Does diet influence physiological and behavioural responses to predation risk?

Abstract

As one of the strongest selective forces, predation risk induces antipredator responses in prey that not only maximise survival probability but are energetically expensive. While these responses are known to affect foraging patterns and diet composition, the functional role of changes in dietary macronutrients remains unclear. We investigated the effect of dietary NPE (non-protein energy) concentration on the antipredator responses of the Indian rock agama Psammophilus dorsalis. In a manipulative experiment, wild-caught lizards were fed either a low or high NPE diet and exposed to repeated simulated predator attacks. We measured the space-use and hiding duration of lizards after each attack, as well as their circulating corticosterone concentrations at the end of the experiment. Predator exposure induced refuge use for all lizards. Diet had a context-dependent effect: lizards on the high NPE diet used riskier perch locations more frequently than those on low NPE diets, but only during safe periods and not during active threat. Physiologically, lizards on the low NPE diet had significantly higher baseline corticosterone levels, indicating a greater allostatic load. Overall, while dietary NPE did not alter reactive escape behaviour, it influenced the underlying physiological state and proactive behavioural decisions.