Practice question

Optimal diet theory ranks prey by profitability, usually E_i/h_i, where E_i is usable energy from prey type i and h_i is handling time. Prey type P1 ranks above P2 when E1/th1 exceeds E2/th2, because each unit of post-encounter time devoted to P1 yields more energy. The ratio, not the sum or product of energy and handling time, captures energetic return rate. A predator encountering the higher-ranked type should accept it under the basic model. Whether it also accepts the lower-ranked type depends mainly on the encounter rate with higher-ranked prey: abundant P1 can make rejecting P2 worthwhile, whereas rare P1 raises search costs and favors a broader diet. Abundance of P2 itself does not directly determine acceptance after encounter in the classic contingency model. Real choices can incorporate nutrients, capture probability, toxins, and risk, but these can be represented by adjusting expected gain or effective handling cost. The inequality therefore states a ranking rule rather than a complete prediction of diet composition.