Fat fish stay cool: Stress recovery and behavioral flexibility vary with nutritional state and predator exposure in the cichlid Neolamprologus pulcher

Behavioral flexibility plays an important role in adaptation to changing environments within an individuals lifetime. Stress resilience influences flexibility, as short-term stress can enhance attention and memory, while prolonged stress may impair cognitive function. Nutritional state also plays a role, with overweight individuals often suffering greater consequences of chronic stress. The allostatic load model predicts that individuals under prolonged stress remain in a chronically activated state, potentially reducing flexibility. Using a cichlid, we manipulated body condition and exposed individuals to occasional or frequent predator presentations. We then assessed stress responses and behavioral flexibility via a reversal learning test. Contrary to predictions, fish in a high nutritional state - but not overweight - that were frequently exposed to predators recovered rapidly from stress and exhibited enhanced flexibility. Our results provide direct evidence that nutritional state interacts with behavioral flexibility, revealing the costs of coping with repeated stressors. We highlight a link between brief stress responses, characterized by rapid cortisol recovery, and behavioral flexibility. This association only emerged in well-nourished individuals facing frequent stressors, suggesting energy reserves buffer the costs of repeated stress. Thus, resilience benefits behavioral flexibility, while it is energetically costly, as a reduced diet hindered adaptation to environmental change.