Gopherus Berlandieri Research Articles

Blood bacterial microbiota of the Texas tortoise, Gopherus berlandieri, in Tamaulipas, Mexico

The blood bacterial microbiota of the Texas tortoise (Gopherus berlandieri) in Tamaulipas, Mexico, was characterized by next-generation sequencing. In 2019, blood was collected from 6 free-living tortoises. DNA was extracted, the V3-V4 region of the 16S rRNA gene was amplified, and Illumina sequencing was performed. The results showed 9 phyla, 20 classes, 42 orders, 81 families, 176 genera and 299 bacterial species. Firmicutes was the most abundant phylum in the blood of G. berlandieri; this taxon has been recorded as predominant in the intestine, excrement, nasal exudates and saliva of other species of the genus Gopherus. The dominant bacterial genera were Caldalkalibacillus, Anaerobacillus, Nesterenkonia and Bacillus. These taxa have been recorded in alkaline and halophilic soils, such as those found in G. berlandieri burrows. All of these bacterial taxa can enter the bloodstream of G. berlandieri via intestinal, oral and nasal translocation. Likewise, 3 bacterial taxa (Coxiella sp., Ehrlichia sp. and Anaplasma phagocytophilum) that are transmitted by arthropod vectors, as well as the potentially pathogenic Salmonella enterica were recorded. This information is the first bacteriological reference for the blood of G. berlandieri, and is expected to be useful for health and conservation programs.

Playing “hide and seek” with Texas tortoises: value of a detector dog

Texas tortoises (Gopherus berlandieri) were once considered common and abundant throughout southern Texas with densities as high as 16 tortoises per hectare. Today, density estimates are 0.25 tortoises per hectare, which constitutes about a 98% population decline. Because of their low numbers and elusive behavior, Texas tortoises can be difficult to find. We demonstrate the value of using a detector dog as a time saving method in locating Texas tortoises. We glued VHF radio transmitters onto 9 adult tortoises and released them in a 5-ha plowed and short-grass pasture that contained mesquite (Prosopsis glandulosa) mottes, habitat conducive for Texas tortoise habitat selection. We calculated the Detectability Index (DI) as the detection rate (# tortoises found/minute) × percent tortoises from the known population found within 60 minutes. We compared DIs via telemetry, detector dog, and “cold” (no equipment or knowledge) human searches. We used the time required to find all tortoises when a searcher had knowledge of locations as the baseline. Our baseline DI was 0.79, followed by telemetry (0.13) and detector dogs (0.11), while “cold” searches was 0.02. Telemetry, detector dog, and cold searches were 6-fold, 7-fold, and nearly 40-fold slower, respectively, than having knowledge of tortoise locations. However, the combination of using detector dogs with telemetry resulted in a 50% time savings than single methods. Telemetry was useful in locating a generalized area with a tortoise but a detector dog was 2X faster in visually locating the tortoise once the area was identified. Therefore, we recommend the use of detector dogs as a time-saving method when conducting research on Texas tortoises.

Validation of an Enzyme-Linked Immunosorbent Assay and Establishment of a Reference Interval for Androstenedione in Texas Tortoises (Gopherus berlandieri)

Validation of an Enzyme-Linked Immunosorbent Assay and Establishment of a Reference Interval for Androstenedione in Texas Tortoises (Gopherus berlandieri)

What is your diagnosis? Blood smear review in a Texas tortoise (Gopherus berlandieri).

What is your diagnosis? Blood smear review in a Texas tortoise (Gopherus berlandieri).

CLINICAL OPHTHALMIC PARAMETERS OF THE TEXAS TORTOISE (GOPHERUS BERLANDIERI).

Ophthalmic studies of the Texas tortoise (Gopherus berlandieri) established normal ophthalmic parameters for select diagnostic tests in captive tortoises and assessment of differences among individuals of differing size and health status. Sixty-one tortoises of varying weight, shell size, Mycoplasma seroprevalence, and herpesvirus exposure were included. Complete ophthalmic examinations, including neuro-ophthalmic reflexes, phenol red thread test, rebound tonometry, fluorescein staining, palpebral fissure length measurement, slit lamp biomicroscopy, indirect fundoscopy, and ocular ultrasound measurements of axial globe length, anterior chamber depth, lens thickness, and vitreous length, were recorded. All tortoises had negative dazzle and pupillary light reflexes, inconsistent menace responses, and positive palpebral reflexes. Mean ± SD tear production and intraocular pressure (IOP) were 14.2 ± 5.6 mm/15 sec and 13.8 ± 2.4 mm Hg in healthy tortoises, respectively. Mycoplasma-seropositive tortoises (with or without herpesvirus exposure) had significantly increased tear production (20.2 ± 8.1 and 19.9 ± 8.9 mm/15 sec, respectively) compared with healthy seronegative tortoises (14.2 ± 5.6 mm/15 sec; P = 0.02). As body size decreased, so too did palpebral fissure length and ocular ultrasound measurements, while IOP increased. Overall, palpebral fissure length appeared relatively small, and tear production relatively increased compared with other chelonian species, likely on the basis of the relatively arid native habitat. Further work is recommended to establish baseline values in related species, as well as comparison in aquatic versus terrestrial chelonians. The authors further suggest that the finding of relatively increased tear production in tortoises may indicate the need to rule out mycoplasmosis as a cause of upper respiratory tract disease.

Successful correction of a prefemoral hernia with free coelomic yolk in a Texas tortoise (Gopherus berlandieri)

An approximately 10-year-old female Texas tortoise (Gopherus berlandieri) with a large right prefemoral fossa mass was presented after brumation. Based on CT and fine needle aspiration, the animal was diagnosed...

Co-infection does not predict disease signs in Gopherus tortoises.

In disease ecology, the host immune system interacts with environmental conditions and pathogen properties to affect the impact of disease on the host. Within the host, pathogens may interact to facilitate or inhibit each other's growth, and pathogens interact with different hosts differently. We investigated co-infection of two Mycoplasma and the association of infection with clinical signs of upper respiratory tract disease in four congeneric tortoise host species (Gopherus) in the United States to detect differences in infection risk and disease dynamics in these hosts. Mojave Desert tortoises had greater prevalence of Mycoplasma agassizii than Texas tortoises and gopher tortoises, while there were no differences in Mycoplasma testudineum prevalence among host species. In some host species, the presence of each pathogen influenced the infection intensity of the other; hence, these two mycoplasmas interact differently within different hosts, and our results may indicate facilitation of these bacteria. Neither infection nor co-infection was associated with clinical signs of disease, which tend to fluctuate across time. From M. agassizii DNA sequences, we detected no meaningful differentiation of haplotypes among hosts. Experimental inoculation studies and recurrent resampling of wild individuals could help to decipher the underlying mechanisms of disease dynamics in this system.

Habitat Space Used by Northern Bobwhites and Texas Tortoises on South Texas Rangelands

South Texas rangelands are increasingly managed for recreational hunting, particularly northern bobwhite (Colinus virgianus). Effects of habitat management for game species on non-game species are largely unknown. Large private ranches used for recreational hunting could also provide habitat for the threatened Texas tortoise (Gopherus berlandieri). We studied habitat use of Texas tortoises and northern bobwhites on a private ranch in South Texas that undergoes active habitat management. In 2015, tortoises (n = 12) and bobwhite hens (n = 42) were tracked during their active and breeding seasons, respectively, with radio-telemetry. Satellite images were analyzed using ArcGIS 10.3 to delineate habitat through unsupervised classification for relevant habitat categories. Habitats were delineated based on reflectance. Differences in percent habitat composition of observed and random home ranges (100% Minimum Convex Polygon) of tortoises were not significant, but were significant for quail in 3 of 5 habitat categories in only 1 of 2 pastures. These observed quail home ranges included more areas corresponding to light woody cover and moderate herbaceous cover and fewer areas corresponding to sparsely vegetated or bare ground than random home ranges. Tortoise home ranges included more areas with woody brush cover than bobwhite home ranges. Bobwhite home ranges included more areas associated with moderate grass and herbaceous cover than tortoises. This study will continue in 2016 and will include more quail home ranges in areas with tortoises. This research seeks to determine the compatibility of managing for recreational hunting while maintaining landscape characteristics important to Texas tortoises.

The Texas Tortoise: A Natural History by Francis L. Rose, Frank W. Judd

Reviewed by: The Texas Tortoise: A Natural History by Francis L. Rose, Frank W. Judd David C. Rostal The Texas Tortoise: A Natural History. By Francis L. Rose and Frank W. Judd. Norman: University of Oklahoma Press, 2014. vii + 188 pp. Figures, tables, maps, references, index. $39.95 cloth. The Texas Tortoise covers the life work of Drs. Rose and Judd, who spent much of their scientific careers studying this ancient survivor. It provides a wealth of information on this species but also warns us of its plight. Included are many black-and-white figures and drawings as well as two sets of excellent color photographs. The preface provides insight into the authors’ motivation for undertaking this project. In the introduction, I enjoyed reading the history of the early naturalist Jean Louis Berlandier, after whom the tortoise would later be named. In each successive chapter that follows, the authors explain the natural history and biology of the Texas tortoise in a way that readers will enjoy. Chapter 1 not only describes the relationships between the five currently recognized species of North American tortoises but also explains the complexity of determining a genus and species. Chapter 2 follows with an in-depth description of the species’ range and habitat. North American tortoises once traveled throughout the Great Plains of North America during the Pleistocene but are now restricted to more southern habitats. We know little about the species in the southern part of its range in Mexico. Following chapters discuss aspects of the Texas tortoise’s biology and allude to areas that need further research or study. These chapters also cover reproduction, sexual size dimorphism, growth, temperature regulation, and population ecology. The work concludes with a discussion of conservation and the future of the Texas tortoise, which is experiencing the same declines witnessed for turtles and tortoises around the world. I especially enjoyed the way the authors inserted anecdotes from the past. The book provides a thorough coverage of our understanding of the Texas tortoises but occasionally falls short in its current coverage of more recent literature on North American tortoises. There is some redundancy, but it is limited and does not hinder the flow of the book. That being said, I found its coverage of early foundational papers by early scientists such as Walter Auffenberg to be enlightening. The authors in some cases express their strong personal opinions regarding aspects of the biology and conservation of the Texas tortoises, which I appreciated. Many of these classic papers are hard to access today in our modern world of electronic literature. From that standpoint alone it is a book anyone interested in tortoises or turtles will want to have in their library. I have thoroughly enjoyed reading the book and know I will find it an important reference in my personal library. The Texas Tortoise is a must for anyone interested in tortoises or herpetology. David C. Rostal Department of Biology Georgia Southern University Copyright © 2016 Center for Great Plains Studies, University of Nebraska–Lincoln

Detection of Mycoplasma agassizii in the Texas Tortoise (Gopherus berlandieri)

Mycoplasma agassizii causes upper respiratory tract disease (URTD) in Texas tortoises (Gopherus berlandieri). To determine exposure to and shedding of M. agassizii, we collected blood samples and nasal swabs from 40 free-ranging Texas tortoises on public and private lands in Texas, USA, from May to October 2009. We used an enzyme-linked immunosorbent assay (ELISA) to detect M. agassizii-specific antibodies. Eleven (28%) tortoises were antibody positive, three (8%) were suspect, and the remaining 26 (65%) were negative. Nasal lavage samples were collected from 35 of the 40 tortoises for M. agassizii culture and PCR to detect shedding of M. agassizii. Current infection with M. agassizii was confirmed in one tortoise that had mild clinical signs of URTD and was positive by ELISA (antibody titer >512), PCR, and culture. The clinical isolate was confirmed as M. agassizii by restriction fragment length polymorphism and immunobinding.

Isolation and characterization of polymorphic microsatellite loci for the gopher tortoise (Gopherus polyphemus) and cross-amplification in other species of Gopherus

All members of the tortoise genus Gopherus have some degree of conservation concern. We report on the development of thirty-two new microsatellite loci for gopher tortoise, which were tested on 31 individuals from Ft. Benning, Georgia, USA. These loci possessed an average number of 5.09 alleles, an average observed heterozygosity of 0.574 and an average expected heterozygosity of 0.589. We also tested these loci in three congeners: Gopherus morafkai, Gopherus flavomarginatus and Gopherus berlandieri. The new microsatellite loci should prove useful in conservation efforts of Gopherus polyphemus and other Gopherus species.

Survivorship in Two Coastal Populations of Gopherus berlandieri

Abstract We studied two closely situated (6.4 km distance) coastal populations of the Gopherus berlandieri in Cameron County, Texas. The Yturria Ranch population was monitored from 1972 through 1987, and the Reed Ranch population was monitored from 1977 through 1987. Tortoises were located by searching between grid lines 18.3 m apart that encompassed 3.3 ha on the Yturria Ranch and 2.0 ha on the Reed Ranch. Nine (3.7%) of 244 tortoises marked on the Yturria Ranch and 16 (10.5%) of 151 marked on the Reed Ranch died during the study. Timing of known deaths were distinctly different for the two sites, with nine tortoises found dead on the Yturria Ranch from 1983–87, whereas all known tortoise deaths occurred on the Reed Ranch from 1977–79. Annual survivorship estimates were higher for males and females on the Yturria Ranch, but survivorships at both sites were similar. Abundance of prickly pear (Opuntia engelmannii), on which tortoises feed, on the Yturria Ranch site may have contributed to a higher survivor...

Genetic Variation and Population Structure of the Texas Tortoise, Gopherus berlandieri (Testudinidae), with Implications for Conservation

Abstract The Texas tortoise (Gopherus berlandieri) is a state-protected, threatened species in Texas. The expansion of agricultural practices and urban development are major causes of habitat degradation for the species. To provide genetic data that can inform conservation planning for this species, genetic variation, population structure, and the process that maintains the observed structure were examined in the Texas populations of G. berlandieri. Microsatellite genetic variation of 8 polymorphic loci was examined for a total of 138 individuals collected from 10 sampling areas in southern Texas. Assignment tests, F statistics, and analysis of molecular variance indicated that G. berlandieri forms weak population differentiation into northern and southern groups, with a boundary at southern Duval County. A test of isolation by distance and indirect estimation of the number of migrants (Nm) suggest recent gene flow between the 2 groups. Estimation of the extent of contemporary migration appears to be comp...

Tracing Genetic Lineages of Captive Desert Tortoises in Arizona

Abstract: We genotyped 180 captive desert tortoises (Gopherus agassizii) from Kingman (n = 45), Phoenix (n = 113), and Tucson (n = 22), Arizona, USA, to determine if the genetic lineage of captives is associated with that of wild tortoises in the local area (Sonoran Desert). We tested all samples for 16 short tandem repeats and sequenced 1,109 base pairs of mitochondrial DNA (mtDNA). To determine genetic origin, we performed assignment tests against a reference database of 997 desert tortoise samples collected throughout the Mojave and Sonoran Deserts. We found that >40% of our Arizona captive samples were genetically of Mojave Desert or hybrid origin, with the percentage of individuals exhibiting the Mojave genotype increasing as the sample locations approached the California, USA, border. In Phoenix, 11.5% were Sonoran–Mojave crosses, and 8.8% were hybrids between desert tortoise and Texas tortoise (G. berlandieri). Our findings present many potential implications for wild tortoises in the Sonoran Desert of Arizona. Escaped or released captive tortoises with Mojave or hybrid genotypes have the potential to affect the genetic composition of Sonoran wild populations. Genotyping captive desert tortoises could be used to inform the adoption process, and thereby provide additional protection to native desert‐tortoise populations in Arizona.

Seroprevalence of Mycoplasma agassizii in Wild Caught and Rescued Texas Tortoises (Gopherus berlanderi) in South Texas

The Texas tortoise (Gopherus berlanderi) is one of four native tortoise species found in North America. All four Gopherus species receive some form of government protection because of recent population declines. The Texas tortoise is considered threatened within the state of Texas and is of major conservation interest. As a result of human encroachment into Texas tortoise habitats, there has been an increase in the dissemination of infectious disease into native populations. One of the most important diseases studied in North American tortoises is Mycoplasma agassizii. Seroprevalence studies have been performed in the California desert tortoise (Gopherus agassizii) and Gopher tortoise (Gopherus polyphemus) but have yet to be performed in the Texas tortoise. The purpose of this study was to measure the seroprevalence of Mycoplasma agassizii using an ELISA in two populations of Texas tortoises, a wild population (N = 39) and a population in a wildlife rehabilitation facility (N = 15). Tortoises in the wild population were all seronegative (95% confidence intervals [CI]: 0–7.6%), whereas 80% (12/15; 95% CI: 60–100) of the tortoises from the rehabilitation facility were seropositive. The results of this study suggest that Texas tortoises are exposed to and can mount an immunoglobulin response to Mycoplasma agassizii, which may influence the status of this species in North America. This pilot study suggests that further research is needed to determine the epidemiology of mycoplasmosis in Texas tortoises from the wild and in captivity.

TEXAS TORTOISE (GOPHERUS BERLANDIERI) CONSUMED BY A MOUNTAIN LION (PUMA CONCOLOR) IN SOUTHERN TEXAS

Mountain lions (Puma concolor), throughout their distribution, eat a variety of prey, but primarily consume large prey (e.g., cervids). While monitoring radio-collared mountain lions, we saw a mountain lion kitten consuming a Texas tortoise (Gopherus berlandieri). Small prey might increase survival of young mountain lions developing predation skills required for solitary survival as adults.

Habitat Selection by the Texas Tortoise in a Managed Thornscrub Ecosystem

Brush encroachment on semiarid shrublands resulting from livestock grazing has created global concern. Southern Texas is dominated by Prosopis-Acacia mixed brush communities typical of the Tamaulipan Biotic Province, and the geographic range of the state-threatened Texas tortoise (Gopherus berlandieri) is nearly identical to the boundaries of this biotic province in Texas. In light of the perceived threat to Texas tortoises because of habitat change caused by brush encroachment, we monitored 36 Texas tortoises by radiotelemetry during 1994-1996 to assess habitat selection on a site containing grazed and ungrazed pastures. Tortoises did not exhibit habitat selection at the level of locations within home ranges. Differential habitat selection at the level of home ranges within study areas was not apparent for sex, but was evident for treatment (grazed or ungrazed). Analysis of pooled data indicated that tortoises exhibited broad-scale selection for home ranges within study areas. Selection was expressed as preferential avoidance of old-field and riparian habitats, which represented vegetational extremes of canopy cover. However, tortoises tolerated the broad continuum of other brush communities on the study site. Apparent treatment differences may be an artifact of our inability to adequately pair study areas given the scale of tortoise movement. Our data indicate that increases in the extent of woody canopy cover resulting from grazing-induced brush encroachment will not be detrimental to Texas tortoises. Furthermore, large-scale range improvement practices, such as root-plowing, create unsuitable habitats for this species.

Mark-Recapture Analysis of Population Parameters in a Texas Tortoise (Gopherus berlandieri) Population in Southern Texas

Techniques to assess population changes in reptiles across large landscapes are a conservation and management need. We studied a population of Texas tortoises (Gopherus berlandieri) on a large study area (6150 ha) of contiguous thornscrub vegetation in southern Texas from 1990 to 1999. We examined cohort and temporal variation in capture probabilities; and estimated survival, population size, and A (finite pop- ulation growth rate) for a population of Texas tortoises. We captured 2128 tortoises a total of 3132 times during the study period. The distribution of the frequency of captures by sex varied during the active season and across years, but annual capture probabilities were similar between sexes. The ratio of juvenile to adults varied by a month-by-year interaction. Tortoises exhibited a temporary response to marking that was modeled in survival analysis. Capture probabilities of adult tortoises on an annual basis ranged from 0.12-0.38, and annual survival rate of adults was estimated to be 0.79 ? 0.05. We estimated the density of the adult population to be 0.26 tortoises/ha, a level of magnitude lower than previous work conducted on habitat islands. Lambda (population growth rate) was estimated to be 0.981 (95% confidence limits: 0.945- 1.019) from a Jolly-Seber model. Road-cruising was an effective large-scale method for population moni- toring of the Texas tortoise in our study area and may prove useful in thornscrub habitats that compose the majority of its geographic range.

Effects of Grazing on the Demography and Growth of the Texas Tortoise

Abstract: Considerable effort has been exerted in attempts to understand the complex ecological effects of grazing. North American tortoises, by virtue of their distribution, provide a good model taxon through which to study how grazing effects vary with grazing regime, habitat, and climate. We studied the Texas tortoise ( Gopherus berlandieri ), which is restricted primarily to privately owned rangelands of southern Texas and northeastern Mexico. Management of this species is hampered by a lack of information on the effects of common land‐use practices. We evaluated the effects of moderate grazing by cattle (short‐duration, winter‐spring rotational grazing regime; 6–28 animal‐unit days/ha/year) on this tortoise by comparing two grazed and two ungrazed sites in the Western Rio Grande Plains, Texas ( U.S.A.), from April 1994 to October 1997. We made 132 captures of 106 individuals in the ungrazed pastures and 324 captures of 237 individuals in the grazed pastures. We also radiotracked 22 tortoises in the ungrazed pastures and 25 tortoises in the grazed pastures. Comparisons of relative abundance, body‐size distribution, age distribution, body mass, sex ratio, adult survival, proportion of juveniles, and growth rates revealed no differences ( p> 0.05 for all parameters) between tortoises on grazed and ungrazed areas. Based on these results, we suggest that moderate grazing by cattle is not incompatible with maintenance of Texas tortoise populations. Our data were consistent with a general model of tortoise biogeography and tolerance of disturbance which suggests that Texas tortoises are tolerant to intermediate levels of disturbance. Generalities about the effect of cattle grazing on the four North American tortoises should be avoided unless they can be placed in the context of grazing regime, precipitation, habitat quality, and tortoise requirements.

Patterns of behavior in the Texas tortoise, Gopherus berlandieri: a multivariate ordination approach

We compared the distribution of 19 categories of behavior exhibited by 47 adult Texas tortoises (Gopherus berlandieri) over 3 years with the use of detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA). DCA revealed a gradient from passive to active behavior along axis 1. Tortoises were more active in 1994 and less active in 1996. This pattern was likely due to the extremely hot and dry conditions in 1996. Year was the most significant variable explaining variability in behavior when sex, age, size, year, and grazing treatment (pastures grazed versus ungrazed by cattle) were used as environmental variables in CCA. Age, size, and grazing treatment were not significant variables in CCA. Tortoises used proportionally more burrows, shallow surface depressions termed pallets, and cavity pallets, and ate more cactus in 1996. More foraging and active behaviors, like courtship, were observed in 1994. Sex was a significant variable in explaining behavioral variability after the effects of year were controlled for. Males tended to exhibit more active behaviors than females. Our analyses suggested that the grazing regime used in Chaparral Wildlife Management Area did not affect the patterns of behavior exhibited by this protected tortoise.