Thermal Ecology of Desert Tortoises in the Eastern Mojave Desert: Seasonal Patterns of Operative and Body Temperatures, and Microhabitat Utilization

Zimmerman, Linda C.; O’Connor, Michael; Bulova, Susan J.; Spotila, James R.; Kemp, Stanley J.; Salice, Christopher J.

doi:10.2307/1467069

Cited by 95 publications

(99 citation statements)

References 10 publications

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“…As animals paced along a fence, carapace temperatures would, in some instances, exceed 43°C. For example, one female tortoise was found pacing the fence on 28 August in the late afternoon, a time when desert tortoises are typically at rest in the shade of their burrows (Zimmerman et al, 1994). When the same tortoise was observed the following day, it was found along the fence dead.…”

Section: Discussionmentioning

confidence: 99%

“…The mean location error of the GPS loggers was 8.6 m (range 3-38 m) as determined by previous field trials. With desert ectotherms, behavioral thermoregulation within physiological limits is critical for movement, water balance, foraging efficiency, reproduction, and overall survival (Brand et al, 2016;Zimmerman et al, 1994;Nagy and Medica, 1986). Previously, carapace temperatures have been used as a proxy for internal body temperatures for the desert tortoise (Zimmerman et al, 1994;Brand et al, 2016).…”

Section: Data Collectionmentioning

confidence: 99%

“…With desert ectotherms, behavioral thermoregulation within physiological limits is critical for movement, water balance, foraging efficiency, reproduction, and overall survival (Brand et al, 2016;Zimmerman et al, 1994;Nagy and Medica, 1986). Previously, carapace temperatures have been used as a proxy for internal body temperatures for the desert tortoise (Zimmerman et al, 1994;Brand et al, 2016). To understand the thermal ecology of desert tortoises near and away from structures, we affixed iButton temperature loggers to the first right or first left costal scute of each study animal with epoxy putty (J-B Weld SteelStik).…”

Section: Data Collectionmentioning

confidence: 99%

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Effects of roads and roadside fencing on movements, space use, and carapace temperatures of a threatened tortoise

Peaden

Nowakowski

Tuberville

et al. 2017

Biological Conservation

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A B S T R A C TRoads are widespread features of many landscapes that can negatively affect wildlife, most notably through animal-vehicle collisions. Roadside fencing has increasingly been installed to help eliminate this source of mortality. While fencing may reduce road mortality, other types of wildlife responses to this novel barrier are not well understood. Here, we examined the movement behavior, space use, and carapace temperatures of Mojave Desert Tortoises (Gopherus agassizii) as they interacted with a roadside fence and an unfenced road. Using GPS loggers, we tracked tortoise movements for two years at 15-min intervals. We found that carapace temperatures were greater near structures (fence or unfenced road) than away from structures; tortoises near the unfenced road had higher mean carapace temperatures, but tortoises along the fence experienced more extreme upper temperatures that approached the species' thermal limit. Movement speeds were also higher along the structures than away from them. Tortoise home range sizes decreased with proximity to the fence or road; fragmentation of home ranges and road-crossing avoidance may have contributed to smaller home ranges along the fenced and unfenced road, respectively. While tortoises crossed the road significantly less than expected by chance, they did so primarily in May and July and in areas with washes, indicating that placement of roadside fencing and animal underpasses could be optimized by targeting areas where roads intersect washes. Taken together, our results suggest that roadside fencing can affect behavior, space use, and thermal ecology of tortoises, which may require refinements to future conservation strategies involving roadside fencing.

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Section: Discussionmentioning

confidence: 99%

Section: Data Collectionmentioning

confidence: 99%

Section: Data Collectionmentioning

confidence: 99%

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Effects of roads and roadside fencing on movements, space use, and carapace temperatures of a threatened tortoise

Peaden

Nowakowski

Tuberville

et al. 2017

Biological Conservation

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“…The annual cycle of above-ground activity for tortoises varies according to location within the geographic range and depends on such environmental factors as number of freezing days per annum, timing and amounts of precipitation, day-and night-time temperatures, and the type of desert (FWS, 1994). The exact timing of above ground activity is also dependent on availability of forage, local weather patterns, and ambient daytime temperatures (Nagy and Medica, 1986;Ruby et al, 1994;Zimmerman et al, 1994;Henen, 1997), as well as the size and age of tortoises (Berry and Turner, 1986).…”

Section: Preparations For the Fieldmentioning

confidence: 99%

“…During the activity season (March-October), most tortoises should be alert and responsive under normal operating temperatures (Berry and Turner, 1986;Zimmerman et al, 1994), and able to withdraw head and limbs quickly and tightly into the shell when prodded. If environmental temperatures are at or near freezing, or skies are overcast and weather generally cold, the responses of a normal, healthy tortoise will be slower.…”

Section: The Health Profile Formmentioning

confidence: 99%

Guidelines for the Field Evaluation of Desert Tortoise Health and Disease

Berry

Christopher

2001

Journal of Wildlife Diseases

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Field evaluation of free-ranging wildlife requires the systematic documentation of a variety of environmental conditions and individual parameters of health and disease, particularly in the case of rare or endangered species. In addition, defined criteria are needed for the humane salvage of ill or dying animals. The purpose of this paper is to describe, in detail, the preparation, procedures, and protocols we developed and tested for the field evaluation of wild desert tortoises (Gopherus agassizii). These guidelines describe: preparations for the field, including developing familiarity with tortoise behavior and ecology, and preparation of standardized data sheets; journal notes to document background data on weather conditions, temperature, rainfall, locality, and historic and recent human activities; procedures to prevent the spread of disease and parasites; data sheets for live tortoises to record tortoise identification, location, sex, body measurements and activity; health profile forms for documenting and grading physical abnormalities of tortoise posture and movements, general condition (e.g., lethargy, cachexia), external parasites, and clinical abnormalities associated with shell and upper respiratory diseases; permanent photographic records for the retrospective analysis of progression and regression of upper respiratory and eye diseases, analysis of shell lesions and evaluation of growth and age; and indications and methods for salvaging ill or dying tortoises for necropsy evaluation. These guidelines, tested on 5,000 to 20,000 tortoises over a 10 to 27 yr period, were designed to maximize acquisition of data for demographic, ecological, health and disease research projects; to reduce handling and stress of individual animals; to avoid spread of infectious disease; to promote high quality and consistent data sets; and to reduce the duration and number of field trips. The field methods are adapted for desert tortoise life cycle, behavior, anatomy, physiology, and pertinent disease; however the model is applicable to other species of reptiles. Comprehensive databases of clinical signs of disease and health are crucial to research endeavors and essential to decisions on captive release, epidemiology of disease, translocation of wild tortoises, breeding programs, and euthanasia.

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Field Physiology: Studying Organismal Function in the Natural Environment

Williams

Hindle

2021

Comprehensive Physiology

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Thermal Ecology of Desert Tortoises in the Eastern Mojave Desert: Seasonal Patterns of Operative and Body Temperatures, and Microhabitat Utilization

Cited by 95 publications

References 10 publications

Effects of roads and roadside fencing on movements, space use, and carapace temperatures of a threatened tortoise

Effects of roads and roadside fencing on movements, space use, and carapace temperatures of a threatened tortoise

Guidelines for the Field Evaluation of Desert Tortoise Health and Disease

Field Physiology: Studying Organismal Function in the Natural Environment

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