Diet breadth is a classic optimal foraging theory (OFT) model from human behavioral ecology (HBE). Different resources, ranked according to their food value and processing costs, are distributed in the environment in different densities. One or more foragers searches for resources and decides to take them according to rank. A forager will preferentially take highest ranked resources (providing the highest net return). Within increasing dietary stress a forager will be willing to take a wider variety of resources at different ranks.