Evidence from recent studies on foraging behavior supports the idea that animals optimize for multiple macronutrients and not just energy gain. Such optimization requires animals to know three things – 1) their current nutritional state, 2) nutritional composition of the food item, and 3) how much of the food item is needed to achieve the desired nutritional state. Lab experiments on animals across taxa demonstrate that they can, in fact, achieve this feat. We now also know that optimal nutritional composition of diets, or ‘intake targets’, are plastic, which allows animals to maintain homeostasis under changing environmental conditions. Abiotic factors (such as temperature) and trophic interactions (both bottom-up and top-down) not only affect the nutritional demands, but also constrain acquisition of nutrients in response to those demands. In addition, life-history strategies such as foraging modes might also influence nutritional demands, and therefore, intake targets. Under natural conditions, however, such constraints often prevent animals from achieving these targets.

In many habitats, available resources vary temporally with seasons and spatially across the landscape. Along with these bottom-up constraints on nutritional intake, top-down predation risk effects also affect foraging behavior and nutrient acquisition in the prey species. In a desert ecosystem such as the one in the Thar, an herbivorous agamid, the Indian spiny-tailed lizard Saara hardwickii, experiences great spatio-temporal variation in resource nutritional quality. Temporal variation in temperature and spatial variation in predation risk are also prominent stressors and can influence foraging in these lizards. This provides an opportunity to understand nutritionally explicit foraging decisions in response to environmental factors varying in both space and time. In my thesis, I propose to examine the nutritional intakes of S. hardwickii in response to temporal shifts in nutrient state space and temperature. I will also capture the variation in distribution of nutrients in space to construct a ‘landscape of nutrition’ (LON) for the spiny-tailed lizards. Lizard burrow densities and body condition index will be measured to understand burrow site selection and its consequences along the landscape of nutrition. In addition, I will quantify predation risk to construct a ‘landscape of fear’ (LOF) in the same space. Along the LON and LOF, I will examine various behavioral, nutritional, and physiological variables to understand animal responses as they balance foraging benefits and predation risk. Further, in a manipulative experiment, I will examine the consequences of long-term nutritional constraints on physiological and motor performance. Finally, using published literature on diet composition, I will explore how life-history strategies such as foraging modes shape intake targets over evolutionary timescales in animals across taxa.