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 without immediate benefit, expecting that the favor will be returned later. One classic example comes from vampire bats. These bats need to feed on blood every night, but sometimes a bat fails to find food. In such cases, a well-fed bat will regurgitate blood to share with the hungry bat. The key is that the bat that received help often returns the favor on a future night when the helper is hungry. This exchange only works because the bats have long-term memories and recognize each other, so they can trust that the favor will be repaid. Another example is seen in certain fish species, like the cleaner wrasse. These small fish set up 'cleaning stations' where larger fish come to have parasites removed. The cleaner fish gets a meal, and the larger fish gets cleaned. Interestingly, the larger fish could easily eat the cleaner, but they don't. They spare the cleaner because they value the service, and the cleaner benefits from the ongoing relationship. So, reciprocal altruism is not just about one-time help, but about building a system of mutual reliance that benefits both parties over time.