{"id":705,"date":"2020-11-15T22:11:48","date_gmt":"2020-11-15T21:11:48","guid":{"rendered":"https:\/\/lizardecology.org\/?p=705"},"modified":"2021-02-26T13:44:02","modified_gmt":"2021-02-26T12:44:02","slug":"what-determines-geographic-variation-in-thermoregulation-behavior","status":"publish","type":"post","link":"https:\/\/lizardecology.org\/?p=705","title":{"rendered":"Thermal and hydric conditions drive geographic variation in thermoregulation behavior in a lizard"},"content":{"rendered":"\n

Animals, and especially ectotherms, rely on behavioral thermoregulation to control their body temperature and perform optimally in their natural environment. It is therefore not surprising that research on these animals has focused on understanding the mechanisms and efficiency of thermoregulation behavior, especially in the context of global warming. Whereas most field studies are interested in behavioral responses of ectotherms to changes in their thermal environment, including mean thermal quality and occurrence of heat stress events, laboratory and experimental studies have shown that thermoregulation behavior is sensitive to a myriad of other abiotic factors, such as food and water, and biotic interactions, such as competition. So one key question is how much each factor contributes to explain natural variation in thermoregulation behavior and its efficiency given that natural populations are exposed to multi-factorial changes in the quality and the structure of the thermal landscape, in the water availability, etc. This question is difficult to tackle by paired comparisons of a small number of sites or by classical gradient studies.<\/p>\n\n\n\n

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A male common lizard photographed by Arnaud Badiane and basking full sun on a rock<\/em><\/figcaption><\/figure>\n\n\n\n

To answer these questions, David Rozen-Rechels<\/a>, a PhD student in our laboratory now post-doctoral researcher in the Max Planck Institute for Animal Behavior research group in Germany, performed one of the most exhaustive comparative study of thermoregulation behavior in the common lizard (Zootoca vivipara<\/em>), a widespread species occurring in bogs, heather lands, meadows and forest clearances in cold and humid environments in France. Together with the group of Jean Clobert, especially post-doctoral and PhD students Andr\u00e9az Dupou\u00e9, Alexis Rutschmann, Pauline Blaimont<\/a> and Arnaud Badiane<\/a>, and with the help of Prof. Donald Miles<\/a>, we sampled as many as 21 populations in Massif Central, France between 2016 and 2018. These populations are part of a long-term field study of geographic variation in reproductive strategies of female lizards. This sampling scheme allows us to test for effects of geographic variation caused by altitude, climate conditions or habitat because populations are scattered across a complex “gradient” of altitude, slope orientation and forest cover. The decision to sample populations during three successive years was a strength of this study. It allows us to make inference about effects of consistent differences among populations versus peculiar conditions observed only during one year due to weather fluctuations.<\/p>\n\n\n\n

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One population located in a meadow at Pejouzou nearby Puy Mary (Cantal). Photograph by J.-F. Le Galliard.<\/em><\/figcaption><\/figure>\n\n\n\n

In each population, we measured the body temperature of lizards in the field and their location. We also sampled the thermal quality of the environment with physical models coupled with thermal data loggers. Some lizards were transported back to the laboratory to measure their thermal preferences in a gradient, a measure of their “ideal” body temperature without constraints and stress. Not to say this was a herculean work and around 2,000 lizards were gently processed during this research program. Together with Micha\u00ebl Guillon, an independent researcher working part time for Biotope – an ecology expert office, we extracted detailed weather data to characterize historical conditions and annual conditions in each population.<\/p>\n\n\n\n

But this was not enough … During the first field season in 2016, we decided to quantify micro-habitat structure and heterogeneity in each population. Indeed, one recent finding of thermoregulation research is that animals should thermoregulate better in more heterogeneous thermal environments, when a combination of shady and open micro-habitats allows them to heat or cool depending on their requirements. The habitats of the common lizard are extremely heterogeneous and we tried first to sample this diversity with detailed photographs taken close to the ground. But this took too much time and was difficult to process.<\/p>\n\n\n\n