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 in the future. It's not just about survival—it's about building social bonds that pay off later. Let me give you two examples. First, consider vampire bats. When a bat fails to find blood one night, it might starve. But a well-fed bat will often regurgitate blood to share with a hungry companion. Importantly, the bat that received help is more likely to return the favor later. This mutual back-scratching ensures the colony's survival. Second, think about vervet monkeys. When a monkey gives an alarm call to warn others of a predator, it actually puts itself at risk by drawing attention. However, other monkeys remember who gave reliable warnings. In the future, those reliable callers are more likely to receive grooming or support in fights. So, in both cases, the initial sacrifice creates a debt that is repaid, strengthening cooperation within the group.