Desert Tortoise Research Articles

Characterizing range-wide impacts of anthropogenic barriers on structural landscape connectivity for the Sonoran desert tortoise (Gopherus morafkai)

Characterizing range-wide impacts of anthropogenic barriers on structural landscape connectivity for the Sonoran desert tortoise (Gopherus morafkai)

Designing a Long-term Occupancy Monitoring Plan for a Cryptic Reptile

Monitoring populations of cryptic reptiles is challenging because of their crypticity. Occupancy monitoring is a useful technique for local populations, but seasonal unavailability for detection can result in large swings in apparent annual occupancy. We used data from 5 yr of occupancy surveys, and the observed sampling and process error, to evaluate the power to detect true change in occupancy under a range of sampling scenarios and occupancy trends for a cryptic reptile, Mojave Desert Tortoise (Gopherus agassizii) None of the sampling strategies that we tested had the power to detect a 1% per annum increase in true occupancy over a 10-yr period and required ≥70 sites to detect a 1% decline in occupancy. For a 2% per annum change in true occupancy, 50 sites were needed and for a 3–4% per annum change 20–30 sites were needed. Power to detect a 4% per annum decline in occupancy was >80% for all number of secondary visits and number of sites if the number of sites was ≥50, but required seven visits to ≥60 sites to detect a 4% increase in occupancy Multiple sampling designs provided equivalent power. For example, both designs of 80 sites with three secondary visits and 50 sites with seven secondary visits yielded >50% power on average to detect 1–4% per annum changes in true occupancy. These results can help local managers of Mojave Desert Tortoises and other cryptic reptiles to design optimally efficient occupancy monitoring strategies.

Range‐wide occupancy trends for the Mojave desert tortoise (Gopherus agassizii)

AbstractData from long‐term monitoring programs, such as the US Fish and Wildlife Service (USFWS) line distance sampling (LDS) program for Mojave desert tortoises (Gopherus agassizii), are increasingly being used in new ways to elucidate trends in population dynamics. We used the USFWS LDS data in a novel way to generate range‐wide predictions of occupancy, colonization, and local extinction rates from 2001 to 2018. We developed a dynamic occupancy model to answer fundamental questions posed by Bureau of Land Management personnel regarding how G. agassizii are distributed across the landscape over space and time. We transformed the LDS data into detection/nondetection data and constructed a Bayesian dynamic occupancy model using several time‐varying (e.g., temperature, precipitation, normalized difference vegetation index, fire, and a proxy for invasive grasses) and static covariates (e.g., soil properties, topography, distance to roads, distance to urban areas) hypothesized to influence G. agassizii occupancy dynamics. We estimated that over the entire time series (2001–2018) the probability of G. agassizii occupancy is declining in over one quarter (26%) of the range, largely in the northeastern part of the range, but that from 2011 to 2018, 77% of the range has a declining trend. Drawing on these model outputs, we developed an interactive, web‐based tool for exploring trends in dynamic occupancy across the species range, allowing users to focus on areas of management interest or concern.

A spatially explicit model for density that accounts for availability: a case study withMojavedesert tortoises

AbstractEstimating population density and identifying those areas where density is changing through time are central to prioritizing conservation and management strategies. Obtaining reliable estimates of density and trends can be challenging, however, especially for long‐lived species that are rare, have broad geographic distributions, and are difficult to detect reliably during field surveys. We developed a hierarchical model for distance‐sampling data that characterizes spatial variation in density at two scales and simultaneously estimates regional trends while accounting for variation in detection probability and availability across surveys. We applied the model to data collected over a 20‐year period (2001–2020) in an area that encompassed most of the geographic range of the Mojave desert tortoise (Gopherus agassizii). Density of adult tortoises varied with multiple biotic and abiotic features, including topography, aspect, geology, and seasonal precipitation and temperature regimes. Across the entire period and study area, the density of adult tortoises decreased by an average of 1.8% per year (95% CI = −3.5% to −0.2%). Trends varied geographically, however, with the steepest declines in the western part of the range (−4.1%, −6.9% to −1.3%). Accounting for habitat loss across our study area, the abundance of this threatened species declined by an estimated 129,000 adults (36%) between 2001 and 2020. Our modeling approach extends traditional distance‐sampling frameworks by accounting for ecological and observational processes that could mask spatiotemporal variation in density and, at the same time, provides spatially explicit estimates to guide conservation and management strategies for tortoises and other rare species.

Drivers of survival of translocated tortoises

AbstractTranslocation of animals, especially for threatened and endangered species, is a currently popular but very challenging activity. We translocated 158 adult Agassiz's desert tortoises (Gopherus agassizii), a threatened species, from the National Training Center, Fort Irwin, in the central Mojave Desert in California, USA, to 4 plots as part of a long‐distance, hard‐release, mitigation‐driven translocation to prevent deaths from planned military maneuvers. We monitored demographic and behavioral variables of tortoises fitted with radio‐transmitters from 2008 to 2018. By the end of the project, 17.72% of tortoises were alive, 65.82% were dead, 15.19% were missing, and 1.27% were removed from the study because they returned to Fort Irwin. Mortality was high during the first 3 years: >50% of the released animals died, primarily from predation. Thereafter, mortality declined but remained high. After 10.5 years, survival was highest, 37.50% (15/40), on the plot closest to original home sites, whereas from 2.56% to 23.68% remained alive on the other 3 release plots. Surviving tortoises settled early, repeatedly using locations where they constructed burrows, compared with tortoises that died or disappeared. Models of behavioral and other variables indicated that numbers of repeatedly used locations (burrows) were a driver of survival throughout the study, although plot location, size and sex of tortoises, and distance traveled were contributors, especially during early years. Because >50% mortality occurred, we considered this translocation unsuccessful. The study area appeared to be an ecological sink with historical and current anthropogenic uses contributing to habitat degradation and a decline in both the resident and released tortoises. Our findings will benefit design and selection of future translocation areas.

Tropical Climates May Be Suitable for Endangered Desert Tortoise Exhibits, Rescues, Adoptions

Tropical Climates May Be Suitable for Endangered Desert Tortoise Exhibits, Rescues, Adoptions

Travel Management Planning for Wildlife with a Case Study on the Mojave Desert Tortoise

Abstract Roads are important drivers of habitat loss, degradation, and fragmentation that affect global biodiversity. Detrimental effects of roads include direct mortality of individual animals, spread of habitat-altering invasive plants, and loss of demographic and genetic connectivity of wildlife populations. Various measures address the negative effects of roads on wildlife. However, most strategies for minimizing or mitigating the effects of roads are focused on the actual roads themselves rather than on the collective travel network across landscapes. We summarized a growing body of literature that has documented the effects of road density on wildlife populations and the benefits associated with lower densities. This literature supports the application of limits on road density as a viable tool for managing cumulative effects. Based on these examples, we recommend road densities, including all linear features used for travel, of less than 0.6 km/km2 as a general target for travel management in areas where wildlife conservation is a priority. Lower densities may be necessary in particularly sensitive areas, whereas higher densities may be appropriate in areas less important to landscape-level conservation and wildlife connectivity. Public policy and funding also are needed to address challenges of enforcing off-highway vehicle regulations. In applying this general overview to a case study of the Mojave desert tortoise Gopherus agassizii, we found that all management plans across the species' range lack considerations of road density and that tortoise populations declined within all conservation areas with road densities of more than 0.75 km/km2. From this, we provide several travel management recommendations specific to Mojave desert tortoise conservation beginning with identifying the entire travel network within management areas. Specific actions for managing or setting limits for road density depend on the site-specific biological or management context, for instance relative to habitat quality or proximity to designated tortoise conservation areas. In addition, increasing law enforcement and public outreach will improve enforcement and compliance of travel regulations, and installing tortoise-exclusion fencing along highways will reduce road kills and allow tortoise populations to reoccupy depleted areas adjacent to highways. Implementation of these recommendations would improve the prospects of reversing desert tortoise population declines.

Scat as a source of DNA for population monitoring.

Sampling fecal droppings (scat) to genetically identify individual animals is an established method for monitoring mammal populations and could be highly useful for monitoring reptile populations. Whereas existing protocols for obtaining DNA from reptile scat focus on analyses of whole, fresh scat deposited during animal handling, the collection of scat naturally deposited by reptiles in situ, as required for non-invasive population monitoring, requires protocols to extract highly degraded DNA. Using surface swabs from such scats can reduce PCR inhibition and increase genotyping success. We report on three related but independently designed studies of DNA analyses from scat swabs of herbivorous reptiles under natural desert conditions: two free-ranging desert tortoise species (Agassiz's desert tortoise, Gopherus agassizii, California, US, and Morafka's desert tortoise, G. morafkai, Arizona, US) and the common chuckwalla (Sauromalus atar) (Arizona, US, and Sonora, MX). We analyzed samples from both tortoise species with the same set of 16 microsatellites and chuckwalla samples with four mtDNA markers; studies also varied in swab preservation medium and DNA extraction method. Microsatellite amplification success per sample, defined as ≥9 loci with amplification, was 15% for the study of Agassiz's desert tortoise and for the study of 42% Morafka's desert tortoise. For chuckwallas, we successfully amplified and sequenced 50% of samples. We recovered fragments up to 400 bp for tortoises and 980 bp for chuckwallas from scat swab samples. This study indicates that genotypes can successfully be obtained from swabs of scat from herbivorous reptiles collected in the field under natural environmental conditions and emphasizes that repeat amplifications are necessary for the genetic identification of individuals from non-invasive samples.

Habitat use by female desert tortoises suggests tradeoffs between resource use and risk avoidance.

Animals may select habitat to maximize the benefits of foraging on growth and reproduction, while balancing competing factors like the risk of predation or mortality from other sources. Variation in the distribution of food resources may lead animals to forage at times or in places that carry greater predation risk, with individuals in poor quality habitats expected to take greater risks while foraging. We studied Mojave desert tortoises (Gopherus agassizii) in habitats with variable forage availability to determine if risk aversion in their selection of habitat relative was related to abundance of forage. As a measure of risk, we examined tortoise surface activity and mortality. We also compared tortoise body size and body condition between habitats with ample forage plants and those with less forage plants. Tortoises from low forage habitats selected areas where more annual plants were nutritious herbaceous flowering plants but did not favor areas of greater perennial shrub cover that could shelter them or their burrows. In contrast, tortoises occupying high forage habitats showed no preference for forage characteristics, but used burrows associated with more abundant and larger perennial shrubs. Tortoises in high forage habitats were larger and active above ground more often but did not have better body condition. Mortality was four times higher for females occupying low forage habitat than those in high forage habitat. Our results are consistent with the idea that tortoises may minimize mortality risk where food resources are high, but may accept some tradeoff of greater mortality risk in order to forage optimally when food resources are limiting.

Assessing the Impact of a Utility Scale Solar Photovoltaic Facility on a Down Gradient Mojave Desert Ecosystem

A field study was conducted in the Mojave Desert (USA) to assess the influence of a large photo voltaic facility on heat and water transport into an adjacent creosote (Larrea tridentata) bursage (Ambrosia dumosa) plant community. Air temperature, plant physiological status, soil water in storage and precipitation were monitored over a two to four year period. A service road built 27 years before the construction of the PV facility decoupled the wash system at the site leading to a significant decline in soil moisture, canopy level NDVI values and mid-day leaf xylem water potentials (p < 0.001) down gradient from the PV facility. Measurements along a 900 m gradient suggested that plants closer to where the wash was decoupled were placed under significantly greater stress during the higher environmental demand summer months. Air temperatures measured at three 10 m meteorological towers revealed warmer night time temperatures at the two towers located in close association with the solar facility (Inside Facility—IF and Adjacent to facility—AF), compared to the Down Gradient Control tower (DGC). As the warmer air was displaced down gradient, the temperature front advanced into the creosote—bursage plant community with values 5 to 8 °C warmer along an east west front just north of tower AF. Based on our research in Eldorado Valley, NV, USA, a down gradient zone of about 300 m was impacted to the greatest extent (water and heat), suggesting that the spacing between solar facilities will be a critical factor in terms of preserving high quality habitat for the desert tortoise and other species of concern. Greater research is needed to identify habitat zones acceptable for animal populations (especially the desert tortoise) within areas of high solar energy development and this should be done prior to any fragmentation of the ecosystem.

Potential Facilitation Between a Commensal and a Pathogenic Microbe in a Wildlife Disease.

We assessed the potential for microbial interactions influencing a well-documented host-pathogen system. Mycoplasma agassizii is the known etiological agent of upper respiratory tract disease in Mojave desert tortoises (Gopherus agassizii), but disease in wild animals is extremely heterogeneous. For example, a much larger proportion of animals harbor M. agassizii than those that develop disease. With the availability of a new quantitative PCR assay for a microbe that had previously been implicated in disease, Pasteurella testudinis, we tested 389 previously collected samples of nasal microbes from tortoise populations across the Mojave desert. We showed that P. testudinis is a common commensal microbe. However, we did find that its presence was associated with higher levels of M. agassizii among the tortoises positive for this pathogen. The best predictor of P. testudinis prevalence in tortoise populations was average size of tortoises, suggesting that older populations have higher levels of P. testudinis. The prevalence of co-infection in populations was associated with the prevalence of URTD, providing additional evidence for an indirect interaction between the two microbes and inflammatory disease. We showed that URTD, like many chronic, polymicrobial diseases involving mucosal surfaces, shows patterns of a polymicrobial etiology.

COMPUTED TOMOGRAPHY FOR MEASURING BODY FAT RESERVES IN THE THREATENED MOJAVE DESERT TORTOISE (GOPHERUS AGASSIZII).

Noninvasive methods for measuring fat reserves in both captive and free-ranging animals are important for monitoring individual and population health, but chelonian anatomy and physiology present challenges to accurate measurements. Standard field-based methods for assessing body condition in Mojave desert tortoises (Gopherus agassizii) involve the qualitative body condition score, which relies on the apparent height of the temporalis muscle relative to the sagittal crest (in addition to other characteristics) and quantitative body condition indices that measure relative mass at size. However, it is unclear how these metrics relate to body fat reserves in this species. The aims of this study were to (1) describe the use of noninvasive computed tomography in measuring body fat volume of Mojave desert tortoises, (2) describe the location of fat reserves, (3) investigate relationships between fat reserves and body condition score and body condition index, and (4) explore whether relative temporalis muscle depth, measured via computed tomography, correlates with body condition score. Body condition scores were assessed for eight captive Mojave desert tortoises prior to euthanasia, and computed tomography was performed postmortem to quantify fat volume and measure temporalis muscle depth. At necropsy, the distribution of fat was documented. Fat volume calculated by computed tomography ranged from 2.83 to 145.38 cm3 (0.07-2.5% body volume). Neither qualitative body condition score nor quantitative body condition index was correlated with fat volume. Bladder content did not compromise body condition index. Body condition score was not correlated with relative temporalis muscle depth. Computed tomography is a noninvasive method for successfully identifying fat reserves and estimating total fat volume in Mojave desert tortoises. The lack of a relationship between computed tomography-determined metrics and commonly used body condition metrics indicates that computed tomography fills a critical gap in the health assessment tool kit for captive and free-ranging Mojave desert tortoises.

Temperature and Season Influence Phagocytosis by B1 Lymphocytes in the Mojave Desert Tortoise.

Lymphocytes are usually interpreted as functioning in adaptive immunity despite evidence that large proportions of these cells (B1 lymphocytes) have innate immune functions, including phagocytosis, in the peripheral blood of ectothermic vertebrates. We used a recently optimized assay to assess environmental influences on phagocytic activity of lymphocytes isolated from the Mojave desert tortoise (Gopherus agassizii). Previous studies suggest that lymphocytes in this species are associated with reduced pathogen loads, especially in cooler climates, and that lymphocyte numbers fluctuate seasonally. Thus, we evaluated thermal dependence of phagocytic activity in vitro and across seasons. While B1 lymphocytes appeared to be cold-adapted and always increased phagocytosis at cool temperatures, we also found evidence of thermal acclimation. Tortoises upregulated these lymphocytes during cooler seasons in the fall as their preferred body temperatures dropped, and phagocytosis also increased in efficiency during this same time. Like many other ectothermic species, populations of desert tortoises are in decline, in part due to a cold-adapted pathogen that causes chronic respiratory disease. Future studies, similarly focused on the function of B1 lymphocytes, could serve to uncover new patterns in thermal acclimation of immune functions and disease ecology across taxa of ectothermic vertebrates.

Wildlife associates of nine-banded armadillo (Dasypus novemcinctus) burrows in Arkansas.

The Nine‐banded Armadillo (Dasypus novemcinctus) is a widespread burrowing species with an expanding geographic range across the southeastern and midwestern United States. Armadillos dig numerous, large burrows within their home ranges and these burrows are likely used by a diverse suite of wildlife species as has been reported for other burrowing ecosystem engineers such as Gopher Tortoises (Gopherus polyphemus), Desert Tortoises (Gopherus agassizi), and Black‐tailed Prairie Dogs (Cynomys ludovicianus). We used motion‐triggered game cameras at 35 armadillo burrows in 4 ecoregions of Arkansas and documented 19 species of mammals, 4 species of reptile, 1 species of amphibian, and 40 species of bird interacting with burrows. Bobcat (Lynx rufus), Coyote (Canis latrans), Eastern Cottontail (Sylvilagus floridanus), Gray Fox (Urocyon cinereoargenteus), Gray Squirrel (Sciurus carolinensis), Northern Raccoon (Procyon lotor), Virginia Opossum (Didelphis virginiana), and unidentified rodents (mice and rats) were documented using burrows in all four ecoregions. We documented wildlife hunting, seeking shelter, rearing young in, and taking over and modifying armadillo burrows. The rate of use was highest in the Mississippi Alluvial Valley, a landscape dominated by agriculture, where natural refugia may be limited and rodents are abundant. Armadillo burrows are clearly visited and used by numerous wildlife species to fulfill various life stage requirements, and this list will likely expand if more attention is devoted to understanding the role of armadillos burrows. Armadillos are important ecosystem engineers, and their ecological role warrants more investigation and attention as opposed to only being viewed and managed as agricultural and garden pests.

Genetic analyses are more sensitive than morphological inspection at detecting the presence of threatened Mojave desert tortoise (Gopherus agassizii) remains in canid scat and raven pellets

AbstractSubsidization of predator populations increases predation pressure on prey species, which is exacerbated when natural resources are scarce. Estimating the frequency of predation by subsidized predators on vulnerable species, especially low‐density, long‐lived species such as the federally threatened Mojave desert tortoise (Gopherus agassizii), allows landscape managers to evaluate the need for actions like reducing subsidies, discouraging predation by taste aversion, or predator removal. Most studies of Mojave desert tortoise predation have relied on morphological analysis to identify hard parts in predator scat. Here, we developed and validated a qPCR assay to test for the presence of Mojave desert tortoise in DNA extracted from scat and pellets. We used the assay to detect tortoise DNA in scat and pellets collected in a conservation easement adjacent to Boulder City, Nevada, from three Mojave desert tortoise predators: coyotes (Canis latrans), desert kit foxes (Vulpes macrotis arsipus), and common ravens (Corvus corax)—all of which consume anthropogenic resources. We compared the results of our qPCR assay to results from morphological analysis of the same samples and found that the qPCR method is much more sensitive at detecting the presence of tortoise remains. Although neither method can determine whether consumption was the result of predation or scavenging, nor how many individual tortoises were consumed, our findings indicate that conservation managers may benefit from focusing efforts on reducing subsidies that attract and support predators and on reducing tortoise mortality from predation.

Dual-Energy Computed Tomography for Diagnosis and Monitoring Attempted Medical Management of a Large Urate Urolith in a Desert Tortoise (Gopherus agassizii)

An estimated 29-yr-old male zoo-housed desert tortoise (Gopherus agassizii) presented for endoscopic liver biopsies as part of a diagnostic workup for recurrent, profound anemia and hypoalbuminemia. Suspected cystoliths were identified during endoscopy, but were not visible on conventional radiographs. Dual-energy computed tomography (DECT) imaging confirmed the presence of a large urate urolith filling the majority of the bladder. Because of the recent clinical illness, the tortoise was considered a poor surgical candidate. Medical management consisting of urinary alkalinization with potassium citrate, vibration therapy, and daily warm water soaks was elected. Following institution of medical therapies, the tortoise began passing pieces of urate stone that were 0.25–2.0 cm in diameter during daily soaks. A recheck DECT scan at 2 months indicated the urolith was approximately one third the initial size, suggesting medical therapy was effectively treating the urolith. Unfortunately, after 5 months of medical therapy, the stone had increased in size again on the follow-up DECT scan. This case report suggests that medical management may be a potential option for large urate cystoliths in desert tortoises, although more research is needed to further refine effective therapeutics for such cases. The use of DECT imaging was essential in this case because it enabled confirmation of stone presence, identification of urolith composition, and monitoring of response to therapy.

High female desert tortoise mortality in the western Sonoran Desert during California’s epic 2012-2016 drought

We conducted population surveys for desert tortoisesGopherus agassiziiat 2 nearby sites in the western Sonoran Desert of California, USA, from 2015-2018, during the driest ongoing 22 yr period (2000-2021) in the southwestern USA in over 1200 yr. We hypothesized that drought-induced mortality would be female-biased due to water and energy losses attributable to egg production during protracted periods of resource limitation. At the higher-elevation, cooler, wetter Cottonwood site from 2015-2016, the sex ratio of live adult tortoises was biased toward males and the sex ratio of tortoises estimated to have died during the intensified drought conditions from 2012-2016 was essentially even. At the lower-elevation, warmer, drier Orocopia site from 2017-2018, the sex ratio of live adult tortoises was biased toward males and the sex ratio of tortoises with estimated times of death from 2012-2016 was biased toward females. High female mortality at the Orocopia site may have resulted from the interaction of drought effects and the bet-hedging reproductive strategy of tortoises wherein they continue to produce clutches of eggs in drought years. Annual reproductive output results in an estimated loss of up to 13.5% of female tortoise body mass including over 0.20 l of water. Combined with dehydration during severe droughts, these losses may compromise their ability to survive droughts lasting more than 2 yr. The low tortoise density and high mortality of females observed may reflect reduced survival of tortoises near the southern edge of their range due to climate change, including protracted and intensified droughts.

Dual Energy Computed Tomography for Diagnosis and Monitoring Attempted Medical Management of a Large Urate Urolith in a Desert Tortoise (Gopherus agassizii)

An estimated 29-year-old male, desert tortoise ( Gopherus agassizii ) under professional care presented for endoscopic liver biopsies as part of a diagnostic work-up for recurrent, profound anemia and hypoalbuminemia. Suspected cystoliths were identified during endoscopy but were not visible on contemporary radiographs. Dual-energy computed tomography (DECT) imaging confirmed the presence of a large urate urolith filling the majority of the bladder. Due to the recent clinical illness, the tortoise was considered a poor surgical candidate. Medical management consisting of urinary alkalinization with potassium citrate, vibration therapy, and daily warm water soaks was elected. Following institution of medical therapies, the tortoise began passing pieces of urate stone that were 0.25-2.0cm in diameter during daily soaks. A recheck DECT scan at two months indicated the urolith was approximately 1/3 the initial size, suggesting medical therapy was effectively treating the urolith. Unfortunately, after five months of medical therapy, the stone had increased in size again on the follow-up DECT scan. This case report suggests that medical management may be a potential option for large urate cystoliths in desert tortoises, though more research is needed to further refine effective therapeutics for such cases. The use of dual-energy CT imaging was essential in this case as it enabled confirmation of stone presence, identification of urolith composition, and monitoring of response to therapy.

Cytologic and Histologic Findings of Nephroblastoma in a Captive Desert Tortoise (Gopherus agassizii)

A 97-year-old, male, captive desert tortoise ( Gopherus agassizii ) had a 2 month history of lethargy. Imaging with ultrasound, X-ray, and computed tomography revealed a 10-cm-diameter mass in the caudal coelom. Fine needle aspiration revealed spindle and epithelial cell proliferations with formation of rosettes. Exploratory surgery was performed and the mass was removed and submitted for pathology. There was no evidence of metastasis on imaging or at surgery. Histology revealed a mass arising from and compressing the kidney. The mass was composed of primitive glomeruli, tubules, blastemal cells, and mesenchymal cells, features that are diagnostic for nephroblastoma. Tubules were reactive to cytokeratin and mesenchymal cells were reactive to desmin via immunohistochemistry; other immunohistochemical markers were either negative (i.e. S-100) or non-contributory (i.e. epithelial membrane antigen, myogenin, vimentin, and Wilms’ Tumor 1). This is the first report of nephroblastoma in a chelonian.

COMPARISON OF SUBCARAPACIAL SINUS AND BRACHIAL VEIN PHLEBOTOMY SITES FOR BLOOD COLLECTION IN FREE-RANGING GOPHER TORTOISES (GOPHERUS POLYPHEMUS).

Paired blood samples were collected from the brachial vein and subcarapacial sinus of 42 wild gopher tortoises (Gopherus polyphemus) for comparison of hematological and plasma biochemical, vitamin, mineral, and protein electrophoresis parameters with general linear models with repeated measures designs. Comparisons revealed higher brachial vein mean values for 38 of 42 parameters with significance (P ≤ 0.05) for 21 parameters. Significantly lower brachial vein means were noted for two parameters. Coefficients of variation for brachial vein samples were lower for 30 out of 42 parameters with significantly lower values for 11 parameters. Of the 12 parameters with lower coefficients of variation for subcarapacial sinus samples, significant differences were noted for four parameters. Both the lower coefficient of variation and the higher mean values for most parameters from brachial vein samples are attributed to greater hemodilution of subcarpacial samples with lymph compared to the paired brachial vein samples. To address the clinical relevance and reliability of the parameter ranges obtained from both paired phlebotomy sites, we compared these values to those obtained from other selected investigations of gopher tortoise and desert tortoise (Gopherus agassizii) clinicopathology. Although statistically significant differences were detected, available data demonstrated that most mean ± standard deviation values and/or ranges for both phlebotomy sites of our study are similar to those reported for the selected studies. Based on these results, utilization of either set of our study values in the assessment of a gopher tortoise population or individual gopher tortoises would be acceptable for clinical or management decisions. It is also advisable that investigators develop institutional blood parameter ranges for healthy individuals by phlebotomy site when possible in addition to maintaining standardized sample collection and handling protocols.