Foraging Energetics and Risk

维持或管理一个自然系统需要我们了解组成这个系统的有机体的生存策略。我们可以通过预测生存策略将如何随着环境变化而改变的能力来衡量我们的理解水平。许多动物，特别是小鸟和哺乳动物，必须找到并消耗足够的食物来满足他们每天的能量消耗，否则就可能面临通宵饥饿的可能性(当黑暗中断觅食时)。在食物报酬随机变化的环境中，理论预测，这种动物的觅食行为取决于预期的每日能量摄入量与每日能量消耗的比较。鉴于食物奖励的特定平均水平，当预期能量摄入量超过支出(即平均收益超过成本)时，采集者应避免具有高奖励变异性的食物资源。然而，当必要的支出超过预期的能量摄入量(即成本超过平均收益)时，觅食者应该更喜欢高回报变异性。卡拉科博士之前的实验支持了这一理论。在这项工作中，每天的能量消耗基本上是固定的，卡拉科博士通过实验操纵了觅食鸟类的预期每日能量摄入量。但相互竞争的理论预测了这些实验中的类似行为。卡拉科博士的新研究涉及不同理论预测不同行为的研究。他将保持预期的每日能量摄入量不变，并通过实验控制每日的能量消耗。使用步入式冷却器，他可以选择环境温度，在这种环境温度下，一只(“温血”)鸟的食物摄入量超过、等于或低于它的需要。他预计，鸟类对食物奖励可变性的厌恶或偏好，仍将取决于预期能量摄入量与消耗的比较。如果卡拉科博士的实验结果与他的预测相符，这将表明，他的理论将显著提高我们对促进在不同环境中生存的行为策略的理解水平。

Maintaining or managing a natural system requires that we understand the survival strategies of the organisms that make up the system. We can gauge our level of understanding by our ability to predict how survival strategies will change as the environment changes. Many animals, especially small birds and mammals, must find and consume enough food to meet their energy expenditures each day, or face the possibility of starving overnight (when darkness interrupts foraging). In an environment where food rewards vary randomly, theory predicts that the foraging behavior of such animals depends on a comparison of expected daily energy intake with daily energy expenditures. Given a particular average level of food rewards, foragers should avoid food resources with high reward variability when expected energy intake exceeds expenditures (i.e., average benefits exceed costs). However, foragers should prefer high reward variability when necessary expenditures exceed expected energy intake (i.e., costs exceed average benefits). Dr. Caraco's previous experiments supported the theory. In that work, daily energy expenditures were essentially fixed, and Dr. Caraco experimentally manipulated the expected daily energy intake of foraging birds. But competing theories predict similar behavior in these experiments. Dr. Caraco's new research involves studies for which the different theories predict different behaviors. He will hold expected daily energy intake constant and experimentally manipulate daily energy expenditures. Using walk-in coolers, he can select ambient temperatures where a ("warm-blooded") bird's food intake exceeds, equals, and falls short of its requirement. He anticipates that the bird's aversion to, or preference for, food-reward variability will still depend on a comparison of expected energy intake with expenditure. If Dr. Caraco's experimental results match his predictions, it would indicate that his theory provides a marked increase in our level of understanding of the behavioral strategies that promote survival in variable environments.