Note that the optimal prey

Note that the optimal prey - th prey type where V j/H j<...

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Note that the optimal prey-choice model defines a central trade-off : 1) If specialize in highest-ranked (most efficiently harvested) prey type, face highest possible search costs per unit harvested (spend the most time passing up "unacceptable" prey types, waiting to encounter the top-ranked type) 2) If take all or most prey types, will have to harvest many low-ranked ones (i.e., ones with the lowest return per unit handling time) Since both higher search time and handling time occur in the denominator of overall return rate (see 5) above), this tradeoff seems to create "damned if do, damned if don't" dilemma, but in fact defines optimal diet breadth as point where marginal decline in search cost = marginal increase in handling costs Thus, model reveals a very simple decision rule for optimal solution: add prey types to the set taken, in descending rank order, until reach the j
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Unformatted text preview: th prey type where V j /H j < Σ V i / (T s + Σ H i ) [Note: V = value (e.g., calories) for each prey type; T s = total search time; Σ = "sum of"; H = average handling time for prey items of each prey type] Phrased in English, this rule says "Add prey types until the post-encounter return rate from a prey type is lower than the average rate of return for all higher-ranked prey types (including search time)" The optimal diet thus occurs at the point that "adding" prey types to diet, in descending rank order (most efficient to least) leads to a decrease in the overall rate of return [see Kelly 1995:85-86 for an example] Although optimal prey-choice model seems pretty formalized and abstract, the major elements actually correspond quite closely to concrete aspects of the foraging process, and its procedures are pretty straight-forward...
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