TALENHUB14 - Regulación adaptativa del nivel metabóli

Individual metabolic rates change dynamically under various circumstances, and different time scales. Basal metabolic rate (MR) represents the minimal cost of maintenance in endotherms. However, basal MR has been questioned in an ecological context, as individual variation is substantial and poorly understood while selective advantages remain uncertain. I use the wintering passerines as a model system to reveal whether individual variation in basal MR is adaptive and therefore could be considered a trait under selective regulation. Wintering small birds at high latitudes need to cover their energy requirements on a daily basis, at a time when conditions deteriorate and food becomes scarcer. Food acquisition, and ultimately body mass (BM) is considered the main trait birds manage in order to survive winter conditions. However, theoretical and empirical studies suggest that small-birds may not only regulate BM but other traits like basal MR or facultative hypothermia (FH) may also play a relevant role. Studying wild wintering great tits I aim to reveal whether: 1. Patterns of seasonal variation in BM persist when variation due to basal MR is accounted for, implying that seasonal changes in BM may reflect changes in basal MR rather than internal reserves. 2. The level and variation in individual basal MR, BM and FH is related to actual or previous body condition. Basal MR and various measures of body condition will be obtained from wild caught individuals twice in a period of 4 weeks, reflecting the individual condition at 4 time scales ranging from present to previous molting period. 3. Wintering small birds regulate BM, basal MR or FH under a predation-starvation dilemma. All three traits will be measured from captive birds before and after a predation and starvation experiment, to evaluate which traits individuals optimize. With these three experiments I will be able to ascertain whether basal MR plays a role as an adaptive trait in real ecological circumstances.