托福口语 Task 4

Today, we're going to talk about a fascinating behavior in the animal kingdom called 'reciprocal altruism.' This is when animals help others without immediate benefit, expecting that the favor will be returned later. One classic example is seen in vampire bats. These bats need to eat blood every night, but sometimes a young or unlucky bat fails to find food. In such cases, a well-fed bat will regurgitate blood to feed the hungry one. This isn't pure charity—the bat that gives blood is more likely to receive blood from that same bat on a future night when it's hungry. This mutual exchange increases the chances of survival for both. Another example comes from a type of fish called the cleaner wrasse. These small fish set up 'cleaning stations' on coral reefs, where larger fish come to have parasites removed. The cleaner wrasse gets a meal, and the larger fish gets rid of harmful pests. Interestingly, studies show that a cleaner wrasse is more attentive and provides better service to a larger fish that it has seen being patient with other cleaners. This suggests that the cleaner wrasse builds a reputation and expects future cooperation, rather than just a one-time meal. So, in both cases, the initial act of helping is not entirely selfless—it's a strategic investment in future returns.