Internal states drive nutrient homeostasis by modulating exploration-exploitation trade-off

Internal states can deeply alter the behavior of animals. Which aspects of behavior change upon metabolic challenges and how these allow the animal to achieve nutrient homeostasis is poorly understood. We used an automated video tracking setup to characterize how amino acid and reproductive states interact to shape exploitation and exploration decisions taken by adult Drosophila melanogaster, to achieve nutritional homeostasis. We find that these two states have specific effects on the decisions to engage and leave proteinaceous food patches. Furthermore, the internal nutrient state defines the exploration-exploitation trade-off: nutrient deprived flies focus on specific patches while satiated flies explore more globally. Finally, we show that olfaction mediates the efficient recognition of yeast as an appropriate protein source and that octopamine is specifically required to mediate homeostatic postmating responses without affecting internal nutrient sensing. Internal states therefore modulate specific aspects of exploitation and exploration to change nutrient selection.