Sonoran Desertscrub Research Articles

Coordination of hydraulic and functional traits in ten species of trees of the Sonoran Desert

Leave’s vein xylem and stomata hydraulic traits should be critically linked to modulating plant responses to drought in leaves of desert species, influencing traits at the whole-plant level and promoting adaptation. We tested for coordination among leaf vein xylem anatomical traits across different hierarchical orders (hydraulic vessel diameter, vein area, free veins per area, areolas per area, total free veins number, total areola number) and stomatal traits (stomatal size, stomatal density, stomatal index, leaf total stomatal area, leaf total stomatal number) as well as their relationship with the leaf area in ten tree species from the Sonoran Desert scrub, Mexico. Moreover, these traits were correlated with other hydraulic and functional traits associated with resource use strategies (hydroscape area, stem-specific density, leaf mass per area, and leaf phenology). Leaf total stomatal area and number were positively associated with vessel diameters at the midrib and with leaf total free terminal veins and areola number, indicating coordination between water transpiration and transport. Also, interspecific differences fit species along a physiological resource use spectrum, following an exploitative vs. conservative physiological axis. Accordingly, species with lower leaf longevity (LL) and foliage duration at the canopy (FD) displayed higher values of stomatal indices and free vein densities, higher stomata density; and anatomical traits related to higher hydraulic conductance and gas exchange in comparison to species with higher LL and FD. Therefore, in this community, species have been selected to take advantage of different temporal hydrological niches to enhance survival under unpredictable and highly seasonal water availability.

Triggering rainfall intensities for post-wildfire debris flows in the Sonoran Desertscrub plant community

Wildfire makes landscapes more vulnerable to debris flows by reducing soil infiltration capacity and decreasing vegetation cover. The extent to which fire affects debris-flow processes depends on the severity of the fire, the climatology of intense rainfall, the pre-fire plant community, and sediment supply, among other factors. As fire expands into new plant communities and geographic regions, there is a corresponding need to expand efforts to document fire-induced changes and their impacts on debris-flow processes. In recent years, several large wildfires have impacted portions of the Sonoran Desertscrub plant community in Arizona, USA, a plant community where fire has been historically infrequent. Following two of these fires, we monitored debris-flow activity at the watershed scale and quantified wildfire-driven changes in soil hydraulic properties using in-situ measurements with mini disk tension infiltrometers. Results indicate that rainfall intensity-duration thresholds for the initiation of post-fire debris flows in recently burned watersheds within the Sonoran Desertscrub plant community are substantially greater than those in nearby areas dominated by other plant communities, such as chaparral. Results provide insight into the impact of fire on debris-flow processes in a plant community where it is likely to be more impactful in the future and help expand existing post-fire debris flow databases into a plant community where there is a paucity of observations.

Updates of Historic and Contemporary Records of Jaguars (Panthera onca) from Arizona

We summarize >80 accounts of jaguars killed and/or photographed in Arizona during a 160-year period. These accounts include 13 previously unrecorded animals and six contemporary photographic records. The period with most records occurred between 1900 and 1920. Occurrences ranged from Sonoran desertscrub < 1000 m ASL to mixed confer forest at 2,134 m ASL. Every county in Arizona save four had jaguar records and distribution of records indicate a north by northwest movement along montane corridors from the southeastern quarter of the state northwest to the Grand Canyon. Three counties bordering Sonora yielded numerous records over protracted periods, namely Santa Cruz, Cochise, and Pima Counties. The distribution, number of occurrences and records of females and sub-adults before 1920 suggest some animals may have been breeding residents.

Population Surveys and Viability Assessments for Coryphantha scheeri var. Robustispina, a Federally Protected Cactus of the Sonoran Desert

Coryphantha scheeri var. robustispina (Pima pineapple cactus [PPC]; Cactaceae) is a small cylindrical cactus found in semi-desert grassland and Sonoran desert-scrub in southern Arizona and northern Mexico. This species was listed as endangered in 1993 in the USA, but does not have protection in Mexico. In 2017, surveys were repeated at six PPC sites with a long monitoring history within the Altar Valley, Pima County, Arizona. Overall, PPC individuals were found at five of the six sites (i.e., 83%). Although PPC is persisting at most sites and recruitment was observed at some sites, the overall pattern was one of decline within the surveyed area. In addition, population viability analyses predict that four sites will lose more than half of their individuals within 20 y, and five sites within 50 y. The information presented in this study should be useful for making decisions regarding federal protection for Coryphantha scheeri var. robustispina.

Leaf water relations reflect canopy phenology rather than leaf life span in Sonoran Desert trees.

Plants from arid environments display covarying traits to survive or resist drought. Plant drought resistance and ability to survive long periods of low soil water availability should involve leaf phenology coordination with leaf and stem functional traits related to water status. This study tested correlations between phenology and functional traits involved in plant water status regulation in 10 Sonoran Desert tree species with contrasting phenology. Species seasonal variation in plant water status was defined by calculating their relative positions along the iso/anisohydric regulation continuum based on their hydroscape areas (HA)-a metric derived from the relationship between predawn and midday water potentials-and stomatal and hydraulic traits. Additionally, functional traits associated with plant water status regulation, including lamina vessel hydraulic diameter (DHL), stem-specific density (SSD) and leaf mass per area (LMA) were quantified per species. To characterize leaf phenology, leaf longevity (LL) and canopy foliage duration (FD) were determined. Hydroscape area was strongly correlated with FD but not with leaf longevity (LL); HA was significantly associated with SSD and leaf hydraulic traits (DHL, LMA) but not with stem hydraulic traits (vulnerability index, relative conductivity); and FD was strongly correlated with LMA and SSD. Leaf physiological characteristics affected leaf phenology when it was described as canopy FD better than when described as LL. Stem and leaf structure and hydraulic functions were not only relevant for categorizing species along the iso/anisohydric continuum but also allowed identifying different strategies of desert trees within the 'fast-slow' plant economics spectrum. The results in this study pinpoint the set of evolutionary pressures that shape the Sonoran Desert Scrub physiognomy.

Comparisons of Reptile Assemblages in Two Subdivisions of the Sonoran Desertscrub Biotic Community

Anthropogenic disturbances can have negative effects on species assemblages. This study was established to form baseline data on the environmental structure and reptile assemblages within a planned energy corridor in Pinal County, Arizona, prior to construction. We emphasized evaluating the differences in reptile assemblages in two subdivisions of the Sonoran Desertscrub, the Lower Colorado River Valley (LCV) and Arizona Uplands (AZU). Surveys were conducted on 50 sites (LCV = 15; AZU = 35) along the proposed 67.1-km long energy corridor through environmental surveys and 50 drift-fence trapping arrays with 400 box funnel traps. Vegetation height, number of burrows, and percent rock, ground cover, and coarse woody debris were significantly higher in the AZU than in LCV. Eighteen reptile species (n = 995 captures) were detected on the energy corridor including 8 lizard species (n = 952 captures) and 10 snake species (n = 43 captures). Species richness, evenness, and capture rates were not significantly different between the LCV and AZU; however, species diversity was significantly higher in the LCV. Reptile abundance (LCV = 281; AZU = 714) differed in the two subdivisions, yet rank-abundance curves revealed no difference in dominance of species. Post hoc examination revealed that the geographic separation of sites within the LCV and the location of the study area (along the ecotone) may have contributed to our results. We conclude that both subdivisions are equally important to the maintenance of local biotic diversity and recommend that any future land set-asides consider both subdivisions.

Shaping species with ephemeral boundaries: the distribution and genetic structure of desert tortoise (Gopherus morafkai) in the Sonoran Desert region

AbstractAimWe examine the role biogeographical features played in the evolution of Morafka's desert tortoise (Gopherus morafkai) and test the hypothesis that G. morafkai maintains genetically distinct lineages associated with different Sonoran Desert biomes. Increased knowledge of the past and present distribution of the Sonoran Desert region's biota provides insight into the forces that drive and maintain its biodiversity.LocationSonoran Desert biogeographical region; Sonora and Sinaloa, Mexico and Arizona, USA.MethodsWe examined wild tortoises from Mexico (n = 155) and Arizona (n = 78), spanning their known distribution. We used mtDNA sequences to reconstruct matrilineal relationships and 25 microsatellite (STR) loci for Bayesian analyses of gene flow. We performed clinal analyses on both mtDNA and STR loci to determine the position and amount of introgression where lineages co‐occur. We used GIS to assess the association of genetic structuring with ecological features. We used these data in a hypothesis‐driven approach to assess different models of how genetic diversity is maintained and distributed in G. morafkai.ResultsGopherus morafkai was found to comprise genetically and geographically distinct ‘Sonoran’ and ‘Sinaloan’ lineages. Both lineages occurred in a relatively narrow zone of overlap in Sinaloan thornscrub, where it transitions into Sonoran desertscrub. Limited introgression occurred at the contact zone. The best‐fit model suggests that these lineages diverged in parapatry where the distribution of genotypes is environment‐dependent and introgression is inhibited by exogenous selection.Main conclusionsThe historically shifting ecotone between tropical deciduous forest and Sonoran desertscrub appears to be a boundary that fostered divergence between parapatric lineages of tortoises. The sharp genetic cline between the two lineages suggests that periods of isolation in temporary refugia due to Pleistocene climatic cycling influenced divergence. Despite incomplete reproductive isolation, the Sonoran and Sinaloan lineages of G. morafkai are on separate evolutionary trajectories.

Amphibians and Reptiles of the Madrean Archipelago of Arizona and New Mexico

The Madrean Archipelago in southern Arizona and southwestern New Mexico consists of 22 mountain ranges south of the Mogollon Rim. Herpetofaunal lists for these ranges and a segment of the rim were constructed based on museum specimens from Madrean evergreen woodland, petran montane conifer forest, and interior chaparral. Few or no species have been recorded from these communities in the Sierrita, Little Dragoon, and Big Hatchet mountains, emphasizing the need for additional sampling in the archipelago. A total of 83 species are found in the remaining 20 ranges, with lizards (28) and snakes (35) predominating. No two mountain ranges had the same herpetofauna. Species richness varies from 15 to 44 (mean 28.1). Phenetic analyses of herpetofaunal similarity among the ranges identify three groups: a northern group with eight ranges from the Rincon Mountains to the Pinaleño Mountains to the Sierra Ancha; a southwestern group consisting of the Baboquivari, Santa Rita, Pajarito, and Patagonia mountains; and a southeastern group with seven ranges from the Huachuca and Whetstone mountains to the Animas Mountains; the Mogollon Rim segment is placed as the first “branch” of the phenogram. The analyses place the Patagonia Mountains in the SW group and the Huachuca Mountains in the SE group, although the two are connected by woodland. The Madrean line separating the northern group from the two southern groups approximates the southern limit of interior chaparral. The ranges of the southwestern group are in contact with semitropical Sonoran desert scrub at low elevations, whereas Chihuahuan desert scrub and semidesert grassland surround the southeastern ranges. With few exceptions, published studies of phylogeography within species suggest that divergence among montane populations in the archipelago does not predate the Pleistocene. Phylogeographic analyses using nuclear and mitochondrial gene sequences and including all ranges of the Madrean Archipelago inhabited by a species are needed to determine the extent to which shared historic biogeographic events may underlie the groups of mountain ranges identified on the basis of herpetofaunal similarities in this study.

The herpetofauna of Sonora, Mexico, with comparisons to adjoining states

Situated in the topographically complex transition between the Neotropics and the temperate biomes of North America, the state of Sonora, Mexico, has an extraordinarily diverse herpetofauna. Surprisingly little research has been conducted on the state’s amphibians and reptiles and many systematic and biogeographic questions remain unanswered. To facilitate future research, we provide a checklist of Sonora’s herpetofauna, documenting species presence based on museum specimens, our fieldwork, and published research. Sonora’s herpetofauna is placed in a regional biogeographic perspective via a checklist for the six adjoining states together with faunal analyses. A total of 402 species of amphibians and reptiles are recorded from these seven states. Sonora has the greatest species richness (187 species), followed by Chihuahua (169 species), and Sinaloa (146 species). Sonora's herpetofauna is most similar to that of Chihuahua, with which it shares a long border. Eleven biogeographic affinity-based faunal groups are recognized. Of these, three are dominant in Sonora: a core group classified as "Sonoran" demonstrates strong affinity to Sonoran Desertscrub and Sinaloan Thornscrub communities; a Tropical group - with many species reaching their northern distributional limits in the state; and a Madrean group consisting largely of montane species. Our state-level faunal analysis provides some evidence of peninsular depauperization of the herpetofauna on the Baja California peninsula due in part to the small number of Neotropical species present in Baja California Sur. Our faunal analysis points toward distinctive mainland and peninsular Sonoran Desert herpetofaunas centered on Sonora and the Baja California Peninsula, respectively, each with about 50 non-insular species, and each with species-level endemism nearing 50%.

Land use changes affect distributional patterns of desert birds in the Baja California peninsula, Mexico

AbstractReliable plans for desert bird conservation will depend on accurate prediction of habitat change effects on their distribution and abundance patterns. Predictive models can help highlight relationships between human‐related and other environmental variables and the presence of desert bird species. Presence/absence of 30 desert bird species of Baja California peninsula was modelled on the basis of explanatory variables taken from the field, maps, and digital imagery. Generalized linear models were fit to each bird species using both variables representing human activity and other environmental factors as predictors that might influence distribution. Probability of species presence was used as a habitat suitability index to evaluate the effect of human activity when the model contained a significant human activity variable. No differences were found in bird species richness between natural sites and those transformed by agriculture or urbanization. Of 59 bird species recorded in surveys, 34% were positively or negatively associated with human‐transformed habitats. Fourteen species seem to benefit from transformation of natural vegetation by agriculture or urbanization, while six were negatively affected. Sensitivity analyses of final models indicated all were robust. Results suggest that the occurrence of a large percentage of bird species inhabiting scrub habitats is sensitive to human habitat transformation. This finding has important conservation implications at regional scale as fragmentation and conversion of desert ecosystems into agricultural and urban areas affect the distribution of species that are highly selective for scrub habitat. Land use and anthropogenic activities seem to change ecological patterns at large spatial scales, but other factors could drive species richness distribution too (i.e. individual species response, species–energy relationships). The spatial modelling approach at regional scale used in this study can be useful for designing natural resource management plans in the Sonoran desert scrub.

Breeding Phenology of the Lowland Leopard Frog (Rana yavapaiensis): Implications for Conservation and Ecology

Breeding Phenology of the Lowland Leopard Frog (Rana yavapaiensis): Implications for Conservation and Ecology

A 22,000-year record of vegetation change in the north-central Sonoran Desert

Plant macrofossils from eleven packrat ( Neotoma sp.) middens provide a history of vegetation change over the last 22,140 years at Eagle Eye Mountain, near the northern border of the Sonoran Desert in Arizona. This site is located in the Arizona Upland subdivision. Departures and arrivals of various perennial plant species during the Holocene were similar to other records from more southerly sites and support earlier generalizations of Van Devender [Van Devender, T.R., 1990. Late Quaternary vegetation and climate of the Sonoran Desert, United States and Mexico. In: Betancourt, J.L., Van Devender, T.R., Martin, P.S. (Eds.), Packrat Middens: The Last 40,000 Years of Biotic Change. University of Arizona Press, Tucson, pp. 134–165.] regarding the tempo and mode of late Quaternary changes in the Arizona Upland. Evergreen woodland containing Pinus monophylla (singleleaf pinyon), Juniperus osteosperma (Utah juniper), and Quercus turbinella (shrub live oak) occupied the site during full glacial times. The latter two species, but not P. monophylla, persisted into the early Holocene and were joined by a limited number of desertscrub species, including Acacia greggii (catclaw), Carnegiea gigantea (saguaro), and several other succulents. With the arrival of many other species during the middle Holocene, a desertscrub community that differed considerably from the modern vegetation developed. Acacia greggii and Cercidium floridum (blue paloverde) were the principal large woody species on exposed hillslopes. Assemblages similar in composition to the modern desertscrub did not appear until approximately 4000 years ago, when the more xerophytic Cercidium microphyllum (foothills paloverde) arrived and C. floridum disappeared from hillslopes. The delayed arrival of C. microphyllum in comparison to other Sonoran Desertscrub species with similar climatic tolerances is attributed to the limited dispersal distance of its seeds by seed-eating heteromyid rodents. At 4540 and 6425 yr B.P., the cold-intolerant shrub Encelia farinosa was present on northeasterly aspect exposures where it is absent today, suggesting slightly warmer winter conditions during the middle Holocene. The presence of the tree Cercidium floridum and the perennial, C-4 grass Setaria leucopila on exposed slopes during the middle Holocene indicates substantially moister conditions during that time than in the late Holocene or today. At sites on the xeric limits of the modern distributions of both species, average annual precipitation is from 50% to 100% greater than that presently received at Eagle Eye Mountain. In particular, the responses of S. leucopila and cacti during the middle Holocene indicate substantial increases in warm-season precipitation.

Successive pot cultures reveal high species richness of arbuscular endomycorrhizal fungi in arid ecosystems

Three cycles of successive trap cultures were utilized to determine the taxonomic structure of arbuscular fungi associated with mesquite (Prosopis spp.) from three locations in the Sonoran desertscrub biotic community and one location in the Chihuahuan desertscrub biotic community. Unlike the low species richness found in previous studies of some arid habitats, seven to nine species were recovered from each sampling site. This number is comparable to that found in many other plant communities. Seventy-five percent of the species found after three culture cycles were not detected in the first trap cultures, suggesting that a high proportion of arbuscular fungi in arid habitats may be nonsporulating in the field. Low colonization levels may account for the absence of sporulation, but ecological factors such as moisture limitations also may be involved. Although a total of 10 different species was detected, generic richness was limited, with 9 of these species in Glomus and 1 in Entrophospora. As long as measurement of species richness is based on occurrence of sporulation, successive trap cultures provide a means of detecting nonsporulating mycorrhizal colonizers in arid and other habitats. Keywords: vesicular – arbuscular mycorrhizae, ecology, desert, Glomales.

Speciation in the Desert Pocket Mouse (Chaetodipus penicillatus Woodhouse)

Variation in mitochondrial DNA was studied across the range of Chaetodipus penicillatus . Sequence data from the COIII gene and restriction-enzyme analysis of a 2,150 base pair fragment indicated a significant genetic demarcation between samples assigned to C. p. pricei and those assigned to C. p. eremicus . Sequence and restriction data also show that populations assigned to C. p. eremicus share a common history not shared by populations assigned to C. p. pricei . These data are concordant with independent evidence from nuclear data of divergence among populations of C. penicillatus at protein and chromosomal levels. Furthermore, the overall pattern of phylogeographic population structure in C. penicillatus is consistent with an hypothesis of long-term isolation and divergence of Chihuahuan and Sonoran desertscrub biotas. We recommend that C. p. eremicus be recognized as a distinct species. The appropriate binomial for populations thus far examined from the Chihuahuan Desert is Chaetodipus eremicus .

Paleoclimatic Implications of Holocene Plant Remains from the Sierra Bacha, Sonora, Mexico

A total of 93 plant taxa were identified from 11 packrat ( Neotoma sp.) midden samples from the Sierra Bacha on the coast of the Gulf of California near Puerto Libertad, Sonora, Mexico. Nine indurated samples have radiocarbon dates ranging from 9970 to 320 yr B.P. Sonoran desertscrub was present on rocky slopes throughout the Holocene. Early Holocene assemblages dominated by Fouquieria columnaris (boojum tree) reflect vegetation and climate more like modern Baja California with greater winter rainfall and cooler summers. Middle Holocene vegetation was essentially modern with modest indications of greater monsoonal rainfall even though cold-water upwelling locally inhibits summer precipitation. The results are similar to all previous midden reconstructions of early and middle Holocene climates in the Sonoran Desert, but contradict general atmospheric circulation model simulations.

Comparison of pollen and macrofossils in packrat ( Neotama) middens: A chronological sequence from the Waterman mountains of southern Arizona, U.S.A.

Pollen percentages in moss polsters and soil samples were compared with percent plant cover along 30-m transects in desertscrub vegetation, Waterman Mountains, Arizona, in the northeastern Sonoran Desert. These data were used to interpret pollen assemblages and associated plant macrofossils from 14 packrat ( Neotoma sp.) middens radiocarbon dated from 1320 to 22,450 yr B.P. A macrofossil: pollen index ( MPI) was used to compare the presence and relative abundances of pollen and macrofossils in midden samples. In general, pollen and macrofossils from Sonoran Desert middens reflect similar vegetation signals. Calculation of Sørensen's Similarity Index ( SI) comparing the presence of midden pollen and macrofossils indicates greater similarities for Sonoran desertscrub than pinyon-juniper woodland. SI values from the Waterman series are greater for all age samples, compared to samples from other desert locations, perhaps reflecting greater species richness and summer rainfall in the northeastern Sonoran Desert. The pollen and macrofossil assemblages reflect a middle and late Wisconsin (22,450-ca. 11,500 yr B.P.) pinyon-juniper woodland with sagebrush and Joshua tree on limestone slopes. A transitional early Holocene juniper woodland/chaparral was replaced by 8900 yr B.P. by a mesic Sonoran desertscrub of saguaro, catclaw acacia, blue paloverde and velvet mesquite. The presence of the latter three on exposed rocky locations, now restricted mostly to riparian washes, indicates moister conditions during the middle Holocene than today. Essentially modern vegetation developed by ca. 4000 yr B.P. Changes over the last ca. 1300 years suggest that modern climate is the most xeric in the entire record.

Holocene Vegetation and Climate in the Puerto Blanco Mountains, Southwestern Arizona

AbstractPlant macrofossils from 21 pack rat (Neotomasp.) middens at 535–605 m from the Puerto Blanco Mountains, southwestern Arizona, provide and excellent history of vegetation and climate for the last 14, 120 yr B.P. in the Sonoran Desert. A late Wisconsin juniper-Joshua tree woodland gave way to a transitional early Holocene desertscrub with sparseJuniperus californica(California juniper) by 10,540 yr B.P. Important Sonoran Desert plants includingCarnegiea gigantea(saguaro) andEncelia farinosa(brittle bush) were dominants. Riparian trees such asAcacia greggii(catclaw acacia),Prosopis velutina(velvet mesquite), andCerdicium floridum(blue palo verde) grew on dry, south-facing slopes in a middle Holocene Sonoran desertscrub in a warm, wet summer climate with frequent winter freezes. Modern subtropical Sonoran desertscrub formed about 4000 yr B.P. as summer rainfall and winter freezes declined.Cercidium microphyllum(foothills palo verde),Sapium biloculare(Mexican jumping bean),Olneya tesota(ironwood) andStenocereus thurberi(organ pipe cactus) became dominant as riparian trees retreated to wash habitats. The inferences of a latest Wisconsin/early Holocene summer monsoonal maximum by J. E. Kutzbach (1983), Modeling of Holocene climates.In“Late-Quaternary Environments of the United States,” Vol. 2, “The Holocene” (H. E. Wright, Ed.), pp. 271–277. Univ. of Minnesota Press, Minneapolis) are not supported for the Southwest. Apparently the persistence of late Wisconsin circulation patterns offset any increases in insolation.

The lower Colorado River Valley: A Pleistocene desert

A chronological sequence of plant macrofossil assemblages from twenty-five pack rat middens provides a record of desert scrub vegetation for most of the last 13,380 yr B.P. from a hyperarid portion of the lower Colorado River Valley. At the end of the late Wisconsin, and probably during much of the Quaternary, the Picacho Peak area, Imperial County, California, supported a typical Mohave Desert association of Larrea divaricata (creosote bush), Coleogyne ramosissima (blackbrush), Yucca brevifolia (Joshua tree), and Y. whipplei (Whipple yucca). Recent arrivals of Sonoran Desert plants such as Olneya tesota (ironwood) and Fouquieria splendens (ocotillo) suggest that the area supported relatively modern Sonoran desert scrub species for relatively short periods during interglaciations.

Haematosiphon inodorus (Hemiptera: Cimicidae) in a Nest of a Bald Eagle (Haliaeetus leucocephalus) in Arizona

Haemutosiphon inodorus (Duges), the Mexican chicken bug, is a bloodsucking ectoparasite recorded from only nine species of birds of prey (Falconiformes and Strigiformes) and domestic fowl (Galliformes): California condor (Gymnogyps californiunus Shaw), turkey vulture (Cathartes aura Wied), golden eagle (Aquila chrysaetos L.), red-tailed hawk (Buteo jamaicensis Gmelin), prairie falcon (Falco mexicanus Schlegel), great horned owl (Bubo virginianus Gmelin), barn owl (Tyto alba Bonaparte), domestic chicken (Callus gallus L.), and domestic turkey (Meleagris gallopavo L.) (see Wilson and Oliver, 1978, Southwest. Nat. 23: 305307). The Mexican chicken bug is relatively uncommon in southwestern U S A . (Usinger, 1966, Monograph of Cimicidae, Horn Shafer Co., Baltimore, Maryland, 585 pp.; Lee, 1955, Pan-Pac. Entomol. 31: 137-138; Wilson and Oliver, 1978, op. cit.). The USDA Cooperative Extension Service and the Insect Identification Laboratory of the Arizona State Agriculture Commission have no reports of any serious infestations on domestic poultry in Arizona. This note documents the first recorded occurrence of H. inodorus in an active nest of a bald eagle in sufficient numbers to have caused or contributed to the death of two eaglets. The eagle nest was located in east-central Arizona in Sonoran desertscrub habi-

Bobcat Lynx rufus Home Range, Density and Habitat Preference in South-Central Arizona

-Home range size, density, and habitat preference was estimated for a bobcat population on a portion of the Three Bar Wildlife Area, Arizona. Five adult females and two adult males were radio-located 394 times between September 1976 and January 1978. Female and male home ranges averaged 4.8 km2 and 9.1 km2, respectively. Home range size varied little within each sex. Female bobcat home ranges tended to be relatively exclusive with respect to other females. The arrangement of male home ranges was less exclusive, and male and female home ranges overlapped extensively. Estimated minimum density of adult resident bobcats was one bobcat per 3.9 km2. Bobcats preferred riparian habitat. The bobcat (Lynx rufus baileyi) has been little studied in the southwest deserts of the United States. Jones and Smith (1979) studied the bobcat's diet in Arizona, but little information was gathered on home range or habitat preference. The majority of bobcat research has focused on diet and reproduction. With the development of radio-telemetry, more accurate data have been collected on bobcat home range and movements (Marshall and Jenkins, 1966; Bailey, 1972; Lembeck, 1978). The home range and habitat preference of bobcats have not previously been studied in a Sonoran desert environment. This study was conducted from July 1976 to January 1978 to ascertain: (1) home range size; (2) spatial distribution of home ranges; (3) population density; and (4) habitat preference, of a bobcat population in a Sonoran desert environment in central Arizona. STUDY AREA.-This study was conducted on the Three Bar Wildlife Area, in central Arizona in the Tonto National Forest, just west of Lake Roosevelt. Rainfall the past 20 years averaged 36.4 cm per year, and temperature extremes range from 43°C during the summer to -7°C in the winter. Steep slopes and rocky ravines are the main topographic characteristics of the Three Bar. This area has been ungrazed since 1947, and hunting and trapping of predators was banned in 1972 (Jones, 1977). The study area was on the northeast portion of the Three Bar. The elevation varies between 600 m and 1500 m. The study area supports four major habitats: Sonoran desert scrub, desert grassland, chaparral, and riparian (Dickerman, 1954). METHODS.-Using No. 2 steel leg-hold traps, five female and three male bobcats were captured. One male died from trap injuries. Trapping was done in a 6 km2 area in an attempt to capture all individuals. Trapped bobcats were immobilized with ketamine hydrochloride (16.5 mg/kg of body weight) and fitted with collar-mounted radio-transmitters (Telonics Inc., Mesa, Arizona). Instrumented bobcats were located primarily by triangulation from the ground, using a directional antenna. Whenever possible three or more azimuth readings were taken. An attempt was made to locate bobcats daily. The day was divided into 6 sampling periods which were cued to sunrise and sunset. Dawn was classified as beginning one hour before sunrise and ending one hour afterward. Dusk was, in like manner, a two hour time block set around sundown. The other 4 time blocks were classified as follows: 1) morning, between dawn and noon; 2) afternoon, between noon and dusk; 3) evening, between dusk and midnight; and 4) early morning, between This content downloaded from 207.46.13.112 on Mon, 03 Oct 2016 05:01:13 UTC All use subject to http://about.jstor.org/terms The Southwestern Naturalist BOBCAT 1 BOBCAT 3 ..... BOBCAT 4 ---BOBCAT 5 BOBCAT 6 BOBCAT 7