Behavioral Ecolo10 - As we can see in the , the rate of...

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Behavioral Ecology Marginal Value Theory Marginal value theory, also called patch choice theory, is a form of the economic law of diminishing returns . An animal feeding at a food patch must decide when to leave the patch in search of another. The more of the patch the animal consumes, the lower the rate of return will be for the remainder of the patch because the food supply is running out. Using calculus, we can determine the optimal time for the animal to leave the patch and search for a new one. When the profitability of the patch lowers enough to equal the profitability of an average patch, including the time it will take to search or travel to the new patch, the animal should leave. Mathematically, the optimal time to leave is: dE(h)/dh = E(h)/(s+h). You should be aware this formula exists, but need not know how to use it. There is a simpler, graphical method for determining the optimal time to spend at any one patch. Figure %: Diminishing rates of return at a food patch
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Unformatted text preview: As we can see in the , the rate of calorie consumption decreases as the animal spends more time at one patch (the slope of the graph decreases). The total calories continues to increase, but the animal would benefit more by finding a fresh patch from which the rate of consumption would be higher. The easier to use graphical method is illustrated in . If we know how long it will take on average to find a new patch, we draw a line from that search time so that it is tangent to the curve. The point at which our line touches the curve is the optimal time to spend at the patch. After this time, the animal should leave. Figure %: The optimal time to spend at a patch The marginal value theory predicts that animals will remain in one patch longer when patches are scarce or far apart. Like the contingency model, the patch choice model is not perfect; it merely serves to approximate the amount of time an animal will spend in any one patch....
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