Article
Ecology
Kristin H. Berry, Jeremy S. Mack, Kemp M. Anderson
Summary: In the Mojave Desert, the availability of water and annual plant foods greatly influence the survival of the threatened Agassiz's desert tortoise. A study involving the translocation of juvenile tortoises found that larger size and access to suitable burrows during extreme temperatures were key factors for survival. Precipitation and forage availability also impacted movements, growth, and home range expansion of the tortoises.
FRONTIERS IN ECOLOGY AND EVOLUTION
(2023)
Article
Ecology
Amanda M. M. Kissel, Bryan Wallace, Jesse Anderson, Brett G. G. Dickson, Kristen Van Neste, Vincent Landau, Roy C. C. Averill-Murray, Linda J. J. Allison, Amy Fesnock
Summary: By analyzing data from the US Fish and Wildlife Service's long-term monitoring program, researchers have found a declining trend in the population dynamics of Mojave desert tortoises from 2001 to 2018, especially in the northeastern part of their range. They developed a Bayesian dynamic occupancy model using various factors to estimate the influence on the tortoise's occupancy dynamics. They also created an online tool for users to explore trends in dynamic occupancy across the species range.
Article
Ecology
Erin R. Zylstra, Linda J. Allison, Roy C. Averill-Murray, Vincent Landau, Nathaniel S. Pope, Robert J. Steidl
Summary: Estimating population density and identifying changing trends is crucial for conservation and management strategies. However, obtaining reliable estimates for rare, long-lived species that are difficult to detect is challenging. In this study, a hierarchical model was developed to estimate density and trends for the Mojave desert tortoise using distance-sampling data. The density of adult tortoises decreased by 1.8% per year over a 20-year period, with the steepest declines in the western range. Overall, the abundance of this threatened species declined by 36% between 2001 and 2020, accounting for habitat loss. This modeling approach provides spatially explicit estimates and guidance for conservation efforts.
Article
Multidisciplinary Sciences
Kirsten E. Dutcher, Kenneth E. Nussear, Jill S. Heaton, Todd C. Esque, Amy G. Vandergast
Summary: Roadways and railways can negatively impact wildlife movements and population connectivity. This study explores the effects of culverts and population density on connectivity using gene flow simulations. The results show that culverts do not completely eliminate the effects of linear barriers, but improve gene flow. Population density is also found to be important for connectivity. The study predicts decreased population connectivity over time due to current anthropogenic disturbance, with detectable genetic and demographic effects within a short period following disturbance.
Article
Multidisciplinary Sciences
M. A. Walden, Kevin J. Loope, Elizabeth A. Hunter, Stephen J. Divers, Jessica R. Comolli, Todd C. Esque, Kevin T. Shoemaker
Summary: This study aims to develop a non-surgical method for sex identification to minimize handling of wild animals. By measuring plasma testosterone concentration in 0-3 months old hatchlings, the study successfully differentiated males from females. Injection of follicle-stimulating hormone (FSH) further elevated testosterone levels in male hatchlings, aiding in sex identification.
SCIENTIFIC REPORTS
(2023)
Article
Multidisciplinary Sciences
Melia G. Nafus, Jacob A. Daly, Tracey D. Tuberville, A. Peter Klimely, Kurt A. Buhlmann, Brian D. Todd
Summary: Animals select habitat based on the benefits of foraging and reproduction while considering factors such as predation risk and mortality. Variations in food distribution may cause animals to forage in riskier areas, with individuals in poor quality habitats taking greater risks. In our study of Mojave desert tortoises, we found that individuals in low forage habitats selected areas with more annual plants, while those in high forage habitats showed no preference for forage characteristics. Tortoises in high forage habitats used burrows associated with larger perennial shrubs. Mortality was higher for females in low forage habitats. Our results suggest that tortoises may tradeoff mortality risk to optimize foraging when food resources are limited.
Article
Veterinary Sciences
Tristan L. Burgess, Josephine Braun, Carmel L. Witte, Nadine Lamberski, Kimberleigh J. Field, Linda J. Allison, Roy C. Averill-Murray, K. Kristina Drake, Kenneth E. Nussear, Todd C. Esque, Bruce A. Rideout
Summary: The study aims to investigate the health status of Mojave Desert tortoises, revealing higher prevalence of upper respiratory tract disease and Mycoplasma infection at the study site LSTS. There is a clear association between clinical signs of URTD and M. agassizii infection, with no significant difference between study sites. Despite the presence of Mycoplasma infection and URTD outside LSTS, the potential for increased incidence if populations were to reconnect must be considered against the benefits of increased connectivity for population viability.
JOURNAL OF WILDLIFE DISEASES
(2021)
Article
Public, Environmental & Occupational Health
Molly J. Bechtel, Karla Kristina Drake, Todd C. Esque, Nathan C. Nieto, Jeffrey T. Foster, Mike B. Teglas
Summary: Ticks transmit pathogens and cause zoonotic diseases, with this report detailing the first cases of tick-borne relapsing fever in people in the Mojave Desert. Contact with tortoises may lead to such diseases, highlighting the importance of precautions in this region.
VECTOR-BORNE AND ZOONOTIC DISEASES
(2021)
Article
Ecology
Erica C. Kelly, Brian L. Cypher, Tory L. Westall
Summary: Desert tortoises are vulnerable to predation by various predators such as desert kit foxes and coyotes, with coyotes consuming more adult tortoises while desert kit foxes prefer juveniles. The study found that these canids primarily consumed small mammals and invertebrates, with desert tortoise remains occurring at a low frequency, indicating opportunistic use of tortoises as prey or scavenged food.
JOURNAL OF ARID ENVIRONMENTS
(2021)
Article
Veterinary Sciences
Elliott R. Jacobson, Kristin H. Berry, Dennis E. Brooks, John F. Roberts
Summary: This case report describes a wild Agassiz's desert tortoise with bilateral eyelid reduction and plaques of tissue covering the corneas. The Polymerase chain reaction (PCR) confirmed the presence of Mycoplasma agassizii in the corneas. The tortoise was later euthanized and necropsied, revealing increased bulbar exposure, periocular scales dermal excoriation, bilateral conjunctivitis, and squamous metaplasia of the bulbar conjunctiva. Mycoplasma testudineum was also identified in the nasal cavities. These findings have not been previously reported in tortoises.
VETERINARY OPHTHALMOLOGY
(2023)
Article
Zoology
Douglas E. Ruby, W. Bryan Jennings, Gilbert Goodlett, James R. Spotila, Henry R. Mushinsky
Summary: In a study to reduce Mojave Desert Tortoise mortality along roadways, researchers tested the feasibility of structures that deter tortoises from walking along barriers or crossing areas with gates or openings. The diversion designs tested were somewhat successful in deflecting tortoises away from fences, but some tortoises still opted to continue walking along barriers. The "tortoise guard" structures, similar to cattle guards, were not completely effective in preventing tortoises from crossing openings, but certain characteristics such as gap sizes and a climbable design were identified as important for an effective structure.
CHELONIAN CONSERVATION AND BIOLOGY
(2023)
Article
Biodiversity Conservation
Lillian D. Parker, Jessica D. Quinta, Isabel Rivera, Brian L. Cypher, Erica C. Kelly, Michael G. Campana, Robert C. Fleischer, Ryan Boarman, William I. Boarman, Jesus E. Maldonado
Summary: Subsidization of predator populations increases predation pressure on prey species. The development and validation of a qPCR assay for detecting Mojave desert tortoise DNA in predator scat have shown that this method is more sensitive than morphological analysis. Conservation managers can benefit from reducing subsidies and predation to improve the protection of the tortoise.
CONSERVATION SCIENCE AND PRACTICE
(2022)
Article
Agriculture, Dairy & Animal Science
Shantanu Kundu, Tanoy Mukherjee, Ah Ran Kim, Soo-Rin Lee, Abhishek Mukherjee, Won-Kyo Jung, Hyun-Woo Kim
Summary: This study reveals lower genetic diversity and more fragmented habitats in India compared to Sri Lanka for the star tortoise, Geochelone elegans. The findings highlight the need for genetic screening, strict measures against wildlife trafficking, and urgent habitat restoration to protect this highly-threatened species.
Article
Veterinary Sciences
Margarete A. Walden, Rachel Jania, Matthew E. Kinney, Anne Devan-Song, K. Kristina Drake, Todd C. Esque, Kevin T. Shoemaker
Summary: This study used noninvasive computed tomography to measure the body fat volume of Mojave desert tortoises and found that there was no correlation between body fat volume and commonly used body condition metrics. Computed tomography fills a critical gap in the health assessment tool kit for Mojave desert tortoises.
JOURNAL OF ZOO AND WILDLIFE MEDICINE
(2022)
Review
Ecology
Gregory A. Geller, Scott L. Parker
Summary: The dynamics of freshwater turtle nest predation by mammalian predators are influenced by various biotic and abiotic factors. Different predators use different cues to locate turtle nests. Most of the existing studies focus on North America, and more research is needed in other regions.
FRONTIERS IN ECOLOGY AND EVOLUTION
(2022)