Risk-sensitive foraging in a tropical lizard.

Foraging opportunities can be unpredictable. When foragers face a choice between resources that vary in predictability, foraging decisions not only depend on the profitability of food but also on their physiological state. This risk-sensitive foraging approach, in which animals take greater foraging risks when starving, remains relatively untested in reptiles compared with other taxa. We tested the risk-sensitive foraging theory in the tropical lizard, Psammophilus dorsalis, by manipulating energy budgets (satiated versus 48 h starved) and measuring foraging preferences for options that differed in rewards: constant (two mealworms) versus variable (zero or four mealworms). We found that satiated lizards were risk averse to variability in reward amounts and chose the constant food option more frequently than the variable option. In contrast, starved lizards were risk-prone and chose the variable reward option more often than the constant one. At the end of foraging trials, these strategies resulted in both starved and satiated groups achieving similar net resource gains. As new support for risk-sensitive foraging in a tropical reptile species, these results provide insight into how resource uncertainty influences foraging strategies. For lizards in the tropics, which have high-energy requirements year-round, risk-sensitive foraging could be an effective strategy in stochastic environments.