Climate change will continue to increase mean global temperatures with daily minima increasing more than daily maxima temperatures. Altered rainfall patterns due to climate change will also disrupt water availability for terrestrial organisms already facing climatic warming. To explore how organisms may adjust to changes in multiple, concurrent climate‐related environmental conditions, we manipulated day and night temperatures as well as water availability during gestation in female common lizards Zootoca vivipara, a cold and wet adapted species facing climatic changes notably in populations located on the warm margin. We jointly manipulated temperature (hot or cold) independently during the daytime and nighttime as well as water availability (± ad libitum access to water) throughout pregnancy and quantified the effects on maternal traits (morphology, physiology and phenology) and reproductive output. Overall, we found that higher day or night temperatures decreased gestation length and increased energetic demands. Higher temperatures during the day, coupled with water restrictions, increased dehydration and water restrictions affected ability to allocate resources but had no impact on reproductive output. While high temperatures during the day were beneficial to current reproductive output and success, high temperatures during the night had the opposite effect. Our results suggest that high nighttime temperatures can dramatically increase the burden on pregnant mothers already constrained by heavy resource and water investment. This could provide a mechanistic explanation for the long‐term declines of warm‐margin populations in this species.

The postprandial increment of metabolism, often referred to as specific dynamic action (SDA), encompasses the summed costs of meal ingestion, digestion, absorption, and assimilation. Different SDA parameters, such as its magnitude, duration, and relative cost, are affected by a diverse set of environmental and physiological determinants, including meal size and body temperature. While the influence of these variables has been thoroughly examined in most ectothermic vertebrate groups, few studies have focused on the determinants and consequences of the SDA response in anuran amphibians. Thus, we examined the effects of meal size and body temperature on the SDA response of a Neotropical frog, Leptodactylus latrans, by measuring the rates of oxygen consumption of frogs while fasting and after being fed meals of different sizes at different temperatures. SDA lasted from 3 to 5 days and increased with meal size for frogs fed meals equivalent to 5-15% of their body mass. SDA cost was not affected by meal size and averaged 14.6% of the caloric content of the meal. Temperature increment was accompanied by proportional increases in metabolic rateand shorter SDA duration. The relative SDA cost averaged 14.8% of the meal caloric content at 20°C and 25°C, but increased to 23.5% at 30°C. Our results indicate that meal size imposes no physiological or energetic constraint to L. latrans feeding.Digestion at temperatures near the thermal preference of the species seems to optimize energetic return, whereas the shortening of SDA duration at higher temperatures may provide significant ecological advantages. K E Y W O R D Sanurans, digestion, energetics, meal size, postprandial metabolic increment, temperature

bstract. Metabolic studies in ectothermic vertebrates are, almost always, conducted at a constant temperature, a valid and recommended procedure in most instances. However, for long term measurements, for example during snakes digestion, keeping experimental temperature constant subjects the animals to a condition potentially quite diverse from what animals may experience in nature. Thus, we investigated the influence of constant (20°C, 25°C, and 30°C) and fluctuating (circadian thermoperiod cycles of 20:30°C, 12:12 h) temperatures regimes on the post-prandial metabolic response of the Crossed pit viper, Borhrops alternatus. Maximum oxygen consumption rates (V02peak) during digestion increased with temperature, while the time to reach these rates (Tp^ai^) and the duration of the digestive process decreased as temperature was elevated. Both, scope (V02peak/RMR) and SDA coefficient were not influenced by temperature. When compared to the results obtained at constant 25°C (which is equivalent to the average temperature of the fluctuating regime), the fluctuating temperature regime caused a decrease in RMR and V02peak accompanied by an increase in digestion duration. Thermal regime did not affect the energetic cost of digestion in B. alternatus.