托福听力

🎧 听力原文

Listen to part of a lecture in a biology class. The professor is discussing the behavior of certain bird species. Professor: So, we've been talking about animal behavior, and today I want to focus on a fascinating example of cooperative breeding in birds, specifically the acorn woodpecker. These birds live in family groups, and they store acorns in what we call granaries, which are essentially large structures, often dead trees, where they drill holes and stash acorns. Now, the interesting part is that not all members of the group breed. In fact, only a few dominant individuals reproduce, while the others help with raising the chicks and defending the territory. This seems counterintuitive from an evolutionary perspective, because why would an individual forgo its own reproduction to help others? Well, one key benefit is that these helpers are usually related to the breeding pair, so they pass on their genes indirectly by helping their relatives survive. Additionally, the group benefits from having more eyes to watch for predators and more individuals to maintain the granary. The acorns stored are a critical food source for the winter, and a larger group means better protection of that food supply. So, in this case, the costs of not breeding are outweighed by the benefits of group living and kinship.