Preference in patchy landscapes: the influence of scale-specific intake rates and variance in reward

Abstract

Understanding the responses of foragers to patchy distributions of resources has formed a fundamental challenge in behavioral ecology. Two currencies have been used to assess the patch preferences of herbivores—intake rate maximization and risk sensitivity. We wished to understand if small mammalian foragers, collared lemmings (Dichrostonyx groenlandicus), choose patches to maximize food intake rate or to reduce risk of starvation in “variable” environments. Moreover, we examined the possibility that maximizing intake rate depends on the spatial scale of patchiness. We designed an experiment offering two alternative patches of food, varying the predictability of food rewards and the “potential intake rate” at different spatial scales. Collared lemmings did not consistently select patches that maximized their intake rate at either scale studied. Instead, they chose patches offering the least variation in food reward over the course of the experiment. Collared lemmings used prior knowledge gained from previous foraging bouts to assess food variability. We interpret these results as evidence for risk-averse foraging strategies, which are predicted for continuous foragers aiming to minimize risk of starvation.