How far can a tortoise walk in open habitat before overheating? Implications for conservation

Moulherat, Sylvain; Delmas, Virginie; Slimani, Tahar; Mouden, El Hassan El; Louzizi, Tarik; Lagarde, Frédéric; Bonnet, Xavier

doi:10.1016/j.jnc.2013.11.004

Cited by 30 publications

(33 citation statements)

References 45 publications

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“…If thermally moderated sites are juxtaposed so that they are distant from one another, the potential for ecological traps could be high for species seeking thermal refuge during the heat of the day or during extreme heat events. For example, due to their limited mobility, Moorish tortoises (Testudo graeca) in Morocco require thermal refuges within 0.5 km of their diurnal position during hot summer conditions to avoid heat stress (Moulherat et al 2014). Characterizations of thermal landscapes such as those in this study combined with behavioral and physiological data could serve to answer questions about how environmental conditions may induce ecological traps for species now and in the future.…”

Section: Discussionmentioning

confidence: 98%

“…For example, due to their limited mobility, Moorish tortoises ( Testudo graeca ) in Morocco require thermal refuges within 0.5 km of their diurnal position during hot summer conditions to avoid heat stress (Moulherat et al. ). Characterizations of thermal landscapes such as those in this study combined with behavioral and physiological data could serve to answer questions about how environmental conditions may induce ecological traps for species now and in the future.…”

Section: Discussionmentioning

confidence: 99%

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Landscape pattern is critical for the moderation of thermal extremes

et al. 2016

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Abstract. Temperature is highly variable across space and time at multiple scales, shapes landscape pattern, and dictates ecological processes. While our knowledge of ecological phenomena is vast relative to many landscape metrics, thermal patterns which shape landscape mosaics are largely unknown. To address this disconnect, we investigated the thermal landscape by measuring black bulb temperature (T bb ) at intervals as small as 15 min across 3 yr in a mixed-grass shrub vegetation community. We found that the thermal landscape was highly heterogeneous displaying a prevalence for thermal extremes (i.e., T bb > 50°C) and that T bb was driven by the synergism of environmental, terrain, and vegetation factors. Specifically, variation of T bb on the landscape was best predicted by the inclusion of ambient temperature (T air ), solar radiation (S rad ), low woody cover, and tall woody cover as variables. Moreover, models of single vegetation parameters (i.e., bare ground, low woody, or tall woody cover) each had greater relative importance than those containing a single terrain variable (i.e., slope or aspect) based on AIC, providing evidence that vegetation is a key driver of T bb on the landscape. Within the thermally heterogeneous landscape, tall woody cover moderated T bb by 10°C more than bare ground, herbaceous, or low woody cover during peak diurnal heating (14:00), and was the only cover type that remained <50°C on average. Given that tall woody cover comprises only about 7% of the landscape in our study, these findings have direct conservation implications for species inhabiting shrub communities, specifically that the distribution of tall woody cover is a spatially limited but key predictor of potential thermal refugia on the landscape. Our findings also demonstrate that local interactions between vegetation and temperature can create thermal patterns that shape dynamic landscape mosaics across space and time. Furthermore, we show that structural heterogeneity can maximize thermal complexity across landscapes which can provide greater potential thermal options for organisms. However, our modeled climate projections suggest that far greater thermal extremes will be possible across increasingly larger swaths of the landscape in the future, making assessments and quantifications of thermal landscapes increasingly critical.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Landscape pattern is critical for the moderation of thermal extremes

et al. 2016

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“…Lowered activity can benefit aridadapted species by reducing evaporative water loss and other metabolic expenditures when water is scarce [57,58]. Although species such as the desert tortoise can escape some thermal or metabolic challenges created by water scarcity by retreating into burrows, not all arid tortoise species burrow and many species face substantial challenges in metabolic maintenance as habitat is degraded and temperatures increase [59,60]. Reduced activity in juvenile tortoises in the present study also resulted in fewer foraging and basking behaviors even when green plants were available.…”

Section: Discussionmentioning

confidence: 99%

Precipitation quantity and timing affect native plant production and growth of a key herbivore, the desert tortoise, in the Mojave Desert

Nafus

Tuberville

Buhlmann

et al. 2017

Clim Chang Responses

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Background: Deserts may be disproportionately vulnerable to changes in precipitation that accompany global climate change due to complex evolutionary relationships of species to historical conditions. Based on current and projected climate scenarios for the southwestern United States, we manipulated rainfall timing and quantity and measured the response by plants and the growth and behavior of the desert tortoise (Gopherus agassizii) to precipitation in the eastern Mojave Desert. Results: We found that winter-dominant rain -the current prevailing pattern in the eastern Mojave Desert -and greater total rainfall correlated with greater cover and species richness of plants. Winter-dominant rain also correlated with a higher proportion of native plants flowering relative to invasive plants. Juvenile tortoises grew more rapidly when they were subjected to rainfall treatments that associated with increased plant abundance and species richness, while their behavior appeared more driven by water availability. Conclusions: Our results suggest that precipitation timing may be as important as rainfall quantity when considering total effects of climate change on arid-adapted systems. Further research should explore how the timing of rainfall may interact with aridity or temperature to influence total effects due to climate change on arid communities.

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“…This measureable behavioral response to translocation may challenge translocation efforts irrespective of whether a tortoise exhibits homing. Such increased movements may influence ability to breed successfully (Tuberville et al 2011), affect survivorship (Tuberville et al 2008) or have physiological consequences (Moulherat et al 2014).…”

Section: Discussionmentioning

confidence: 99%

The effects of homing and movement behaviors on translocation: Desert tortoises in the western Mojave Desert

et al. 2014

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Translocation of threatened or vulnerable species is a tool increasingly used for conservation and management. However, in some species, homing and movement behaviors may undermine the success of translocation efforts. For the federally protected Agassiz's desert tortoise (Gopherus agassizii), translocation is a strategy used to manage declining populations, yet homing behavior in this species is poorly understood. To explore homing behavior and movement patterns after translocation, we radio tracked 80 tortoises during a 2‐phase experimental translocation. Phase 1 included 40 tortoises that were translocated, then monitored for a period of 37 days (21 Sep–28 Oct 2009), and phase 2 included a different group of 40 tortoises that were translocated and then monitored for 186 days (13 Apr–20 Oct 2010). In both phases, we assigned tortoises randomly to 1 of 3 treatment groups: translocated (displaced 2, 5, or 8 km from their source location), handling control, or control. After translocation, 20% of the translocated tortoises were able to navigate to their source location, and translocation distance had an effect on their ability to navigate home. We found 44% of tortoises in the 2‐km translocated group returned home; 1 tortoise in the 5‐km group, and no tortoises in the 8‐km translocated group returned. The time required to reach home ranged from 5 to 37 days for the 2‐km group, and 34 days for the 5‐km group. We deemed tortoises to have homed successfully if they returned to their source location within 37 days of translocation as this reflected the duration of phase 1 and allowed for a balanced comparison between the 2 phases. We found that translocated tortoises moved at least 1.5 times more overall than the control groups, with some individuals moving >10 km from the translocation site. These patterns persisted even after accounting for seasonal and sex differences in distance traveled. By identifying homing behaviors and quantifying post‐translocation movement patterns, this experiment addressed a key data gap in tortoise behavior that may limit the efficacy of tortoise translocation efforts. Our results point to the need to account for behavioral responses of tortoises to minimize risk to translocated individuals and maximize the success of translocation projects. © 2014 The Wildlife Society.

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How far can a tortoise walk in open habitat before overheating? Implications for conservation

Cited by 30 publications

References 45 publications

Landscape pattern is critical for the moderation of thermal extremes

Landscape pattern is critical for the moderation of thermal extremes

Precipitation quantity and timing affect native plant production and growth of a key herbivore, the desert tortoise, in the Mojave Desert

The effects of homing and movement behaviors on translocation: Desert tortoises in the western Mojave Desert

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