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 birds. Professor: Today, we're going to talk about a fascinating behavior observed in some species of crows, specifically the American crow. This behavior is called 'anting.' Now, anting is when a bird deliberately rubs ants on its feathers. Some birds even allow ants to crawl through their plumage. Why would they do this? Well, researchers have proposed several hypotheses. One idea is that the ants' formic acid acts as a natural insecticide, killing or repelling parasites like lice and mites. Another hypothesis suggests that the ants help to soothe the bird's skin during molting, when new feathers are growing in. Interestingly, some birds also engage in a similar behavior with other items, such as citrus fruits or even burning cigarettes, which contain strong chemicals. This suggests that the birds are not just after the ants themselves, but rather the chemical compounds. However, a recent study found that the frequency of anting increases when the weather is hot and humid, which might point to a thermoregulatory function, but this is still debated. So, as you can see, the exact purpose of anting remains a bit of a puzzle, and it likely serves multiple functions depending on the context.