The mortality exponent, z, is the key parameter; u* = 2R if z = 2, but u* = 4R/3 if z = 4. In contrast to our previous results, here the optimal foraging effort decreases when mortality is a more sharply accelerating function of foraging effort (fig. 9.5). If the requirement, R, is large, foraging at the maximum rate (u* = 1) may be the best option available to foragers. Notice also that the optimal effort does not depend on the constant, k, but only on the exponent z. This means that the shape of the trade-off is the key, while the exact level of danger is irrelevant. Animals in environments with different absolute levels of danger would have the same optimal behavior as long as their trade-offs between foraging and mortality followed the same basic function.

0 0.2 0.4 0.6 O.fi Required energy expenditure, R

Figure 9.5. For growing animals, optimal foraging effort increases with the amount of energy required to stay alive, R, and decreases as the mortality function becomes more sharply accelerating.

0 0.2 0.4 0.6 O.fi Required energy expenditure, R

Figure 9.5. For growing animals, optimal foraging effort increases with the amount of energy required to stay alive, R, and decreases as the mortality function becomes more sharply accelerating.

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