Habitat Use by Desert Tortoises (Gopherus agassizii) on Alluvial Fans in the Sonoran Desert, South-Central Arizona

Riedle, J. Daren; Averill‐Murray, Roy C.; Lutz, Clayton L.; Bolen, Darren K.

doi:10.1643/ch-06-010

Cited by 33 publications

(28 citation statements)

References 18 publications

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“…Our analyses showed that desert tortoises tended to cross the road near washes. Their preference for crossing near washes may stem from their use of washes as travel corridors (Jennings, 1997;Riedle et al, 2008;Todd et al, 2016), which suggests that efforts to mitigate road effects could be enhanced by focusing on areas where roads intersect washes. The majority of road crossings also occurred at two distinct times, during spring and late summer-early fall.…”

Section: Discussionmentioning

confidence: 99%

“…Because tortoises can use washes as travel corridors (Jennings, 1997;Riedle et al, 2008;Todd et al, 2016) and washes frequently intersect roads, we analyzed locations where tortoises were observed crossing roads to determine whether those locations were non-random with respect to the density of washes along the road. To do this, we first digitized washes from satellite imagery (United States Department of Agriculture, taken 26 May 2014, 1-m resolution).…”

Section: Analyses Of Road Crossingsmentioning

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: Analyses Of Road Crossingsmentioning

confidence: 99%

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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“…Analysis of habitat use is also essential to assess the relevance of the release site [8]. The main natural habitat turtle is considered the forests, fields, open place a succulent plant, but they are not restricted to this habitat [9].…”

Section: Habitat Usementioning

confidence: 99%

Development of Reintroduction Techniques and Population Monitoring of Radiated Tortoises (Astrochelys radiata) in Southern Madagascar: Ampotaka: First Result for 3 Month Acclimatation

Randrianjafizanaka¹,

Felicity²,

Roland³

et al. 2014

OALib

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The radiated tortoise (Astrochelys radiata) of Madagascar is critically endangered with extinction. The Turtle Survival Alliance (TSA) oversees the in-situ captive breeding program for this species and assesses the suitability of reintroduction from captivity as a management strategy is of great importance. 120 adult and juvenile animals from the quarantine center Mangily/Ifaty (30 km north of Toliara) and 24 resident animals from Ampotaka and Tranovaho will be selected in the implementation of the research on the best strategy reintroduction Astrochelys radiata in southern Madagascar, by a soft release of six months and one year (where animals are acclimated to the release site for a pre-determined period) and hard-release. Finally, 90 individuals were destined for a soft release (45 for six months and 45 for one year), 30 individuals for hard release and 24 animals resident population as controls. On 21 January 2014, the first group of 45 animals was transferred to Ampotaka for 1 year of acclimatization. The other 45 will be transferred to the 2nd pen and the latest wave of 30 individuals will be transferred in January 2015. All animals will be radio-tagged and monitored from January 2015 to May 2015. Actually, short-term success will be assessed by investigating survival and pre-release response in body mass, movement and microhabitat use. All 45 reintroduce tortoise survived the duration of this study, remained in pen of pre-release/release and used habitat and resources in a similar way to wild tortoises. S. T. Randrianjafizanaka et al.OALibJ |

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“…They found that 74% of the variance of burrow locations could be explained by proximity to anthropogenic features (roadways and concrete pads to support wind-energy infrastructure) and plant species (L. tridentata, Yucca spp., and Encelia farinosa). Riedle et al [14] found that tortoises in the Sonoran Desert strongly preferred protective geologic features (e.g., incised washes underpinned by petrocalcic horizons, uplands alluvial fan, boulders) over specific vegetation assemblages, but that both geology and vegetation influenced habitat location versus random locations. These studies demonstrate the importance of shrubs or geologic features when tortoises choose locations for burrows, further demonstrating the need to assess spatial patterns of shrubs in this study.…”

Section: Introductionmentioning

confidence: 99%

Airborne LiDAR and Aerial Imagery to Assess Potential Burrow Locations for the Desert Tortoise (Gopherus agassizii)

et al. 2017

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Abstract:The Southwestern United States desert serves as the host for several threatened and endangered species, one of which is the desert tortoise (Gopherus agassizii). The goal of this study was to develop a fine-scale, remote-sensing-based approach that indicates favorable burrow locations for G. agassizii in the Boulder City (Nevada) Conservation Easement area (35,500 ha). This was done by analyzing airborne LiDAR data (5-7 points/m 2 ) and color imagery (four bands, 0.15-m resolution) and determining the percent vegetation cover; shrub height and area; Normalized Difference Vegetation Index (NDVI); and several geomorphic characteristics including slope, azimuth, and roughness. Other field data used herein include estimates of canopy area and species richness using 1271 line transects, and shrub height and canopy area using plant-specific measurements of~200 plants. Larrea tridentata and Ambrosia dumosa shrubs were identified using an algorithm that obtained an optimum combination of NDVI and average reflectance of the four bands (IR, R, G, and B) from pixels in each image. The results, which identified more than 65 million shrubs across the study area, indicate that percent vegetation cover from aerial imagery across the site (13.92%) compared favorably (14.52%) to the estimate obtained from line transects, though the LiDAR method yielded shrub heights approximately 60% those of measured shrub heights. Landscape and plant properties were combined with known locations of tortoise burrows, as visually observed in 2014. Masks were created using roughness coefficient, slope percent, azimuth of burrow openings, elevation, and percent vegetation cover to isolate areas more likely to host burrows. Combined, the masks isolated 55% of the total survey area, which will help target future field surveys. Overall, the approach provides areas where tortoise burrows are more likely to be found, though additional ecological data would help refine the overall method.

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Habitat Use by Desert Tortoises (Gopherus agassizii) on Alluvial Fans in the Sonoran Desert, South-Central Arizona

Cited by 33 publications

References 18 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

Development of Reintroduction Techniques and Population Monitoring of Radiated Tortoises (Astrochelys radiata) in Southern Madagascar: Ampotaka: First Result for 3 Month Acclimatation

Airborne LiDAR and Aerial Imagery to Assess Potential Burrow Locations for the Desert Tortoise (Gopherus agassizii)

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