The thermoregulatory strategy of reptiles should be optimal if ecological costs (predation risk and time devoted to thermoregulation) are minimized while physiological benefits (performance efficiency and energy gain) are maximized. However, depending on the exact shape of the cost and benefit curves, different thermoregulatory optima may exist, even between sympatric species. We studied thermoregulation in two coexisting colubrid snakes, the European whipsnake (Hierophis viridiflavus, Lacépède 1789) and the Aesculapian snake (Zamenis longissimus, Laurenti 1768) that diverge markedly in their exposure, but otherwise share major ecological and morphological traits. The exposed species (H. viridiflavus) selected higher body temperatures (approximately 30 degrees C) than the secretive species (Z. longissimus, approximately 25 degrees C) both in a laboratory thermal gradient and in the field. Moreover, this difference in body temperature was maintained under thermophilic physiological states such as digestion and molting. Physiological and locomotory performances were optimized at higher temperatures in H. viridiflavus compared to Z. longissimus, as predicted by the thermal coadaptation hypothesis. Metabolic and energetic measurements indicated that energy requirements are at least twice higher in H. viridiflavus than in Z. longissimus. The contrasted sets of coadapted traits between H. viridiflavus and Z. longissimus appear to be adaptive correlates of their exposure strategies.

Understanding variations in individual trajectories is a crucial evolutionary issue. Terrestrial ectotherms from temperate regions typically face thermal constraints and limited activity periods. Developmental conditions (i.e. embryonic life) and reproductive timing (laying date) should induce phenotypic variations and influence subsequent ontogenetic trajectories (growth and survival). We studied these combined influences in an oviparous squamate, the wall lizard (Podarcis muralis), comprising a multiple clutch species with natural variations in laying date for the first clutch. We experimentally manipulated maternal basking opportunities during gravidity (3, 6 or 9 h per day) and incubation temperature (23 or 29°C). Early laying date positively influenced winter survival in both incubation treatments. Survival was significantly lower in cool than warm-incubated individuals (14.8% and 73.6%, respectively) because of delayed hatching date and reduced activity period before winter. Individuals from cool incubation temperature were slightly smaller but had a higher body condition and grew faster during the first month of life. Offspring behaviour was driven by complex interactions between gravidity and incubation treatments. Under cool incubation temperature, defensive behaviour was high, independently of gravidity treatment. Warm incubated individuals showed low defensive response except when maternal basking opportunities were restricted to 3 h. Defensive behaviour at birth had a positive influence on survival in cool-incubated individuals. The results of the present study highlight the long-term influence of hatching date that integrates female reproductive timing and incubation conditions.