Abstract
Thermoregulation is critical for ectotherms as it allows them to maintain their body temperature close to an optimum for ecological performance. Thermoregulation includes a range of behaviors that aim at regulating body temperature within a range centered around the thermal preference. Thermal preference is typically measured in a thermal gradient in fully-hydrated and post-absorptive animals. Short-term effects of the hydric environment on thermal preferences in such set-ups have been rarely quantified in dry-skinned ectotherms, despite accumulating evidence that dehydration might trade-off with behavioral thermoregulation. Using experiments performed under controlled conditions in climatic chambers, we demonstrate that thermal preferences of a ground-dwelling, actively foraging lizard (Zootoca vivipara) are weakly decreased by a daily restriction in free-standing water availability (less than 0.5°C contrast). The influence of air humidity during the day on thermal preferences depends on time of the day and sex of the lizard, and is generally weaker than those of of free-standing water (less than 1°C contrast). This shows that short-term dehydration can influence, albeit weakly, thermal preferences under some circumstances in this species. Environmental humidity conditions are important methodological factors to consider in the analysis of thermal preferences.
Highlights
Thermoregulation is a critical determinant of the ecological performances of many organisms, and of the sensitivity and resilience of biodiversity to global changes [1,2,3]
We ran a qualitative, pilot study with one climatic chamber where 60 lizards were observed to detect any obvious disturbance caused by the contained environment of the climatic chamber. We found in this pilot study that the body temperature (Tb) of lizards ranged from 25 to 35 ̊C during the day and matched qualitatively the values recorded in earlier studies using laboratory thermal gradients or performed in outdoor conditions [47,50,51]
The change in thermal preferences between water availability treatment groups was not a consequence of lizards avoiding the warmest parts of the gradients where the expected evaporation rates would be the highest (Fig 1)
Summary
Thermoregulation is a critical determinant of the ecological performances of many organisms, and of the sensitivity and resilience of biodiversity to global changes [1,2,3]. Thermoregulation largely involves behaviors such as modulations of activity patterns, shifts in the selection of micro-habitats or changes in body posture through which the organism adjusts heat transfer processes to modulate its body temperature [4,5,6]. It has received a support under the program "Investissements d’Avenir" launched by the French government and implemented by ANR with the reference ANR-11-INBS-0001 AnaEE France
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