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This dataset provides spatial predictions of habitat suitability for Gopherus agassizii (Agassiz’s desert tortoise), Gopherus morafkai (Morafka’s desert tortoise) and a pooled-species model under current conditions (1950 – 2000 yr). The raster layers contained here accompany the manuscript Inman et al. 2019 and were used to evaluate subtle ecological niche differences between G. agassizii and G. morafkai, and identify local species-environment relationships. Spatial predictions of habitat suitability were created using MaxEnt version 3.4.0 (Phillips et al., 2006), a widely-used software for SDM in presence-background frameworks. Detailed methods are provided in Inman et al. 2019. Inman et al. 2019. Local niche...
The relationships between Mycoplasma agassizii, a causative agent of upper respiratory disease (URTD), and desert tortoise (Gopherus agassizii), generally illustrate the complexities of disease dynamics in wild vertebrate populations. In this review, we summarize current understanding of URTD in Mojave desert tortoise populations, we illustrate how inadequate knowledge of tortoise immune systems may obfuscate assessment of disease, and we suggest approaches to future management of URTD in desert tortoise populations. We challenge the view that M. agassizii causes consistent levels of morbidity and/or mortality across the Mojave desert. Instead, URTD may be described more accurately as a context-dependent disease....
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This dataset provides spatial predictions of clustering and the genotype association index for the Mojave genotype in local species-environment relationships of Desert Tortoises (Gopherus agassizi and Gopherus morafkaii) for individuals in the subregion encompassing the genetic sampling locations used by Edwards et al. (2015). This region offered an opportunity to explore habitat selection across the ecotone between the Mojave and Sonoran deserts and the secondary contact zone between G. agassizii and G. morafkai, and is referred to as the focal study area. The raster layers contained here accompany the manuscript Inman et al. 2019 and were used to identify multivariate clusters and map them back to geographic space....
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This dataset provides spatial predictions of the pooled-SDM residuals from a multiscale geographically weighted regression model (MGWR) and the resulting local R2 values for individuals in the subregion encompassing the genetic sampling locations used by Edwards et al. (2015). This region offered an opportunity to explore habitat selection across the ecotone between the Mojave and Sonoran deserts and the secondary contact zone between G. agassizii and G. morafkai, and is referred to as the focal study area. The raster layers contained here accompany the manuscript Inman et al. 2019 and were used to identify multivariate clusters and map them back to geographic space. Inman et al. 2019. Local niche differences predict...
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This dataset depicts the distribution of Desert Tortoise habitat in Arizona. This dataset was obtained from Arizona GAP with no metadata.
In the Sonoran Desert of North America, populations of the desert tortoise (Gopherus agassizii) occur in rocky foothills throughout southwestern Arizona and northwestern Mexico. Although tortoise populations appear to be isolated from each other by low desert valleys, individuals occasionally move long distances between populations. Increasingly, these movements are hindered by habitat fragmentation due to anthropogenic landscape changes. We used molecular techniques and radiotelemetry to examine movement patterns of desert tortoises in southern Arizona. We collected blood samples from 170 individuals in nine mountain ranges and analyzed variability in seven microsatellite loci to determine genetic differentiation...
1. 1. Deep body and shell surface temperatures were monitored via radio-telemetry from unrestrained desert tortoises in their natural habitat. 2. 2. The surface of the carapace acts as a buffer against solar radiation, resulting in deep body temperatures up to 10�C below shell surface at the time of the midday retreat to burrows. 3. 3. The burrow of the desert tortoise provides the only ambient temperatures at ground level which are below the lethal range for this species during midday hours. 4. 4. Evening retreat to burrows permits an extension of higher body temperatures into the mid-evening hours. 5. 5. The use of evening burrow retreats lessens in mid-summer. This behavioral change results in lower body temperatures...
Egg production by desert tortoises was estimated at two sites in San Bernardino, California: Ivanpah Valley in 1980 and 1981 and Goffs in 1983, 1984 and 1985. Mean clutch frequencies were estimated for 1980 (1.60) and 1981 (1.10) from mass changes observed among sexually mature females weighed every 1-2 wk. Mean clutch frequencies in 1983 (1.89), 1984 (1.57) and 1985 (1.75) were estimated from periodic X-rays of females. Clutch sizes were also determined from radiographs. Tortoises at Goffs typically laid 1-2 clutches during May and June, but one female failed to lay eggs in 1984 and single tortoises laid three clutches in 1983 and 1985. If tortoises laid two clutches, the second was faintly visible in X-rays within...
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This USFWS data set has been modified by NatureServe to include critical habitat only within the Central Basin and Range, and Mojave Basin and Range ecoregions, and further modified to include only the desert tortoise (Gopherus agassizii). These data identify, in general, the areas where final critical habitat exist for species listed as endangered or threatened.
The USGS GAP Analysis Program has developed range maps and distribution models for 1401 species, 604 of which are found within the SRLCC. This record's parent folder contains several examples of GAP species web services. The GAP website has a complete list of available web services for species as well as a map viewer for species data. Species: Desert Tortoise (Gopherus agassizii) There are two web services for this species: the range map, showing the geographic limits within which the species can be found, and a distribution model, which predicts the environment within the range that is suitable for occupation by the species. Link to metadata for GAP range maps and distribution models. To access services, select...
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This dataset provides the environmental explanatory variables used to explore spatial patterns in species-environment relationships in Gopherus agassizii and Gopherus morafkai across the subregion encompassing the genetic sampling locations used by Edwards et al. (2015). This region offered an opportunity to explore habitat selection across the ecotone between the Mojave and Sonoran deserts and the secondary contact zone between G. agassizii and G. morafkai, and is referred to as the focal study area. The raster layers contained here accompany the manuscript Inman et al. 2019 and were used to identify multivariate clusters and map them back to geographic space. Inman et al. 2019. Local niche differences predict...
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The Moj_ConservationAreas layer is a mosaic of data including the Arizona, California, Nevada, and Utah Areas of Critical Environmental Concern (ACEC), Critical Habitat Unit (CHU), the Red Cliffs Desert Reserve (RCDR), the Desert Tortoise Conservation Center (DTCC), the Desert National Wildlife Refuge, State and National Parks, National Monuments, National Conservation Areas, Beaver Dam Wash National Conservation Area, and the Boulder City Conservation Easement (BCCE). Landownership classification for Wilderness Areas and Wilderness Study Areas, Department of Defense and Department of Energy were also included.
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This USFWS data set has been clipped by NatureServe to include critical habitat only within the Central Basin and Range, and Mojave Basin and Range ecoregions, and extracted to include only the desert tortoise (Gopherus agassizii) critical habitat areas. These data identify, in general, the areas where final critical habitat exist for species listed as endangered or threatened.
We constructed minimum convex polygon (MCP) home ranges for free-ranging desert tortoises from a natural population adjacent to the Desert Tortoise Conservation Center, near Las Vegas, NV. Home range area estimates were not significantly different from those estimated for other desert tortoises in the Mojave and Sonoran deserts. Male tortoises had significantly larger and more variable home ranges in a combined statistical analysis of this study with those of Burge (1977) and Barrett (1990). Bootstrap analysis of the MCP polygon areas suggested substantial autocorrelation of the tortoise sightings despite a mean interval between recaptures of 3.2 days, violating an assumption of nearly all home range estimation...
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These data include environmental covariates used to develop species distribution models for Gopherus agassizii and Gopherus morafkai, along with PCA-reduced environmental covariates used to explore local species-environment relationships within a subregion of the ectone between the two species. We also provide the genotype association used to test the mapped clusters of multiscale geographically weighted regression coefficients against models of (i) a geographically-based taxonomic designation these two sister species, and (ii) an environmental ecoregion designation. These data support the following publication: Inman et al. 2019. Local niche differences predict genotype associations in sister taxa of desert tortoise....
The desert tortoise Gopherus agassizii is federally listed as Threatened because of documented declines in some populations, yet the proximate causes of these declines are not well understood. With use of radiotelemetry, I monitored a total of 55 individual tortoises at two Mojave Desert sites over three years. Both populations suffered high adult mortality during an extreme drought period, but the temporal pattern and inferred proximate causes of mortality differed between sites. At the eastern Mojave site, no telemetered tortoises died in 1988 or 1989, but 41% died in 1990. All nine carcasses were found and only one showed any evidence of predation or scavenging. Tortoises that died had symptoms of dehydration...
Habitat modeling offers an approach to understanding some management problems of desert tortoises (Gopherus agassizii) and to focusing new research efforts. Modeling can provide (1) a method to organize existing information, (2) a means to identify whether physical habitat or some factor outside the scope of the habitat model is limiting populations, (3) a method to integrate habitat into resource development planning, and (4) a mechanism for focusing research on missing species-habitat information. Published in Herpetologica, volume 42, issue 1, on pages 134 - 138, in 1986.
    map background search result map search result map GAP Web Service: Desert Tortoise Local ecological niche models, genotype associations and environmental data for desert tortoises. Environmental Explanatory Variables Habitat Genotype Association Local Niche Model Spatial Predictions of Mojave Desert Tortoise, Sonoran Desert Tortoise and Pooled Species Habitat Suitability for present-day (1950 – 2000 yr) BLM REA SOD 2010 Distribution of the Desert Tortoise in California and Arizona BLM REA SOD 2010 Desert Tortoise Distribution in Arizona (GAP) BLM REA MBR 2010 Final Critical Habitat (Polygonal Features) BLM REA MBR 2010 Conservation Areas in the Mojave Desert BLM REA CBR 2010 PLII CBR crithab poly tortoise BLM REA MBR 2010 Final Critical Habitat (Polygonal Features) BLM REA CBR 2010 PLII CBR crithab poly tortoise BLM REA SOD 2010 Desert Tortoise Distribution in Arizona (GAP) BLM REA SOD 2010 Distribution of the Desert Tortoise in California and Arizona BLM REA MBR 2010 Conservation Areas in the Mojave Desert Local ecological niche models, genotype associations and environmental data for desert tortoises. Environmental Explanatory Variables Habitat Genotype Association Local Niche Model Spatial Predictions of Mojave Desert Tortoise, Sonoran Desert Tortoise and Pooled Species Habitat Suitability for present-day (1950 – 2000 yr) GAP Web Service: Desert Tortoise