Foraging is essential for animals, providing energy for all fitness-related activities. While foraging decisions are often viewed as maximizing intake and minimizing costs, this food-centric view overlooks the role of specific nutrients. In the wild, animals face various environmental challenges that trigger physiological responses, such as glucocorticoid-driven metabolic shifts altering nutritional demands and should therefore directly influence dietary choices. Hence, foraging decisions should be readily explicable at the nutrient levels. In my thesis, I examined how environmental risks, such as resource uncertainty, seasonal changes, and predation risk affects foraging behaviour and nutritional intakes in the tropical lizard, Psammophilus dorsalis, highlighting strategies employed to meet changing nutritional needs.

Reptiles exhibit physiological adaptations for torpor, helping them combat energetic shortages in the wild. Hence, we first tested whether tropical lizards adjust foraging choices in response to resource uncertainty risk by manipulating their starvation levels. We found that satiated lizards avoided risk while starved lizards took greater risks, providing novel evidence of risk-sensitive foraging in a tropical reptile. We then explored how seasonal variation in glucocorticoids is linked to life-history stages of lizards and affect their dietary nutritional intakes and excretion in the wild. We found that, despite seasonal variation in stress-induced glucocorticoids, lizards maintained a consistent carbon:nitrogen intake ratio. However, glucocorticoids negatively correlated with faecal compositions, suggesting post-ingestive nutritional retention as a possible strategy to meet physiological demands.
Expanding on our findings from previous chapters, we explored post-ingestive elemental retention in response to physiological stress as an adaptive strategy to meet energetic demands during challenging states. In a lab experiment, we manipulated stress levels and measured carbon and nitrogen retention. Lizards selectively reduced nitrogen retention efficiency alone when compared to their wild diets highlighting the need to study compensatory strategies that animals employ to achieve their nutrient goals. In my final chapter, we explored how predation risk affects prey dietary choices by testing two hypothesis – the food safety trade-off and nutritional optimization. By manipulating ‘what to eat’ and ‘where to eat’, we studied dietary choices and measured macronutrient intakes by lizards. Results revealed novel support for both hypotheses in governing dietary choices of lizards when faced with predation risk, offering new insights into how fear shapes nutritional decisions of prey.
Overall, my thesis shows how animals integrate environmental cues with physiological needs to guide foraging decisions and optimize nutrient intakes under diverse ecological challenges.