Аудирование TOEFL

🎧 Транскрипт аудио

Listen to part of a lecture in a biology class. The professor is discussing the behavior of certain birds. 'Today, we're going to talk about a fascinating behavior known as 'anting,' which is observed in some bird species. Anting involves birds deliberately placing ants on their feathers or allowing ants to crawl over their bodies. There are two main forms: active anting, where the bird picks up ants and rubs them on its feathers, and passive anting, where the bird lies on an ant nest and lets the ants swarm over it. Why do birds do this? One hypothesis is that ants secrete formic acid, which acts as a natural insecticide, helping to eliminate parasites like mites and lice. Another idea is that the ants' secretions soothe irritated skin during molting. Some researchers also suggest that anting might be a way to acquire chemical defenses, making the birds less palatable to predators. However, not all birds engage in anting, and its frequency varies among species, which puzzles scientists. Recent studies have shown that birds may prefer ants that produce more formic acid, supporting the parasite-control theory, but the behavior remains not fully understood.'