black; large spot behind ankle blackish; plantar stripe dark brown to black, usually becoming light brown or yellowish on ventral side of toes; white band at base of tail interrupted by dusky or black tuft on ventral surface; dorsal and ventral tail stripes dusky; subterminal band of tail black. Skull: Medium-sized; adult greatest length 45.3 to 46.2 mm; basal length 33.0 to 34.1 mm; length of nasals 16.4 to 17.5 mm; maxillary arch heavy, somewhat slanted posteriorly; posterolateral edge of max- illary arch slightly flared out; medial side of lacrimal usually narrower than lateral side; mastoidal bullae large; greatest breadth across bullae 29.0 to 29.7 mm; supraoccipital and interparietal narrow; least supra- occipital breadth 1.5 to 1.9 mm; pterygoid foramen usually oval and directed anterolaterally; incisors and molariform teeth medium in size; alveolar length of maxillary toothrow 6.1 to 6.5 mm; opening of exter- nal auditory meatus generally oval; mandibular length 19.1 to 20.0 mm. Also see Table 6. Comparisons. Compared with Dipodomys spectabilis perblandus, D. s. spectabilis differs in the following: Larger and darker; all exter- nal measurements greater; arietiform markings more distinct; ear fold anteriorly more blackish; large spot behind ankle darker; plantar stripe and ventral surface of toes usually darker; tuft of hairs ventral to white band at base of tail more blackish; dorsal and ventral tail stripes darker; black subterminal band darker; white tip of tail longer; skull larger in size; auditory bullae larger; least supraoccipital breadth narrower; interparietal usually narrower; maxillary arch usually more slanted posteriorly and less angled to the long axis of skull; postero- lateral edge of maxillary arch usually less flared out; lacrimal less uni- form in width; incisors and molariform teeth somewhat larger; ptery- goid foramen usually oval and directed anterolaterally; opening of external auditory meatus usually more oval than round. Compared with Dipodomys spectabilis baileyi, D. s. spectabilis dif- fers in the following: Smaller in total length, tail length, hind foot length, and body length; usually darker in color; arietiform markings darker; skull less massive; greatest length and basal length smaller; maxillary arches not so heavy and less flared out; teeth slightly smaller, especially incisors; rostrum relatively longer; rostral width slightly nar- rower; rostral depth slightly shallower; auditory bullae relatively as well as actually smaller; greatest breadth across bullae and bullar depth smaller; mandibular length shorter. Compared with Dipodomys spectabilis zygomaticus, D. s. spectabilis SUBSPECIES OF Dipodomys spectabilis 3] differs in the following: Longer body and longer white tip of tail; color of upper parts slightly paler, the buffy element less heavily mixed with black; skull usually with longer nasals; least interorbital breadth usually narrower; posterolateral edge of maxillary arch slightly less flared; auditory bullae usually less expanded in front of meatus; jugals usually parallel and less divergent posteriorly; pterygoid foramen usu- ally rounder and more anterolaterally directed; rostral depth and least supraoccipital breadth usually narrower; breadth across exoccipital greater. Compared with Dipodomys spectabilis nelsoni, D. s. spectabilis dif- fers in the following: Larger in all external measurements; usually with longer white tip of tail; usually with more ochraceous buff color on dorsum; pelage more heavily mixed with black-tipped hairs; darker arietiform markings; darker subterminal band of tail; skull larger in almost all measurements; maxillary arches relatively as heavy but actu- ally smaller; auditory bullae larger; upper incisors usually wider; man- dible usually longer. Remarks. Typical Dipodomys spectabilis spectabilis is characterized by a long distal white tip of the tail, the maxillary arch slanted pos- teriorly, and both the interparietal and supraoccipital narrow. Some external and cranial characters of the type-specimen and some topotypes of D. s. spectabilis are not characteristic for the subspecies. Notably, in some topotypes, the anterior face of the maxillary arch is more angled relative to the long axis of skull and more flared out. Also the interparietal and least supraoccipital breadth in some is wide. Specimens from 19 mi W, 2 mi N Willcox, Cochise County, Arizona, are more typical. Buffy spots are occasionally present on the ventral side in specimens from various localities throughout the range of this subspecies, and more so than in any other subspecies. Less frequently there is a streak of buff-colored hair on the ventral side. A narrow, sharp zone of intergradation exists between D. s. spec- tabilis and D. s. perblandus along a line that extends down the east side of the Rincon, Empire, Santa Rita, and Patagonia mountains in Arizona and southward in northern Sonora. This zone seems to be one of secondary intergradation and shows a high degree of concordance in the characters examined. Specimens from the following localities in the zone of intergradation, when compared with typical D. s. specta- bilis, have the following characteristics: Specimens from Empire Ranch, Pima County, Arizona, show some degree of intergradation in that most adults have smaller hind feet; some have a wider interparietal 32 KANGAROO RATS and supraoccipital; and some have a shorter mandibular alveolus. Specimens from Fort Crittenden, Santa Cruz County; the vicinity of Bonita, Graham County; and the vicinity of Willcox, Cochise County, show little intergradation. Specimens from Fort Huachuca and vicin- ity, Cochise County, show some intergradation of characters as some have lighter arietiform markings and smaller external measurements. Some of these specimens have wider supraoccipitals, less breadth across the exoccipitals, more flared posterolateral edges of the maxilary arches, larger interparietal, and more uniform lacrimals. Some adults from Montezuma Canyon show intergradation in having more flared maxillary arches, more uniform lacrimals, rounder pterygoid fora- mina, narrower least interorbital breadth, and narrower breadth across the exoccipitals. Some specimens from La Sauceda, Sonora, show intergradation of characters, as evidenced by shorter tails, shorter mandibular alveolus, and wider supraoccipital. D. s. spectabilis may intergrade with D. s. bailey: in west-central New Mexico between the Gila River and the Rio Grande, but little evidence of this process is observed in the available material. Some specimens from Mangas Valley, Grant County, have a slightly greater breadth across the maxillary arches and thus are closer to D. s. bailey. D. s. spectabilis intergrades with D. s. baileyi in a wide zone along the Rio Grande in south-central New Mexico. Only 11 of the 20 meas- urements studied show taxonomic differences between these two sub- species in this region. Specimens from both Lat. 31° 47’, Long. 107° 15’, Luna County, and from Camp near Lake Palomas, Chihuahua, have some characters close to D. s. baileyi, while other characters are close to D. s. perblandus. D. s. spectabilis is not known from the valley immediately west of the Rio Grande in northeastern Chihuahua. This gap may not be a true one and is probably due to the inaccessibility of the region. Although certain areas within this gap do not seem to be suitable habitat for this subspecies, future collecting in this region may yield some D. s. spectabilis. Specimens from the southernmost part of the range of D. s. spectabt- lis in Chihuahua exhibit evidence of intergradation with D. s. zygo- maticus. Adults from the vicinities of Parrita and Pozo Mangiay have some cranial characters close to those of D. s. zygomaticus. D. s. spectabilis may intergrade with D. s. nelsoni in east-central Chi- huahua. The available material from this region is scanty. Two adults, one from near Coyamé, and one from south of Hormigas, are smaller in some external and two cranial measurements than typical D. s. spec- tabilis, and are within the range of D. s. nelsoni. SUBSPECIES OF Dipodomys spectabilis os Two adult females from 7 mi W, 2 mi S Casas Grandes, Chihuahua, KU Nos. 64083 and 64084, are clearly different from typical D. s. spec- tabilis, especially in skull characters. They are similar to D. s. per- blandus in having pale dorsal color and short white tip of the tail. Averages of three external measurements and of eight cranial measure- ments are smaller than for D. s. spectabilis. They have smaller audi- tory bullae, have wider interparietals, and supraoccipitals, and are broader across the exoccipitals. The maxillary arches are more slanted posteriorly, and the external auditory meatus has a more oval-shaped opening. It is probable that this population will merit taxonomic rec- ognition when more specimens are available. Alvarez (1960:407) assigned specimens from La Sauceda, 15 mi NNE Cananea and from 9 mi N Cananea, Sonora, to D. s. perblandus. Examination of four specimens from the former locality and one speci- men from 5 mi N Cananea, reveals that they are more typical of D. s. spectabilis. The subspecies D. s. spectabilis has not been reported pre- viously from Sonora, although in distribution maps of the species, it was assumed to be present in the northeastern part of the state. The last three localities listed under specimens examined from Luna County, New Mexico, are probably all the same. Specimens examined. A total of 331 specimens from: ARIZONA. Pima County: Empire Ranch, E Santa Rita Mts., 4,632 ft, 4 (UsNM); Empire Ranch, 50 mi E of S Tucson [=38 mi SSE], 1 (ucLa) ; 40 mi SE Tucson, at Rosemont, Santa Rita Mts., 4,700 ft, 1 (USNM) . SANTA Cruz County: Fort Crittenden, 4,800 ft, 3 (cas). GRa- HAM County: Fort Grant, 5 (USNM) ; 2 mi NW Bonita, Graham Mts., 3 (ut); 3 mi E Bonita, Graham Mts., 2 (ur). Cocuise County: 8 mi W Bowie, 1 (LAcM); 5 mi NE Willcox, 1 (ku); 3 mi N, 214 mi E San Simon, 1 (ur); 19 mi W, 2 mi N Willcox, 4 (u1); 10 mi W, 2 mi S Willcox, 2 (ur); Willcox, 4 (UsNM); 414 mi E, 234 mi S Willcox, 5 (ur) ; Dos Cabezos [= Dos Cabezas], 500 ft, 7 (Mvz), 17 (USNM) ; Fort Bowie, 7 (UsNM); Chiricahua Mts., 1 (mvz); 12 mi S Dos Cabezos [=Dos Cabezas], 1 (mMvz); 414 mi E, 24 mi S Willcox, 6 (ur); 5 mi E Portal, 3 (ur); Fairbank, 7 (AMNH), 8 (FMNH); Fort Huachuca, 9 (usnM); 5 mi S Fort Huachuca factually ESE], 7 (ur); 8 mi S Fort Huachuca [actually SE], 1 (ur); 5 mi W Herford, 2 (ku); 3 mi SW Herford, 2 (ur) ; Montezuma Canyon, Huachuca Mts., 15 (ur) ; Mouth Montezuma Canyon, Huachuca Mts., 3 (ur) ; Montezuma Canyon, 8 mi E, 14 mi S Fort Huachuca, 12 (ur) ; Montezuma Canyon, 20 mi S$ Fort Huachuca [factually 8 mi E, 14 mi S Fort Huachuca], 2 (ur) ; 9 mi 34 KANGAROO RATS N Douglas, 1 (ur) ; 6 mi NE San Bernardino, 4,000 ft, 3 (UsNM) ; S. B. Ranch [San Bernardino Ranchj, 2 (FMNH) ; San Bernardino Ranch, 3 (AMNH) , 9 (USNM) ; 18 mi E Douglas, 1 (ur). SONORA. La Sauceda, 4,700 ft, 15 mi NNE Cananea, 4 (mvz); 5 mi N Cananea, 4,750 ft, 1 (mvz). NEW MEXICO. Grant County: Silver City, 14 (UsNM) ; Mangos [=Mangas] Valley, Head of Mangos [=Mangas] Lake, 3 (UsNM) ; White Water [=Whitewater], | (UsNM) ; Hachita, 2 (Usnm). HipaLco County: 10 mi NW Lordsburg, | (LAcM) ; 12 mi S (by road) Animas, 2 (UNM) ; Hatchet Ranch, 1 (UsNM) ; 17 miS, 2 mi W Animas, 4 (KU) ; Animas Creek, 17 mi (by road) S Animas, 3 (UNM) ; 18 mi S, 3.2 mi W Animas, | (UNM) ; Adobe Ranch, N base Animas Pk., 1 (UsNM); 7.2 mi N Cloverdale, 1 (UNM) ; 4 mi N Cloverdale, 1 (uNM); T 33 S-R 19 W, Sec. 29 [about 1 mi NE Cloverdale], | (UNM) ; 36 mi S, 5 mi W Ani- mas, | (UNM); T 33 S-R 20 W, Sec. 19 [1 mi NE Cloverdale], 1 (unm) ; Upper Animas Valley, 36 mi S, 3 mi W Animas, 3 (UNM) ; 36.5 mi S, 8 mi W Animas, 1 (UNM); 3 mi W, | mi N San Luis Pass, 3 (UNM) ; Deer Creek, Culberson Ranch, | (usNM) ; 46 mi S (by road) Animas, I (uNM); Animas Valley, Lang Ranch, 1 (UsNM); Dog Spring [skin tag: Grant Co.], 8 (USNM). SIERRA CounTy: Lake Valley, 5,000 ft, .2 (USNM). Luna County: Ft. Cummings, | (usnM); 12 mi S Nutt, 1 (USNM) ; 6 mi N Deming, 1 (UsNm) ; Deming, 4 (UsNM) ; 10 mi E Dem- ing, | (UsNM) ; Florida Mts., 10 mi S, 7 mi E Deming, 1 (UNM) ; Camp No. 4, near Carrizallilo Springs, 7 (UsNM); Lat. 31° 47’ Long. 30° 1’ [Long. 107° 15’], Mex. Bound. Line, 4 (usNm) ; Lat. 31° 47’, Long. 30° 15’ [Long. 107° 15’], Mex. Bound. Line near Emory’s 5th Mon., Mex. [—Monument No. 15], 1 (usNM) ; 50 mi W El Paso, Mon. No. 15, Mex. Bound. Line, 1 (UsNM). Dona ANA County: 15 mi W Las Cruces, 5 (LACM) ; 12 mi WSW Las Cruces, 1 (Mvz). CHIHUAHUA. Camp near Lake Palomus [=Palomas], 1 (USNM) ; Mesquite [=Mosquito] Springs, near Mex. Bound. Line, 2 (UsNM) ; White Water [= Whitewater], Mex. Bound. Line, 5 (usNM); 314 mi N, 1 mi W San Francisco, 5,100 ft, 1 (KU) ; 214 mi N, % mi W San Fran- cisco, 5,100 ft, 2 (KU) ; Rancho San Francisco, 5,100 ft, 2 (ku) ; Colonia Diaz, 4,750 ft, 1 (UsNM); Vuelta de Alamos, 4,200 ft, 2 (Ku) ; Corralitos, 2 (usNM); 17 mi N Nuevo Casas Grandes, 2 (ur) ; Casas Grandes, 2 (USNM) ; | mi W Casas Grandes, 5 (ur); 7 mi W, 2 mi S Casas Grandes, 2 (ku); 11 mi SE Nuevo Casas Grandes, 2 (UNM); 14.8 mi SE Nuevo Casas Grandes, 2 (ur); 10 mi NW Galeana, 1 (ur); 4 mi S, 1 mi E Moctezuma, 4,550 ft, 3 (Ku) ; S edge Sierra Mojina, 5,200 ft, 24 mi W Gallego, 1 (Mvz); Gallego, i2 (usnM): 4.4 mi SE San Buenaventura SUBSPECIES OF Dipodomys spectabilis 35 [=Buenaventura], 1 (ur); Arroyo del Nido, 27 mi SW Gallego, 6,500 ft, 2 (mvz); 5 mi N Cerro Campana [at mouth of Canon de Santa Clara, S end Sierra del Nido], 5,350 ft, 2 (atvz) ; Ojo de Laguna, 5,200 ft, 25 mi S Galego [=Galiego], 4 (mvz); 15 mi W, 6 mi S Coyamé, 5,500 ft, 1 (Ku); Rancho La Campana, 1,470 m, 4 (AMNH) ; 38 mi N, 18 mi E Chihuahua [approx. 5 mi S Hormigas], 4,700 ft, 1 (ku) ; 4 mi N, 2 mi W Chihuahua, 4,750 ft, 1 (ku); 5 mi N, 6 mi E Chihuahua, 3 (ur); Chihuahua, 8 (USNM); 6 mi E, | mi S Chihuahua, 8 (ul); 5 mi SE Chihuahua, 5,250 ft, | (mvz); 1 mi SW Pozo Mangiay, 5,200 ft, 30 mi S Chihuahua, | (Mvz); 2 mi W Parrita, 1 (kU). Additional records. ARIZONA. Granam County: SW slopes Gra- ham Mts., near Fort Grant, 5,000 ft (Vorhies and ‘Taylor, 1922:8) ; 1 mi E Bonita, about 4,600 ft (Hoffmeister, 1956:279) . Cocuisk Coun- Ty: 5 mi E Willcox, 1 (um, Cockrum, 1960:144); Sulphur Springs Valley (Monson, 1943:98) ; San Simon Valley (Cahalane, 1939:430) ; 3/10 mi NW Portal, 1 (uA); Portal (Cahalane, 1939:431); 2 mi E Portal, 2. (um, Cockrum, 1960:144); near Chiricahua, 1 (uA); 5 mi W Herford, 2 (um, Cockrum, 1960:144); 3 mi W Herford, 6 (UM, Cockrum, 1960:144) . SONORA. 9 mi N Cananea (pcc, Alvarez, 1960:407) . NEW MEXICO. Grant County: Burro Mts., 5,700 ft. (Vorhies and Taylor, 1922:8). Hrpatco County: Lordsburg (Bailey, 1931:249) ; Playas Valley (Bailey, 1931:249); 6 mi E Cloverdale, 1 (NMsuwc) ; Dona ANA County: New Mexico State University Ranch, about 16 mi NW Las Cruces, on the Jornada Plains, 4,200 ft, 8 (NMsuUWC) . Dipodomys spectabilis perblandus Goldman Dipodomys spectabilis perblandus Goldman, J. Washington Acad. Sci., 23 (10) :466, 15 October 1933, original description. Type. Female, adult, skin and skull; No. 17748/ 24689, U. S. Biologi- cal Surveys Collection; from Calabasas [about 3,500 feet], Santa Cruz County, Arizona; obtained by Vernon Bailey, 27 October 1889, origi- nal number 611. Range. South central Arizona and north central Sonora. More specifically, in Arizona, from the vicinity of Oracle, Pinal County, and the western slopes of the Santa Catalina, the Santa Rita and the Huachuca mountains and the vicinity of Cerro Blanco, Sono- ra, west to Ajo and the Valley of the Ajo on the western slopes of the 36 KANGAROO RATS Ajo Mountains, and the Sonoita Valley within the boundary of the Organ Pipe Cactus National Monument, Pima County, Arizona, and adjoining parts of Sonora. Not known from north of the Gila River in Arizona; the northernmost known record is Florence, Pinal County, and it extends south to about 20 miles south of Santa Ana, Sonora. Limits of range are fairly well known in Arizona, but may extend farther north beyond the Gila River. The eastern limits and especially the zone of intergradation with D. s. spectabilis in Sonora need to be clarified, also the western and southern limits in Sonora, especially the area of intergradation with D. s. intermedius. Diagnosis. Size: Small; adult total length 325.9 to 337.0 mm; tail length 190.0 to 196.4 mm; body length 133.7 to 140.0 mm; hind foot length 48.0 to 50.9 mm; ear length 15.0 to 16.4 mm; distal white of tail medium, 21.3 to 29.0 mm. Color: In general, Light Ochraceous-Buff, thinly mixed with black-tipped hairs on dorsum, purest on sides and shoulders, lightest on cheeks; arietiform markings dusky; anterior ear fold dusky; large spot behind ankle grayish black; plantar stripe brown or light brown; toes ventrally light brown or yellowish; tuft of hairs at base of tail ventrally dusky or gray; dorsal and ventral tail stripes grayish black; subterminal band of tail nearly black. Skull: Small-sized; greatest length 44.1 to 44.9 mm; basal length 31.6 to 32.5 mm; length of nasals 15.6 to 16.3 mm; maxillary arch forms an almost right angle with long axis of skull; posterolateral edge of maxillary arch flared out; lacrimal narrow and uniform; greatest breadth across bullae 28.0 to 28.9 mm; supraoccipital and interparietal wide; least supraoccipital breadth 2.0 to 2.5 mm; alveolar length of maxillary toothrow 5.6 to 6.0 mm; opening of external auditory me- atus generally round; pterygoid foramen usually round; mandibular length 18.1 to 19.0 mm. Also see Table 6. Comparisons. Compared with Dipodomys spectabilis intermedius, D. s. perblandus differs in the following: Color Light Ochraceous-Buft with no pinkish shade on the sides; total length and tail length great- er; skull larger in almost all measurements, especially basal length, auditory bullae, breadth across bullae, least supraoccipital breadth, mandibular length; teeth slightly heavier; opening of external audi- tory meatus more round; jugals heavier. For comparison with Dipodomys spectabilis spectabilis, see account of that subspecies (pp. 30 ff.) . SUBSPECIES OF Dipodomys spectabilis 37 Remarks. Typical Dipodomys spectabilis perblandus is character- ized by Light Ochraceous-Buft color, thinly mixed with black-tipped hairs with a medium white tip of the tail, flared out maxillary arches, a wide interparietal and supraoccipital, and medium-sized teeth. Although the zone of intergradation between D. s. perblandus and D. s. intermedius is not well defined, the available material shows some intergradation between these two subspecies in Sonora. One adult from 20 mi S Santa Ana has some cranial characters suggestive of D. s. intermedius. D. s. perblandus intergrades, along a narrow zone, with D. s. spec- tabilis in eastern Arizona and eastern Sonora. Some of the specimens assigned here to D. s. perblandus from the following localities along the contact zone have some external and cranial characters close to those of D. s. spectabilis: ‘The vicinity of Oracle, Pinal County; the vicinity of Fort Lowell, 8 mi E Fort Lowell; Tanque Verde; and Sa- guaro National Monument, 10 mi E Tucson, Pima County. One adult from. Black Mountain, 10 mi S, 2 mi W Tucson, Pima County, has several external and cranial characters close to those of D. s. spectabilis. The lowland south of the Rincon Mountains and north of the Santa Rita Mountains provides a good opportunity for populations from the east and west sides of the mountains to interbreed. One adult from the north base of the Santa Rita Mountains, and some adults from east of Continental, Pima County, have deeper auditory bullae similar to those of D. s. spectabilis. One adult from Cerro Blanco, Sonora, has a wider rostrum, and two adults from Magdalena have slightly darker arietiform markings, and several cranial characters close to those of D.. S-Spectaniis: A few specimens from various localities throughout the range of D. s. perblandus have either buffy spots or a buffy shade on the ven- tral surface. The frequency of occurrence of the buffy color in this sub- species is less than that in D. s. spectabilis. Usually, the jugals of D. s. perblandus are parallel. However some adults from various localities throughout the range of this subspecies have bowed jugals which is a characteristic of D. s. zygomaticus. The presence of this character in some specimens of D. s. perblandus is most likely independent, because this subspecies is far removed geographi- cally from D. s. zygomaticus. Specimens from the westernmost localities of D. s. perblandus also exhibit some variation. Two adults from Gunsight, Pima County, com- pared with topotypes, have paler dorsal and ventral tail stripes, slight- ly paler upper parts, longer tails, and wider interparietals. ‘They have 38 KANGAROO RATS shorter bodies and are smaller in several cranial characters. Two adults from Pozo de San Emeterio, Sonora, average shorter in tail length, but have longer nasals, deeper rostrum, and deeper bullae than typical D. s. perblandus. These variations among specimens from the western limit of this subspecies are irregular and do not follow a uni- form pattern. The northernmost specimens of D. s. perblandus examined are from Florence, Pinal County, Arizona. Of four specimens in the AMNH collection that were collected by F. Terry on 27 March 1947, from Florence, two are D. s. perblandus and the other two are D. deserti arizonae. This record provides the only known evidence that these two species occur together. Unfortunately no field notes of Terry’s were found to detect any habitat differences, although differences are ex- pected. Recent collecting in the vicinity of Florence and directly north of it produced only D. deserti arizonae. This indicates that D. spec- tabilis does not occur farther north of Florence. It is possible that the specimens of D. s, perblandus in the AMNH collection were taken only in the vicinity of Florence, and in fact from south of the town. A specimen in the usNM collection, No. 229351 ¢, from Indian Oasis, Pima County, Arizona, was collected by A. B. Howell on 9 July 1918, original number 173. The skin of this specimen is typical of D. s. perblandus, but the cranium is more typical of D. deserti arizonae whereas the lower jaw is typical of D. spectabilis. Another specimen in the same collection (No. 229343 ¢ , from Gila Bend, Maricopa County, Arizona, collected by A. B. Howell on 22 June 1918, original number 126) is a skin typical of D. d. arizonae, but it has a skull typical of D. s. perblandus and a lower jaw typical of D. deserti. It seems obvious that there was a mix-up of the skulls of these two specimens, probably during the process of cleaning. In addition to this, the Gila Bend area does not seem to be a suitable habitat for D. spectabilis, and in the same way, Indian Oasis does not seem to be a suitable habitat for D. deserti. The card file of the U.S. National Museum, indicates that specimen, No. 229345 ¢, identified as D. spectabilis, from Gila Bend, is missing. No. 229343 from Gila Bend is here regarded as a D. deserti arizonae and No, 229351 from Indian Oasis as a D. spectabilis per- blandus. Specimens examined. A total of 262 specimens from: ARIZONA, PinaL County: Florence, 2 (AMNH); 9 mi W Oracle, 3,600 ft, 2 (ku); 5 mi W Oracle, 2 (ku); Oracle, 6 (USNM). PIMA County: 10 mi N Tucson, 2,800 ft, 3 (UsNM) ; vic. of Fort Lowell, 2 (UcLA) ; 8 mi E Fort Lowell, 2 (ucra) ; ‘Tanque Verde, 1 (ku) ; Gun- SUBSPECIES OF Dipodomys spectabilis 39 sight, 2 (usNM); 75 mi W Tucson, | (UsNM); vic. Tucson, | (UI) ; Tucson, 2 (UsNM) ; Saguaro National Mon., 10 m E Tucson, 2 (ul) ; Saguaro National Mon., 2 mi S of Park base, 1 (ur); Black Mt., 10 mi S, 2 mi W Tucson, | (KU) ; Copper Mt., Valley of the Ajo, 5 (spsNH) ; 1 mi S Copper Mt., Valley of the Ajo, 3 (spsNH) ; Ajo Valley, 2,000 ft, 3 mi W Alamo Canyon, 4 (LAcM); mouth Alamo Canyon, 2,100 ft, Ajo Mts., 3 (Lacm) ; Baboquivari Mts., T. M. Peter’s Ranch, | (usnM) ; 30 mi SE Tucson, | (usNM); 5 mi NW Sells, 3 (spsNH) ; Sells (air- port), 15 (ur); Indian Oasis [=Sells], 6 (UsNM) ; N base Santa Rita Mts., 4,000 ft, 2 (usNM); Gray’s Ranch, Sonoita Valley, 1 (spsNH) ; Hartt, 23 mi S Tucson, 8 (LAcM); Continental (26 mi S Tucson) , 2,900 ft, | (ucLa) ; Continental, 1 (UsNM) ; Sabino Canyon, 23.5 mi N, 4 mi E Sasabe, | (ut); Sabino Canyon, Baboquivari Mts., 5 (ur); 75 mi SW Tucson, 1 (UsNM); | mi S Topawa, 2 (ut); 30 mi S Tucson, 4,100 ft, 16 (KU); 14 mi E, 3 mi S Continental, 4,000 ft, 10 (KU) ; 6 mi E, 5 mi S Continental, 1 (ur); NW Santa Rita Mts., 7 mi S, 8 mi E Continental, 2 (Ku); 35 mi S Tucson, Santa Rita Range Reserve Sta., 4,300 ft, Ruelas Sta., 2 (UsNM); Santa Rita Exp. Range, NE Station, 2 (ut); 35 mi S Tucson, Santa Rita Exper. Range, 3,900 ft, Climatic Sta., 15 (usnM) ; 35 mi S Tucson, Santa Rita Range Reserve Sta., 5,800 ft, 3 (usNm); 35 mi S Tucson, Santa Rita Res., 1 (UsNM); 35 mi S Tucson, across road from Road Sta., 4,000 ft, 5 (UsNM) ; 35 mi S ‘Tuc- son, Santa Rita Range Res., Desert Canal, 3,500 ft, 1 (UsNM) ; Santa Rita Grazing Reserve, 3,600 ft, 1 (UsNM) ; Santa Rita Range Reserve, 514 mi NW Florida Ranger Sta., 3,500 ft, 8 (cas) ; Santa Rita Range Res., 414 mi NW Florida Ranger Sta., 3,500 ft, 11 (cas); 134 mi S, 1 mi W, NE Station, Santa Rita Exp. Range, 1 (ur); W slope Santa Rita Mts., 4,500 ft, 1 (ucLA); E slope Baboquivari Mts., 10 mi N Interna- tional boundary, 4,000 ft, 1 (ucLA); 1% mi E Arivaca, 3 (ur); Sapo Tank, 114 mi S, 14 mi E Arivaca, 1 (ur) ; Sapo Tank, 114 mi S, 4 mi E Arivaca, 9 (ur); 4 mi N, 1 mi E Sdsabe, 1 (ur) ; La Osa, Altar Val- ley, 3 (Mvz) ; La Osa, 7 (usNM) . SANTA Cruz County: Santa Rita Mts., below Sawmill Canon, 3,500 ft, 4 (cas) ; Tubac, | (FMNn) ; Calabasas, 10 (usNM) ; 814 mi N, 214 mi W Nogales, 1 (ku); 9 mi NE Nogales, Patagonia Mts., 3 (u1); 9 mi ENE Nogales, Patagonia Mts., 10 (ur) ; 7 mi NW Nogales, Calabasas Canyon, 3 (UI). SONORA. Pozo de San Emeterio, 814 mi N Quitovac, 4 (MVZ) ; Cerro Blanco, 1 (FMNH) ; Magadalena, 2 (usNM) ; Llano, 2 (UsNM) ; 20 mi S Santa Ana, 2,600 ft, 23 (mvz). Additional records. ARIZONA. PinaL County: between Florence and Tucson, along Hwy. 80, 1 (cm, Doutt, 1934:262; recorded as D. s. 40 KANGAROO RATS spectabilis) : 6 mi NW Oracle Junction, 5 (cm, Cockrum, 1960:144) ; 2 mi N, 5 mi W Oracle. 1 (uA); 27 mi N, 4 mi E Tucson, 1 (uA) ; few miles E Oracle (Gibbs, 1955:463) ; 1 mi S Oracle, 1 (uA, Lange, 1960: 447). Pima County: Ajo (Vorhies and Taylor, 1922:9; recorded as D. s. spectabilis) ; 3 mi E Tucson, 1 (ua, Cockrum, 1960:144) ; Black Mt., 10 mi SW Tucson, 1 (ua); 30 mi S Ajo, Organ Pipe Cactus Na- tional Monument, 2 (cm, Cockrum, 1960:144) ; Santa Rita R. S., Mel- endreth Wash, 3,700 ft, 1 (uA, Cockrum, 1960:144) ; vic. Copper Mt. (Huey, 1942:361); about 1 mi NE Gray’s Ranch (Huey, 1942:361) ; Clark Ranch, 4 mi E Arivaca, 3,890 ft, 1 (ua, Cockrum, 1960:144) ; near Sdsabe, 2 (mMsu) . SANTA Cruz County: 14 mi S Calabasas, 8 (ua, Cockrum, 1960:144). SONORA. 2 mi S Sasabe, 2 (Dice and Blossom, 1937:30); Noria (ucLA, Burt, 1938:46): Ebano (Alvarez, 1960:406) . Dipodomys spectabilis intermedius Nader Dipodomys spectabilis intermedius Nader, Proc. Biol. Soc. Washing- ton, 78 (5) :50, 21 July 1965, original description. Type. Female, adult, skin and skull; No. 82782, Museum of Verte- brate Zoology, University of California; from 16.7 miles southwest of Bamori, 1,900 feet, Sonora, México; obtained by Seth B. Benson, 25 April 1938, original number 5301. Range. West central Sonora. Known at present from the vicinity of Querobabi on the north, southward to Carbo and westward to a locality about 17 miles south- west of Bamori. Limits of the range of this subspecies are not well known. Diagnosis. Size: Small; adult total length 318.5 to 325.0 mm; tail length 184.9 to 188.8 mm; ear length 16.16 mm; white tip of tail short, 20.0 to 21.0 mm; weight 98.8 to 106.1 grams. Color: Upper parts Light Ochraceous-Buff mixed with Pinkish Buff and thinly mixed with black-tipped hairs; sides with more evi- dent Pinkish Buff; arietiform markings dusky; plantar stripes light brown; tuft of hairs at base of tail ventrally grayish; dorsal and ventral tail stripes darkish; subterminal band of tail blackish. Skull: Small-sized; greatest length 43.0 to 43.2 mm; basal length 31.0 mm; breadth across maxillary arches small; posterolateral edge of SUBSPECIES OF Dipodomys spectabilis 4] maxillary arches slightly flared; lacrimal not too uniform in shape; rostrum narrow; auditory bullae small; greatest breadth across bullae 27.0 to 27.7 mm; supraoccipital and interparietal narrow; least supra- occipital breadth 1.7 to 2.0 mm; breadth across exoccipitals narrow; external openings of auditory meati oval; incisors usually small; man- dibular length small, 17.9 to 18.0 mm. Also see Table 6. Comparisons. For comparison with Dipodomys spectabilis perblan- dus, see account of that subspecies (pp. 36 ff.) . Remarks. Typical Dipodomys spectabilis intermedius is character- ized by small size in such features as total length, skull, auditory bullae, and mandible, Pinkish Buff on sides, and a short white tail tip. This subspecies intergrades with D. s. perblandus in central Sonora. One adult from 5 mi W Querobabi, which is referred to D. s. inter- medius, has some cranial characters similar to those of D. s. perblan- dus. Variation within the range of D. s. intermedius includes the follow- ing: One adult male from 45 mi N Hermosillo has the breadth across the maxillary arches and the greatest breadth across the bullae slightly larger than typical. Two adult paratypes have the least width of the supraoccipital approaching that of D. s. perblandus. Specimens examined. A total of 18 specimens from: SONORA. 16.7 mi SW Bamori, 1,900+ ft, 9 (mvz) ; 5 mi W Quero- babi, 4 (Ku) ; 45 mi N Hermosillo, 2,100+ ft, 5 (mvz). Dipodomys spectabilis baileyt Goldman Dipodomys spectabilis bailey: Goldman, Proc. Biol. Soc. Washington, 36:140, 1 May 1923, original description. Dipodomys spectabilis clarencet Goldman, J. Washington Acad. Sci., 23:467, 15 October 1933. Type: Male, adult, skin and skull; No. 158824, U. S. Biological Surveys Collection; from Blanco, San Juan County, New Mexico; obtained by Clarence Birdseye, 19 November 1908, original number 443. Type. Male, young adult, skin and skull; No. 97185, U. S. Biological Surveys Collection; from 40 miles west of Roswell, Lincoln County (not Chaves County, Hall and Kelson, 1959:528), New Mexico; col- lected by Vernon Bailey, 13 June 1899, original number 6961. 42 KANGAROO RATS Range. Northeastern Arizona; northwestern, central, and southeast- ern New Mexico; western Texas. More specifically, in northeastern Arizona, from the western side of the Chinle Valley, to about 25 miles southwest of Chinle, Apache County. In northwestern New Mexico, from the San Juan River Val- ley, to Blanco and Canon Largo, San Juan County, to the vicinity of Gallup, McKinley County, to San Agustin Plains, Catron County, to Rio Alamosa Valley, Socorro County, to the vicinity of Las Palomas, Sierra County, and the eastern valley of the Rio Grande. In eastern New Mexico, from the Jemez River Valley, Sandoval County, to the vicinity of Santa Fe, Santa Fe County, to the vicinity of Santa Rosa, Guadalupe County, and along the eastern valley of the Pecos River to the vicinity of Floyd, Roosevelt County, to the vicinity of Caprock, Chaves County, south to southeastern New Mexico. In western Texas, from the eastern valley of the Rio Grande, to the vicinity of Marfa, Presidio County, and from the vicinity of Andrews, Andrews County, to the vicinity of Tarzan, Martin County, south to the vicinity of Mid- land, Midland County, to Odessa, Ector County, and the vicinity of Iraan, Pecos County. Limits of range are fairly well known. This race may be found in southeastern Utah and southwestern Colorado. Also. it may occur south of the known range in western Texas. Diagnosis. Size: Large; adult total length 351.0 to 374.0 mm; tail length 207.0 to 224.0 mm; body length 146.4 to 156.0 mm; hind foot length 54.6 to 57.0 mm. Color: Upper parts, in general, Light Ochraceous-Buff and occa- sionally Pinkish Buff, purest on sides and shoulders, moderately mixed with black-tipped hairs, especially over top of head and back; arieti- form markings blackish; anterior ear fold blackish; large spot behind ankle blackish; plantar stripe brownish black to black; tuft of hairs at base of tail ventrally blackish; dorsal and ventral tail stripes blackish, inconspicuously mixed with gray; subterminal band of tail black. Skull: Large and massive; greatest length 46.3 to 47.9 mm; basal length 34.2 to 35.6 mm; maxillary arch heavy; dorsal anteromedial edge of maxillary arch projecting farther forward along premaxilla; maxillary arch not sharply slanted posteriorly, and its posterolateral edge not flared out; breadth across maxillary arches 26.7 to 28.0 mm; lacrimal wide and uniform; auditory bullae large; greatest breadth across bullae 29.8 to 30.5 mm; opening of external auditory meatus large and oval shaped; pterygoid foramen large; mandibular length 20.1 to 21.4 mm; incisors heavy. Also see Table 6. SUBSPECIES OF Dipodomys spectabilis 43 Comparisons. For comparisons with Dipodomys spectabilis specta- bilis, see account of that subspecies (pp. 30 ff.) . Remarks. Typical Dipodomys spectabilis baileyi is characterized by an Ochraceous-Buft color and occasionally a Pinkish Buff color, mod- erately mixed with black-tipped hairs and with the dorsal and ventral tail stripes grayish black. Most external and cranial measurements are the largest for the species. D. s. baileyi has large bullae, heavy maxil- lary arches, and heavy teeth. Goldman (1933:467) regarded the populations in northwestern New Mexico as a distinct subspecies (D. s. clarencez) . In the 20 meas- urements studied in this report, none appeared to be distinctive in these northwestern populations. In comparing D. s. clarencei with D. s. baileyi, Goldman (1933) stated that the former has a similar color, but less distinct arietiform markings and the upper surface of the muzzle behind the nasal pad is more extensively white. No real difference was found in the distinctness of the arietiform markings be- tween specimens from northwestern New Mexico and those from cen- tral and southeastern New Mexico. Also, the white spot behind the nasal pad does not seem to be a good character on which to base dis- tinctions, since it is not present in the majority of the specimens from northwestern New Mexico, and it is present in many specimens from central and southeastern New Mexico. With regard to cranial charac- ters, Goldman (1933) stated that D. s. clarencei is smaller than D. s. baileyi, with a relatively broader frontal region, with more strongly developed external angles on the maxillary arches (tending to form more strongly projecting hooks), and with narrower incisors. The hook development of the maxillary arches is not a distinctive character for the northwestern populations, because it is present in many spect- mens throughout the range of D. s. baileyi. No real differences were detectable in the width of the incisors or in the least interorbital breadth (an indication of frontal width) in a comparison of north- western populations and the rest of D. s. baileyi. In a scatter diagram (Fig. 7) using greatest breadth across the bullae and greatest length of the skull, it was not possible to show any difference in the size of the skull between the two populations. Thus D. s. clarencei is regarded here as consubspecific with D. s. baileyi. Dipodomys spectabilis baileyi intergrades with D. s. spectabilis in a wide zone along the Rio Grande in south central New Mexico and western Texas (see also Remarks under D. s. spectabilis, p. 32). Adults from Magdalena and from the vicinity of Socorro, Socorro County, ‘9suUvL JO JIed ULDISIMYWOU WOT] ,.299UIAD]I,, ‘Sq pur ‘OorxoJy MON pue vuozity wory 1€aj1pq ‘sq A[Npe poauTUeXd [[e Jo [[Nys ay) Jo yuo] jSa]VIIS PUL ILT[NQ IYI sso1V YIpPvaiq jsaivaiIs UsIMI9q UOsIIvduIOD SuIMOYsS UTVASLIP 1911vIg */ “SI TINNS JO HLON3ST 18317349 0-6% S- 0-8b S- Old S- 0-96 S- O-St 0-62 ole aBuel jo ped Ua}saMUWOU WO} ,,1edUdIeIO,, o ® e OOIX9/\| MAN puke eUOZIIW WOd} IAaieg e@ GREATEST BREADTH ACROSS BULLAE SUBSPECIES OF Dipodomys spectabilis 45 New Mexico, have narrower rostra than typical D. s. baileyi. The skull of the adult from Parker Lake, east Organ Mountains, Dona Ana County, is narrow across the maxillary arches and in this respect is sim- ilar to D. s. spectabilis. Many specimens from several localities in western Texas are smaller in several external and cranial measure- ments than typical D. s. baileyi, to which they are referred herein, but are within the range of D. s. spectabilis. Compared with typical D. s. baileyi, adults from the vicinity of Chinle, Apache County, Arizona, and from Fruitland, San Juan Coun- ty, and from Santa Fe, Santa Fe County, New Mexico, are smaller in some cranial characters. Some adults from northwestern New Mexico have shorter tails and smaller hind feet. Others from central New Mex- ico are smaller in rostral depth and in bullar depth. These variations are not uniform, and the populations are not well marked for taxo- nomic recognition. Three specimens in the UNM collection, Nos. 14870 ¢, 14871 9, and 14872 4, from 15 mi W, 7 mi N Jal, are new records of this subspecies for Lea County, New Mexico. Also three specimens in the LAcm col- lection, Nos. 41244 skin only, 21254, and 21264, from 20 mi N Pecos, Loving County, represent new county records in Texas. Specimens examined, A total of 211 specimens from: ARIZONA. APACHE County: 8 mi S Chin Lee [now Chinle], 5,500 ft, 1 (USNM). NEW MEXICO. San Juan County: Fruitland, 4 (usNm) ; Blanco, 3 (USNM); 7 mi S, 6 mi W Bloomfield, T 27 N-R 12 W, Sec. 4, 2 (UNM) ; 1 mi E, 9 mi S Bloomfield, T 27 N-R 11 W, Sec. 11, 1 (UNM) ; Gallegos Store, 10 mi S, 7 mi W Bloomfield, 1 (UNM) ; Chaco Canyon National Mon., 6,400 ft, 4 (mvz) ; Chaco Canyon, 6,400 ft, 1 (UsNM). McKINLEY County: 15 mi NW Gallup, 2 (UsNM) . SANDOVAL CouNTy: Jemez River Valley, 1 (AMNH) ; 12 mi NW Alameda, 5,500 ft, 2 (Mvz). VALENCIA County: Juan Tafoya, 1 (UsNM) ; 10 mi SE Belen, 5,000 ft, ] (UNM). BERNALLIO County: 6 mi E, 1 mi N Alameda, | (UNM) ; Juan Tabo Road, 2 mi W recreational area, 1 (UNM); Mesa, 5 mi W Albuquerque, 1 (UNM); Albuquerque, 3 (USNM). CATRON COUNTY: Mayberry Ranch, 75 mi W Magdalena, 6,600 ft [skin tag: Socorro Co.], ] (USNM) . Socorro County: 10.5 mi W, 4.7 mi N Bernardo, | (UNM) ; Juniper zone, below Lardon, T 3N, R 3W, Sec. 36, 1 (UNM); 14 mi S, 2 mi W Bernardo, 1 (UNM); Bear Spring Mts., 3 (UsNM); Riley, 1 (USNM); 9 mi N Lemitar, Rio Salado, 1 (UNM); Gallina Mts., 2 (USNM) ; 114 mi N, 5 mi W Magdalena, 1 (ku) ; Magdalena, 2 (UsNM); 46 KANGAROO RATS Socorro, 5 (USNM) ; Range, 2 mi SW Socorro, 4,700 ft, 2 (mMvz) ; 4 mi S, 3 mi W Socorro, 8 (UNM); 15 mi W, 1] mi S$ Magdalena, San Au- gustin [=Agustin] Plains. | (UNM); Big Rosa Canon, 1 (uNM) ; Big Pigeon Ranch, San Mates [Mateo] Mts., 1 (usNM); Rio Alamosa, 15 mi N Ajo Caliente, 6,900 ft, 5 (UsNM); 7.5 mi E Springtime Canyon, San Mateo Mts., | (UNM) ; Nogal Canyon, 28 mi S, 17 mi W San An- tonio, 1 (UNM). SIERRA CouNTy: 51% mi E, 1 mi N Engle, 2 (UNM). Dona ANA County: 25 mi N Las Cruces, 1 (UNM) ; Las Cruces, on the mesa, 4,000 ft, | (UsNM) ; Parker Lake, E Organ Mts., 2 (UsSNM) . SAN- TA Fre County: 6 mi N of NE corner Santa Fe Municipal Airport, | (KU) ; 5 mi NW Santa Fe, T 17N, R 8W, Sec. 1 and 12, 1 (un); 1 mi W Santa Fe Municipal Airport, 1 (ku), 1 (ur); Santa Fe Municipal Airport, 6,300 ft, 1 (ur); 8 mi SW Santa Fe, 5 (ku); 11 mi SW Santa Fe, 4 (cas) ; 12 mi SW Santa Fe, N border of Airport, 1 (cas); 15 mi SW Santa Fe, 1 (cas), T 15N, R 8E, Sec. 34 and 35, 1 (ur) ; Simmons Ranch, 8 mi SE Golden, 6,500 ft, 1 (vz). TORRANCE County: 31% mi S, 814 mi E Cline’s Corners, 6,500 ft, | (Ku) ; Monzano Mts., E foot- hills N end, 6 (UsNM); 10 mi E, 2 mi S Willard, 1 (UNM); Mesa Ju- manes, N portion [34° 25’ N, 106° 05’ W], 2 (usNM) . GUADALUPE Coun- Ty: Santa Rosa, | (UsNM). De Baca County: Alamogordo Reservoir below dam, 9 mi N, 9 mi W Ft. Sumner, | (UNM). LINCOLN County: Ancho, 2 (USNM); French’s Ranch, 12 mi NW Carrizzo, 5,400 ft, 1 (Mvz) ; W edge lava bed [8 mi NW Carrizzo], 1 (UNM) ; 7 mi W Car- rizzo, 1 (uM); Capitan, Flying H Ranch, 6,000 ft, 2. (usnm) ; 44 mi NW Roswell, 19 (mMvz); 40 mi W Roswell, 1 (usnM) ; 30 mi W Ros- well, 2 (UsNM). OTERO County: 12 mi SW Alamogordo, 3 (SDSNH) . Cuaves County: 35 mi N Roswell, 1 (usnmM); 20 mi N Roswell, 3 (USNM) ; 9.3 mi E, 8.2 mi S Roswell, 1 (UNM) . Eppy County: Carlsbad Cave, 3 (usNM) ; 6 mi S, 10 mi W White’s City, 4,100 ft, 1 (Ku). LEA County: 15 mi W, 7 mi N Jal, 3 (UNM). TEXAS. Et Paso County: El Paso, Flats E Franklin Mts., 1 (usNM); 12 mi E, 1 mi S City Hall, El Paso, 4,000 ft, 1 (ku) ; Fabens, San Fe- lipe Arroyo, | (UNM). HupspeTH County: Sierra Blanca, 3 (USNM). CULBERSON County: 55 mi N Van Horn, 3,600 ft, 1 (Tewc) ; 11 mi N Kent, 4,500 ft, 2 (rcwc); 6 mi N Kent, 4,000 ft, 3 (rcwc) ; 16 mi E Van Horn, 3,000 ft, 1 (rewc) ; Kent, 1 (usnM); 16 mi SE Van Horn, 4,100 ft, 1 (rewc). Jerr Davis County: Fort Davis, | (UM); Vaten- tine, 3 (UsNM) ; 1414 mi SW Fort Davis, 2 (UM). PREsip1Io County: 10 mi NE Marfa, 5 (um); Marfa, 4 (ur), 1 (um). Lovine County: 20 mi N Pecos, 3 (LACM). REEVES County: Toyah, 2 (usnm) ; 20 mi S Pecos, 2,900 ft, 1 (Ku); 5 mi E Toyahvale, 2 (UsNM). Warp County: SUBSPECIES OF Dipodomys spectabilis 47 Monahans, 16 (UsNM); Grand Falls | =Grandfalls], 8 mi SW Castle Mts., | (UsNM). PEcos County: 20 mi E Adams [about 5 mi NW Iraan], ] (USNM). ANDREWS County: 14 mi S Andrews, Sam Arnett Ranch, 4 (uM). Ecror County: 3 mi NE Penwell, 1 (ur). CRANE County: Castle Mts., 7 mi SW Castle Gap, 1 (USNM). Additional records. ARIZONA. Coconino County: 5 mi E Rainbow Lodge, 6,000 ft. (Hoffmeister, 1977:150) not plotted on Fig. 5. APACHE County: 10 to 25 mi SW Chinle (Goldman, 1933:467) . NEW MEXICO. (All from Bailey, 1931:259-260, unless otherwise noted) , SAN JUAN County: near Bloomfield, N side San Juan River: Largo Canyon [=Canon Largo]; Blanco Canyon; San Juan Valley, E base Chuska Mts.; Kimbetoh Valley [=Kinebeto Wash]; Escavada Val- ley [=Escarbada Wash]. McKINLEY County: N Hosta Butte Mts.; W Gallup. SANDOvAL County: Valley of Salado Creek, E and N Cabezon; on the mesa, 6 mi E Algodones. VALENCIA County: Cubero; Laguna; 15 mi SW Acoma. BERNALLIO County: 8 mi NNW Albuquerque (Ivey, 1957:496) ; on the mesa, 3 mi E Albuquerque; W base Sandia Mts., E Albuquerque, 6,000 ft (Vorhies and ‘Taylor, 1922:8); 15 mi WSW Albuquerque, 3 (Ivey, 1957:496). Carron County: foothills of Datil Mts.; edge of San Augustin [=Agustin] Plain. Socorro County: foot- hills of Gallina Mts., Plains near Magdalena; 3 or 4 mi NW Socorro. SIERRA County: Jordana Valley; on the mesas about Cuchillo; on the mesas near Las Palomas. DoNA ANA County: between Garfield and Rincon; 8 mi E Mesilla Park, 4,800 ft; base Organ Mts., 5,200 ft; E base Franklin Mts. GUADALUPE County: 8 or 10 mi N Santa Rosa. DE Baca County: N Fort Sumner. LINCOLN County: NW base Jicarillo Mts., 2; 50 mi NW Roswell; on the Malpais, W Oscuro (Blair, 1941: 223). OTERO County: E border Tularosa Valley; S end Tularosa Val- ley, near Jarilla. CHaves County: 15 mi N Roswell; E side Pecos River, 15 mi NE Roswell (Vorhies and Taylor, 1922:9) ; 12 mi NW Roswell; 4 mi W Caprock, 2 (Ramsey and Carley, 1970:351) ; 3 mi W and 1 mi N Caprock, 1 (Judd and Schmidly, 1969:382). Eppy County: along railroad, between Roswell and Carlsbad; foot Guadalupe Mts., 30 mi W Carlsbad; Carlsbad (Vorhies and Taylor, 1922:9) ; Pecos Valley, 30 mi E Carlsbad. RoOosEvELT County: 9 mi S and 1 mi W Tolar (Best, 1972:201) ; 4mi W Floyd (Best, 1972:202) . TEXAS. Ex Paso County: 10 mi N El Paso, E base Franklin Mts., 1 (Bailey, 1905:147); lower edge Franklin Mts. (Vorhies and Taylor 1922:9) . CULBERSON County: Van Horn (Bailey, 1905). Jerr Davis County: 16 mi NE Ft. Davis, | (rewc) ; 4 mi SW Fort Davis, 5,000 ft, 48 KANGAROO RATS 1 (um, Blair, 1940:29); 12 to 14 mi SW Fort Davis, 11 (uM, Blair, 1940:29) . Presipio County: 11 mi W Valentine, 3 (TMM) ; about 7 mi NE Marfa, 5 (uM, Blair, 1940:29) ; 2 mi S Paisano, 3 (Tcwc) . REEVES County: Pecos (Bailey, 1905): Toyahvale (Bailey, 1905). ANDREW County: 25 mi NE Kermit, | (Packard and Judd, 1968:537). WINKLER County: 7 mi SW Kermit, 3 (Packard and Judd, 1968:537) . Pecos County: Adams [about 5 mi NNW Bakersfield (Bailey, 1905) ]. Ector County: Odessa (Bailey, 1905). Martin County: all from Ramsey and Carley (1970:351): Midland Water Station (7 mi § Pa- tricia) ; 7 mi W ‘Tarzan, 2; 12 mi S Flower Grove, 2; 1 mi S and 18 mi W Stanton, 3. Miptanp County: 8 mi W and 5 mi N Midland, 13 (Ramsey and Carley, 1970:351) . Dipodomys spectabilis zygomaticus Goldman Dipodomys spectabilis zygomaticus Goldman, Proc. Biol. Soc. Wash- ington, 34:140, | May 1923, original description. Dipodomys nelsoni: Baker and Greer, 1962:100 (part). Type. Male, young adult, skin and skull; No. 96432, U. S. Biological Surveys Collection; from Parral [=Hidalgo del Parral], southern Chi- huahua, México; obtained by E. A. Goldman, 17 September 1898, orig- inal number 13030. Range. South central Chihuahua and north central Durango. More specifically, west in Chihuahua from the vicinity of Hidalgo del Parral, east to the vicinity of Bufalo and Salaices. North from the vicinity of Ciudad Camargo and south of the Rio Conchos in Chihua- hua, south to north central Durango around the vicinity of La Reso- lana. Limits of the range are well known only on the eastern side; more collecting is still needed. Limits in the other directions are poor- ly known and need to be clarified. More collecting west of the present known range may reveal D. s. zygomaticus to be present as far west as the valley east of the San Juan River. Also future collecting may show a wider range in northwestern and north-central Durango and may bring D. s. zygomaticus in contact with D. s. nelsoni. Diagnosis. Size: Medium; adult body length 135.7 to 140.0 mm; white tip of tail medium 20.0 to 28.0 mm. Color: In general, Light Ochraceous-Buff, purest on sides, rather heavily mixed with black-tipped hairs on dorsum, especially over top SUBSPECIES OF Dipodomys spectabilis 49 of head, back, and rump; arietiform markings black; anterior ear fold black; large spot behind ankle black; plantar stripes brownish or dusky; tuft of hairs at base of tail ventrally black; dorsal and ventral tail stripes gray mixed with black; subterminal band of tail black. Skull: Medium-sized; length of nasals 16.0 to 16.3 mm; maxillary arch heavy; posterolateral edge of maxillary arch usually flared out; breadth across maxillary arches 25.9 to 26.9 mm; least interorbital breadth 16.0 to 16.8 mm; auditory bullae usually expanded in front of meatus; jugals usually divergent posteriorly; pterygoid foramen usually round. Also see Table 6. Comparisons. Compared with Dipodomys spectabilis cratodon, D. s. zygomaticus differs as follows: Total length greater and tail usually longer; upper parts more heavily mixed with black-tipped hairs; arieti- form markings usually darker; skull shorter as indicated by greatest length; maxillary arch slightly less heavy and less angled with long axis of skull; nasals longer; region of premaxillaries and nasals an- terior to maxillary arch narrower; interorbitally wider; least supra- occipital breadth usually less; incisors narrower and less massive; jugals usually more divergent posteriorly; auditory bullae usually more inflated anterior to the opening of the external auditory meatus. Compared with Dipodomys spectabilis nelsoni, D. s. zygomaticus differs as follows: Slightly larger in all external measurements; usually with longer white tip of tail, but relatively same length; usually with more ochraceous buff color; more heavily mixed with black-tipped hairs; darker arietiform markings; skull usually larger in all measure- ments; maxillary arches relatively as well as actually heavier; auditory bullae relatively as well as actually larger; jugals usually divergent posteriorly; auditory bullae usually expanded anterior to opening of external auditory meatus; upper incisors usually wider; mandible usu- ally longer. For comparison with Dipodomys spectabilis spectabilis, see account of that subspecies (pp. 30 ff.) . Remarks. Typical Dipodomys spectabilis zyogmaticus is character- ized by a Light Ochraceous-Buff color, rather heavily mixed with black-tipped hairs. The auditory bullae are usually expanded in front of the meatus, and the jugals are usually divergent posteriorly. Goldman (1923:141) in his diagnosis of D. s. zygomaticus stated that the skull is similar to that of D. s. spectabilis, but “broader especially posteriorly between outer sides of audital bullae.” In comparing the averages of the greatest breadth across the bullae of this subspecies 50 KANGAROO RATS with those of D. s. spectabilis, no significant difference was found. Only the specimens from the type-locality and some specimens from 2 mi W Parral and 5 mi E Parral are broad across the bullae. In all other localities where this subspecies is found, the average width across the auditory bullae is within the range of D. s. spectabilis. Goldman ap- parently based his diagnosis of D. s. zygomaticus on the four specimens then available to him from the type-locality. In a scatter diagram based on nasal length and least interorbital breadth, it was possible to separate 96% of all adults examined of D. s. zygomaticus from 86.6% of all adults examined of Chihuahuan D. s. spectabilis (see Fig. 8, and also comparisons with D. s. spectabilis) . D. s. zygomaticus in its present range is far removed geographically from D. s. cratodon to the southeast. The species spectabilis apparently has been present at one time or another throughout the elevated plains of central Durango and west central Zacatecas. ‘The contact zone between D. s. zygomaticus and D. s. spectabilis is not well defined; however, specimens from the northern part of the range of D. s. zygomaticus in Chihuahua show intergradation with D. s. spectabilis. It is believed that the Rio Conchos is an effective barrier between these two subspecies. Specimens from Santa Rosalia and from 2 mi SE Boquilla, which are referred here to D. s. zygomati- cus, may be regarded as intergrades. Dipodomys spectabilis zygomaticus intergrades with D. s. nelsoni in the vicinity of Bufalo and Salaices in south central Chihuahua, and in the vicinity of La Resolana in north central Durango. Future collect- ing may reveal a greater degree of intergradation in this area. For a discussion of the zone of intergradation and the degree of overlap be- tween the measurements studied, see Remarks under D. s. nelsoni (pp. 57-58) . Three specimens in the msu collection, Nos. 4909-11, from 12 mi NW La Resolana, Durango, were assigned by Baker and Greer (1962: 101) to D. nelsoni. Two of these specimens (Nos. 4909-10) were ex- amined (No. 4911 was deposited at the Department of Game, Mexico City, México) , and are referred here to D. s. zygomaticus. One of the specimens (No. 4909 4), seems closer in its measurements to D. s. nelsoni because it is a subadult. The other specimen, No. 4910, is an adult female and its measurements are within the range of D. s. zygo- maticus, although smaller than average. One adult specimen from 414 mi ESE Boquilla, Chihuahua, is typi- cal of D. s. zygomaticus in coloration, but with a larger than typical skull and with incisors as heavy as those of D. s. cratodon. Also it has 18-0 ‘ e spectabilis o zygomaticus eo © @ 17-0 16-0 15-0 5 15-0 ‘5 16-0 5 17-0 5 LEAST INTERORBITAL BREADTH Fig. 8. Comparison between length of nasals and least interorbital breadth of all examined adult D. s. zygomaticus (except those from zone of intergrada- tion with D. s. nelson?) , and all examined adult Chihuahuan D. s. spectabilis. The equation of the discriminant function line which best separates these populations is approximately y = —.44+ 1.6.x where y is the length of the nasals and x is the interorbital breadth. 52 KANGAROO RATS wide nasals and large bullae, but the bullae are not expanded anterior to the opening of the external auditory meatus. Jugals in this speci- men are not divergent. Specimens examined. A total of 73 specimens from: CHIHUAHUA. Santa Rosalia [=Ciudad Camargo], 4 (usNM); 2 mi SE Boquillas [=Boquilla], 4,700 ft, 3 (Ku) ; 4.5 mi ESE Boguillas, 4,700 ft, 1 (ku); 7.5 mi ESE Boquillas, 4,700 ft, 1 (Ku) ; 9.5 mi ESE Boquillas, 4,700 ft, 2 (ku); 10.5 mi ESE Boquillas, 4,700 ft, 3. (KU) ; 13.5 mi ESE Boquillas, 4,700 ft, 4 (kU) ; 14.5 mi ESE Boquillas, 4,700 ft [about 3 mi NW Bufalo], 1 (ku); 15 mi ESE Boquillas, 4,700 ft [about 2.5 mi NW Bufalo], 12 (ku); 1 mi W Bufalo, 4,700 ft, 1 (KU) ; 1 mi S Bufalo, 4,700 ft, 1 (Ku); 29 mi N, 12 mi E Parral [=Hidalgo del Parral], 1 (ku); 22 mi N, 8 mi E Parral, 1 (ku); 15 mi N, 5 mi E Parral, 1] (ku); 12 mi N, 2 mi E Parral, 1 (ku); 19.5 mi WSW Jimeé- nez, 5,000 ft, 3 (KU) ; 21.5 mi WSW Jiménez, 4,800 ft, 1 (ku); 6 mi N Parral, 1 (KU); 5 mi N Parral, | (KU) ; 3 mi NNW Hidalgo del Parral, 2 (Mvz); 2 mi W Parral, 6,200 ft, 9 (mvz) ; Parral, 4 (USNM); 5 mi E Parral, 5,700 ft, 9 (kU); 21.5 mi E Parral, 5,200 ft, 2 (ku); 23 mi E Parral, 1 (ku); 10 mi SE Parral, 6,000+ ft, 1 (kU). DURANGO. 12 mi NW La Resolana, 6,000 ft, 2 (Msv) . Additional records. CHIHUAHUA. 18 mi SSE Villa Matamoros, 5,700 ft (Baker and Greer, 1962:101) . DURANGO. 12 mi SE Las Nieves, 5,750 ft (Baker and Greer, 1962: 101). Dipodomys spectabilis cratodon Merriam Dipodomys spectabilis cratodon Merriam, Proc. Biol. Soc. Washington, 20:75, 22 July 1907, original description. Type. Male, young adult, skin and skull; No. 78953, U. S. Biological Surveys Collection; from Chicalote, Aguas Calientes [now Aguascali- entes], México; obtained by E. W. Nelson and E. A. Goldman, 2 July 1896, original number 9734. Range. East-central Zacatecas, northeastern Aguascalientes, and western San Luis Potosi. More specifically, west from Canitas in central Zacatecas to Chica- lote in central Aguascalientes, east to vicinity of Herradura in western San Luis Potosi and to Jesus Maria, the southeasternmost known rec- SUBSPECIES OF Dipodomys spectabilis 53 ord in San Luis Potosi. Limits of range not well known; future col- lecting may reveal that this subspecies covers most or all of central Zacatecas and may also occur in east central Durango, southeastern Aguascalientes, northeastern Jalisco, northern Guanajuato, and even in northwestern Queretaro. Diagnosis. Size: Medium; adult total length 326.5 to 337.0 mm; tail usually short. Color: In general, Light Ochraceous-Buff, thinly mixed with black-tipped hairs on dorsum, purest on sides; arietiform markings usually dusky; anterior ear fold black; large spot behind ankle dusky to gray; plantar stripe dark brown to brown with lighter shade on ventral side of toes; tuft of hairs at base of tail ventrally dusky; dorsal and ventral tail stripes dusky mixed with gray; subterminal band of tail blackish. Skull: Medium-sized, massive and squarish; greatest length 44.0 to 45.2 mm; length of nasals 15.5 to 16.0 mm; posterolateral edge of maxillary arch usually flared out; maxillary arch usually forms an al- most right angle with long axis of skull; region of premaxillaries and nasals immediately anterior to maxillary arch wide; least interorbital breadth 15.5 to 16.0 mm; interparietal and supraoccipital usually nar- row; least supraoccipital breadth 1.0 to 1.5 mm; incisors broad and heavy; pterygoid foramen usually round; auditory bullae large; open- ing of external auditory meatus usually oval. Also see Table 6. Comparisons. Compared with Dipodomys spectabilis nelsoni, D. s. cratodon differs in the following: Total length and hind foot longer; color more buffy and darker; arietiform markings and subterminal band of tail darker; skull larger and heavier; maxillary arches heavier; nasals longer; interorbital breadth wider; incisors heavier; molariform teeth larger; auditory bullae larger; external opening of auditory meatus larger and more oval; pterygoid foramen rounder; mandible longer and heavier. For comparison with Dipodomys spectabilis zygomaticus, see account of that subspecies (p. 49). Remarks. ‘Typical Dipodomys spectabilis cratodon is characterized by a medium-sized, squarish skull, wide rostrum immediately anterior to the maxillary arches, heavy incisors, and narrow supraoccipital. The present known range of D. s. cratodon is far removed from that of D. s. zygomaticus, which is the closest to it morphologically. There 54 KANGAROO RATS is no known evidence that these two subspecies were in contact at any time, although it is possible that there was a contact zone in central Durango. Also, there is no contact at the present time with D. s. nel- soni, but future collecting may show a secondary zone of intergrada- tion in southeastern Durango, in north central Zacatecas, or in central San Luis Potosi. Alvarez (1960:408) assigned a specimen or specimens (no number is given) from 3 mi N Lulu, Zacatecas, to this subspecies. Although I did not examine the material that Alvarez (1960) used in support of his statement that the range of D. s. cratodon covers all of Zacatecas, I believe it is most probable that specimens from near Lult are D. s. nelsoni. Four of a series of five specimens in the mvz collection (the fifth was deposited at the Direcci6én General de Caza in México) , from the same aforementioned locality, were examined and all were typical of D. s. nelsont. Merriam (1907:75), in his original description of this form, stated that the skull is the largest of the genus, deep vertically, and with a broad rostrum. It was found that averages of the greatest length are smaller than in D. s. zygomaticus, but the basal length, breadth across the maxillary arches, and greatest breadth across the bullae are about the same. However, D. s. baileyi is the largest in all these measure- ments. Average bullar depth of D. s. cratodon is slightly larger than that of D. s. zygomaticus but is smaller than in D. s. baileyi. Average rostral width is slightly smaller and average rostral depth is smaller than for D. s. baileyi. If Merriam (1907) is referring to the part of the skull immediately anterior to the maxillary arches as the rostrum, then it is true that this region is broader in D. s. cratodon than in any other subspecies of D. spectabilis. It has been observed that kangaroo rats in central Zacatecas bear some resemblance to D. s. zygomaticus and/or D. s. nelsoni. One adult from Canitas compared with typical D. s. cratodon has some external and cranial characters to suggest D. s. zygomaticus. In some skull char- acters, specimens from central Zacatecas are smaller. It is hard to say whether these specimens are closer to D. s. zygomaticus or D. s. nelsoni, because there is no known contact zone between D. s. cratodon and either of these two subspecies. The closest recorded locality is that for a specimen of D. s. nelsoni, 10 mi SW Yerbanis, 6,200 ft, Durango (Baker and Greer, 1962:100) . Specimens from southeastern Zacatecas and northwestern San Luis Potosi are smaller in many characters than typical D. s. cratodon. The SUBSPECIES OF Dipodomys spectabilis 55 difference is slight and irregular and does not seem to be taxonomi- cally significant. Dalquest (1953:118) made a similar observation about the specimens that he had examined from western San Luis Potosi. The small size of specimens from this part of the range of D. s. cratodon in Zacatecas and San Luis Potosi may suggest intergra- dation with D. s. nelsoni. Specimens from southwestern San Luis Po- tosi are more typical of D. s. cratodon although some have darker arietiform markings and some specimens from Jesus Maria are smaller in some characters. The type-specimens and topotypes have narrower ventral tail stripes, smaller pterygoid foramina, and the maxillary arches of one young adult male (UusNM No. 80354) slant more posteriorly than in other specimens assigned to this taxon, The interparietal bone in this subspecies is either absent or fused with the supraoccipital in 47.5% of all the specimens examined. This is a much higher percentage than in any other subspecies of D. s. spectabilis. Specimens reported on in this study show a considerable extension of the present known range of this subspecies (Hall and Kelson, 1959: 528) . Specimens from Canitas, Zacatecas, represent a northwestern ex- tension of about 50 miles in central Zacatecas and specimens from Jesus Maria, San Luis Potosi, represent a southeastern extension of about 70 miles in southwestern San Luis Potosi. The specimens from both localities are in the USNM. Specimens examined. A total of 65 specimens from: ZACATECAS. Canitas, 3 (usNM) ; Villa de Cos, 6,700 ft, 2 (KU) ; 4.5 mi E Fresnillo, 1 (mvz):; 8 mi SE Zacatecas, 7,225 ft, 3 (Ku); 5 miS Ojo Caliente, 2 (ur); Berriozabal, 4 (usNM) ; Real Di Pinos [=Pinos], 4 (AMNH). AGUASCALIENTES. 7 mi N Rincon, | (ur); 4.5 mi N Rincon de Romos, 5 (ur); 1 mi S, 6 mi E Rincén de Romos, 6,550 ft, 2 (KU); 1 mi N Chicalote, 1,900 m, 1 (Mvz) ; Chicalote, 11 (USNM). SAN LUIS POTOSI. 4.5 mi SW Herradura, 7,200 ft, 3 (Ku); 8 mi W Ramos, 6,700 ft, 1 (KU): Hacienda La Parada, 5 (usNM); Jesus Maria, 17 (USNM). Additional records. SAN LUIS POTOSI. 2 km E Illescas, 13 (Lsu, Dalquest, 1953:118); 8 mi SW Ramos, 6,700 ft, 1 (Ku); 7 km NW Palmas, 1 (Lsu, Dalquest, 1953) ; Salinas, 1 (Lsu, Dalquest, 1953) ; 4 km E Salinas, 1 (Lsu, Dalquest, 1953). 56 KANGAROO RATS Dipodomys spectabilis nelsoni Merriam Dipodomys nelsoni Merriam, Proc. Biol. Soc. Washington, 20:75, 22 July 1907, original description. Type. Male, young adult, skin and skull; No. 79439, U. S. Biological Surveys Collection; from La Ventura, Coahuila, México; obtained by E. W. Nelson and E. A. Goldman, 10 August 1896, original number 9998. Range. Southeastern Chihuahua, northeastern Durango, western and southern Coahuila, northern Zacatecas, northern San Luis Potosi, and southern Nuevo Leon. More specifically, in southeastern Chihuahua from the vicinity of Escobillas, west to the eastern valley of the Rio Conchos, south to the vicinity of Ciudad Camargo, Bufalo, and Salaices; to the vicinity of La Zarca in northeastern Durango, and southeast to the vicinity of Casco and to a place 10 miles southwest of Yerbanis in east central Durango; in northwestern Coahuila from the southern valley of the Rio Grande in the vicinity of Boquillas, south to the vicinity of ‘Tanque Alvarez, and Ocampo, and southeast to the eastern border of the state; in northeastern Zacatecas to the vicinity of San Tiburcio; southeast to the vicinity of Matehuala in northeastern San Luis Poto- si; and to Doctor Arroyo in southern Nueyo Leon. Except in the northwestern part, limits of the range are not well known, and more collecting along the periphery of the range is needed to establish its extent and limits. Diagnosis. Size: Small; adult total length 302.0 to 325.0 mm; tail length 176.0 to 196.0 mm; body length 118.0 to 134.0 mm; hind foot length 42.0 to 49.0 mm; ear length 14.0 to 16.5 mm; distal white of tail short, 6.0 to 19.9 mm. Color: In general, Light Ochraceous-Buff to grizzled buff, purest on sides, thinly mixed with black-tipped hairs on dorsum, especially over top of head, back and rump; arietiform markings dusky; anterior ear fold dusky; large spot behind ankle blackish; plantar stripes light brown to dark brown; tuft of hairs at base of tail ventrally grayish black; dorsal and ventral tail stripes dusky; subterminal band of tail dusky to black and sometimes tufted. Skull: Small-sized; greatest length 41.5 to 43.2 mm; basal length 29.7 to 32.0 mm; nasals short, 14.8 to 15.4 mm; maxillary arch rela- SUBSPECIES OF Dipodomys spectabilis 57 tively heavy and not flared; breadth across maxillary arches 22.2 to 24.4 mm; auditory bullae relatively large; greatest breadth across bullae 26.3 to 27.6 mm; supraoccipital and interparietal usually small; external opening of auditory meatus usually oval; incisors narrow; mandibular length small, 17.1 to 18.5 mm. Also see Table 6. Comparisons. For comparisons with Dipodomys spectabilis specta- bilis, D. s. zygomaticus, and D. s. cratodon, see accounts of those sub- species (pp. 31, 49, 53). Remarks. Typical Dipodomys spectabilis nelsoni is characterized by Light Ochraceous-Buff to grizzled buff color on the dorsum, small ex- ternal size, and a short white tip of the tail. The skull is small, the maxillary arches are not flared, and the auditory bullae are small. Merriam (1907:75) described the species “D. nelsoni” as “Similar to spectabilis in general form and massiveness of skull but much smaller . . . mastoids actually nearly as large—relatively larger—than spectabilis; . . . white tip of tail shorter (20 mm) or absent all to- gether.” Generally, the white tip of the tail is short (the shortest measured is 3 mm), but it is never absent (unless it is broken). When this white end of the tail is short, it is usually covered with the long blackish fur of the subterminal dark band of the tail and thus not readily seen. Since Merriam’s description of nelsoni, several investigators—Dal- quest (1953:119); Baker (1956:246); and Anderson (1972:313), to name three—have studied the relationship between “D. nelsoni” and D. spectabilis and have arrived at similar conclusions. They maintain that the two forms are closely related, but there is no evidence of in- tergradation between them and they do not overlap in their ranges. Thus nelsoni has retained its specific status. However, Baker and Greer (1962:101) , commenting on nelsoni in Durango, stated that “there is indication that some contact between the two species has occurred in extreme north central Durango, possibly resulting in hybridization.” The geographic range of D. s. nelsoni complements the ranges of the other subspecies of D. spectabilis (Figs. 2 and 6). No conclusive evidence is yet available to indicate that specimens with the characters of these two taxa were collected from the same place. Four of five specimens in the U. S. National Museum labeled as Santa Rosalia [=Ciudad Camargo] are D. s. zygomaticus and the fifth one is D. s. nelsoni. Three of the four zygomaticus and the specimen of nelsoni were collected by E. W. Nelson between 17 and 26 September 1893. In 58 KANGAROO RATS his field notes, Nelson wrote about his field number 5482 (the nelsoni specimen) as being found only on the mesa land back from the river. It is not known on what side of the river this specimen was col- lected, and whether the specimens of zygomaticus were collected at the same place or not. Goldman (1951:124) reported that all the work in Santa Rosalia during the aforementioned period was done within a radius of three miles, mainly along the sides of the river bottom and adjacent mesa above town. The subspecies of D. spectabilis closest to the range of nelsoni is zygomaticus. Material recently collected from critical localities by the Museum of Natural History, University of Kansas, from south central Chihuahua, brings the range of D. s. zygomaticus to approximately 2 miles from that of D. s. nelsoni (zygomaticus from 19.5 mi WSW Jiménez; nelsoni from 1 mi § Salaices, Chihuahua). This and other material obtained by The Museum, Michigan State University, from north central Durango, show strong evidence of intergradation. The zone of intergradation between D. s. zygomaticus and D. s. nel- soni 1s a secondary one. This is evident by its narrowness and by the steep slope of the character gradient. In general, specimens of D. s. zygomaticus become smaller in all measurements as they approach the zone of contact, and along this zone they are extremely variable. With- in one sample there are specimens typical of zygomaticus and others which are distinctly smaller, and, in this respect, closer to nelsoni. Specimens of D. s. zygomaticus in this area show a pronounced ten- dency to resemble D. s. nelsoni in color, in having a shorter white tip of the tail, and in having smaller external and cranial measurements than typical zygomaticus. This is more prominent among specimens from the localities closest to the range of nelsoni (1 mi S Bufalo; 19.5 mi WSW Jiménez, Chihuahua) and also among specimens from 12 mi WSW La Resolana, Durango. Most specimens of D. s. zygomaticus from the zone of contact have parallel jugals and are thus not typical of this subspecies. Specimens of D. s. nelsoni, in this zone of contact, seem to be more conservative in the shift of the characters, and the change is less than in D. s. zygomaticus. Nevertheless, these specimens and others from nearby localities show a tendency to resemble D. s. zygomaticus in color, and in being larger in external and in cranial measurements, at least in some specimens. This is well illustrated in specimens from 1 mi S Salaices (the closest locality to the range of zygomaticus) . Of the 20 measurements taken, 19 of them in the zone of intergrada- tion show overlap of varying degrees (Fig. 9). The only measurement that does not show any overlap is the breadth across the maxillary ‘osuring [eU09 You pure enyenylyy [kNUI) YINOS UL UONLpLISIIIUL JO 9UOZ IYI WOT] (S9UT] PITOS) zwos7au *s “q pu (sauT, Udyo1q) SNIIPVUWOBAZ “8 “(J JO suauads yupe jo syuUoWMIINsSeIUT TRTUPID UIdJINOF pue HLON37 YVINSIGNYN oz 61 ga Zl STWWLIdlIO90X3 SSONOV HLAV3yNSs vl £1 él Se nr | MOYHLOOL “ONVW JO HLON3D ‘'AIV : ¢ : —— ey, ee ee ee ee ee 4 H1ld3q yv1ing 91 $| LA €l : : Le Sa ee ee ee J HLOVAYS IWelSOY H1OV3YS IWLISYONSLNI 1SV37 a) GI €! HLOVSYE AYVTTIIXVW 92 92 bz 22 HLONIT IVSUN dl Gl €l HLON31 1VSVa ve ee oe ‘SIYSIOM ‘s}UIWIINsvaUT [LUIIIXI AY UIIMIAq dvpsdAO IWaUYT “6 ‘SL LHOISM Oe! foxey| 08 Le-—---— -—-— ~~ — ~~ 4 HLONI 17 YV3 8! S| All ° e ° t---—-J4 HLONAT LOO4 GNIH Ss os Sb 60 KANGAROO RATS arches. There is, however, a clear indication that this character in D. s. zygomaticus does become smaller in the zone of intergradation. In my opinion, this difference is not important, for there is only a 0.5-mm break between the two measurements. The bullar index for all the adults from this zone is 1.184 for nelsoni and 1.107 for zygomaticus. This difference between the two indices is small. Intensive collecting in this zone of intergradation almost certainly will yield specimens exhibiting overlap in maxillary breadth, and a still greater degree of overlap in the other characters. In his discussion of the relationship between D. spectabilis and D. nelsoni, Stock (1974:523) indicated that both species have a karyotype with a diploid count of 72. He also stated that the subspecies of D. spectabilis difter from each other in the same way that they differ from D. nelsoni, but to a lesser degree. These conclusions strongly support my argument in regarding D. nelsoni as a subspecies of D. spectabilis. Unfortunately, Stock did not have samples of the southern subspecies of D. spectabilis. If he had had karyotypes of specimens of D. s. zygo- maticus to compare with D. nelsoni, he might have noted an even closer relationship between these two. Specimens from the western part of the range of D. s. nelsoni in east- ern Durango are larger than typical nelsoni. Although D. s. nelsoni is presently not known to be in contact with D. s. cratodon, specimens from northern San Luis Potosi and southern Nuevo Leon are larger than typical nelsoni. Also, as noted in Remarks under D. s. cratodon, specimens of this subspecies from southeastern Zacatecas and north- western San Luis Potosi are slightly smaller in many characters than the typical. This small size in specimens of cratodon in this part of its range, and the large size in specimens of nelsoni in northern San Luis Potosi and southern Nuevo Leon may suggest intergradation between these two forms. D. s. nelsoni is found in a variety of habitats and at a wide range of elevations. The animal seems to be best adapted to open desert habitat from elevations as low as 1,800 feet in the vicinity of Boquilla in north- western Coahuila, up to 3,500 feet in the vicinity of Ocampo in cen- tral Coahuila. It also is found in mixed grassland and thorn shrubs along the periphery of the range, at least in eastern Durango in the vicinity of La Zarca at 6,650 feet elevation. Nevertheless, D. s. nelsoni and D. s. zygomaticus inhabit similar areas along the periphery of their ranges in south central Chihuahua and north central Durango. Also, nelsoni is found in a transitional area between desert and grassland in east central Durango (Baker and Greer, 1962:100). This habitat is similar to that in which D. s. spectabilis occurs. SUBSPECIES OF Dipodomys spectabilis 61 On the basis of the above mentioned data, nelsoni is regarded as a subspecies of D. spectabilis. The zone of secondary intergradation shows the highest degree of concordance in the characters examined, and D. s. nelsoni is the most distinct subspecies of D. spectabilis. It is probable that D. s. nelsoni became isolated sometime before the isolation of D. s. cratodon. This latter race inhabits habitat similar to that of subspecies found in Arizona, New Mexico, western ‘Texas, and Chihuahua and probably very little change has occurred in the habitat since cratodon was isolated. D. s. nelsoni is found in a somewhat dif- ferent habitat, and because of the length of the period of isolation and differences in the habitat, the morphological differentiation of this subspecies is greater than that of D. s. cratodon. The long isolation of nelsoni has brought enough morphological differentiation to achieve nearly specific status. The contact between D. s. nelsoni and D. s. zygomaticus seems to be relatively recent in the evolutionary and dis- tributional histories of the species. The range of D. s. nelsoni occurs in only the eastern part of Duran- go as far as the eastern slopes of the Sierra Madre Occidental and does not extend westward beyond the eastern valley of the Rio Oro in the north central part of that state. The Rio Grande seems to be an effec- tive barrier for D. s. nelsoni inasmuch as it is not present in the north- ern valley of the river in south central Texas. Although the habitats on the two sides of the river in this region are similar, it is unlikely that future collecting on the northern side of the river will yield speci- mens of D. s. nelsoni. The range of this subspecies most probably will not extend much farther to the northeast of Coahuila because of the presence of the Sierra del Carmen and the Sierra Madre Oriental. Fu- ture collecting may reveal a wider distribution in northern Zacatecas and northern San Luis Potosi. Five specimens of D. s. nelsoni from two localities in Zacatecas rep- resent the first records for that state. Specimens examined. A total of 227 specimens from: CHIHUAHUA. 8 mi NNW Escobillas, 5,000 ft, 4 (ku); 1 mi E Julimes, 8 (Ku); 3 mi E Julimes, 3,850 ft, 1 (ku); 4 mi E Julimes, 3,850 ft, 1 (ku); 1 mi W San Francisco, 4,325 ft, 1 (ku); 2 mi N, 6 mi E Camargo, 4,150 ft, 3 (ku); 1 mi N, 3 mi E Camargo, 4,150 ft, 2 (ku); Santa Rosalia [=Ciudad Camargo], | (usNM) ; Sierra Almagre, 12 mi S Jaco, 5,300-6,000 ft, 10 (ku) ; Sierra Almagre, SW slope, 19 mi S, 4 mi E Jaco, 5,500 ft, 11 (Ku) ; 23 mi ESE Boquilla, 4,700 ft [about 4 mi E Bufalo], 4 (ku); 23.5 mi ESE Boquilla, 4,700 ft, 2 (ku); 9 mi N Jiménez, 2 (ku); 2 mi W Jiménez, 4,700 ft, 1 (ku); 5 km S Jiménez, TABLE 6 Measurements (in mm) of adult specimens from type-localities or near type-localities of the different subspecies of Dipodomys spectabilis. (Mean with sample size as superscript and range below) spectabilis perblandus intermedius Character 346,19 26 46,499 444,399 Total length 347.84 326.65 325.06 340.0 — 353.0 315.0 — 335.0 314.0 — 330.0 Tail length 203.34 193.6° 186.76 199.0 — 206.0 184.0 — 204.0 180.0 — 195.0 Hind foot length 52.34 48.36 47.47 51.0— 53.0 47.0 — 50.0 46.0 — 49.0 Ear length 16.84 — 16.67 16.0— 17.0 16.0— 17.0 Body length 144.54 1335.26 137.47 141.0 — 149.0 130.0 — 138.0 130.0 — 146.0 Greatest skull 45.94 44.46 43.08 length 44.0— 46.8 43.0— 45.3 42.1— 44.2 Basal skull length 33.34 31.85 31.04 32.0— 34.2 s16— 32.1 30.5— 318 Length of nasals 17.14 16.16 15.87 16.7— 17.5 15.0— 16.8 15.2— 168 Breadth across 26.34 25.74 25.07 maxillary arches 25.8— 26.6 25:3. 29.9 Ee = 258 5 Least interorbital 15.94 14.64 14.87 breadth 15.7— 16.3 140— 15.3 14.1— 15.3 Greatest breadth 29.44 28.16 27.34 across bullae 28.3— 30.2 27.7 — 28.6 27.2— 28.7 Rostral breadth 4.64 4.66 4.37 44— 4.8 4.3— 4.7 41— 44 Rostral depth 8.84 8.56 8.47 85— 9.0 8.3—= (8.7 8.2— 8.6 Bullar depth 15.44 14.86 14.66 149— 15.9 14.5— 15.1 14.2— 15.2 Alveolar length 6.54 5.96 5.97 maxillary toothrow 6.1— 6.8 56— 6.2 53— 6.3 Least breadth 1.74 2.16 1.95 supraoccipital 15— 2.0 19— 2.5 14— 2.2 Breadth across 15.18 13.66 13.14 exoccipitals 14.7 — 15.7 12.8— 14.2 12.7— 13.4 Alveolar length man- 6.14 5.86 5.67 dibular toothrow 5.8— 6.3 5.5— 6.2 5.3— 6.1 Mandibular length 19.74 18.76 18.07 18.6— 20.2 18.5— 19.1 17.3— 18.5 Length white tip 40.84 23.05 20.07 of tail 37.0— 46.0 16.0— 30.0 13.0— 25.0 Weight, grams — — 98.77 94.8 — 105.7 spectabilis: 19 mi W, 2 mi N Willcox, Cochise County, Arizona perblandus: Calabasas, Santa Cruz County, Arizona intermedius: 16.7 mi SW Bamori, Sonora baileyi zygomaticus cratodon nelsoni 636,799 384,19 586, 429 11g ¢, 399 354.611 341.54 337.08 319.218 340.0 — 373.0 334.0 — 352.0 320.0 — 358.0 303.0 — 334.0 205.411 201.64 209.08 197.718 191 O== 221.0 195.0 — 212.0 195.0 — 226.0 180.0 — 211.0 55.012 52.34 525° 48.514 53.0— 56.0 49.0— 54.0 51.0— 54.0 46.0— 51.5 13.112 — — _ 120— 14.0 150.112 139.94 128.28 121.114 142.0 — 164.0 138.0 — 143.0 117.0 — 133.0 108.0 — 132.0 47.012 45.74 45.49 42.314 45.5 — 48.7 45.0 — 46.2 43.4— 47.0 40.6— 43.5 34.610 34.14 34.19 31.114 33.8— 35:7 33.4— 343 se 3D.0 29.6— 32.0 17.0138 16.14 16.29 14.914 16.1— 17.7 15.8— 16.5 Ib2— 17.1 142 155 26.912 26.93 26.98 23.018 25.6-— 28.5 26.0— 27.6 259 == 28.5 22.2 == 257 15.313 16.12 16.07 14,511 14.8— 16.3 15.7/-—— 16.4 15.3— 17.0 14.0— 15.3 29,710 30.34 29.59 26.814 28.8— 31.4 29.4-— 530.9 28.4— 30.5 25.4 = 2h9 5,018 5.04 4.69 4.218 $5—— 55 48— 5.3 44—— 50 3.7— 4.7 9.213 9.14 9.19 7.914 89— 9.6 8.9— 9.4 8.7— 9.4 76— 82 15.710 15.34 15.59 14.514 15.1— 16.9 149== 156 15:2 16.0 13.8— 15.1 6.618 6.64 6.79 6.014 6.0— 7.0 6.4— 6.7 64— 69 5.3— 68 2.213 2.04 1.49 1.414 Lo3— 26 Lp 22 09— 17 10— 18 14.410 14.33 14.49 13.012 bj. 152 13.8— 15.0 13.4— 16.0 12.2— 14.1 6.218 6.04 6.39 5.714 5 — 67 Boa “6 6.1— 65 54— 6.0 20.418 19.84 20.69 17,714 19.5 -—. 214 19.3— 20.4 19.3—- 21-9 17.1— 184 30.0138 22.84 19.88 11.611 240— 40.0 18.0 — 29.0 12.0— 24.0 4.0— 20.0 146.213 _ = = 128.9 — 164.3 baileyi: 44 mi NW Roswell, Lincoln County, New Mexico zygomaticus: Parral, Chihuahua cratodon: Chicalote, Aguascalientes nelsoni: La Ventura, Coahuila 64 KANGAROO RATS 4 (ku); 10 mi WSW Jiménez, 4,800 ft, 2 (ku) ; 11.5 mi WSW Jiménez, 4,800 ft, 2 (kU) ; 12.5 mi SW Jiménez, 5,000 ft, 3 (KU) ; 14.5 mi WSW Jiménez, 5,000 ft, 4 (ku); 1 mi S Salaices, 4,900 ft, 21 (KU) ; 6.9 mi NE Escalon, | (v1) ; Escalon, 60 km SE Jiménez, 2 (ku), 10 (USNM). DURANGO. 6 mi E Zavalza, 4,150 ft, 3 (msu); 7 mi NW Yermo, 3,900 ft, 1 (mMsu) ; 7 mi NNW La Zarca, 6,000 ft, 1 (msu) ; 12 mi E La Zarca, 6,000 ft, 4 (KU); 14 mi E Zarca, 6,650 ft, 1 (vz); 35 mi W Mapimi, 5,500 ft, 3 (msu) ; 1 mi WSW Mapimi, 3,800 ft, 3 (KU); 4 mi SE Casco, 5,850 ft, 1 (msu); 2 mi NW Chocolate, 4,500 ft, 3 (Ku) ; 2 mi E Pedricena, 4,300 ft, 6 (KU), 1 (Msv). COAHUILA. 7 mi S, 2 mi E Boquillas, 1,800 ft, 2 (KU); 6 mi N, 2mi W Castillon, 3,750 ft, 1 (Ku); 2 mi SSE Castillon, 4,050 ft, 2 (KU) ; 11 mi N, 9 mi W Tanque Alvarez, 4,500 ft, 1 (KU); 2.5 mi SE Ocampo, 3,300+ ft, 1 (kU); 2.5 mi W, 21 mi S Ocampo, 3,500 ft, 4 (kU) ; 4 mi N Acatita, 3,600 ft, 2 (kU) ; Trevino, 2 (usNM) ; 15 mi SSE Hda. Guadalupe [=Guadalupe], 3.200 ft, 1 (msu) ; Jaral, 11 (FMNH), ] (UCLA), 3 (USNM); 14 mi S San Antonio de Jaral [= Jaral], 4,400 ft, 6 (Mvz); 12 mi N, 10 mi E Parras [=Parras del Fuente], 5,000 ft, 1 (KU) ; La Pastora, 4 mi W, 15 mi N Saltillo, 1 (ku); 3 mi N, 5 mi W La Rosa, 3,600 ft, 3 (kU); Torreon, 1 (UsNM); 1 mi N San Lorenzo, 4,200 ft, 4 (ku); 4 mi NNW Saltillo, 5,200 ft, 4 (ku); N foot Sierra Guadalupe, 10 mi S, 5 mi W General Cepeda, 6,500 ft, 16 (KU); W foot, Pico de Jimulco, 4,600 ft, 1 (Ku); 7 mi S, 1 mi E Gomez Farias, 6,500 ft, 5 (Ku); San Juan Neponuceno, 5 mi La Ventura, 1 (Mvz) ; La Ventura, 18 (USNM). ZACATECAS. 3 mi N Lulu, 4 (mMvz); 1 mi SWS S/an] Tiburcio, 7,000 ft, 1 (KU). SAN LUIS POTOSI. 57 mi N Matehuala, 6,000 ft, 1 (AMNH) ; 11 mi NW Cedral, 1 (Mvz). NUEVO LEON. Doctor Arroyo, 2 (USNM). Additional records. CHIHUAHUA. (AIl from Anderson, 1972:313) “Pinon Camp” Sierra Rica, 4,900 ft, 1 (srsc); ‘Alluvial flat between camps’, 3,200 ft (E Sierra Rica), 2 (srsc) ; “29° 12’ N, 104° 06’ W”, 3,200 ft, 1 (sRsc) . DURANGO. 10 mi SW Yerbanis, 6,200 ft (Baker and Greer, 1962: 100) . COAHUILA. Near Cuatro Ciénegas (Gilmore, 1947:158) ; about 32 mi N Saltillo (Baker, 1956:244). SAN LUIS POTOSI. 3 km S Matehuala, 1 (Lsu, Dalquest, 1953:19) ; 6 km S Matehuala, 1 (Lsu, Dalquest, 1953:19). DIPODOMYS DESERTI Species Characteristics The desert kangaroo rat is the most specialized and one of the largest species of the genus Dipodomys, It is adapted to live in the lowest, hottest, and most arid regions of North American deserts. It has four toes on each hind foot, and the foot is covered with relatively long hairs. The color of the upper parts varies from Pale Buff to Ochraceous Buff mixed with a variable amount of long blackish hairs, depend- ing on the subspecies. The supraorbital and postauricular spots, hip stripes, fore limbs, dorsal surface and sides of hind feet, the ring at the base of the tail, including the ventral tuft, lateral tail stripes, ventral surface of the body, and the distal tip of the tail are pure white. The skull is large, with maximum inflation of the bullae for the genus (Fig. 10). The supraoccipital is so restricted dorsally as to be almost absent, and the interparietal is usually absent in adult specimens. The nasals are long and the rostrum is long and slender. The maxillary arches are not heavy or wide, and give the skull a triangular appear- ance. The jugals are divergent posteriorly. The molariform teeth are of the kleistodont type (Nader, 1966). External openings of the audi- tory meati are large and oval-shaped. The ectoglenoid fossa is absent. The mandibles are delicately built. The weight of adult males ranges from 91.0 to 148.0 grams, of adult females, from 82.8 to 141.2 grams. The hyoid apparatus of Dipodomys deserti consists of only two parts, as in D. spectabilis, a basihyal and a reduced thyrohyal. The basihyal is large with a low ventral ridge. The anteromedial border of the “shoulders” is more or less pointed. The basihyal arch is usually deep. The thyrohyal is large. Secondary sexual dimorphism is evident in this structure. This large kangaroo rat primarily inhabits the Lower Sonoran Life- zone, but it also invades the salt-desert area (Hall, 1946:34) of the ‘vuozly ‘AjUNOD vuInx ‘UOIIULOS AS "ur g uloly 2 B/G/T “ON IQ ‘T[NYS 274aSap isasap s§ (wopodiq JO smara [PNUIA PUL [esIOg ‘OL “BIy [eI]U9A Jesiop Dipodomys deserti 67 Fig. 11. Beaver Dam Wash, at Terry’s Ranch, 7 mi N Utah-Arizona border, Washington County, Utah. Typical habitat of Dipodomys deserti desertt. Upper Sonoran Life-zone in northwestern Nevada. It is restricted al- most exclusively to the loose sandy parts of the desert with scattered creosote bush, Larrea sp. and mesquite, Prosopis sp. (Fig. 11) . In only one case was D. deserti found in gravelly soil and that was in the vicin- ity of Florence in central Arizona (see Remarks under D. d. arizonae, p. 94). This species is well adapted to a wide range of elevations with- in its geographic limits. It inhabits the desert depressions as low as —200 feet at Salt Creek, Inyo County, in the Death Valley National Monument, California. It was collected at elevations as high as 5,700 feet in the Huntoon Valley, Mineral County, Nevada. Other kangaroo rats that occur sympatrically with Dipodomys de- serti are D. merriami, D. ordii, D. panamintinus, and D. microps. Its size, coloration, and skull features make D. deserti readily distinguish- able from all of these other kangaroo rats. Little is known about the longevity of this rodent. The only avail- able record is that of Brattstrom (1960:404) who reported a captive D. d. deserti living for five years and five months. An adult D. d. arv- zonae was live-trapped on 3 February 1961 and kept in captivity at the Museum of Natural History, University of Illinois, until it died on 26 September 1969, having lived in captivity for 7 years and about 8 68 KANGAROO RATS months. Since this animal was adult when captured, it lived at least 814 to 9 years. This is the longest record of longevity for the desert kangaroo rat and, to my knowledge, it is the longest record for the genus. Lidicker (1960:136) reported a Merriam’s kangaroo rat living at least 714 to 8 years. Records of predators of D. deserti are scarce, and this species seems to be successful in avoiding its natural enemies. The kit fox, Vulpes macrotis, owls, and snakes may be among its predators. Grinnell et al. (1937:417) concluded that kangaroo rats constitute the main food of the kit fox in the soft sand areas of California where D. deserti lives. McAtee (1921:258) reported that in 592 pellets of the barn owl, Tyto alba, collected in California, remains of 230 kangaroo rats were found in addition to other rodents, but no mention was made of the kinds of kangaroo rats involved. Records of ectoparasites and endoparasites are seemingly very few. D. deserti is known to be host for two species of fleas, Meringis parkevi, and Thrassis (Thrassoides) hoffmani (Hubbard, 1961:135) and one species of sucking louse, Fahrenholzia pinnata (Ferris, 1922:160). No record of endoparasites was found. As with D. spectabilis, all specimens examined were checked for molting and notes on molting patterns were taken. The number of molting specimens was noticeably small. Although at least one speci- men was molting in each month, with the exception of November and December (Table 7) , there seems to be only one adult molt per year, occurring in the spring and the summer, with a peak in July. These data show that the time of molt is in disagreement with the findings of Grinnell (1922:107) who stated that molt in D. deserti takes place in the fall. REPRODUCTION Knowledge of the reproductive activity in the desert kangaroo rat is TABLE 7 Number of molting individuals of Dipodomys deserti (by age-groups and month of capture) Month of capture Age-Group J F M A M J Jj A S O N D Juvenile —- — -5 —- 4 6 Immature = 1 — 3 + 4 4 2 1 — a — Subadult — 1 _ 3 4 3 1 2 Adult 8 — 1 — 4 7 17 +4 1 1 — -= Dipodomys desertt 69 TABLE 8 Distribution of recorded reproductive activity in females of Dipodomys desertt_ by age-groups Immature Subadult Adult Total Number of females examined 5 23 77 105 Females showing reproductive activity 2 10 48 60 meager. Of 105 females examined for pregnancy or lactation, 60 (57.1%) showed signs of such activities (Table 8). Sexual maturity begins early in the life of this species. In five immature females, one was lactating and another had four embryos; among 23 subadults, 10 were pregnant. Reproductive activity starts early in January and continues through the first half of July. The first recorded pregnancy is on 18 January (3 embryos x 30 mm) and the latest reproductive activity is a lactat- ing female on 10 July, with pregnancies in every month between (Fig. 12A). No differences in the time of pregnancy between the northern and the southern populations were detectable. The month of February has the largest number of pregnant females and the largest number of young born, judged from the number of embryos (Fig. 12 A and B). All the females examined in this month were pregnant. The breeding period is relatively long, spreading over seven months, from January to July. Two peaks are recognized within the breeding period, in February and in May (Fig. 12A). This leads to the assump- tion that two litters are produced in the year, but no final conclusion can be made until further study is done in this respect. The number of embryos per litter ranges from one to six (Fig. 12C). In 48 pregnant females the number of embryos was 165, with a mean of 3.43 embryos per female and a mode of 3. Butterworth (1961b:414) reported similar figures from a captive pair. The female produced 23 young in seven litters with a mean of 3.29 young per litter and a mode of 3. Butterworth also reported that the gestation period varies be- tween 29 and 32 days. The lengthening of the gestation period in D. deserti (one of the longest in the genus) reflects a unique adaptation to produce well-developed young that survive the severe conditions of the desert habitat. A newborn is about 52 mm in total length (Butter- worth, 1961a:134) . Little is known about growth and development of the desert kan- garoo rat. Butterworth (196la) reports that the incisors erupt between 7 and 10 days after birth, weaning occurs between 15 and 25 days, EzIS JOU] JO UOIN!yS!p Aouanbel4 9G vez ~ oOoOroanann fo) 0 NUMBER OF FEMALES 02 ‘uyaasap skwopodig ut AWAnoV dANONpoiday “Zl “Sty yjuoW Jed SsoAiquua JO JAGUWNN GQNOSVPfrfWVWd Pe 9€ Lad d NUMBER OF EMBRYOS yjuoW Jad AjyIAOe aAonpojdes Hulmous sejewa JO (UWUN|OO Yyoea sAOqe) abejusoied pue JaquinN ‘Vv QNOSVFPAVWAS ES Oger nOon — FEMALES (°) o NUMBER OF Dipodomys deserti 71 adult size is attained at about 90 days and very little growth takes place after that; 91% of weight is attained in 90 days, and an average adult weight in 150 to 180 days. COLOR In Dipodomys deserti the color of the upper parts varies from pale fawn to grayish black, depending on the subspecies. In the zone of inter- gradation between the different subspecies, there are all degrees of color gradients. Within a given subspecies, color is usually stable except in D. d. deserti where it varies from Pale Buff to Ochraceous Buff thinly mixed with long dusky colored hairs (see Remarks under this subspecies, p. 86). Color, in general, is a useful taxonomic crite- rion; however, color variations may be present within one subspecies —as in D. d. deserti—and in this case cranial characters are relied on almost exclusively for diagnosis. The subspecies of D. deserti do not exhibit any noticeable variation in the white supraorbital and postauricular spots, hip stripe, venter, forefeet, dorsal surface and sides of the hind feet, ring at the base of the tail, and the lateral tail stripes. Occasionally the supraorbital and postauricular spots are not too distinct in D. d. deserti from California and are more distinct and usually larger in D. d. arizonae. Although the distal white of the tail is quite variable within most of the samples, it is usually short in D. d. deserti, longer in D. d. arizonae, and longest in D. d. sonoriensis. There are noticeable differences in the extent of the color of the arietiform markings between the subspecies. In D. d. deserti, this marking ranges from nearly obliterated to a pale buffy line, while in D. d. arizonae, D. d. sonoriensis, and D. d. aquilus it is dusky to blackish. The color of the orbital ring follows almost the same pattern as that of the arietiform markings. The outer surface of the ear is similar in color to the upper parts. The plantar stripe also shows some variation in color. In D. d. de- serti it ranges from absent to light brownish which is usually restricted to the heel region, while in the other subspecies it is most frequently brownish or blackish. A yellow or yellowish shade is sometimes present on the ventral side of the toes. The dorsal tail stripe and the subter- minal dark band of the tail vary, in general, according to the color of the pelage. It is buffy or dusky in D. d. deserti and blackish mixed with gray in the other subspecies. The ventral tail stripe is ordinarily absent in D. d. deserti but, when present, it is pale-colored and broken. It is usually present in D. d. sonoriensis and D. d. aquilus, and always present in D. d. arizonae, where it is dark and most often continuous. 72 KANGAROO RATS The color of the pelage of D. desert seems to be correlated with the color of the soil. Pale-colored populations are found in the central part of the range in the Mojave, Colorado, and Yuma deserts, where the soils of the desert are mostly pale or buff in color (Dice, 1939:120) . The color of the specimens in the northwestern populations (in NW Nevada) is dark and so is the color of the soil. The palest-colored in- dividuals are found in Death Valley, California, where the hottest and the driest conditions occur within the range of the species. High alka- linity of the soil affects the color in D. d. deserti, and the upper parts become more yellowish than usual; the plantar stripes, the distal white of the tail, and in extreme cases, the circumanal ring are altered in color. The original color is restored after molting. Such altered colora- tion was found among specimens from Keeler and from several locali- ties within Death Valley National Monument, California, and in some specimens from southern Nevada, especially Thorpes Mill in Nye County. The ochraceous color of the populations in southwestern Arizona and northwestern Sonora is not likely to have been caused by the alkalinity of the soil, as most of these specimens have fresh pelages. Several specimens of D. d. deserti, especially in California and south- ern Nevada, have one or more buffy spots on the ventral side. Similar spots were not seen in the other subspecies. It is not known whether these spots are genetically controlled or adventitious. Age Variation Four age-groups were distinguishable for Dipodomys deserti. ‘These are established on the same basis as for D. spectabilis. Juvenile. Deciduous PM4,pm4 are present and show some or con- siderable wear. M1-2,m1-2 show some wear. M3,m3 are either just erupted or not erupted yet, and may show slight wear in older juve- niles (Fig. 13; a, a’, b, b’). M3 usually shows more wear than m3. ‘The skull is fragile and its dorsal surface convex. The auditory bullae are opaque and rough. The interparietal is wide and the supraoccipital is evident in its whole length. Immature. Deciduous PM4,pm4 have just been shed. In older im- matures, the permanent PM4,pm4 and M3,m3 show slight wear while M1-2.m1-2 have more wear (Fig. 13; c, c’). At the end of this stage, any one of the teeth still shows evidence of enamel infoldings. The skull is, in most cases, convex, the bullae are still opaque and rough and the interparietal is long and narrow. a-e = right maxillary toothrow Juvenile No. 17572 9 6 mi SE Somerton, Yuma County, Arizona Immature No. 9299 12¥2 mi S Yuma, Yuma County, Juvenile No. 9305 2 12V2 mi S Yuma, Yuma County, Arizona Subadult ES No. 24327 2 Saratoga Springs, San Bernardino d Arizona County, California C d’ Cc Adult No. 23023 ¢ 4miS and 1 mi E Picacho, Pinal County, Arizona e e Fig. 13. Occlusal views of molariform teeth of different age groups of Dipod- omys desertt. All specimens from UI Collection, 74 KANGAROO RATS Subadult. All teeth show some wear. All molariform teeth except M3 and pm4 are almost oval in shape (Fig. 13; d, d’). M3 is usually pentagonal in shape with its apex directed posteriorly, while pm4 has two enamel intoldings, a deep lingual and a shallow labial. Enamel breaks develop in this stage and in some subadults all the teeth have them. The skull is slightly convex and the bullae are still rough and porous. The interparietal is usually absent and the supraoccipital is narrow. Adult. All teeth show considerable wear (Fig. 13; e, e’). Enamel breaks are usually present in all teeth. The dorsal surface of the skull is flat and the bullae are shiny and translucent. The supraoccipital is narrow and in most cases is so restricted dorsally as to be absent. The tur in the young individual is usually short and has more gray- ish color than that of the adult. The tail is covered with short hairs over its entire length. The dorsal and ventral tail stripes and the dark subterminal band of the tail are darker in young animals. DENTITION The sequence of tooth eruption in D. deserti is, in general, similar to that of D. spectabilis. In the youngest D. deserti examined, ur No. 17572 9, the deciduous PM4 has an anterior cusp, a protoloph, and a metaloph (Fig. 13 a). The two cusps of the protoloph are distinct, but none of the cusps of the metaloph is distinct. After some wear the two cusps of the protoloph unite with each other, then with the anterior cusp (Fig. 13 b). The protoloph later unites with the metaloph lin- gually, leaving a deep labial enamel infolding. The elongated decidu- ous pm4 has an anterior cusp, a protolophid, and a metalophid. ‘The two cusps of the protolophid are distinct, but none of the cusps of the metalophid is evident (Fig. 13 b’). The anterior cusp unites first with the protolophid and later this unites with the metalophid at the mid- dle of the occlusal surface, leaving two labial and two lingual enamel infoldings. When the occlusal surfaces of the deciduous PM4, pm4 are worn smooth, PM4 will have an almost triangular shape with its apex directed anteriorly and with no enamel infoldings, and pm4 will have a rounded anterior end and an almost straight posterior one. ‘The two lophs of the permanent PM4 unite labially, leaving a deep lingual enamel infolding; while the two lophids of the permanent pm4 unite in the middle, leaving two deep enamel infoldings, one lingual and one labial (Fig. 13; c, c’). The protoloph and metaloph of M1-3 unite lingually leaving a deep labial enamel infolding (Fig. 13b). More- Dipodomys deserti 75 over, in M3 there is a small indentation on the lingual side. The pro- tolophid and metalophid of m1-3 unite in the middle of the tooth forming an H pattern and leaving deep labial and shallow lingual enamel infoldings (Fig. 13; b’, c’). In D. desert: in the immature age- group, the labial infoldings in the upper molars disappear in succes- sion from the first to third molar. In the lower molars, the lingual infoldings disappear before the labial ones. The labial infoldings dis- appear in the same age-group and in the same sequence as in the upper molars. All molariform teeth in the subadults are almost oval in shape ex- cept M3 and pm4 (Fig. 13; d, d’). The former is usually pentagonal in shape with its apex directed posteriorly while pm4 is squarish, but indented laterally on both sides because of the two enamel infoldings. These infoldings usually disappear in old adults, or become quite shallow. Enamel breaks develop early in this species. ‘They develop in the subadult age-group, and in some old subadults all teeth have them. The sequence of the development of the enamel breaks is as follows: They develop first in M1-2,m1-2; then in the premolars, in PM4 before pm4; the last teeth to develop enamel breaks are the third molars where they develop in m3 before M3. In old subadults all molariform teeth may have enamel breaks. These enamel breaks develop some- times on the lingual side first, or on both sides at the same time. In pm4 of some old adults, two additional enamel breaks develop antero- laterally, one on each side. Enamel breaks disappear in some teeth in some old adults. No groove in the anterior face of the lower incisors was found in any specimen. Individual Variation To analyze the individual variation in Dipodomys deserti, a grouped locality was formed from the southwestern corner of Yuma County, Arizona. This locality included specimens from: 7 mi S Yuma; 12 mi S Yuma; 6 mi SE Somerton; 5 mi ESE Somerton; 10 mi E and 4 mi S Yuma; and 3 mi E Somerton. A total of 32 adults, 18 males and 14 females was examined. As in D. spectabilis, the 20 measurements studied in this species show normal variability except the least supraoccipital breadth and the distal white of the tail (Table 9). The greater inflation of the bullae in D. deserti reduces even more the size of the supraoccipital 76 KANGAROO RATS "TABLE 9 Coefficients of variation within a grouped locality of Dipodomys desertt, vicinity of Yuma, Yuma County. Arizona (Superscript for number of specimens) Character 18g ¢ 1499 Total length 5.50 3.69 Tail length 7.00 4.50 Hind foot length 3.55 2.88 Ear length 5.6017 6.89 Body length 4.95 4.35 Greatest skull length 2.8011 1.9715 Basal skull length 3.1512 2.2712 Length of nasals 4.2517 2.15 Breadth across maxillary arches 3.9417 3.24 Least interorbital breadth 4.6110 2.6710 Greatest breadth across bullae 2.6215 2.5318 Rostral breadth 5.23 3.25 Rostral depth 4.06 4.19 Bullar depth 2.7612 1.8718 Alveolar length of maxillary toothrow 3.48 4.34 Least breadth supraoccipital 124.9216 83.1518 Breadth across exoccipitals 3.3811 5.2611 Alveolar length of mandibular toothrow 4.65 3.57 Mandibular length 2.76 1.68 Length of white tip of tail 48.34 30.1218 and the interparietal, in comparison with D. spectabilis. The inter- parietal is usually absent in adult specimens and, when present, only a smal] part, its anterior end, is evident between the reduced arms of the supraoccipital. The supraoccipital dorsally appears to be absent but may remain as a narrow, splintlike bone that may widen out slightly at its anterior end. As was indicated under Materials and Methods, the least supraoccipital breadth and the length of the white tip of the tail were not used in the analysis of the geographic variation. Again as in D. spectabilis, the external measurements are slightly more variable than the cranial measurements. Tail length and ear length vary the most. Rostral breadth, rostral depth, breadth across the exoccipitals, and alveolar length of the mandibular toothrow are more variable than other cranial measurements. The most variable measurement among them is the breadth across the exoccipitals. ‘The mean of the alveolar length of the maxillary toothrow was com- pared with that of the mandibular toothrow in both sexes. In both Dipodomys deserti fi cases the alveoli of the mandibular toothrow were slightly longer than those of the maxillary, but the differences were not significant. Secondary Sexual Dimorphism Males are generally larger than females. To analyze this secondary sexual dimorphism, the same grouped locality used in the analysis of the individual variation was employed. The means of the 18 measure- ments used in this analysis were larger for the males (Table 10). How- ever, only in the following measurements were the differences signifi- cant: Tail length, basal length, greatest length, breadth across the maxillary arches, least interorbital breadth, greatest breadth across the bullae, rostral depth, breadth across the exoccipitals, and the man- dibular length. Accordingly, these measurements were analyzed sepa- rately for males and females in the analysis of geographic variation. Geographical Variation Morphological variation among different populations of Dipodomys deserti throughout the range of the species is not great. Several factors may account for this. First, throughout its entire range, D. deserti in- habits an almost uniform terrain—loose sandy soil. Second, no geo- graphic barrier permits isolation and differentiation within the range of D. deserti. The only geographic feature which may represent a bar- rier is the Colorado River. This, however, does not seem to be an effective barrier, especially near its southern end where the river is shallow and its course has shifted back and forth several times in the past (Goldman, 1937:429). That populations along both sides of the river in its southern region are similar in most characters is a demon- stration of the ineffectiveness of the river as a barrier in this region. Although some of the populations present along the two sides of the river in west central Arizona and southeastern California exhibit slight differences in some of the measurements, these differences are irregu- lar and do not follow a uniform pattern. Third, it seems that D. de- serti has achieved a high degree of specialization for the type of habi- tat it occupies, and probably the future will bring little change in the morphology of this species. This assumption would be true only if there would be no major change in the habitat which D. deserti occu- pies at the present time, and provided that the limits of tolerance of this species are narrow. It is difficult to speculate about change in habitat, but the narrow limits of tolerance of this species is exhibited by its restriction to a specific type of habitat. 78 TABLE 10 KANGAROO RATS Comparison between adult male and adult female Dipodomys deserti, vicinity of Yuma, Yuma County, Arizona (Number of individuals, mean, range, one standard deviation, and one standard error of the mean. Measurements in mm) Character 183g e 149 9 Total length 342.87 327.92 (315.0-368.0) (307.0-347.0) 18.847 12.099 +4.443 +3.235 Tail length 201.43 189.92 (181.0-225.0) (177.0-205.0) 14.059 8.553 +3.314 +2287 Hind foot length 54.5 52.89 (52.0-58.0) (51.0-56.0) 1.925 1.522 +.454 +.406 Ear length 17.28 17.25 (15.0-19.0) (16.0-19.0) .969 1.188 “#255 +317 Body length 141.4 138.0 (132.5-156.0) (129.0-146.0) 7.001 6.0 +1.65 +1.603 Greatest skull length 46.12 44,7 (44.2-47.9) (43.3-46.4) 1.291 .88 ae .30 ate 245 Basal skull length 31.75 30.68 (30.0-33.2) (29.6-32.0) 1.002 .698 +.289 +.202 Length of nasals 17.4617 16.88 (16.4-18.6) (16.1-17.5) 742 464 +.18 124 Breadth across maxillary arches 23.9417 22.97 (22:2-25.7) (22.0-24.7) 943 743 3.229 +.198 Least interorbital breadth 14.4210 13.6210 (13.5-15.8) (13.1-14.4) 664 364 +.211 +.116 Dipodomys deserti Table 10 contd. 79 Character 184 ¢ 1499 Greatest breadth across bullae 30.515 29.5718 (28.9-31.6) (28.5-31.1) 80 747 +207 +.207 Rostral breadth 4.05 3.96 (3.8-4.5) (3.7-4.2) 212 128 +.05 +.034 Rostral depth 7.77 7.44 (7.2-8.2) (7.1-8.0) 315 311 +.074 +.083 Bullar depth 15.2312 14,9213 (14.6-16.0) (14.5-15.5) A2 219 +.121 +.078 Alveolar length of maxillary toothrow 6.26 6.11 (5.8-6.8) (5.5-6.5) 218 .265 +.052 +.07 Breadth across exoccipitals 13.2911 12.3511 (12.5-13.8) (11.5-13.5) 449 65 +.135 +.196 Alveolar length of mandibular 6.31 6.17 toothrow (6.0-7.1) (5.8-6.5) 1292 | +.068 +.058 Mandibular length 18.79 18.21 (17.8-19.7) (17.8-18.7) .163 306 +.038 +.082 Among the external measurements, the most variable, geographi- cally, are total length and body length; among the cranial measure- ments, greatest length, and greatest breadth across the bullae. The least variable measurements, geographically, are the length of hind foot, rostral width, breadth across maxillary arches, and basal length. As was stated earlier, males are usually larger than females in all the characters studied. The differences, however, are significant in only 9 of the 18 measurements compared, and morphological variations are 80 KANGAROO RATS more evident among males than among females. In several of the char- acters there is some evidence of clinal change from the northwestern part of the range of the species in northwestern Nevada to the south- eastern parts in south central Arizona and west central Sonora. Speci- mens from Nevada are smaller than those from Arizona and Sonora. Nasal length and rostral depth are among the characters that show evidence of clinal change. They are larger in the southeastern popu- Jations than in the central and northwestern ones. Rostral breadth, however, does not show much variation throughout the entire range of the species. It is thought that the lengthening of the nasals and deepening of the rostrum, which consequently enlarge the volume of the nasal passages, act as a cooling device for the air during inhalation, and, more important, during exhalation to help condense the moisture in the exhaled air. Condensation of water from the expired air would result in conserving considerable water which is exceedingly important for these animals, as they are not known to be dependent on free wa- ter in the wild. ‘Thus, the increase in the volume of the nasal passages appears to be directly correlated with an increase in temperature and a decrease in humidity. Setzer (1949:503) reported a reverse trend in D. ordi with regard to the length of nasals and the width of rostrum where they decreased as the southern limits of the range were ap: proached, and he suggested that this may be correlated with the mean annual relative humidity of the environment. SUBSPECIES OF DIPODOMYS DESERTI Dipodomys desertt deserti Stephens Dipodomys deserti Stephens, Am. Naturalist 21:42, January 1887, orig- inal description. Dipodomys deserti helleri Elliot, Field Columbian Museum, Publ. 87, Zool. Ser., 3:249, 7 January 1903, type: Male, adult skin and skull; No. 13007, Chicago Natural History Museum; from Keeler, Owens Lake, Inyo County, California; collected by E. Heller, 3 June 1903. Dipodomys deserti deserti: Miller, U. S. Natl. Museum Bull., 79:277, 31 December 1912. Type. Female, immature, skin and skull; No. 15629/22522, U. S. Biological Surveys Collection: from Mojave River, California [Mojave River bottom at “upper crossing” on old road from Cajon Pass to Rab- bit Springs, 3 or 4 miles from, and opposite, Hesperia, San Bernardino County, California (Grinnell, 1922:108)]; obtained by Frank Stephens, 29 June 1886, original number 314. Range. West central and southern Nevada, east central and south- eastern California, northeastern Baja California, extreme southwestern Utah, western and southwestern Arizona, and northwestern Sonora. Limits of the range are fairly well known. More specifically, in west central Nevada, from the vicinity of Wads- worth, Washoe County, to the Carson Sink area, south along the Walker River to the Huntoon Valley, Mineral County, east to San Antonio and Ralston Valley, south to 25 miles north of Ash Meadows and thence east to the western side of Beaver Dam Wash, Washington County, Utah. In east central California, from Oasis, Mono County, south to Saline Valley, Lone Pine, and Olancha, Inyo County, to the vicinity of Inyokern, San Bernardino County, to the vicinity of Nee- nach and east to Llano, Los Angeles County, to Agua Caliente and 116 T D. d. aquilus 1 2 D.d. deserti 3 D.d. arizonae 4 D.d. sonoriensis 4 = type-locality ® =specimens examined © = additional records MILES 32- 30 28 ge of the subspecies Fig. 14. Known occurrences and probable geographic ran of Dipodomys deserti (aquilus, deserti, arizonae, sonoriensis ). SUBSPECIES OF Dipodomys deserti 83 Manson Valley, San Diego County. In Baja California, along the west- ern edge of Laguna Salada and the eastern slopes of Sierra de Juarez and Sierra San Pedro Martir to about 56 km south of San Felipe. In Arizona, along the northwestern border, south to Lake Mead, then along the eastern valley of the Colorado River south of Lake Mead to the vicinity of Bouse and Quartzsite, Yuma County, east along the Gila River to the vicinity of Sentinel, Maricopa County, south to Bates Well and Quitobaquito. In Sonora along the coastal area south to about the Rio Magdalena. Diagnosis. 99 Size: Large; adult total length 337.3 to 348.5 mm; tail length in males 197.0 to 211.7 mm, and in females 188.0 to 200.0 mm; body length 135.0 to 145.0 mm. Color: In general, Light Buff to Pale Ochraceous-Buff, purest on sides, lightly mixed with long dusky hairs on dorsum; arietiform mark- ings usually pale with distinct buffy spot at base of vibrissae; orbital ring dusky; small light buffy patch on outer side of leg usually extends to ankle; plantar stripe not too distinct; heel usually dusky or light brownish; ventral surface of toes white or washed with light yellowish color; dorsal tail stripe similar to color of dorsum or dusky; ventral tail stripe usually absent and if present narrow and broken with same color as dorsal stripe; subterminal band of tail dusky drab to dusky, usually not continuous all around. Skull: Medium-sized; greatest length in males 45.1 to 46.3 mm, and in females 44.1 to 45.7 mm; rostrum shallow and usually slender; nasal length 16.4 to 17.1 mm; maxillary arch slightly slanted posterior- ly, its posterolateral edge not flared out; breadth across maxillary arches 23.6 to 24.8 mm; least interorbital breadth small, in males 13.5 to 14.4 mm and in females 13.1 to 14.1 mm; lacrimal usually small; breadth across auditory bullae in males 30.1 to 30.9 mm and in fe- males 29.5 to 30.5 mm; alveolar length of maxillary toothrow 5.6 to 6.0 mm; jugals usually heavy; mandibular length in males 18.2 to 18.9 mm and in females 17.5 to 18.8 mm. Also see Table 11. Comparisons. Compared with Dipodomys deserti aquilus, D. d. de- serti differs in the following: Size usually larger, especially in total length, tail length, and body length; color of upper parts, arietiform markings, plantar stripe, and dorsal tail stripe paler; ventral tail stripe usually absent; skull larger, particularly in greatest length, maxillary breadth, nasal length, and greatest breadth across the auditory bullae; incisors usually narrower. TABLE 11 Measurements (in mm) of adult specimens representing the different sub- species of Didopomys deserti (Mean with sample size as superscript and range below) Character Total length Tail length Hind foot length Ear length Body length Greatest skull length Basal skull length Length of nasals Breadth across maxillary arches Least interorbital breadth Greatest breadth across bullae Rostral breadth Rostral depth Bullar depth Alveolar length max. toothrow Least breadth supraoccipital Breadth across exoccipitals Alveolar length man. toothrow Mandibular length Length white tip of tail Weight, grams deserti: Palm Springs, Riverside County, California deserti aquilus arizonae 826 ¢,629Q 26 6, 19 134 46,1099 342.014 326.33 344.721 313.0 — 376.0 325.0 — 328.0 $25.0 — 361.0 206.314 192.08 200.921 187.0 — 229.0 190.0 — 195.0 190.0 — 310.0 53.514 52.08 52.428 51.0 — 56.0 51.0 — 55.0 49.0 — 56.0 -- 16.78 17.515 16.0 — 17.0 16.0 — 19.0 137.214 134.38 143.928 122.0 — 153.0 = 130.0 — 138.0 133.0 — 152.0 45.511 44,23 46.020 44.5— 46.5 44.0— 44.5 44.1— 48.1 51.501 31.18 32.119 30.8— 32.2 30.5 — 31.6 30.7 — 34.1 16.811 16.538 17.323 16.1 — 17.5 16.1 — 16.7 16.1— 184 23.311 22.63 23.522 22.1 — 25.0 22.3— 23.0 22.1 — 25.0 13.711 13.53 13.922 13.2— 14.5 13.1— 13.8 12.8— 15.4 30.214 29.58 30.919 28.9— 31.4 29.4— 29.6 29.4— 32.1 4.014 3.98 4,228 3.7— 43 37 — 4.1 39— 4.5 7.714 7.78 8.028 7.3— 83 76— 7.8 7.7— 88 15.014 14.88 15.219 14.5— 16.1 14.8— 14.8 146— 15.8 6.214 5.73 6.2238 58— 6.5 5.5 — 6.0 58— 68 0.214 0.68 0.428 0.0— 0.7 06— 0.6 00— 12 12.612 12.18 13.319 11.7— 13.8 116— 12.3 124— 14.4 6.014 6.08 6.228 5.7— 6.2 58— 6.2 59— 68 18.514 18.23 18.823 17.9— 19.9 17.9— 18.8 17.5— 19.9 20.88 14.38 24.220 12.0— 30.0 10.0— 18.0 15.0— 36.0 118.31 113.48 — 110.7 — 115.7 aquilus: 21 mi W, 2 mi N Lovelock, Pershing County, Nevada arizonae: 5 mi SE Picacho; 4 mi S, 1 mi E Picacho, Pinal County, Arizona sonoriensis: 1 mi N Rancho de Costa Rica; Rancho de Costa Rica, Sonora sonoriensis 763, 8929 362.815 345.0 — 385.0 210.715 198.0 — 231.0 53,119 142.0 — 176.0 46.714 456— 47.8 32.914 31.7— 326 17.414 16.2— 18.6 24.615 23.3— 25.9. 14.915 Mo. 159 31.115 30.3— 32.1 4.414 fim 43 8.115 (o— -64 15.615 15.2— 16.1 6.015 56— 64 0.415 00— 09 14.214 135—— 148 6.115 5.7— 65 18.815 17.9— 19.7 37.518 18.0 — 66.0 129.53 116.0 — 137.0 SUBSPECIES OF Dipodomys deserti 85 Compared with Dipodomys deserti arizonae, D. d. deserti differs in the following: Size usually smaller, especially body length; color of upper parts paler, less mixed with blackish and grayish hairs; arieti- form markings and dorsal tail stripe paler; ventral tail stripe usually absent; plantar stripe paler or absent; subterminal dark band of tail paler; skull smaller in general; basal length smaller; rostrum shal- lower; maxillary arches more slanted posteriorly; mastoidal bullae usually less inflated; greatest breadth across the bullae and mandibu- lar length smaller. Compared with Dipodomys deserti sonoriensis, D. d. deserti differs in the following: Total length, tail length, and body length smaller; color of upper parts paler, less mixed with blackish hairs; arietiform markings and dorsal tail stripe paler; ventral tail stripe usually absent; plantar stripe paler or absent; subterminal dark band of tail paler; skull smaller in general, especially in greatest length and in greatest width across auditory bullae; maxillary arches heavier; rostrum usu- ally shallower; lacrimal smaller; jugal heavier; mastoidal bullae less inflated; bullar depth, interparietal width, and alveolar length of maxillary toothrow smaller. Remarks. Typical Dipodomys deserti deserti is characterized by its pale buff color, pale arietiform markings, and the absence of a dark ventral tail stripe. The skull is medium-sized, but the posterolateral edges of the maxillary arches are not flared out and the auditory bullae are medium in size. Dipodomys deserti deserti intergrades, in a wide zone, with D. d. arizonae in southwestern Arizona. Some specimens from the following localities have some external and cranial characters in addition to some color features close to those of D. d. arizonae: Sentinel, Maricopa County; Bates Well, Pima County; northern bondary of Organ Pipe Cactus National Monument; 7 mi E Papago Well; 9 mi E Papago Well; Quitobaquito. The zone of intergradation between Dipodomys deserti deserti and D. d. sonoriensis has not been clearly determined because of insufh- cient material from this area. These two subspecies may intergrade along the Rio de Magdalena in northwestern Sonora. One adult from Est. Enchilayas has a larger body than D. d. deserti and in this respect is closer to D. d. sonoriensis. Dipodomys deserti deserti intergrades with D. d. aquilus in north- western Nevada. Several specimens from the vicinity of Wadsworth, Washoe County, and those from 6 mi NE Fernley, Lyon County, and some specimens from the vicinity of Fallon, Churchill County, are 86 KANGAROO RATS smaller in some external and cranial measurements than typical D. d. desertt. The specimens from the vicinity of Fernley have a darkish color, closer to that of D. d. aquilus. Color variation is apparent between different populations in this subspecies, especially those populations from southwestern Arizona. No appreciable skull differences, however, were found in these popu- lations to warrant taxonomic recognition. The palest colored speci- mens are among the populations from southeastern California. ‘The general color of the upper parts becomes more buffy (Pale Ochra- ceous-Buff) among populations from the western part of the range in California. In west central Nevada, the color becomes increasingly mixed with long dusky hairs, and the color markings become darker in the populations to the northwestern part of the range. Specimens from northwestern Arizona and the Beaver Dam Wash area in south- western Utah have a slightly darker coloration and occasionally a dis- rupted or broken ventral tail stripe is observed. Specimens from Baja California have a more buffy tone than those from southeastern Cali- fornia. The bufhest specimens of this race are found in southwestern Arizona, especially in the Yuma-Somerton area, and in northwestern Sonora. The color of these specimens is Light Ochraceous-Buff with a slightly pinkish cast, occasionally mixed with long dusky hairs and the subterminal band of the tail is usually dusky. The long dusky hairs are quite prominent in specimens from Punta Penasco, Sonora. The type-specimen of this subspecies is an immature with the per- manent PM4, pm4 erupted but almost unworn. Also a narrow inter- parietal bone is present in this specimen. Specimens from several isolated and noncontiguous populations of D. d. deserti have skulls larger in several measurements than those from the type locality. Such populations are found in Llano, Los An- geles County, California; the vicinity of San Felipe, Baja California; Wellton, Yuma County; and Quitobaquito, Pima County, Arizona. These represent variable populations and are not of a subspecific im- portance. Three specimens from Oasis, Mono County, represent a new county record for the state of California for D. d. deserti. Limits of the range of this subspecies are fairly well known and fu- ture collecting is unlikely to reveal any significant range extension. D. d. deserti is occupying, at the present time, almost all the suitable desert habitat in southwestern North America. Specimens examined. A total of 1,307 specimens from: NEVADA. WasuHor County: | mi W Wadsworth, 1 (Mvz) ; 14 mi E SUBSPECIES OF Dipodomys deserti 87 Wadsworth, 1 (mMvz). Lyon County: 6 mi NE Fernley, 2 (Mvz); 1% mi SE Wadsworth, 4,200 ft, 1 (mvz); 1 mi SE Wadsworth, 4,200 ft, 1 (Mvz) . CHURCHILL County: 10 mi NW Fallon, 1 (usNm) ; 7 mi NW Fallon, 4,000 ft, 1 (Uusnm); 1 mi NW Soda Lake, 4,000 ft, 2 (ku), 1 (Mvz) ; 1 mi S Soda Lake, 4,000 ft, | (mvz); 4 mi NW Fallon, 4,000 ft, 2 (USNM) ; 4 mi NE Fallon, 1 (ur); 7 mi W Fallon, 7 (ur); 5 mi W Fallon, 4,000 ft, 1 (mvz) ; 4 mi W Fallon, 4,000 ft, 2 (mvz) ; Ragtown, Carson River, 4 (UsNM); 14 mi WSW Fallon, 13 (ku); 8 mi S Soda Lake, 4,000 ft, 1 (mvz); 16 mi S Fallon, 2 (ku). MINERAL County: 8 mi NNW Schurz, Walker River, 2 (ku); 8 mi SE Schurz, 4,100 ft, 1 (Mvz) ; Cat Creek, 4 mi W Hawthorne, 4,500 ft, 1 (mvz); Huntoon Valley, 5,700 ft, 4 (mvz). ESMERALDA County: Columbus, 3 (USNM) ; 3% mi SE Coaldale, 4,850 ft, 2 (mvz); 4 mi SE Coaldale, 4,850 ft, 2 (KU), 2 (Mvz); 13 mi N Goldfield, 5,100 ft, 1 (mvz); 1314 mi NW Goldfield, 4,850 ft, 13 (mvz); 7 mi N Arlemont, 5,500 ft, 17 (mvz) ; ] mi S Fish Lake, 1 (mMvz) ; Clayton Valley, 5 mi SE Blair, 5,000 ft, 1 (USNM) ; 8 mi SE Blair, 4,500 ft, 3 (mvz) ; Clayton Valley, sand dunes, 8 mi SE Blair, 4,000-4,500 ft, 6 (UusNM). Nye County: San Antonia, 5,400 ft, 1 (mvz) ; Ralston Valley, 5,650 ft, 34 mi E, 1 mi N Tonopah, ] (mMvz); N shore Mud Lake, 5,300 ft, S end Ralston Valley, 2 (Mvz) ; Thorpes [=Thorps Mill], 4 (usnm) ; Oasis Valley, 1 (UsNM) ; Table Mt., 25 mi N Ash Meadows, 4 (UsNM) ; 20 mi NNW Ash Mead- ows, 2 (USNM) ; Amargosa Desert, 2,500 ft, 20 mi SE Beatty, 4 (Mvz) ; 15 mi N Ash Meadows, 3 (usNM); Ash Meadows, 38 (USNM) ; Pahrump Valley (near Stewart Well), 16 (UsNM). LINCOLN County: Coyote Spring, 2,800 ft, 4 (mvz), 1 (spsNH). CLARK County: Indian Spring Valley, 14 mi N Indian Springs, 3,100 ft, 1 (cas), 11 (mvz) ; Bunker- ville (Virgin River Valley), 2 (usNM); 7 mi N [on] Virgin arm of Boulder Lake [=Lake Mead], E side, 920 ft, 1 (mvz) ; 5 mi SE Over- ton, 1,200 ft, 1 (mvz) ; island in Boulder Lake, mouth of Virgin River, ] (Mvz); Valley of Fire, 12 mi SW Overton, 1 (Mvz); 114 mi NW Corn Creek Hdq., Desert Game Ranch, | (UsNM) ; Corn Creek Ranch, ] (usNM); Colorado River, bend near Calville (orig. tag: Lincoln Co.) , | (usNM) ; Colorado River (orig. tag: Lincoln Co.) , 4 (UsNM) ; Stone’s Ferry, 1 (UsNM) ; Colorado River Head of Black Canon (orig. tag: Lincoln Co.) , 1 (usnm) ; Colorado River at Jap Ranch, 14 mi E Searchlight, 500+ ft, 12 (mvz). CALIFORNIA. Mono County: Oasis, 3 (LACM). INyo County: Owens Valley, 6 mi S Alvord, 4,000 ft, 2 (usnm); Big Sand Dunes, Eureka Valley, 300 ft, 3 (mvz) ; Mesquite Spring, N end Death Valley, 6 (sDSNH) ; Death Valley, Mesquite Valley, 3 (UsNM); Death Valley, 88 KANGAROO RATS Mesquite Well, 4 (usnM); Mesquite Flat, 8 mi N Stovepipe Wells, Death Valley, 2 (spsNH) ; 3 mi N Saline Valley, Soda Works, 1,140 ft, 2 (mvz) ; Midway Well, Death Valley National Mon., 1 (cas) ; Saline Valley, Soda Works, 1,100 ft, 1 (mvz) ; Triangle Spring, Death Valley, —13 ft, 1 (LacmM), 6 (Mvz); Salt Creek, Death Valley, —200 ft [SE corner of T15S, R45E], 2 (mMvz) ; Lone Pine, 5 (UusNm) ; 4 mi N Keeler, 6 (SsDSNH) ; Keeler, 14 mi [E] from Lake, 2 (Mvz) ; Keeler, 3,600-3,604 ft, 5 (FMNH), 37 (Mvz), 12 (UsNM); 1.2 mi (by road) SSE Keeler, 3,600+ ft, 6 (mvz); Furnace Creek Ranch, Death Valley, —178 ft, 34 (Mvz) ; Furnace Creek (Death Valley), 7 (FMNH) , 23 (USNM) ; 2 mi S Furnace Creek Ranch, Death Valley, —178 ft, 1 (atvz); 37/10 mi NE Olancha, Sanddune, 3,600 ft, 4 (mvz) ; Kelley's Well, Amargosa River, 2,100 ft, 3 (mvz); Death Valley, 6 (AMNH), 1 (KU), 23 (USNM) ; Pana- mint Valley, 11 (UsNM):; Bennett’s Wells, Death Valley, 18 (usNM) ; Ballarat, 2 (FMNH); 12 miles Spring, near Resting Springs, 8 (USNM) ; Shoshone, 10 mi W of Kingston Ranch, 1,560 ft (T22N, R7E), 2 (Mvz) ; Resting Springs, Death Valley, 8 (usNM) ; Argus Mt., 2,200 ft, 2 (USNM); Amargosa River, 1 (UsNM); Amargosa Valley, 4 (USNM) ; Amargosa, 3 (USNM) ; Amargosa Wash, S end Death Valley, 1 (UsNM). Los ANGELES County: 2 mi S Pecks Butte, Mojave Desert, 2,650 ft. 6 (mvz); Black Butte, Mojave Desert, 3,000 ft, 1 (vz); Llano, 1 (cas) , 16 (LACM). SAN BERNARDINO County: Borax Flat, 1,750-2,100 ft, 5 (UsSNM) ; Saratoga Spring, 1 (LACM), 1 (ut), 8 (USNM) ; 814 mi SSE Ripley (Ne- vada) [about 5 mi SE Kingston], 14 (mMvz); Lone Willow Spring, 7 (USNM) ; 15 mi E Inyokern, | (Mvz) ; Raymond’s Well, Salt Well Val- ley, 2,500 ft [plotted as Salt Well], 5 (usnm) ; 8 mi W Clark Mt., 3,300 ft, 2 (mvz); Ivanpah, 2 (usnm) ; Mesquite, 1,246 ft, 1 (mvz); 214 mi SW Kelso, 2,100 ft, 20 (mvz); 114 mi NE Barstow, Mojave Desert, 2,200 ft, 3 (mvz); Afton Canyon, Mojave Desert, 44 mi E Barstow, ] (Mvz); Daggett, 23 (FMNH) ; Fenner, 2,000 ft, 1 (UsNm) ; Needles, 1 (cas) ; Ludlow, 1,712 ft, 2 (amnu), 1 (Mvz), 9 (UsNM) ; Danby, 1,500 ft, 2 (UsNM); Hesperia, 1 (UsNM) ; Mojave River, 8 (USNM) ; Cotton- wood Spring, | mi W Old Woman Springs, 3 (Mvz) ; 714 mi NE Chub- buck, Old Woman Mts., 2,320 ft, 1 (mvz); Colorado River, 29 mi S Needles, 5 (Ku) ; Surprise Spring (T3N, R7E) , 35 mi NE Whitewater Station, 2,400 ft, 1 (mvz); 4 mi N Twentynine Palms, 2,200 ft, J (Mvz); 16 mi E Twentynine Palms, | (mMvz); Colorado River, opp. Parker [Arizona], 350 ft, 1 (usNm); Mojave Desert, E Morong [=Mo- rongo] Valley, 3,100 ft, 2 (usnm) ; 1 mi S Virginia Dale mine, Joshua SUBSPECIES OF Dipodomys deserti 89 Tree National Monument, 1,900 ft, 1 (mvz); 2 mi S Blythe Jet. [=Rice], 800 ft, 1 (mvz). RIVERSIDE COUNTY: Seven Palms [Well], 1 (CAs); White Water [= Whitewater], near San Jacinto Mts. (orig tag: San Diego Co.), 1 (AMNH), 1 (FMNH), 1 (SDSNH), 1 (USNM) ; Whitewater Station, 1,130 ft, 6 (mMvz); Riverside Mt., Colorado River, | (mvz); 1,000 Palms, 2,000 ft, 2 (mvz) ; Palm Springs, 455 ft, Colorado Desert, 4 (FMNH) , 2 (LACM) , 8 (Mvz), 2 (SDSNH), 2 (USNM) ; | mi S Palm Springs, 1 (Mvz); S end Coxcomb Mts., 1 (LacmM), 1 (ur); 1144 mi W, 234 mi S Pinto Peak [in the Joshua Tree National Monument], 1,775 ft, 3 (mvz) ; Indio, 1 (usNM); 4 mi NE Desert Center, 1 (LAcm); 3 mi N Palo Verde intake, 300 ft, Colorado River, 1 (LAacm); 4 mi NE Mecca, | (Mvz) ; Hopkins Well, 2 (LAcM), 1 (UI); Mecca, 36 (Mvz); Dos Palmos (2 mi W Dos Palmos Spring) , 2 (mMvz) ; 15 mi SW Ehrenberg, 2 (usNM) ; Rannels [=Rannells] (orig. tag: Imperial Co.) , 4 (LACM) . SAN Dieco County: Aqua Caliente, Colorado Desert, 1 (AMNnH), | (USNM) ; Baregas [= Borrego] Springs, 5 (AMNH) , 4 (FMNH) , 3 (USNM); Borego [=Borrego] Valley, 4 (spsNH) ; Borego [=Borrego] Hotel, 3 (cas) ; San Felipe Narrows, | (LAcM); La Puerta Valley [=Manson Valley], 2,100 ft, 10 (spsNH) ; Carrizo Creek, 500 ft, 1 (LAcm) , 3 (Mvz), 3 (SDSNH) . IMPERIAL County: Palo Verde, 2 (LACM); 25 mi SW Ehrenberg, 1 (USNM) ; 4 mi S Palo Verde, 275 ft, 5 (AMNH), 2 (Mvz) ; Salt Creek, 2 (Mvz); Brawley, 3 (USNM); 15 mi E Holtville, 3 (spsNu) ; Laguna, Colorado Desert, | (FMNH), 2 (SDSNH); Indian Wells, New River (orig. tag: San Diego Co.), 2 (AMNH), 1 (USNM); Coyote Well, 4 (Mvz) ; Coyote Wells, Colorado Desert, | (usNM) ; Coyote Wells, 271 ft, 4 (CAs), 1 (SpSNH), 1 (USNM); 1 mi W Pilot Knob, | (spsnw) ; Pilot Knob (orig. tag: San Diego Co.), 1 (usNmM); Pilot Knob, Colorado River, 2 (Mvz); near Pilot Knob, Colorado River, 6 (Mvz); Fort Yuma, 3 (LACM) ; 14 mi W Calexico, 1 (Mvz). BAJA CALIFORNIA. Alamo River, 20 mi SW Pilot Knob, 50 ft, 12 (Mvz) ; Gardner's Laguna, Salton River, 2 (usNM); Las Palmas Can- yon, W side of Laguna Salada, 15 mi S of N end, 200 ft, 2 (mvz) ; Vol- cano Lake, 5 (usNM); 13 mi N El Mayor, 2 (Mvz); Base Cocopah Mts., 100 ft, 1 (UsNmM) ; De Mara’s Well ( on W side of) Laguna Sala- da [35 mi below International Line (Huey, 1951:253)], 5 (spsnn) ; Mount Mayor, 1 (usNM) ; 40 mi N San Felipe, 1 (spsnu) ; 36 mi N San Felipe, 1 (LtAcM); 30 mi N San Felipe, 1 (spsNH) ; Valley at E base, San Pedro Martir Mts., 5 (UsNM); San Felipe, 11 (FMNH), 15 (Mvz), 90 KANGAROO RATS 9 (SDSNH) ; San Felipe Bay, 3 (UsNM); Sonora del Norte, 3 mi SSW San Felipe, 4 (Mvz). UTAH. WaAsHINGTON County: Beaver Dam Wash, 8 mi N Utah- Arizona border, 2,600-2,800 ft, 2 (UU); 14 to 14 mi S Terry’s Ranch on Beaver Dam Wash, 7 to 634 mi N Utah-Arizona border, 2,600 ft, 1 (uu); Beaver Dam Wash. 5 mi N Utah-Arizona border, 2,600 ft, 6 (uu) ; Beaver Dam Wash, 1 (v1). ARIZONA. MouHave County: Mormon Well, Beaver Dam Wash, ] (KU) ; near mouth of Beaver Dam Creek, just above Littlefield, 1,500 ft, 7 (usNM) ; Littlefield, 1,500 ft, 1 (usnm); Beaver Dam (Lodge) , 1,900 ft, 14 (ut); Beaver Dam (Nevada) [in the Virgin River Valley], ] (UsNM); Grand Wash, 2,100 ft, 2 mi S, 3 mi E Pakoon Springs, 3 (UI) ; Black Willow Spring, 1,900 ft, 4 mi S of Pakoon Springs, 5 (ur) ; Seven Springs, 1,600 ft, 8 mi S, 1 mi W Pakoon Springs, 9 (U1); Grand Wash, 1,800 ft, 8 mi S Pakoon Springs, 1 (UsNM) ; Lake Mead, 1,200 ft, foot of Grand Wash, 4 (u1) ; Old Searchlight Ferry, 500+ ft, 8 (mvz) ; Old Searchlight Ferry, Colorado River, 1,000 ft, 1 (usNm) ; Colorado River, 31 mi N, 214 mi W Camp Mohave, 5 (Mvz) ; Harper’s Ferry, 7 (USNM); Fort Mohave, 13 (USNM) ; opposite Needles, Wm. Robert’s Ranch, 500 ft, | (usnM) ; Mellen [=Topock], 18 (mMvz) ; Topock, 600 ft, 2 (UsNM). YuMA County: Parker, 350 ft, 8 (usNM); 5 mi E Parker, 4 (ku) ; 514 mi E Parker, 9 (ut); 514 mi SE Parker [actually 5 mi E], 1 (un) ; Eh- renberg, 2 (LACM), 1 (USNM); Ehrenberg, Colorado River, 2 (Mvz) ; 10 mi S Quartzsite, 1 (LAcM); 25 mi below Ehrenberg, Colorado River, 1 (mvz); 15 mi NE Yuma, 3 (usnM) ; 5 mi NE Laguna, Colo- rado River, 3 (mvz); Dateland, 5 (FMNH); Texas Hill [=Stoval], 2 (USNM) ; 6 mi E Yuma, 1 (spsNH) ; Yuma, 13 (usNM) ; Old Quarry near Yuma, 1 (spsNH); near Yuma, 4 (FMNH) ; 214 mi SE Yuma, | (Mvz) ; 10 mi E, 4 mi S Yuma, | (ut); Gila Center, 5 (usnm) ; Adonde, 11 (USNM) ; 14 mi E Wellton, 3 (ur); Wellton, 20 (spsNH), 2 (USNM) ; 9 mi SW Yuma, 2 (Mvz); 7 mi S Yuma, | (ur); 3 mi E Somerton, 8 (u1) ; 1214 mi S Yuma, 11 (v1); 5 mi ESE Somerton, 6 (ur) ; 6 mi SE Somerton, 20 (ur); 4 mi S Gadsden, 120 ft, 5 (AMNH), 8 (Mvz) ; Mon- ument 204, Colorado River, 27 (usNM) ; 10 mi SE Fortuna Mine, 300 ft, 1 (mvz); Yuma Desert, Monument 200, 3 (UsNM) ; 16 mi SE For- tuna Mine, 300 ft, 5 (amMNnu), 1 (KU), 11 (mvz); Tinajas Altus [=Al- tas], | (usNM); Tule Wells, 1 (usnm); S end Tule Desert, 3 mi N Monument 182, 1 (spsNuH) ; E end Pinacate, 2 mi NW Monument 180, 6 (uI). Pima County: Bates Well, 2 (mvz); N Boundary Organ Pipe Cactus National Monument, 15 mi S Ajo, 5 (ur); Papago Well, 1 (ur); 7 mi E Papago Well, 2 (spsNH); 9 mi E Papago Well, 1,100 ft, 1 SUBSPECIES OF Dipodomys desertt 91 (Mvz) ; Quitovaquito [=Quitobaquito], 1 (spsNH), 7 (USNM). Mart- copa County: Sentinel, 2 (AMNH). SONORA. S base Tule Mts., 3 (UsmN) ; El Doctor, 5 (ucLA) ; 1% mi S Crater Elegante, 34 mi W Sonoita [=Sonoyta], 900+ ft, 1 (Mmvz) ; Poso McDougal, Pinacate Region, 850+ ft, 1 (mvz); Batamote, Rio Sonoita [—Sonoyta], 30 mi WSW Sonoita [=Sonoyta], 8 (Mvz); 1 mi NNE Punta Penasco, 2 (Mvz) ; Punta Penasco, 50+ ft, 1 (mvz) ; Punta Penascosa [=Penasco], 17 (spsNH) ; near Punta Penasco, | (UNM) ; Est. (Las) Enchilayas, 2 (FMNH) ; 28 mi W Caborca, Vado EI Coyote, | (ur). Additional records. NEVADA. (All from Hall, 1946:431, unless otherwise indicated.) CHURCHILL County: 15 mi WNW Fallon, 1 (KU); 15 mi WSW Fallon, 1 (ku). NyE County: Stonewall Flat, 14 mi SE Goldfield; 1 mi N Beatty, 3,400 ft; 314 mi N Pahrump, 2,667 ft; 1% mi N Pahrump, 2,667 ft. LincoLN County: Carp. CLARK County: Mesquite; Indian Springs, 3,280 ft; St. Thomas; 14 mi E St. Thomas; Corn Creek, 2,840 ft. CALIFORNIA. Los ANGELEs County: 16 mi NE Palmdale, about 3,261 ft (Butterworth, 1961a). SAN BERNARDINO County: Calico Val- ley, 1 (Brattstrom, 1960:404) . RiversipE County: Coachella, 1 (Grin- nell, 1922110). BAJA CALIFORNIA. 61 km NE, 3.4 km W San Felipe (Alvarez, 1960:422) ; 56 km S San Felipe (Alvarez, 1960:422) . ARIZONA. Yuma County: 11 mi NW Bouse, | (Cockrum, 1960: 154); 2 mi NE Ehrenburg, 1 (Tewc); 15 mi NE Yuma (Cockrum, 1960:154) . Pima County: SE Growler Valley, about 3 mi SW Growler Mine (Huey, 1942:361) ; 1 mi E Quitovaquita [=Quitobaquita], Abra Valley (Huey, 1942:361) . SONORA. Near Puerto Penasco, 2 (ua, Cockrum and Bradshaw, 1963:8) ; Rancho Noce Buena Vieja, 120 km SE [12 km N sic] Sonoy- ta (Alvarez, 1960:422) . Dipodomys deserti aquilus Nader Dipodomys deserti aquilus Nader, Proc. Biol. Soc. Washington, 78 (5): 52, 21 July 1965, original description. Type. Male, adult, skin and skull; No. 126411, Museum of Verte- brate Zoology, University of California; from 11% mile northwest High Rock Ranch, about 12 miles southeast of Wendel, 4,080 feet, Lassen County, California; obtained by C. S. Thaeler, 21 July 1960, original number 1022. 92 KANGAROO RATS Range. East central Lassen County, California, and northwestern Nevada. More specifically, from the vicinities of Wendel and High Rock Ranch, Lassen County, California, east to the vicinities of Nixon and Flanigan, Washoe County, Nevada, northeast to the vicinity of Jungo, Humboldt County, and southwest to Adobe Flat and the vicinity of Toulon, Pershing County. Limits of the range are not too well known, especially in the northern and northwestern parts; future collecting may reveal a wider range of this subspecies in these directions. Diagnosis. Size: Small, adult total length averages about 323.5 mm; tail length averages in males about 193.4 mm and in females about 190.0 mm; body length averages about 132.2 mm. Color: In general, Pale Ochraceous-Buff, heavily mixed with grayish and long blackish hairs on dorsum; arietiform markings dusky; orbital ring blackish; plantar stripe brownish-black; dorsal tail stripe dark; ventral tail stripe dark and usually present; subterminal band of tail blackish. Skull: Small-sized; greatest length averages about 44.2 mm; breadth across maxillary arches narrow, averaging 23.0 mm; nasals short, averaging 16.2 mm; greatest breadth across auditory bullae nar- row, averaging about 29.5 mm; incisors robust. Also see Table 11. Comparisons. For comparison with Dipodomys deserti deserti, see account of that subspecies (p. 83). Remarks. Typical Dipodomys deserti aquilus is characterized by its small external measurements, dark color, and small skull, especially the greatest length, maxillary breadth, nasal length, and greatest breadth. Dipodomys deserti aquilus intergrades with D. d. deserti in north- western Nevada. Specimens from the vicinity of Toulon, Pershing County, Nevada, are slightly larger in some measurements than typi- cal D. d. aquilus. Some of these specimens lack the ventral tail stripes. An adult specimen from near High Rock Ranch, Lassen County, and the young specimens from near Flanigan, Washoe County, are darker than the other specimens from northwestern Nevada. Specimens examined. A total of 12 specimens from: CALIFORNIA. Lassen County: 114 mi NW High Rock Ranch, T 28 N, R 17 E, Sec. 26, 4,040 ft, 1 (mvz). NEVADA. WasHOE County: 414 mi N, 414 mi W Flanigan, 4,000+ SUBSPECIES OF Dipodomys deserti 93 Fig. 15. Dipodomys deserti arizonae from 4 mi S and 1 mi E Picacho, Pinal County, Arizona. (Photograph by W. Goodpaster) ft, 2 (mvz). HumBotpt County: 8 mi E, 1 mi N Jungo, 4,200 ft, 1 (mMvz). PersHING County: 21 mi W, 2 mi N Lovelock, 4,000 ft, 3 (mvz) ; 314 mi NNE Toulon, 3,900 ft, 1 (vz) ; 3 mi E Toulon, 3,900 ft, 4 (Mvz). Additional records. NEVADA. WasHoE County: 16 mi E Wendel (California) (Hubbard, 1961:135) ; 414 mi N and 214 mi W Nixon, 2 (Coll. Ira W. La Rivers and T. J. Trelease) (Hall, 1946:431); % mi SE Pyramid Lake, 3 (Stock, 1974:506) . Dipodomys deserti arizonae Huey Dipodomys deserti arizonae Huey, Trans. San Diego Soc. Nat. Hist., 12:99, 10 February 1955, original description. Dipodomys deserti sonoriensis: Willet, J. Mammal., 18:101, 14 Febru- ary 1937. Type. Male, adult, skin and skull; No. 12532, San Diego Society of Natural History Collection; from 3 miles southeast of Picacho, Pinal County, Arizona; obtained by Laurence M. Huey, 14 May 1937, no original number. 94 KANGAROO RATS Range. South central Arizona. More specifically, north from about 10 mi N Sunnyslope, Maricopa County, Arizona, southeast to Florence Junction, south to the vicinity of Picacho and Green’s Reservior, Pinal County, west to about 10 mi N Ajo, Pima County, north to about 15 mi NW Buckeye, Maricopa County. Limits of the range are fairly well known except in the west- ern and the northwestern parts. Diagnosis. Size: Large. Color: In general, Pale Ochraceous-Buff heavily mixed with gray- ish and long dusky hairs on dorsum; arietiform markings dusky to black; orbital ring dusky to blackish; plantar stripe light brown to dark brown; ventral side of toes usually yellowish; dorsal tail stripe blackish; dark ventral tail stripe continuous or broken; subterminal dark band of tail brown to blackish; usually meets ventrally at its dis- tal end in a narrow zone. Skull: Large-sized, adult basal length large, in males 32.4 to 33.1 mm and in females 30.5 to 32.2 mm; nasals usually long, 17.2 to 17.8 mm; lacrimal usually small; jugals usually heavy; maxillary arches more acutely angled with long axis of skull; anteromedial border of maxillaries extend somewhat along nasals; rostral depth in males 8.1] to 8.3 mm and in females 7.7 to 8.1 mm; mandible long, in males 19.0 to 19.4 mm and in females 18.0 to 19.1 mm. Also see Table 11. Comparisons. Compared with Dipodomys deserti sonoriensis, D. d. arizonae differs in the following details: Color of upper parts slightly paler and more buffy; total length usually less; tail shorter; body usu- ally shorter; skull with maxillary arches heavier, less slanted posterior- ly, and their posterolateral edges less flared out; jugals heavier; lacri- mals smaller; auditory bullae shallower; interorbital breadth usually narrower; mandible usually longer; alveolus of mandibular toothrow longer. For comparison with Dipodomys deserti desertt, see account of that subspecies (pp. 85 ff.) . Remarks. Typical Dipodomys desert arizonae is characterized by its grayish color, dark ventral tail stripe, large auditory bullae, more angled maxillary arches with reference to the long axis of the skull, alveoli of maxillary toothrow long, and long mandible. In comparing Dipodomys desertit arizonae with D. d. deserti, Huey (1955:99) stated that the former has a smaller skull and a slenderer SUBSPECIES OF Dipodomys deserti 95 rostrum. This study shows that topotypes and most D. d. arizonae are larger, in several cranial measurements, than those of D. d. deserti (also see Table 11). As for the slenderness of the rostrum, there are no real differences between the two subspecies, and in fact many speci- mens of D. d. deserti have slenderer rostra than those of D. d. arizonae. Dipodomys deserti arizonae intergrade in a wide zone with D. d. deserti to the west in south central Arizona. Some specimens from the following localities in the zone of intergradation, when compared with typical D. d. arizonae, have slightly more ochraceous color and smaller cranial measurements: 16 mi W, 2 mi N Buckeye; 11 mi S, 714 mi E Buckeye; Gila Bend, Maricopa County. One adult from 10 mi N Ajo, Pima County, has more of a pinkish buft color and some of its cranial characters are smaller. Variations within the range of D. d. arizonae are not great. Speci- mens from the following localities show some degree of variation when compared to typical D. d. arizonae: Specimens from the vicinity of Scottsdale, Maricopa County, have more inflated mastoidal bullae and are larger in several skull measurements, especially in greatest length, basal length, and nasal length. Specimens from Phoenix, Maricopa County, and from Maricopa, Pinal County, have slightly more bufky color of the upper parts, paler arietiform markings, and paler ventral tail stripe. Adults from Gila Bend, from10 mi S Gila Bend, Maricopa County, and from 10 mi N Ajo, Pima County, are larger in total length and in maxillary breadth. Recent field work by W. Goodpaster in central Arizona revealed an interesting transition in the habitat requirements of this subspecies of the desert kangaroo rat. The typical habitat of D. deserti is deep, loose, drifting sand or sand dunes. In his field notes, Goodpaster wrote that two specimens of D. d. arizonae, ut Nos. 27535 9 and 275369, from 6 mi N, 1 mi E Florence, were collected on 15 March 1963 in hard gravelly soil. This is the only locality known to me in which specimens of D. deserti were collected in gravelly soil. Although there is a possibility that the animals were foraging on the gravelly soil while their burrows are in the loose sandy soil, it is assumed, from Goodpaster’s notes, that the animals were trapped near their burrows which were in the gravelly soil. This shift in the habitat requirement of the desert kangaroo rat is important from the evolutionary and dis- tributional point of view of the species. Specimens examined. A total of 133 specimens from: ARIZONA. Maricopa County: 9.7 mi N Dunlap [Ave.] and 7th St., 96 KANGAROO RATS and 0.3 mi W on Cave Creek Rd. [about 9.7 mi N Sunnyslope], 1 (ur) ; 5 mi N Shea Blvd. and Scottsdale Rd. [11] mi N Scottsdale], 1 (asv) ; 15 mi N, 2 mi E of ASC [Arizona State College] at Tempe, 1 (asv) ; 10 mi N, 2 mi E Scottsdale, 1,000 ft, 1 (asu); 2.5 mi N Shea Blvd. on Scottsdale Rd. [814 mi N Scottsdale], 1 (Asu); 8 mi N Scottsdale on Scottsdale Rd., 1 (ur); 1 mi W Scottsdale Rd., 14 mi N Bell Rd., 1 (asu), 1 (ur); 1 mi W Scottsdale Rd.. 300 yds N Bell Rd., 1 (asv) ; 250 yds W, 200 yds N Jct. Scottsdale and Bell Rds., 1 (asu) ; 200 yds NW Jet. of Scottsdale and Bell Rds., 1 (Asu); 100 yds NE of Jet. Scottsdale and Bell Rds., 4 (Asu); 10 mi N Tempe to Bell Rd. on Scottsdale Rd., 1 (asu) ; 5 mi N Scottsdale, 1 (Asu) ; 5 mi N, Y% mi E Scottsdale, 1,100 ft, 1 (Asu) ; Bell Rd. at Pima Rd., 1 (Asu) ; Phoenix, I (AMNH), 8 (USNM) ; 16 mi W, 2 mi N Buckeye, | (ur); 11 mi S, 714 mi E Buckeye, 6 (ur); Gila Bend, 9 (usNM); 10 mi S Gila Bend, 3 (SDSNH). PINAL County: Florence Jct., | (AMNH); 6 mi N, | mi E Florence, 3 (u1); 5 mi N Florence, 1 (ur); 2 mi N Florence, 2 (mvz) ; Sacaton, 1 (USNM); Maricopa, 5 (UsNM); 1 mi E, 1 mi N Florence, 7 (ul); Florence, 4 (AMNH); 5 mi N Stanfield, | (ur); 11 mi W Casa Grande, | (kU), 11 (spSNH) ; Casa Grande, 5 (UsNM) ; 3 mi E Picacho, 6 (LACM); 3 mi SE Picacho, 17 (spsNH); 4 mi S, 1 mi E Picacho, 17 (u1) ; Green’s Reservoir, 1,600 ft, 2 (Tcwc). Pima County: 10 mi N” Ajo, 1 (USNM). Dipodomys deserti sonoriensis Goldman Dipodomys deserti sonoriensis Goldman, Proc. Biol. Soc. Washington, 36:139, 1 May 1923, original description. Type. Male, adult, skin and skull; No. 242306, U. S. Biological Sur- veys Collection; from La Libertad Ranch, 30 miles east of Sierra Seri, Sonora, México; obtained by Charles Sheldon, 3 January 1922, origi- nal number 22611-X. Range. The coastal area of west central Sonora, México. More specifically, from the southern banks of the Rio de Magda- lena, Sonora, south along the coastal region as far as the vicinity of Estero Testiota, and east along the Rio de Sonora as far as the vicinity of Hermosillo. Limits of the range are not well known except the southern part. It is doubtful that this form of D. deserti will be found to occur much farther to the east beyond the coastal sand dunes, and beyond the vicinities of Hermosillo and Estero Testiota. SUBSPECIES OF Dipodomys desertt 97 Diagnosis. Size: Large; adult total length 349.0 to 364.4 mm; tail length in males 212.1 to 219.0 mm, and in females 201.0 to 221.5 mm; body length 147.0 to 154.4 mm. Color: In general, Pale Ochraceous-Buff, purest on sides, heavily mixed with long blackish hairs on dorsum; arietiform markings black- ish; orbital ring blackish; plantar stripe brownish with lighter shade on ventral side of toes; dorsal tail stripe blackish; ventral tail stripe dusky and usually present; subterminal band of tail blackish. Skull: Large-sized; greatest length in males about 46.7 mm and in females 45.8 to 46.8 mm; maxillary arch weak, its posterolateral edge slightly flared; lacrimal large, its extension along posterior bor- der of maxillary arch equaling about one-half of the distance to outer angle; interorbital breadth great, in males 14.5 to 14.8 mm and in fe- males 14.2 to 15.2 mm; jugals slender, spur at its posterior end usually not well developed; mastoid bullae large, bullar depth 15.6 to 15.8 mm. Also see Table 11. Comparisons. For comparisons with Dipodomys deserti deserti and D. d. arizonae, see accounts of those subspecies (pp. 85 and 94). Remarks. Typical Dipodomys desertt sonoriensis is characterized by its large size, blackish color, thin maxillary arches, slender jugals, and inflated mastoidal bullae. Goldman (1923:139) in his description of this subspecies stated that the size of the articulating area of the squamosal with the parietal, as viewed dorsally, is small. This area and the size of the squamosal, in general, are variable throughout the range of the species and do not provide reliable taxonomic characters. Dipodomys deserti sonoriensis may intergrade with D. d. deserti to the north along the Rio de Magdalena in northwestern Sonora. Lack of sufficient material from the northern part of the range of the former does not permit clear demonstration of this intergradation. Specimens from Cerro Prieto, however, are regarded here as intergrades. A sub- adult female from this locality has more of an ochraceous color, closer to that of D. d. deserti. Two other specimens from this locality lack the dark ventral tail stripe. Another variant is an adult male from Rancho Dolores with more reddish color than the rest of the series and the maxillary arches slightly more slanted posteriorly, similar to that of D. d. deserti. Several specimens from Bahia Kino are smaller in sev- eral skull measurements than is typical for D. d. sonoriensis. 98 KANGAROO RATS The dark ventral tail stripe is not always present in specimens as- signed to this race, but it has been present in 56% of the specimens examined. This ventral tail stripe is disrupted or broken in some spec- imens and continuous in others. Three specimens from Estero Testiota were taken about 35 miles south of the southernmost recorded locality for this subspecies. The vicinities of Estero ‘Testiota and Hermosillo most probably are the southern and southeastern limits, respectively, as no apparent suitable habitat is available farther south and southeast of them. Specimens examined. A total of 77 specimens from: SONORA. Cerro Prieto, 3 mi N Puerto de Lobos, 500= ft, 2 (MVZ) ; La Libertad Ranch, 30 mi E Sierra Seri, | (UsNM); La Libertad Ranch, [30 mi E] Sierra Seri, 1 (UsNM); Rancho Dolores, 7 mi ESE Rancho Libertad, 47 mi W Hermosillo, 300 ft, 8 (mMvz); 7 mi ENE Pozo Es- calante, 2 (ku); 1 mi N Rancho de Costa Rica, Rio Sonora, 270 ft, 4 (Mvz) ; Rancho Costa Rica, 45 mi SW Hermosillo, 15 (ucLa) ; Rancho de Costa Rica, Rio Sonora, 200 ft, 1 (mvz); Costa Rica Ranch, | (UsNM) ; 15 mi W, 3 mi S Hermosillo, 7 (ur); 4 mi N Bahia Kino, 3 (LAcM) ; 3 mi N Bahia Kino, ] (LAcM) ; Bahia Kino, 10 (spsnu) , 10 (u1); 114 mi E Bahia Kino, 1 (LAcmM); 5 mi NE Estero Testiota, 7 - (mvz) ; Estero Testiota, 3 (Mvz). Additional records. SONORA. Sand dunes, Puerto Libertad, 25 ft, ] (ua, Cockrum and Bradshaw, 1963:8) ; vicinity of Hermosillo (Villa, 19412571). PHYLOGENY OF THE SPECIES D. SPECTABILIS AND D. DESERTI Fossil history of the genus Dipodomys was reviewed by Setzer (1949) and Lidicker (1960). Members of this genus first appeared in the late Pliocene or early Pleistocene and evolved from the primitive hetero- myid Prodipodomys. Different forms which belong to the genus Pro- dipodomys are known from the middle Pliocene to early Pleistocene (Hibbard, 1937, 1939, and 1962). Prodipodomys rexroadensis was de- scribed by Hibbard (1954:228) from the Upper Pliocene deposit of the Rexroad fauna, Meade County, Kansas. On the basis of the teeth only, Hibbard (1954:231) stated that this species can be considered as ancestral to Dipodomys. Gidley (1922:123) described D. minor from late Pliocene deposits from Benson, Arizona. If one follows Gazin (1942:486) in referring Dipodomys minor to the genus Prodipodomys, then the earliest member of the genus Dipodomys is D. gidleyi known from very late Pliocene or early Pleistocene deposits from Curtis Ranch, near Benson, Arizona. Setzer (1949:484) stated that D. spec- tabilis may have been the end product of the phyletic trend of D. gidleyi and that Prodipodomys? minor may have given rise to D. ordit. Thus, according to the available paleontological evidence, all modern species of Dipodomys were probably differentiated since late Pliocene or early Pleistocene. As many as three centers of dispersal for the species of the genus Dipodomys have been proposed. Setzer (1949:498) proposed that southwestern Nevada and southeastern California, south to the north- ern deserts of México was a major center and that the low, hot, in- terior valleys and adjacent foothills of central California was a second- ary center. Lidicker (1960:131) assumed that the high, dry, Mexican Central Plateau was a third minor center. As stated by Mayr (1963:386) , the original form of a species is usu- ally found in the central part of the range of the species, while the 100 KANGAROO RATS peripheral populations may deviate secondarily in different ways. Ac- cordingly, it is assumed that the region of origin and the center of dispersal of Dipodomys spectabilis was in southwestern New Mexico and adjacent parts of Chihuahua. This is the northern part of the third minor center of origin of the genus which was proposed by Lidicker (1960). D. spectabilis probably originated in the middle Pleistocene. From its place of origin, the following three patterns of dispersal are assumed to have taken place. These patterns are partly based on the relationships among the different recognized subspecies and partly conjectural. One route was in a westward direction to south central Arizona and adjacent parts of Sonora, giving rise to D. s. per- blandus. These populations are well differentiated and inhabit a some- what different terrain from that of the parental stock (open desert vs. desert grassland) . Later on, a southward invasion of these populations to west central Sonora resulted in the differentiation of D. s. inter- medius. A second route of dispersal from the center of origin of the species was in an eastward direction to central New Mexico and from there southeastward to western Texas and northwestward to north- western New Mexico and the adjacent area of northeastern Arizona. These populations comprise what is known now as D. s. baileyi. The third route was in a southeastward direction to south central Chihua- ~ hua giving rise to D. s. zygomaticus. From south central Chihuahua, the banner-tail invaded the lowlands of eastern Durango, and from there two routes were taken. A side route was taken in an eastward direction to west central Coahuila. From there it moved southeastward to southern Coahuila, northern Zacatecas, northern San Luis Potosi, and southern Nuevo Leon, and northwestward to northwestern Coa- huila and southeastern Chihuahua. These populations inhabited a somewhat drier environment than that typical for D. spectabilis, and after isolation gave rise to D. s. nelsoni, a well-marked subspecies of D. spectabilis. The main route, from eastern Durango, continued in a southeastward direction to central Zacatecas, western San Luis Potosi, and eastern Aguascalientes where these populations gave rise, after being isolated, to D. s. cratodon. Dipodomys deserti probably originated in early Pleistocene in the major center of origin of the genus, in southwestern United States, and most probably in southeastern California and the lower Colorado Desert. From the place of origin of this species, population dispersal probably took three main directions. The following patterns of dis- persal of the populations are assumed, in part, from the relationships among the different recognized subspecies and, in part, from conjec- PHYLOGENY OF THE TWO SPECIES 101 ture. One population took a north northwestward route resulting in the differentiation of D. d. aquilus in northwestern Nevada. A second route was mainly in an eastward direction to south central Arizona, which gave rise to D. d. arizonae. A small population invaded the east- ern banks of the Colorado River and moved northward, but did not reach the area now covered by Lake Mead. Populations on the eastern side of the Colorado River did not differentiate from the original pop- ulation of southeastern California. The third route was mainly south- eastward into northwestern Sonora and coastal areas of western So- nora, giving rise eventually to D. d. sonoriensis in west central Sonora. A small population invaded the northeastern coastal areas of Baja California. Populations in this region are still in direct contact with the parental populations in southeastern California and, although specimens from Baja California are slightly larger, they have not dif- ferentiated enough to become taxonomically distinct. D. spectabilis occupies throughout its range several different types of habitats, whereas D. deserti occupies an almost uniform habitat, which suggests that the limits of tolerance of D. spectabilis are much greater than those of D. deserti. Although D. spectabilis is assumed to have originated later than D. deserti, the present geographic range of spectabilis is approximately twice that of deserti. This indicates that the rate of dispersal of D. spectabilis has been greater than that of D. deserti. D. deserti seems to occupy, at the present, almost all of the suitable habitat available to it, and, unless a change in its habitat requirements takes place or changes occur in the enivornment itself, the geographic range of this species will not change appreciably from its present condition. In contrast, some range extension is to be ex- pected of D. spectabilis, especially in Sonora, Durango, Zacatecas, and San Luis Potosi due to the availability of some suitable habitat. The high degree of differentiation of most of the subspecies of D. spec- tabilis, in contrast with those of D. deserti, suggests that D. spectabilis has had a faster rate of evolution. Moreover, it seems that D. deserti is genetically more stable than D. spectabilis. This genetic instability of the latter species coupled with isolation and natural selection are believed to be important factors in its ability to adapt to different habitats and to give rise to more recognizable taxa than D. desertt. In comparing the extent of the geographic variation in the morphol- ogy of the two species studied, it appears that this variation is more extensive in D. spectabilis than in D. deserti. It is postulated that this is partly due to the availability of more varied habitat and to a longer period of isolation of some of the populations of D. spectabilis in con- 102 KANGAROO RATS trast with D. deserti. D. spectabilis gave rise in its evolutionary history to at least seven distinguishable living subspecies. These subspecies are at various levels of differentiation. Some are notably well differen- tiated and have nearly attained the specific level, as D. s. nelsoni, and to a slightly lesser degree as D. s. perblandus. Others are still less dif- ferentiated such as D. s. baileyi, D. s. cratodon, and D. s. spectabilis. The least differentiated is D. s. zygomaticus. Among the numerous factors responsible for the different degrees of divergence, the most important is the length of the period of geographic isolation. The zone of contact between D. s. nelsoni and D. s. zygomaticus is defined by a sharp shift in many character gradients and by a high degree of con- cordance in the characters studied which clearly indicate a secondary zone of intergradation. This zone most likely demonstrates that the contact between D. s. nelsoni and D. s. zygomaticus is relatively recent in the history of the species. D. s. nelsoni generally occupies an open desert type habitat which differs considerably from the range of the neighboring subspecies that occupy desert grassland. This difference in habitat probably further enhanced the differentiation of D. s. nel- soni. The high degree of divergence of this subspecies reflects a long period of isolation. The zone of intergradation between D. s. perblandus and D. s.— spectabilis also indicates secondary contact and strongly suggests a long period of isolation between these two subspecies. This zone is not so well defined as that between D. s. nelsoni and D. s. zygomaticus. The zone of contact between D. s. perblandus and D. s. spectabilis coincides closely with the presence of certain high ranges of mountains in southeastern Arizona—that is, the Empire, Santa Rita, and Pata- gonia mountains—which have been a highly effective barrier between the two subspecies. In general, D. s. perblandus occurs in low, open desert habitat, while D. s. spectabilis inhabits mixed desert grasslands at higher elevations. The different territory occupied by D. s. per- blandus probably further enhanced its differentiation. I). s. cratodon, which is presently isolated from the other subspecies, is not so well differentiated as either D. s. nelsoni or D. s. perblandus. It is likely that the geographic isolation of D. s. cratodon from its neighboring subspecies is more recent in the history of the species than that of either D. s. nelsoni or D. s. perblandus. Moreover, the habitat of D. s. cratodon, unlike that of the two aforementioned subspecies, does not differ appreciably from that of D. s. zygomaticus and D. s. spectabilis. Dipodomys deserti consists of only four recognizable subspecies al- PHYLOGENY OF THE TWO SPECIES 103 though the species itself originated in early Pleistocene, according to some authorities. Furthermore, the level of differentiation of each of these subspecies is not so great as that found among most of the sub- species of D. spectabilis. This low level of differentiation is attributed to the fact that throughout its entire range D. deserti inhabits an al- most uniform type of soil and encounters no effective geographic bar- riers that would permit isolation and differentiation. Also, D. deserti seems to have achieved a high degree of specialization for the type of habitat it occupies, which is reflected by its narrow limits of tolerance and by the presence of certain specializations in its morphology. It is thought that the inflation of the mastoidal bullae and the elon- gation of the hind feet are indications of the specialization and adapta- tion in D. spectabilis and D. deserti for open habitat and desert life. Some investigators have postulated that bullar inflation is an adapta- tion for saltation. Hatt (1932) suggested that the inflated auditory and mastoid bullae may shift the skull’s center of gravity backward and thus facilitate richochetal locomotion. Seton (1929) stated that the mastoid chambers contain some fluid and the mastoidal inflation is a specialization assisting in control of locomotion. Other investiga- tors suspected that bullar inflation is an adaptation for acute hearing and this has been proved by Webster (1962) in his experiments with D. merriami and D. spectabilis. It may be postulated that the larger the bullae are, in relation to skull size, the better the animal is adapted to jumping and balancing and also the better equipped for an open habitat. Bullar inflation is believed to permit more acute hearing in the special atmospheric conditions that affect the sound-transmitting properties of air in hot climates. This in turn increases the ability of the kangaroo rat to detect and avoid predators while they are stll some distance away. The elongation of the hind foot is an adaptation for the saltatorial mode of locomotion. Thus, the longer the hind feet are, in relation to the length of the body, the better the animal is adapted to this type of locomotion. To determine the degree of specialization of each subspecies in rela- tion to the other subspecies within the species, four indices are calcu- lated. They are the bullar index, cranial index, pedal index, and index of total specialization. The bullar index shows the degree of bullar inflation in relation to the breadth across the maxillary arches. ‘The cranial index shows the degree of mastoidal enlargement in relation to the greatest length of the skull. The pedal index shows the degree of hind foot elongation in relation to the length of the head and body. The index of total specialization shows the degree of specialization in 104 KANGAROO RATS each subspecies in regard to the three aforementioned indices. The four indices are presented in Tables 12 and 13 for D. spectabilis and D. deserti, respectively. According to the index of total specialization, it appears that D. s. nelsoni is the most specialized and D. s. inter- medius is the least specialized subspecies of the species D. spectabilis (Table 12). Also it appears that D. d. deserti is the most specialized and D. d. sonoriensis is the least specialized among the subspecies of D. deserti (Table 13). Setzer (1949:564) concluded that “In general, the most primitive kinds of D. ordit occur at the periphery of the range of the species,” and Lidicker (1960:206) stated that his study of D. merriami showed that “there is a definite tendency for the less specialized and presum- ably more primitive populations to inhabit the periphery of the range of the species.” The present study on D. spectabilis and D. deserti does not show any uniform tendency in the peripheral forms to be less spe- cialized in either of these two species. Also, this study shows that it is difficult to generalize that the peripheral or the central population is TABLE 12 Indices of specialization in Dipodomys spectabilis Subspecies in order of increasing total Bullar Cranial Pedal Total specialization D. 5s. intermedius 1.096 639 354 69.6 D.s. perblandus 1.103 639 358 70.0 D. s. spectabilis 1.115 639 364 70.6 D. s. baileyi 1.119 .636 365 70.6 D.s. zygomaticus 1.107 648 373 70.7 D.s. cratodon 1.102 652 372 70.8 D.s. nelsoni 1.185 636 368 129 TABLE 13 Indices of specialization in Dipodomys deserti Subspecies in order of increasing total Bullar Cranial Pedal Total specialization D. d. sonoriensis 1.268 667 362 76.56 D. d. arizonae 1.279 .668 374 77.36 D. d. aquilus 1.285 665 378 77.60 D. d. deserti 1.280 669 382 77.74 PHYLOGENY OF THE TWO SPECIES 105 the most specialized in a species. When a peripheral population be- comes isolated during the process of dispersal, it may differentiate secondarily to a more specialized or to a more generalized form than the parental population. Among the several factors that may influence this secondary differentiation are the length of the period of isolation, the degree of difference in the genetic constitution, and the habitat differences. Lidicker (1960) summarized the previous attempts to arrange the living species of the genus Dipodomys into a phylogenetic scheme and then presented his own. No such attempt has been made in the present study. But in order to determine how closely related D. spectabilis is to D. deserti, four indices were calculated for each species with use of the data presented in Tables 12 and 13 respectively. Also, the data from Setzer (1949:508) for D. ordi and from Lidicker (1960:207) for D. merriami were utilized and are presented in Table 14 along with those of D. spectabilis and D. deserti. From this table, three tentative conclusions can be drawn: (1) D. spectabilis is less specialized than D. deserti in all the indices studied; (2) D. deserti, besides being more specialized than D. spectabilis, is phylogentically far removed from it, contrary to what Lidicker (1960:134) had proposed; (3) D. desertz is the most specialized of the four species compared, and it is the most specialized species of the genus Dipodomys. On the basis of total specialization (based on averages of six indices) and comparison of the visceral arrangement, Setzer (1949) regarded D. deserti as the most specialized species of the genus Dipodomys and retained it in a separate group from D. spectabilis. Lidicker (1960) , considering all of the accumulated evidence together with his field experience, placed D. deserti in a separate subgroup within the Spec- tabilis Group. He suggested that it may, however, be desirable to re- TABLE 14 Indices of specialization in four species of Dipodomys Species in order of increasing total Bullar Cranial Pedal Total specialization D. ordii — 634 10 — (after Setzer, 1949) D. spectabilis 1.118 640 364 70.74 D. merriami 1.155 635 377 72.20 (after Lidicker, 1960) D. deserti 1.278 667 374 77.32 106 KANGAROO RATS tain D. deserti in a separate group following the Spectabilis Group. Burt’s (1960) study of the bacular morphology showed that the bacu- lum of D. spectabilis is very different from that of D. deserti. Most recently, in his study of the karyotypes of the genus Dipodomys, Stock (1974) also regarded D. deserti as the most specialized species of the genus. However, he placed it in a separate subgroup within the Heer- manni Group. He also found differences in the diploid number and in the morphology of the chromosomes of D. spectabilis and D. deserti. According to the indices arrived at in this study along with the available evidences which illustrate the differences between D. spec- tabilis and D. deserti, this latter species should be retained in a sepa- rate Deserti Group. Moreover, because of the high degree of special- ization of D. deserti, the Deserti Group should be kept at the end of the phylogenetic scheme of the genus as it has been in earlier schemes. SUMMARY This study is based on the examination of 2,725 specimens from 689 localities of both Dipodomys spectabilis and Dipodomys desertt; 1,187 specimens from 368 localities for D. spectabilis and 1,538 specimens from 321 localities for D. deserti. Fourteen skull measurements and six external measurements were studied and the color of each speci- men was analyzed. ‘The two species are characterized and notes are given about their habitat, longevity, predators, parasites, and molt. In each of the two species, the adults undergo one molt a year, usually in August for D. spectabilis and in July for D. desertz. Notes on reproductive activities of both species are given. There is a slight difference in the length of the period of these activities and in the number of embryos per month between the northern and the southern populations in D. spectabilis. The period is longer and the number of embryos is larger in the southern populations. No such differences are found in D. deserti. The mean of the litter size in D. deserti is larger than that in D. spectabilis. Color of the pelage in D. spectabilis is more stable than it is in D. desertt. The color in deserti seems to be correlated with the color of the soil. The age of each specimen was determined primarily on the basis of tooth wear and the translucence of some of the skull bones. Five age-groups are recognized in D. spectabilis: juvenile, immature, sub- adult, young adult, and old adult, while in D. desert: four age-groups are recognized: juvenile, immature, subadult, and adult. No signifi- cant differences are found between the young adult and the old adult age-groups in D. spectabilis. In the statistical treatment and in the analysis of the infraspecific variation, only the adults are considered. Notes on dentition and the pattern of wear on the occlusal surface in each of the two species are given. 108 KANGAROO RATS Variation within a population is analyzed and the coefficient of vari- ation is calculated for each measurement studied for both species. No significant secondary sexual dimorphism is present in D. spectabilis, although noteworthy differences are found in nine measurements in D. deserti. Clinal variation is not clear from the measurements of D. spectabilis, whereas some of the measurements in D. deserti show some degree of clinal change in a north-south direction. Nasal length and rostral depth increase in size in this direction, and this is thought to be correlated with the temperature and humidity of the environment. Geographic variation is more evident in D. spectabilis than in D. deserti although the latter is thought to have originated earlier. It is thought that this is due to the availability of more varied habitat and a longer period of isolation of some of the populations of D. spec- tabilis in contrast with D. deserti. The low degree of variability throughout the range of D. deserti is ascribed to the uniformity of the habitat, the absence of effective geographic barriers, and its narrow limits of tolerance. Seven subspecies of D. spectabilis and four subspecies of D. deserti are recognized and formally diagnosed. D. s. nelsoni, formerly re- garded as a full species, is herein regarded as a subspecies of D. spec- tabilis; D. s. clarencei is regarded as a consubspecific with D. s. baileyi. Notes on the fossil history of the genus in general and of D. spec- tabilis and D. deserti in particular are given. It is assumed that D. spectabilis originated in the northern part of the Mexican Central Plateau and D. deserti in southeastern California. A pattern of dis- persal for each of these two species is proposed. Four indices are calculated for each subspecies of the two species and then for each species to determine their degree of specialization for acute hearing and for saltation. The data arrived at in this study do not show, in either of the two species, any uniform distribution of the less specialized or the more specialized subspecies within the range of each species. Within D. spectabilis, the most specialized subspecies is D. s. nelsoni, and the most generalized is D. s. intermedius. 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McGraw-Hill Book Co., Inc., New York. vii+336 p. McAtee, W. L. 1921. Farm help from the birds. In Yearbook U. S. Dept. Agr. 1920, p. 253-270. Merriam, C. H. 1890. Description of three kangaroo rats, with remarks on the identity of Dipodomys ordiit of Woodhouse. N. Am. Fauna 4:41—49. 1907. Description of ten new kangaroo rats. Proc. Biol. Soc. Washington 20:75—80. Miller, G. S., Jr. 1912. List of North American land mammals in the United States Na- tional Museum, 1911. U. S. Natl. Museum Bull. 79:xiv+455 p. Monson, G. 1943. Food habits of the banner-tailed kangaroo rat in Arizona. J. Wildl. Memt. 7:98-102. LITERATURE CITED 113 Nader, I. A. 1965. Two new subspecies of kangaroo rats, genus Dipodomys. Proc. Biol. Soc. Washington 78:49—54. 1966. Roots of teeth as a generic character in the kangaroo rats, Dz- podomys. Bull. Biol. Res. Centre, Baghdad 2:62-69. Packard, R. L., and F. W. Judd 1968. Comments on some mammals from western Texas. J. Mammal. 49:535—538. Ramsey, P. R., and C. J. Carley 1970. Additions to the known range and ecology of three species of Dipodomys. Southwestern Naturalist 14:351—353. Ridgway, R. 1912. Color standards and color nomenclature. Published by the author, Washington, D.C. ii+43 p. Seton, E. T. 1929. Lives of game animals. Doubleday, Doran and Co., Garden City, New York. 4 (Pt. 1) :440 p. Setzer, H. W. 1949. Subspeciation in the kangaroo rat, Dipodomys ordi. Univ. Kan- sas Publ., Museum Nat. Hist. 1:473—573. Stephens, F. 1887. Description of a new species of Dipodomys with some account of its habits. Am. Naturalist 21:42—49. Stock, A. D. 1974. Chromosome evolution in the genus Dipodomys and its taxonomic and phylogenetic implications, J. Mammal. 55:505—526. Villa, B. R. 1941. Nota acerca de algunas especies de roedores de los géneros Di- podomys, Perognathus y Peromyscus. An. Inst. Biol. Mexicana 12:355-399. Vorhies, C. T., and W. P. Taylor 1922. Life history of the kangaroo rat, Dipodomys spectabilis spectabilis Merriam. U. S. Dept. 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INDEX Abbreviations, museums, 7—8 Age-groups: determination, 5-6, 107; D. deserti, 72-74; D. spectabilis, 16-18 Bubo virginianus, 1) Canis latrans, 11 Chigger, 11 Climate, effect on nasal length and rostral depth, 108 Coefficients of variation, 5,21 (Table 14) , 76 (Table 9) Coloration, 3, 9, 11, 15-16, 31, 65, 71-72, 85, 86, 92, 97, 107 Crotalus, 11 Ctenophthalmus, 11 Dentition, 16-21, 69, 72—75, 86, 107 (see also Tooth) Deserti Group, 108 Differentiation, morphological, 61, 101-102, 103; secondary, 105 Dipodomyinae, 1 Dipodomys gidleyi, 99 Dipodomys merriami, 1, 11, 28, 67, 68, 103, 104, 105 D. m. mayensis, 28 Dipodomys microps, 1, 67 Dipodomys minor, 99 Dipodomys ordit, 1, 11, 67, 80, 99, 104, 105 Dipodomys panamintinus, 67 Dipodomys spectabilis clarencei, 43, 44, 108 Ectoglenoid fossa: D. deserti, 65; D. spectabilis, 9 Embryos: D. deserti, 69, 70; D. specta- bilis, 13, 14 Endoparasites, 11, 68 Environment, effects of temperature and humidity, 108 Fahrenholzia pinnata, 68 Fleas, 11, 68 Geographic variation: D. deserti, 77, 79-80; D. spectabilis, 25, 28 (see also Variation) Gestation: D. deserti, 69; D. spectabilis, 15 Habitat, 65-67, 86, 95, 98, 101, 102, 103, 105, 108 Hearing, acute, 108; and bullar inflation, 103 Heermanni Group, 106 Heteromyidae, | Hybridization, 57 Hyoid apparatus; D. deserti, 65; D. spectabilis, 11 Indices, 6, 104, 105 Intergradation, 31, 32, 37, 41, 50, 52, 55, 58, 59 (Fig. 9) , 60-61, 85, 92, 95,97, 102 S Karyotypes, 60, 106 Lice, 68 Litter size: D. deserti, 69; D. specta- bilis, 14 Locomotion, 103, 108 Longevity: D. deserti, 67-68; D. spectabilis, 11 Lynx rufus baileyt, 11 Masticophis flagellum, 11 Measurements, 3—5 Mephitis, 11 INDEX Meringis parkeri, 68 Merriam’s kangaroo rat, 22 Molting, 107; D. deserti, 68; D. spectabilis, 11-12 Museums, 7-8 Pelage, 1, 15, 18, 72 Pituophis, 11 Prodipodomys rexroadensis, 99 Range: D. deserti, 81, 82 (Fig. 14), 86, 92, 94, 96, 101-102; D. spectabilis, 29, 35-36, 40, 42, 48, 56-58, 60-61, 77, 101; pattern variation, 23, 99-100 Ridgway, color terminology (pelage) , 3 Saltation, 103, 108 Secondary sexual dimorphism: D. deserti, 77; D. spectabilis, 22-23 Specialization, indices of, viii, 1, 6, 103, 104, 105, 106 A Note on the Author 116 Supraoccipital: least breadth of, 5; variation in, 22, 31, 76 Synonymy, 6 Taxidea taxus, 11 Taxonomy, I, 45, 55, 86, 101, 105-106 Thrassis (Thrassoides) hoffmant, 68 Tooth eruption: D. deserti, 74; D. spectabilis, 18, 20; type: Kleistodont, 65; Opaeodont, 9 Trombicula, 11 Tyto alba, 11, 68 Variation: age, 16, 72 coefficients of (q. v.) geographic: D. deserti, 65, 80, 101, 108; D. spectabilis, 11, 23, 101, 108; maps, 26-27 Vulpes macrotis, 11, 68 Iyap A. NaApDER was born in 1934 in Baghdad, Iraq. He received his B.S. with honors from the University of Baghdad and his M.S. and Ph.D. (1964) from the University of Ilinois. In addition to teaching at the University of Baghdad, he was the director of the Biological Research Center in Baghdad from 1967 to 1971. Presently he is a professor of zoology and chairman of the De- partment of Sciences at the College of Education at Abha, Uni- versity of Riyadh. He has published more than thirty scientific papers and books. a x aX 4 a i 3: : 4 Ff = ae 6 bs f wiih: j = ae : % : f = x ‘ i E \ hy ey : ‘ % . Z i f Z 2 ? ~ ~ ci : - * ‘ Ks 1 geok i 3 Ao ‘ * Shere eng pe 4s aoe y pty 2 f i i re : - f . é “ : s = Wh 2 = * ¥ i © ry E jem 3 P < J wens = ye che Pe i oath » a: ee x ro