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Anthropogenic threat to the desert tortoise (Gopherus agassizii): Litter in the Mojave desert
... While litter was rare on our plot, we came upon approximately 7-10 mylar helium "party" balloons. Helium balloons can cause tortoise mortality by being ingested-becoming lodged in the gastrointestinal tract-or by entanglement (Burge 1989, Walde et al. 2007). Our study is not unique in finding that balloons make up the majority of trash on a tortoise plot (Walde et al. 2007), and this is not surprising considering the low amount of human traffic to YPG Dome Rock Mountains but the large distances-greater than 270 km-that a balloon can travel (Walde et al. 2007). ...
... Helium balloons can cause tortoise mortality by being ingested-becoming lodged in the gastrointestinal tract-or by entanglement (Burge 1989, Walde et al. 2007). Our study is not unique in finding that balloons make up the majority of trash on a tortoise plot (Walde et al. 2007), and this is not surprising considering the low amount of human traffic to YPG Dome Rock Mountains but the large distances-greater than 270 km-that a balloon can travel (Walde et al. 2007). ...
... Helium balloons can cause tortoise mortality by being ingested-becoming lodged in the gastrointestinal tract-or by entanglement (Burge 1989, Walde et al. 2007). Our study is not unique in finding that balloons make up the majority of trash on a tortoise plot (Walde et al. 2007), and this is not surprising considering the low amount of human traffic to YPG Dome Rock Mountains but the large distances-greater than 270 km-that a balloon can travel (Walde et al. 2007). ...
The Sonoran Desert Tortoise (Gopherus morafkai) faces several threats to its persistence, but military lands can provide conservation opportunities as large areas of military installations may be relatively undisturbed, have low levels of human traffic, and are mostly closed to the general public. Recent monitoring on the Yuma Proving Ground (YPG) indicates that tortoises have a patchy and low-density distribution there. It is imperative to have as much high-quality data as possible on the Sonoran Desert Tortoise in order to allow well-informed listing decisions. With this in mind, we have established the first of two Sonoran Desert Tortoise long-term monitoring plots on YPG, serving the dual purposes of providing YPG with information needed to best manage their tortoise population and adding to the range-wide population trend data. We established a new long-term monitoring plot in the Dome Rock Mountains, and in 2021 conducted four complete passes of exhaustive searches for Sonoran Desert Tortoises. A total of 13 individual tortoises (8 adults and 5 immature) were encountered 16 times during the surveys of the plot. A traditional Lincoln-Peterson population estimate from this mark-recapture data resulted in an estimated 19 +/- 4.9 tortoises on the plot, including immature tortoises. Other methods of estimating population size ranged from 10-16 adults and 21-30 total tortoises including immature individuals, depending on the assumptions of the model used. This study provides an important baseline upon which further studies can build and eventually lead to better-informed management for the Sonoran Desert Tortoise on YPG. Additionally, any data resulting from future monitoring efforts on this plot would provide valuable insights into conservation listing decisions.
... There are reported cases of accidental ingestion of plastic wastes by land mammals including elephants, hyenas, zebra, camels and cattle, resulting in death of these animals (Lai 2022). Ingestion of balloon by desert tortoise (Gopherus agassizii) and loss of limb as a result of balloon tangling has been reported (Walde et al 2007). Animals ingest plastics when they mistake it for food or prey due to its shape, colour or smell (Savoca et al 2016;Grant et al 2021) or by feeding on a prey that has ingested plastic (Hammer et al 2016). ...
Plastic pollution is ubiquitous throughout the world’s ecosystem. Increase in the world’s plastic production and use, inefficient recycling, indiscriminate disposal, synthetic nature and non-biodegradability of plastics have made it a considerable threat to biodiversity. The impact of plastic wastes on humans and the environment is becoming apparent. However, information on the impacts of plastic wastes on biodiversity is mostly directed towards marine environment with scarce information on land biodiversity although terrestrial environment is the major source of marine contamination. Terrestrial plastic waste contaminants are derived from long term used plastic containers and single-use plastic products, which are introduced by anthropological means, flood water, sewage and wind dispersal. Gradual breakdown of large plastic wastes give rise to microplastics, which increase its abundance in the environment. Plastics threaten wildlife in terms of entanglements, ingestion and chocking, which often results in loss of body parts or mortality. Plastics as vectors of invasive species in marine ecosystem have been widely established. Although not much is known on the importation of invasive species on terrestrial ecosystem by plastic wastes, there is possibility that plastic waste can be a potential vector of terrestrial alien species. Contamination of soil with microplastics alters soil habitats and disturbs the natural biophysical properties of the soil environment that leaves a negative impact on soil biota by reducing their activities and indirectly affecting food production. Accumulation of plastic wastes provides breeding ground for disease vectors, which has contributed to increased prevalence of emerging infectious diseases. This review examines the impact of plastic wastes on terrestrial biodiversity as it affects soil organisms, land animals and breeding of disease vectors.
... However, in the case of the Critically Endangered Bermuda rock skink Plestiodon longirostris, an endemic lizard of Bermuda, discarded containers are indeed one of the main threats (Davenport et al., 2001). It should be noted that containers such as bottles or cups are also a potential trap for reptiles (for details see Figure 4a in Kolenda et al., 2021), whereas other garbage poses other direct threats to reptiles, e.g. by ingestion or entanglement (Walde et al., 2007;Strine et al., 2014). Due to the relative rarity of the above-mentioned observations, the real impact of discarded containers on monitor populations remains poorly understood. ...
Zdunek, P. and Kolenda, K. 2022. The threat of discarded food and drinks containers to monitor lizards. Herpetological Bulletin 161: 28-30
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The aim of this note is to show that littering is a serious threat to monitor lizards. We present 30 cases where varanids got stuck inside discarded beverage or food containers. These include eight species of which Varanus acanthurus was the most common. The accidents took place in at least six countries. The most common traps were drink and food cans. In five containers lizards were found dead.
... Ongoing, low to moderate. Consumption of trash can lead to illness and death (Donoghue 2006, Walde et al. 2007). Balloons and other trash are common throughout the desert and most abundant near human habitations, along roads, and recreation use areas (Berry et al. , 2014a. ...
... Turtle ingestion of synthetic fishing line is also frequently reported [44][45][46] , but because this fishing line is likely ingested inadvertently when turtles take baited fish hooks or lures 47,48 , we consider this a very different form of plastic pollution and do not discuss these records further. Additionally, we identified eight non-marine turtle species that have been reported ingesting non-plastic litter 23,[41][42][43][49][50][51][52][53][54][55][56][57][58] . These eight include both aquatic and terrestrial species (Table S1). ...
Plastic pollution, and especially plastic ingestion by animals, is a serious global issue. This problem is well documented in marine systems, but it is relatively understudied in freshwater systems. For turtles, it is unknown how plastic ingestion compares between marine and non-marine species. We review the relevant turtle dietary literature, and find that plastic ingestion is reported for all 7 marine turtle species, but only 5 of 352 non-marine turtle species. In the last 10 years, despite marine turtles representing just 2% of all turtle species, almost 50% of relevant turtle dietary studies involved only marine turtles. These results suggest that the potential threat of plastic ingestion is poorly studied in non-marine turtles. We also examine plastic ingestion frequency in a freshwater turtle population, finding that 7.7% of 65 turtles had ingested plastic. However, plastic-resembling organic material would have inflated our frequency results up to 40% higher were it not for verification using Raman spectroscopy. Additionally, we showcase how non-native turtles can be used as a proxy for understanding the potential for plastic ingestion by co-occurring native turtles of conservation concern. We conclude with recommendations for how scientists studying non-marine turtles can improve the implementation, quality, and discoverability of plastic ingestion research.
... Trash was a potential contributor to poor health or death in all sizes of tortoises, with higher counts outside than inside the fence. Tortoises consume trash (this study, Donoghue 2006, Walde et al. 2007, which can lead to illness and death (Diaz-Figueroa and Mitchell 2006). ...
Feral Burros and Other Influences on Desert Tortoise Presence in the Western Sonoran Desert
KRISTIN H. BERRY1,4, JULIE L. YEE2, AND LISA M. LYREN3,5
1 U.S. Geological Survey, Western Ecological Research Center, 3621 Pinot Grigio Way, Reno, NV 89509, USA
2 U.S. Geological Survey, Western Ecological Research Center, 2885 Mission Street, Santa Cruz, CA 95060, USA
3 U.S. Geological Survey, Western Ecological Research Center, 2177 Salk Avenue, Suite 250, Carlsbad, CA 92008, USA
ABSTRACT: Across the globe, conflicting priorities exist in how land and resources are managed. In the American West, conflicts are common
on public lands with historical mandates for multiple uses. We explored the impacts of multiple uses of land in a case study of Agassiz’s Desert
Tortoises (Gopherus agassizii), a federally threatened species, in the western Sonoran Desert. The tortoise has declined for many reasons, most of
which relate to management of land and habitat. Frequently cited causes are livestock grazing, roads, vehicle-oriented recreation, predators, and
disease. In spring of 2009, we conducted a survey to evaluate relationships between desert tortoises, vegetation associations, topography,
predators, and anthropogenic uses. We sampled a 93-km2 area with 200 independent 1-ha plots. Density (6 SE) of adult tortoises was low, 2.0 6
1.0/km2, and the annualized death rate for adults during the 4 yr preceding the survey was high, 13.1%/yr. We observed tortoise sign, most of
which was recent, on 22% of the 200 plots, primarily in the southwestern part of the study area. More tortoise sign occurred on plots with
Brittlebush (Encelia spp.) vegetation at higher elevations. Most plots (91.0%) had �1 human-related impacts: feral burro scat (Equus asinus;
84.0%), recent vehicle tracks and trails (34.0%), trash (28.0%), burro trails and wallows (26.5%), and old vehicle tracks (24.0%). We used a
multimodel approach to model presence of tortoise sign on the basis of 12 predictor variables, and calculated model-averaged predictions for the
probability of tortoise presence. Importance values revealed two apparent top drivers: feral burros and vegetation association. This is the first
study to identify a negative association between presence of desert tortoises and feral burros.
Key words: Equus asinus; Gopherus agassizii; Trash; Vehicles; Vegetation association
... Trash was a potential contributor to poor health or death in all sizes of tortoises, with higher counts outside than inside the fence. Tortoises consume trash (this study, Donoghue 2006, Walde et al. 2007, which can lead to illness and death (Diaz-Figueroa and Mitchell 2006). ...
Agassiz’s desert tortoise (Gopherus agassizii), a threatened species of the southwestern United States, has severely declined to the point where 76% of populations in critical habitat (Tortoise Conservation Areas) are below viability. The potential for rapid recovery of wild populations is low because females require 12–20 years to reach reproductive maturity and produce few eggs annually. We report on a 34‐year mark‐recapture study of tortoises initiated in 1979 at the Desert Tortoise Research Natural Area in the western Mojave Desert, California, USA, and provide substantive data on challenges faced by the species. In 1980, the United States Congress designated the Research Natural Area and protected the land from recreational vehicles, livestock grazing, and mining with a wildlife‐permeable fence. The 7.77‐km2 study area, centered on interpretive facilities, included land both within the Natural Area and outside the fence. We expected greater benefits to accrue to the tortoises and habitat inside compared to outside. Our objectives were to conduct a demographic study, analyze and model changes in the tortoise population and habitat, and compare the effectiveness of fencing to protect populations and habitat inside the fence versus outside, where populations and habitat were unprotected. We conducted surveys in spring in each of 7 survey years from 1979, when the fence was under construction, through 2012. We compared populations inside to those outside the fence by survey year for changes in distribution, structure by size and relative age, sex ratios, death rates of adults, and causes of death for all sizes of tortoises. We used a Bayesian implementation of a Jolly Seber model for mark‐recapture data. We modeled detection, density, growth and transition of tortoises to larger size‐age classes, movements from inside the protective fence to outside and vice versa, and survival. After the second and subsequent survey years, we added surveys to monitor vegetation and habitat changes, conduct health assessments, and collect data on counts of predators and predator sign. At the beginning of the study, counts and densities for all sizes of tortoises were high, but densities were approximately 24% higher inside the fence than outside. By 2002, the low point in densities, densities had declined 90% inside the fence and 95% outside. Between 2002 and 2012, the population inside the fence showed signs of improving with a 54% increase in density. Outside the fence, densities remained low. At the end of the study, when we considered the initial differences in location, densities inside the fence were roughly 2.5 times higher than outside. The pattern of densities was similar for male and female adults. When evaluating survival by blocks of years, survivorship was higher in 1979–1989 than in 1989–2002 (the low point) and highest from 2002 to 2012. Recruitment and survival of adult females into the population was important for growing the population, but survival of all sizes, including juveniles, was also critical. Major events and activities driving the decline in populations both inside and outside the fence included illegal collecting, upper respiratory tract disease, and hyperpredation by the common raven (Corvus corax) on juvenile tortoises. Other sources of death were gunshots, vehicles, and predation by mammals. Outside the fence, fragmentation and deterioration of habitat was a critical driver. Between the first and last surveys, 2 different ecosystem processes were underway: recovery of vegetation and soils from grazing and vehicles inside the fence and continued deterioration outside the fence. Habitat outside the fence became increasingly denuded of shrubs and fragmented by roads and trails, and habitat fragments increased 50‐fold. Outside the fence, biomass of non‐native annual plants was higher and the cover of shrubs was lower, a reflection of ongoing deterioration. These changes and losses of habitat resulted in loss of shrub cover and sites for burrows, reduction in preferred food plants, and greater exposure to predators and extremes in temperature. Overall, the tortoise population and habitat inside the fence appeared to benefit from protection and showed signs of recovery at the end of the study. Fencing, control of vehicular access, and removal of livestock grazing were among several recommended management actions for critical habitat in the first recovery plan in 1994. At the end of the study, the Natural Area remained as 1 of 2 fenced, official protected areas for the species in the geographic range. We attribute fencing to continuing higher densities of adults inside the fence compared with outside the fence and promising signs of recovery. Densities of adults at the Natural Area also were 2.3 to 5.5 times higher than in 16 of the 17 Tortoise Conservation Areas (critical habitat units) within the geographic range. © 2020 The Authors. Wildlife Monographs published by Wiley Periodicals, LLC on behalf of The Wildlife Society. La tortue du désert ou gophère d’Agassiz (Gopherus agassizii), une espèce menacée du sud‐ouest des États‐Unis, a subi une forte régression, au point que 76% des populations dans l’habitat essentiel (zones de protection des tortues) sont en dessous du seuil de viabilité. Le potentiel de régénération rapide des populations sauvages est faible, car les femelles n’atteignent leur maturité reproductive qu’après 12 à 20 ans, et même alors, elles ne pondent que peu d’œufs chaque année. Nous présentons ici une étude par marquage‐recapture sur les tortues, entreprise en 1979 et conduite pendant 34 ans dans la zone naturelle de recherche sur les tortues du désert, dans l’ouest du désert de Mojave en Californie, et nous fournissons des données concrètes sur les difficultés rencontrées par cette espèce. En 1980, le Congrès américain a délimité la zone naturelle de recherche et installé une clôture perméable à la faune pour protéger le terrain des véhicules récréatifs, du pâturage de bétail et de l’exploitation minière. La zone étudiée de 7,77 km2, située autour des installations didactiques, comprenait des terres à l’intérieur et à l’extérieur de la zone naturelle clôturée. Nous nous attendions à ce que les tortues et leur habitat se trouvent davantage à l’intérieur qu’à l’extérieur de la zone. Nos objectifs étaient de mener une étude démographique, d’analyser et de modéliser les changements dans la population de tortues et leur habitat, et d’évaluer l’efficacité de la clôture sur la protection des populations et de l’habitat avec une comparaison entre l’intérieur et l’extérieur de la zone. Nous avons effectué des relevés au printemps de sept années entre 1979, lorsque la clôture était en construction, et 2012. Nous avons comparé les populations à l’intérieur et à l’extérieur de la clôture entre ces sept années: changements dans la distribution, structure selon la taille et l’âge relatif, proportion des sexes, taux de mortalité des adultes et causes de décès pour toutes les tailles de tortues. Nous avons utilisé une implémentation bayésienne d’un modèle Jolly‐Seber pour les données de marquage‐recapture. Nous avons modélisé la détection, la densité, la croissance et la transition des tortues vers les classes de taille‐âge supérieures, leurs mouvements de l’intérieur de la clôture de protection vers l’extérieur et vice versa, et leur survie. À partir de la deuxième année, nous avons ajouté des relevés pour surveiller les changements de la végétation et de l’habitat, évaluer la santé des tortues et recueillir des données sur le nombre de prédateurs et les signes de présence de prédateurs. Au début de l’étude, les dénombrements et la densité des populations de toutes les tailles de tortues étaient élevés, mais les densités étaient environ 24% plus élevées à l’intérieur de la clôture qu’à l’extérieur. En 2002, l’année où elles étaient les plus faibles, les densités avaient diminué de 90% à l’intérieur de la clôture et de 95% à l’extérieur. Entre 2002 et 2012, la population à l’intérieur de la clôture a montré des signes d’amélioration avec une augmentation de 54% de la densité. À l’extérieur de la clôture, les densités sont restées faibles. À la fin de l’étude, lorsque les différences initiales de localisation ont été prises en compte, les densités à l’intérieur de la clôture étaient environ 2,5 fois plus élevées qu’à l’extérieur. Les densités de population étaient similaires pour les adultes mâles et femelles. L’évaluation par périodes a montré que la survie était meilleure entre 1979 et 1989 qu’entre 1989 et 2002 (le niveau le plus bas), et encore meilleure entre 2002 et 2012. Le nombre et la survie des femelles adultes étaient des facteurs importants pour accroître la population, mais la survie de toutes les tailles de tortues, y compris des jeunes, était critique également. Les principaux événements et activités entraînant le déclin des populations à l’intérieur et à l’extérieur de la clôture étaient notamment le braconnage, les maladies des voies respiratoires supérieures et l’hyperprédation des jeunes tortues par le corbeau commun (Corvus corax). Les autres causes de mortalité étaient les tirs d’armes à feu, les véhicules et la prédation par des mammifères. À l’extérieur de la clôture, la fragmentation et la détérioration de l’habitat étaient un facteur critique. Entre le premier et le dernier relevé, deux processus écosystémiques différents étaient à l’œuvre: régénération de la végétation et des sols précédemment abîmés par les pâturages et les véhicules à l’intérieur de la clôture; poursuite de la détérioration à l’extérieur de la clôture. L’habitat à l’extérieur de la clôture était de plus en plus dépourvu de végétation et fragmenté par les routes et les sentiers, et les fragments d’habitat ont été multipliés par 50. À l’extérieur de la clôture, la biomasse de plantes annuelles non indigènes a augmenté et le couvert d’arbustes a été réduit, reflétant une détérioration continue. Ces changements et ces pertes d’habitat ont entraîné une réduction du couvert arbustif et des sites pouvant accueillir des terriers, une raréfaction des plantes dont se nourrissent les tortues et une plus grande exposition aux prédateurs et aux températures extrêmes. Dans l’ensemble, la population de tortues et l’habitat à l’intérieur de la clôture semblaient avoir bénéficié de la protection apportée et montraient des signes de régénération à la fin de l’étude. La clôture, le contrôle de l’accès des véhicules et la suppression des pâturages faisaient partie des mesures recommandées pour l’habitat essentiel dans le premier plan de régénération en 1994. À la fin de l’étude, la zone naturelle est demeurée l’une des deux zones officiellement protégées et clôturées pour l’espèce dans l’aire de répartition de l’espèce. Nous attribuons à la clôture la persistance de plus fortes densités d’adultes à l’intérieur par rapport à l’extérieur ainsi que les signes prometteurs de régénération. Les densités de population adulte dans la zone naturelle étaient également de 2,3 à 5,5 fois plus élevées que dans 16 des 17 zones de protection des tortues (unités d’habitat essentiel) de l’aire de répartition de l’espèce. We conducted a 34‐year demographic study of threatened Agassiz’s desert tortoises at the fenced Desert Tortoise Research Natural Area in the Mojave Desert, comparing a population inside the fence with one outside the fence. The fence successfully prevented habitat degradation but was insufficient in preventing a catastrophic decline caused by numerous anthropogenic activities, including an infectious disease and predation by common ravens. However, by 2012, the population inside the fence showed signs of increasing, whereas the population outside the fence was below viability.
... The relationships between Vehicles and Trash were positive, but between Trash and tortoise sign were negative. Tortoises are known to consume trash and balloons, which can lead to death (Donoghue 2006;Walde et al. 2007). ...
We evaluated the status of a population of Mojave Desert Tortoises (Gopherus agassizii), a threatened species, in the El Paso Mountains of the northwestern Mojave Desert in California, USA. The study area lies north of and adjacent to a designated critical habitat unit for the species, is adjacent to a state park, and is a short distance from the Desert Tortoise Research Natural Area. We randomly sampled 373 1-ha plots from a 239.1-km² area in the mountain range to determine demographic attributes of the population, vegetation associations, predator presence, and human uses. Live and dead G. agassizii and sign (burrows, scats, tracks) occurred on 35.7% of plots. Densities of adults were higher than in adjacent critical habitat, and threats (traumatic injuries, infectious and other diseases) were similar to those reported elsewhere in the geographic range. Signs of human use were evident on 98.4% of plots. We used a multimodel approach to determine distribution of G. agassizii in relation to vegetation, anthropogenic, and predator variables. Vegetation, predators, trash, mining activity, and vehicles were important factors affecting the distribution and intensity of tortoise sign. We concluded that this population is in a downward trend, like other populations in the western Mojave Desert. The high death rate of adults, low population density, high human visitor use, and ongoing decline in the adjacent critical habitat unit indicate that a viable population is unlikely to persist in the study area. The future for the population found in the El Paso Mountains might depend on survival in the adjacent roadless El Paso Mountains Wilderness Area.
In contrast to the abundance of research on marine debris, terrestrial anthropogenic litter and its impacts are largely lacking scientific attention. Therefore, the main objective of the present study is to find out whether ingested litter produces pathological consequences to the health of domestic ruminants, as it does in their relatives in the ocean, the cetaceans. For this purpose, five meadows (49°18'N, 10°24'E) with a total survey area of 139,050 m2 as well as the gastric content of 100 slaughtered cattle and 50 slaughtered sheep have been examined for persistent man-made debris in Northern Bavaria, Germany. All the five meadows contained garbage, and plastics were always part of it. Including glass and metal, 521 persistent anthropogenic objects were detected altogether, equalling a litter density of 3747 items per km2. Of the examined animals, 30.0% of the cattle and 6.0% of the sheep harboured anthropogenic foreign bodies in their gastric tract. As in the case of cetaceans, plastics were the most dominant litter material. Bezoars had formed around plastic fibres of agricultural origin in two young bulls, whereas pointed metal objects were associated in cattle with traumatic lesions in the reticulum and the tongue. Of all the ingested anthropogenic debris, 24 items (26.4%) had direct equivalents in the studied meadows. Comparing with marine litter, 28 items (30.8%) were also present in marine environments and 27 items (29.7%) were previously reported as foreign bodies in marine animals. At least in this study region, waste pollution affected terrestrial environments and domestic animals, with clear equivalents in the marine world. Ingested foreign bodies produced lesions that may have reduced the animals' welfare and, regarding commercial purposes, their productivity.
The Mojave Desert Tortoise, Gopherus agassizii (Family Testudinidae), is a large terrestrial species that can reach >370 mm in straight midline carapace length (CL) but most individuals are smaller. Both sexes reach adulthood at 12 to 21 years and ca. 180 mm CL. The species is sexually dimorphic, with males typically larger than females; sexual characteristics of males become more obvious with increasing size and age. Females lay from 1 to 10 eggs per clutch and from 0 to 3 clutches annually, with eggs hatching after 67 to 104 days. Populations of G. agassizii have declined rapidly over the last several decades. Habitat throughout the geographic range has experienced major losses, degradation, and fragmentation as a result of urban and agricultural development, livestock grazing, military activities, transportation and utility corridors, high levels of visitor use, vehicle-oriented recreation, and energy development. Disturbed habitats were vulnerable to invading non-native grasses and forbs, creating an unnatural and destructive grass-fire cycle. When consumed by tortoises as their only diet, non-native (and native) grasses are harmful because of limited nutrients. Additionally, subsidized predators (Common Ravens, Coyotes, and dogs), infectious diseases, drought, and vandalism, add to the catastrophic effects of habitat loss and degradation. Tortoise populations have declined rapidly in density, and most populations are below viability, with fewer than 3.9 adults/km2. These declines occurred despite protections afforded by federal and state laws and regulations, ca. 26,000 km2 of federally designated critical habitat units, two Recovery Plans, and efforts to reduce the negative impacts of human activities. As noted by Allison and McLuckie (2018), the negative population trends in most of the critical habitat units suggest that under current conditions G. agassizii is on the path to extinction.
Distribution. – USA. Distributed in parts of the southern Great Basin, Mojave, and western
Sonoran deserts in southeastern California, southern Nevada, northwestern Arizona, and southwestern Utah, north and west of the Grand Canyon/Colorado River complex, with the exception of a small population east of the Colorado River.
Synonymy. – Xerobates agassizii Cooper 1861, Testudo agassizii, Gopherus agassizii, Gopherus polyphemus agassizii, Scaptochelys agassizii, Xerobates lepidocephalus Ottley and Velázques Solis 1989.
Subspecies. – None currently recognized.
Status. – IUCN 2019 Red List: Vulnerable (VU A1acde+2cde; assessed 1996); TFTSG Provisional Red List: Critically Endangered (CR; assessed 2011, 2018); CITES: Appendix II (Testudinidae spp.); US ESA: Threatened.
Observations surrounding the use of erosion control mesh fabrics and the hazards presented to snakes.
