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, Bothrops alternatus. Maximum oxygen consumption rates () during digestion increased with temperature, while the time to reach these rates (Tpeak) and the duration of the digestive process decreased as temperature was elevated. Both, scope () 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 accompanied by an increase in digestion duration. Thermal regime did not affect the energetic cost of digestion in B. alternatus.