托福口语 Task 4

Today, we're going to talk about a fascinating concept in behavioral ecology called 'optimal foraging.' This theory suggests that animals make decisions to maximize the energy they gain from food while minimizing the energy they spend to get it. Essentially, animals choose food sources that give the best net benefit. Let me give you two examples to illustrate this. First, consider a species of shorebirds that feed on crabs. When crabs are small, they're easy to catch but provide little energy. Large crabs, on the other hand, are harder to catch—they can pinch and escape—but they provide a lot of energy. The birds don't always go for the largest crabs; instead, they select medium-sized ones. Why? Because the energy gained from a large crab doesn't justify the extra time and risk spent catching it. Medium crabs give the best balance. Second, think of bees foraging on flowers. Some flowers have abundant nectar but are located far from the hive. Others have less nectar but are nearby. Bees often choose flowers closer to the hive, even if they have less nectar, because the energy saved in flight outweighs the lower nectar yield. So, in both cases, animals are making cost-benefit decisions.