托福口语 Task 4

Today, we're going to talk about a fascinating concept in animal behavior called 'reciprocal altruism.' This is when animals help others who are not their relatives, with the expectation that the favor will be returned in the future. It's a form of cooperation that can seem puzzling from an evolutionary perspective, since it might appear to benefit the recipient more than the giver. But reciprocal altruism can be advantageous if the animals have long-term relationships and can remember past interactions. Let me give you two clear examples. First, consider vampire bats. In a colony, a bat that has successfully fed will sometimes regurgitate blood to share with a hungry bat that failed to find food. The key is that the bat that received help is more likely to return the favor later when the original giver is hungry. This works because bats live in stable groups for years, so they can track who has helped them. Second, think about cleaner fish, like the cleaner wrasse. These small fish set up 'cleaning stations' on coral reefs where larger fish come to have parasites removed. The cleaner fish gets a meal, and the larger fish gets cleaned. Interestingly, if a larger fish is a regular customer, the cleaner fish will treat it more gently, while it might give a quick, less thorough clean to a newcomer. The regulars remember the good service and return, and they also chase away predators of the cleaner fish. So, in both cases, the mutual benefit relies on repeated interactions and memory.