Los ecosistemas de secano están siendo cada vez más afectados por la extracción de combustibles fósiles, con pozos de petróleo y gas operativos típicamente durante dos a cuatro décadas. Los mandatos federales exigen que se tomen medidas para devolver las plataformas de pozos abandonados a “condiciones naturales”. Sin embargo, lograr este objetivo sigue siendo difícil de alcanzar por diversas razones. Este estudio investigó las cronosecuencias de plataformas de pozos abandonados en las comunidades de arbustos de Wyoming y de blackbrush en la Meseta de Colorado para cuantificar la perturbación del suelo y evaluar su posible correlación con el tiempo transcurrido desde el abandono, así como con el rendimiento fisiológico de los arbustos en las plataformas de pozos en comparación con la vegetación de referencia. Medimos la resistencia mecánica del suelo, la conductividad eléctrica del suelo, los potenciales hídricos del suelo y de las plantas, así como las tasas de intercambio de gases en las hojas a mediados del verano en plataformas de pozos abandonados y en la vegetación de referencia cercana, abarcando 18 sitios de arbustos de Wyoming y 9 de blackbrush. Los resultados indican una compactación significativa del suelo en las plataformas de pozos en ambas comunidades, así como niveles significativamente elevados de salinidad en las comunidades de arbustos de Wyoming, donde ni la compactación ni la salinidad se habían recuperado significativamente en un plazo de 50 años tras el abandono. Por el contrario, en las comunidades de blackbrush, las plataformas de pozos abandonados durante 40 a 50 años mostraron niveles de compactación similares a los de los sitios de referencia. La evaluación fisiológica reveló que, en ambas comunidades, los arbustos en las plataformas de pozos tenían potenciales hídricos significativamente menos negativos y tasas de intercambio de gases más altas que los arbustos en la vegetación de referencia, probablemente debido a la reducción de la cobertura de arbustos y la menor competencia por el agua del suelo. Si bien los potenciales hídricos de los arbustos en las plataformas de pozos en la comunidad de arbustos de Wyoming tendieron a igualarse con los de la vegetación de referencia con el tiempo, se observó la tendencia opuesta en las comunidades de blackbrush. Concluimos que las comunidades de blackbrush pueden tener un mayor potencial para la recuperación natural, aunque el proceso puede ser lento, mientras que la recuperación en las comunidades de arbustos de Wyoming podría estar indefinidamente estancada debido a las condiciones del suelo persistentemente deficientes, las cuales seguirían obstaculizando el establecimiento de plántulas de arbustos.

The Mojave desert tortoise Gopherus agassizii experienced population declines during recent decades, which have persisted despite its designation as a federally protected species. A small number of populations were monitored with mark-recapture methods starting in the 1970s, but inconsistent sampling resulted in challenges estimating the range of factors influencing survival. Large amounts of tortoise telemetry data were collected in recent decades, providing an alternative source for survival estimation. Here, we describe an integrated, spatially explicit, analysis that combined mark-recapture (3923 tortoises, 35 sites, 1977-2022) and telemetry (2858 tortoises, 22 sites, 1988-2022) datasets to estimate variation in survival across tortoise populations. We produced robust estimates of annual survival conditioned on climate-related covariates and compared results to non-integrated known-fate and mark-recapture models. Integration allowed for estimation of effects on survival not recovered by non-integrated models, including higher survival of males than females, lower survival of juveniles and subadults than adults, and a positive effect of total precipitation from 2 prior winters and active seasons. The integrated analysis estimated permanent emigration rate as the difference between both true survival (via telemetry data) and apparent survival (via capture-recapture data). Annual emigration probability was ~5% in 1 km2 plots and decreased with increasing plot size. Our results demonstrate the strength of leveraging multiple data sources in describing historical demographic rates and identifying relationships with covariates that have delayed effects on survival. Our modeling framework could be used to examine the effects of additional factors on tortoise survival and resulting population dynamics.

Obtaining reliable estimates of demographic parameters is critical to effective wildlife conservation and management. Densities of Mojave Desert Tortoises (Gopherus agassizii) were historically derived from capture-mark-recapture surveys on small, often strategically placed demography plots, or demographic study areas, that also provided information on demographic composition and vital rates. After protection was afforded to Desert Tortoises under the US Endangered Species Act in 1990, monitoring shifted mostly to line-distance sampling across broad areas for estimating densities of primarily adult tortoises to inform long-term population trends. However, that approach is incapable of providing data about other demographic characteristics important to population growth and viability. We surveyed a previously unsampled demography plot in the western Mojave Desert, California, USA, during 2022 and applied spatial capture-recapture (SCR) models to estimate spatially explicit Desert Tortoise density and sex-by-size class compositions. Directly accounting for spatiotemporally varying survey effort in SCR models via hazard-based adjustment reduced the estimated detection rate by 91% and increased the estimated density by 17%. Estimated spatial mean Desert Tortoise density across a 2.53-km(2) area was 18.53 tortoises/km(2) (95% confidence interval [CI] = 12.36-27.77). The SCR model-estimated size class ratio was skewed toward prereproductive tortoises (64% prereproductive; 36% adults), whereas the adult sex ratio was female biased (61% females; 39% males). Those ratios corresponded to densities of 11.86 prereproductive tortoises/km(2) (95% CI = 7.91-17.77), 4.08 adult female tortoises/km(2) (95% CI = 2.72-6.11), and 2.59 adult male tortoises/km(2) (95% CI = 1.73-3.89). Estimated tortoise density and demographic composition collectively support a high potential for population growth. Our study provides an illustrative example of using SCR models to directly estimate spatially explicit local Desert Tortoise densities and demographic composition that can be used for long-term monitoring and comparisons with other demography plots to inform conservation.

Joshua trees are long-lived perennial monocots native to the Mojave Desert in North America. Composed of two species, Yucca brevifolia and Y. jaegeriana (Asparagaceae), Joshua trees are imperiled by climate change, with decreases in suitable habitat predicted under future climate change scenarios. Relatively little is understood about the ecophysiology of Joshua trees across their range, including the extent to which populations are locally adapted or phenotypically plastic to environmental stress. Plants in our common gardens showed evidence of Crassulacean acid metabolism photosynthesis (CAM) in a pilot experiment, despite no prior report of this photosynthetic pathway in these species. We further studied the variation and strength of CAM within a single common garden, measuring seedlings representing populations across the range of the two species. A combination of physiology and transcriptomic data showed low levels of CAM that varied across populations but were unrelated to home environmental conditions. Gene expression confirmed CAM activity and further suggested differences in carbon and nitrogen metabolism between Y. brevifolia and Y. jaegeriana. Together the results suggest greater physiological diversity between these species than initially expected, particularly at the seedling stage, with implications for future survival of Joshua trees under a warming climate.

Texas Tortoises (Gopherus berlandieri) are understudied compared to federally protected congeners. Despite important early studies on the basic ecology of G. berlandieri, quantitative identification of habitat associations with specific environmental conditions has been limited. Gopherus berlandieri inhabits Tamaulipan thornscrub across its range, and coastal populations are historically associated with low-relief clay ridges with thick mesquital scrub surrounded by salt prairie grasslands. Our study examined tortoise home range size and association with canopy cover and potential ground moisture at a protected natural area in Cameron County, TX, USA. Twelve tortoises were outfitted with GPS loggers that recorded location once an hour from March 2020 to March 2022. To delineate home ranges, we estimated utilization distributions (UDs) for tortoises as autocorrelated kernel density estimates (AKDEs) at low-use (95%) and core-use (50%) levels for each tortoise. UDs were estimated for the entire study period and during seasons of sustained heat or cold to determine if tortoises used space differently across these seasons over the study period. Applying a use-availability study design, we compared canopy cover and potential mesic ground condition (i.e., precipitation flow accumulation) within each tortoise's UD ("use") to the area within 1 day's movement around the boundary of the UD ("available"). Tortoise UD sizes were significantly different across seasons for low-use (95%) but not for core-use (50%) AKDE levels. Tortoise UDs had greater canopy cover compared to available-but-unused areas at both AKDE levels. Potential mesic ground condition did not significantly differ between available and used areas. Our study revealed that tortoises vary the size of their home ranges throughout the year, whereas areas of intensive use or occupation tended to remain remarkably stable throughout the year. In seasons of extreme weather (hot or cold), tortoises seem to seek out areas of denser canopy cover that likely serve as thermal refugia. Based on our results, effective habitat identification may best be served by ensuring that canopy cover is at least equivalent to the values reported here to ensure sufficient refugia during extreme seasonal temperatures.

Joshua trees ( Yucca brevifolia and Yucca jaegeriana ) are iconic, foundational species of the Mojave and Sonoran Deserts in North America. Due to their ecosystem importance, long generation times, and low resilience to disturbance, these hybridizing sister species are increasingly the focus of conservation efforts. Predicting Joshua tree responses to impending climate variability, along with the extent of suitable future habitat and/or climate refugia, is critical to ongoing management planning. Previous modeling efforts have been hampered by incomplete distribution data and are now out‐of‐date with the most recent global climate projections. We used a high‐resolution, field‐validated distributional database of nearly complete presence and absence records, along with a simulation of dispersal, to project Joshua tree distributions into future time periods and Coupled Model Intercomparison Project phase 6 (CMIP6) emissions scenarios. Overall, our models predict widespread habitat loss with limited availability of newly suitable habitat. Under the highest emissions scenario (SSP5–8.5), we project that up to 80% of current habitat may become unsuitable by 2100. Even so, our models predict a larger area of potential refugia than some previous efforts, particularly in the southern parts of the range, where we project persistent refugia through 2100. We also found a non‐negligible influence of baseline climate period (the period used to represent “current” climate) on predicted future habitat probabilities. Simulations of dispersal based on the Joshua tree's limited capacity suggest that over 25% of suitable future habitat could be inaccessible, while much of the remaining future habitat area consists of refugia within the upper elevations of the species' current range. An increasing frequency of wildfire appears to be the greatest rangewide threat to future suitable habitat for Joshua trees, followed by renewable energy development. Over 80% of future suitable habitat occurs on federally managed lands, including up to 47% within Bureau of Land Management‐administered areas and 15% within National Park Service units.

Identifying population-level relationships between predators and their prey is often predicated on having reliable population estimates. Camera-trapping is effective for surveying terrestrial wildlife, but many species lack individually unique natural markings that are required for most abundance and density estimation methods. Analytical approaches have been developed for producing population estimates from camera-trap surveys of unmarked wildlife; however, most unmarked approaches have strict assumptions that can be cryptically violated by survey design characteristics, practitioner choice of input values, or species behavior and ecology. Using multi-year datasets from populations of an unmarked predator and its co-occurring unmarked prey, we evaluated the consequences of violating two requirements of the random encounter model (REM), one of the first developed unmarked methods. We also performed a systematic review of published REM studies, with an emphasis on predator–prey ecology studies. Empirical data analysis confirmed findings of recent research that using detections from non-randomly placed cameras (e.g., on trails) and/or borrowing movement velocity (day range) values caused volatility in density estimates. Notably, placing cameras strategically to detect the predator, as is often required to obtain sufficient sample sizes, resulted in substantial density estimate inflation for both the predator and prey species. Systematic review revealed that 91% of REM density estimates in published predator–prey ecology studies were obtained using camera-trap data or velocity values that did not meet REM requirements. We suggest considerable caution making conservation or management decisions using REM density estimates from predator–prey ecology studies.

Climate change coupled with large-scale surface disturbances necessitate active restoration strategies to promote resilient and genetically diverse native plant communities. However, scarcity of native plant materials hinders restoration efforts, leading practitioners to choose from potentially viable but nonlocal seed sources. Genome scans for genetic variation linked with selective environmental gradients have become a useful tool in such efforts, allowing rapid delineation of seed transfer zones along with predictions of genomic vulnerability to climate change. When properly applied, genome scans can reduce the risk of maladaptation due to mismatches between seed source and planting site. However, results are rarely replicated among complimentary data sources. Here, we compared RAD-seq datasets with 819 and 2699 SNPs (in 625 and 356 individuals, respectively) from the Mojave Desert winter annual Chylismia brevipes. Overall, we found that the datasets consistently characterized both neutral population structure and genetic-environmental associations. Ancestry analyses indicated consistent spatial genetic structuring into four regional populations. We also detected a marked signal of isolation by resistance (IBR), wherein spatial genetic structure was better explained by habitat resistance than by geographic distance. Potentially adaptive loci identified from genome scans were associated with the same environmental gradients-fall precipitation, winter minimum temperature, and precipitation timing-regardless of dataset. Paired with our finding that habitat resistance best explained genetic divergence, our results suggest that isolation of populations within environmentally similar habitats-and subsequent local adaption along gradients parallel to these habitats-drive genome-wide divergence in this species. Moreover, strong genetic associations with winter precipitation timing, along with forecasted shifts in precipitation regime due to midcentury climate change, could impact future population dynamics, habitat distribution, and genetic connectivity for C. brevipes populations within the Mojave Desert.

Soft ticks in the genus Ornithodoros occur throughout the Mojave Desert in southern Nevada, southeastern California, and parts of southwestern Utah and northwestern Arizona, USA, and are frequently observed parasitizing Mojave desert tortoises (Gopherus agassizii). However, limited research exists examining the relationship between ticks and desert tortoises. Mojave desert tortoises are listed as threatened by the US Fish and Wildlife Service, and as such, their populations are monitored and individual tortoise health is routinely assessed. These health assessments document the presence and abundance of ticks present on tortoises, but detailed examination of the relationship between ticks and tortoise health has been lacking. This study analyzed the relationship between tick presence and desert tortoise health assessments as a function of season, location, age (adult vs. juvenile), foraging behavior, evidence of clinical signs of disease, body condition score, and sex. Our results indicate that more ticks were found on tortoises in the summer than in any other season. Ticks were observed more frequently on captive tortoises versus wild tortoises, and more ticks were likely to be present on adult tortoises than on juveniles. Ticks were also more likely to be observed on tortoises that lacked evidence of foraging and on tortoises with observed clinical signs of disease. These findings provide valuable insights into the biology of ticks in relation to tortoises that may be useful for management of both captive and free-living threatened tortoise populations where ticks are detected. Our study also may improve understanding of potential tick-borne disease dynamics in the Mojave desert tortoise habitat, including Borrelia sp. carried by Ornithodoros ticks, which cause tick-borne relapsing fever in people.

Quantifying how global change impacts wild populations remains challenging, especially for species poorly represented by systematic datasets. Here, we infer climate change effects on masting by Joshua trees (Yucca brevifolia and Y. jaegeriana), keystone perennials of the Mojave Desert, from 15 years of crowdsourced observations. We annotated phenophase in 10,212 geo-referenced images of Joshua trees on the iNaturalist crowdsourcing platform, and used them to train machine learning models predicting flowering from annual weather records. Hindcasting to 1900 with a trained model successfully recovers flowering events in independent historical records and reveals a slightly rising frequency of conditions supporting flowering since the early 20th Century. This reflects increased variation in annual precipitation, which drives masting events in wet years-but also increasing temperatures and drought stress, which may have net negative impacts on recruitment. Our findings reaffirm the value of crowdsourcing for understanding climate change impacts on biodiversity.

The threatened Mojave desert tortoise ( Gopherus agassizii ) exhibits temperature-dependent sex determination, and individuals appear externally sexually monomorphic until sexual maturity. A non-surgical sex identification method that is suitable for a single in situ encounter with hatchlings is essential for minimizing handling of wild animals. We tested (1) whether plasma testosterone quantified by enzyme-linked immunosorbent assay differentiated males from females in 0–3 month old captive hatchlings, and (2) whether an injection of follicle-stimulating hormone (FSH) differentially elevates testosterone in male hatchlings to aid in identifying sex. We validated sex by ceolioscopic (laparoscopic) surgery. We then fit the testosterone concentrations to lognormal distributions and identified the concentration below which individuals are more likely female, and above which individuals are more likely male. Using a parametric bootstrapping procedure, we estimated a 0.01–0.04% misidentification rate for naïve testosterone samples, and a 1.26–1.39% misidentification rate for challenged (post-FSH injection) testosterone samples. Quantification of plasma testosterone concentration from small volume (0.1 mL) blood samples appears to be a viable, highly accurate method to identify sex of 0–3 month old hatchlings and could be a valuable tool for conservation measures and investigation of trends and variation in sex ratios for in situ wild nests.

IntroductionForecasting range shifts in response to climate change requires accurate species distribution models (SDMs), particularly at the margins of species' ranges. However, most studies producing SDMs rely on sparse species occurrence datasets from herbarium records and public databases, along with random pseudoabsences. While environmental covariates used to fit SDMS are increasingly precise due to satellite data, the availability of species occurrence records is still a large source of bias in model predictions. We developed distribution models for hybridizing sister species of western and eastern Joshua trees (Yucca brevifolia and Y. jaegeriana, respectively), iconic Mojave Desert species that are threatened by climate change and habitat loss.MethodsWe conducted an intensive visual grid search of online satellite imagery for 672,043 0.25 km2 grid cells to identify the two species' presences and absences on the landscape with exceptional resolution, and field validated 29,050 cells in 15,001 km of driving. We used the resulting presence/absence data to train SDMs for each Joshua tree species, revealing the contemporary environmental gradients (during the past 40 years) with greatest influence on the current distribution of adult trees.ResultsWhile the environments occupied by Y. brevifolia and Y. jaegeriana were similar in total aridity, they differed with respect to seasonal precipitation and temperature ranges, suggesting the two species may have differing responses to climate change. Moreover, the species showed differing potential to occupy each other's geographic ranges: modeled potential habitat for Y. jaegeriana extends throughout the range of Y. brevifolia, while potential habitat for Y. brevifolia is not well represented within the range of Y. jaegeriana.DiscussionBy reproducing the current range of the Joshua trees with high fidelity, our dataset can serve as a baseline for future research, monitoring, and management of this species, including an increased understanding of dynamics at the trailing and leading margins of the species' ranges and potential for climate refugia.

Roadways and railways can reduce wildlife movements across landscapes, negatively impacting population connectivity. Connectivity may be improved by structures that allow safe passage across linear barriers, but connectivity could be adversely influenced by low population densities. The Mojave desert tortoise is threatened by habitat loss, fragmentation, and population declines. The tortoise continues to decline as disturbance increases across the Mojave Desert in the southwestern United States. While underground crossing structures, like hydrological culverts, have begun receiving attention, population density has not been considered in tortoise connectivity. Our work asks a novel question: How do culverts and population density affect connectivity and potentially drive genetic and demographic patterns? To explore the role of culverts and population density, we used agent-based spatially explicit forward-in-time simulations of gene flow. We constructed resistance surfaces with a range of barriers to movement and representative of tortoise habitat with anthropogenic disturbance. We predicted connectivity under variable population densities. Simulations were run for 200 non-overlapping generations (3400 years) with 30 replicates using 20 microsatellite loci. We evaluated population genetic structure and diversity and found that culverts would not entirely negate the effects of linear barriers, but gene flow improved. Our results also indicated that density is important for connectivity. Low densities resulted in declines regardless of the landscape barrier scenario (> 75% population census size, > 97% effective population size). Results from our simulation using current anthropogenic disturbance predicted decreased population connectivity over time. Genetic and demographic effects were detectable within five generations (85 years) following disturbance with estimated losses in effective population size of 69%. The pronounced declines in effective population size indicate this could be a useful monitoring metric. We suggest management strategies that improve connectivity, such as roadside fencing tied to culverts, conservation areas in a connected network, and development restricted to disturbed areas.

Species conservation plans frequently rely on information that spans political and administrative boundaries, especially when predictions are needed of future habitat under climate change; however, most species conservation plans and their requisite predictions of future habitat are often limited in geographical scope. Moreover, dispersal constraints for species of concern are not often incorporated into distribution models, which can result in overly optimistic predictions of future habitat. We used a standard modeling approach across a suite of 23 taxa of amphibians and reptiles in the North American deserts (560,024 km(2) across 13 ecoregions) to assess impacts of climate change on habitat and combined landscape population dispersal simulations with species distribution modeling to reduce the risk of predicting future habitat in areas that are not available to species given their dispersal abilities. We used 3 general circulation models and 2 representative concentration pathways (RCPs) to represent multiple scenarios of future habitat potential and assess which study species may be most vulnerable to changes forecasted under each climate scenario. Amphibians were the most vulnerable taxa, but the most vulnerable species tended to be those with the lowest dispersal ability rather than those with the most specialized niches. Under the most optimistic climate scenario considered (RCP 2.6; a stringent scenario requiring declining emissions from 2020 to near zero emissions by 2100), 76% of the study area may experience a loss of >20% of the species examined, while up to 87% of the species currently present may be lost in some areas under the most pessimistic climate scenario (RCP 8.5; a scenario wherein greenhouse gases continue to increase through 2100 based on trajectories from the mid-century). Most areas with high losses were concentrated in the Arizona and New Mexico Plateau ecoregion, the Edwards Plateau in Texas, and the Southwestern Tablelands in New Mexico and Texas, USA. Under the most pessimistic climate scenario, all species are predicted to lose some existing habitat, with an average of 34% loss of extant habitat across all species. Even under the most optimistic scenario, we detected an average loss of 24% of extant habitat across all species, suggesting that changing climates may influence the ranges of reptiles and amphibians in the Southwest.

Space use by mammals can differ among age-classes, sexes, or seasons, and these processes are recognized as adaptive behavioral strategies. Semi-fossorial ground squirrels, in particular, have shown age- and sex-specific patterns in their aboveground movement behaviors. We studied space use of Mohave ground squirrels (Xerospermophilus mohavensis) at the Freeman Gulch study site in the central region of their range in the Mojave Desert, California. We documented the timing of their full annual cycle, investigated correlates of size of home ranges of adults and distance of long-distance movements by juveniles, and evaluated whether juvenile body masses and movements were related to interannual climatic variation. Adult males emerged from burrows and entered hibernation sooner than did adult females. Home ranges were larger for males ((x) over bar over bar +/- SD = 0.50 +/- 0.40 km(2)) than females (0.05 +/- 0.03 km(2)), especially during the mating season. Maximum distances moved by juveniles did not differ significantly between males (1.6 +/- 2.3 km) and females (1.0 +/- 1.8 km), and both sexes were equally likely to travel long distances from natal sites. The longest-distance movement we documented was 7.7 km by a juvenile male. Juveniles born in a year of low vegetation productivity gained significantly less mass (97 +/- 7 g) and traveled shorter distances than those born in a year of higher vegetation productivity (177 +/- 20 g). Our findings were similar to those documented in the Coso Range study site in the northern region of the geographic range of the species, indicating that movement patterns are similar range-wide. Mohave ground squirrels responded strongly to climate variation, and global climate change will likely result in a northward shift in suitable habitats. Informed conservation planning, therefore, will be essential for this rare, declining species.

AbstractAmphibians and reptiles are a diverse group of ectothermic vertebrates that occupy a variety of habitats in rangelands of North America, from wetlands to the driest deserts. These two classes of vertebrates are often referred to as herpetofauna and are studied under the field of herpetology. In U.S. rangelands, there are approximately 66 species of frogs and toads, 58 salamanders, 98 lizards, 111 snakes, and 27 turtles and tortoises. Herpetofauna tend to be poorly studied compared with other vertebrates, which creates a challenge for biologists and landowners who are trying to manage rangeland activities for this diverse group of animals and their habitats. Degradation of habitats from human land use and alteration of natural processes, like wildfire, are primary threats to herpetofauna populations. Disease, non-native predators, collection for the pet trade, and persecution are also conservation concerns for some species. Properly managed livestock grazing is generally compatible with herpetofauna conservation, and private and public rangelands provide crucial habitat for many species. Climate change also poses a threat to herpetofauna, but we have an incomplete understanding of the potential effects on species. Dispersal and adaptation could provide some capacity for species to persist on rangelands as climates, disturbance regimes, and habitats change. However, inadequate information and considerable uncertainty will make climate mitigation planning difficult for the foreseeable future. Planning for and mitigating effects of climate change, and interactions with other stressors, is an urgent area for research. Maintaining large, heterogeneous land areas as rangelands will certainly be an important part of the conservation strategy for herpetofauna in North America.

IntroductionAnimal movements are influenced by landscape features; disturbances to the landscape can alter movements, dispersal, and ultimately connectivity among populations. Faster or longer movements adjacent to a localized disturbance or within disturbed areas could indicate reduced habitat quality whereas slower or shorter movements and reduced movements may indicate greater availability of resources. The Mojave desert tortoise (Gopherus agassizii) is a threatened species that is challenged by anthropogenic disturbances. MethodsWe studied tortoise movements using Global Positioning System (GPS) loggers at multiple sites in the Mojave Desert of Nevada and California. Tortoises at our sites encountered localized, linear human infrastructure, including paved roads, dirt roads, and fences, as well as landscape-scale disturbances [wildfire, off highway vehicle use (OHV), livestock grazing area]. We fit two-state (moving and encamped) Hidden Markov models to GPS logger data to infer how tortoise movement behavior relates to anthropogenic and natural features. ResultsWe found that temporal covariates, individual-level random effects (intercepts), and sex best explained state transition probability in all sites. We compared relationships between tortoise movement and linear disturbances, which varied depending on site and context. Tortoises made longer movements within the OHV recreation area, near most dirt roads, and near a low-traffic paved road, indicating that tortoises avoid these habitat disturbances. Conversely, tortoises made shorter movements in areas of higher slope and near highways, suggesting that these features may restrict movement or provide resources that result in prolonged use (e.g., forage or drinking locations). Tortoises that encountered fences around utility-scale solar installations were more active and made longer movements near fences, indicative of pacing behavior. DiscussionThese results provide insight into how different disturbances alter tortoise movement behavior and modify tortoise habitat use, providing information that can be used to manage tortoise habitat.