# Scaling of the risk landscape drives optimal life history strategies and the evolution of grazing

## TL;DR

This paper develops a theoretical model to understand how the variability and distribution of resources influence life-history strategies and the evolution of grazing behaviors, highlighting risks like Allee effects and implications for large herbivores.

## Contribution

It introduces a framework linking resource landscape variability with optimal life-history strategies and the evolution of grazing, emphasizing the role of resource clustering and body size.

## Key findings

- Depleted environments favor earlier reproduction and larger reproductive investments.
- Resource clustering increases extinction risk due to Allee effects.
- The model explains the evolution of large-bodied grazers from smaller browsing ancestors.

## Abstract

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.