Paper by David Rozen-Rechels made the cover of Ecological Monographs!

With ongoing global change, landscape structure changes are expected to be a driver of extinction rates of temperate zone ectotherms. In a recent study led by David Rozen‐Rechels (doi: 10.1002/ecm.1440) we found that changes in water availability, coupled with rising temperatures, might have a drastic impact on the population dynamics of some ectotherm species. This paper made the cover of the journal issue, Ecological Monographs. The selected photograph is an aerial view of the habitat for the studied population of the common lizard Zootoca vivipara (referenced as TIO in the study) at Mont d’Aubrac Massif in the mountain ranges of Massif Central in south‐central France, where grass, heather, and rocks provide a diversity of thermal micro‐habitats. Image taken with a Phantom 4 Pro drone (DJI, Shenzen, China) in July 2017 by J.-F. Le Galliard

Social costs and visual communication in lizards

According to animal signalling theory, social costs incurred by aggressive conspecifics are one mechanism maintaining signal honesty. Although our understanding of signal evolution has much improved for pigment-based colours, the mechanisms maintaining the honesty of structural colour signals, such as ultraviolet (UV), remain elusive. In a recent study led by master student Anna Kawamoto and post-doctoral collaborator Arnaud Badiane, we used the common lizard (Zootoca vivipara) to test whether the honesty of UV-reflecting signals displayed on male throats is under social control. To do so, we staged agonistic interactions between non-manipulated focal males and opponents of either larger or smaller body size. We manipulated the UV component of the male throat colour patch to create small cheaters with UV-enhanced throats, large cheaters with UV-reduced throats, and their respective controls. In support of a conventional signal hypothesis, focal males were aggressive towards large cheaters and became submissive when these large cheaters retaliated, and were less submissive against small cheaters. However, that focal males were not more aggressive towards small cheaters contradicts our initial predictions. We confirm that male UV reflectance and bite force were good predictors of contest outcomes in control conditions. Overall, we provide partial evidence suggesting that social costs enforce UV signal honesty in common lizards.

Anna Kawamoto, Jean-François Le Galliard, Arnaud Badiane, The role of social costs as a mechanism enforcing the honesty of ultraviolet-reflecting signals in a lizard, Biological Journal of the Linnean Society, 2021,

Effects of air humidity and water availability on thermal preferences of a lizard

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.

Female common lizard basking in the field (Audrey Ely, 2020)