  Consumers face numerous risks that can be minimized by incorporating
different life-history strategies. How much and when a consumer adds to its
energetic reserves or invests in reproduction are key behavioral and
physiological adaptations that structure much of how organisms interact. Here
we develop a theoretical framework that explicitly accounts for stochastic
fluctuations of an individual consumer's energetic reserves while foraging and
reproducing on a landscape with resources that range from uniformly distributed
to highly clustered. First, we show that optimal life-history strategies vary
in response to changes in the mean productivity of the resource landscape,
where depleted environments promote reproduction at lower energetic states,
greater investment in each reproduction event, and smaller litter sizes. We
then show that if resource variance scales with body size due to landscape
clustering, consumers that forage for clustered foods are susceptible to strong
Allee effects, increasing extinction risk. Finally, we show that the proposed
relationship between consumer body size, resource clustering, and Allee
effect-induced population instability offers key ecological insights into the
evolution of large-bodied grazing herbivores from small-bodied browsing
ancestors.
